How do you Define your Own Catalogues of Objects?

C2A lets you define your own catalogues of objects as text files. The command User catalogues ... in the File menu allows you to load catalogues and to display them in the field map. Note that C2A also allows you to compile your own catalogues of objects (see the section: How to compile user catalogues of objects).

Users can define their own objects to be displayed in the same way as those in databases supplied with the program.

User objects defined in textual databases are represented by the same symbols as deep sky objects or solar system objects (asteroids, comets, etc…). Have a look at the object symbols section to see the symbols associated with different kinds of objects.

User objects which have an apparent size on the celestial sphere are displayed with circles or ellipses which reflect this size.

Description of file contents

You can put a string of characters (maximum 32) at the beginning of the user file to succinctly describe its content. This optional string must be on the first line of the file and begin with the “$” character. When you load this database file, C2A will use this description to identify it (in addition to the file name).

Example: $ Uppsala General Catalogue

For a file to be automatically recognised as a user text file, it must have the extension “c2a”. Without this convention, user files will not be automatically recognised in the database directory specified through the User catalogues… command in the File menu.

Object declarations

Stars

For stars, the declarations must have the following form (see the following table for an understanding of the detailed syntax in each field):

star, <right ascension>, <declination>, <magnitude>, <spectral type>, [<name>], [<comment>];

Galaxies

For galaxies, declarations must have the following form (see the following table for an understanding of the detailed syntax in each field):

galaxy, <right ascension>, <declination>, <magnitude>, [<ellipse>], [<name>], [<comment>];

Example of a galaxy declaration:

%
Example of a comment block associated with the following object. In this example, the galaxy will be represented by a 6.5’ par 2.7’ellipse with an inclination of 135° with respect to North
%
galaxy, 0 3 15, 16 8 42, 12.0, 6.5 2.7 135, "UGC 8";

Frames

It is possible to declare specific objects called 'frames'. These objects are represented in the maps as rectangles whose dimensions are specified in the object declaration. A frame must be declared with the following syntax (see the following table for an understanding of the detailed syntax in each field):

frame, <right ascension>, <declination>, <RA dimension>, <DE dimension>, <rotation>, <RGB color>, <style>, [<name>], [<comment>];

Example of a frame declaration:

frame, 05h 38m 55s, +27° 09' 35", 1° 56' 29", 1° 27' 41", 90°, 255 255 0, 1, "SH2-240_1", "First frame of the mosaic";

Objects with two dimensions

For all extended objects which can have two different dimensions (and can therefore be represented by an ellipse), which is to say, open clusters, diffuse nebulae, dark nebulae, planetary nebulae, galaxy clusters and un-classified user objects, declarations must have the following form:

<type1>, <right ascension>, <declination>, [<magnitude>], [<ellipse>], [<name>], [<comment>];

Example of user object declaration (without any particular type):

%
Field center for imaging a part of the SH2-240 nebula
%
object, 5 41 09.2, +27 02 44.8, *, -1 -1 -1, "SH2-240_1", "Part 1 of the composition";

In this last example, we do not want to declare any magnitude or shape to the object. This is why we use the declaration '*' for the magnitude and '-1 -1 -1' for the elliptical shape of the object. The object will be represented by a simple green cross in the display.

Objects with one dimension

For all extended objects having only one dimension (and can therefore be represented by a circle), i.e. globular clusters, supernovae, pulsars and quasars, the declarations must have the following form:

<type2>, <right ascension>, <declination>, [<magnitude>], [<size>], [<name>], [<comment>];

Objects without dimension

Finally, declarations for other dimensionless objects, that is, simple stars, double stars, multiple stars, asteroids, comets and satellites, have the following syntax:

<type3>, <right ascension>, <declination>, [<magnitude>], [<name>], [<comment>];

Example of an asteroid declaration:

%
Fast moving asteroid 2012 DA14
%
asteroid, 11 45 30.7, +20 21 50, ?, "2012 DA14", "2013 15 15 200000";

Note: The characters [ and ] denote an optional field. Note also that if an optional field is included in the declaration of an object, all the optional fields of preceding this one must also be included (for obvious reasons of interpretation).

The syntax of different fields is described below:

<type1>

This is the type of declared object (with two possible dimensions) and the keyword should be one of the following:

open cluster

galaxy cluster

diffuse nebulae

open cluster + diffuse nebulae

dark nebulae

diffuse nebulae + galaxy

planetary nebulae

object

<type2>

This is the type of declared object (with one possible dimension) and the keyword should be one of the following:

globular cluster

quasar

supernova

pulsar

<type3>

This is the type of declared object (without dimensions) and the keyword should be one of the following:

simple star

asteroid

double star

comet

triple star

satellite

multiple star

 

<right ascension>

Right ascension of the object for the equinox 2000. This declaration must have the form AhBmCs where A and  B are integers and C a real number.  The characters h, m and s are optional and may be replaced by spaces. You can also use the form AhBm if you do not want to specify seconds of  time. In that latter case, B must be real number (if it is an integer, it must be specified with a trailing .0).

