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Telescope Parameters:

System - F/4 Optical System Equatorial fork mount

Optical System :


Value / Description

Configuration Ritchey-Chretien
with Cassegrain focus
Pupil aperture Annular
Outer size : 1310.64 mm diameter
Inner size : 657.86 mm diameter
Telescope focal length 5149.6 mm (-F/4)
Plate scale = 40.0545 arcsec / mm
Primary mirror (M1) Hyperbolic
Secondary mirror (M2) Hyperbolic
Field Corrector Clear aperture : 236.22 mm diameter
Axial focal plane Circular : 101.6 mm diameter (~ 67.83 arcmin)
Operational wavelenght 350 nm to 2500 nm
Science field of view 66 arcmin unvignrtted field for axial port
Optical image quality 80% energy in less than 0.6 arcsec diameter;
(for 14 arcmin field of view with elevation range 40 to 90 deg and for the wavelength range 350 nm to 2500 nm)

Mechanical System:


Value / Description

Mounting Equatorial fork mount
Pointing accuracy < 10 arcsec RMS for any point in the sky for
zenith angle 0 to 60 degree
< 15 arcsec RMS for zenith distance down to 70 degree
Tracking accuracy < 0.5 arcsec for less than 10 min without auto-guider for
zenith angle 0 to 40 degree
Telescope motions Max. slew speed : 3 deg s-1
Guide speed (default) : 100 arcsec s-1
Set speed (default) : 5 arcsec s-1Smallest motor step : 0.1 arcsec s-1
Celestial objects having speeds from 0.001 arcsec/s to 3 deg/s are possible to track by setting RA and DEC rates.
Re-targeting time Less than 10 s for 2 deg move
Rotation freedom Final Software limit -1 : 72 deg zenith distance
Approaching software limit : 70 deg zenith distance
Hardware limit : 80 deg zenith distance in DEC and RA
(except 72 deg in south)
DEC Limits : -40 deg to +90 deg
HA hardware limit : +/- 11.5 hr
HA software limit : +/- 11.3 hr

Instrument Interface Unit :



Instrument envelope Cylindrical cum conical space of 1 m height below the M1 cell. A constant cylindrical diameter of 152 cm from cell to 20 cm and a decreasing conical diameter from 152 cm to 70 m corresponding to the distance below the cell from 20 cm to 1 m.
Mounting screws Four sets of 12 tapped holes (size-3/8-24) on the back of the mirror cell are provided for mounting instruments. The diameter of bolt circle are 19, 20, 24, and 36 inches.
Location of axial port Cassegrain focus 242.1 mm behind the cell (with filter)
240.2 mm behind the cell (without filter)
Maximum weight of the instrument 200 kg
Counterweights are provided to balance the telescope

Telescope Control System (TCS) :

The TCS is a software system that froms the interface between the telescope's hardware and the user.

The TCS consists of weather station, mount control system, and PC. The weather station shall measure dew point, air humidity, air pressure, wind speed and wind direction at the telescope level and it will send the information to the TCS PC through a RS 232 serial link. The TCS controls the motion af RA, DEC, M2 five axes housing, M1 mirror doors andthe roll-off roof. The TCS provides access to both the operational and engineering control of the telescope hardware and it also interface with the 5-axes M2 mirror housing, guiding unit system and the imaging instrument if any. It is installed on a dedicated industrial PC with in-built GPS card and with communication ports (TCP/IP, EXCOM, and MNCP) to communication with the observatory control system. The TCS is written in Turbo-pascal and it runs on the WINDOWS (XP) platform.

Image Quality of The Telescope :

The E80 will fall within 0.6 arcsec (equivalent FWHM PSF of 0.45 arcsec) for stellar images up to field of view of 1 degree. The stellar images with 1 arcsec FWHM were recorded on 23rd Oct 2010.