Informations on C2A Software

User InterfaceStar CataloguesDeep Sky CataloguesFeatures


C2A has been designed to answer the following objectives:

User Interface

C2A has a simple and user friendly interface. The image on the left describes the main interface elements which are available to the user in the main window of the program.

A first important thing must be noted in the main window. This is the type of the map which is displayed in the top left corner of the current view. C2A can display two types of map: those with a field type for which the North Celestial pole is by default in the direction of the top of the screen (it is possible to perform rotations and symmetries), and those of type horizon for which the map is oriented in such a way that the closest horizon point is in the direction of the bottom of the screen. In the example on the left, the view has the type field with the North Celestial pole at the top of the screen.

The second important point to be noted is the presence of the two small LEDs in the status bar at the bottom of the main window. They actually display the status of the filters for the stars (left one, which only apply to magnitudes) and deep sky objects (right one, which apply to both magnitude and object type). Green means that there is no filter in action, i.e. all the objects are displayed. Yellow indicates that an automatic filter is currently applied which depends on the zoom level. Finally, red means that a manual filter has been set by the user. A gray LED indicates that there is no catalogue displayed (respectively for stars and deep sky objects).

Identifying an object in the current map can easily be done through a double-click on the object with the mouse left button. To search an object by its name, the user just has to type the string to be searched into the Quick Search zone located at the top left corner of the program window. The search is launched simply by hitting ENTER on the keyboard.

Many options are available to parameterize the views. All these options are gathered into a single dialog box which has several tabs. This option dialog box cand be accessed from the Tools menu or through the keyboard shortcut F7.

Some of the options from the dialog box are also directly accessible from the program menu or through keyboard shortcuts, e.g. the display of constellation lines or the database to use in the maps.

The tab Date allows the user to specify the date to be used to compute the map and the tab Location specifies the observation location in latitude and longitude. The tab Paths is also important as it is the way to indicate C2A where its object databases are located, in particular the large star catalogues which are not provided with the standard distribution of C2A and that need to be installed separately on the user's computer.

C2A can display stars under the form of colored disks or under the form of synthetic stars that reproduce the aspect of stars that can be obtained on a CCD image.

Toggling between the two types of display can be done through the option dialog box or simply using the Ctrl+Y keyboard shortcut.

Star Catalogues

C2A is able to read and display objects from several catalogues. The links in the table below give access to snapshots of the same field with the different catalogues which are supported by C2A (only the GCVS, WDS, Loneos, ArasBeAM and Exoplanet Transit Database catalogues are displayed with a larger field where all the Orion constellation is displayed). Using the same field gives an idea of the respective star density for each catalogue. This field is centered on coordinates Alpha=3h38m / Delta=-35°33 and has a 2° width. It includes several bright galaxies which are displayed in all the fields.

In the descriptions below, a color code is used to indicate where each catalogue can be found:
  The catalogue is part of the C2A standard distribution (it is provided in a format specific to C2A)
  The catalogue is optional and must be downloaded from the C2A Web site (it is provided in a format specific to C2A)
  The catalogue must be obtained from the institution which publishes it (it is read by C2A in its native format)
  The catalogue is directly accessed through Internet (it is read by C2A in its native format)
  The catalogue must be obtained from the institution which publishes it and must then be compiled to be used by C2A.

Red boxes in the catalogue descriptions below provide information about how some key large catalogues (the ones recommended for astrometry) must look like when installed on your local computer hard disk drive. In particular, the exact sizes of some data files are provided in order to validate a catalogue installation on your PC.

SAO Catalogue 
The Smithsonian Astrophysical Observatory Star Catalog (SAO) is a star catalogue that reaches magnitude 11.9. It contains 258,997 objects.

Hipparcos Catalogue 
C2A is also able to read the Hipparcos catalogue that gives positions, proper motions, BT and VT magnitudes as well as other information for 118,218 stars. It includes positions, proper motions, magnitudes BT and VT as well as other detailed information.

Guide Star Catalogue  
The Guide Star catalogue (version 1.1) contains 18,839,509 stellar and non stellar objects. Also known as the Hubble Space Telescope, Guide Catalogue (HSTGC), it has been compiled initially to perform the pointing of the Hubble space telescope. Stars in the catalogue have a magnitude between 6 and 15.

