DEIMOS Notes for Observing Assistants

Description

DEIMOS is a general-purpose, faint-object, multi-slit, double-beam, visible-wavelength imaging spectrograph at the Nasmyth focus on Keck II. DEIMOS features wide spectral coverage (up to 5000 � per exposure), high spectral resolution (down to ~1 �), high throughput, and relatively wide field of view (81.5 arcmin� field).

Summary

  • Type: Dual-beam, multi-object spectrograph
  • Wavelength range: optical
  • Spectrograph type: slitmask
  • Detector array: 8 × ( 4k × 2k) CCDs
  • Rotator: built in
  • Position: K2 RNAS
  • Built at: UCO/Lick
  • Optimized for: Surveys of distant galaxies
  • GUI control: Dashboard (similar to ESI)

Guider

  • PXL 1024×1024 pixel at 0.21 arcsec/px
  • Field of view shows pickoff mirror at bottom 1/3 and slitmask on top 2/3
  • Slow readout like ESI
  • Displays significant pattern noise in 2×2 binning readout mode.
  • Get good reflection off slitmasks; guiding on slitmask OK
  • TV guider flexure is significant

Rotator

  • Entire instrument rotates
  • Limits of rotation are -330° < ROTPPOSN < +400° (two complete revs)
  • Slew speed is about 2m 15s per 1 revolution
  • Tracking excellent through zenith

Pointing Origins

  • See also: KSD40-style drawing of focal plane
  • REF is on center of pickoff mirror (AUTOFOC here)
  • SLIT is centered on the longslit position
  • IMAGE is directly above the slit (send faint longslit targets here)
  • DEIMOS is at slitmask center (send slitmask centers here)
  • TVCENTER is at center of guider (512,512)
  • MIRA will be used for telescope focus

Focus

  • AUTOFOC and MIRA work well
  • Secondary tilt compensations should be minimal
  • Should not need to focus as often as with LRIS
  • Probably no telescope focus difference between imaging and spectroscopy modes

Eavesdropping

  • OA can run DEIMOS dashboard from DCS GUI

See Also

Last modified: 07/10/2020 05:20
Send questions or comments to:DEIMOS Support

The information on this page is the property of the W. M. Keck Observatory. The contents of this page or any part thereof shall not be copied or otherwise reproduced or transferred to other documents or used or disclosed to others for any purpose other than observing support at the W. M. Keck Observatory and the subsequent analysis and publication of scientific data obtained from observations conducted at the W. M. Keck Observatory. All rights reserved. © W. M. Keck Observatory.