What is a telescope dew shield?

Steve says: "Dew shields are metal or plastic extensions to a telescope’s optical tube. They serve two functions; to stop stray light entering the light path from oblique angles and to help keep dew at bay.


At first, a telescope cools down via the movement of air until it’s the same temperature as its surroundings.

However, after that, the glass elements continue to radiate heat away, which can cause dew to form.

A dew shield traps a pocket of air in front of the lens, helping to control the rate of this radiation and prevent dew from building up."

Follow our guide to make your own telescope dew shield.


Email Steve your astronomy queries to scopedoctor@skyatnightmagazine.com.


Astronomer Steve Richards
Steve RichardsAstronomer and author

Steve Richards is a DIY astronomy expert and author of Making Every Photon Count: A Beginner’s Guide to Deep Sky Astrophotography.