Aperture Photometry Tool (APT), v. 2.8.4
Russ Laher (laher@ipac.caltech.edu)
IPAC, California Institute of Technology, M/S 100-22, Pasadena, CA 91125
Copyright © 2007-2020, All rights reserved.
Always remember the
First Rule of Data: Look at the data!
Doing this and using this software will make you an "apt" astronomer.
Abstract
APT is software for astronomers interested in manually exploring the
photometric qualities of astronomical images. It is a graphical user
interface (GUI) designed to allow aperture-photometry calculations to
be visualized. The finely tuned layout of the GUI, along with judicious
use of color coding and alerting, is intended to give maximal user
utility and convenience and minimal chance of blunders.
Simply mouse-clicking on a source in the displayed image will instantly compute
and print out, for the specified aperture geometry,
source intensity and source-intensity uncertainty, along
with both conventional and robust measures of the sky background
and sky-background scatter.
APT is geared toward processing a small number of images, and is not suitable
for bulk processing a large number of images (unless a large number of
CPU cores are available), unlike other aperture-photometry
packages (e.g., SExtractor). However, APT does have a convenient source-list
tool that enables aperture-photometry calculations for a large number of
detections in a given image, albeit the user is advised that
patience is required for the relatively slower computational times
expected for software implemented in the Java programming language
(although multi-threading can be enabled for faster runtimes).
The source-list tool can be run either in the automatic
mode to generate a hands-off photometry-results table,
or in the manual mode to permit inspection
and adjustment of the aperture-photometry calculation for each individual detection.
APT displays a variety of useful plots with just the push of a button, including
image histogram, aperture slice, source scatter, sky scatter, sky histogram,
radial profile, and curve of growth. APT has many functions for customizing
aperture-photometry calculations, including outlier rejection, pixel "picking"
and "zapping", and a selection of source and sky models. The radial-profile-interpolation
source model, which is accessed via the radial-profile-plot panel,
allows extrapolated recovery of flux density in pixels with missing data.
Aperture corrections vs. aperture radius can be automatically computed
and applied, if activated by the user preferences, so that the
aperture size can be reduced for improved
signal-to-noise ratio. Many of these software features can be especially
beneficial in crowded fields.
Troubleshooting and Bug Reporting
If you experience an unexpected behavior from APT, try looking at the output in
the terminal window where you are executing the software (or in the console window
if APT was installed and run as a double-click application). This may shed some light on
the matter.
If you find a bug, please e-mail Russ Laher (laher@ipac.caltech.edu).