[JohnH]

Help,

I took 20 3 mins iso800 shots of m18 last night, took darks and flats too. Stacked and processed in IP2.75 as I have done many times before and the result - diagonal streaks appear when I used DD to bring up the nebulosity. What is causing this? I have tried reprocessing a number of times but cannot eliminate the problem. It seems to me the darks are not good - I have some residual amp glow showing too (crpeed out of the image attached though)

I should say this was all done with the camera set to LARGE/FINE (jpeg), is that the problem? (I have done this before too), advice/opinions/ideas welcome?