DIS III - Quick Information, Specifications and Status

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This page last updated: March 5, 2008 - JMD
This page last checked: September 27, 2004 - JMD

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Please refer to DIS TechStaff Information or DIS Users Guide

Contents

Basic User's Guide: DIS - 2007 Start here if you are looking for basic instrument usage!!! Printable version

New Grating Naming Convention Please Read Before submitting your Proposal!!!

Quick Information

• DIS Spectra (Dispersion, Waverange, and (default) Wavecenters) and Offsets

General Instrument Information

• General
• Slits
• Gratings
• Collimator
• Optics

Red Camera Specifications

Blue Camera Specifications

Other Information

Taking Lamp Calibration Spectra

Lamp Spectra and Offsets

DIS Slit Inventory

Quick Information

Standard Default DIS III grating setup is - Blue B1200/Red R1200 & Blue B400/Red R300new.

All grating configurations and wavelength centers need to be explicitly stated (even default setups) in your proposal. Gratings setups different than the standard should be sent requested via separate e-mail to the techstaff at APO 2 days prior to your observing run.

If you wish other gratings than the default, Please state specifically which gratings you wish to use (e.g. Blue B400 (400 lines/mm, new) & Red R150 (150 lines/mm or simply B400 & R300new)) and the wavelength centers you wish them to be set at.

If there is a grating setup different than the standard default setup then your program time will be used, if necessary, to make the grating change and calibrations to/from the standard default setups. Please allow approximately 25 minutes for this. The observing specialist on duty that night can advise you if/when this will need to occur.

The following are the default wavelength centers that we use for our setup calibrations, If you wish a different wavecenter or grating set, Please inform your observing Specialist at least 1 day prior to your observing run.. This gives us time to install and/or calibrate the gratings to your specifications.

DIS Spectra (Dispersion, Waverange, and (default) Wavecenters) and Offsets

The grating centers are fairly stable once set, during the start of the night, and typically do not move during instrument rotations, However movement of the turret (changing from one set of gratings to the other) can cause a grating center shift and therefore you should always repeat your cals if the turret is moved.

Some things to know about DIS:

• Rotation does cause different illumination of mirror cover flats.

• Shutter times of less than 3 seconds are not repeatable.

• Always click the current button (TUI) to verify your gratings, grating centers, binning, and windowing are correct before the start of your program. If they are not, make necessary changes in Remark/TUI and click the apply button.

New Grating Naming Convention

As of Summer 2006 we have installed 3 new gratings, as our default gratings), with improved throughput. We also have implemented a new naming convention for defining grating setups. R1200 - Red 1200 lines/mm grating

The new default gratings are:

B1200 - Blue 1200 lines/mm grating (old grating)

R1200 - Red 1200 lines/mm grating (new grating, better throughput)

B400 - Blue 400 lines/mm grating (new grating, better throughput)

R300 - Red 300 lines/mm grating (replacing old Red 300 lines/mm grating, better throughput).

The new default gratings setups are:

B1200(old grating)/R1200(new grating) and B400(new grating)/R300(new grating)

For reference, here is the old naming convention for the gratings

• Old "high" grating setup was B1200/R830

• Old "medium" grating setup was B600/R300

• Old "low" grating setup was B300/R150

Please do not use the old "high", "medium", or "low" grating terminology in your setups, instead use the specific gratings you want (if not the default gratings).

DIS III - Red Camera

• CCD is a Marconi 2048x1024 back illuminated CCD

• CCD pixel size = 13.5µm

• CCD gain = 1.89 e^-/ADU ±0.02

• CCD read noise = 4.12 e^- ±0.05

• Quantum Efficiency

• Wavelength	%
  350nm	40.0
  400nm	80.1
  500nm	94.3
  650nm	87.7
  900nm	30.6

• Dark Current: <1 e- / second

• Pixel scale = 0.40"/pixel binned 1x1

• Full well depth: 150k e^-

• Linear up to 64k, Saturation at 64K

• Schmidt camera f/2.7, focal length = 540 mm

• Readout time: approximately 47 seconds non-binned, full chip

DIS III - Blue Camera

• CCD is a Marconi 2048x1024 back illuminated CCD

• CCD pixel size = 13.5µm pixels

• CCD gain = 1.74 e^-/ADU ±0.02

• CCD read noise = 4.61 e^- ±0.05

• Quantum Efficiency

• Wavelength	%
  350nm	51.7
  400nm	79.3
  500nm	86.8
  650nm	81.0
  900nm	29.5

• Dark Current: <1 e- / second

• Pixel scale = 0.42"/pixel binned 1x1

• Full well depth: 150k e^-

• Linear up to 64k, Saturation at 64K

• Schmidt camera f/2.7, focal length = 540 mm

• Readout time: approximately 47 seconds non-binned, full chip

General Instrument Information

• Imaging Field of View: 4' x 6'

• Minimum Exposure: 1 second (must be integral seconds)

• Installed filters (User selectable): SDSS g', SDSS r'

• Readout time: approximately 47 seconds non-binned, full chip. Both chips are read out in parallel (no time savings in reading just one chip).

Slits

• Standard slits: 0.9", 1.2" w/2.0" wide occulting bar, 1.5", 5.0", open

• Available slits: Pinhole

• Slit length is 708 pixels (~300"/pix) blue / 756 pixels (~300"/pix) red (1x1 binning )

• Slitview FOV is 150" of slit length

Gratings:

*Designates standard grating setup with listed wave centers, other gratings and/or wavecenters avaliable by request.

**DIS R300 default wavelength changed from 7600A to 7500A October 12, 2007

Old Grating Dispersion can be found here.

For reference, here is the old naming convention for the gratings (Please use the new B400/R300new convention)

• The old gratings are still available by special request only.

• Spatial scale for Red gratings are : 0.40 arc-sec/pixel

• Spatial scale for Blue gratings are: 0.42 arc-sec/pixel

• incident angle = 69.5 deg

Collimator:

The collimator focal lengths on the blue and red side are both 963mm; the camera focal lengths are 140.3mm and 141.7mm on the blue and red sides respectively; the resulting reduction is 6.865 in the blue and 6.798 in the red (the measured values are within 1/2% of this value, and vary slightly with collimator focus).

The measured scales are 1.086 arcsec/pixel in the blue and 0.610 arcsec/pixel in the red. The beam diameter is 100mm, and the angle between the collimator and camera optical axes is 35 degrees. There are commands to centre given wavelength on the chips.

Optics:

• Dichroic cutoff at 5350Å

Taking Lamp Calibration Spectra

* Designates default gratings, other gratings avaliable by request.

(NOTE: Times in parentheses are "minimum" and "maximum" exposure times taken from results of testing of DIS after optics upgrades in 2002. The minimum times were chosen to yield S/N values of ~100 "at most wavelengths"; maximum times were chosen to avoid saturation.)

(Under Construction!) HeNeAr lamps are available on the truss for comparison arc exposures. Suggested exposure times for HeNeAr arcs are:

* Designates default gratings, other gratings avaliable by request.

(NOTE: Counts cited for arc lamp spectra are those in the brightest lines to reach a S/N of ~100K. Consult plots of arcs taken with DIS to determine whether these exposure densities are sufficient for your program. If taking arcs with the lamps separately, reduce exposures for Ne only by about half, increase exposures

DIS Slit Inventory

NOTES: 'Locations' were as of October 2004. "DIS" refers to slits which remain permanently availablein the so-called default slit wheel. This 'default' wheel also contains one open position for imaging-mode observations.