User's Guide to the Nickel Spectrograph

Table of Contents

Hardware Overview
Aperture Wheel
Filter Wheel
CCD Stage
Detector Characteristics
Software Overview
CCD User Interface
Motor Controller
Observing Hints
Calibration Lamp Spectra

Data Archive
Mt. Hamilton Homepage

Aperture Wheel

The aperture wheel has seven slots for slits, pinholes, and occulting disks, and a clear position. Any position of the wheel may be remotely selected from the Motor Control GUI.

For slit spectroscopy, an assortment of precisely machined, slit-shaped apertures is provided. The observer may chose from among eleven apertures of various fixed widths (most are 3.6 arcminutes in height), but the four mounted by default in the aperture wheel (see below), along with a pinhole and two occulting disks, have proven satisfactory nearly everyone's needs.

The apertures are positioned at a slight angle to the focal plane so that a periscope assembly can be used to view the slit with the guide camera, for both field acquisition and autoguiding.

If yopu need to use an aperture that is not one of the standard apertures, contact a support astronomers in advance of your run so that they can install the aperture for you. The standard installed apertures and others listed listed below.

Standard Contents of Aperture Wheel
Pixel Width1 Arcsec WidthReturn
11.4 (0.7)2.91550
22.2 (1.2)4.61850
33.2 (1.7)6.62150
44.2 (2.2)8.82450
6Occulting Disk5.03050
7Occulting Disk10.03350
1 Values in parentheses are for the 58mm Nikkor lens.
Other Available Apertures
Millimeter Width Pixel Width1 Arcsec Width
0.0970.29 (0.15)1.2
0.1460.44 (0.23)1.7
0.1940.61 (0.32)2.3
0.3401.0 (0.53)4.1
0.38821.2 (0.61)4.6
0.6461.9 (1.0)7.7
0.9232.8 (1.5)11.0
1 Values in parentheses are for the 58mm Nikkor lens.
2 All slits are 18mm (3.6 arcmin) long with the exception of the 0.388mm aperture which is 10mm (2.0 arcmin) long.

Aperture IDs
ID NumberAperture
12.9 arcsec slit
21.2 arcsec slit
31.7 arcsec slit
42.3 arcsec slit
54.1 arcsec slit
6?? arcsec slit
74.6 arcsec slit
8?? arcsec slit
96.6 arcsec slit
107.7 arcsec slit
118.8 arcsec slit
1211.0 arcsec slit
134.6 arcsec slit, 2.0 arcmin long
141.5 arcsec pinhole
5"5 arcsec occulting spot
10"10 arcsec occulting spot
15"15 arcsec occulting spot
N/Alarge (maybe 20 arcsec) occulting spot

Support Astronomers (
Last modified: Tue Jul 17 18:34:48 PDT 2012