The Rosette or Skull Nebula (NGC 2237, Sh2-275) My February target was the fantastic and grand Rosette Nebula, also known as the Skull Nebula for hopefully obvious reasons. This nebula is a gigantic cloud of predominantly ionized atomic hydrogen that lies in the Monoceros constellation, not too far from the Orion Molecular Cloud Complex. This object has a number of different catalogue designations given to different regions of the nebula (NGC 2237, 2238, 2239, 2246) and associated star clusters. The primary star cluster being NGC 2244 – the most central cluster that provides most of the illumination and stellar winds and radiation that illuminate and disperse the gaseous clouds that form the nebula. X-ray imaging has identified approximately 2500 young stars in this star-forming complex.
Space is Big This nebula lies approximately 5,000 light years from earth and is roughly 130 light years in diameter. To get an idea how immense this nebula is, compare this to the Great Orion Nebula (M42), which is only 40 light years in diameter. With all this talk about light years, I wanted to explore this to get a better idea of what we’re talking about and try and wrap our heads around the scale of an object like this. A light year is roughly 5.88 trillion miles – the distance light travels in a year. Since I’m an American, I’ll keep everything in miles so that I can better understand. The diameter of this nebula is roughly 764 trillion miles. The fastest spacecraft ever recorded is the Parker Solar Probe, which reached a top speed of 364,660 mph. This comes to 3,194,421,600 miles this probe can traverse in a single year. Sounds like a lot, right? Well, to cover the 764 trillion miles to reach one end of this nebula to the other, it would take the Parker Probe 239,167 years! We probably don’t need to get into the amount of time it would take the Parker Probe to get to the nebula in the first place.
“Space is big. You just won’t believe how vastly, hugely, mind-bogglingly big it is.” Douglas Adams – A Hitchhiker’s Guide to the Galaxy
Collecting the data I had anticipated this one being a little difficult to find. IT is found roughly on the line between two stars of the winter triangle – Betelgeuse, and Procyon. But, there are really no large magnitude stars in close proximity to help get it in the tight frame of my 300mm lens. I was please that it took me only about 10 minutes to get it in frame. However, because I was hoping to grab some of the much dimmer gases that can make up a sort of stem of this rose, I spent another 30 minutes trying to frame it just so. This turned out to be time wasted. In order to get this dim gas to show, much more integration time would be necessary than what I was able to collect on a single night.
Date and location Imaged on the night of 17/18 February 2023 at Danville Conservation Area in Montgomery County, Missouri (Bortle 4).
Dark period: 19:10 – 05:19
Target period: 15:20 – 02:08; Zenith 20:44
Conditions Clear skies over the course of the session. Temperature: 31° – 27° F. Winds forecasted to be 6-8 mph but seemed lower than this.
Equipment Astro-modified Canon 7D mkii camera, Canon 300mm f/2.8 lens, Skywatcher Star Adventurer tracker without guiding on a William Optics Vixen Wedge Mount. Gitzo CF tripod, Canon shutter release cable, laser pointer to help find Polaris and sky targets, lens warmer to prevent dew and frost on lens, dummy battery to power camera, lithium battery generator to provide power to camera and dew heater, right-angle viewfinder to aid in polar alignment.
Imaging Details Lights taken (ISO 3200, f/2.8, 25 second exposures) 779. 61 frames dropped due to poor focus, 217 frames dropped due to tracker error, 10% frames dropped in stacking instructions. A total of 450 frames used in integration for a total of 3.13 hours. Darks: 39 taken at the exposure time listed above. Bias and Flats: Not taken. Removed most vignetting and some chromatic aberration while converting RAW images to TIF.
Processing RAW files converted to TIF in Canon DPP, stacked in Astro Pixel Processor, GraXpert for gradient removal, StarNet++ for separating stars from nebulosity, Photoshop CS6 for stretching, recombining stars and nebulosity and other cosmetic adjustments.
This one was a bit tougher than I expected, mainly due to the StarNet software not wanting to work the first several times I tried. I captured more of the hydrogen alpha in the surrounding regions than this image depicts but, because it was so faint, nasty artifacts appeared during the stretch. I was forced to leave much of this out of the final image due to this. I think in order to do this properly I would need much more total integration time.
Problems and learnings This one went about how I had expected except for one thing. I was devastated to learn that I had not acquired critical focus for roughly the first 45 minutes of imaging. This was even more of a blow as this time coincided with the object being at or near its zenith, meaning I lost some of the best potential data gathering of the night.
I have also been collecting some data on how many subs I throw away due to errors in tracking. In this case, 35% of the subs I took were thrown away, which seems to be close to my average when using this lens at these exposure times. I dropped the exposure time to 25 seconds in order to help reduce this but I think this issue is mostly due to the tracker being at or above its limit in regards to payload and focal length. For this reason, I am investigating a new tracker that should meet my needs nicely for a 1-2 minute exposure with the above kit and a keeper rate of greater than 90%. Keeping my fingers crossed for that company bonus this year. 😉
Conclusion This is another very popular and relatively easy object that most astrophotographers tackle early on. Overall I’m pleased with the outcome. I like the detail and the colors but I think that better processing might bring these out better even with the data I have here. Always learning. This object is better imaged in December or January, when more time with it can be had in a single night. I look forward to trying this one again someday.
After M42 had began to drop to low in the western skies, making any further attempts at photographing it futile, I decided to try and find the newly discovered, long period comet, C2022 E3 (ZTF). I was unable to see it with my naked eye at my location, but with careful scanning using binoculars, I was able to find it. At 03:00, I was happy that getting it in the camera viewfinder wasn’t too difficult a task. I knew this wouldn’t be the best image of this comet, but I didn’t want to pass up the opportunity. This is a stack of 77 20-second images. You can make out the green color of the comet’s head, proposed to be due to the presence of diatomic carbon, along with two tails. The broader, warmly colored tail is the dust tail and the fainter tail below is the ion tail.
The comet’s closet distance to earth will appear on February 1st, where it will be close to the north celestial pole. The waxing moon will make it harder to see. So, if you plan on trying to see this one yourself, you should wait until the moon sets.
The Great Orion and Running Man Nebulas (M42 and M43) After trying for three months, we finally had a night of very good conditions to create the closeup of these two objects that I have been hoping to accomplish. The winds were low enough that I felt comfortable using the big 300mm lens. We had zero clouds the whole night and although this was the night before the new moon, the 3% moon that was left didn’t rise until after 05:00. Humidity was high, so seeing and transparency weren’t the best and the frost was building, but I’ll take a night like this anytime. In addition, since these objects set around 03:00, I had the opportunity to photograph a new comet in our sky, C/2022 E3 (ZTF). This comet appears to have an orbit that won’t put it back by earth for about 50,000 years, so I thought now would be the best time to try for a photograph.
A part of the asterism known as Orion’s Sword within the Orion Constellation, the Great Orion Nebula (M42) is an enormous cloud (~40 light years in diameter) of fluorescent gas, composed primarily of hydrogen, which lies approximately 1350 light years from earth. It also contains traces of helium, carbon, nitrogen and oxygen. M42 is a diffuse, emission-type nebula that is home to star formation. The bright nascent stars, primarily Theta Orionis – the four stars that make up the asterism known as the “Trapezium,” are found within the bright core of the nebula. Via a process known as photoionization, these stars provide the ultraviolet radiation that excites the hydrogen and other elements to emit the visible light by which we can see the fine, multicolored mackerel patterns throughout M42. There are thought to be about 2800 young stars, mostly unseen via visible light imaging, within the nebula.
