When I started to get more serious about astrophotography I often thought about how exciting it would be to actually work with someone to create an image that is better than what one could produce on their own. Astrophotographers are faced with limitations that are unique to their location, equipment and skill. Working together with someone seems to be a good way to overcome those challenges.
On Friday, October 25th I will be doing a talk at the Mississauga RASC on this subject in more detail. In the process of getting my act together, so to speak, I realized that I should actually hunker down and complete one of the collaborations that I started back in 2009 with my good friend Stefano Cancelli of astrogarage.com. We were both imaging M31 around the same time and we felt that if we combined data sets we would get a better final image. We both were not happy with the results in some way or another and it was put on the back burner for a few years. Recently I decided to revisit this with some much needed final tweeks. We went back and forth on the adjustments a few times and finally came to agree on a final version that we both loved. First, I'll share the background and some snaps of the process along the way.
Living in Toronto, Stef has a major challenge with light pollution but with a great setup and his skill in post processing, he was able to bring a high resolution 3-panel luminance image of the core of M31 to the collaboration. Stef used a Vixen VC200L telescope and an SBIG ST10XME cooled mono-chip camera. On the other hand, I have darker skies since I am living in the Niagara region and therefore have an easier time collecting data with colour. I also love working with colour. My setup gives me a bigger field of view but a lower resolution. I used a QHY-8 camera (which is a super cooled APS-C sized one shot colour Sony chip) and an Astro Tech 8 inch Ritchey Chretien telescope with a focal length around 1100 mm (with a focal reducer).
This is what the stacked tiff file from my contribution looked like straight out of a program called Deep Sky Stacker. When you bring that tiff file into Photoshop it really looks disappointing - but not to worry. This is why we have programs for post processing.
The tiff holds all the information that is needed. Below is the image after a few careful curves stretches.
Continuing with the multiple curve stretches in Photoshop this is what you get. I also always make some adjustments to the gradients and colour balance as well if needed. When it comes to colour balance, if you can see a reasonable distribution of orange, yellow, white and blue stars then you are probably in the ball park and your target colours should also fall into line. If you have green or purple ones you know you still have to make some adjustments.
This is Stefano's contribution. He transferred this to me so that I could add it to my colour version...
...but unfortunately I had to do some cropping, rotating and transforming in Photoshop to get it all lined up with mine.
In Photoshop, I added his mono image as a luminance layer so that the colour comes through and his details and smoother results remain intact.
Adding in some clipping curve masks you can seamlessly blend the two. Finally after sharpening, noise and colour tweeking and lots of back and forths we came to this final result that we are both very happy with. Being able to capture something like this from the most populated and light polluted part of Canada is very rewarding.