Photom -- programs to perform photometric calibration of stellar photometry
Version 0.8: March 27, 2005
Version 0.8 has one big enhancement and one small fix:
- The user can now request that stars detected in only a single
passband be retained and included in output.
They will have no color corrections made, only
zero-point and extinction shifts.
- A minor big in initializing memory has been fixed; it caused
the selftest script to fail on some machines.
Added March 25, 2006:
Version 0.8 (and all earlier versions)
have one important bug.
Thanks very much to Andisheh Mahdavi
for pointing this out.
I ought to fix it in a future release ....
- The code requires the names of the filters
for which data will be reduced to be
"V" and "I".
It turns out these are the filters used
TASS Mark IV
project, for which this software was written.
I was just too lazy to create the proper routines
to handle arbitrary filter names.
So, whatever filters you are using, you'll have to
supply "V=" and "I=" as the arguments on the
command line, even if the data of interest
are, e.g., "B" and "V".
Added Sep 7, 2007:
If the code compiles and links, and passes some of the
self-tests -- but fails on others --
try editing the Makefile to change
CFLAGS = -g -O2
CFLAGS = -g
These programs are designed to take raw, instrumental measurements
of stellar brightness and convert them to calibrated magnitudes
on some standard system.
They were written as part of the
TASS Mark IV pipeline ,
but may work on other datasets.
This package creates two executables:
- collate, which matches up measurements of the same
star in images taken through different passbands
- photom, which compares multi-passband measurements
of stars to magnitudes in a catalog, determines
the coefficients of a simple photometric solution,
and applies it to the raw measurements
The photom program tries to fit the raw measurements
from N frames
to the catalog magnitudes with
in one of three modes:
- if given command-line option mode=noextinct,
an equation of N + 1 free parameters and no extinction
calibrated mag = raw mag + a + b * (raw color)
- if given command-line option mode=noextinct and fixk=,
an equation of N + 1 free parameters and differential
extinction within each frame with user-supplied coefficient
calibrated mag = raw mag + a + b * (raw color) - k*X
- if given command-line option mode=extinct,
an equation with just 3 free parameters
calibrated mag = raw mag + a + b * (raw color) - k * airmass
- a_i is the magnitude zero-point for frame i,
or, in the last case, a is the single magnitude
zero point shared by all frames
- b is a first-order color term
- k is a first-order extinction coefficient
There is no default; the user must specify
the mode in the command line.
If no values for fixk are given,
then no differential extinction is included in the solution.
The source code is vanilla ANSI C.
It links against the standard math library,
and also against the
GNU Scientific Library (GSL).
It works off the command line, with no user-friendly GUI.
The package includes a self-test is written in Perl, but it's not necessary
for the operation of the programs.
The GSL will take about 75 MB of disk space to download,
compile and install, but much of that is needed only
The photom code itself requires only a few tens of MB.
The current version is photom 0.8, last modified March 27, 2005.
Older version is photom 0.7, last modified Aug 2, 2003.
Last modified March 27, 2005 by