T15 0.80 meter APT

Observing Program

Design and contruction of the T15 0.80m APT was done by Lou Boyd at Fairborn Observatory and Mike Williamson at Tennessee State University. The telescope became operational in the Fall of 2020 at Fairborn. Like the T8 APT, T15 measures stellar brightnesses in the standard Stromgren b & y photometric system with a two-channel photometer. Funding for the construction of the telescope came from NSF and Tennessee State University.

For the next several years, T15 will be used to observe ~100 exoplanet candidate host stars being observed with the NSF-funded EXtreme PREcision Spectrograph (EXPRES), designed and built at the Yale Exoplanetary Laboratory and installed on the 4.3-meter Discovery Channel Telescope operated by Lowell Observatory. EXPRES can make radial velocity measurements with a precision of 10-15 cm/sec. The joint EXPRES/APT project is searching for planets that are similar in mass to our Earth that orbit their host stars at a similar distance where liquid water can exist on their surfaces. These planets will be the targets of intense searches for life outside the solar system. See Zhao et al. (paper) and Brewer et al. (paper) for more information.


  • 31.5-inch Cassegrain optics of sitall by Star Instruments
  • Primary focal ratio is f/2; effective focal ratio is f/8
  • Horseshoe equatorial mount with tripod secondary mirror support
  • Disk and roller drive systems on both axes
  • High-precision, two-channel photometer with dichroic beam splitter
  • Stromgren by filters
  • Neutral density filters with attenuation of approximately 1.25, 2.5, 3.75, and 5.0 mag.
  • Selectable diaphragm wheel with diameters of 30, 45, & 60 arcseconds
  • Two EMI 9124QSB photomultipliers
  • PMTs, voltage divider, preamp, and filters in sealed, environmentally-controlled chamber
  • New CoATIS control system