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

Observing Hints and Auxilliary Information

Note that these pages are under construction and reorganization. Many of these pages will move to Setup Procedures in the near future.

Readying the Spectrograph | Filling the Dewar | Taking a Test Exposure | Navigating the Spectrum | Calibrations | Systems Integrations | Data Directory | Overscan Subtraction

Filling the Dewar

Due to safety considerations in the Hamilton Camera room, only staff members who have been trained in the proper procedures fill the dewar.

Data Directory

Data are stored in the directories /data/hamshane and /data/hamcat determined by whether the Shane or CAT telescope is being used with the Hamilton Spectrometer. If data are in the directory from a previous observer's run, please contact a Support Astronomer or Telescope Technician to clear the data directory for you. Their procedures confirm that data are archived before clearing the directory.

Overscan Subtraction

A Python 3.x script to do overscan subtraction from a list of FITS files is available: This script will correctly identify the overscan and data regions regardless of binning or subregion of the Lick Observatory detector read out or whether one or two amplifiers are used. Each row of the overscan is median combined and optionally a third order legendre polynomial is fit to the overscan. This is then subtracted from the data region and written to a file.

Syntax: -f -i inputfilelist -o outputfilelist

-f is an optional argument to indicate that the Legendre polynomial fit is desired (this is recommended for most data).
inputfilelist is a text file containing the names (one per line) of the FITS files for which you wish to do overscan subtraction.
outputfilelist is a text file containing the names (one per line) of the output FITS file names. This file should have the name number of lines as inputfilelist. outputfilelist may be the same as inputfilelist, which will overwrite the original files with the new overscan subtracted files.

Examples: -f -i rawdataList.txt -o overscanSubtractedList.txt -i inFitsList.txt -o outFitsList.txt requires Python 3 packages numpy and astropy. Also, this script assumes that the path to python is /bin/python3. If that is not the case on your machine, you may have to edit the first line of the program with the proper path. Bug reports, comments, and suggestions for should be directed to Elinor Gates (

Support Astronomers (
Last modified: Wed Sep 23 16:11:43 PDT 2020