The M42 nebula is both the brightest and closest such star forming nebula to earth, making it one of the most viewed, photographed and studied deep sky object. Evidence suggests that the current brightness (equivalent to a 4th magnitude star) may be a recent phenomenon. This is supported by the fact that M42 and M43 were not mentioned by the early astronomers (e.g. Ptolemy – 2nd century CE, al Sufi – 10th century CE, and Galileo – 17th century CE) despite their close observations and records of this area of the sky. The accepted first discovery of M42 was by the French astronomer, Peiresc, who first published his observations in 1619.
The Running Man Nebula (M43) is so named for the vague specter that can be seen sprinting across this gaseous body. It is a wedge of nebulosity located northeast of the Trapezium and primarily illuminated by the 7th magnitude “Bond’s” star. I find that M43 is a perfect bit of color and contrast that tops off M42 very well.
Collecting the data (20/21 January) Having had imaged this section of sky in December, I gained experience in collecting image data and processing using multiple exposure lengths. This is important for M42 particularly in collecting fine details in the outer dim gas and dust clouds while also capturing the details in the bright hot core. Overall, imaging went as I anticipated with the exception of a couple new issues that I explain below.
For this session, Miguel and I setup at Danville C.A., as usual, and Miguel brought along his partner, Leela. Miguel wound up collecting the data he needed earlier than I did, and he and Leela were on their way home before 01:00. The forecasts were mostly correct. There was a chance of clouds developing over us around 03:00 but when I was on the road home around 05:00, the skies were still clear. I want to thank my friend, Pete Kozich for his assistance in meteorological forecasting for this and past projects. That is always a big help and much appreciated.
One anecdote to share was something I expected to happen sooner or later. Miguel and I had just started our imaging when a pickup truck pulled into the parking lot, with the driver placing its beams down the road to where we were setup. I immediately thought this was going to be another meeting with a Conservation Agent. When it was obvious they weren’t going to pull out and head off, I stopped the camera and headed over to the parking area. When I arrived, I was met by a group of friendly hunters and their dogs who shared that they were hoping to do some coon hunting. They asked what we were doing and I told them, mentioning that their headlights and any additional lights would be detrimental to what we were trying to accomplish. Thankfully, this C.A. is pretty large with a few different access points. When they understood the situation, they graciously decided to allow us to continue without further disturbance and headed to a different location. I understand these areas are used by different folks with different purposes in mind and was thankful they didn’t try and push the point.
Conditions Over the course of this imaging session, skies were clear of clouds. Winds started at 6 mph and wound up around 2 mph by the end of the night. Temperature ranged from ~34 – 23 °F over the course of my imaging.
Equipment Astro-modified Canon 7D mkii camera, Canon 300mm f/2.8 lens, Skywatcher Star Adventurer tracker without guiding on a William Optics Vixen Wedge Mount. Gitzo CF tripod, Canon shutter release cable, laser pointer to help find Polaris and sky targets, lens warmer to prevent dew and frost on lens, dummy battery to power camera, cart battery to provide power to camera and dew heater, right-angle viewfinder to aid in polar alignment.
Imaging details Lights taken (ISO 3200, f/3.2): 32 seconds (492 taken, 412 used in integration); 16 seconds (165 taken, 148 used in integration); 8 seconds (112 taken, 106 used in integration); 4 seconds (56 taken, 54 used in integration); 2 seconds (63 taken, 61 used in integration); 1 second (61 taken, 60 used in integration). Darks: 30 taken at each of the six exposure times listed above. Bias and Flats: Not taken. Removed most vignetting and some chromatic aberration while converting RAW images to TIF.
Processing I admit, this one was a chore. Almost 15 hours in total, most of this in the stacking at the six different exposure lengths. I’m not completely satisfied with my compositing for the core of M42. Even though I’ve gotten a lot of experience with doing this in Photoshop, I still don’t have the skillset to combine the different stacks into something I picture in my mind.
I think I may be finished with Deep Sky Stacker (DSS). When attempting to stack the 32-second frames, DSS would only accept about half of them. Digging into the reasons for this, I found that DSS is particularly picky about only accepting subs that are above a threshold of star quality. Because I shoot with fast lenses, opened wide, and because I am using an entry level star tracker, my stars would not be considered top quality by any serious astrophotgrapher. I don’t particularly care about this. I’m focusing on the DSO, not taking pictures of fine, perfectly round stars. Wanting to use every possible frame that I deemed useable, and not able to find a workaround in DSS, I needed another option.
I decided to download a trial version of Astro Pixel Processor (APP) because I read that this software works very well, and it allows the user to set the threshold for the acceptability of the frames it uses. This seems to be a nice way to run stacks. APP can analyze every frame and then provide you scoring data for each frame on a few different parameters. It is then easy to set a threshold, letting the software pick the top 90%, for example, or selecting and removing the frames yourself based on your own judgements about what the rating data provide.
APP is definitely more complicated than stacking software I have previously used, but not nearly as complicated as something like PixInsight. Much of what APP offers I won’t have any use for, but, because it gives you the option for doing things either mostly automatically or picking and choosing the settings yourself, I think I have found my new choice for stacking.
A note about colors. I encourage the reader to look up images like mine to see the wide array of colors with which these objects are depicted. There are a few reasons for this. First, subjective decisions. Some imagers just like to play with colors and saturations to create what they like. Another reason is improper color balance choices. These are cases where the colors are not true to what you would see in visible light but were not necessarily the choice of the photographer. The equipment used is another reason for the color variation seen in different images of these nebulae. Some photographers use filter systems designed to pick up enhanced light coming from the specific elements, e.g., using filters that pick up more blue or green light emitted from oxygen or red light from hydrogen. When these frames are put together, there is always going to be differences between any two images and not necessarily like what the human eye perceives. It is my goal to create images that are as close to neutrally balanced as possible. But much like the question of what the proper pronunciation of Latin should be, there simply is no agreed upon answer for what are the trues color of many of these objects.
Problems and Learnings It seems I can’t get through a session without a lesson or two to learn. I had three from this night’s imaging, but I am pleased that none of these wound up ruining my efforts for this evening and that I was able to diagnose the issues to avoid making these mistakes again.
During this session, the 300mm f/2.8, which until this night, had never had much of an issue with losing focus over the course of a night, began exhibiting this problem quickly. For the first couple of hours, I found I needed to check and reacquire focus nearly every 30 minutes. Then, it seemed to level off and hold focus for the rest of the night. The outside temperature was not changing rapidly, and I had the rig exposed to the elements for close to two hours before beginning imaging, hence my perplexity. I think I figured it out. I had setup everything and had it ready to go about an hour before sunset but did not turn on the dew heater until shortly before beginning imaging. The lens, having already acclimated and reaching the same general temperature as the air, began changing temperature when the lens heater was powered up, and therefore, began losing focus due to this change in temperature. I now realize that in the future I need to turn on the lens heater immediately after setting up, so the lens reaches its steady state before imaging starts.
My next lesson learned was even more perplexing. Early on, when beginning to take the 16 and later the 32-second exposures, I noticed a faint glow on one of the long sides of the frames. I knew that there was nothing in that portion of sky that should show up so profoundly in that area of my composition and that it must be something of external origin. I checked and made sure there was no light pollution center in that direction of the sky. I then thought it must be some stray light entering the imaging path somewhere. Maybe the lens hood wasn’t installed correctly and allowing light to “leak” in? During the night, I couldn’t figure it out. But, because it was relatively minor and did not directly affect the main objects, I put it out of mind, figuring I could probably fix it in post processing using the gradient removal software. Then a more worrisome development came to my attention. When looking at my dark frames, which are taken in near completely dark conditions, I saw the exact same glow in them! What was going on here? Now I was concerned. Was there a problem with my newly converted camera? Did they not seal something correctly when they put it back together?
