T2 0.25 meter APT

(Decommisioned July 2007)

Observing Program

The Fairborn T2 0.25m APT began operations in early 1986 at the Fred Lawrence Whipple Observatory (FLWO) on Mt. Hopkins in southern Arizona, which is operated jointly by the Havard-Smithsonian Center for Astrophysics and the University of Arizona. It was relocated in 1996 to Fairborn Observatory's new site at 5500 ft in the Patagonia mountains near Washington Camp, Arizona. Operation of the Fairborn 0.25m APT was supported by FLWO (during its tenure on Mt. Hopkins), Fairborn Observatory, and Tennessee State University.

Until 2001 (16 years), the telescope was dedicated primarily to long-term photometric monitoring of semi-regular pulsating variable stars. These stars typically have magnitude ranges of a few tenths of a magnitude and timescales of variability from weeks to years. Many of the semi-regular variables exhibit two or more distinct timescales of variability.

The telescope was out of operation during the 2001-02 and 2002-03 observing seasons. During that time, the original OS9 operating system was replaced with a new Linux-based system and ATIS93 control system software. The original photodiode detector was replaced, a CCD camera was added for star acquistion and centering, and temperature stabilization of the photometer and CCD camera was implemented.

The upgraded telescope became operational for the 2003-04 observing season. The new Science Program included intensive monitoring of the Be star Gamma Cas and observations of young solar-type stars from the SIRTF Legacy program "Formation and Evolution of Planetary Systems" to measure rotation periods. The telescope was decommisioned July 2007, after 20 years of automated operation, to make room for a new APT.


  • 10-inch Schmidt-Cassegrain optics and tube assembly from Meade Instruments
  • Equatorial fork mount from DFM Engineering
  • Micro-stepping Berg belt to disk & roller drives on both axes
  • SSP-3 photometer with photodiode detector from Optec, Inc.
  • Active temperature control of photometer, filters, & CCD acquisition camera
  • Observes stars between 2.0 and 9.0 mag in Johnson VRI pass bands
  • Detector in focal plane and masked to 80 arcseconds diameter
  • ATIS93 automatic control system by Fairborn Observatory
  • External precision of a single observation is 0.01 mag or better.