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Department of Physics |
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AstroLab |
Overview of Procedures for Photometry
Initial Preparation
- If necessary (DRACO and older EAST-14 images), subtract a master dark frame. Images starting with d/ad are already dark subtracted.
- Locate the master flat for the given telescope and filter. They are stored in
"/mnt/share/flatfields/".
Aperture Photometry
Measure the aperture photometry of objects on an image by one of
following methods:
- interactively with GAIA and enter derived values
as a line in the "
summary.obs" file
- fully automatically with the "
photom_ad2.py" script
To understand the photometry process, it is a useful and essential
exercise to process some images "by-hand" with GAIA.
The interactive approach of
GAIA will also give enable you to
choose appropriate aperture sizes
and give an double check for the automated process.
After Aperture Photometry
- use the "
raw2dif" routine, which adds an appropriate
constant to the target magnitudes in order to place the photometry
on a standard system. This is usually not possible for asteroids which
have long timescale magnitude variations, due to their distance from
Earth, as well as the variation due to rotation.
- remove discordant points with a text editor
- if required average observation lines with the "
average_lines.py"
script
- if required convert the observation times to Heliocentric JD with
the "
cor2hjd" routine
Period Finding
The automated "fast_solve.py" routine
effectively uses phase dispersion minimisation to both find
the 'best' period.
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