Double Spectrograph (DBSP) Technical Specifications

View the original specs page.

Spectrograph status: Observatory Instrument

Contents

Collimators
Cameras
Scale
Detectors
Wavelength range
Single slit
Sensitivity
Dichroic filters
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″

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. Dichroic Filters

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

9. Gratings

	1^st 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

Questions? We've answered many common observing and operations questions in our observer FAQ page.
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DBSP Specs / v 2.1
Last updated: 09 Feb 2018 CMH