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A.1 Specifying the grating tilt

A.1.1 RC Spectrograph

For the RC Spectrograph, the user can specify the central wavelength desired directly in Angstroms using the 4-m Telescope Control System (TCS) Graphical User Interface (GUI). The user must specify the grating name, the order, and the desired central wavelenth.

We give in the table below the encoder units corresponding to a particular wavelength setting. This table may be useful for simply substantiating the setup, and in determining the anamorphic demagnification, as explained in Sec. 4.3.

 

A.1.2 CryoCam

The wavelength in the center of the chip is determined by the choice of grism. However, there are a number of slit inserts that one can choose that will in fact change the central wavelength by of the wavelength coverage. The table below shows what offset slit aperture plates are available, and what these shifts would be with the 300 l/mm grisms. Other grisms will scale proportionally.

CryoCam Offset Slits
Offset Shift for 300 l/mm Slit widths available
15.0mm blue -520Å 1.4'', 1.7'', 2.5'', 3.2'', 10.2''
10.8'', 11.1'', 21.0''
7.5mm blue -260Å: 1.7'', 2.5'', 3.2''
0.0mm --- 1.0'', 1.7'', 2.5'', 3.2'', 3.7''
7.5mm red +260Å 1.7'', 2.5'', 3.2''
11.0mm red +380Å 2.5'', 3.2''
15.0mm red +520Å 1.7'', 2.5'', 3.2''
22.6mm red +700Å 2.5''

A.1.3 GoldCam

The grating tilt of the GoldCam spectrometer must be set by hand; care must be taken not to overtighten the tilt clamp and observers are cautioned to call for help if an adjustment is needed.

The table below shows the encoder setting for a particular wavelength. (The grating tilt of the zeroth order is 25.93.) In reading the dial setting for the grating tilt, it is the number that is covered by the pointer that gives the integral number of degrees.


next previous contents
Next: A.2 Focusing the Spectrograph
Previous: A Setting Up and Focusing the Spectrographs
Updated: 02Sep1996