I had to wait until I got some sleep before getting into this research and giving this issue some serious thought. I decided to try taking some dark frames in as dark of conditions that I could possibly make. The glow was still there. I felt I could safely eliminate the possibility that this was due to a leak in the body that was letting light in. Another factor that added to this mystery is that I used “Bulb” mode in my camera to take the 16 and 32-second exposures. I then thought this might be the issue. I noticed that while using continuous shooting while taking my light frames, the camera behaved and sounded a bit different that when I normally shoot this way in “Manual” mode. This must be the cause! But that wasn’t it either. I then tried a series of 30-second dark frames in “Manual” mode and found the glow in most of these as well.
Stumped, I began a conversation with Miguel and fired up the Google machinery. I’ll save you the rest of the unimportant details and let you know that with the help of Miguel and some experienced folks in the proper online forums, I discovered the cause of the glow. It was caused by something called “amp glow.” This is the term for the glow that is produced by the heat of the circuitry inside the camera and, as it turns out, is a common occurrence when shooting with “live-view” enabled with moded dSLR bodies. Using live-view for astrophotography with dSLRs is almost a necessity as it makes it much easier to find your target and obtain critical focus on the distant stars. Why had I not noticed this earlier in my previous sessions in which I also used live view? I am not certain. Maybe it was the combination of using ISO 3200 over the course of a longer evening, allowing for the buildup of heat?
To ensure this was indeed the cause of the glow I was experiencing, I performed some tests, taking 60-second dark frames with and without live-view engaged. Just as I expected, those without live-view engaged had no glow and those with live-view turned on showed it in every frame. Thankfully, this wasn’t a major issue with this project. Using the dark frames at these exposures, which also had amp glow, was supposed to result in the removal of the glow during the stacking process. This was not the case, unfortunately. Even though I had what I believe were the correct settings for this glow to be removed, that didn’t wind up working. I assume the fault lies in me not doing something correctly, but I don’t know how to fix this. The glow following the stack was so substantial, that gradient removal couldn’t do the trick in this case. This forced me to crop the final image more than I had originally designed to remove the area most affected by the glow. To avoid this problem in the future, my new imaging process will now be to use live-view only for acquiring the target and acquiring/checking focus. I will then turn this off and let the mirror slap away when taking my light frames.
The third issue, and simply a mistake in my strategy, is that I was unable to properly resolve the Trapezium. I had thought 1-second exposures would be good enough to allow me to properly resolve the four bright stars located in the center of M42, but these wound up being a rectangular blown out blob. I suppose that 1-second is still too much at ISO 3200. I should have checked these shorter exposures more closely so that I could have adjusted for this. Oh well, a reason to shoot this one again someday.
Conclusion I have wanted to make this image since I first began thinking about getting into astrophotography. These paired nebulae are most astrophotographers’ first object chosen to image and, most likely, the most photographed DSO of all time. This isn’t quite the image I had envisioned in my mind, but it comes reasonably close. I think the primary reason it doesn’t match my expectations is my limited skillset with making composits in Photoshop. I also need to rethink my strategy in shooting high dynamic range objects. Maybe it’s a good thing not to have nailed it on my first try. This gives me the impetus to try again in coming years.
Witch’s Head Nebula (IC 2118, NGC 1909) IC 2118 has been on my list of potential deep sky objects to photograph since I first hear about her. I didn’t think I would have the skills or techniques to do her justice so soon but my plans for shooting M42 with the 300 mm lens were dashed again because of high winds. I studied the area and figured out my desired composition using a 200mm lens and a 1.6 x crop body camera and this is pretty much the result I was hoping for.
Why is this target so difficult for photographing? IC 2118 is known as a reflection nebula, meaning that there aren’t a lot of highly illuminous stars or star formation occurring within this collection of dust and gas. This very dim (apparent magnitude of 13) reflection nebula is primarily illuminated by the 7th brightest star in our sky – Rigel, the left foot in the constellation of Orion. Rigel, located 2.6 degrees to the east of IC 2118, is actually a system of four stars in close proximity. Rigel A is the primary star and is measured to be approximately 120,000 times more luminous than our sun, with an apparent magnitude of 0.13. It is a young star, approximately 8 million years old and has already burned through the hydrogen in its core. It is now burning heavier elements and will one day go supernova – one of the closest stars to us that will do this. When this happens, it is estimated that it will be as visible to us on earth as a quarter moon!
Back to the oh-so-appropriately named Witch’s Head. Due to the blue color of Rigel and the properties of this light scattering off of the gas and dust, this nebula appears blue in color, similar to the reason why our sky is blue on earth. Astronomers are unsure if the nebula is the remnants of an ancient supernova itself or just a collection of dust and gas. Although being close to, or perhaps a part of, the Orion molecular cloud complex, IC 2118 officially lies in the constellation Eridanus. This nebula is approximately 800 light years from earth and of course is absolutely huge. IC 2118 is roughly 1 x 3 degrees in our night sky and roughly 50 light years long. It is not visible to the naked eye from earth, but to give a size comparison of the amount of sky this object would take if we could see it, it would roughly be equivalent in length to six full moons in our night sky.
Collecting the data (27/28 December) It was nice having two opportunities in December to work on astrophotography. Like I mentioned above, I was hoping to do a closeup of Orion and Running Man nebulas but with 10-12 mph steady winds with gusts above 20 mph, I knew I better not shoot with the 300 mm lens. IC 2118 was definitely on my list and could be captured with the much smaller 200 mm lens. The weather forecast was tricky and one of four weather apps suggested that clouds would ruin my night starting around 01:00. Even if so, which it did, I could still get up to six hours on the target.
I was by myself for this session, Miguel having something else, like sleeping I guess, going on this evening. And I setup at the usual location – Danville Conservation Area. It was truly windy and the temps hovered around the freezing point, which was warmer than the last time we went out.
Being such a dim target presented a significant challenge. Primarily, with a 35% luminated moon, I struggled a bit with getting exposure where I wanted. I would have liked to use ISO 3200, but when I started, this put the histogram peak above the 50% line. So I decided to use ISO 1600 using 30 second exposures. When the moon set at 22:04, I knew the histogram peak would drop and it did to a little less than the 20% mark. This was concerning because I knew this would be too close to get the signal to noise ratio I needed, especially with such a dim target. I contemplated changing the ISO up to 3200 but then I wouldn’t be able to stack the two sets taken at different ISOs with my dark frames while being able to use the process to remove satellites and plane trails. Instead, I opened up the aperture from f/3.5 to f/3.2. This gave me a third stop more light for each sub. I wasn’t sure if this was going to work, especially not being able to see the target in an individual frame!
As I feared, clouds came in heavier than 3 out of 4 weather apps and a meteorologist predicted! So, I shut down around 01:45 and made it home by 03:30 – an early night!
Equipment Astro-modified Canon 7D mkii camera, Canon 200mm f/2.8 lens, Skywatcher Star Adventurer tracker without guiding on a William Optics Vixen Wedge Mount. Gitzo CF tripod, Canon shutter release cable, laser pointer to help find Polaris and sky targets, lens warmer to prevent dew and frost on lens, dummy battery to power camera, cart battery to provide power to camera and dew heater, right-angle viewfinder to aid in polar alignment.
Imaging details Lights taken (30 seconds; ISO 1600; f/3.5 and f/3.2) 671 taken, manually removed bad subs due to tracking errors, winds and clouds for a total of 433 used in integration. Darks: 49 Bias and Flats: Not taken. Removed most vignetting and some chromatic aberration while converting RAW images to TIF.
