On my quest to make lamb out of mutton, I've embarked on making a decent flat set for my astro fest images. Last night I took the scope out and focused on Altair using the bahtinov mask and locked the focuser. This afternoon from 5 - 5:30 I went out and too a load of images with a t-shirt over the scope - and we had a thread recently about things neighbours get up to
So anyhow, I now have over 200 frames from which to make a flat set to go with my lights and darks (I appreciate it would be an ideal match because of the time differential). I programmed the camera to take sets of 25 shots which me whisking the scope around in between each frame so as to get seemingly random bits of sky. For each set, I had pointed the scope east and above the trees and set the exposure so that the histogram on the camera was in the 2nd quadrant (between 25 and 50%).
As a result if the fading light, the exposure length was increased as time went by. There is also some variation in the histogram of the images due to my "random" whisking often (maybe 25-30%) catching an area of the sky with a tree in it (there's a kit of those around here
)
So now...I have all these images, how best to select a good set?
- Random pic from set of he same exposure length
- I've read a couple of pages that talk about median pixel values, so a bunch of images with similar values? (regardless of exposure length?)
- Or...???
Or am I doomed?
