A tip-tilt correction system for the 30-inch telescope

Abstract

Atmospheric turbulence degrades the image formed by ground-based telescopes. It causes the image to be spread over a large area known as the seeing-disk in a typical long exposure. In a short exposure, the image is spread into a bunch of speckles, each of angular size equal to the diffraction-limit. In short, there are two distinct components to image degradation. One is the motion of the overall image, and the other is the blurring of the image. The aim of this project is to develop a system that will arrest the overall motion of the image. The main objective of this project is to design, deploy and test a tip-tilt system (as a black box) at the 30-inch telescope at the Vainu Bappu Observatory (VBO), Kavalur, while at the same time retaining the existing on-axis imaging instrument with minimal change. In other words, the aim is to augment the 30-inch telescope with a tip/tilt correction facility as an additional, optional feature. Also, this project aims to test the ability to ”off-load” tip/tilt correction (provided by the fast piezoelectric actuator) periodically (e.g., every 1 minute) to the telescope control system (along the RA. and DEC. axes) and thus enabling tip-tilt correction from the piezoelectric actuators for long duration. (e.g., several hours). The major focus is to gain expertise and confidence in developing a tip-tilt correction system so that it can be easily extended to the 90-inch telescope having a similar f-number.