Strange calibration or registration issue

I just found out it's caused by the LNC algoritme. Too much dust signal I guess? 🙂 Now to figure out why I still have those columns.

Yeah these remain. Strange as it didn't pop up in my other processing with the same calibration files.

Posted by: Vincent Groenewold

Just finished some processing on NGC 7317 and M 45. 7317 went perfect, no left-over columns or weird noise. On M 45 however something strange happened. I suddenly see a hard transition as if a sub is smaller (it isn't) and lots of bad columns (or at least it looks like that). I tried several settings, with/without MBB, more or less noise reduction, etc. What could be the issue, the MF, MB and BPM are perfect (as they have been used by a few photographers on our Spain observatory).

Here's the issue;

Hi Vincent @supernov,

Thank you for sharing this issue. I am aware of the 

I suddenly see a hard transition as if a sub is smaller

problem, it pops-up sometimes whith a low level degree LNC on some datasets. I think I know why this happens so I will work on this soon.

As regards to the bad columns, that should be related to bad column detection and dithering of the data. Is the data well dithered? Perhaps you can show screenshots of a stretched Masterdark and the BPM ? In know that in some cases, enabling the Adaptive Data Pedestal could have a positive effect in this regard. Have you tried processing this with the Adaptive Data Pedestal in 2) on ?

How are things down under 😉 ?

Kind regards,

Mabula

Thanks for the suggestions. I was dithering yes, but only with small to medium dithering in SGP, I'm now collecting more data on high dither to see if that helps. The Adaptive Data Pedestal I didn't try, will let you know if it makes a difference.

Things are fine down under. 🙂 I've gotten used to life overhere and can be frequently found at the local (super dark) observatory here just 20 min's away. They are not really set up for photography though, so I'm trying to push that a bit which seems to have woken up a few people. haha Let's see how that turns out.

Ok so the pedestal didn't do much, but the new data worked flawlessly. The weird thing is that I also see that a single sub is being calibrated better in this run. So apart from the dithering, there seems to be something with the data itself as well, maybe a noise issue in the camera? Main difference was the temperature, -11 on the "bad" data and -7 in this session.

Hi Vincent @supernov,

Thank you for your feedback.

I have found and solved your bug:

...I suddenly see a hard transition as if a sub is smaller...

Here's the issue;

It manifested itself on some datasets when you used both LNC and a LN outlier rejection filter. Details are here:

https://www.astropixelprocessor.com/community/release-information/astro-pixel-processor-1-067-preparing-next-release/

• FIXED, LNC & LN Rejection filters, as reported By Vincent Groenewold @supernov in post https://www.astropixelprocessor.com/community/main-forum/strange-calibration-or-registration-issue/#post-3909

...I suddenly see a hard transition as if a sub is smaller...

Here's the issue;

If you used LNC and a LN outlier rejection filter, this issue could manifest itself on certain datasets. The main cause of the problem was located in the LN rejection filters. They weren't actively working on the boundary areas of the data's entire Field of View. This also was the case for general LNC use. The data analysis involved in both LNC and the LN rejection filters has now been improved/fixed to cover the entire Field of View. This error should no longer occur now. Shown is a clear example of the issue of H-alpha data on the Rosette Nebula, with the bug and with the bug fixed, parameters used in integration were

LNC 1st degree 5 iterations

Outlier rejection: LN MAD Winsor clip 1 x 2.5 kappa

With bug, from left to right, integration, rejection map, normalization map:

Fixed, from left to right, integration, rejection map, normalization map:

Thank you for reporting the issue 😉

Things are fine down under. I've gotten used to life overhere and can be frequently found at the local (super dark) observatory here just 20 min's away. They are not really set up for photography though, so I'm trying to push that a bit which seems to have woken up a few people. haha Let's see how that turns out.

Excellent, I wish you a great time over there and clear & dark skies 😉 !

The weird thing is that I also see that a single sub is being calibrated better in this run. So apart from the dithering, there seems to be something with the data itself as well, maybe a noise issue in the camera? Main difference was the temperature, -11 on the "bad" data and -7 in this session.

Hmm, sounds a bit odd then, let me have a look if you see it again perhaps ?

Cheers,

Mabula

That's awesome Mabula! As for the bad columns, I think it was camera related on that particular night, maybe interference or so, I didn't see it later.