![image showing 1 vs 3000: I couldn't afford a Telescope or a Tracker, so I spent 3 nights taking over 3000 Exposures of the Andromeda Galaxy using just an entry-level camera from a fairly light polluted city in Central India. Merged them together using a technique called "Stacking", and this is the result[OC]](67b4ccea-c726-5280-b9c6-70bebfcd3a34.jpg)
1 vs 3000: I couldn't afford a Telescope or a Tracker, so I spent 3 nights taking over 3000 Exposures of the Andromeda Galaxy using just an entry-level camera from a fairly light polluted city in Central India. Merged them together using a technique called "Stacking", and this is the result[OC]
vpsj on November 1st, 2020 at 00:02 UTC »
Details:
Left is a Single exposure straight out of the camera on how the sky(and particularly the galaxy) looked. Right is what I got after stacking 3000+ frames of the Galaxy.
Andromeda Galaxy is about 2.5 Million Light Years away from us. Normally, you'd photograph a subject like this using a motorized tracking mount or at least going to a darker area. I couldn't afford either of those things(the latter due to the current pandemic) so I just took all these shots from my roof instead. I know that some other shots you may have seen of M31 are probably way better than this, but the fact that I could even get Andromeda even from a Bortle Class 6 sky was enough for me.
If you like this shot, you can check out my other work on my insta @astronot_yet . I do Astrophotography with a cheap/affordable camera and try to demonstrate that beautiful night sky shots are possible even without driving hundreds of miles to a forest or to spend your entire month's salary on buying expensive gear.
TIP:If you don't like to read huge wall of texts, I would recommend watching 'Nebula Photos' on YouTube instead. He has a series on Andromeda without a tracker and it's absolutely the most comprehensive and detailed guide I have ever seen.
What is Stacking?Stacking means taking lots of images of the same subject, align them together and take an average of all the frames. This increases the Signal to Noise Ratio(SNR) of the image and reduces the random noise that creeps up in your photos. Bottom line: You can get really high details by stacking multiple images than using just one image.
Equipment-Nikon D3100, Nikkor 70-300mm telephoto lens, a cheap tripod, a wired remote shutter(optional)
EXIF:155mm, F/4.5, ISO 12800, 2sx3084 exposures
Process:1) Getting the focus right is the single biggest challenge while shooting dim objects like these, so I spent a considerable time fine tuning the focus to get it as sharp as possible.
2) Next, we need to locate the Andromeda Galaxy. The best way is to download any star chart app, and use the Augmented Reality feature that most of them have these days. I used this but you can use your own favorite.
3) Point your camera roughly between the constellation Cassiopeia and the star Mirach. M31 should be just a little below Mirach.
4) A remote shutter or intervaloemter is advised to avoid touching the camera again and again and minimize blurriness/disturbance. You can buy a cheap wired remote, or if your camera is fairly new it may already have an intervaloemeter built in. If neither of these are possible, just put your camera in a 2s delay timer and you'll essentially achieve the same result.
5) How to select your exposure length: If you set your camera's shutter duration for let's say 15-20s or something, what you will see are star trails where instead of pin pointed stars, you'd see them moving in a line, ruining our shot. In order to get sharp looking stars, we use the rule of 500 which is essentially
Take a shot, zoom in and check the stars, if you see some trailing, lower your shutter length and test again. For my case, Nikon cameras have a crop factor of 1.5, so at the focal length of 155mm, Rule of 500 gave me 500/(155x1.5)= ~2s.
6) Take as many exposures as you can. If you're already in a darker area, 1000 exposures would be good enough. DO NOT change any settings in between the exposures. It's a good idea to not disturb the camera at all while it's taking the shots.
7) Take a few bias, dark and flat frames. These are called "Calibration Frames" and their job is to remove any noise that is being generated by the Camera itself(Heat, dust on the sensor, etc). How to take these here
8) After all this, you can use any stacking software to process these shots. My favorite is Deep Sky Stacker and Sequator. Pixinsight is also a capable one, but it's not free so pick whichever one you like. The main job of stacking software is to align all the exposures and then sort of take an average of the frames which decreases noise and increases the Signal to Noise ratio of our image, so the final shot results in extremely high details and very less noise.
9) I processed the result in Pixinsight, and retouched it a bit in Lightroom.
Please note that this is a very simple explanation, and some of the rules and technologies I wrote above might have mistakes, or may not work in your case. Please remember, experiment and experience will give you the best results. Also, if I indeed made some mistakes above, please correct me.
Ask me if you guys have any other questions :)
EatMoreHummous on November 1st, 2020 at 01:44 UTC »
The biggest takeaway for me from this is just how much the night sky gets blocked by city light.
Compared to the 3k images merged together, I've had clearer views in one go from rural US, not to mention somewhere like the Atacama Desert.
aatdalt on November 1st, 2020 at 02:16 UTC »
As one of those guys with all the expensive gear, I just want to say this is really impressive and well done. Good write up too. Hope to see you get to keep at it! A simple star tracker is going to make an unbelievable difference for you (mostly in the reduced headache of stacking 3000 subs).