15th Feb 2024: Astro Pixel Processor 2.0.0-beta29 released - macOS native File Chooser, macOS CMD-Q fixed, read-only Fits on network fixed and other bug fixes
7th December 2023: added payment option Alipay to purchase Astro Pixel Processor from China, Hong Kong, Macau, Taiwan, Korea, Japan and other countries where Alipay is used.
Greetings all,
I am beginning astrophotography and image treatment, so I am facing all the problems in the same time :))
As a reminder, I use a C11 Edge HD, a Paramount ME and an ATIK 4000 (plus filter wheel of course). As I do live in Paris, France, the tube is remote. So, it is difficult for me to correct a few things, one of them being the optical train. I will soon add a focal reducer to the optical train, and I will then re_rotate the camera at 0°, made a full new calibration on TPoint, a new PEC etc, hoping it will in resolving my guiding problems (as you can see in the pictures below, the stars are oblong).
Concerning APP, here are 2 results I get with 52 lights of 60 secs with the CLEAR filter, 30 darks of 60 secs, 120 bias and 36 FLATS with CLEAR filter. I have several questions :
1) If I load the FLATS and use them in the calibration process, the dust bunnies become obvious, and I really don't understand why.
2) If I load the FLATS and a BPM, the BPM is recognized as such, but the lights don't have the small "BPM" flag, and when I check the image-l, the hot pixels remain indeed, as if the BPM was not used.
3) There is dark line in the left center of the image... any idea what causes it ? I don't have it on the FLATS 🙂
I link you here all the masters and the BPM too in JPEG, as I am not sure the FITS will fit in size...
Oh, sorry, let me add a 4th question : how to diminish the "burned center" of the brightest stars ? I have it on my "native" lights 🙂
TY SO MUCH in advance for any help here 🙂
Hi Jean-Brice @jb-gayet,
Please study the basic data calibration principles to be found here:
In aswer to your questions
1) If I load the FLATS and use them in the calibration process, the dust bunnies become obvious, and I really don't understand why.
For good data calibration, especially flat-field calibration using flats, it's essential to calibrate your flats with either a masterbias or a masterflatdark. Some holds for the lights, they need to be calibrated with a masterbias or masterdark as well. One of the essential principles is that the bias offset/pedestal needs to be subtracted of both lights and flats to get accurate flat-field correction.
2) If I load the FLATS and a BPM, the BPM is recognized as such, but the lights don't have the small "BPM" flag, and when I check the image-l, the hot pixels remain indeed, as if the BPM was not used.
if the BPM is not matched with the lights, it means that the instrument name of the BPM (which is convention for the camera used) doesn't match the instrument of the lights. With the batch modify tool you can adjust this by modifying the isntrument of the darks for instance and then creating a BPM from those darks.
3) There is dark line in the left center of the image... any idea what causes it ? I don't have it on the FLATS 🙂
the dark line is actually a cold column, not entirely defect, but it's not behaving well. (As you know by now, APP 1.060 will be able to correct this 😉 )
4) how to diminish the "burned center" of the brightest stars ? I have it on my "native" lights 🙂
if this is burned on the linear captured data, then you can only reduce the exposure time or reduce the gain of the camera to prevent that.
Kind regards,
Mabula
Hi Jean-Brice @jb-gayet,
Thank you for sharing your data. I have taken a look at what's happening and I have also upgraded the detection of bad columns in APP. The cold column will now be corrected.
The data that you have is a bit inconsistent in reporting valuable metadata like exposure and gain used with your camera. The gain is reported on the lights, but not on the calibration frames (so capture software is not reporting this apparently). I have corrected this with the batch modify tool.
Together with upgrading the calibration engine for cold column detection and correction, I get good calibration results:
shown is zoom in on an uncalibrated versus calibrated light showing some hot and 1 cold column. Calibrated with a Masterdark, a Masterflat that was bias subtracted, and a BPM with your bad columns.
This is a JPG of the final integration, and a very strong stretch showing that flat-field calibration is working well 😉
Kind regards,
Mabula
Thank you so much for your help here again Mabula 🙂 over cloudy nights don't permit me to test with new images your upgrades but I am already totally APP 😉
