Calibration Frames

Intro

Here’s a quick primer on how to take calibration frames. These are pretty easy to take and improve your image quite a bit.

Flats

Flats correct for dust on your optical train and vignetting from the telescope and your optics. Take about 25-30 of these. Ask around! Everyone does them differently… There are a few good methods to take them. An easy method for beginners is to move the telescope so it’s pointing at the zenith and then use a rubber band to secure a white t-shirt to the front of the telescope. Then, put a white image on your phone screen at max brightness and place it on the telescope. Keep the settings the same as when you took the light frames, but lower the exposure until the histogram fits in the middle.

If you took them correctly, your flat frame will look something like this:

Biases

These are quick and easy to take. don’t skip these. They correct for inherent sensor noise. You only have to take these once, and you can reuse them forever. Take about 50 biases. Take exposures at the fastest speed your shutter will go. For a DSLR that might be 1/4000, older DSLRs might be at 1/2000. For an astrocam it might be even faster.

Darks

These calibration frames correct for amp glow and hot/cold pixels. Dark frames are pure noise. Take about 30-50 darks. These might take you a while if your exposure time is longer. Shoot these before or after your session- make sure your camera has the same settings/ambient temp is the same

Extra frames:

Dark flats These are nice if you have filters and it’s fast to take these. It’s not really useful for DSLRs but it’s nice for astrocams. Same exposure length as the flats. measure dark current in the flat frame

Here’s Noah!