DSLR Photometry - Check stars and magnitude types

American Association of Variable Star Observers (AAVSO)
Tue, 12/22/2020 - 09:47

What is the difference between a check star and a comparison star?  In AIJ you select the target star and a number of comparison stars. In MUNIWIN it only allows me to select one comparison star but many check stars.

Can you explain the difference between catalogue magnitude and instrumental magnitude and why is there a preference for instrumental magnitude?  Presumably instrumental magnitude is a relative magnitude in which case you'd have to know what it was relative to.




Bundesdeutsche Arbeitsgemeinschaft fur Veranderliche Sterne e.V.(Germany) (BAV)
The comparison star, with a…

The comparison star, with a certain magnitude, is used for comparison with the variable star. The DSLR Guide recommends ~ to stay in a range of 2.5 mag from the variable. More comparison stars (ENSEMBLE option at Muniwin light curve dialog) making better statistics. They also should have the same color or spectra. So V-C is your lightcurve. Take comparison stars from VSP.

The check stars, are also constant, they check that the comparison stars are also constant and not variable by accident.   C-K should be a straight line.

If you have the lightcurve plottetd, SAVE AS AAVSO Extended Format. There you put in the VSP catalog magnitude. Muniwin compares this to the variable.

For instrumental magnitude see Muniwin help.


I take as compare stars some with close magnitudes from the variable. For check stars I take at least 2, from VSP , and some with farther away magnitudes from the variable. So i am getting 3-6 mmag.


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