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.
Sarah and I traditionally conduct a caterpillar hunt on the weekend of her birthday in mid-September and 2022 was no different. This year we headed to Meramec State Park. I had recently heard of a short trail that covered the lush river bottom and contained hundreds of pawpaw trees. My hope was to find caterpillars of zebra longwing butterflies – a cat that has been elusive despite my many attempts at finding a late instar to photograph. We wound up short of this goal again, but we did find quite a few interesting species. I know Sarah will want me to mention that she did indeed win the day by finding more cats than I did. 🙂
Late last summer I had the great pleasure of attending my first couple of field trips with the St. Louis chapter of the North American Butterfly Association. Both of these walks were led by my friend, Yvonne Homeyer, the St. Louis chapter President. Yvonne is not only skilled and knowledgeable with butterflies but is an expert birder as well. These walks were held at Marais Temps Clair Conservation Area in St. Charles County, MO. I was thrilled to be able to get a number of first photographs of some fantastic species and was happy to do so while on a walk in good weather among friends. Thanks to all the participants who patiently helped me locate these insects and get the photos!
Many thanks to Chris Brown and his family! They had the incredible fortune of having a Mississippi Kite nest in their front yard this summer. The nest wasn’t really viewable from their house but with great luck, the chick after having left the nest, picked a branch right outside Chris’s son’s window to sit and wait for the parents to bring in food. At this point Chris invited me over on a couple of occasions to watch and photograph. Thanks for the use of your room, Avery! Unfortunately, these couple of days I began coming down with Covid-19 symptoms, inadvertently exposing the Browns and cutting off my time there. Thankfully, none of them picked it up during my visits. Here are some of my favorites of the parents bringing in cicadas and dragonflies.
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! 😉