Processing Not knowing for sure if my individual sub-exposures were going to be accurate, I was eager to get to the processing. After removing obviously bad sub-exposures, I plugged the 433 photos into Deep Sky Stacker and told it to use the best 90% of those, giving me a total of 3.25 hours of integration time.
It’s amazing how I can get sucked into processing these DSO images. This one only took me about four hours from start to finish but it seemed like no time at all. I also used GraXpert to remove gradients and various steps in Photoshop CS6.
Problems and learnings This is definitely an object you want to shoot without light pollution and with as much time as you can possibly get on her. With roughly half my night lit by the moon and not getting as much time as I had hoped for, I am very pleased with the outcome. I hope to try this one again someday. Being a winter target, it is possible to get 8-10 hours on this target in a single night. This would help bring out the surrounding dust and provide better definition of the target herself. I did wind up using some subs that had light clouds, providing the halo around Rigel that normally wouldn’t be there. I don’t think this hurt the image, however. I could also shoot her with the 300 mm lens but this would eliminate Rigel in the frame and I don’t think would be nearly as interesting.
Conclusion This is the second image of five I hope to make around the Orion molecular cloud complex. I did not expect to shoot the witch this soon but I am pleased that I have learned enough to make a competent image of this dim and challenging subject. After doing this a few months in a row, I am much more confident in what I am doing and using my kit has almost become old hat. As long as the weather gods bless me, I am feeling much more confident in being able to capture and process the targets that are within my capabilities. I hope to upgrade my tracking mount within the next year or two but I will continue with what I have at the present.
M42, B33 and friends The Orion molecular cloud complex is one of the most active regions of star formation and contains the brightest emission nebulas from our vantage point. The complex is between 1,000 and 1,400 light years from earth and is hundreds of light years across. This frame is just a small but significant portion of the whole complex and is one of four compositions I plan on making of this portion of the sky over the next couple of years.
Let’s discuss the objects. Even those with a small familiarity with the night sky should be able to determine where these objects are located once explained. Let’s start at the bright star in the upper left-hand corner of this image. This is Mintaka, the brightest (double) star in the asterism of Orion’s Belt within the Orion constellation. Going down and to the right, we reach the next star in Orion’s belt – Alnilam. The final star in Orion’s belt, Alnitak, is to the lower right of Alnilam. All three of these stars are tens of thousands to hundreds of thousands more luminous than our Sun. Alnitak is the primary reason we can see the reddish nebulosity known as the Horsehead nebula (IC434, B33). It’s strong ultraviolet radiation excites the hydrogen gas making up this nebula and releases hydrogen-alpha wavelengths that we can pick up on earth. Just a little to the lower left of the Horsehead is one of my favorite pieces in this composition. This is a very young star, still condensing and making its way out of the nebula.
To the left of the Horsehead is the Flame nebula (NGC 2024 and Sh2-277). This emission nebula is another birthplace of stars. It contains hundreds of young stars but specialized X-ray and infrared imaging is needed to resolve these.
To the right hand side of the image we first come to the comparatively smaller nebula known as Running Man (Sh2-279) and to the right of it lies The Great Orion Nebula (M42). M42 makes up a portion of the Orion’s Sword asterism and is the brightest nebula in the night sky. It is so bright it can be seen with binoculars or a low power telescope from dark skies. It is also the target of the first deep sky image ever taken – by Henry Draper in 1882. Within the star nursery that is M42 are approximately 700 young stars in various stages of formation. Throughout the image is a lot of darker nebulosity that is quite dim, requiring ample amounts of exposure time to resolve.
Collecting the data My original intent for this session was to image the usually paired group of Running Man and Orion. However, we were fighting to find a good night’s sky in December. The night we chose was forecast to be pretty clear but with 7-10 mph winds, gusting to 20mph. Because of the forecasted winds, I decided it wasn’t prudent to use the large and heavy 300mm lens that would be required to make these two the primary target. So, I decided to go with another composition that I had planned to do later. I used the much smaller and lighter 200mm lens that wouldn’t catch nearly as much of the wind and make getting accurate tracking of 30 second subexposures much easier. This image comprises a section of sky approximately 4 degrees by 6 degrees.
As I explained in last month’s image, M42 has a very wide dynamic range in intensity of its brightness. Due to this, I needed to take several sets of subexposures at different exposure lengths. Ultimately, I took seven different exposure length sets but only wound up using four of these in the final image.
Miguel and I imaged at our usual locale of Danville Conservation Area. On this night we ran into our first Conservation Officer who asked us what we could possibly be doing on such a cold and windy night. At first I was worried we would be shut down for the night as he mentioned that all conservation areas in the state were closed between 10:00pm and 4:00am. But, after some explaining and discussion he decided we were OK doing what we were doing and where we were doing it.
The sky forecasts were a little variable between the different apps we use. Some suggested that the skies would be mostly clear around sunset while others had clouds lingering until midnight. Thankfully, the skies cleared like magic a little after 9:00pm. We lost a couple hours of imaging time but in December you have to take advantage of what you can get. Temps were cold as you might expect ranging between -3 and -7 degrees C over the course of our session. I guess the temperature swing wasn’t as drastic as the last time I used the 200mm lens back in September because the focus of the lens wasn’t changing nearly as much as it had while imaging Andromeda.
Equipment For this image, I broke in a few new pieces of equipment. First, this was the maiden voyage of my astro-modified Canon 7D mkii. This camera has its IR-cut filter removed. This modification allows for much more of the Hydrogen-alpha light to hit the sensor that is mostly blocked from stock dSLR camera bodies. In order to get as much of that warm coloration seen in the Horsehead and Orion nebulas with a stock body would have required much more integration time. As mentioned above, I used the Canon 200mm f/2 lens. When used with this crop-body camera, this gives an equivalent focal length of 320mm.
Another new piece of gear allowed for less hassle over the course of the night. I purchased a “dummy” battery that allows me to power the camera over the course of the entire night with my “little” cart battery and an inverter that I typically use for attracting moths at night. I love finding new uses for stuff I already have! The $20 cost of the dummy battery was a most welcome addition to my kit.
I also picked up a really nice right-angle viewfinder that attaches to the end of the polar scope of the tracking mount. To make the rig as sturdy as possible, I like to set it up low to the ground. Doing this requires me to often crouch low or even lie on my belly while wrenching my neck to be able to see through the polar scope. This is not a comfortable position to be in while doing the fine tuning of the controls on the wedge mount to get precise polar alignment. This new piece of kit allows me to simply look down and much more comfortably make these fine adjustments with both hands.
Finally, I picked up a lens heater that will prevent the formation of dew and frost on the lens objective. This was also run from the main battery and inverter and seemed to do the job. Previously, I used chemical heat packs for hand warming that I attached to the end of the lens with a velcro strap. This new powered dew heater should be able to be used with all the potential lenses I use for astrophotography.
I guess I’m getting a little more tech involved but nearly as much as my astro imaging partner, Miguel. See discussion below.
Thanks a lot to my patient wife Sarah for the early Christmas gifts!
Other equipment: Skywatcher Star Adventurer tracker without guiding on a William Optics Vixen Wedge Mount. Gitzo CF tripod, Canon shutter release cable. Laser pointer to help find Polaris and sky targets. Lots of layers to protect me from the cold!
Imaging details Lights taken (ISO 3200): 30 seconds (389 taken, 284 used in integration); 15 seconds (108 taken, 90 used in integration); 8 seconds (209 taken, 194 used in integration) 1 second (195 taken and used in integration). Darks: 30 taken at each of the 4 exposure times listed above. Bias and Flats: Not taken. Removed most vignetting and some chromatic aberration while converting RAW images to TIF.
