What is a telescope baffle?

BBC Sky at Night Magazine's Scope Doctor Steve Richards solves your astronomy ailments.

Altair 150EDF apochromatic doublet refractor. Credit: BBC Sky at Night Magazine

What is a telescope baffle?

Steve says: “Astronomers strive to obtain the maximum contrast that their telescope and eyepieces will allow so that dim objects stand out better against the night sky.

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Light pollution spoils contrast but so too does stray light bouncing around inside the telescope tube.

Baffles are frequently built into many telescope designs to stop this unwanted light from reaching the eyepiece by stopping it in its tracks.

A baffle is a ring made of thin plastic or aluminium that is attached to the inside of the optical tube and is painted in a black matt finish to further absorb unwanted light.

It is common for there to be several such baffles within the tube.”

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Email Steve your astronomy queries to contactus@skyatnightmagazine.com and they could be answered in a future issue of BBC Sky at Night Magazine.