19 June 2021: Our upload server https://upload.astropixelprocessor.com/ has been migrated successfully to our new office with higher upload and download speeds (nearly 10MByte/sec up/down ) ! We now have 1 general upload user called: upload with password: upload. The users upload1 - upload5 have been disabled.
31 May 2021: APP 1.083-beta2 has been released ! APP 1.083 stable will follow soon afterwards. It includes a completely new Star Reducer Tool, New File Saver Module, Improved Comet registration and much more, check the release notes here!
Banding pattern artifact appears after registration
For some time I have been trying to solve a banding artifact occurring in my highly stretched (OIII and SII) data. I thought for a while that this was an interference pattern between the NB filters and the ASI 1600MM Pro (Mono).
Tonight however I realized that the pattern appears with variation on each individual sub-frame only after registration. Occurs in both normal and mosaic mode, though mosaic produces more curved or even pinwheel artifacts. It is less pronounced but still visible in the masters.
Also less pronounced in other viewers or processing software, but still appears if I stretch far enough
It is not present in the calibrated frame:
I have this happening to me now as well. The images look great (HA-OIII extracts of Ha and OIII). After registration the image develops vertical banding that are most pronounced in the center of the image, and wither out towards the edges. I am unable to understand why this is happening.
Have you solved this or has anyone given helpful tips?
Interesting. Could you upload the integrations (2 I assume) and the masterbiad, masterdark and masterflat (for me to check) to our server?
Go to https://upload.astropixelprocessor.com and use upload3 as username and upload3 as password.
Create a directory named “raed-stripesafterregistration” and upload in there. Thank you!
Raed and Vincent,
After looking into this more I believe it to be moire, an interference pattern introduced by resampling, rescaling, or rotating images. There are several threads on the cloudy nights forum discussing it.
In my images I notice that a more pronounced moire pattern occurs when the images are zoomed out, but fades when I zoom in, suggesting the resampling artifact is introduced by the display rather than the actual data.
There is a fainter moire pattern that persists, however, and can appear later in post processing when aggressive stretch or noise reduction masking is applied to the fainter NB channels. This I believe is introduced when the images are resampled for registration. Zooming in alot I can see stair step aliasing artifacts in bands across some images that correlate. I will try to post some pictures later.
I have had some luck reducing it if I use a different interpolation method in PI for registration, but I'm not sure how to implement this in APP.
From what I read, the lancos interpolation is more prone than others to moire, and cubic is suggested. Also good calibration frames seem to help.
Let me know if you have any luck or other insights.
Thanks for the insight Chris, I will ask Mabula what he thinks about that.