Apparent Image grid

[M44DSW]

I am seeing this as well. Not seen before, same workflow, same camera, don't think I have changed any settings, only change is PI has updated a few times since the last time I used it last season. I only get this when I Star Align, it is not apparent in the calibrated image, nor the calibration frames or the original image. I have a CMOS mono camera so ZWO ASI1600MM.

I have attached an STF stretched screenshot.

Any ideas?

[pfile]

have you tried making new darks?

you can try the pedestal thing and see what happens.

rob

[M44DSW]

Hi,

Ok I have worked it out, it is the algorithm being used for image registration. There has been a change in the latest update and I updated my Mac last week. So I have the interpolaion set to Auto. This should select Mitchell-Netravali Filter which it had been up until now as my scaling factor is 0.3, however it is now selecting Lanczos-3 and causing the issue. Selecting Mitchell-N manually fixes the problem and looking back at my last image I took with this camera you can see the image registration module has changed, the current one I am using is 01.04.01.0362 whereas the previous one was 01.00.05.0608. Not sure what has changed but going back to that module on another Mac fixes the issues with auto. Out of interest Nearest Neighbour also produces good images without the pattern.

Thanks
Dave

[pfile]

you should still check your calibrated subs for pixels clamped at 0 - the artifact is from registration but you may just be masking it by changing the algorithm. i think lanczos-3 has been the default interpolation method for a long time now.

rob

[mmirot]

Adding a 100 output pedestal at calibration does not help. Must be something else.

[pfile]

well still try applying this pixelmath to one of your calibrated subs and see if you have a bunch of white pixels in the result:

iif($T==0,1,0)

you can try this on your non-pedestal calibrated image and the pedestal-calibrated image and see if there is any difference. it could be that a pedestal of 100 is not enough.

or, it could be something else as you say, but it's worth looking for clamped pixels.

rob

[mmirot]

Rob,

I have used an output pedestal of 100 and the maximum of 999.  100 leaves about 70 zero pixels. 999 leaves about 25 .
Having trouble producing a cal image with none. Suggestions ?


Max

[pfile]

how about an image with no pedestal applied?

those are small numbers of 0-valued pixels, i think for the grid to show up as a result of clamped pixels you'd need a lot more of them than what you have. there could be some other cause for your problem...

rob