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John S. Hall Telescope

gr/42inch.jpg

With funding from the John M. Wolff Foundation (for the primary mirror blank) and the Friends of Lowell Observatory, the newly refurbished Hall Telescope is again operational for astronomy research at Anderson Mesa, AZ. Lowell Observatory photo.

The 42-inch John S. Hall Telescope was built for Lowell Observatory by AstroMechanics of Austin, Texas and installed at Anderson Mesa in 1971. Named in honor of the Observatory's 5th director, this fork-mounted telescope has just undergone a substantial modernization and is now equipped with new optics, including a lightweight Hextek primary mirror. The telescope has an f/8 Ritchey-Chretien optical configuration, and is equipped for CCD imaging, photoelectric photometry, and spectroscopy.



Lowell Telescope Specification chart

Perkins 72" Hall 42" LONEOS 31" 21"
Longitude 111° 32' 09.3" 111° 32' 07.9" 111° 32.2' 111° 32' 09.0" 111° 39' 59.2"
Latitude +35° 05' 48.6" +35° 05' 48.3" +35° 05.8' +35° 05' 54.6" +35° 12' 10.4"
Altitude 7236ft. (2206m) 7236ft. (2206m) 7236ft. (2206m) 7243ft. (2208m) 7260ft. (2213m)
Dp 72" (1.8m) 41" (1.04m) * 31/29.5" (0.79/0.75m) 20.78 (0.53m)
F/# 17.5 8.06 * 15 15.9
EFI 1256.5" (31.93m) 330.39" (8.392m) * 464" (11.78m) 332.5" (8.44m)
Scale ("/mm) 6.45 24.58 * 17.5 24.3
BFI 51.5" (1.30m) 29.9" (0.759m) * 25" (0.63m) 20" (0.51m)
Fp/# 4.18 4.05 * 5.0 3.4
FLp 300.6" (7.635m) 166.06" (4.218m) * 155" (3.94m) 70.0" (1.77m)
Dsa 16.3" (0.41m) 16.6" (0.422m) * 9.0" (0.22m) 4.6" (0.12m)
Is 284.1" (7.22m) 130.43" (3.313m) * 134.9" (3.43m) 72.7" (1.85m)
Os 68.0" (1.72m) 65.51" (1.664m) * 45.1" (1.14m) 15.3" (0.39m)
Ms 232.6" (5.91m) 100.56" (2.554m) * 109.9" (2.79m) 54.7" (1.39m)
mag 4.2 1.990 * 3.0 4.7
K1 -1.0 -1.306 * -1.00 -1.00
K2 -3.65 -14.945 * -5.01 -3.35

1) Longitude and latitude are good to about 0.2.
2) The altitudes are good to about 1 meter.
4) The Hall F/8 is a Ritchey-Chretien telescope.
5) The 31inch primary if F/5. However, it is stopped down to 29.5 inches.
6) Only the Hall F/8 has a known optimum back focal distance.
7) The conic constant is defined such that 0 is a circle and -1 is a parabola.
8) Dsa is the diameter of the axial cone at the secondary. The diameter of the secondary is 1 to 2 inches larger than Dsa.

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