Re: Methods for convert spectra intensities in flux unit
Posted: Fri Apr 04, 2014 12:02 am
Hi Paolo,
Excellent initiative!
All seem right
Concerning BVR photometric coefficients evaluation, I have used some
Landoldt star observed in photometric mode. See part 3 of this
page:
http://www.astrosurf.com/buil/calibrati ... ion_en.htm
You have yourselve the answer about flat-field (not necessary because division of two
affected terms). But ok, is the two spectrum (ref and target) are not in the
same place on the CCD you can have some pseudo noise - but of low importance, I think.
While this does not seem to me strictly necessary here, you can
calculate a "plane" flat-field containing the map of pixels response non-uniformity (PRNU correction).
This solves the problems of high frequency response dispersion.
Look second item here (PRNU):
http://www.astrosurf.com/buil/isis/eshel/tuto1.htm
After computation of PRNU map, give the name of this image
in the standard "flat" field of "General" tab of ISIS.
I do not recommend however a classic flat-field for photometry mode, because
I think it causes more problems than it resolve (to be confirmed) and remember
it is a double flat-field correction.
Christian
Excellent initiative!
All seem right
Concerning BVR photometric coefficients evaluation, I have used some
Landoldt star observed in photometric mode. See part 3 of this
page:
http://www.astrosurf.com/buil/calibrati ... ion_en.htm
You have yourselve the answer about flat-field (not necessary because division of two
affected terms). But ok, is the two spectrum (ref and target) are not in the
same place on the CCD you can have some pseudo noise - but of low importance, I think.
While this does not seem to me strictly necessary here, you can
calculate a "plane" flat-field containing the map of pixels response non-uniformity (PRNU correction).
This solves the problems of high frequency response dispersion.
Look second item here (PRNU):
http://www.astrosurf.com/buil/isis/eshel/tuto1.htm
After computation of PRNU map, give the name of this image
in the standard "flat" field of "General" tab of ISIS.
I do not recommend however a classic flat-field for photometry mode, because
I think it causes more problems than it resolve (to be confirmed) and remember
it is a double flat-field correction.
Christian