Processing Assistance

[Sarge]

After a lengthy break from AP due to the persistant clouds in summer over Melb, and then trying to sort out some alignment issues, I finally got some photo time last night.
The photo below is 18 x 40 secs with bias, darks and flats. Stacked with DSS and quickly (levels and curves only) processed with PS2. The end result has a dark line horizontally about one third down from the top. Re -stacked with DSS and processed with GIMP and came up with the same result. I can't see any lines on the RAW subs.
Any idea what is causing the line?

Clear skies

Rod
:D:D

[rcheshire]

Rod. I think it's typical of faulty calibration/reduction. Unless you are already doing it, you might find that using uncalibrated darks and no bias frames will give better results. But you will need to make a master flat.

[Sarge]

Re-stacked with DSS, this time using "Median Kappa-Sigma clipping" for darks, bias and flats.

No lines and the colour is much better.

Thanks Rowland

Clear skies

Rod
:D:D

[LightningNZ]

Much better! The sigma-clipping methods are good cause they throw away outliers completely. You could probably decrease the colour vibrancy a little and stretch the bottom-end of the luminance curve a bit more to bring out the faint detail. Regardless you're well on the right track. :)