Processing I knew this one was going to be a challenge, due to using the new astro-modified camera and handling different exposure lengths to capture the dynamic range within M42 that I would need to show the details in the core of the nebula. I believe I have the data needed to do a better job on this part of the nebula but after nearly ten hours spent on the computer, I was happy enough with what I got.
What really came as a surprise was the amount of satellites that crossed this portion of sky. I estimate that 90% of my 30 second sub frames had at least one, if not several, satellite and/or plane trails. This technically isn’t a problem because in the stacking software I use (Deep Sky Stacker), you can handle the satellites by using Kappa-Sigma Clipping stacking within DSS. However, when using the high dynamic range (entropy weighted average) stacking mode, which will blend the different exposures automatically, you cannot use Kappa-Sigma-Clipping to remove the trails! Or at least not that I have been able to figure out. Therefore, I had to stack each of the sub-exposure sets separately and then blend using layers in Photoshop. This wasn’t too terrible but it did require a lot more time on the computer.
Problems and learnings I guess I didn’t learn my lesson the first time. Again, I walked away from the rig for 45 minutes without making sure the camera was taking pictures! I guess I was too interested in getting back to the car to read my book (Hail Mary by Andy Weir) and didn’t do my final check. It didn’t ruin the night but man was I pissed that I lost nearly an hour’s worth of potential integration when the targets were near their zenith. Never again!
I was also pleased to see that the output from DSS was relatively color balanced, requiring me to do very little to get accurate colors. Colors in these objects are subjective and free to change, but I strive to be as “accurate” as I can be. I was concerned by this because in the astro-modified cameras, naturally the red light is most abundant and many images taken with these cameras, when not color corrected, show way too much gaudy reds. I did not want my final product to look like that.
Probably my biggest regret is with the framing of this one. If I could do it again, I would have moved the frame more diagonally, allowing Orion and the Running Man to drift more towards the upper right-hand corner. This would have made a much better composition. But, I was primarily focused on keeping Mintaka in the upper left-hand corner as an anchor point for me to be able to see how much drift from the tracker was occurring. I’m going to try and think through the framing and composition better in the future.
Conclusion Overall, it was another fun night and I am pleased with the final outcome. Miguel and I enjoyed ourselves as usual and we keep finding new things to learn and experience with each outing. I’m looking forward to seeing Miguel’s image. He focused on Orion and Running Man – my original target for the night.
Aside I have mentioned numerous times previously that Miguel and I work together, typically imaging the same targets. However, we go about doing this in very different methods. Whereas I go about things in more of a manual, craft-like manner, Miguel is using state-of-the-art consumer level equipment. I realize that nobody cares (nor should they!) about what it took for the photographer to make their final image, but I thought it would be good to explain our differences in how we go about our image making processes.
Bill I use dSLR cameras much like the cameras anyone uses for daytime photography and typical fast (f/1.4 – f/2.8) camera lenses that allow me to capture as much light as I can. I use a standard consumer tracking mount that is considered portable. All it does is work by using gears and belts to point the rig at the same portion of the sky to match the change in position of the stars due to the rotation of the earth. I need to do the process of polar alignment manually, which is a PITA! I also must find and position my target by myself, using my eyes or a laser pointer to help me find that night’s target. I must also manually change the camera’s settings to what I need them to be and must acquire proper focus, which is not easy to do with a camera lens at these wide open apertures.
Miguel By comparison, Miguel lives on easy street! His imaging rig is composed of a temperature-controlled dedicated astronomy camera attached to a William Optics Redcat 51 apochromatic refractor AP scope. He uses a similar tracker but his is connected to a computer that is also connected to his camera and lens via a focus adjuster. This gives him three significant advantages. First, after pointing his polarscope towards the north, the computer polar aligns for him. He also has “go-to” capabilities. He simply tells the computer which object he wishes to target and the rig moves there! Even better, he can tell the computer the specifics on how he wants the target framed! Once on target in the framing he indicated, his rig now provides autoguiding. This means that the computer makes fine repositions during the imaging session, correcting for errors in the tracking that my rig suffers from. This means he can obtain much longer sub-exposure times. Where I am kept at 30-60 second exposures without significant star trailing, Miguel can get exposures in the 3-5 minute range. A distinct advantage indeed! To top it off, the computer in Miguel’s rig will obtain perfect focus for his scope and keep it there throughout the imaging session.
Miguel has spent a lot of money and time learning the components and how to control the different aspects of his computer software. I am not trying to sound the holier here, but I thought it would be interesting to describe the vast differences in our techniques and imaging rigs. I’m not hating, Miguel! 😉
The Pleiades Star Cluster (M45) The Pleiades, or as it is called in Japan – Subaru, has been near the top of my list of deep sky objects since I began to play in astrophotography. This star cluster is one of the most prominent objects in the night sky and can be easily seen with the naked eye, although it is a stunner through binoculars or a scope. Folks with very good vision under dark skies have been reported to be able to see seven stars, giving this cluster another of its names – the Seven Sisters. Whatever you want to call it, M45 is a relatively young cluster of approximately 1500 young stars (the cluster is thought to have formed around 100 million years ago). The majority of these stars are bright-burning blue stars and, as this cluster passes through a dust cloud in the Milky Way, the blue light from the brightest stars reflects off this foreground dust creating the blue nebulosity that surrounds them. M45 is potentially the closest star cluster to earth at about 444 light years away and is the nearest Messier object to earth.
Collecting the data Along with the Orion Nebula (M42), M45 is considered to be one of the hard easy targets for astrophotographers. It is relatively bright with a magnitude of 1.6, so that helps with not needing particularly long exposures that many dim DSO’s require. However, there is a lot of dynamic range in the light coming from the cluster, with bright stars, a nice nebula and much dimmer dust clouds that are not well lit by the stars. In my image presented here, you can see some of this dimly illuminated dust throughout the image. To really capture this dust well, a lot of integration and/or longer sub-exposures are required. I am happy to have pulled enough of the detail in these areas with heavy processing without too much injury to the photo quality.
To account for the high dynamic range presented with this target, I had planned on taking two sets of “lights/subs” so that I could capture the fainter dust and nebula without overexposing the bright primary stars of the cluster. Then, I could process these two sets in a way to blend the two exposures, hence capturing the total dynamic range presented. This is pretty easily said, but at my level of experience, it was harder to put this plan into place. I knew that I would have to experiment a little and make the decisions on my camera settings on the scene.
As usual, Miguel and I imaged M45 at the Bortle 4 sky location at Danville Conservation Area. Other than a few late hunters leaving with the sun, we had the place to ourselves except for the owls, coyotes, deer and armadillos. The forecasts were true and we had clear skies with mediocre seeing and transparency. It was a cold night! Temperatures ranged from the low 20s to about 14 degrees Fahrenheit over the course of the night. The heat packs on my lens and Miguel’s battery powered heat bands on his scope really did the trick with preventing dew and frost from forming on our optics.
Equipment For this target, I used the unmodified Canon 7D mkii and a 300 mm f/2.8 is lens. As usual, I reviewed my options at Telescopius and found that this was a good focal range (480 mm focal length equivalent). However, this choice would give me some problems.
I used the Skywatcher Star Adventurer without guiding mounted on the William Optics vixen style base. Although this is a great tracker and platform, I knew I would be pushing the boundaries of what this unguided setup could handle. At first, I could not get good tracking results with this heavy payload at 30 second sub-exposure lengths. With most photographers imaging this at 1-2 minutes, I knew I was really going to be pushing to get the signal to noise ratio where I needed it to be. But, the 30 sec subs where just unusable, so I took the first set at 20 seconds and ISO 1600. This would turn out to be a nice exposure for the brightest stars.
