next up previous contents index
Next: Finding the Telescope Pole Up: Two-Star Pointing Previous: Two-Star Pointing   Contents   Index

Finding the Telescope Pole Offset - Mechanically

The telescope axis can be determined by rapidly slewing the telescope along the RA axis during an exposure, at 50% maximum slew speed. If the telescope is pointing along the dec axis, the stars should create circles around the center of the CCD. Finding this position can take a few trials. It need not be precise, (up to ${\sim
0.5^\circ}$ is fine, for there are other large systematic errors in the two-star rotation matrix.

When the telescope is pointing along its axis, record the axis 1 encoder position using rstat described in Section 2.5.4. Convert this to degrees by dividing by the conversion factor in schierd.conf, which should be 19395. Subtract the converted value from ${90^\circ}$, and you have the offset.

Rotse Pager 2003-05-20