If it is the first time you download C2A, you just need to get the most recent full version of the software (use the first link in the Distributions section below). All what you need in a first time is included in the distribution package.
In addition to the distribution packages of C2A, this page provides you with a certain number of downloads:
The most two recent versions of C2A are available for download in this section. It is advised to install the latest version, the other one being here in case of a regression is found in the most recent version.
|Most Recent Version||April 3, 2016|
|Version 2.1.2 - full distribution||40.8 MB||Full distribution in English (1)|
|Version 2.1.2 - update||5.5 MB||Update to version 2.1.2 (2)|
New features in version 2.1.2
|Version before the most recent version||November 2, 2015|
|Version 2.1.1 - full distribution||40.7 MB||Full distribution in English (1)|
|Version 2.1.1 - update||5.4 MB||Update to version 2.1.1 (2)|
New features in version 2.1.1
|Version before the most recent version||January 26, 2015|
|Version 2.1.0 - full distribution||40.1 MB||Full distribution in English (3)|
To install C2A on your system, simply "unzip" the content of the ZIP file into a temporary folder, then launch the executable setup.exe. Finally, follow the different steps of the installation procedure as proposed by the installation software.
This section allows you to download orbital elements files so that they can be imported in the C2A Asteroids and Comets tool. These orbital elements are updated on a regular basis. It is recommanded however to use the automatic importing function which is available in the Asteroids and Comets tool rather than downloading the orbital elements manually.
All the orbital elements provided in this page are in the C2A format (which is a very simple text format). To download these files on your computer, make a mouse right click on the links, then use the Save as... command.
Last Update: April 3, 2016
|500 First Asteroids|
The file ast_500.c2a contains orbital elements for the 500 first asteroids (obtained from the site of the Bowell Catalogue). The URL that can be used directly within C2A is:
|1000 First Asteroids|
The file ast_1000.c2a contains orbital elements for the 1000 first asteroids (obtained from the site of the Bowell Catalogue). The URL that can be used directly within C2A is:
|2000 First Asteroids|
The file ast_2000.c2a contains orbital elements for the 2000 first asteroids (obtained from the site of the Bowell Catalogue). The URL that can be used directly within C2A is:
The file ast_brgt.c2a contains the orbital elements of the bright asteroids at opposition in the current year (obtained from the Minor Planet Center site). The URL that can be used directly within C2A is:
The file ast_crit.c2a contains orbital elements for the critical asteroids (obtained from the Minor Planet Center site). The URL that can be used directly within C2A is:
The file ast_nea.c2a contains orbital elements for distant asteroids (obtained from the Minor Planet Center site). The URL that can be used directly within C2A is:
The file ast_dist.c2a contient les éléments orbitaux des astéroïdes distants (obtenus depuis le site du Minor Planet Center). The URL that can be used directly within C2A is:
In order to load the orbital elements provided in this page, simply use the Import dialog box of the C2A Asteroids and Comets tool (which can be displayed using the button Import... of the Asteroids and Comets tool dialog box). Once this dialog box is displayed, simply specify the name of the file to be imported (assuming it has been saved locally on your disk) or use directly the URLs proved above.
Pay special care to correctly position the Asteroid and Comet buttons before starting the importation process. Furthermore, you must check that the import format is in accordance with the format of the file to be imported (in our case it is the C2A format).
|Large C2A Catalogues|
|Tycho-2 Catalogue||152 MB|
This ZIP file contains the Tycho-2 catalogue in the C2A format and must be decompressed to be used by the program. This version includes the two supplement catalogues. It also corrects a problem with the stars from the supplement catalogue (found on the 1st of May 2007).
|Guide Star Catalogue version 1.1||131 MB|
This ZIP archive contains the Guide Star 1.1 catalogue in its compiled format for C2A. The files in the ZIP file must be uncompressed into a folder (named GSC for instance) preserving the sub-directory structure. This version of the catalogue is provided for historic reasons, but it is advised to use instead the version 1.2 of the Guide Star catalogue (see below).
|Guide Star Catalogue version 1.2||232 MB|
This ZIP archive contains the Guide Star 1.2 catalogue in its native format. The files in the ZIP file must be uncompressed into a folder (named GSC for instance) preserving the sub-directory structure. It is advised to use this version of the Guide Star catalogue. It allows in particular to perform searches on the object names.
|BT-Atlas Images||620 MB|
All the BT-Atlas images are available in this ZIP archive in the PIC format (the format from the well known Iris image processing software) with all their dynamic. The files in the ZIP file must be uncompressed into a folder (named BT-Atlas for instance) preserving the sub-directory structure. The author wants to thank Christian Buil for having given free access to this great image catalogue.
