Watcher is a robotic telescope located at Boyden observatory, near Bloemfontein in South Africa (GPS: -29.0381°, 26.4050°) run by the Space Science Group at UCD, in Dublin, Ireland (PI: L. Hanlon).
It has been in operation since 2006 with the main scientific goal to rapidly follow-up GRB afterglows and to provide supporting optical observations for sources of interest of high-energy telescopes e.g. Fermi, INTEGRAL, Swift, XMM-Newton and HESS. When no GRB is being followed, Watcher typically monitors blazars, novae, asteroids and other interesting targets upon request.
The declination limit given by the geographical location is about +40° (assuming a minimum source elevation of 15° above the horizon). There are about 200 clear nights a year, with seeing typically around 2 arcseconds.
Watcher is a 40 cm Cassegrain telescope of a focal length f/14.25 and a field of view of 8×8 arcminutes. The telescope pointing is controlled by a Paramount mount and it is equipped with a filter wheel capable of switching between the standard Bessell BVRI filters and an open slot.
The focal plane instrument is an Andor EMCCD camera cooled to -80 °C, that can reach a limiting magnitude of approximately 18th magnitude in a 30 second exposure in R band in standard mode, or the same in a 5s exposure in electron multiplying mode.
The Watcher telescope is fully robotised, operated by the RTS2 software package. This open source software provides automatic remote control over the telescope components and the additional devices, such as the weather station, robotic focuser, dome controller, web camera, etc. In the autonomous mode, the RTS2 scheduler also calculates in real-time an optimal observing plan and listens for incoming GRB alerts.
Since 2013, Watcher has been fully integrated into the GLORIA robotic telescope network. You can follow Watcher on Twitter @WatcherTele or find out more at the telescope website.