Hi,
I loaded already calibrated FITS files with the green channel already extracted. When running STACK (calibration only) I receive the usual warnings about missing darks and flats but when completed the results tab remains empty. What did I do wrong? Any help appreciated!
cs Axel
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They stack here normally. The stars are pretty small due to the green channel but it is no problem. Try to go to default settings (see attached) and try again. Tell me if this helps.
Hi Han,
took some time as my hard disk decided not work any more... I simply installed the latest ASTAP version which should also kind of reset the software. I tried again (just adding 3 lights and pressing the Stack button) but same result - identical messages and no files are listed in the results section.
Yes the first screenshot you select in tab stack method "Calibration only". This means the files are only calibrated. Without flat or darks nothing will happne.
To stack select in tab "stack method" method "average" or sigma clip".
MfG,
Han
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Han,
I want to prepare a time series for photometry so I do not want to stack. If I have neither darks nor flats do I still have to calibrate or can I load the images immediately into the results tab?
cs Axel
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I would like to add that without calibration we have not only darkening in the corners of the frame, but also a much worse effect - the stars gradually shift from frame to frame and sometimes broken or on the contrary, bright pixels end up "creeping" on the image of the star, creating a completely realistic effect of an eclipse or flash.
Therefore, be sure to calibrate frames for photometry, it will save you from a lot of erroneous results and a lot of unnecessary work.
Have a clear sky!
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Hi Aleh,
while I do not know why not using a flat field would shift stars from frame to frame there is no question that flatfielding is in most cases necessary for photometry.
However, when you use only small portions of a field (variable and check/comparison stars very close together) a check on the sky brightness around the stars will show you that sometimes differences in background brightness are negligible and a flat field may not be necessary.
I am still feeling my way around astap so I am still checking what works and how. But yes, I usually calibrate my images for photometry ;-)
cs Axel
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Hi,
I loaded already calibrated FITS files with the green channel already extracted. When running STACK (calibration only) I receive the usual warnings about missing darks and flats but when completed the results tab remains empty. What did I do wrong? Any help appreciated!
cs Axel
Hi Axel,
To understand what is happening, Can you share some of the files for testing?
e.g upload to
https://ufile.io/
and share the link
Han
Hi Han,
sorry, I did forget the subject...
Here are the files:
https://ufile.io/f/9sw0f
cs Axel
They stack here normally. The stars are pretty small due to the green channel but it is no problem. Try to go to default settings (see attached) and try again. Tell me if this helps.
Han
Hi Han,
took some time as my hard disk decided not work any more... I simply installed the latest ASTAP version which should also kind of reset the software. I tried again (just adding 3 lights and pressing the Stack button) but same result - identical messages and no files are listed in the results section.
cs Axel
Hi Han,
I experimented a little: when I add a masterflat the files are processed (see attachment).
cs Axel
Yes the first screenshot you select in tab stack method "Calibration only". This means the files are only calibrated. Without flat or darks nothing will happne.
To stack select in tab "stack method" method "average" or sigma clip".
MfG,
Han
Han,
I want to prepare a time series for photometry so I do not want to stack. If I have neither darks nor flats do I still have to calibrate or can I load the images immediately into the results tab?
cs Axel
Hi Axel,
Without darks, flats and flat-darks just load them in the photometry tab.
Without calibration the accuracy will be little less depending on the signal drop in the corners. But it will work fine.
Han
I would like to add that without calibration we have not only darkening in the corners of the frame, but also a much worse effect - the stars gradually shift from frame to frame and sometimes broken or on the contrary, bright pixels end up "creeping" on the image of the star, creating a completely realistic effect of an eclipse or flash.
Therefore, be sure to calibrate frames for photometry, it will save you from a lot of erroneous results and a lot of unnecessary work.
Have a clear sky!
Hi Aleh,
while I do not know why not using a flat field would shift stars from frame to frame there is no question that flatfielding is in most cases necessary for photometry.
However, when you use only small portions of a field (variable and check/comparison stars very close together) a check on the sky brightness around the stars will show you that sometimes differences in background brightness are negligible and a flat field may not be necessary.
I am still feeling my way around astap so I am still checking what works and how. But yes, I usually calibrate my images for photometry ;-)
cs Axel