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Subsections

Introduction

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. GCX implements recipy files: local catalogs of field and standard stars that are used to automatically reduce variable star frames.

Features

GCX can do the following:

Image handling

Catalogs and WCS

Camera Control

Telescope control

Aperture Photometry

Interfacing

Free Software

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. 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.

Contributing

The most important contribution you can make to GCX is to try it out, and don't give up immediately if something goes wrong. Complain to the author about it--he will try to help you.

The next important contribution one can make is to extend the hardware support of the program. When interface library are available for cameras (many manufacturers do have such libraries), it is relatively straightforward to add support for a camera, as GCX has cleanly defined camera interface. Likewise, many mount/telescope manufacturers use the LX200 protocol, so essentially what is needed for other telescopes/mounts is tetsing and maybe a little tweaking. The program only uses a few LX200 functions, so interfacing to even a custom mount should be easy.

Third, there's the bane of free software: documentation. Any help in documenting or checking the documentation of the program is greatly appreciated, and will go a long way towards keeping GCX users happy.

And finally, the fun part: the code itself. There are many clever algorithms that can be added to the program, and which will benefit from the general infrastructure and integration provided by GCX .

About this Manual

This manual is work in progress. It starts with a tutorial introduction, so people can get a taste of what GCX is all about. The focus in that section is on operations that don't involve particular hardware (image viewing and data reduction).

What gets written next depends on feedback from users. Some aspects of the program's operation are self-explanatory, while some may be a little quircky. Ask for information, and it shall be provided.

The manual is maintained in LATEX

Related Projects

cpxctrl
the camera server used by GCX . Currently it supports the cpx3m camera, but should be easy to modify to control different ones;
cpx3m
a free CCD camera design;
avsomat
a batch variable star reduction program; more portable than GCX it shares some code, but uses a different field-matching algorithm. Avsomat and GCX use the same recipy format.
xephem
The well known planetarium program by Elwood Downey. GCX uses the same object databse format as xephem, namely (.edb), as well as the same WCS annotation FITS fields. The star search algorithm is also inspired from xephem.
libnova
A library for celestial mechanics and astronomical calculations; GCX uses some sidereal time and equatorial-to-horizontal coordinates transformation routines from libnova.


next up previous contents
Next: A Tutorial Up: GCX User's Manual Previous: Contents   Contents
Radu Corlan 2004-01-12