C2A is also abale to read the versions 1.2 and ACT of the Guide Star catalogue, but these catalogues are not provided with C2A and must be sourced separately.

 The Guide Star ACT catalogue can be downloaded from this FTP page at the CDS Strasbourg.

Tycho-2 Catalogue 
The Tycho-2 catalogue gives positions, proper motions, BT and VT magnitudes for 2.5 millions stars (2,558,647 exactly) all over the sky. C2A takes into account proper motions to calculate object positions at a given epoch. All the required information about the Tycho-2 catalogue can be obtained from Erik Høg's Web site. It must be noted that, in order to be used with C2A, the Tycho-2 catalogue must be compiled first. The Tycho-2 catalogue can be downloaded in the C2A format from the Downloads page.

USNO-SA1.0 and USNO-A2.0 Catalogues 
The USNO-SA1.0 contains 488,006,860 stars. This catalogue is published under the form of a CD-ROM by the US Naval Observatory. It represents a very good astrometric reference for asteroid hunters. This catalogue is a simplified version of the USNO-A1.0 catalogue. The catalogue USNO-A2.0 contains 526,280,881 stars. The main difference with the USNO-SA1.0 is that the later one makes use of the Guide Star catalogue for its reference fields while the A2.0 makes use of the ICRF catalogue.

USNO-B1.0 Catalogue 
The USNO-B1.0 catalogue covers the whole sky with positions, prper motions and magnitude in various bands for 1,042,618,261 objects derived from 3,643,201,733 separate observations. Data has been obtained from the scan of 7,435 images which are the result of various observations campains. C2A can access the USNO-B1.0 catalogue directly on the Internet and there is no need to have a local copy of this catalogue.

UCAC1 Catalogue 
The UCAC1 catalogue is an astrometric catalogue with a position accuracy of 20 mas for magnitudes between 10 and 14 (and 70 mas above magnitude 16). Proper motions are provided for each object and they are taken into account by C2A for computing object positions at a given epoch. The first version of the catalogue (UCAC1) covers 80% of the Southern Hemisphere. It can be obtained by going to the USNO site. This catalogue contains 27,425,433 stars. It must be noted that, in order to be used with C2A, the UCAC1 catalogue must be compiled first. The compiler is provided in the Downloads page of this site.

UCAC2 Catalogue 
C2A is also compatible with a newer version of the UCAC catalogue which is the UCAC2 edited by the US Naval Observatory. This catalogue contains more than 48 millions stars and covers all the Southern Hemisphere as well as a large part of the Northern Hemisphere (-90 to +40° of declination) for magnitudes ciomprised between 8 and 16. It must be noted that, in order to be used with C2A, the UCAC2 catalogue must be compiled first. The compiler is provided in the Downloads page of this site.

UCAC3 Catalogue 
C2A can read the native version of the UCAC3 catalogue (Third U.S. Naval Observatory CCD Astrograph Catalog). The UCAC3 catalogue, edited by the U.S. Naval Observatory, is an all-sky star catalogue covering mainly the 8 to 16 magnitude range in a single bandpass between V and R. Positional errors are about 15 to 20 mas for stars in the 10 to 14 mag range. It is supplemented by proper motions and SuperCosmos and 2MASS photometric data, as well as various flags. The catalogue takes includes proper motions and has more than 140 millions objects. It must be noted that it is not necessary to compile the UCAC3 catalogue to read it in C2A (as opposed to the UCAC2). The native format can be directly read in C2A.

 The catalogue UCAC3 can be obtained from the CDS Strasbourg site at this FTP page (caution, the files must be uncompressed and named according to the indications below). It is read by C2A in its native format and takes 7,9 gigabytes on disk.

