1 Glossary of Terms, Acronyms, and Symbols

PA:

Position angle of the DEIMOS x-axis with respect to the sky, measured north through east.

RPA:

Rotator position angle of the DEIMOS spectrograph x-axis with respect to the Nasmyth platform. At 0, the slit direction is vertical with Side A on the right when looking at the focal plane from the outside. From this view, RPA increases as the instrument rotates counter-clockwise. This also corresponds to increasing PA of the slit on the sky.

FCS:

Flexure Compensation System.

T:

Temperature inside DEIMOS, in C. (Nominal T = C)

P:

Atmospheric pressure, in mm of Hg. (Nominal P = 615 mm)

FKCS:

Fundamental Sky Coordinate System.

RSCS:

Refracted Sky Coordinate System.

MFCS:

Mask Form Coordinate System.

SMCS:

Slit Mask Coordinate System.

ICS:

Image Coordinate System.

CCDCSi:

Pixel coordinate system of CCDi.

FCSj:

Pixel coordinate system of Flexure Compensation CCDj.

TVCS:

Pixel coordinate system of the TV Guider CCD.

GOH:

Grid of Holes mask, for direct imaging.

LOS:

Line of Slitlets mask, for spectroscopy.

LOH:

Line of Holes mask, for spectroscopy.

SGOH:

Staircase Grid of Holes mask, for spectroscopy.

SGOTH:

Staircase Grid of Tiny Holes mask, for spectroscopy.

FPFs:

Focal plane fiducial marks. Two marks within the slitmask area near the focal surface and projected onto the fiducial CCD during direct imaging.

Fiducial CCD:

The fiducial CCD is No. 3 in the CCD array. It is the first CCD installed in the focal plane and the one to which the others in the array are aligned. Images of the focal plane fiducials fall onto the fiducial CCD during direct imaging.

Slitmask Form:

The cylindrically curved form into which slitmasks are pressed. Approximates the spherically curved telescope Nasmyth focal surface.

Astrometric Mask:

A slitmask for direct imaging with boxes at the expected positions of astrometric standard stars. The displacement of the stars relative to the boxes provides corrections terms to the mapping RFCS MF/SMCS.

Offset Guide Mirror:

A permanently fixed mirror mounted in the focal plane next to the slitmask area. Its image of the sky is visible in the TV Guider at all times regardless of whether a slitmask or longslit is inserted.

TVFs:

TV fiducial marks. Two marks etched onto the offset guide mirror, parallel to the focal plane fiducials within the slitmask area, and permanently visible in the TV guider.