Created May 09, 1995  --  RDM
Obtained from WIYN FTP Archives at NOAO, dated February 02, 1995, with
minor updates by RDM


MOS/Hydra
---------

The Hydra Milti-Fiber Positioner and the Bench Spectrograph have
been removed from the KPNO 4m Telescope and transferred to the 3.5m
WIYN telescope.

A general description of the instrument may be found in the Hydra Users
Manual, available via anonymous FTP (ftp ftp.noao.edu, cd
kpno/manuals, binary, get hydramanual.ps.Z).  Changes include the expected 
availability of a new, faster focal ratio camera and a more limited
inventory of gratings. Specifications of capabilities on WIYN
can also be obtained via anonymous FTP (ftp ftp.noao.edu, cd kpno/hydra);
a brief summary is given here.



                    Hydra/Bench Characteristics at WIYN

    |--------------------------------------------------------------------|
    | Full unvignetted field        |      60 arcmin                     |
    | diameters                     |                                    |
    |-------------------------------|------------------------------------|
    | Fiber diameters               |      3 arcsec (blue fibers)        |
    |                               |      2 arcsec (red fibers)         |
    |-------------------------------|------------------------------------|
    | Fibers available              |      96 blue fibers                |
    |                               |      96 red fibers                 |
    |                               |      12 field orientation probes   |
    |                               |      84 locations for future fibers|
    |-------------------------------|------------------------------------|
    | Minimum fiber separation      |      37 arcsec                     |
    |-------------------------------|------------------------------------|
    | Configuration time            |      20-25 minutes                 |
    |-------------------------------|------------------------------------|
    | Estimated positioning         |      0.22 arcsec (20 um)           |
    | accuracy                      |                                    |
    |--------------------------------------------------------------------|

    |--------------------------------------------------------------------|
    | Grating      |  316 line/mm, blaze angle 7 d (B&L 181)             |
    |              |  600 line/mm, blaze angle 13.9 d (B&L 420)          |
    |              |  860 line/mm, blaze angle 30.9 d (KPC-24)           |
    |              |  1200 line/mm, blaze angle 21.1 d                   |
    |              |  316 line/mm echelle, blaze angle 63.4 d            |
    |--------------|-----------------------------------------------------|
    | Cameras      |  All-refractive bench camera (285 mm focal length)  |
    |              |  Simmons camera (381 mm focal length)               |
    |--------------|-----------------------------------------------------|
    | Collimators  |  6 inch f/6.7 paraboloid and spheroid               |
    |--------------|-----------------------------------------------------|
    | Detector     |  2048 x 2048 thinned Tektronix CCD (24 um pixels)   |
    |--------------------------------------------------------------------|

For the purpose of estimating exposure times, proposers should assume
that the WIYN/MOS combination has equivalent throughput to the
4m/Hydra throughput as described in the Hydra manual.

A revised "setup" program is also available for defining the
spectrograph configuration and planning observations.  The setup
program is available via anonymous FTP or Mosaic.