Cassegrain f/13.7 focus
Cassegrain Spectrometer (es2)
Dr. Anita Cochran
ES2 Users Manual (pdf)
A low-to-moderate resolution spectrometer (600-2,500). The CCD detectors are CC1 and TI1. TI1 should be used for the blue region and CC1 for the red. Various gratings are available to provide wavelength coverage from 0.3 to 1.1 microns. The spectrometer has long slit (120 arcsec) capability. There is a selection of slits of predetermined sizes from 0.5 to 12 arcsec. Limiting magnitude mv = 18 mag. Autoguiding is available using software optimized for guiding on a slit or a guide star in an offset mode.
|Grating No.||Blase Å||Grooves/mm|
Dispersion lambda/delta lambda (2 pixel, 1st order, TI1)
|300 grooves/mm = 650|
|600 grooves/mm = 1300|
|1200 grooves/mm = 2600|
For CC1, resolution is 12/15 that of TI1. Only one grating may be mounted at a time and wavelength setting is not overly reproducible.
ES2 has only predefined slits to use. These are on a wheel in the instrument and are set remotely with a selector switch. The slits are reasonably reflective for purposes of guiding.
Slits 3-12 are nominally 120 arcsec long.
The instrument is attached to the telescope with the Telescope Utility Bin (TUB). The TUB contains argon and neon comparison lamps, as well as slit control and TV position control. The TV may view the slit directly or a field or offset position. The TUB is controlled by a switch box (not software) and is accessible from either the dome floor or the control room.