Night Sky Image Stacking
I used to take alot of single exposure images of the night sky. They would come out really cool looking but always looking a good bit too busy when zoomed in. Now while this would be ok for a small screen like a cell phone, I wasnt happy. There had to be a way to get rid of the excessive noise from high ISO. With just a camera on a tripod your limited on exposure length. With a wide angle the best I could do was 30 seconds without getting noticeable star trailing. So naturally I thought maybe if I could just get a longer exposure at a lower ISO it would work. So I bought an iOptron sky tracker off Amazon. I managed to get it all the way up to 1.5 minutes at ISO 400. Yet still when pushing the details in RAW I would get a lot of white noise in the shadows.
As you can see above, it looks like a ton of stars. Well it is and it isnt. Come to find out, with long exposure comes distortion in the image. From image sensor heat and noise. So some very smart people came up with the method of taking dark frames. You take one light one, of your exposed image. and then one with the exact same settings with the lens cap on. Subtract the dark frame from the light frame and you have a noise and error free image! Absolutely genius. Take a closer look at the details below
Theres a good bit more clarity and a good bit less noise. Especially in the color ranges. So now, how the heck do you accomplish this?! I used a iOptron Sky Tracker. You can buy one from Amazon by clicking HERE. Having this is essential to making exposures in excess of 30 minutes. Youll also need it if you use long lenses upwards of 200mm. Overall its really the only thing you need to add to your kit to keep yourself busy photographing deep sky objects for years to come. Setting it up is a breeze. Point it towards north using the compass on the top of the tracker. Then use their handy app to tilt it up towards polaris. Then fine tune with the scope! If you get a really good alignment you can push your exposure times significantly. I usually recheck the alignment after moving the camera. You’ll also need a decent tripod. I use a Polaroid carbon tripod with removable ballhead. Which you can buy HERE.
Now on to the picture taking part! I trust you already know how to find a dark sky and the right timing to take milky way or deep space pictures. If not then you need to check out my other tutorial on how and where to even take these pictures! Click HERE, and then come back to this one once your done.
So your all setup, you have your dark location on a moonless night. Skytracker aligned with Polaris (north star) and aimed at what your hoping to get a cool picture of. Well need to take a series of images. Lights, Darks, and Bias frames. The lights are the ones with the optical data. Take these at 1600ISO, widest aperture, and around 10 seconds exposure. Take lots of them. At least 50. Then put the lens cap back on and take 25 more. These will be the Darks. These frames will cancel out the noise from ISO and sensor heat. Then set your shutter speed as fast as it will go and take 25 more. These are the bias frames. Supposedly these are to clean the image of sensor signals. Either way, you will end up with a fantastically clean image. At the end of each sequence of shots. I take a picture of my phone screen as a break point so its easier to figure out where one sequence ends and another begins.
Next up youll need to put all this data into a program. I use the free software called DeepSkyStacker. You can download it for free from their website! Click HERE to get it. Now in the interest in not reinventing the wheel I’ll refer you all to a video I found on youtube. This guy does a fantastic job of explaining everything I did above and also the step by step on how to use the program.
With the help of this video I managed some decent results on my first attempt at this.
Sony a7ii / 28mm f2 / ISO1600 / 10 Light frames / 5 dark / 5 bias/
Sony a7ii / Pentax 300mm f4 / ISO1600 / 12 light frames / 5 dark frames / 5 bias frames.astrophotography, editing, educate, help, image stacking, jamesfleishelphotography, learn, night sky, Photography, tutorial