<declination>

Declination of the object for the equinox 2000. This declaration must have the form A°B'C'' where A and B are integers and C a real number. The characters  °, ' and '' are optional and may be replaced by spaces. You can also use the form A°B' if you do not want to specify arc seconds. In that latter case, B must be a real number (if it is an integer, it must be specified with a trailing .0).

<magnitude>

Magnitude of the object (as a real number). If the magnitude is not know, this field must be replaced by a question mark ? or a * character.

<spectral type>

Spectral type of the star. This must be a letter from the list: O, B, A, F, G, K, M, C.

<ellipse>

The field allows you to define the major and minor axes and the inclination of a galaxy (or another two-dimensional object) which can be represented by an ellipse. It comprises three real numbers separated by spaces:

<major axis> <minor axis> <inclination>

The major and minor axes must be expressed in arc minutes and the inclination is calculated from the North towards the East in degrees (which must be between 0 and 360°). If the major and minor axes have a value of 0, the object will be represented by a symbol and not an ellipse or a circle. If the minor axis is 0, the object will be represented by a circle. Additionally, if the inclination is -1, C2A will assume the latter is unknown and will display an ellipse of zero inclination and a specific colour (which tells the user that the inclination is unknown). An example of a declaration is given later in this section.

<size>

This field lets you define the size in arc minutes of an extended object represented by a circle. This is therefor used for objects of the type: globular clusters, supernovae, pulsars ans quasars. If you do not want to specify a size (because, for example, you don’t know it) just use the value 0. User objects which have a declared size will be displayed with a dotted cicle (above a certain level of zoom) whose radius corresponds to the declared size.

<RA dimension>

Only for objects with the 'frame' type. Frame dimension along the right ascension axis. This declaration must have the form A°B'C'' where A and B are integers and C a real number. The characters  °, ' and '' are optional and may be replaced by spaces. You can also use the form A°B' if you do not want to specify arc seconds. In that latter case, B must be a real number (if it is an integer, it must be specified with a trailing .0).

<DE dimension>

Only for objects with the 'frame' type. Frame dimension along the declination axis. This declaration must have the form A°B'C'' where A and B are integers and C a real number. The characters  °, ' and '' are optional and may be replaced by spaces. You can also use the form A°B' if you do not want to specify arc seconds. In that latter case, B must be a real number (if it is an integer, it must be specified with a trailing .0).

<rotation>

Only for objects with the 'frame' type. Rotation to operate in the frame in the counter-clock direction.

<RGB color>

Only for objects with the 'frame' type. Three integers separated by spaces and which represent the R, G and B values of the frame that will be drawn in the maps. Each of these values must be between 0 and 255. The frame label will also be displayed in this color.

<style>

Only for objects with the 'frame' type. Integer that represents the style of the frame that will be displayed in the maps. The possible values are the following: 0 (frame with a full line), 1 (dotted line), 2 (line with dashes), 3 (line with successive figures made of one dot and one dash) et 4 (line with successive figures made of one dash and two points).

<name>

Optional name of the object. This must be a character string within quotation marks and may include spaces. Example: “delta Orion”. When launching a Search by name…, C2A uses this field, if it is present, to search objects in user catalogues.

<comment>

Optional comment attached to an object. As with the field <name>, the comment must be a string of characters between quotation marks and may include spaces. Example: “The most beautiful nebula in the heavens”. The comment must not be longer than 511 characters. It is displayed when user objects are identified in the maps.

A declaration must be contained in a single line (even if it has more than 80 characters). Each line is ended by an optional ; character (it is however advised to use it in order to have a clean definition of each object).

The character ‘#’ indicates the presence of a comment at the end of as line (the comment will be ignored by the program).

It is possible to associate a block of several lines of comment with an object (not to be confused with the field <comment> placed at the end of the declaration). To do this, just place before the declaration of the object a block of text enclosed by “%” at the beginning of a line. There  is no limit to the number of lines in a comment block. The example of the asteroid declaration above illustrates the use of a comment block.

Note that to find a user object, just type its name in the rapid search area of the find object box and OK it with the ENTER key. The object can only be found if the user catalogue is active in the dialogue box which lets you manage user catalogues.

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