Quote:
Originally Posted by Eric Hahl
I got outside last night and shot the North American and Pelican nebula's in Cygnus. 4.4 hours worth of exposures. Messed up the flat field images I took for calibration so didn't include any in this picture. They sure would have helped. I've got a weird color gradient I don't care for. Oh well, chaulk it up to learning.
https://cdn.astrobin.com/thumbs/YwAtyx8kmoAS_1824x0_wmhqkGbg.jpg |
I'll say two things...
The only time I saw variation like that (top to bottom symmetrically) was electronic heat along the "reading" side of a parallel CCD. Not a serial CCD, which reads row after row then shifts the register down, since that creates corner heat. Parallel read CCDs read each column at the same time, so the read noise is across one edge. It's not optical, clearly. That was old school mono CCDs, I have no idea how modern full color CCD/CMOS chips work. Maybe they're all parallel now.
You over processed, you made halos around the stars in the nebula. Now, if you go back and look at my old images, I generally did the same thing and was fine with it, but since you're now vanguarding the imaging in this thread, we're all looking to you to BE PERFECT.
Edit: It sickens me to to see what some freaking amateur can do these days with 4 hours of imaging. All those hours I spent guiding by hand in a reticle eyepiece, eyes fogging over because you're hunched over cutting off the blood to your brain, then taking that roll of film to the only shop in town that won't destroy your images, only to find out that your guide camera was out of balance and slumping during the run, and your image was ruined. We EARNED our bad images back then!
