The Andromeda Galaxy
The Andromeda Galaxy is a widely popular, huge and gorgeous galaxy located in the constellation of Andromeda (no surprises there). I’ve imaged this galaxy three times now with a camera and a telescope, each time slowly improving. Admittedly there has been equipment improvements as well but also my own skills and abilities have improved alongside. In this post I’m going to describe the process of photographing a sensational Deep Sky Object.
The image contains 4.7 hours of 2 minute exposures using a Light Pollution Suppression Filter. A modest refracting telescope. An excellent astrophotography mount and a dedicated One Shot Colour (OSC) camera. There is certainly some expensive equipment in this rig and I had high hopes for being able to do this target justice.
As mentioned, the Andromeda galaxy is huge and located in the constellation of its namesake. There is a bright star nearby called Mirach which can be used to orientate yourself and find the galaxy.
Honestly when I was using a non-GoTo mount I always sort of struggled to find the galaxy. Even when using setting circles. Really Go-To absolutely assists when trying to find targets. But due to its size and brightness it shouldn’t be a difficult experience finding it in your finder scope. Viewing M31 visually is really amazing also once you do find it.
When I was getting round to imaging it this time, I not only used Go-To, but I used plate-solving. Plate-solving uses black magic to take a photo, assess where it is, and then sends adjustments to the mount to centre the co-ordinates in the camera’s field of view. I also used Stellarium to figure out my rotation and framing. From there, it was as simple as hitting Go-To++.
Photographing The Andromeda Galaxy
As mentioned above, I used a combination of camera, telescope, mount and a filter. The mount is pretty much the most important part as taking deep sky astrophotography involves following the night sky as it seems to move through the sky due to the rotation of Earth. It’s just another layer of complexity to the hobby. I have an entire breakdown of equipment needed for Deep-Sky Astrophotography on my channel.
- Sky-Watcher Evostar 80ED
- iOptron CEM70
- ZWO ASI 071mc Pro
- IDAS NGS1 Filter
- Astro-Essentials Mini Guide Scope
- ZWO ASI 120mm Guide Camera
Finding the correct exposure time is the ultimate question. It’s one that is always asked and wondered about. Whilst I have a lecture from Dr Glover of SharpCap which aims to help answer that question. I personally like a trial and error approach. I attempted 3 minute exposures, but trying to balance enough dust lane details as well as not overexposing the nucleus of the galaxy was the challenge. In the end I settled on 2 minute exposures, and just laying on the integration time.
I felt that 2 minutes gave me the right balance I wanted. It’s in the processing also that the dust lanes will be pulled out. The benefit of shorter exposures is less strain on the guiding system. You may not need guiding, but it also let me dither my data. The guiding solution was the Astro Essentials Mini Guider & ZWO ASI 120mm. Dithering data, in a nutshell, moves the telescope ever so slightly to break up noise patterns to get a cleaner final image.
When shooting in heavy light pollution, signal to noise ratio and separation from the background sky is always going to be an issue. Also the use of a light pollution filter doesn’t necessarily allow all the correct ratios of light through. What I found was my Andromeda galaxy image, as well as other galaxies I’ve shot, have a purple tint over them. The dust lanes can also be obscured by the pollution as well.
Dark skies are always a benefit, but I made the best out of what I could. Here’s what my image looked like before any attempts to colour correct for the filter’s colour tint.
The other way around this issue, especially with broadband targets in light pollution – and really for Andromeda – it’s to lay on the integration time. This was 4.7 hours but I will continue adding data to this image.
The Final Image
So as mentioned my final image of the Andromeda Galaxy is 4.7 hours of total integration time, using 2 minute sub exposures. I stacked the image in DeepSkyStacker and then edited it in Photoshop.
I’ll continue adding data I’m sure. But I also feel like I might experiment using no filters even in my city light pollution to see what sort of result I get. But here’s the image I have, and I hope you enjoy it. You can also watch the video behind the scenes.