CALIFORNIA ASSOCIATION FOR RESEARCH IN ASTRONOMY

Title:

MAGIQ DEIMOS guider flexure compensation

Date of Observation:

Jan 27

Lead:

Wirth

Other persons involved:

Kwok

Telescope(s)

Keck II

Instrument(s)

DEIMOS

Sky time Requested

3 hours

Date(s) to avoid

None

Required conditions

Any

Purpose (Please describe succinctly the main purpose of the proposal: development project, general telescope engineering, instrument commissioning, problem trouble shooting, data quality, etc.):

We propose to test the algorithm in MAGIQ software for correcting the guide star position to compensate for flexure in the DEIMOS guider.  These corrections are crucial to keeping the stars in the slits during long integrations involving instrument rotation.  Initial test data taken on the DEIMOS engineering night in July 2008 indicated that the compensations are not yet within spec and require further testing.

Description (Please describe your night-time engineering plan; provide justification for the time request, and include figures, ECR description and other attachments if necessary):

We will take images of a random starfield through meridian crossing while guiding.  Each test requires about 30 minutes to complete 120 deg of rotation.  We will test forward and backward rotations through a full 360 deg of DEIMOS physical rotator angles in 3 trials of 120 deg each; hence, a minimum of 3 hours (6x30 minutes) is required.  Additional time could be used for further testing.

Plan for data reduction, analysis, and reporting:

Data reduction is very straightforward: we simply measure the change in location of random stars during the image sequence.  If the guider flexure compensations are enabled and working, then the star centroids should change by less than +/- 1 pixel throughout the exposure sequence.  Software to perform these measurements was created during the July run and will be re-used.

Other resources needed:

None.

Status and progress reports from previous use of engineering time:

DEIMOS data acquired in July revealed that the MAGIQ guider flexure compensation algorithm still had some bugs.  We attempted to obtain data on an engineering night in August but all of our time was lost due to an ACS failure.