User's Guide to the Hamilton Spectrograph

Table of Contents

Quick Reference
CCD Characteristics
Grating Tilt & Dewar Height
Filter Wheel & Shutter
Calibration Sources
Photon Integrator
Image Rotator
Iodine Cell & Slit Room Controller
Guide Camera & Filter Wheel
Data Taking System
Hamilton Motor Controller
Hamilton Focus
More Info:
Spectral Format
Navigating the Spectrum
Table of Orders
Setup Procedures
Observing Hints

Data Archive
Mt. Hamilton Homepage

Filter Wheel and Shutter

The filter wheel and shutter are mounted inside the camera room, just downstream from the entrance slit, on camera-room side of the slit bulkhead. They are reached from a wooden platform, a few feet in front of the camera-room door.

Access to the assembly is usually only needed for changing filters or performing tests that require the shutter to be manually opened. The few filters routinely used for Hamilton work are permanently mounted in the wheel, so observers rarely change filters. However, in some cases, especially when making longslit observations, observers may need to do so (see changing filters).

Filter Wheel

Hamilton observations are generally done without a filter, as order separation is accomplished with cross-dispersion. Filters are, however, often needed for calibration exposures, especially flat fields (see calibrations).

The filter wheel is controlled from the spectrogrpah motor control interface, hammotor_gui, via the filter menu shown below. N.B.: Do not change filters if you have not been trained in the procedure. If you do change filters, you must remember to update the filter names in hammotor_config_gui to reflect changes in the filterwheel's contents! See changing filters.

Science Filter Selection Menu


A circular, diaphragm shutter is attached to the filter wheel. This shutter controls the length of Hamilton exposures. Hamilton observers need not be concerned with small errors introduced by shutter motion or timing (which, in any case, are reasonably fast and accurate) as the spectrograph is rarely, if ever, used for flux measurements.

The shutter receives its signals to open and close from the CCD controller, after the observer has initiated an exposure. If the shutter has been opened manually (there is a lever for doing so on its outer rim), as is sometimes necessary when troubleshooting or adjusting the alignment of a calibration source, be sure to shut it manually when finished, as the CCD controller will not do so before the end of the next exposure.

Diaphragm shutters do occasionally fail, either by not opening at all or by opening very briefly and then partially or completely closing. Such failures are not common, but should be considered when trouble shooting low or absent flux, espcecially in cold weather.

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Last modified: Sun Feb 13 17:22:49 PST 2011