Hello Han,
this is the first time, that I made a timely sequence from a variable, here the QSO TON 618. Acc. AAVSO the check star has a magnitude of 15.176m. Attached are the measurements.
Now the question: Is variable's star magnitude calculated acc. measured check-star's magnitude and then aligned assuming that check star has a constant magnitude acc. eDR3 database?
Regards Achim
All magnitude measurements are calibrated against the Gaia stars it can find in the image with an SNR above 30. This can be a few hundered stars. So not against the Check star.
For Johnson-V or the Green channel of a DSLR you should the V17. For unfiltered, images
you should use H17, or H18.
Does the measured value of the check star match the AAVSO value?
Han
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Han, you misunderstood. AAVSO-Ref-stars are selected stars in the field to be constant in magnitude. But ASTAPs Ref-star isn't constant (it's the same star of course). I made a chart with VAR / REF / AAVSO-mag / Aligned mag, see attachment
I'm using only V17
Regards Achim
When I measure the stability of a AAVSO reference star, then is see something like 0.02 magn variation or less. if I remember well. Your graph shows much more. So at the moment i don't understand it.
There is no possibility to select reference stars in ASTAP. Only the Var, Check and one more I called 3.
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
Hello Han,
this is the first time, that I made a timely sequence from a variable, here the QSO TON 618. Acc. AAVSO the check star has a magnitude of 15.176m. Attached are the measurements.
Now the question: Is variable's star magnitude calculated acc. measured check-star's magnitude and then aligned assuming that check star has a constant magnitude acc. eDR3 database?
Regards Achim
Hello.
All magnitude measurements are calibrated against the Gaia stars it can find in the image with an SNR above 30. This can be a few hundered stars. So not against the Check star.
For Johnson-V or the Green channel of a DSLR you should the V17. For unfiltered, images
you should use H17, or H18.
Does the measured value of the check star match the AAVSO value?
Han
Han, you misunderstood. AAVSO-Ref-stars are selected stars in the field to be constant in magnitude. But ASTAPs Ref-star isn't constant (it's the same star of course). I made a chart with VAR / REF / AAVSO-mag / Aligned mag, see attachment
I'm using only V17
Regards Achim
Which star is labeled kmag?
When I measure the stability of a AAVSO reference star, then is see something like 0.02 magn variation or less. if I remember well. Your graph shows much more. So at the moment i don't understand it.
There is no possibility to select reference stars in ASTAP. Only the Var, Check and one more I called 3.
Kmag is the check star. AAVSO ref is set constant from me in the Excel chart.
Kmag star and AAVSO star are the same
may be this graph helps: The ASTAP-Chk-star is the star with the constant brightness as of AAVSO
Han, close this thread, I now understood
Thanks for your answers.
Achim
The variation of the check star is too much. If you can provide me some sample files i can have a look.
e.g upload to
https://ufile.io/
and give me the link.
Okay. Is the SNR high enough? Low SNR could result in more noise in the signal
yes, I measured noise.