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2.4 The 2.1-m GoldCam Spectrometer

The 2.1-m GoldCam spectrometer has proven to be one of the most popular spectroscopic instruments at Kitt Peak. While one cannot go as faint with it as one can with the 4-m on stellar sources, many programs simply need more observing time than can typically be accommodated during short 4-m runs. The total system throughput (telescope + spectrograph + CCD) is 15-18% under typical seeing conditions with a nominal slit width (24% peak throughput under excellent seeing conditions). GoldCam offers resolutions from 300 to 4500 using a variety of gratings. The detector in GoldCam is a Ford 3K x 1K CCD with 15m pixels and fairly good cosmetics. The full 5.2 slit projects to 400 rows, and so only half of the chip is used. The camera design does not give good focus over the entire 3K length, although we find that the central 2000 pixels are in relatively good focus. A TV camera views the slit, and guiding is accomplished using a second TV which is moved around the xy axis outside of the instrument field of view.

It is possible to rotate the slit to specific position angles at the 2.1-m, but doing so requires moving the telescope to zenith and must be done manually by the telescope operator. Allow a minimum of 10 minutes of overhead for each rotation.

The following table lists the available gratings and wavelengths coverage.

2.1m GoldCam Gratings
Name l/mm order Blaze Coverage(Å) Dispersion Resolutiona



(Å) 2000 pixels (Å/pixel) (Å)
201 150 1 5000 1 octaveb 4.85 13.1
250 158 1 3800 1 octaveb 4.60 12.4
400 158 1 6750 1 octaveb 4.60 12.4
09 300 1 4000 <4940c 2.47 6.7
32 300 1 6750 <4940c 2.47 6.7


2 3375 2480 1.23 3.3
58 400 1 8000 3800 1.90 5.1


2 4000 1400 0.95 2.6
240 500 1 5500 3040 1.52 4.1
26old 600 1 4000 2480 1.24 3.3
26new 600 1 4900 2480 1.24 3.3
35 600 1 6750 2480 1.24 3.3


2 3275 1240 0.62 1.7
56 600 1 11000 2480 1.24 3.3


2 5500 1240 0.62 1.7
47 831 1 8000 1800 0.90 2.4


2 4000 900 0.45 1.2

Notes: (a) Based on 2.7 pixels FHWM corresponding to 100 m slit (1.3 arcsec). Resolution will degrade to 3 pixels at 150 m slit (2 arcsec). (b) Spectral coverage limited by overlapping orders. (c) Spectral coverage limited by grating efficiency and atmospheric cut-off.

The grating efficiencies have been measured in the laboratory and are shown in Fig. 5

 
Figure 5:   The efficiencies of the various GoldCam gratings are shown in this figure.

2.4.1 Blocking Filters for GoldCam

There are a variety of order-separation filters available for use in GoldCam. These filters are listed below and their transmission curves are shown in Fig. 6 and Fig. 7.

Blocking Filters for GoldCam
Long cut-off Short cut-off
Filter Thickness Filter Thickness Filter Thickness
BG-1 1mm WG-320 2mm GG-455a 2mm
BG-38 1mm GG-345 2mm GG-475 2mm
BG-38 2mm WG-375 2mm GG-495 2mm
CuSO4 8mm WG-1 (WG-360) 2mm OG-530 3mm
KG-3 2mm GG-385 2mm OG-550 2mm
BG-1 1mm 3-75 2mm OG-570 2mm
BG-39 2mm GG-400 2mm RG-610 1mm
4-96 4mm GG-420 2mm GG-610 2mm


O-51 4mm RG-695 2mm


WG-420 3mm RG-695 3mm


GG-455 2mm

Figure 6
Figure 6: The transmission curves for the various GoldCam long- cut-off filters.

Figure 7
Figure 7: The transmission curves for the various GoldCam short- cut-off filters.


next previous contents
Next: 3 Estimating Exposure Times
Previous: 2.3 4-m Cryogenic Camera
Updated: 03Jun1997