What is going on here.......

[paul mc c]

Just run this through APP as always but never seen this before......any ideas.

[Tomatobro]

looking at the frame edges the stack has been dithered? What calibration frames were used for the stack?

[tomato]

Is this OSC data or separate LRGB channels? If it’s the latter, do the separate R,G and B stacks look OK?

[gajjer]

Hot pixels? Have you used darks in the stack?

[paul mc c]

21 minutes ago, Tomatobro said:

looking at the frame edges the stack has been dithered? What calibration frames were used for the stack?

Used flats and bias only.

[paul mc c]

16 minutes ago, tomato said:

Is this OSC data or separate LRGB channels? If it’s the latter, do the separate R,G and B stacks look OK?

OSC

[paul mc c]

13 minutes ago, gajjer said:

Hot pixels? Have you used darks in the stack?

Thought that, confused why I never seen this before.

[gorann]

Looks odd and you never seen this before. It has a pattern to it. Makes me think it is not ordinary hot pixels. Maybe it could be some electronic interference with the USB connection to the camera. Have you changed anything with regard to cabling?

Edited March 16 by gorann

[woldsman]

Looks like hot/cold pixels smeared by dithering? Things to try would be darks, taking new darks (if you used an old library), re-stacking with sigma-kappa selection.

[paul mc c]

2 hours ago, gorann said:

Looks odd and you never seen this before. It has a pattern to it. Makes me think it is not ordinary hot pixels. Maybe it could be some electronic interference with the USB connection to the camera. Have you changed anything with regard to cabling?

I did re connect the leads just before the session....

[ONIKKINEN]

Did you let APP decide the integration settings automatically?

If APP chose to not reject anything, or chose too high a sigma for hot pixels you would see this.

[paul mc c]

1 hour ago, ONIKKINEN said:

Did you let APP decide the integration settings automatically?

If APP chose to not reject anything, or chose too high a sigma for hot pixels you would see this.

To my knowledge yes,I have took new calibration frames to see, interestingly run only lights through APP ant the artifacts were showing..

[ONIKKINEN]

I've found APP to be a bit too relaxed with rejection hot sigma with satellite trails and hot pixels visible, if i just go full automatic on the stacking process. Chances are APP chose some silly hot sigma, like 6 which rejects basically nothing. Try setting it to 3, they should go away.

[paul mc c]

2 hours ago, ONIKKINEN said:

Did you let APP decide the integration settings automatically?

If APP chose to not reject anything, or chose too high a sigma for hot pixels you would see this.

Is this what you mean.

[ONIKKINEN]

7 minutes ago, paul mc c said:

Is this what you mean.

Yep, choose the settings manually instead of automatic to have control over the rejection rate of hot pixels.

My APP subscription has run out and i dont quite recall what the options were, but i think there was a winsorized sigma clipping option for rejection. Set it to that and go for 3 sigma in kappa high. Kappa low is not too important, you can leave it to whatever it is, maybe 6 by default.

[paul mc c]

We update, new flats bias and dark flats..

[gajjer]

Glad you got that sorted. It's also an indication that your polar alignment isn't too good and that the frame is moving slightly with each successive capture. You'll see it on the stacking stats in Deep Sky Stacker as changes in dx dy and angle.

Perhaps worth spending some time aligning before you start. PHD makes it quite easy.

cheers

gaj