wfcmdb records details of filters mounted for use with the WFC. The details allow the system to find which filters are loaded in the filter wheel and ensures that the log and archive are correctly written.
wfcmdb is a rolodex-like X-windows GUI. It shows the details for one filter at a time, like this:
The buttons marked `>' and `<' allow you to scan forward and backwards respectively to view the other known filters.
The six data displayed for each filter are all editable. If you need to edit any of these fields, you must press the `commit changes' button before moving to view another filter. You must also save your changes explicitly on exit if you want them to be used by the system.
The business of registering a new filter is discussed in the section Using WFC filters and the meanings of the fields are given here.
The filter-holder code is a deciaml number equal to the 5-bit binary code embossed on the rim of the filter mount. The ICS reads this code to identify the filter mount and searches the database file whose name is displayed by wfcmdb to find out which filter is in the mount.
The invocation is the name for the filter used in the filter command. It is case sensitive, to distinguish broad-band and narrow-band filters.
The waveband and photometric system are recorded in the observing log and in the FITS header for each observation.
The focus offset is used by the ICS and TCS to correct the telescope focus for filters of different thicknesses. In the current database, the offsets are measured relative to the Harris filters. The offsets are always positive and are larger for thicker filters.
The unique ID of the filter is a catalogue number from the ING database of optics. It is recorded in the FITS header for completeness; it may one day be useful to distinguish between different filters of the same nominal waveband and photometric system.
The `new item' button generates and displays a blank entry in the catalogue in which to register a new filter. The `delete item' button removes the currently-displayed entry from the database and switches the display to entry number 1.