VDB152

[martin_h]

2 moonlit nights and clear! This was more of a test than a serious attempt. Very noisy and a strange gradient on one side, my bad pixel map is leaving black holes in places and my flats are turning dust bunnies into doughnuts, but apart from that..................

 

[wimvb]

Great image. More data should bring the noise under control.

Sometimes flats can over correct. I don't know what causes this, but I suspect that flat brightness can be a possible culprit.

[martin_h]

I'm just running a range of flats now for a test. a set of 22k, 25k and 30k adu and it still doesnt correct, strange!

[wimvb]

The large dustbunnies in the lower half of your image look almost embossed. Could it be that they have shifted? That could possibly explain their look.

The situations where flats could not correct light frames, was when they caused an inverted vignetting effect (=light corners).

The gradient on the right side can possibly be corrected by DBE or gradient exterminator.

Good luck

[martin_h]

1 hour ago, wimvb said:

The large dustbunnies in the lower half of your image look almost embossed. Could it be that they have shifted? That could possibly explain their look.

The situations where flats could not correct light frames, was when they caused an inverted vignetting effect (=light corners).

The gradient on the right side can possibly be corrected by DBE or gradient exterminator.

Good luck

Im beginning to think you are right, and there has been a movement between lights and flats, I ran a series of flats today from 20K to 35K ADU with exactly the same results in every one.

[wimvb]

You could try to overlay a stretched single frame with a single flat at 50 % opacity, to check if dustbunnies have moved.

[PatrickGilliland]

On 8/17/2016 at 12:00, martin_h said:

I'm just running a range of flats now for a test. a set of 22k, 25k and 30k adu and it still doesnt correct, strange!

For a test image it is a good start, LRGB under the moon is never easy.

On the flats you may want to come lower, for my 8300 chip i have found 18k works best.  Same results on QSI and FLI camera's so cant imagine QHY will be much different.

Paddy