40-inch Astrometric Reflector

The University of Virginia operates a 40-inch (1 meter) telescope at Fan Mountain Observatory, about 15 miles south of Charlottesville. The telescope is an astrometric reflector, originally designed for use with photographic plates as part of UVa‘s ongoing tradition of precision astrometry. In recent years, however, extensive hardware upgrades and instrumentation efforts have transformed the observatory into a more modern research facility capable of optical CCD imaging and stellar spectroscopy.

Specs

General System Data: Baker-Schimdt system

Effective focal ratio - f / 13.534

Effective focal length - 541.3764 inches (13.75096 meters)

View Optical layout

Focal Plane:
Cassegrain focus - Photographic Plates

Field Diameter - 8 inches
Angular Field Diameter - 50.8 arcmin
Plate Scale - 15.000 arcsec/mm

Focal Plane:
Cassegrain focus - SITe 2048 x 2048 CCD

Field Diameter - 2 inches
Angular Field Diameter - 12.3 arcmin
Plate Scale - 0.36 arcsec/pixel
Filter wheel 1 - 3 x 6" filters (Washington + DDO51)
Filter wheel 2 - 5 x 4" filters (UBVRI and H alpha + cont.)

Optics

General System Data: Baker system

Effective focal ratio - f/13.534
Effective focal length - 541.3764 inches
View Optical layout

(1) Corrector Lens: aspheric-plano

Outer Diameter - 43.5 inches
Thickness - 1.131 inches
Clear Aperture - 40 inches
Material - UBK-7

(2) Primary Mirror: aspheric

Outer Diameter - 43.5 inches
Inner Diameter - 14.0 inches
Thickness - 7 inches
Clear Aperture - 43.060 inches
Radius of Curvature - 651.64 inches
Material - ULE
Reflective coating - Aluminum

(3) Secondary Mirror: aspheric

Outer Diameter - 19.25 inches
Thickness - 2.5 inches
Clear Aperture - 19.00 inches
Radius of Curvature - 651.64 inches
Material - ULE
Reflective coating - Aluminum

(4) Focal Plane: Cassegrain focus

Field Diameter - 8 inches
Angular Field Diameter - 50.8 arcmin
Plate Scale - 15.000 arcsec/mm

Instrument

The 40-inch telescope is an astrometric reflector originally designed to continue UVa's long tradition of precision astrometry farther away from the growing Charlottesville area where light pollution was less of a factor. The telescope has an f/13.5 Cassegrain focus with a 15.0 arcsec/mm focal plane that is very flat over an area 8 inches in diameter. This large focal plane was useful during the telescope's earlier days when photographic plate imaging was done. The instruments used at the 40-inch today, however, make use of only the central portion of the focal plane.

Instrument	Description	Notes	Status
CCD Gen I	Direct SITe Generation I CCD Camera	A	Operational
CCD Gen II	Direct SITe Generation II CCD Camera	B	Operational
FOBOS	Single Object Fiber Spectrograph	C	Operational
EYE	2-inch Eyepiece	D	Operational

NOTES

A. The GenI camera is used for optical imaging. It houses a science grade, single amplifier SITe 2048x2048 CCD mounted in an IR Labs dewar controlled by SDSU CCD Laboratory Generation I electronics.

B. The GenII camera is used with the FOBOS spectrograph. It houses an engineering grade, quad amplifier SITe 2048x2048 CCD mounted in an IR Labs dewar controlled by SDSU CCD Laboratory Generation II electronics. Note, however, that the CCD is generally operated using either one or two amplifiers.

C. FOBOS is a single-object, fiber-fed spectrograph intended for moderate resolution stellar spectroscopy. Detailed information about the instrument can be accessed through the following link: FOBOS.

D. There is currently one eyepiece available for the 40-inch, used primarily for public outreach.

Filters

Two filter wheels in the telescope's tailpiece allow for five 4-inch filters and three 6-inch filters to be loaded simultaneously. Available filters include Johnson UBV, Cousins RI, Washington C, M, T1, and T2, DDO51, and H-alpha.

Additional filter information

The old control room WHITE BOARD (erased November 18, 2004), with historical focus data, etc.

Observing Tools