Pixinsight users,
I pulled ~2hrs worth of exp with ISO 800 with 4 min subs, NGC7023 the other night in LP skies. It certainly needs more exp time.
But, my issues I am seeing are , excessive noise I did not see in my other images while using the LP filter, with the same setup, and the color calibration in processing I have seen since adding the LP filter..
I bought a IDAS LP filter, which lets me take the 4 min exp without saturating in my LP skies, (could go longer, but having issues with guiding), but I noticed that the Red is less on the histogram, and seems to cause color balance issues. This is of course in the flats as well.
1st issue is with the flats: These are sky flats of <1sec.
My flats are very unbalanced. With the OSC DSLR, my previous sky flats without the IDAS filter showed the red lower but not real low compared to the Green and Blue. The IDAS is really knocking the red down.
Messing around I found the I could debayer the master flat, take it into HTT, and balance the colors. Then use the new "balanced" master flat to calaibrate the lights again. Following this thread, there are obviously other ways to do this.
After doing so I was able to do the processing much easier.
But it made the Red higher than the Blue or Green.
I have put the main light image in a dropbox folder if anyone wants to help with this.
Both with and without calibration from balanced flat master. light-base_2.fit is the balanced light.
https://www.dropbox.com/sh/t6iiqzh1xlupjmg/kVHaANs2t-?mIn the doc ( named HTT.xxx) you can see my original and balanced flat. ( bottom)
Also In the doc (from the top)I have shown snapshots of the images and what the HTT looks like for the color balancing after (crop,DBE), then background Neutralization, and then after Color calibration.
I wanted to know if the differences in the RED value is suppose to change like it did.
I don't know if this balancing of the flat master was a good idea, but seems to work. I saw some weirdnesses, so I am just asking.
And also put the flat masters from the original and the balanced flat in the dropbox. (debayer_flat-BINNING_1_hist) is the balanced flat.
After using the balanced flat, the light frame did not look any different with an initial unlinked STF stretch, but with the linked STF it went from RED to GREEN. But it sure did act differently when processing. The light frame calibrated with the balanced flat was much easier to process.
I feel the calibrated light is just to bright when using a simple STF stretch.I can do lot with it with PI, but I think I might be starting out with an improperly balanced image.
As a side: I read something from Rob about using a red or pink T-shirt to try to bring out more Red for the flats. I might try that.
P.S Except for weekends, my sky flat days are over for awhile now. Daylight saving time has expired.
I need to find another way to get flats now.
Scott
