The pointing to any location is accomplished through two
mechanisms, one external and one internal.
The first is achieved with the use of external legs, that
move the whole CDS instrument at 45 degrees to the N-S
and E-W directions, with about
2¢¢ steps. The overall pointing accuracy of the CDS instrument
has been at best 10¢¢.
The area reachable can
extend out to a maximum 1.4 solar radii in certain
directions.
The internal movement is more accurate because it is done via the movement
of the scan mirror and the slits, with 2¢¢ steps,
and has a negligible error.
It is limited to 4' in either direction.