The catalogue is made of 360 files names z001 to z360 (each zone is 0.5 degree wide). The files u3index.unf and table_zones must also be present in the same folder as the one containing the 360 data files. The access path to the folder that contain all the UCAC3 files must be declared in the Paths tab of the C2A option dialog box. Here are the exact sizes of some files:

z001: 105,672 bytes      z002: 321,552 bytes
z359: 179,088 bytes      z360:  77,112 bytes

UCAC4 Catalogue 
C2A can read the native version of the UCAC4 catalogue (Fourth U.S. Naval Observatory CCD Astrograph Catalog). The UCAC4 catalogue, edited by the U.S. Naval Observatory, is an all-sky star catalogue covering mainly the 8 to 16 magnitude range in a single bandpass between V and R. Positional errors are about 15 to 20 mas for stars in the 10 to 14 mag range. Proper motions have been derived for most of the about 113 million stars utilizing about 140 other star catalogs with significant epoch difference to the UCAC CCD observations. These data are supplemented by 2MASS photometric data for about 110 million stars and 5-band (B,V,g,r,i) photometry from the APASS (AAVSO Photometric All-Sky Survey) for over 50 million stars. UCAC4 also contains error estimates and various flags. All bright stars not observed with the astrograph have been added to UCAC4 from a set of Hipparcos and Tycho-2 stars. Thus UCAC4 should be complete from the brightest stars to about R=16, with the source of data indicated in flags.

 The catalogue UCAC4 can be obtained from this FTP page (caution, the files must be put in sub-folders and named according to the indications below). It is read by C2A in its native format and takes 8.5 gigabytes on disk.

The catalogue is made of 900 files names z001 to z900 (each zone is 0.2 degree wide). All these data files must be stored in a sub-folder called u4b. The files u4index.unf and zone_stats must also be present in a sub-folder called u4i at the same level as the sub-folder u4b. The access path to the folder that contain the two sub-folders u4b and u4i must be declared in the Paths tab of the C2A option dialog box. Here are the exact sizes of some files:

z001: 16,068 bytes      z002: 51,480 bytes
z899: 39,936 bytes      z900: 13,338 bytes


A Python script is available to automaticaly transfer the 900 binary data files and 2 index files. To use it, make sure that Python 3 is installed on your computer (see Download Python), download the script, put it the folder that will host the UCAC4 catalogue, open a command window and type 'python transfer_UCAC4.py'. Depending on your Internet connection bandwidth, transferring all the files may take a while... Once this is done, launch C2A, go into the Options dialog box then 'Paths' tab and declare the access path (in the UCAC4 zone) to the folder where you have downloaded the files.

NOMAD Catalogue 
C2A is able to read the NOMAD catalogue (Naval Observatory Merged Astrometric Dataset). This catalogue has been assembled in 2005 and groups together the catalogues Hipparcos, Tycho-2, UCAC2, USNO-B1.0 and 2MASS. It contains 1,117,612,732 objects (more than a billion!) down to magnitude 21, representing around 80 gigabytes of data. It must be noted that C2A is able to read both the full version of the catalogue and the reduced version. Furthermore, it is not necessary to compile the catalogue, i.e. C2A reads the native catalogue.

 The catalogue NOMAD must be obtained from a user who already owns it as it cannot be downloaded from the Internet due to its size. This catalogue is read by C2A in its native format and takes 92 gigabytes on disk.

The catalogue is made of 1,800 files split in 180 folders named 000 to 179 (each folder covers a zone 1 degree wide). Each folder contains data files, accelerator files and index files with the respective extensions .cat, .acc and .inx. File names have the form mxxxx.yyy where xxxx is a 4-digit number and yyy the extension. The access path to the folder that contain the 180 sub-folders must be declared in the Paths tab of the C2A option dialog box. Here are the exact sizes of some files:

m0000.cat: 32,912  m0000.acc: 2,880  m0000.inx: 7,204
m1799.cat: 33,704  m1799.acc: 2,880  m1799.inx: 7,204


A short version of the NOMADcatalogue is also available which is organized with the same structure as the regular catalogue but without accelerator files. Here are the exact sizes of some files:

m0000.cat: 1,496   m0000.inx: 7,204
m1799.cat: 1,232   m1799.inx: 7,204

PPMXL Catalogue 
C2A is able to read the PPMXL catalogue. PPMXL is a catalogue of positions, proper motions, 2MASS- and optical photometry of 900 million stars and galaxies, aiming to be complete down to about V=20 full-sky. It is the result of a re-reduction of USNO-B1 together with 2MASS.

 The catalogue PPMXL must be obtained from a user who already owns it as it cannot be downloaded from the Internet due to its size. This catalogue is read by C2A in its native format and it takes 147 gigabytes on disk.

