M31 is one of the most favoured and popular imaging targets in the night sky; it is bright, large and very photogenic. I have imaged this galaxy numerous times, for example, in this LRGB version and in this OSC version. Since the galaxy is so large, each of these images is set in a wide field, one of 3 degrees horizontally and 2 degrees vertically across the field of view which equates to six times the diameter of the full moon. Many newcomers do not appreciate how large these objects are in the sky. Large but VERY dim!
The above image is at a resolution of 4.16arcsec/pixel. On such a large object as M31 this allows the entire galaxy to be imaged in one field of view on a wide field refractor such as the FSQ85 but does not allow for a “closer in” and more detailed image.
In order to do the latter, I created a mosaic of four panels to image the right hand side “west” of the galaxy at the greater resolution with my TEC140 and Atik 460. All I needed is the luminance data and then I could use this to blend with the lower resolution OSC data at the top of this post in Photoshop.
Each of the four luminance panels is a total of 90 minutes of 300 sec exposures captured with the TEC140 and Atik460 CCD camera with a Astrodon luminance filter. The luminance image above is a total of six hours of imaging time. I then processed these four images and knitted them together in PixInsight. I then registered this four-panel luminance with the OSC data at the top of the post and then used it as a luminance layer to give the best of both worlds; the colour of the OSC/FSQ85 wide field image with the detail of the TEC140/Atik460 image!
I hope you like it! 🙂