Affiliation
American Association of Variable Star Observers (AAVSO)
Tue, 07/21/2020 - 16:14
I seem to be having problems with calibrating my images. It doesn't show up in FIT Liberator but when I post an image to nova.astrometry.net or VPHOT, it becomes very noticeable.
I have been using SiriL for astrophotography because DeepSkyStacker will only stack one subframe no matter what I do while SiriL will stack as many as it can line up based on the stars. So, I went ahead and used it for photometry. Does anyone have any suggestions to fix this issue?
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Software for pretty picture astrophotography often does strange things to photometry images.
I suggest you calibrate your images with software that is appropriate for photometry: AIP4W, MaximDL, CCDSoft, AstroimageJ. Others can probably add more names to this list.
Phil
IRIS and MuniWin can be added as recommended photometry reduction software. Se the DSLR-manual
https://www.aavso.org/dslr-camera-photometry-guide
What is your problem with Siril? It seems to be lightning fast.
Yours
Søren Toft
Soren,
I don't necessarily have a problem with Siril, but when I see an image as bizarre as the one Tim posted, my first suspect is the software.
Rather than asking for calibration frames and uncalibrated images in order to try to track down the problem I think the first order of business should just be to calibrate the image with software that we know works for photometry.
Thanks for mentioning IRIS and MuniWin as photometry friendly software.
Phil
I have gone to AIJ, mostly because AIP4Win is quirky on my Win10 computer.Note that some of the images I processed in CCDStack did not play well with VPhot. AIP4Win usually shows up on VPhot as "uncalibrated" because of the fits header. But that is not a fatal problem. AIJ is free. I know its reptation in AAVSO circles is for exoplanets, but it can also be used for simple calibration without the exoplanet anlalysis. I have never had a problem with AIJ in terms of producing good calibarted images.
Ed
I use AIJ for callibration (and photometry). During callibration, it can do other useful things.
When you enter the name of the target (variable star) in the Data Processor Coordinate Converter dialogue, and press Enter, AIJ instantaneously pulls the RA and DEC from SIMBAD into the dialogue. Then, during callibration, the FITS headers are updated with the RA, DEC and airmass of the target. The latter can then be written into every record of the data file in time series photometry.
Another thing I like about AIJ (although I presume other photometry software can do this) is to output not only the JD_UTC but also the HJD_UTC for every image.
Roy