SBO 24-inch Boller & Chileens Telescope under dome.

SBO 24-inch Boller & Chivens Telescope under dome.

The 24-inch Boller & Chivens f/8 Cassegrain was installed in the dome of Sommers-Bausch Observatory in 1973. Originally equipped for visual viewing, 4x5 film photography, photomultiplier photometry, and glass-plate stellar spectroscopy, the 24-inch now utilizes CCD electronic technology to achieve the same results: astroimaging, spectroscopy, and photometry. 

For the first eight years of its life, the 24-inch was the sole telescope at SBO, and was kept busy seven nights a week with undergraduate observing sessions, graduate research, and public open houses. Now, it is used primarily by APS graduate students as a training and data-gathering instrument in preparation for observing runs at larger telescope facilities.

Beginning in Spring 2000, when the department major in astronomy was initiated, the 24-inch once again returned to heavy use as an undergraduate training facility for upper-division astronomy majors. In addition, since Summer 2015, the 24-inch (along with the now retired 18-inch) began to be used as part of the KELT-project, searching for exoplanets.

The original instrument to occupy the dome was the 10.5-inch Bausch telescope, which was installed in the new observatory building in 1953. The 25-foot diameter dome was necessary to encompass the long, f/15.5 refractor.

Now, with the much shorter 24-inch with folded optics, the dome offers plenty of elbow room, even after the installation of a false floor and separate instrument room (referred to as the Coude Room, even though the Coude focus has never been used). The mirrors one sees around the periphery of the dome are historical left-overs from the transition between the long-and-narrow refractor and its replacement short-and-fat reflector.

Looking in on the SBO 24-inch Boller & Chileens Telescope.

Looking in on the SBO 24-inch Boller & Chivens Telescope.

In order to fully appreciate the fine detail and workmanship that went into the Boller & Chivens telescope, one needs to take it apart - which we do, on occasion, to do some mirror cleaning.

The 24-inch has seen some well-known visitors in its time - including the captain of the starship Enterprise and the only human being to play a round of golf on the Moon. 

Telescope Specifications

  • Manufacturer: Boller & Chivens (1973) 
  • Design: Retchey-Cretien (modified Cassegrain)
  • Aperture: 0.61 m (24 inches)
  • Effective Focal Length: 4.877 m (192 inches)
  • Effective Focal Ratio: f/8
  • Plate Scale: 42.28 arc-sec/mm (85.17 mm/degree) (0.634 arc-sec per 15-micron CCD pixel)

Guide Scope Specifications

  • Aperture: 0.15 m (6-inch)
  • Focal Length: 2.44 m (96 inches)
  • F/ratio: f/16

Finder Scope Specifications 

  • Aperture: 0.10 m (4-inch)
  • Focal Length: 0.91 m (36 inches)
  • F/ratio: f/9

Currently Installed Filters

  1. UV/IR Cut (L)
  2. Sloan g'
  3. Sloan r'
  4. Sloan i'
  5. H-Alpha
  6. Red Continuum
  7. Transmission Grading

Spectrograph Specifications

  • Camera Optic
    • 210mm Focal Length
    • f/4
    • Mamiya-Sekor C Medium Format Lens
  • Grating
    • 450 grooves/mm
    • 3300A to 7500A
  • Slits
    • 20 micron / 0.8 arcsec
    • 28 micron / 1.2 arcsec
    • 40 micron / 1.7 arcsec
    • 56 micron / 2.4 arcsec
    • 80 micron / 3.4 arcsec

Illustration of the SBO 24-inch by Eric Maxwell Mc Neil Former Observatory Assistant.

Illustration of the SBO 24-inch by Eric Maxwell Mc Neil, former Observatory Assistant.