Catalogue entries

There is an internal catalogue containing the names, positions and guide star references for up to 500 objects. ADV/CAT will give the source names of all targets in the current catalogue, while LIST/CAT will give the full details. Stored system cataloges are listed in section . There are 3 special entries:

• the `EDIT source' is the catalogue entry whose parameters (RA, Dec, equinox, proper motions, guide object) are presently being modified;
• the `CURRENT source' is the object being observed, and
• the `NEXT source' is the object that will be observed when the GO command is typed, or the `Telescope-Dome Source' button SRCE on the Control Desk is pressed, at which point the object also becomes the CURRENT source. The said button is found under the label T/SDOME at the top centre of the `System Control' panel, which occupies the lower section of bay 2 (from left).

Modifications to the CURRENT source's parameters do not affect the operation of the telescope directly. This is only altered when a button is pressed or GO is typed, in which case the parameters of the NEXT source are always picked up. When a new catalogue entry is defined using the SOURCE command, it automatically becomes the EDIT source, except if SOURCE/MARK is used. The edit pointer is also changed if an existing source name is input. Thus any data input will always be associated with the edit source until the pointer is changed by a SOURCE or an already defined source name. Any source parameters which are not specifically entered will be picked up from the first entry in the catalogue .D(EFAULT). At STARTUP all three pointers point to .D(EFAULT). It is therefore, possible to observe by merely entering R and D commands (each new entry going into .D) and pressing GO at the end of the observation. By this means the pointers are never reset and no source entries are accumulated in the catalogue.

When the same objects are to be observed on different nights SA(VE) will store the current internally held catalogue and this can then be recalled from disc with I(NPUT) on any subsequent occasion. The contents of the catalogue are stored as commands so that restoring the catalogue allows objects in it to be acquired immediately without resort to any other commands apart from GO.