To download these files on your computer, make a mouse right click on the links, then use the Save as... command. Once these catalogues are downloaded on your disk drive, you must declare the access paths in the tab Paths of the Options dialog box (F7 keyboard shortcut within C2A).
|Reduced UGC Catalogue||15 KB|
Text catalogue example in the C2A format.
To download this file on your computer, make a mouse right click on the link, then use the Save as... command.
The syntax of text catalogues is described in the C2A Help system. Text catalogues usually have the extension ".c2a". Text catalogues can be loaded in C2A using the command User Catalogues... from the File menu.
|4th Uhuru Catalogue||4U.ccc||30 KB|
|Abell Clusters of Galaxies||Abell.ccc||198 KB|
|Arp Atlas of Peculiar Galaxies||Arp.ccc||17 KB|
|Bonner Durchmusterung Catalogue||BD.ccc||16 MB - ZIP file|
|Flat Galaxy Catalogue||FGC.ccc||386 KB|
|Fifth Fundamental Catalogue||FK5.ccc||158 KB|
|General Catalogue of Variable Stars||GCVS.ccc||3.7 MB|
|Hickson Galaxy Cluster Catalogue||Hickson.ccc||7 KB|
|Hipparcos Input Catalogue||Hippar.ccc||9.9 MB|
|High Velocity Stars||HVS.ccc||52 KB|
|Lynds' Catalogue of Bright Nebulae||LBN.ccc||61 KB|
|Lynds' Catalogue of Dark Nebulae||LDN.ccc||134 KB|
|UBVRI photometry of faint field stars||Loneos.ccc||3.7 MB|
|MBrphological Catalogue of Galaxies||MCG.ccc||2.5 MB|
|Merged Catalogue of Galaxies||MERCG.ccc||2.7 MB|
|New Suspected Variables||NSV.ccc||3 MB|
|Open Cluster Data||OPENCL.ccc||55 KB|
|Galactic Planetary Nebulae||PLN.ccc||83 KB|
|Northern PPM Catalogue||PPMNORTH.ccc||25 MB - ZIP file|
|Southern PPM Catalogue||PPMSOUTH.ccc||20 MB - ZIP file|
|Ruprecht Star Clusters||Ruprecht.ccc||9 KB|
|Sharpless HII Catalogue||HII.ccc||15 KB|
|Galactic Supernova Remnants||SNR.ccc||11 KB|
|Uppsala General Catalogue||UGC.ccc||1.4 MB|
|Washington Visual Double Stars||WDS.ccc||4.3 MB|
|Zwicky Clusters of Galaxies||Zwicky.ccc||611 KB|
To download these files on your computer, make a mouse right click on the links, then use the Save as... command.
The C2A catalogue compiler can be downloaded from this same page (section Compilers). It is a simple executable that must be run from the Windows Command Line. All the necessary steps to create a compiled catalogue are described in the C2A Help System. Compiled catalogues must have the extension ".ccc". Compiled catalogues can be loaded in C2A using the command User Catalogues... from the File menu.
User Catalogue Compiler
Text user catalogues are useful when catalogues are not too big. However, for large catalogues, loading time within C2A et screen refresh become prohibitives.
C2A offers the possibility to compile an object catalogue. This means that a binary file can be produced from an ASCII file whose syntax is described by the user. This binary file can then be loaded and displayed much faster within C2A. Furthermore, users have the ability to define their own fields whose value is displayed when objects are identified within the maps.
For a text database to be compiled, the user has to provide a certain number of information in a text file called a "model file". This information will allow the database compiler to figure out which data is to be extracted from the ASCII file and used to produce the compiled file.
The database compiler for C2A is called DC and must be launched from the Windows Command Line. In order to install the compiler and use it, first download the file DC.zip using the link on the left, uncompress it, and copy the executable file DC.EXE in a directory of your choice. Then open a Windows command line (go into the Start menu, choose Execute..., then type cmd followed by OK). Go then into the directory where the DC compiler has been installed. Here, the compiler can be used using the directions provided in this short Compiler User Guide (in English).
Note: The old DOS version 1.0.18 of the User Catalogue Compiler (which does not work on Windows 7 64 bits) is also available here.
Compiler for the UCAC1 Catalogue
The UCAC1 catalogue is published by the US Naval Observatory under the form of a CD-ROM that contains a file called u1.tar.gz. In order to be efficiently used by C2A, this catalogue must be compiled first. To compile the UCAC1 catalogue, simply go through the following process:
The compilation process takes around 30 minutes on Core i5 computer (or 2 hours and 3 minutes on a Pentium III computer at 1 GHz...). The output file (for instance UCAC1.DAT) has a size of roughly 889 megabytes. Store it in a directory of your hard disk drive then specify the access path within C2A by going into the tab Paths of the Options dialog box (accessible from the menu Tools/Options...). This access path could be for instance "D:\UCAC1\UCAC1.DAT" assuming that a directory "UCAC1" has been created directly on the C: drive root. The compiled file must be exactly 932,468,278 bytes
C2A is now ready to read the UCAC1 catalogue!
