Advice on calibrating a time series

Science Data Analysis
1

Please can anyone advise.
I use ASTAP for calibrating my CMOS images prior to uploading to VPhot for photometry, and this involves stacking as part of the pre calibration process.
I have recently amassed a time series set of obs on AD Leo a flare star, looking for events at a 10s time resolution so clearly stacking images is not useful.
What software could I use to calibrate these single images please.
Thanks
Kevin

2

I believe you can do this in ASTAP.

Click the "Stack Method "tab and choose the stack method of “Calibration and alignment only”. That will calibrate and align without stacking.

3

Many thanks btschumy for the tip.
I’ll give it a go.
Kevin

4

I tried that but VPhot doesn’t recognise that they have been calibrated. I wondered why they needed aligning given that they are freestanding independent images unlike a stacking. Maybe I could try just calibrate?

5

I just tried it as well and you are correct that the “_aligned.fit” files don’t seem to have the calibration data “DFB” in the header. I have asked Han in the ASTAP forums what is going on. I’ll report back on what he says.

Bill

6

Thanks Bill,
I have tried a few posts in that forum on other topics but never got a response,
Regards
Kevin

7

I haven’t gotten a response either. This is unusual since Han is generally quite responsive.

I decided to download the lasts ASTAP (2025-03-07) since the one I had was a year or two old. With the new version I did see the CALSTAT key in the header with a “BFD” value. So maybe there was a bug and it was fixed. You do need to make sure you are looking at the “*_aligned.fit” in the Results section.

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1 Like
8

Thanks Bill,
I’ll check my version of ASTAP
I received this info from Ken Menzies in a different post.
"Kevin:

VPhot is looking for a specific fits header (CALSTAT=BDF) to report calibration. HOWEVER, just ignore the fact that the Cal button in your image list is red. You know that your images are calibrated. There is probably a HISTORY header installed by ASTAP?

Just proceed with your photometry as normal.

Ken

1 Like
9

Hi
AstroImageJ is a great application for image reduction. It’s also tailored to Exoplanet analysis and reporting as well as variable star reporting. Very easy to use for image calibration for anything really. It’s a free application that is frequently updated and extremely well documented.

PS: I’ve been using AIJ for the Time Series submissions I’ve been making for AD Leo.

10

Hi Kevin,

You can use Phoranso for calibration of FITS CMOS images. In addition, you can align/stack images, if needed, and do the photometry for AD Leo and other variables in your FOV, and then generate the AAVSO (and other) reports.

Best regards
Tonny

11

Thanks for the info Tonny and Gary, and apologies for slow reply
Cheers,
Kevin