DEIMOS user script wftel

Name

wftel -- wait for telescope to complete a move

Purpose

Pause execution of script until we confirm that the
guider has resumed guiding at a new location. Generally
this is used in scripts that perform telescope moves.

Usage

wftel [-D] [-p] [-v] [autresum]

Options

-p = prime; return the current value of DCS AUTRESUM keyword
so that we can later pass this value back to the script as a
reference.

-v = verbose; print additional output about execution phase and
time

-D = debug mode (print diagnostics)

Arguments

autresum = value of AUTRESUM keyword prior to the telescope move.
If you fail to pass in a value then the loop will probably time out.

Output

transcript writted to stdout

Procedure

Second method is to monitor the pause and resume events. After
issuing the offset request, we need to monitor the keyword AUTPAUSE
to increment its sequence number. Then we monitor the keyword AUTGO
to change to RESUMEACK, which is issued by the guider. At this
point, the guider will throws away the first image and resume
guiding with the next image. The offsetting/nodding script can
terminate at this point also, without waiting for guiding to fully
resume. Because TCS internally waits for AXESTAT to go from SLEWING
to TRACKING before sending the RESUME notification, we assume that
the telescope is at the correct position by the time the guider
acknowledges the RESUME notification. This will save more time one
more guider cycle than the first method at the risk that the guide
star may be not at the final destination. This can happen if the
plate scale is not correct (i.e. at the edges of the guider
detector) and the guide box goes to a different place than the guide
star image. The first guider image after the offset will drag the
star to where the guide box is.

Exit values

0 = normal completion
1 = wrong number of arguments

Example

1) Use this sort of code in a script to ensure that the telescope

set autresum = `wftel -p` # grab value
(perform telescope offset)
wftel -v $autresum