Note: The old DOS version 1.0.0 of the UCAC1 compiler (which does not work on Windows 7 64 bits) is also available here.
Compiler for the UCAC2 Catalogue
The UCAC2 catalogue is published by the US Naval Observatory under the form of 3 CD-ROMs that contain 288 files named from Z001 to Z288 as well as 36 files for the Bright Star Supplement names s01 to s36. In order to be efficiently used by C2A, this catalogue must be compiled first. To compile the UCAC2 catalogue, simply go through the following process:
The 24 output files (UCAC2_00.DAT to UCAC2_23.DAT) have a size of roughly 2.17 gigabytes. Store them in a directory of your hard disk drive then specify the access path within C2A by going into the tab Paths of the Options dialog box (accessible from the menu Tools/Options...). This access path could be for instance "D:\UCAC2" assuming that a directory "UCAC2" has been created directly on the C: drive root.
The compilation process takes around 1 hour and 30 minutes on Core i5 computer. Once the compilation process is complete, the source files (Z001 to Z288 and s01 to s36) can be deleted from the hard disk.
Note: The old DOS version 1.2.0 of the UCAC2 compiler (which does not work on Windows 7 64 bits) is also available here.
|Polynomial File to Compute Planetary Positions between 1900 and 2100|
Polynomial File wap.b98
This file must be uncompressed and must overwrite the file wap.b98 in the C2A installation directory (by default C:\Program Files\C2A).
|Add-in to Use C2A with Occult Watcher|
Occult Watcher Add-in
Occult Watcher is a software designed to easily manage predictions of star occultation by asteroids. An Add-in is available to directly launch C2A from Occult Watcher and display a map of the occultation event (setting automatically the time, location and catalogue for the considered event). The Hipparcos, UCAC2, UCAC3 and NOMAD catalogues are often used in occultation predictions, so it is necessary to have them installed on your computer before using this Add-in.
Take care that in order to use this C2A Add-in for Occult Watcher, you need at least version 2.0.43 of C2A and the most recent version of Occult Watcher.
To install the Add-in, simply extract the file OccultWatcher.C2a.dll (available in the ZIP file) and copy it into the Occult Watcher installation folder. A C2A entry will then be added in the Occult Watcher Add-in menu. To launch C2A and get the map of an event, select this event in the Occult Watcher list and go into the Add-in menu to create the C2A Occultation Map.
New features in version 1.6 are the following:
|Bright Star Supplement for the UCAC2 Catalogue|
Bright Star Supplement
The catalogue UCAC2 uses 36 files (s01 to s36) containing information on bright stars which must be integrated into the compiled UCAC2 catalogue for C2A. These files are not provided on all UCAC2 distributions. Therefore, they are provided here for download.
|C2A for DOS|
C2A DOS Version 4.1.4
C2A is available in a DOS version which is compatible with all the Windows Operating Systems as well as in a DOSBox emulation which also runs on Mac OS. The advantage is that it can be used on hardware platforms that maybe not be powerful enough to run recent versions of Windows. This tool is therefore perfect to run a simple Planetarium program on an old machine close to the telescope.
By default, C2A for DOS is able to read three star databases (around 2100, 9000 and 260.000 objects) as well as three deep sky objects databases (around 110, 5000 and 8000 objects). All these catalogues are provided with the software. C2A for DOS is able to read the BT-Atlas catalogue (6600 objects) with its 4649 associated images. It is also possible to access the Guide Star catalogue (10 millions objects) as well as the USNO catalogues in different versions (USNO-SA1.0, USNO-A2.0). These large catalogues are not provided with the C2A for DOS distribution.
To install C2A for DOS, download first the file C2AD_414.zip with the link on the left, uncompress it in a temporary directory and run the executable INSTDOS.EXE. Then, simply follow the steps as displayed on the screen. At the end of the installation process, you can delete the files in the temporary directory.
All the documentation about C2A for DOS is available in a file called C2A.PDF provided in the ZIP archive. Take care that this documentation is in French only! Sorry about that, but it would be a tremendous work to translate it...
C2A DOS Version 4.1.5
This is a DOS version of C2A which supports the polynomial file SLP96 from the IMCCE in order to compute planetary positions over the period 1987 - 2020. Version 4.1.4 only supports the period 1987 - 2009.
In order to install this version, install first version 4.1.4 above (if it is not already installed on your computer) then overwrite the files C2A.EXE, C2A.MSG and C2A.B98 with those from the ZIP archive file.