3.1 Photometry

Since the discovery of the first indications of starspots, photometry remains the most common technique for studying stellar activity. Thanks to efforts of individual observers, more or less regular observations of spotted stars began in 1970’s. They are currently supported by a great number of Automatic Photometric Telescopes (APTs) which provide every-night routine measurements for a big sample of stars. At present, more than a dozen APTs with apertures of 20 cm to 1.2 m operate around the world (see Table 1). The accuracy of ground-based APTs is about 2 – 5 mmag.

Table 1: Automatic Photometric Telescopes collecting data for studying starspots. Remarks: * Villanova, Cidadel, Charleston College, University of Nevada; ** Franklin & Marshal College; + University of Indiana; ++ Copenhagen Observatory; # University of Vienna.
Observatory/APT Location Aperture Filters
Catania Mt. Etna, Sicily × 80 cm UBV
Fairborn Patagonia, Arizona 25 – 80 cm UBV
Four-College* Patagonia, Arizona 80 cm UBVRI
Phoenix 10** Patagonia, Arizona 25 cm UBV
SAAO Sutherland, South Africa 75 cm UBVRI
SpectraBot+ Morgan-Monroe, Indiana 1.25 m UBVRI(CCD)
STELLA II/AIP Teide, Tenerife 80 cm UBVRI(CCD), uvby, Hα
Strömgren APT++ La Silla, Chile 50 cm uvby, Hβ
Wolfgang-Amadeus# Patagonia, Arizona × 75 cm VRI, by

A vast amount of photometric data have been also obtained by the ESA mission HIPPARCOS with the accuracy down to 1 mmag (van Leeuwen et al., 1997). Future space missions aiming at studying stellar oscillations and detection of earth-size exoplanets will also provide immense high-precision photometry of nearby stars which can be used for studying starspots:

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