Having huge problems with processing (Ursa Major)

[tcln1456]

I just got PI two days ago, so please bear with me if I did something wrong 

I'm processing the Big Dipper here in DC, and I always get stuck after using the DBE, because I still have noticeable gradients. When I use a low tolerance (.1) my post-DBE looks like the original, and when I use a high tolerance (.9) there's far too much noise in the image. I tried to use the normalize for the Target Image Correction, but all that did was turn the gradient blue.

I'm stacking in PI with BatchPreprocessing with master bias and darks created in Image Integration. This is what two different takes of DBE looked like (http://imgur.com/ztWdP3P)

Also, a general question. When auto-stretching with the STF, is it recommended to unlink and auto-stretch, or link, auto-stretch, remove green with SCNR, Canon banding reduction, then auto-stretch?

I've been watching both Harry's videos from Harry's Astro Shed and Jason Brown's M33 tutorial.

[Josh Lake]

Hello again, good to see you here!

SCNR will really only work when you go non-linear using Histrogram Transformation.

In the early steps of seeing what you have, I recommend:

1. Auto stretch STF (which will be a very strong stretch in your case) with UNlinked color channels

2. Link color channels

3. Bring up the midtones slider to darken the background

4. Do other steps in linear space -- background neutralization and color calibration, maybe noise reduction with Atrous Wavelets (a la Harry's video)

5. Apply the screen stretch that you're happy with to the Histogram Transformation function by dragging the little triangle of STF to the bottom bar of Histogram Trans, and apply the HT

6. Reset the STF so you're not 'doubly stretched'

[Harry page]

Hi

Cant see why dbe wont work , can you upload a file to me to look at 

Harry

[tcln1456]

Hi

Cant see why dbe wont work , can you upload a file to me to look at 

Harry

Here's the file: https://www.dropbox.com/sh/fi4xt7zsb2n275i/D1vHB99Uh3

Josh, I'll try that out and I'll let you know how it goes.

[Harry page]

Hi

A few comments to start with 

1) You are removing to many pixels in the intergration try increasing the sigma setting
2) you have some kind of light leak/local light ingress / bad subs which need removing from the stack ( you can see the light shadows)
3) Focus is a long way off , need to spend a bit more time on this
4) there seems to be a large rotation during capture , better polar alignment would help
5) crop your image to remove defects before DBE
6) flats would be a great help 

I attach a pic showing my setting , to get you somewhere near , and I have autostretched everything , but this is too aggressive on the final image
you will need to stretch less  8)

Regards

Harry

[tcln1456]

1) I'll increase the sigma setting next time I stack. Would you recommend something like 4.5 low 4 high?
2) That's probably my neighbor's streetlight. I'll dig through some older files when it was turned off
3) How would you recommend adjusting the focus? I usually take a sample exposure and import it to my computer, zoom in to check, then adjust it on my camera. I usually perform around 7 iterations of this, but is there an easier method?
4) I never actually looked into polar alignment. I just kind of plop my tripod down and go. I'll do that next time.
5) Will do
6) Do you have to take flats after every session, or can I just take one set of them and use them for all my stacking?

I fiddled around some more with midtones and color calibration + ATrousWavelet Transform and ended up with this: http://imgur.com/DT9EJxv

My only complaint is that all my stars are blue now.

[Harry page]

Hi

With focus perhapes a Bahtinov Focus Mask would help if you are having difficulty on this , and flats are needed for every time you adjust anything ( rotataion, focus, etc) just something you will learn to do 

Have a look at the histogram to see if you have good balance ( i.e do the peaks line up )

Lastley say try sigma 5 high , but only with checking of the masks can you get this right

Regards

Harry

[Harry page]

Hi

Did a quick process - crop-dbe-cc-stretch-noise reduction-star reduction-colour sat 

There is some colour to play with

Harry

[tcln1456]

Josh and Harry, I present, my attempt with incorporating both of your advice.

I'm not too good with bringing out the color with color saturation, but I don't think it's that bad for a first shot.
The first attachment is the same file, whereas the second attachment an attempt at processing data from another session.

How did I do?

http://i.imgur.com/KaFrps5.jpg

http://i.imgur.com/m7wvIvI.jpg

Unfortunately, I didn't have time to apply a Bahtinov focus mask, because I need a little break from sitting at my computer, but I'll try to shoot with a better focus next time.