User's Guide to the Hamilton Spectrograph

Table of Contents

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

CCD Characteristics

Three CCD's are available for use with the Hamilton: dewars 4, 6 and 8. Dewars 6 and 8 are 2048 x 2048, 15-micron pixel devices. but their performance characteristics differ significantly. Dewar 4 is a 4096 x 4096, 12-micron pixel device that is under development and available on a shared risk basis.

Dewar 6 is a thinned, back-illuminated device with somewhat better blue response, and is much less susceptible to particle events. Dewar 8 is an unthinned, high-resistivity chip with excellent red response and narrower line profiles (narrow-slit FWHM of about 1.45 pixels as compared to about 2.2 pixels for dewar 6), but particle events are much more common and tend to leave longer trails.

Dewar 6 shows fringing in the red, and has a few bad columns; dewar 8 has no fringing and no bad columns. Their respective readnoise and dark current, and their comparative QE's are given in the table and plot below. (See also detailed characteristics and specifications for Dewar 4, Dewar 6 and Dewar 8 .)

DetectorReadout SpeedAmplifiera Gain
(e-/DN)		 Readnoise
(e-)		Readout Time
(m:ss)b
Dewar 8SlowLeft1.2 5.71:31
Dewar 8SlowRight1.210.9 1:31
Dewar 8FastLeft1.3 10.10:31
Dewar 8FastRight1.317.0 0:31
Dewar 6SlowRight1.110.0 1:31
Dewar 6FastRight1.218.0 0:31
Dewar 4FastRight0.923.2 0:53 c
Dewar 4FastLeft0.913.4 0:53 c
Dewar 4SlowRight0.882.4 2:56 c
Dewar 4SlowLeft0.822.5 2:56 c
aDewars 6 and 8 each have two readout amplifiers, of which only one is used at a time to read out the CCD. It is highly recommended to use the Left amplifier for each detector, as it has significantly less readnoise.
bReadout Time is for the full CCD chip and does not include a special erase of the chip after readout for dewar 8 (special erase takes 8 sec).
cReadout Times for Dewar 4 are for the full chip using both amplifiers. Using a single amplifier to read the full chip will take approximately twice as long.

Other Notes:
Dewar 6 left amplifier is not functioning as of December 2009.
Dewar 8 measurements made during Jan 2009, dewar 6 during Apr 2009 by T. Lowe. Dewar 6 slow readout measurements made by R. Stover Jan 2010.
Dewar 4 is linear in response up to 55,000 DN in all readout modes. Readnoise, gain and linearity measurements were done in Feb 2011. Bias level should be ~1000 DN for all detectors in all readout modes. If it is significantly different contact an observatory staff member.

DetectorDark Current
Dewar 840-57 e-/pixel/hour @ -135C
Dewar 616 e-/pixel/hour @ -118C
Dewar 42 e-/pixel/hour @ -80C

The time to erase the Dewar 8 CCD before the exposure begins is ~13 seconds for slow readout, and ~8 seconds for fast readout. The bias level for all readout modes should be ~1000 DN.


Dewar 4 is Fairchild Dewar#4
Dewar 6 is Loral 2k x 2k
Dewar 8 is LBNL 2k x2k

N.B. The QE for dewar 8 in the above plot was measured at -115 c. QE may be slightly lower at lower temperatures. (stats courtesy of the Lick Detector Lab)

Support Astronomers (sa@ucolick.org)
Last modified: Tue Jul 12 19:45:42 PDT 2011