I'm shooting some faint dust in Taurus with a Nikon 180mm f/2.8 lens at f/2.8 on a D5300. The lens has some vignetting wide open.
I shot some blue-sky flats during daytime.
I tried calibrating the lights with darks, flats and bias in both Images Plus and DeepSkyStacker.
The weird thing is the flat calibration is completely different in each - see the attached files. The DSS stack has a large red halo. The IP stack has a darker center with brighter corners.
These are stretched, sky background neutralized, and then hit with the "equalize" command in Photoshop, which ridiculously exaggerates the contrast, but shows the problems.
I've tried calibrating without the darks, and also checking on and off "Set Black Point to Zero" in DSS.
The flats are not clipped in any of the channels.
All lights and calibration frames are shot at ISO 200 so it's not an ISO mismatch in DSS.
In the original stack I have 117 x 4min Lights, 6 darks (ambient temps were very cold), 64 flats and 64 bias.
I have put 3 frames each of the lights, darks, flats, and bias here in DropBox:
I'm only posting 3 of each because it goes a lot quicker if anyone wants to try it and it shows the same problem as the full set.
I repeated the tests with blue-sky t-shirt flats and it didn't make any difference, the problem was still there.
I also ran a set with the 180mm lens and a Canon and didn't see anything like this.
I'm wondering if this could be something related to the black clipping in the Nikons?
Any suggested solutions would be greatly appreciated.
Edited by Jerry Lodriguss, 17 November 2016 - 08:03 AM.