User's Guide to the Nickel Spectrograph

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Table of Contents

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Introduction
Hardware Overview
Software Overview
Observing Hints
Calibration Lamp Spectra
Checklists

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Data Archive
Mt. Hamilton Homepage

Grisms

The grisms are transmission gratings cemented to prisms. The available grisms and their characteristics are listed below (for 27 micron pixels of CCD-9).

Grism	Grooves/mm	Angstroms/pix1	Blaze	Angstroms Coverage2	Central Wavelength x-stage (steps)3	Notes
1	300	7.6 (14.4)	5500	9120 (17280)	-0.390 * lambda + 3338	Formula not Current
2	600	2.5 (4.7)	6500	3000 (5640)	-2.08 * lambda + 14498
3	Not Used
4	600	3.5 (6.5)	4820	4200 (7800)	-0.98 * lambda + 5200
5	300	7.2 (13.9)	7800	8640 (16680)	-0.147 * lambda + 2483	Formula not Current
6	420	5.0. (9.9)	5600	6000 (11880)	-1.09 * lambda + 6974
7 (eschism)4	150	2.0 (3.6)		Order dependent
1Numbers in parenthesis are for the 58mm lens. Only the 110mm lens is recommended for use. 2Due to curvature of the focal plane, the entire range of wavelength coverage may not be useful, especially when using the 58mm lens. 3Enter desired central wavelength in Angstroms, solve for x-stage setting. 4A high-order grism with cross disperser, used as an echelle.

Two varieties of grism tray are available. The first is a rectangular box-like shape and is used to accomodate the much taller 110mm lens and is the default configuration. The second is flat, and designed for use with the 58mm lens, but as that lens is, for all practical purposes retired, it is rarely if ever used. Both trays accept either a slide holding any three grisms, or a slide holding the eschism and its cross-dispersing grism, plus one other normal grism. The tray is repositioned from the Motor Control GUI. Both trays include an empty position for making undispersed direct images, but note that in the absence of an aperture, there is no image on which to guide.

Grisms 2, 4, and 6 are installed by default. Grisms can only be changed by a member of the mountain staff. If you wish to use a different grism, indicate that on your time request and contact a support astronomer in advance of your run so that they can install the proper grism(s) for you.