What might have caused this full screen glow/gradient?

[mos]

Hello everyone, 

I image with a 600D through a 150PDS and results from the other night turned out really weird with a full-screen white gradient glow effect. Attached is a stretched and wiped (Startools gradient removal) stack of 8x500s lights to illustrate the issue. The glow remains after stacking with darks, flats and bias etc and processing. 

My sensor wasn't any hotter than normal (I think - but unfortunately I somehow had turned of exif data tagging so cannot be sure) and the moon was out and at first quarter but wasn't anywhere near my imaging location. I also cover the end of the OTA with black cloth to prevent light leaking through by the primary mirror and I cover the camera view finder with its plastic cover. 

I've never had my lights turn out like this before so was curious if anyone new what could be causing it on this occasion?  As far as I'm aware I didn't do anything differently this time around. 

Thanks for any insights and advice,

Matt

 

[ollypenrice]

The first thing I'd do is make a stack without the flats. This has most of the hallmarks of over-correction, with some oddities thrown in for a challenge. Maybe give the no-flats image a stretch but nothing else and post it up?

The fact that you did your flats as usual doesn't mean they can't be wrong. The blessèd things have a mind of their own!

Olly

[vlaiv]

Hi, welcome to SGL!

I think it could be related to StarTools wipe background (gradient, what ever it is called) action. It is not action it self, but coupled with some other artifact. There is "edge" parameter or something like that if I remember correctly, and it is used to suppress this. I believe it is due to edge being slightly darker than the rest of the image and that is probably caused by mismatched darks.

What does your stack look like if you use Dark optimization in DSS and don't do StarTools background wipe thing?

[mos]

Hi Olly and Vlaiv, 

Thanks for your replies - I've been a lurker in here for the 3-4 months that I've taken up this hobby and I've learned so much off what you've posted in other threads already. The image above is just the lights and darks with no flats or bias. 

I had the chance to get out again last night with the results turning out the same for a stack with just lights with darks . So I went back and re-stacked past data that processed out fine and was again getting the same full screen gradient!! So it appears DSS is now doing something very weird when stacking...on default settings. It has been behaving a bit odd of late with Startools not able to open the generated autosave.fts file on occasion so there might be some underlying windows permissions issue with windows being windows. 

I'll keep trouble shooting and I've just got a trial to pixinsight so I'll try stacking with that when I figure it out and see what comes out. 

Thanks again for your suggestions. I'm relived that it is some sort of stacking/processing issue rather than a problem with my setup.

Matt