As I sat in the car thinking between outings to check battery life and focus, I knew I needed to find a way to increase my sub-exposure/signal if I wanted the image to be close to what I was envisioning. Around 11:00pm I decided to redo my polar alignment, rebalance and tighten down the rig to see if I could get to 30 second subs. I tried a few shots and although it wasn’t perfect, it looked like this could work. I checked the histogram on the back of my camera and it still wasn’t where I needed it to be. Although I was hesitant, I decided to increase the ISO to 3200. After doing this and checking the histogram, I knew I hit the sweet spot for the individual sub-exposures. Hopefully my calibration frames and the total integration time would keep the signal to noise ratio where I needed it to be. I shot another couple of hours at these settings to get the exposure I needed for the nebulosity and dust.
Imaging details Lights: 465 light images taken at 20 sec/ISO 1600 (manually removed obvious bad subs and used 408 subs for a total of 136 minutes of integration). 338 light images taken at 30 sec/ISO 3200 (manually removed obvious bad subs and used 216 subs for a total of 108 minutes of integration). Darks: 32 taken at each ISO Bias and Flats: Not taken. Removed most vignetting and chromatic aberration while converting RAW images to TIF
Processing I tried this two different ways. First, I created two different stacks in Deep Sky Stacker (DSS) from the two different sets of light data I had collected. I also stacked everything together in two different groups within DSS and used their “Entropy Weighted Average” (HDR) stacking mode. I then stretched and processed. For the first option, I used masking in Photoshop to blend the two “exposures” together to create the HDR effect. It was most likely due to the differences in how I processed following the stacking (this is not something I cannot do by recipe yet), but I found I like the image better when I started from the HDR stack by DSS, which is presented here.
Problems and learnings I already went into some detail about the struggle to get sub-exposure lengths where I needed them, pushing the boundaries on ISO and the need to redo PA and balancing to get to the sweet spot. There was also the time where I walked away for an hour without the shutter release button on the cable being engaged. Overall, I see the need to increase my efficiency. Not including the time it took to take the dark calibration frames and breakdown for the night, I estimate that we had about eight hours of good night skies to take our light frames. I was only able to capture about 5.5 hours of data in this time. Part of this is due to the time it takes to stop the process to check battery life and focus – this will always be the case. But I also lost time with the other things I mentioned. If things had gone perfectly, I could have had about two more hours of light frames. Ah well, I should get better with experience.
Conclusion This was a long and cold night but I think Miguel and I both think it was well worth the time and effort. I remember getting into bed a little after 6:00am, wondering if I had collected the data that I would need to make the image I had envisioned. It definitely isn’t perfect. I had to toss a lot of the 30 second sub-exposures due to pushing the boundaries of unguided tracking with that heavy payload and focal length. Even after that, a close look will reveal some ugly and mishappen stars due to imperfect tracking and shooting with the lens wide open. I’m not too concerned with the star quality, however. As long as the target looks good, I am happy. Maybe some day I’ll revisit M45 and use the 200mm lens. I should easily get 30-60 second subs with that lighter rig and hopefully have more of the prominent dust in a wider field of view.
I originally photographed M31 in August of 2020 as my first serious attempt in photographing a deep space object (DSO). I did not make many other attempts in DSO photography until the past couple of months where Miguel and I have had hard times thinking about anything else. There are multiple sides to this type of photography and so many ways to improve and learn. This is definitely the most technically challenging photography I have ever done. I’ll say this new attempt at M31 is a significant improvement over my first, mainly due to increased integration time and learning better processing techniques.
The Andromeda Galaxy (M31) You can learn a little about this section of sky by visiting my first post. In addition, here are a couple other factoids about this galaxy. One of the coolest things I’ve learned since getting into astronomy and DSO imaging is the size of a lot of these objects relative to other things that we all routinely see in the night sky. Sure, stars are small in our vision and there are a lot of very small objects that need very large focal lengths to see. But, many DSOs are actually very large. We don’t notice them due to their low magnitude of brightness. Many nebulas cover large parts of our sky, for example. For M31, it’s apparent size on the long axis is ~ 3.167 degrees. The size of the full moon is ~ 1/2 a degree, so M31 covers an area a little more than six full moons!
Andromeda was first formally described by Persian astronomer Abd al-Rahman al-Sufi in the year 964. Did you know that many of the first astronomers were living in the middle east? It’s true – many of the stars still carry their original Arabic names. Andromeda and other similar galaxies were originally thought to be groups of gas and stars within our Milky Way. The discovery and proof that Andromeda was its own “island universe,” like our own, did not occur until the 1920s. Over the last century, M31 has been extensively studied and is now thought to contain ~ one trillion stars.
Collecting the data The new moon period, which allows for the best low-light conditions for astrophotography, in October is troublesome. Miguel and I checked and double checked the forecast and found the best potential night was on October 22/23. We are finally getting some rain in eastern Missouri and most of this period is forecast for significant clouds. The night we chose was mostly cloudless but was not perfect. Winds were 10-13 mph with regular gusts up to 20 mph. In addition, seeing and transparency were on the poor side due to the winds and high humidity. This was not optimal, but it was still the best apparent night to try, so we did. To aid with the winds, we setup on the downwind side of a couple of hay bales and they did a pretty good job of acting as wind breaks. We imaged at my favorite site – Danville Glades C.A.
Equipment I had originally planned to shoot with my Canon R5 and the Canon ef 400 mm f/4 do ii lens. This framed M31 very nicely in Telescopius and I was eager to see how this lens performed in astrophotography purposes. However, with the winds forecasted, I decided to use a smaller lens that would be less likely to be affected. I wound up using the Canon 7D mk ii and the Canon 200 mm f/2.8 lens instead. This put M31 slightly smaller in the frame, but I thought it would still stand out well enough after a marginal crop.
I used the Skywatcher Star Adventurer without guiding and used my new William Optics vixen style base to mount the tracker on. This mount in combination of using a green laser pointer allowed for very good and easily obtained polar alignment. I’m happy to say that I need not dread getting PA any longer and I can make this step just part of the routine.
Imaging We had some clouds early on in the night. This wasn’t too much of a problem because they cleared out by about 9:30 pm and Andromeda was still in low latitude sky glow until about 10:00 pm. Imaging went pretty well. I did not have to throw out many lights due to wind or tracking errors. One problem that did become apparent was the quality of the stars. When wide open, this lens produces fat stars with pretty bad chromatic aberration. This was probably exasperated by the poor seeing and transparency. I knew this could potentially be an issue but wasn’t too concerned as I was mostly concerned about the galaxy. Anyway, next time I will stop this lens down by 2/3rds of a stop to try and improve this. The settings I used were f/2.8, 30 second exposures at ISO 1600.
Lights: 492 light images taken (manually removed obvious bad subs and used 447 subs for a total of 223.5 minutes of integration). Darks: 36 Bias: 50 Flats: Since flats are a pain to take and since I am using a camera lens that can be corrected for vignetting when processing the raw light files to tif format, I did not take or use flats for calibration. This was the first time I tried this and it seemed to work very well. This will be my new strategy going forward.
Processing Deep Sky Stacker worked! This was the first time I had good enough quality subs that DSS would register and process everything. After about one and a half hours of processing, DSO had processed my linear image. Processing was the biggest learning revelation I had from this project. Pieces finally came together. After stacking in DSS, I used various manual techniques in Photoshop along with StarNet for star removal, GraXpert for gradient removal and Astronomy Tools action set. I finally have a big picture of my step-wise work flow and this should get easier and better going forward.
