User manual

 Numerous commented examples that can be the base for your own filters;

 Buttons giving access to reference columns in the catalogues currently loaded in

Aladin;

 A button giving access to graphical “actions” to perform;

 Buttons giving access to mathematical functions and to available units.

You can also reload a filter from a previously saved file.

Syntax

To understand the filter syntax, let’s start with the following example. Let’s say that you

want to display “object types” and only for bright sources. This filter can be written as

follows:

${B}<18 { draw ${OTYPE} }

Only lines for which the value in the “B” column (B magnitude) is lower than 18 will be

kept, and the display will be relative to the “OTYPE” column (object type).

As we see, a basic filter has the following syntax:

a_test { an_action }

 This test is optional and if no test condition is given, all sources are affected;

 It is possible to indicate several actions, separated by the ‘;’ character or by returning

to the next line;

 It is possible to have several groups “test{action}” one after the other. In this case,

the first action in the list associated to “true” will be the one taken into account, other

lines will then be ignored.

${class}="Star" {draw square}

${class}="Radio" {draw rhomb}

${class}="Galaxy" {draw plus}

 Lines starting with ‘#’ are comments.

Test

 The test command uses usual comparison operators (=, !=, <, >, >=, <=).

 It can have parenthesis, Boolean operations AND (&&), OR (||), NO ( !)

 Mathematical functions can be used (abs, cos, deg2rad, exp, ln, log, rad2deg, sin,

sqrt, tan);

Example: Draw sources corresponding to the following expression: