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Aidan, the most important thing with taking flats is that you leave the system as it was when you took the light frames, and to take them as soon as practicle after the images. What I mean by that is as long as you haven't moved your focuser or rotated your camera, or added any extra filters or anything into the image train you can take them anytime. I like to take them as soon as is possible after the image frames, and I don't have a light box, so what I do is similar to what most people call T'shirt flats. I have a piece of white material that I keep clean, wrinkle free and a strip of elastic. I like to take my flats after the light frames because that ensures that any dew droplets or smudges of dust that appeared during the night will be included in your flats. The early morning after an imaging session, about 5.30 or so, so that the sky is starting to lighten up, I park my scope, which for me is pointed at the SCP, cover the scope end with my material using the elastic around the end of the scope to make sure no wrinkles are in it as they will show up in the flats. I use the same ISO as my images and put the camera into AV mode and take 50 to 100 shots. They are normally less than a second duration each so they don't take long, and that's it. That's all I do. The only suggestion that I have would be make sure the material you use has a very fine weave or else the weave can put a pattern in your flats. I tried t'shirts and many other different types of material that added the pattern, so didn't work. What I ended up using is an old cotton sheet that we had. Works a treat, and like I said makes a big difference. Good luck and let us know how you go.
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