The catalogue is made of 720 text files named xyyz where x is the character n (for the Northern hemisphere) or the character s (for the Souther hemisphere), yy is a number on 2 digits between 00 and 89 and z a character that takes a value between a and d (every file covers a zone 7,5' wide in declination). The access path to the folder containing the 720 files must be declared in the Paths tab of the C2A option dialog box. Here are the exact sizes of some files:

n00a.dat: 242.862.936    n00b.dat: 234.323.886
s89c.dat:   1.057.746    s89d.dat:     348.522

GCVS Catalogue 
C2A standard distribution includes the GCVS catalogue (General Catalogue of Variable Stars). This catalogue does not need to be downloaded separetaly. It include 40,215 objects in its current version. This comprises the digital version of the GCVS4 Vols. I-III catalogue (Kholopov and al. 1985-1988) as well as the "Name-Lists of Variable Stars" Nos.67-78 published during the preparation of the 4th edition of the GCVS catalogue. All the required information on the GCVS catalogue can be found here.

WDS Catalogue 
C2A integrates in its standard distribution the Washington Double Star Catalogue (WDS) maintained by the United States Naval Observatory. It is the world's principal database of astrometric double and multiple star information. The WDS Catalogue contains positions (J2000), discoverer designations, epochs, position angles, separations, magnitudes, spectral types, proper motions, and, when available, Durchmusterung numbers and notes for the components of 103,861 systems. More information can be found here.

Loneos Catalogue 
C2A natively integrates the UBVRI photometry of faint field stars catalogue which is generally called Loneos. This catalogue is well suited to photometry work on large fields. This catalogue was initially developed for the needs of the Lowell Observatory Near-Earth Object Search (LONEOS) program. It contains a collection of photometric Johnson-Cousins UBVRI data. More information can be found on the Strasbourg CDS web site (II/277). There are 34,071 objects in the catalogue.

ArasBeAM Catalogue 
ArasBeAM is a catalogue that allows to coordinate spectral observations on Be Stars for all the amateurs worldwide. C2A automatically loads an updated version of the catalogue from the Internet on a regular basis and displays the catalogue objects with their observations priorities.

Exoplanet Transit Database 
The Exoplanet Transit Database is a catalogue which lists all the known exoplanets that can be observed through a transit in fromt of their parent star. C2A automatically loads an updated version of the catalogue from the Internet on a regular basis and displays the catalogue objects with their observations priorities.

Meteor Shower Catalogue 
C2A is able to read over Internet the IAU Metor Shower Catalogue. When an object from the Meteor Shower catalogue is identified, the following information is displayed: right ascension and declination of the meteor shower radiant, activity type (usually annual), status of the meteor shower (for instance confirmed or under evaluation), solar longitude at peak of shower (degrees, epoch J2000), date and time of the activity peak, geocentric speed (km/s) before acceleration by Earth's gravity, name of the ârent body, detailed name of the meteor shower, radiant drift in right ascension and declination per day (in degrees) if it is known.

Asterism Catalogue 
C2A integrates an asterism catalogue. This catalogue does not need to be downloaded separetaly. It is based on the Saguaro Astronomy Club Asterisms Database version 3.0 and the Deep-Sky Hunter's Field Guide, Part 5, Asterisms, version from November 2010.

Gliese Catalogue 
C2A integrates the Gliese catalogue. This catalogue has the objective to list all the stars within 25 parsecs from the Sun (with a parallax greater than or equal to 0.0390 arcseconds).

CMC15 Catalogue 
C2A is able to read the Carlsberg Meridian Catalogue CMC15 catalogue. It is an astrometric and photometric catalogue of more than 122.7 million stars in the red magnitude range 9 to 17. The latest release of the catalogue covers a declination range between -40° and +50°. Oservations have been made between March 1999 and March 2011.

URAT1 Catalogue 
C2A is able to read the URAT1 catalogue (First U.S. Naval Observatory (USNO) Astrometric Robotic Telescope Catalog). This catalogue covers most of the northern hemisphere and in some areas as far south as -24.8 deg Dec (Pluto field). It covers the about R = 3 to 18.5 magnitude range with positional precisions of 5 to 40 mas depending on observing history and brightness of stars. It was constructed from 2 years of operations of the astrograph at the Naval Observatory Flagstaff Station (NOFS). URAT1 is supplemented by preliminary proper motions derived exclusively from 2-epoch URAT1 and Two Micron All Sky Survey (2MASS) data (at around epoch 2000) resulting in proper motion errors of typically 5 to 8 mas/yr. The catalogue contains 228 millions objects (mostly stars) of which 188 million are common to 2MASS.