Conclusions Including driving time, setup time, imaging time and processing time, I estimate it took about 20 hours of concentrated work to produce this one image seen here. When compared to my previous attempt of this object, I am quite satisfied by the results and the time spent was well worth it to me. The increase in integration time along with my improvements in post processing really paid dividends. Maybe I’ll try this target again in a couple of years if I have made improvements in equipment, techniques and processing.
The Pacman Nebula (NGC 281) The Pacman Nebula is a large emission nebula that is approximately 48 light years across and nearly 9500 light years from earth. It was named for its resemblance to the popular Pac-Man character in video games, although you’ll probably have to use your imagination to see this in my image (Pac-Man is facing towards the top of the image). Unlike the the popular Namco mascot, this Pac-Man does not gobble up dots, it is actually creating them; NGC 281 is a star forming region that lies near the constellation Cassiopeia.
Collecting the data Miguel, who is now getting serious into deep sky object (DSO) photography, and I met at what is now my favorite location for this work – Danville Conservation Area in Montgomery County, MO. This is classified as a Bortle 4 sky location and we were working under near perfect conditions of a new moon, no clouds, low winds and cool temps (mid to low 40s). Selecting a great night was one of the successes of this project. Miguel was just beginning to work on his new rig, attempting polar alignment for the first time and trying out his more sophisticated system of go-to and guiding. I use a simple unguided star tracker and the camera gear I use for normal daytime photography and had my target in mind and planned a night of imaging.
Gear used Canon 7d mkii, 300mm f/2.8 lens is mki, Sky-Watcher Star Adventurer tracking mount with extra counterweight balance, Bahtinov focus mask, red-light scope, heat packs used for prevention of dew formation on lens, all setup on a sturdy Gitzo carbon fiber tripod and anchored to a concrete block.
Imaging details Lights: Approximately six hours with 30 second subs (manually removed obvious bad subs and used 512 subs for integration. Darks: 32 darks captured in field after imaging Flats: 40 flats taken the next day from home Bias: 67 bias images
Processing Image shown here was stacked using Sequator. Stacked file was processed in PhotoShop CS6, manually following processes described in various YouTube videos. See below for details learned from this processing session.
Problems and learnings This was a good night but definitely not perfect. Again, I struggled with getting proper polar alignment. My main issue was not identifying Polaris, necessarily, as we were easily able to find it with our naked eyes. The problem came from being able to correctly identify the star while looking through the reticle. Ultimately, I picked the most likely candidate and went with that. I didn’t have much star trailing in my 30 second subs, so I think I did an OK job. I did notice that the tracking was off and I had to recenter the target about once an hour, but that is due to using an unguided tracker and the weight of my rig. This is something I’ll just have to remember to do with future objects.
I have picked up a couple pieces of gear that will dramatically help with achieving proper PA on future projects. First, I purchased a green laser pointer that I can shoot directly through the reticle and line up perfectly with Polaris. More importantly, I finally picked up a new wedge/base mount to support the tracker. This is the piece that is critical in getting proper PA. The mount that comes with the Sky-Watch Star Adventurer is severely lacking in many ways and is frankly a POS. The William Optics model I now have (see photo) is all metal, allows for more precise control in declination and is much easier to control right accession with. The differences are like night and day! I didn’t have these two things for imaging NGC 281, but I have them now and tried them in the yard one night and achieved perfect polar alignment in less than 15 minutes! I feel much less anxiety about this step now and wish I hadn’t waited so long to pick up this base mount.
The biggest mistake of the night was something I was aware of but simply forgot to handle. I left the settings for auto orientation on in the camera. This means, as the mount tracked the object over the course of the night, about half of my images were in the horizontal orientation and half of them were in the vertical orientation. This is a much bigger problem than it seems. In most software, you can change the orientation of an image with a simple mouse click. However, the orientation is actually embedded in the exif data of your RAW files. I came to find out that most stacking programs will not orient all of the files for you and, therefore, I was losing half of my light subs in the stacking process. It is possible to change the exif data to make them all the same, but this requires computer skills that I simply do not have. Thankfully, Sequator did accept all of my subs, but it is not the best software for stacking DSOs. I would love to fix this in the data I have collected for NGC 281 and be able to stack in Deep Sky Stacker or ASTAP one day, but I will definitely remember to turn this function off in camera in the future.
Processing after stacking was the usual barrel of fun. I found it a little easier than I did for M31, but I think I have a long way to go. I was hoping to get much more detail in NGC 281. I think I had ample integration time and feel there may be some detail I can pull out with better processing. Maybe the fault lies in my images themselves and I could do better with PA and tracking. It might also have to do with the focal length. With the 480mm focal length equivalent used for this object, I don’t have much more opportunity to improve here, but I could have used a 1.4x teleconverter and get 672mm focal length equivalent. I think there was room to do this with this object, but I would have had to recenter more often and lost some light gathering in the process. Maybe next year!
Conclusions Despite the final outcome, which I am satisfied with, this was a lot of fun. I’m finding that I can have fun doing almost anything as long as I am outside. This is getting truer all the time. Although this process has its frustrations and anxieties, I guess you can call that a “good stress.” I’ll always remember the pair of Barred Owls squawking away at each other and the coyotes howling and barking on at least three sides from where Miguel and I worked. In addition, while I was breaking down at about 3:00 am, two armadillos noisily burst through the grasslands, coming up to within ten feet of me to see what I was doing.
My hope is to continue this and image one object a month. I think I can sacrifice one good night’s sleep a month for such experience, learning and memories.
During the most recent new moon, I finally took out my star tracker and kit to try my hand at photographing a deep sky object (DSO) for the first time. I knew this was going to be challenging and this first attempt would be more for learning than producing an image that I would be excited about. However, thankfully it was both – it was a beneficial experience in that I got practice in all the process surrounding making an image of this sort (I will go into details below), and at the same time the final image turned out better than I expected, especially considering the challenges I had. For those of you who don’t care about the process, you can stop reading here – I won’t blame you. For those of you interested, I will provide some of my notes and things learned. You can tell me if it was worth the hassle or not.
The Andromeda Galaxy (M31)
The Andromeda Galaxy is also known as Messier 31 and NGC 224. It is classified as a barred spiral galaxy and is about 2.5 million light-years from earth. It is the largest galaxy in our local galaxy group and is on a direct path to merge with our Milky Way in about 4.5 billion years.
Did you notice? In this image there is more than just the M31 galaxy. There are two other galaxies that move along with Andromeda. Messier 32 is on the bottom side of M31 at about four o’clock. M32 is a compact elliptical galaxy and is comprised of mostly older red and yellow stars that are densely packed. Messier 110 is above M31 in this image and is a dwarf elliptical galaxy. There apparently are at least 11 other satellite galaxies of M31, but none that are apparent in my image to my knowledge.
Collecting the data
For my first attempt, I traveled to the Astronomy Site at Broemmelsiek Park in Defiance, MO. This is an excellent place that provides several concrete platforms along with electrical access for those with equipment that needs it. I did not, but I was looking for an area not too far from our home to find as dark of skies as possible. The sky at this location (Bortle class 5) is darker than where we live (Bortle class 6) and is 25 minutes away. This is a pretty good site for viewing the night sky. I was really excited when I turned my birding scope at 60X power to Jupiter and was not only able to view the banding and colors of the planet, but could also make out four of its moons! However, there was still enough light pollution here to make serious astrophotography a bit of a challenge. Unfortunately, this was more of a challenge due to where M31 was located in the first half of the night. At this time of the year M31 rises from the NE sky and it was not until ~ 11:30 pm that the galaxy rose enough out of the skyglow of civilization to make me a little more comfortable.
