[Solved] Geometric shapes in integration results

Hi @mountainair,

That looks really weird, can you share the fits headers with me? The info is shown in the metadata/header window to the left of the image viewer 😉

Mabula

Hi Mabula,

This has been reproducible with other targets as well.  It never happens when I stack lots of frames.  It seems to be worse with small numbers, like: 

2 frames - strong effect

3 frames - no effect

4 frames - effect

5 frames - no effect

6 frames - less effect

7 frames - no effect

8 frames - no effect

9 frames - no effect

10 frames - no effect

Here is what two stacked frames look like -- the effect is even stronger:

I have attached the FITS headers from the stacked result as well as the 2 individual subs that went into this.

Also, I am adding dynamic distortion correction to 4/registration, changing mode to advanced in 5/normalization and enabling 1st Degree LNC/3 tier and 5% MBB in 6/integration.  Those are the only changes.  Master flats, master dark flats, master darks and BPM used.

Note:  This is still occurring as of Beta 23.  It's not a killer, given it's rare to stack so few frames, but that's all I could get out of the supernova in NGC 1097 last night.  

@mabula-admin I have uploaded the subs I used, the integrated results, and the RGB-combined result to /AstroPixelProcessorUpload/MountainAir-geometricartifact on FileStation.

As I mentioned, this is likely lower priority.  In both these cases I tried to sneak in targets between other targets and ended up with a small number of subs -- in this case a ridiculous two for B and G and only one for R.

If this isn't worth fixing (it seems to go away entirely when you get to 7 subs per integration or more), perhaps just pop up a warning to users who try to generate integrations from a small, even number of integrated frames.

Hello all. I have put my integration in the folder in File Station. If you look at the header of the fit file, you can see my integration settings. The artifacts come from the Automatic mode in Tab 6. With so few images, Median is selected as the Rejection method and that creates the Geometric artifacts. You have to select Manuel Average in Integrate Tab 6, then everything works as expected. The hotpixels can be removed with Cosmetic Correction, at least most of them.

Hope this helps.

@mountainair & @minusman

Thank you very much for reporting this and your testing. It is something that definitely should not occur for sure, so I will test this and fix it 😉

I guess the combination here of both median and MBB causes this. Or does it also happen with MBB turned off? ( I will test myself of course 😉

Mabula

Hi Mabula, I can confirm that when MBB is deactivated the edges look fine.

With best regards.

Thanks @minusman for checking 😉

I will test and fix for sure !

Mabula

Hi @mountainair & @minusman,

This issue with MBB and little frames is fixed in beta26 which I will release in the coming days 😉 Thank you very much for reporting this issue.

In automatic integration mode, whenever MBB is enabled, the integration method will always be average, as it also is for drizzle and mosaics. In all 3 cases, this is vital. For MBB it is vital just like for drizzle, because we are using different weights per pixel.

But even in not automatic integration, if you would set the integration mode to median and enable MBB/drizzle, average will be forced since it is in fact critical. For MBB it is critical for correct pixelstack integration in those areas where MBB is active 🙂 .

Thanks, this is an important fix allthough it was not that obvious when more than 5 images were used in an integration. The problem was really clear with integration 2 images with MBB, median and equal weights. Enabling LNC in addition would let the issue even become more clear.

Mabula

Thank you both so much!