 The catalogue URAT1 can be btained from this FTP page. It is read natively by C2A and it takes 17 gigabytes on disk.

The catalogue is made of 575 files named z326 to z900. The index files v1index.asc and v1index.unf must be present in the same folder as the data files. The access path to the folder that contains the catalogue must be declared in the tab Paths of the C2A Option dialog box. Here are the sizes of some files from the catalogue for reference:

z326: 11,760 bytes        z327: 1,134,720 bytes
z328: 1,524,640 bytes     z329: 2,164,640 bytes


A Python script is available to automaticaly transfer the 575 binary data files and 2 index files. To use it, make sure that Python 3 is installed on your computer (see Download Python), download the script, put it the folder that will host the URAT1 catalogue, open a command window and type 'python transfer_URAT1.py'. Depending on your Internet connection bandwidth, transferring all the files may take a while... Once this is done, launch C2A, go into the Options dialog box then 'Paths' tab and declare the access path (in the URAT1 zone) to the folder where you have downloaded the files.

Deep Sky Object Catalogues

C2A natively integrates several catalogues of deep sky objects. The table belows provides descriptions of these deep sky object catalogues. The links point to screen snapshots which show these different catalogues in the same field (this field is centered on coordinates Alpha=3h38m / Delta=-35°33 and has a 2° width)./p>

In the descriptions below, a color code is used to indicate where each catalogue can be found:
  The catalogue is part of the C2A standard distribution (it is provided in a format specific to C2A)
  The catalogue itself is provided in the C2A standard distribution but the associated images must be downloaded from the Web site.

Revised New General Catalogue and Index Catalogue 
C2A is provided with the Revised New General Catalogue and Index Catalogue (crédit Wolfgang Steinicke - see the site Revised New General Catalogue and Index Catalogue). This Deep Sky objects catalogue includes all the objects from the original NGC and IC catalogues as compiled by Dreyer. Furthermore, it includes a certain number of additional objects (named using extension letters A, B, C, ...). This leads to 13,993 objects in this catalogue.

Deep Sky Object Catalogue 
One of the two Deep Sky object catalogue provided with C2A includes: the Messier catalogue, the NGC catalogue and the IC catalogue. This catalogue is built from the original Revised New General Catalogue well know by the astronomers community. It is enhanced with the NGC 2000 catalogue in order to get some object sizes.

PGC Catalogue 
The PGC catalogue (Catalogue of Principal Galaxies), also called PGC 2003, is derived from the HYPERLEDA database. This version of the catalogue is restricted to confirmed galaxies, which represents around 1 million galaxies brighter than magnitude 18 in the blue. Alternate names of the objects are also provided. It must be noted that no magnitude is provided for the objects, and therefore filters on magnitude are not effective.

BT-Atlas Catalogue 
C2A is able to read the BT-Atlas catalogue (credit Christian Buil) and to display all the associated images. It is a unique set of 4649 images representing 6600 deep sky objects. All these images were acquired using CCD cameras. There are 5002 galaxies, 284 galaxy clusters, 654 open clusters, 136 globular clusters, 155 planetary nebulae, 279 diffuse nebulae and et 90 dark nebulae.

SAC Catalogue 
The SAC catalogue version 8.1 is edited by the Saguaro Astronomy Club). It has been compiled for C2A and it is released with the software for an easy usage (credit Saguaro Astronomy Club). It contains 10,342 objetcs with some detailed information attached to them: name, alternate names, type, magnitude, constellation the objects belong to, equatorial position J2000, Uranometria 2000.0 page number where the object can be found, Tirion Sky Atlas 2000.0 page number where the object can be found, object size, orientation on the sky, object class, number of stars in cluster, magnitude of the brightest star in cluster, NGC description and associated notes.

In addition to the deep sky object catalogues mentioned above, C2A has the capability to access the images of the Digitized Sky Survey (DSS) from the ESO and STScI and to display these images in a separate window or in the background of the current field. In this version, the access to the DSS is only performed through Internet on the ESO DSS server or STScI server. In order to access these images, your platform must be connected to the Internet.

