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New Optics-CCD Combinations for the RFP (1Jun95)
(from CTIO, NOAO Newsletter No. 42, June 1995)

Since August 1994 we have been using Arcon controlled Tektronix CCDs as
the detectors for the Rutgers Imaging Fabry-Perot.  These CCDs have 24 um
pixels, low readout noise (typically 3-4.5 e-), and excellent quantum efficiency
and response flatness. The software interface for the Arcon users allows the
standard RFP spectrograph control to be done via an IRAF parameter file,
which makes the instrument use very transparent. A similar interface is in use
on our 4-m R-C spectrograph with the Tek + folded Schmidt camera or Blue
Air Schmidt + Loral 3K.

Because the Tek 2K and Tek 1K have large image areas we have also
provided a longer focal length camera, which is of particular use on the 1.5-m.
Below are the telescope/focus/camera options currently in use.

                       135 mm (f/2.0)   200 mm (f/4)
Telescope                  camera          lens

4-m     f/7.76          0.36"/pixel     0.24"/pixel
1.5-m   f/13.5          0.54"/pixel     0.36"/pixel
1.5-m   f/7.5           0.97"/pixel     0.65"/pixel

The preferred options are the 135 mm camera for the 4-m, and the 200 mm
camera for the 1.5-m (at f/7.5). With the 200 mm lens the field projects onto
approximately 750 pixels at the detector.  Either the Tek 1K or Tek 2K chip
can (and have been) be used.  The choice is sometimes driven by other
scheduling constraints.  Currently (February 1995) the Tek 2K in Arcon 3.6
offers slightly lower read noise (however, it is in heavy demand for 4-m
instruments).

The FOV remains determined by the 1-inch focal plane aperture of the
instrument. On the 4-m, this gives about 160" of useable field, while on the
1.5-m the FOV is 440" at f/7.5 and 245" at f/13.5.

It should be noted that the 4-m and 1.5-m at f/13.5 do provide significant
numbers of nights with sub-arcsecond seeing. Due to optics problems the
1.5-m at f/7.5 never produces images as small as 1", and 1.5" is typical.

Bob Schommer(rschommer@noao.edu),
Steve Heathcote (sheathcote@noao.edu)

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