User's Guide to the Kast Double Spectrograph

Table of Contents

Quick Reference
Hardware Overview
Common Path
Blue Side
Red Side
Detector Characteristics
Kast Controller
Data Taking System
Position Angle
Arc and Flat-field Lamps
Diagonal Mirror
Kast Focus
Telescope Offset
Setup and Observing Hints
Setup Procedures
Observing Hints
Calibration Lamp Spectra
Exposure Time Calculator
Data Quicklook

Data Archive
Mt. Hamilton Homepage


The Kast Double Spectrograph is used at the cassegrain focus of the Shane 3-m Telescope. It is two separate spectrographs - one optimized for the red, the other for blue - housed in a single structure and having some components in common. Each side offers a selection of dispersive elements for various resolutions and dispersions, and both are also capable of direct imaging over a limited field. Dichroic beamsplitters and separate CCD detectors allow simultaneous observations in red and blue. A polarimeter is also available for spectropolarimetry observations.

Oct 4, 2016: New dichroic beamsplitters are now available. One has a transition wavelength of 5700 A, and the other is a new 4600 A dichroic intended as a replacement for the existing 4600 A dichroic (and will be the default D4600 starting 2017A, programs requiring the old D4600 should note that as a special instrumentation request on their proposals). Both new dichroics have much higher transmittance/reflectance and more distinct transitions. More information is available on the Common Path page.

Sept 18, 2016: The Red side CCD had been replaced with a new Hamamatsu detector, yielding significantly better QE for wavelengths greater than 5000 A. Readout noise is also significantly reduced. The new detector is larger, so the wavelength coverage in a single image is increased by about 20%. The Hamamatsu detector is a thick chip, so fringing is not evident (especially compared to the previous Reticon thinned CCD), except out towards 1 micron wavelengths.

The Kast has been in operation since early 1992. It was designed by Dr. Joseph Miller (UCSC) and built in the Lick Observatory shops. The instrument was made possible by a generous gift from William and Marina Kast.

Much of the material presented here is taken nearly verbatim from Lick Observatory Technical Reports No. 66, The Kast Double Spectrograph, by Joseph Miller and Remington Stone, with updated sections and additional material contributed by the technical staff on Mount Hamilton.

The Kast Spectrograph is available to the University of California astronomical community by subscription.
Follow these links to:

3-m Time Allocation Policy
Observing Time Request Forms

All new users must be checked out by a resident astronomer on their first night. Please request support on your time application.

Please direct questions to a Mount Hamilton support astronomer,