Tennessee State University operates several Automatic Photoelectric Telescopes (APTs) located at Fairborn Observatory in the Patagonia Mountains of southern Arizona. The APTs are dedicated to photometric monitoring programs that would be difficult and expensive to accomplish without the advantages provided by automation. I describe the operation of two of the telescopes (0.75 and 0.80 m APTs) and the quality‐control techniques that result in their routine acquisition of single‐star differential photometry with a precision of 0.001 mag for single observations and 0.0001–0.0002 mag for seasonal means. I show that a primary obstacle to photometry at this level of precision is intrinsic variability in the comparison stars. Finally, I illustrate the capabilities of the APTs with sample results from a program to measure luminosity cycles in Sun‐like stars and a related effort to search for extrasolar planets around these stars.
Gregory W. Henry 1999 PASP 111 845