Markarian’s Chain (NGC 4406)
Since I picked up astrophotography, I knew I wanted to shoot some galaxy clusters. The first that comes to mind is Markarian’s Chain, a nice curved line of galaxies that lies amidst a large cluster of galaxies known as the Virgo Galaxy Cluster. The Virgo Cluster contains up to 2,000 different galaxies and Markarian’s Chain is an asterism-like chain that provides an interesting order to the randomness of the surrounding cluster. Typically, Markarian’s Chain is considered to be comprised of seven galaxies, all of which are moving in the same relative speed and direction with one another. The distance from earth to the galaxies varies from between 50 -80 million light years! Of course this means we are seeing them where they were up to 80 million years ago.
The galaxies comprising NGC 4406 are mostly elliptical and lenticular in type, but there are some fascinating details that can be found by taking a closer look. I’ve left the image above a bit larger than normal and invite the viewer to search within to see some of the different shapes and go galaxy hunting if you would like. I have counted about 35 galaxies in this frame. Most are quite small. Remember, if it’s a little fuzzy, it’s a galaxy. The stars are typically sharp in contrast to the dark background void.
Let’s take a look at some of the galaxies making up this frame. First, the two larger appearing galaxies that anchor the chain are M84 and M86. Just to the left of these are two interacting galaxies, NGC 4438 and NGC 4435, known collectively as ‘Markarian’s Eyes.’ I was happy to pick up enough detail to show how NGC 4438 is being distorted by the gravitational pull of it’s neighbor, sweeping out a lot of the gas, dust and likely stars from their normal placement.
Another prominent galaxy in this frame is found in the lower left corner. This is the supergiant elliptical galaxy, M87 (Virgo A, NGC 4486). M87 is one of the largest and most massive galaxies in our local universe, containing several trillion stars.
One last galaxy to bring your attention to is NGC 4440. This is an interesting barred spiral galaxy that I was not expecting to see in such detail. This galaxy is located at the intersection of two lines in this frame. Draw a line going directly downward from the eyes and another starting at Virgo A going to the right. Where these two lines intersect you will be close to NGC 4440.
See the accompanying partially-annotated image showing the names of the more prominent galaxies in this frame.
Collecting the data
I have made my bed as an astrophotographer that does not use “go-to” technology and I am frustratingly sleeping in it. This one should have been easier to find. It is literally between two mid-magnitude stars – Denebola, in the Leo constellation and Vindemiatrix in the constellation of Virgo. All I had to do is draw a line between the two and the target is in the dead center. Somehow, I did not take this literally enough and spent nearly an hour finding the target and composing the frame. I do have one excuse; this area is filled with galaxies, so every time I took a test shot, there were several galaxies in the frame and it took me some time to see if the pattern I was looking for was there or not. Other than this, the night went pretty easy. We had perfectly clear skies, cold temps and Miguel and I had extra company. We joined with an imaging party from the Astronomical Society of Eastern Missouri, who just happened to be at Danville C.A. the same night we were. It was fun watching the experienced imagers and viewers pulling out all sorts of big, pretty and expensive optics and mounts. Unfortunately, between trying to concentrate on what I was doing and the very cold temperature, I didn’t find the time to do much socializing.
Date and location
Imaged on the night of 19/20 March 2023 at Danville Conservation Area in Montgomery County, Missouri (Bortle 4).
Dark period: 20:45 – 05:42
Target period: 19:52 – 07:31; Zenith 01:42
Clear skies over the course of the session. Temperature in the mid 20’s F. Winds below 5 mph.
Astro-modified Canon 7D mkii camera, Canon 400mm do mkii 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.
Lights taken (ISO 6400, f/4.0, 20 second exposure): 1,076
Lights after cull due to tracker error, wind, bumps, etc.: 912
Used best 90% of remaining frames for stack for a total of 821 subs used for integration (4.56 hours)
Darks: 36 taken at same exposure time and ISO as lights
RAW files converted to TIF in Canon DPP, stacked in Astro Pixel Processor, GraXpert for gradient removal, Photoshop CS6 for stretching and other cosmetic adjustments.
Problems and learnings
Miguel had to save my bacon with this one. This was the “first light” for astrophotography for my Canon 400mm f/4 do mkii lens. I had been eagerly waiting to try this lens for this purpose and, as I feared, this longer focal length did not allow for the 30 second exposures I had gotten used to using the 300mm lens. Even though this combination was a bit lighter than the 300mm f/2.8 lens, the Star Adventurer tracker just wasn’t up to it. So, I was forced to go with 20 second exposures to limit star trailing and, consequentially, had to use ISO 6400 to keep the signal to noise ratio where I needed it. This ISO setting is really pushing it with the camera I use so I wasn’t at all sure that I would even have a final image worth sharing in the end.
Because I pushed the ISO, the noise was pretty awful. Following a very light stretch after stacking, huge bands of green and purple showed up against the dark sky. I was at a loss on what to do about this, having exhausted all of the tools I knew to use in my processing train. I knew Miguel was beginning to become quite proficient in PixInsight processing so I thought I would ask him to try and see what he could do with my stacked image. I was dumbfounded when he was able to fix my problem in about 10 minutes! The final image could still probably be stretched a little more to bring out further details, but considering the ISO I was using, I have to be satisfied with the end result. I can’t get myself to put down the purchase price for PixInsight anytime soon, but that is something I’ll be considering in the future.
Spring is known as galaxy season in the astronomy world. Most of the popular nebulas are not as available as they are in the winter and summer. Unfortunately, I really don’t have the equipment to take closeups of the far off and very small galaxies so I will have to settle for a few of the relatively larger ones as well as the clusters like Markarian’s Chain. I am pleased with what I was able to create here. As usual, it was with some considerable struggles and frustrations but I am coming to find that I kind of like overcoming those obstacles despite what I feel at the time.
One thought on “Markarian’s Chain – NGC 4406 (March, 2023)”
That is another excellent write-up, Bill. I enjoyed reading the workflow. Your patience with the process was rewarded.