Image Servers in Tcl

The astrocat Tcl command is also used to access image servers. For example, the following code retrieves an image file from the DSS server:

 
astrocat cat 
cat open dss@eso 
set filename [cat getimage -pos {3:19:48 +41:30:39} -width 10 -height 10]

To retrieve and image, you typically need to specify the position as a name or in world coordinates and a width and height for the image. This is the default, however, for some image servers, the search arguments may be different. The entry in the catalog config file determines which options may be used for a given catalog or image server. The table below summarizes the options for the getimage subcommand. Some options may not make sense with all image servers:

Option	Value
`-pos`	World coordinates of center position, format: H:M:S[+-]D:M:S.
`-equinox`	Equinox for the position (default 2000.0).
`-nameserver`	Name server to use for resolving object names (for example simbad@eso or ned@eso - default is simbad@eso).
`-name`	Astronomical object name to be resolved by a name server.
`-width`	Width of image in arc minutes.
`-height`	Height of object in arc minutes.
-searchcols, -minvalues, -maxvalues	The argument for -`searchcols` is a list of columns to search by. In this case, we don't have any columns, however some image servers may interpret these as search parameters, such as "patch#" or "region id". The -`minvalues` and -`maxvalues` options supply the corresponding values or value ranges and must have the same lengths (`maxvalues` may be left empty or set to the same as `minvalues` , if you only want to test for equality).

The return value from the getimage subcommand is the name of a temporary file holding the FITS image for the requested area. The file should be copied if necessary, since it will be overwritten by subsequent calls to getimage .