The Andromeda Galaxy is a close galactic neighbor. M31 is large and bright and can be spotted with the naked eye from even a moderately dark location.
This image was taken over three nights from a friends cabin located about 45 minutes east of the city. Its not really "dark-sky", on the light pollution map it shows as yellow. Still, it’s a lot better than my back yard and I can leave the gear set up there for days at a time which really helps for multi-night imaging runs.
This is my longest run for a single image so far. The total exposure time was over 12 hours of which about 7 hours worth was actually useable. The sub-frames are a variety of exposures ranging from 4 to 15 minutes each. Below is a list of the exact exposure times per filter:
Lum: 9x4m + 5x5m = 36m + 25m = 61m
Red: 9x4m + 5x5m = 36m + 25m = 61m
Green: 9x4m + 5x5m = 36m + 25m = 61m
Blue: 9x4m + 12x8m = 36m + 96m = 132m
Ha: 6x10m + 4x15m = 60m + 60m = 120m
Total: 435m (7hr, 15m)
This untidy set of frames was not by design. What actually happened was after each session I would process the images and see how things turned out. Then, for the next session I'd make some changes to see if it would improve things. One issue was a distinct lack of blue. This was remedied by adding in a bunch of 8 minute blue exposures (as compared to 4 and 5 minutes on the red and green). The H-alpha time was also lengthened from 10 minutes to 15 minutes to help bring out the Ha regions of the galaxy.
Another problem was the focus changing during the night due to falling temperatures. Cold causes the telescope to physically shrink a bit which can move it off the best focus point. One night it happened quickly and changed enough that an entire run was lost. After that one I started checking the focus every hour or so and adjusted as needed. This really cut into my sleep, but it worked. I have since bought a motorized focuser system with a temperature probe and can hopefully automate this process. But until then, regular focus checks are in order when the temperature is dropping.
On the plus side, the Ha filter really brought out a number of fairly intense Ha regions. They show up as bright red patches, mostly along the edges of the galaxy. Even some distance from the main galaxy there are Ha regions showing up. Kind of cool to be imaging nebula in another galaxy even if they are just faint fuzzy blobs from where we sit.
This one was difficult to process. The Ha frames affected the red levels and the oddball mix of LRGB exposure times (expecially the blue) made the white balancing a bit of work. Moving the camera meant that the images were rotated a bit differently each night which led to uneven banding around the edges. Even the aurora got in on the act with its random green flicker tricks.
But you know, thats all part of the challenge: take less than perfect data and still come up with a pretty picture. In the end it took over 30 hours of trial and error processing but it worked. So, no its not the best M31 ever, not by a long shot. But it is my best M31 and it shows well even when compared to some of the better I've see on the net.
It’s the ones like this that make your forget about the cold and the dew and the price of gas and the time and effort hauling heavy gear then setting up in the dark in the middle of nowhere and staying all night all by yourself with just the coyotes, bats and porcupines for company. (ok, some of that is actually kinda cool but anyway) Yes, its all worth for one of these.