Second light self modded 1100D

[MarcoS]

Good day,

This is the second set images taken with my modded 1100D that I try to post process in StarTools, and the troubles are not jet over....

in the first set I had problems with flats, I could solve those a bit, with the help of Ivo and Rowland.
this is the link to that tread:
http://www.startools.org/forum/viewtopic.php?f=10&t=644

I tried the Calibration method with AstroArt as suggested by Rowland, but unfortunately the program keep crashing on me so no joy there.

I was successful in getting rid of the banding by increased the Dithering distance in APT, and that problem was solved.

The problem that I'm facing now is that in my image (around its center) there is an huge amount of red, were there should be none, (at lest in other images on the net that area is darker).

This image is the result of 74 x 180sec ISO 1600 light frames, with darks flats and bias.
Stacked in DSS;

I have also tried to re stack the images, letting DSS align the color channel, but it did not help,
If I try to reduce the reds in the color module, I just loose all of it....
I just loose control of the colors.
The work flow I use is a typical one, very similar to the one posted in the tread of the link above.
I think I have to relearn StarTools, because all the workflow I was using before the modding it is not working anymore

Those are two versions of the resulting image:

Autosave004.jpg (71.08 KiB) Viewed 4021 times

HorseHead-003-crop.jpg (96.37 KiB) Viewed 4021 times

And this is the link to the stack:
https://drive.google.com/file/d/0B6oGP3 ... sp=sharing

I do I get rid of all that red in the center?

Thanks and best regards

[admin]

Hi Marco, sorry for the delay in response (the Holiday period is alway very busy).

The problem appears to be some sort of problem with your flats (it's all I can think of anyway). Looking at the data, it appears it is suffering from severe vignetting and/or possible incorrect application of flats.
How does your data/processing look if you stack it without flats?

[MarcoS]

Hi Ivo,
No problem & merry Christmas and New year

I did another stack without flats and it looks horrible, I redid then another stack with an other set of flats taken with the T-shirt method, and It looks a little bit better, but not much.
I also triyed a stack with DSS set to auto-WB and it was e little better .

On the Astronomy-forums members suggested that those rings anomalies could be caused by local stray light infiltrating in the system.
The view finder of the EOS was not covered during imagining, and there was a small 25w light on about 5mt behind a glass door inside the livingroom...
And yesterday while dismounting for cleaning the microfocuser/focalreducer/derotator assembly I noticed that there were some little 'steps' between the adapters that could couse unwanted reflections. I have now flocked that area.

Next clear skies I will try an other stack and hopefully will be better....

[admin]

Great to hear you've found some possible culprits. Your data looks very nice and deep otherwise. Good luck next session!