M31, more from Cherry Springs

I really should have spent more time per image, but I was so intoxicated with the dark skies that I jumped from object to object. My “neighbors” for the week were Bruce and Jill with Bruce being the imager, and he tended to do imaging of no more than two objects each night. But the first night I kind of went crazy and skipped around.

Even so, this image of M31 is definitely way better than what I did a decade ago from Missouri. Total exposure here is a mere 1 hour (20 x 180 sec). In this scaled down image, the noise is not apparent, but this could have used a lot more exposure time. I hope to go back and try again now that it’s coming up a bit earlier so maybe I can spend most of a night on it.

I have to think that I don’t quite understand yet how to do proper calibration in PixInsight (well, that’s at least partially self evident in that I used PWP8 to do additional tweaking). Most images of M31 show a clear bluish tint on the outer parts of the disk, as you see in this. But the initial image when I finishing calibrations and stacking is a pretty uniform yellowish, except for that bright star in the left center (nu Andromedae, a binary composed of a luminous B5 and an F8). It took a lot of work to bring out the bluish tint. My 2009 image was not calibrated at all, and it used a different camera (a modified Canon XTi/350D with a Borg 45ED for the scope, similar focal length), but it showed a bluish/greenish tint to the disk without much work at all.