gcx 0.9.7 review

by rbytes.net on

GCX in the latest incarnation of the cx camera control and data reduction program

License: GPL (GNU General Public License)
File size: 0K
Developer: Radu Corlan
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GCX in the latest incarnation of the cx camera control and data reduction program. gcx is written in C using Gtk+-1.2, and provided under the Gnu General Public License. gcx was tested on Linux and FreeBSD.

The previous version of GCX , CX was written to control the newly designed cpx3m ccd camera. Once the basic camera control functions were running, it was easy to add some LX200 control functions, so that the telescope could be pointed at various objects without having to switch applications.

Having telescope control and image acquisition integrated into one program makes the following step obvious: after entering goto/get commands over several cold nights, one wants to automate the process--especially if he observes a large number of fields every night (as when doing variable star work).

The fact that the author's telescope doesn't point precisely doesn't help automation. So the ability to check/correct the pointing becomes essential. cx first got the ability to read star information from the GSC and overlay it on the images; that eases visual checks (one doesn't need maps anymore) but still is one step short of full automation.

Finally, when reliable field matching was implemented in GCX , it became possible to make the program fully automatic. In the current version, GCX can run through a list of observations completely unattended, and only stops if clouds roll in.

As it happens, field matching and image processing are also essential steps for CCD photometry. Over the time, the photometry functions of GCX have expanded continuously up to the point where they contribute the largest part of the program. It is currently possible to reduce photometric data frames in a completely automatic fashion, and perform color transformations, transformation coefficient fitting and all-sky reduction with relative ease.

Here are some key features of "gcx":
Image handling

Open/save 16-bit FITS image files;

GCX uses floating-point images internally, so other FITS formats are easy to add;
Zoom/Pan images, adjust brightness/contrast/gamma in an intuitive way, appropiate for astronomical images;
Convert FITS files to 8-bit PNM after intensity mapping;
Show image statistics (both global and local);
Maintain a noise model for the image across transformations; //
Maintain bad pixel information;
Perform ccd reductions (dark/bias/flat);
Automatically align (register) and stack images.

Catalogs and WCS

Read field star information from GSC1/2 and Tycho2;
Read object information from edb and native files;
Read recipe files;
Detect sources (stars) from images;
Overlay objects on the image;
Edit objects' information;
Match image stars to catalog positions;
Calculate world coordinates for image objects.

Camera Control

Control cameras over a TCP socket using a simple protocol;

The control proces (cpxcntrl) presently supports the cpx3m camera. It can be easily modified to support other cameras.

Acquire images under script control;
Set binning/windowing/integration times/temperature;
Dark frames;
All acquired frames are fully annotated in their FITS headers;
Auto-generate descriptive names for files.

Telescope control

Support LX200 protocol over serial;
Point telescope under script control;
Point telescope by object name (if edb catalogs are installed);
Refine pointing by comparing image star positions with catalogs;

Aperture Photometry

Do sparse field stellar photometry using fixed circular apertures for stars, annular apertures for sky estimation;
Aperture sizes fully programmable;
Multiple sky estimation methods;
Uses a complex error model thorughout, that takes into account photon shot noise, read noise, noise of the callibration frames and scintillation;
Report noise estimates for every result;
Take photometric targets (program and standard stars) from recipe files, or directly from the image;
Produce a comprehensive report.

Multi-Frame Reductions

Fit color transformation coefficients from multiple frames;
Fit extinction coefficients;
Perform all-sky reductions;
Generate various plots for data checking;


Uses plain-ascii files for configuration files, reports and recipies;
Implements import filters and an output converter to interface with tabular formats;
Most functions available in batch mode, so the program can be made part of a script.

Gcx is free software, distributed under the GNU General Public License. Users can modify it to add features, reduction algoritms, support for other cameras/telescopes, file formats. It is written in C. The GUI uses the Gtk+ 1.2 toolkit. Some GNU-specific libc functions are used, but nothing fancy. It should compile and run on any system that has GNU tools, glibc and Gtk+ 1.2. GCX is maintained on a GNU/Linux system.

What's New in This Release:
This release fixes some endianness issues on fits I/O, and more properly formats filter names in photometry reports. In addition, it has been verified to compile on OS X.
Debian and RPM binary packages have been added to the distribution, as well as a proper man page.

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