Telescope

Features, Optics & Parameters

The Aristarchos telescope (Ritchey-Chretien design) was constructed by the German company Carl Zeiss Carl Zeiss GmbH and was inaugurated in the summer of 2007. The telescope uses technology that is common in larger 8-10 m class telescopes. As a consequence the telescope’s positional accuracy is better than 2 arcsec, while it can follow targets with a positional offset better than a fraction of an arcsec within an hour.

The diameter of its primary mirror is 2.3 m. The field of view is about 10 arcmin in diameter at the sideport, and 1 degree diameter at the Cassegrain focus. The telescope can reach a limiting magnitude of V~24 in an hour of observation on a dark night, while the limiting magnitude for spectroscopy is about V~19 with the low resolution ATS spectrograph.

Telescope Features

Parameter	Value
Weight (moving parts):	29 tons
Total weight :	34 tons
Weight (tube):	14 tons
Weight (altazimuth platform):	7,4 tons
Weight (primary mirror):	2,617 tons
Weight (secondary mirror):	0,108 tons
Mounting system:	Altazimuth with 6 drives per axis
Balancing system:	Automated (ATB)
Encoding system:	2 tape encoders/axis (0.02″ resolution)

Optics

Parameter	Value
Optical system:	Ritchey-Chretien
Primary mirror diameter:	2280 mm
Focal ratio (primary):	f/2.4
Secondary mirror diameter:	740.7 mm
Focal ratio (secondary):	f/3.1
Final focal ratio:	f/8
Optical aperture:	2200 mm
Focal length:	17714.45 mm (corrected FOV) 17630.05 mm (uncorrected FOV)
Field of view RC-corrected:	1.04 deg (diameter 321.6 mm)
Field of view uncorrected:	10.1′ (diameter 52.8 mm)
Field of view (side port):	10.01′ (diameter 52.3 mm)
Image scale:	1″ = 85 microns (11.7″/mm)
Image quality on axis:	< 0.35″ (80% encircled energy, 350 nm – 1000 nm)
Focusing accuracy:	+/- 0.005 mm (secondary mirror movement)
Travel range:	+/- 10 mm (focusing mechanism)

Other Parameters

Parameter	Value	Parameter	Value
Range of movement:	+/- 200 deg (in azimuth)	Resonant frequencies:	16 Hz (fork), 21 Hz (tube)
Range of movement:	+/- 90 deg (in altitude)	Total weight capacity:	up to 300 kg of instrumentation
Range of movement:	max 2 deg per second (in azimuth)	Cassegrain weight capacity:	up to 300 kg of instrumentation
Range of movement:	max 2 deg per second (in altitude)	Side port weight capacity:	up to 100 kg of instrumentation
Pointing accuracy:	<4″ up to zenith distances of 70 deg	Operating temperature range:	-10 C to +35 C
Tracking accuracy:	<0.5″ in 10 min, 2″ in 1 hr (open loop)	Operating humidity range:	up to 80% relative humidity
Tracking accuracy:	<0.25″ in 10 min, 0.5″ in 1 hr (closed loop)	Wind tolerance:	up to 15 m/s (in operation)
Rotator tracking accuracy:	0.25″ in 10 min, 0.5″ in 1 hr	Earthquake resistance:	up to 2 m/sec2 in any direction
Radius of zenith blind spot:	2 deg

Acquisition and Guiding Unit (AGU)

The Acquisition and Guiding Unit (AGU) is mounted on the Cassegrain rotator of the telescope. The AGU provides 5 focal stations for the astronomical instruments, one for the corrected field with 1.05° diameter and four side looking focal stations for the field with 10arcmin diameter. The science fold Mirror directs the light from the telescope to any of the side looking focal stations.

The AGU also provides an offset guiding system (AGS). The AGS patrols a wide field to find bright stars, off axis from the target of interest to the astronomer.

All these functions are to be carried out with reduced vignette of the path of the science beam, or without introducing stray light or extra emission at the science focal plane.