[AstroPy] synthetic photometry

[Vicki Laidler]

Hi Thomas,

Indeed, astrolib includes pysynphot, which is presently being used under the hood of the HST Exposure Time Calculators. It's intended as a replacement for the IRAF STSDAS synphot package, and is largely complete. I'm the primary developer for pysynphot at this time.


You can certainly accomplish the task you describe below with pysynphot. You would need to create a throughput file (wavelength and throughput in dimensionless units between 0 and 1) for each band in your instrument, and a spectrum file or array (wavelength and flux) or black body as a function of temperature. Once you have those, you can simulate an observation and predict the magnitude, something like this:

import pysynphot as psyn
bp = psyn.FileBandpass('your_throughput_file.fits')
sp = psyn.FileSpectrum('spectrum_file.fits')
obs = psyn.Observation(sp, bp)
obs.effstim('abmag')  #gives you the observed magnitude

There is some documentation browsable linked from the astrolib wiki at http://stsdas.stsci.edu/pysynphot/ - it is incomplete but should be enough to get you started. Suggestions for improving the documentation are also very welcome. :) You can get more help here or from help at stsci.edu.

cheers,
Vicki Laidler

________________________________________
From: astropy-bounces at scipy.org [astropy-bounces at scipy.org] on behalf of Thomas Vaughan [tevaughan at gmail.com]
Sent: Tuesday, May 17, 2011 1:12 PM
To: astropy at scipy.org
Subject: [AstroPy] synthetic photometry

I'm looking for a convenient package that I can use to do synthetic photometry.

I thought that I'd probably write one myself, but I should at least
see what's available.

Browsing the Web, I came upon astrolib.

Can it already be used for synthetic photometry?

I need to make a star catalog by starting from a subset of Tycho-2
photometry and spectroscopic classifications. I have the overall
response for my instrument. I need to define a magnitude system for
the instrument and to predict the instrument magnitude for each star
in the catalog.

--
Thomas E. Vaughan
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