For this attempt I was using a Canon 5d mk iv camera and a Canon 300 mm f/2.8 is mk i lens. I balanced this heavy kit on the Sky Watcher Star Adventurer Pro Pack star tracker. Because of the weight of this kit, I used an additional counterweight and bar to achieve balance. This is near the weight limit that this star tracker was designed to hold.
The first step in going about this is to get polar alignment with the celestial north pole. I won’t go into too much detail here, but I found this to be particularly problematic. After trying for 45 minutes I eventually decided I was “close enough” but definitely not at optimal alignment. Getting as close to perfect polar alignment is critical at longer focal lengths and exposure times in order to capture the stars as pinpoints of light. A big part of my problem here was working with the mounting “wedge” that comes with this tracker. I found it quite difficult to get the precise control that is necessary to align Polaris where it needs to be. I will eventually need to replace this wedge with one of higher quality.
After getting marginal polar alignment, my next step was to mount this rig, get it balanced and then point it at the target all while not moving the tripod at all! I am sure I moved it somewhat off the alignment that I managed to get. Because of the light pollution, I was unable to see M31 with my naked eye, which is possible under dark enough skies. This made locating M31 more challenging than I expected. With the help of star charts and astronomy apps on my phone, I eventually found it by taking shorter exposures with very high ISO to be able to compose close to how I wished. This probably took another 30 minutes.
With the mount polar aligned, the target in my sights and the tracker running, I was finally able to collect my data. My settings were as follows: 20 second exposure time, f4 and ISO 1600. A little explanation here is needed. With this tracker and kit, I could theoretically get between one and two minutes per exposure. However, with the imperfect polar alignment I knew I had and the fact this was my first attempt, I decided to go with a shorter exposure. For my aperture, I gave up a full stop of light. However, I was worried about how the stars looked fully open and decided at the last minute to close to f4 to gain a little in the IQ arena. I am not sure this was the best decision or not and will probably try wide-open next time..
I collected 265 “lights” before clouds, that were completely not predicted by all of my weather apps came in and closed me down for the night. Later I cut this down to 225 lights that were unaffected by clouds or airplane lights for a total exposure time of 1.25 hours. While in the field you are supposed to take “darks” – these are frames at the exact settings under the same environmental conditions but you throw your lens cap on. These images are then used by the computer programs to remove the digital noise that is produced during capture. Somehow I forgot to do this in the field and did not remember until I was slipping into bed at 3:00 am. So, I got out of bed and went outside to take them.
Processing the data
It may seem crazy looking at this image, but I spent around 12 hours processing this. Much of this time is due to me not being very familiar with what I was doing. I also prefer to process as manually as possible, and used no specialized plug-ins in Photoshop.
Prior to Photoshop, all of the data needs to be stacked in the computer by specialized software. I first tried to use Deep Sky Stacker (DSS) that I have used for this type of work before. However, I ran into problems. After loading all my lights and calibration frames the software refused to run and gave me typical ambiguous reasons. Doing some troubleshooting online it looks as though my data weren’t good enough – apparently my stars were not round or sharp enough and I could do nothing to get DSS to process my data. I then played around with a couple of other free astro-stacking softwares. Most of these were far too technical for me to easily learn them. I finally found Sequator and this worked great. It does not accept “bias” calibration frames, but I doubt that I could recognize their absence in the final product.
I then took the stacked image and went through the “stretching” process in Photoshop. This is where you increase the local contrasts, trying to bring out details in the arms of the galaxies, nebulosities, etc. There are a number of steps involved in this last bit of processing. Much of what I did I learned from Charles Braken’s book, The Deep-Sky Imaging Primer and YouTube videos from Nebula Photos, Peter Zelinka and others.
Conclusions and what I learned
I realize this type of image is built mostly by technology. There really is not much subjectivity when making images of deep-space objects. It either looks like the thing or it doesn’t. I also realize that there are people doing this that have much more appropriate equipment and knowledge and can produce a much better version of a DSO than I could no matter how much I practice. However, I have found it very rewarding to be able to produce an image of M31 myself, especially using camera equipment I already owned and use for other things.
Here are some things I believe I have learned and can potentially help me improve in my future attempts at making DSO images. If you are an experienced DSO imager and can offer any further suggestions, I would be very much appreciative!
Getting better polar alignment
Getting more practice should help here and I will try and do this on nights that I am not planning on shooting, potentially from my yard.
I have read and seen videos where people are suggesting upgrading the wedge mount and I will do this eventually.
Collecting more data
I believe I could pull more details from the galaxy’s disk, including colors by collecting more data. I was limited by clouds for this one, but next time I hope to get at least four hours. I know that some pool data collected from multiple nights, but that is another layer of complexity I probably do not need right now.
Finding darker skies
There is no doubt that skies with less light pollution will allow for better data collection at a faster rate. This will definitely help in pulling fine details and colors from DSO’s. There are light pollution filters, but I have heard mixed thoughts regarding their benefits.
Beware of dew
I knew this, but forgot to take the heating elements to wrap the lens barrel in order to prevent dew forming on the lens objective. Thankfully, the lens hood seemed to protect from this, but at the end of the night I did notice a thin haze of condensation on the lens.
Learn more on processing
There are numerous ways to skin this cat and I hope to learn more by watching more techniques on YouTube. With trial and error, I am certain that I can improve the final image by learning more here.
Other than the above, the only thing I can think of that would make a big difference is purchasing technology. People who really get into this use specialized telescopes, specially modified cameras, guided trackers run by computers, filters and much more. However, I do not intend to go down this road and believe I can produce images that will satisfy me with the equipment I already have.
If you have an interest in DSO photography and have the basic equipment, I urge you to give this a try. All you need is a camera and lens that is about 100 mm – 500 mm. A star tracker is definitely helpful but not required! You can shoot DSO’s with simply a tripod. Other than that you will need to learn just a few things on how to adjust the settings on your camera and where to point.
The NEOWISE Comet, whose actual name is C/2020 F3, was a pleasant surprise for the astronomical community who await such events as a newly discovered comet. First discovered in late March, the comet grew steadily brighter, eventually becoming the brightest comet to be seen in the northern hemisphere since Comet Hale-Bopp in 1997. According to the experts, this comet had an orbital period of about 4,400 years prior to making its latest trip through the inner solar system. It will now be another 6,700 years before beings on earth will be able to see it again.
I have long had a very strong interest in astronomy and astrophotography and the current pandemic has allowed me to do quite a bit of studying on both topics. Hopefully soon I can get the practice in this area that I desperately need. Although it has some issues, I was relatively pleased at capturing the closeup of the comet pictured above.
Although I had a star-tracking mount that would have been perfect for this situation, I had not yet used it so I did not make this the first time. This image was “untracked” using a full-frame camera and a 200 mm lens. It is comprised of 20 “light” images (the actual photos of the comet) taken at 3.2 seconds per exposure. The aperture was f/2.8 and the ISO/gain was 6400. I combined these images with 10 “dark” frames for noise reduction purposes.
The processing here could be better and I might give it another try sometime. But, both tails of the comet are visible and I think the background stars came out alright as well.
After awhile the comet began to dive towards the horizon with the remnant glow from twilight. I happened to show up at Lee’s Bluff on the same night as accomplished Missouri nightscape photographer, Dan Zarlenga, and so we both turned our tripods around to the south and found this lovely scene. Here, the Milky Way has recently risen above a nice foreground of trees. Again, I wish I would have been a bit more prepared with a plan, but I guess this isn’t too bad.