INSTRUMENTS

ASTRAL TELESCOPE

BASIC NOTES

page 20

CLEANING OF LENSES
A good objective is perfectly polished, but it has to be cleaned carefully so as to avoid spoiling it. Remember that optic glass is much more delicate than regular glass, and that it is therefore easily scratched.
The lenses should never be removed from their position except by an expert. Mirror objectives have to be kept in position but given a certain amount of extra space (you should hear a slight sound when the tube is shaken gently).
If the centering, that is, if the regulation of the screws, or of the locknuts, is too tight, the lenses can be put under pressure and a perfect definition will be mined.
When it becomes necessary to clean lenses or mirrors, they must first be dusted with a camel hair brush or by means of the special bellows.
Then, put some drops of solvent designed for photography objectives onto a clean chamois leather or onto a pad of cotton and polish the lens gently avoiding circular movements.

SUDDEN CHANGES IN TEMPERATURE
If possible, avoid taking the telescope form the cold air outside into a warm room. This will result in condensation forming on the lenses. It must be removed immediately. To do this, place the objective at a safe distance from a heat source and allow the moisture to dry out.
Every mark left on the lenses must be removed carefully once the lenses are completely dry.