Keeler Memorial Reflector

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Main Optical Tube


Primary Mirror

Diameter: 29 inches
Focal Length: 179.5 inches
Focal Ratio: f/6

Secondary Mirror

Diameter: 11.5 inches

Optical System (Richey Critien)

Focal Length: 449 inches
Focal Ratio: f/15

Finder Scope

(Schmidt Cassegrain)

Diameter: 10 inches
Focal Length: 63 inches
Focal Ratio: f/6.3
Eyepiece: 34 mm
Power: 47 x
Under the second largest dome is the Keeler Memorial Reflector.  It is named after James Edward Keeler, the second director of the Allegheny Observatory.*   The Brashear Company also built this telescope and it was operational by 1906 (six years before the building was finished).  Friends of Keeler provided the funds for the construction of the telescope.  For many years the Keeler was used with the Porter and Mellon spectrographs, the former to study the sun and the latter to study the stars, it collected the spectra of some 11,000 stars.

In 1992 the mirrors of the Keeler were replaced.  The new mirrors are made from a Russian version of Cervit, which has an extremely low thermal expansion coefficient.  The optical system was also changed to an f/15 Richey Chretien system.  This system was chosen because of its resistance to coma, a common optical problem associated Cassegrain reflecting telescopes.  It also "gives a field both larger and flatter than that produced by an ordinary reflector."  Thus making it an ideal telescope for astrometry. 

Sadly, due to grant constraints the Keeler is currently under subscribed.

* Many consider Langley as the first director.  Philotus Dean the man who preceded him was more of a caretaker and did no real research.            

Instrumentation:  Gallium Arsenide Photometer,   SBIG ST-2000XM CCD Imaging Camera



University of Pittsburgh
Department of Physics & Astronomy
Allegheny Observatory
159 Riverview Avenue
Pittsburgh, PA 15214

Last Modified 05/28/2003