This screenshot on the right shows a field map (the same as in the examples above but with a field limited to 40 arcminutes) with the ESO DSS image in the background and the object from the Tycho-2 and RNGCIC catalogues in the front-end. We can there is a very good matching between the objects in the image and the objects from the catalogue.

The DSS image download is very easily performed with one mouse click (Ctrl+F8 is a keyboard shortcut) when the field is smaller than 40 arcminutes (in order to limit the size of the download). Once an image is downloaded, it can then be modified and reapplied as the current map background.

Features

C2A includes many features and functions which can be summarized in the table below. Simply click on links to access some screenshots.

Milky Way display

C2A displays the Milky Way whatever is the zoom level. Bézier curve computing is performed in order to render curved shapes.

Nebulae display

When the RNGCIC (Revised New General Catalogue and Index Catalogue) catalogue is the currently displayed catalogue, a certain number of diffuse nebulae are displayed with their real shape. The display of nebulae's shapes depends on both the zoom level and the filters in place for the deep sky objects. Some shapes are directly associated to NGC and IC objects (in which case they are displayed in light green) while others are not related to any specific NGC or IC objects (they can typically include several NGC and IC objects, in which case they are displayed in dark green).

Solar System

Regarding the Solar System, positions computing of the Sun, Moon and planets are performed using some special algorithms from the Institut de Mécanique Céleste (Bureau des Longitudes) in Paris. Polynomial coefficients used in these algorithms provide a very high accuracy on object positions (1/100 arc second over the period 1987/2020, which can be extended to 2100 using the polynomial coefficient file available in the Downloads page of this site). The screenshot shows Venus path with a retrogradation at the top of a synthetic sky background.

Ecliptic View

C2A integrates a tool to view planet, asteroid and comet positions according to an ecliptic view (accessible from the Tools menu). It is possible to easily change the angle of view as well as the zoom level using the mouse. Furthermore, an animation mode is available.

Ephemeris Production

C2A includes a full Ephemeris production system (Moon, Sun, planets as well as comets and asteroids known through their orbital elements). The output step can be adjusted and the produced ephemeris can be saved under the form of a text file or directly printed.

Moon Phases

C2A includes a module to compute and display Moon phases for a given month. Furthermore, dates of Full Moon, New Moon, First Quarter and Second Quarter are specifically provided.

Asteroids and comets

C2A includes a powerful system to compute asteroid and comet position calculation from their orbital elements. A Graphical User Interface allows the user to import and handle orbital elements. It is possible to import orbital elements directly from the Internet, for instance from the Minor Planet Center site. Several different orbital elements formats are supported. Once the orbital elements are loaded, it is then possible to plot the positions or trajectories of the objects.

Planetary Positions

C2A gives the possibility to display planetary positions at 3 different dates for a given month. This display is performed either at the beginning, middle or end of the night. It is done on a map with constant azimut and altitude. This is a useful tool to see at a glance what are going to be the observing conditions for a given object during a given month. It is possible to parameterize the display through numerous options.

Proper Motions

C2A is able to take into account proper motions for the stars in the catalogues UCAC1, UCAC2, UCAC3, Hipparcos and Tycho-2. The associated image shows the successive positions of the Barnard's star between 1959 and 2030. This animated image has been created with the UCAC2 catalogue.

Image Processing

C2A integrates an image processing tool where the most common tasks around astronomical images can be performed: contrast display, visualization threshold setting, color palette changes, zoom, printing, ... Several different formats are taken into account, either formats with visualization dynamics (FITS, CR2, PPM, PGM and PIC the format of the Iris software), or formats without visualization dynamics (JPG, GIF, BMP). Beside these basics features, C2A has several advanced features: automatic astrometry on a field using the PinPoint engine, image acquisition through the Maxim DL software and a camera focus tool.

