JAST/T80 Telescope

JAST/T80 Telescope Image

JAST/T80 Telescope Image

The Javalambre Auxiliary Survey Telescope (JAST/T80) is an 80cm, F#4.5 telescope with a german-equatorial mount and a Ritchey-Chrétien optical configuration. The focal plane corresponds to a Cassegrain layout with a field corrector of 3 spherical lenses of fused silica in the range 115 – 140mm. The distance between M1 and M2 is 0.83m, and the back focal distance is 160mm. The JAST/T80 field of view has a diameter of 1.7 deg (110mm) with full optical performance, reaching the 2.0 deg (130mm) diameter with a slight vignetting (< 1%) and slightly degraded image quality. The baffling system consists of three conical baffles. A summary of the main technical specifications of JAST/T80 are given in Table 1.

Table 1. Main technical specifications of the JAST/T80 telescope at the OAJ.
Optical configuration Ritchey Chrétien
M1 diameter 83cm
FOV diameter 2deg (130mm physical size)
Effective collecting area 0.44 m2
Etendue 1.5m2deg2
Focal length 3712mm
F number 4.5
Plate scale 55.56 arcsec/mm
Mount German equatorial
Focus Cassegrain

In order to guarantee an optimal image quality all over the FoV of the telescope, M2 is supported and controled by an hexapod actuator. This allows to perform fine corrections of the M2 position in piston, x-y decentring and tip/tilt to compensate temperature changes and/or mechanical flexures at different telescope pointings. To do this, an empirical M2 control law has been constructed and implemented.

JAST/T80 has an approximate mass of 2500 kg, and is able to support instruments of up to 80 kg at 25cm from the mounting flange. The first light panoramic instrumentation of JAST/T80 is T80Cam, with a large-format 9.2k x 9.2k CCD and a set of 12 broad, intermediate and narrow band filters.