Comparison between observations of M31

I recently obtained a new image of the Andromeda galaxy (M31) using my recently acquired Dwarf 3 smartscope and I always find it interesting to compare newer observations with those I have obtained in the past. Here is that image again which is based on 2 hours and 4 minutes (536x15s) of integration:-

Here is another image that I took using my Celestron NexStar 102SLT back on the 23rd September 2016:-

I have rotated this image, resized and cropped it so that it matches the one above. This image is 8 minutes of exposure (16x30s) using a Nikon D90 at ISO 3200. To get to the same exposure on the Dwarf 3 (which has an aperture of 35mm) I would have needed (102/35)² x 480 seconds or approximately 1 hour 8 minutes (all other things being equal). So the new image with the Dwarf 3 should be much deeper. 

Comparing the two images it is obvious that I seem to have got the focusing slightly wrong on the older image as evidenced by the pink halos around the stars (this was always a problem with the NexStar). I also seem to have obtained a reddish colour cast. Looking at the images at a 100% there is a lot more noise on the older image as expected and the brighter stars are not so sharp. Also, in the new image the blue star formation areas in the outer fringes of the galaxy are much better defined and do show up as blue in colour. As I said before, I think a lot of this is due to the very good post processing in the dwarf. 

Here are the two crops of the Dwarf Images, one before processing and one after, as before, and for comparison a crop of the same part of the image I took back in 2016:-

 

I think a lot of the gain in image quality from the Dwarf is coming from the post processing.

All text and images © Duncan Hale-Sutton 2025