User Images

The user has the possibility to add its own images in the C2A environment. Once one or several images are associated to a given object (for instance a Messier or an NGC object), access to those images is performed through the button Image... in the information window displayed for that object. The command Image... in the contextual menu can also be used (this menu is displayed with the mouse right button when an object with an associated image is pointed). Object types to which images can be associated to are the following: deep sky objects from the standard deep sky, PGC and RNGCIC catalogues, SAO stars, user objects, Tycho2 star, UCAC1, UCAC2 and UCAC3 stars, ArasBeAM stars, Hipparcos, GCVS, WDS or Loneos stars, planets, Moon, Sun and satellites. User can also associate a text of his/her choice to a given image (for example some comments about how the image was acquired). This text is then automatically displayed in an information box associated to the image. All the images must be stored in a directory declared in the Path tab of the Options dialog box. The first image associated to an object must be named according to the pattern [object name]_1.[extension] where [object name] is the name of the object displayed in the information window and [extension] is the file extension associated to one of the supported image formats (fit, fts, fits, pic, jpg, gif and bmp ). For example, the first JPEG image associated to the object NGC 1972 must be named NGC 1972_1.jpg. The second one must be named NGC 1972_2.jpg, etc...

Printing

Maps, ephemeris and pictures can be printed on all the printers supported by the Windows Operating System. Several options are possible to improve printing results as shown in the associated image. To see a printing result in the PDF format, click here.

Prepoint Track

C2A includes a simple tool to position a telescope on the sky in such a way that at a given time, a pre-defined object is at the center of the field pointed by the telescope. This function, called prepointing, is especially useful in the scope of occultations of stars by asteroids where, several minutes or hours before the event, the telescope is put in position with the RA tracking stopped. The star will drift in the field of view until it reaches the center at the target time.

Telescope Control

C2A offers the possibility to control a telescope through a serial port. By controlling, we mean the following features:

  • Display the telescope position in Right Ascension and Declination in the software Hand Controller;
  • Display current telescope position under the form of a target in the current map;
  • Possibility to calibrate the telescope controller from C2A (i.e. indicate to the telescope controller which point in the sky it is currently pointing at);
  • Possibility to move the telescope (slew) to a specific target, either by providing the coordinates (Right Ascension and Declination) or by pointing an object in the current map.
Supported telescopes are the following:
  • All the telescopes and focusers compatible with the ASCOM standard (see http://ascom-standards.org/);
  • Telescope Meade LX200 (or any other telescope that supports the standard native LX200 protocole). C2A has been validated on an LX200 / 2 - version 3.30L and version 4.341L (AltAz mode);
  • Astro-Physics GTO controller;
  • SkySensor 2000 PC controller. C2A has been validated on a SkySensor 2000 PC version 2.10;
  • Gemini Pulsar controller;
  • AudeCom controller.

Tracking Drift Analysis

C2A includes a tool to analyze and plot tracking drifts for telescope mountings. In its current version, C2A is able to read data files produced by the Iris software (see Iris web site), Maxim DL, GuideMaster, CCDSoft and AstroArt. C2A offers the user the possibility to "zoom" on some parts of the plot and to copy an image of the plot for future usage. To use this tool, go into the Telescope menu and use the command Tracking Drift Analysis...

Focus Tool

C2A includes a tool to help focusing a telescope. This tool is accessible from the Image Processing window once a star has been selected with the mouse. User then simply has to click the Focus button in the tool bar. This tool allows the user to easily see how focus evolves while focus images arrive in a pre-defined directory during the focus process. Focus is plot dynamically through an automatic analysis of the in-coming images.

Observation Planning

C2A lets you plan your observations by finding objects meeting a number of criteria. These are the available types of criterion:

  • The magnitude of the object;
  • The type of object;
  • The size of object;
  • Position within the current map;
  • The azimuth and elevation at the time of the current map;

Once the objects are identified, they can be highlighted in the maps and the telescope can be automatically pointed towards these objects.

Observation Scheduling

C2A includes a tool that lets you put together an observation schedule. It is a list of observations in a certain order that starts at a precise day and time. This tool is different from the Observation Planning tool which is just used to identify objects that meet certain criteria.

Planet Visibility

C2A includes a tool that allows you to figure out at a glance what is the visibility during the night of the planets and the moon. Various options are available to customise the display.

Sunrise and Sunset

A specific tool let you easily get for a specific date the times for sunrise, sun meridian transit, sunset as well as the times of the Astronomical Twilight (Sun at -18° below the horizon), Nautical Twilight (Sun at -12° below the horizon) and Civil Twilight (Sun at -6° below the horizon). Twilights are provided for both sunrise and sunset.

Last Update : November 2, 2015
Author : Philippe Deverchère