Variability in the curves of stars labeled Check and 3

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Variability in the curves of stars labeled Check and 3

Forum: General discussions ASTAP

Creator: Pat Browne

Created: 2023-10-29

Updated: 2023-11-14

Pat Browne - 2023-10-29

Salut!
I recently processed the images for RZ Dra and I discovered that the Check and 3 star were not of constant brightness, even though I selected the reference stars that were labeled in green Attached is the plot and the report for AAVSO

I am trying to understand why these stars are exhibiting variability ? Shouldn't their brightnesses show constant ?

thanks
Pat Browne

rzdra_35s_20231024_041002_cal_graph.png

rzdra_35s_20231024_041002_cal_report.txt

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han.k - 2023-11-01

Hi Pat,

That is clearly an abnormality. This must be caused by a severe change of conditions. Did the sky background or transparency change a lot? Normally it should not effect. Can you check visually the images involved?

Han

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han.k - 2023-11-01

If you can share some or all of the images then I can have detailed look.

Han

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Pat Browne - 2023-11-09

HI Han,
Sorry for the delay. (Somehow I didn't get notification of further activity. )

The answer to your question - yes the transparency changed during the sequence. There was a mixed cocktail of clouds and foliage in the way,

I'm hoping you can see something more revealing in the data so...
Here are links to the data and the calibration darks, flats:
http://www.enrimouskais.net/wp-content/uploads/2023/11/rzdra_35s_20231024.zip
http://www.enrimouskais.net/wp-content/uploads/2023/11/master_dark_flat_rzDra.zip

Thanks for your support!
Pat

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Pat Browne - 2023-11-09

Here are the check and 3 stars chosen for this run

rzDraCheck_3.png

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han.k - 2023-11-14

Hi Pat,

Sorry for the late reply. I have looked to your images. Some are suffering from clouds covering part of the visible stars. This will most likely spoil the calibration against the stars. ASTAP tries to calibrate against all visible stars. This will only work if the transparency for the received star light is homogeneous throughout the image. They only way forward is to redo the images under better conditions.

Regards, Han

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Pat Browne - 2023-11-14

Thanks very much Han for taking the time to investigate. Very much appreciated.

Let's hope for clear skies one of these days! As you said that's the way forward!!!

Pat

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