AAS 204th Meeting, June 2004
Session 10 Instrumentation, Ground-based
Poster, Monday, May 31, 2004, 9:20am-6:30pm, Ballroom

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[10.11] Slitmasks for instruments at Keck Observatory

S L Allen, D A Clarke, A C Phillips (UCO/Lick Observatory), G D Wirth (CARA, Keck Observatory)

DEIMOS and LRIS are multi-slit spectrographs used with the 10-meter telescopes at W.M. Keck Observatory on Mauna Kea. Their focal planes admit light from celestial objects through slitlets cut into interchangeable aluminum sheets. Each observing night may use a dozen custom-cut slitmasks. Each mask may have dozens, or even hundreds, of slitlets.

The process of observing through a slitmask starts with an astronomer choosing targets. Ideally it ends with FITS files which contain images of spectra from each slitlet and tables which document the slitlets and the objects viewed through them. We describe the system which handles slitmasks for Keck from the point where the astronomer has completed the mask design to the point where archival FITS files have been constructed. This system was created for DEIMOS and later retrofitted to LRIS.

DEIMOS slitmask design files (MDFs) contain FITS tables that document objects and slitlets on the sky and on the metal. The observer submits MDFs via a web interface which authenticates the user, validates the input, and inserts the mask design into a relational database (RDB). Consistency checks later verify each slitlet and alert the observer of any problems via e-mail. Astronomers and engineers can check the status of masks via additional web interfaces which query the RDB.

At the milling facility a graphical user interface (GUI) queries the RDB to display a prioritized queue of masks to be manufactured. A machinist uses the GUI to produce code for a numerically-controlled mill. Manufactured masks receive a barcode to identify them uniquely for use during observation. The DEIMOS observing software queries the database and attaches to each image a set of FITS tables describing the slitmask. This allows DEIMOS software to align the mask on the sky automatically to sub-arcsecond precision.

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Bulletin of the American Astronomical Society, 36 #2
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