NOAO is operated by the
Association of
Universities for Research in Astronomy
(AURA), Inc. under cooperative agreement with the
National Science Foundation
A description of the telescope and spectrograph follows. For more details the Coude Spectrograph Instrumentation Operation Manual may be consulted (http://www.noao.edu/kpno/manuals/coude/coude.html).
The configuration of the mounting causes vignetting at declinations north of +70 degrees.
Image quality - While not easy to measure, seeing of 1 arc-sec or slightly better can be obtained. Image jitter of a few tenths of an arc-sec is noticeable in good seeing due to the digital drive. Wind buffeting can induce considerable image motion.
Pointing - Approximately 10 arc-sec RMS after pointing map.
Field of view - Variable with TV zoom lens, up to 3 arc-min.
Acquisition and Guiding - Acquisition and guiding are presently done with an intensified CCD TV camera viewing the slit at all times. A zoom lens on the TV enables a variable slit magnification and field of view. Stars down to about V = 14 are visible with the TV. This description is provided for performance information only. The zoom lens but not the TV camera itself is offered with the telescope.
Collimators - Two f/31.2 collimators are present with diameters of 221 mm and 325 mm. The choice of collimator is usually determined by the grating size.
Gratings - The five available gratings are described in the table below. Note that the echelle grating must be either cross-dispersed or used with narrow band order sorting filters to be of use. Cross dispersion is presently accomplished with a set of grisms borrowed from the 4m Cryocam. These grisms will be available to coude users except when needed by the 4m Cryocam.
The grating wavelength setting is done with the telescope control program.
Coude Spectrograph Gratings
------------------------------------------------------------------------
grating A B C D Ech
gr/mm 632 316 600 1200 31.6
blaze (A),1st ord. 12,000 12,000 8000 8000 562,560
resolution* 28,500 13,500 17,100 35,100 116,000
integ. time (s)** 140(2) 99(3) 125(2) 258(2) 5200(125)
collimator large large small small small
-------------------------------------------------------------------------
*for 2 x 15 micron pixels
**for camera #5, B=10, s/n=25, in order (n) at 4500A
These integration times assume a quantum efficiency of 80% at 4500A and a slit width of 1.8 arc-sec. For camera 6, the resolutions are about 3 times higher, but integration times could be 6 - 8 times longer as the slit width would need to be reduced to realize the higher resolution.
Cameras - Cameras 5 and 6 are described in the table below. Camera 5 is a folded Schmidt design with the CCD dewar mounted behind the spherical mirror. It has interchangeable correctors for red or blue wavelengths.
Camera 6 is a classical lensless Schmidt with the CCD dewar mounted below the focus and perpendicular to the camera axis. A small pickoff mirror diverts the beam into the dewar.
Coude Spectrograph Cameras
---------------------------------------------------------------
camera camera 5 camera 6
type folded Schmidt lensless Schmidt
f-ratio 3.6 16
focal length (cm) 108.0 365.3
demagnification
-small col. 6.3 1.9
-large col. 9.4 3.0
The control system has provided consistently reliable and low-maintenance operation for this telescope.
For further technical information about the telescope and spectrograph, please contact Daryl Willmarth, dwillmarth@noao.edu.
| webmaster@noao.edu Posted: 05Apr2000 |
 |
 |