Telescope Description

The Toppo Telescope #1 (TT1) is an 1.54m altazimuth telescope with a Ritchey-Chretien optical configuration. It is equipped with an active secondary mirror, designed specifically for optimal image quality. The TT1 is the first Alt-Az telescope in Italy.
The following tables show the main TT1 optical parameters:

Optics table
Value
M1 - Diameter/focus 1.537 m / 8.9
M2 - Diameter 0.545 m
Free vignetting area 87%
Scale 15.078 arcsec/mm
Resolution (optics + detector) 0.361 arcsec/pix

Telescope table
Value
Cassagrain focus F 8.9
Nashmit foci (not avaiable) F 11.5
Trapped focus (not avaiable) F 5.6
Range AZ +/-720
Range ALT 0-90
Pointing velocity AZ 1 deg/sec
Pointing velocity ALT 1 deg/sec
Max AZ traking error 0.07 arcsec
AZ traking error (rms) 0.02 arcsec
Max ALT traking error 0.1 arcsec
ALT traking error (rms) 0.02 arcsec

The telescope enclosure is ventilated by a system of flaps which optimize the air flow minimizing the dome and mirror seeing. All motors in the telescope environment and the hydraulic system are cooled to prevent heat input to the building. The volume under the floor is overpressurized and cooled with respect to the ambient. Motors, switchboards and any heat source are contained in this cooled interface/ambient. The upper surface of the telescope pillar is also contained in this volume. The building outside is insulated by means of a 5 cm thick insulation. The telescope floor and the telescope ambient are so insulated from the rest of the building.

The main feature of the TT1 is the presence of an Active Optics (AO) system: M2 is mounted on an exapod system (six expandable arms) used to keep the mirror in the correct position and tilt with respect to M1.
Both the thermal control and the active optics will contribute to the excellent image quality foreseen for the TT1. They will allow the TT1 optical quality to reach the ambient seeing.

The TT1 has a rigid construction due to the reduced mass of the primary mirror and telescope structure compared with classical telescopes. The goal is a very accurate pointing of 1.5" r.m.s. over most of the sky. Degradation occurs close to the zenith and at zenith angles larger than 70.
Tracking accuracy at 0.1" will match the overall image quality of 80% energy in 0.23" diameter.