P3.4 Telescope control – focal plane geometry estimation

• Phase : 3
• Status : Draft
• Category : Nighttime testing (functionality and operability) (C4)
• Recurrence : once at commissioning
• Duration : 1 hour(s)

Description

• For the correct telescope mode for SHARK-NIR, find the offset direction & magnitude (for the field-stabilized mode), verify the proper image orientation, pixel scale, field of view, and distortion at the SCICAM. Note that this may be performed with and without AO running.

Prerequisites

• Atmospheric conditions: should be able to see bight stars on sky (preferably close to zenith?).
• Authorize SHARK-NIR on the SX side.
• Suitable binary or astrometric targets.
• AO running for part of the test.

Procedure

1. Procedure for image orientation
   • Select a filter
   • Place the de-rotator in the nominal "zero" position.
   • Issue a preset to move to a bright star (but not too bright to saturate)
   • Center the star in the science channel
   • Issue a pure elevation offset to the TCS of ca. 5” and verify expected motion direction on the SCICAM
   • Return to the on-axis position and repeat with a pure azimuth motion.
   • Issue a preset to move to a suitable astrometric binary (typically 5-8 arcsec separation) and center one star in the science channel.
   • Based on the published coordinates of the binary, issue the appropriate offset to center the other star.
2. Procedure for pixel scale/ plate scale
   • Select a filter
   • Issue a preset to move to a suitable astrometric binary to measure pixel scale (typically 5-8 arcsec separation)
   • Center the binary in the upper half of the SCICAM and take several frames. Average these frames
   • Move the binary to the lower half of the SCICAM and repeat.
   • Use the difference image (optionally flat-fielded) to verify the expected pixel scale. This gives two measures.
   • Repeat this for other filters.

Success criteria

• The image orientation is as expected. The pixel scale and field of view of the SCICAM are as expected.

Notes LBTO support

• Support from telescope operator (if needed).
• Presence of John Hill usually helps while collimating for the first time.

Associated SHARK-NIR personnel

Date performed and by whom