Double Spectrograph (DBSP) Technical Specifications

View the original specs page.

Spectrograph status: Observatory Instrument

Polarimeter status: Observatory Instrument


    Contents

  1. Collimators
  2. Cameras
  3. Scale
  4. Detectors
  5. Wavelength range
  6. Single slit
  7. Sensitivity
  8. Polarimeter
  9. Dichroic filters
  10. Gratings

1. Collimators

  • Red focal length: 91 inches
  • Blue focal length: 91 inches

2. Cameras

  • Red focal length: 12 inches
  • Blue focal length: 9 inches

3. Scale

  • 2.57″/mm at the slit
  • 0.293″/pixel for the red camera (new LBNL CCD)
  • 0.389″/pixel for the blue camera (CCD 23)

4. Detectors

  • Red: New LBNL CCD; 4096 × 2048; 15µm pixels; linear to 40,000 DN; saturation 45,000 DN
  • Blue: CCD 23; 2048 × 4096 (in the 4096 dispersion axis; rows 575 thru 3410 are un-vignetted); 15µm pixels; linear to 62,000 DN; saturation 65,000 DN

5. Wavelength Range

  • Red: 4700 Å – 11000 Å
  • Blue: < 3000 Å – 7000 Å

6. Single Slit

  • Length: 128″
  • Width: ½″, 1″, 1.5″, 2″, 4″, 6″, 8″, 10″

7. Sensitivity

A rough rule of thumb is that the sky-to-detector throughput is 12%, regardless of the choice of dichroic filter and grating. A star with a monochromatic AB magnitude of 10 will give 2100 detected photons/Å/second. More detailed sensitivity curves for different combinations of dichroic filter, grating, and grating angle may be found here.

8. Polarimeter

  • Linear polarization: 3200 Å – 10000 Å
  • Circular polarization: 3800 Å – 8500 Å
  • Single slit only
  • Maximum slit length 35″
  • Representative exposure:
    • Quasar V=18; 15 min at each of 4 position angles for 0.5% accuracy in P when smoothed to 20 Å.
  • Data reduction (off-line): See M. Cohen for VISTA-based program.

9. Dichroic Filters

Designation Red/Blue Transition Info
48 4800 Å
52 5200 Å graph
55 5500 Å graph
68 6800 Å

10. Gratings

1st Order Dispersion (Å/mm) [a]
lines/mm Blaze (Å) Red Cam Blue Cam
158 7500 202 I 134 II
300 3990 140 I
316 7500 102 I
600 4000 72 I
600 10000 54 I
1200 5000 26 I 36 I
1200 7100 26 I 36 I
1200 9400 26 I 36 I
[a] Roman numeral refers to the order

Please share your feedback on this page or any other Palomar topic at the COO Feedback portal

DBSP Specs / v 2.1
Last updated: 28 March 2016 ACM/AFB