Getting data

Optical pointing is done using the MNU program, and the DCL commands CRE (CREate the data file), SAV (SAVe telescope coordinates in the data file), CAT (select a star from the star CATalog), and PLA (select a PLAnet), or using the automatic searching mode of MNU. Please refer to the document ``Foreign Commands'' by A. Perrigouard for a complete description of these commands.

Two different approaches can be used for the optical pointing, depending whether you have an idea of the pointing parameters or not.

• First, make a crude optical pointing with a few stars, 5-8 at low and 3-6 at high elevations, with good azimuth coverage. The accuracy need not be very good ($5''$). Then, use the newly determined pointing constants to make a more accurate pointing session with 40 to 60 stars. All stars should be rather well centered already , and now the centering accuracy can be made better ($1''$). Uniform coverage is not required: most important is to have low and high elevation sources.
• Or use only a single pass with 60 stars centered within $1''$. This can take somewhat longer because the stars may be far off center.