Thursday, August 17, 2017

Today's Hints for Beginning Amateur Astronomers

It can take along time for the glass in a refractor lens or reflector mirror to cool to ambient temperatures--even more for Schmidt-Cassegrain telescopes.  During that time, image quality will be awful.  If you have just acquired your first telescope and are underwhelmed, plan on giving it an hour (or two if a large one) before being disappointed.


  1. Why should the optics need to cool? That assumes the telescope is stored in an enclosure warmed above outdoor night time temperatures. If the telescope is stored an unheated enclosure, such as a garage or shed, it will be at ambient temperature already.

    And in some climates and seasons, indoor temperatures may be lower than outdoor temperatures, even at night. A warm summer night may be warmer than an air-conditioned house. In such a case, the observer may have to wait for the optics to warm to ambient temperature.

  2. If the outside temperature is identical, cooling is not required. But I have yet to have that situation. My telescopes are in a telescope garage, which because the building absorbs heat from the Sun, is always a bit warmer than the outside air. Palomar, as I recall, keeps its dome closed because it is air conditioned until shortly before use.