stripes in DSLR images

[balt]

Hi all,

I took 26 3 minute exposures of M83 with a Nikon D300s, and no matter what I do when I combine the frames, I end up with what looks like a striation pattern going roughly NNE-SSW. It seems to reside chiefly in the noise. Does anyone have any idea how to get rid of that? At this stage, the image is still a 32bit FITS with no stretching applied (screenshot is from STF'd display).

Processing involved:
- batch converting .nef's to fits for dark frames
- integrate master dark
- calibrate (subtracting master dark)
- star align
- integrate all with average combination, multiplicative weighting with noise estimation.

And that's what I get at the end of that:



Does anyone have any ideas how to process the image from here? The colors look really wonk also...

Thanks for any illuminating hints. I'm just trial and erroring at this stage.

Cheers

- Balt

[pfile]

these kind of streaks are usually the result of 1) drift during image aquisition and 2) darks that don't exactly match.

now, the drift is kind of like a poor-man's dithering, which is good - the hot/warm pixels do not overlap each other. thus, you should be able to reject them while stacking.

try one of the sigma clipping modes to see if you can reject these pixels during stacking.

[troypiggo]

Looks like the result of flexure between the guide scope and imaging scope. How is your rig set up?

[Lex]

Hi,

I noticed the same problems with my 400Da, the reasons where flexure between main and guiding scope --> went to OAG;
On the other hand my Calib files where not proper --> took new ones 
Did you to first crop the image then Background Neut and after this Color Calib?