Software Zeropoint: 1-star SNAFU

  A single star SNAFU is done as follows:

1. At the Telescope Computer system terminal, run INPSCF and check (see section ) that the value of parameter HATERM equals 2 (inquire its value by typing: @HATERM). It is essential to do this because if it has accidentally been left with a value of 1, the following actions will completely invalidate the pointing.
2. Check that PCCH has the correct value from the last 2-star SNAFU (check the log sheet). If it does not, then enter the appropriate value.
3. Slew to a star with 0< Dec < 40; the choice between North (2846) and South (delta < 2846) should be made to minimize dome rotation.
4. Type SNAFU at the User Interface.
5. Centre the star on the reference point (see end of Section ).
6. Press the ACK button until it goes out.
7. Determine and record the values of PCIH and PCID.
8. Type END at Telescope Control System Console to exit from INPSCF.

If the pointing after a 1-Star SNAFU is unsatisfactory, then it is good practice to first check if the encoders are performing correctly, before doing anything else, by running the ENCODERS test programme (see section ). If necessary disable a bad encoder and do again a ZEROSET and 1-Star SNAFU. If all else fails try a 2-Star SNAFU, but it is more likely that such failure indicates a serious problem: call the Duty Technician.