Improperly Calibrated Images

[Jared Greer]

Hello, I am an intermediate Pixinsight user. I have been using the software for 6 months now. A common problem I encounter with my personal astro images is poorly calibrated light frames which can be caused by a variety of issues. I recently grabbed a large HSO data set of the heart and soul nebula from the SPA-1 telescope with the CMOS camera. After stacking, I got a rather unsatisfactory result from the sii and oiii channels. I ran WBPP again and changed the pixel rejection to linear fit and enabled local normalization. I got better results, but there was still much to be desired with the radial gradient in the sii and oiii. The ha was okay, but it was still noticeable. I ran gradient correction twice on sii and oiii and once on ha. This did help, but only to an extent. I believe this was the result of poor calibration from the flats for the one-clicks that were published on Jan. 5, 2024. The others looked fine. How do I download the uncalibrated fits images so I can calibrate manually? I know how to obtain the calibration frames, but which ones should I download? the masters, or all the raw ones to stack? I have attached 4 jpeg images; processed and stretched starless ha, sii, oiii, and SHO. As you can see, there is gradient still present no matter what I do, and it causes problems in the combined and normalized SHO image.

[Reggie Jones]

Hi Jared.  This is a bit of a pain but it is the only way I've found to handle this.  Go to your data archive, wait for it to load, then select SPA-1-CMOS and wait for that to load, then do filter ha, and wait for that to load, then search for object name of this dataset and when that loads then select the files you want.  Make sure to have 100 selected for results and to get the raw files only, turn off "Show Calibrated Files".    100 is the max number of files you can download at one time.  You'll need to do something similar for the calibration files for SPA-1 CMOS.

12:18