Meade DS-2114AT-TC.How do they get 1000mm focal length when distance from mirror to focal point is only half that?Are they counting length of the tube before the light hits the mirror?

Answers:

From: Bill

the light enters the front of the telescope, hits the rear mirror and is reflected to the front mirror which shoots the light up through the eyepiece. thus, focal length is the distance from the front of the telescope to the back plus the distance from the back to the front mirror. so the answer to your question is yes, they are counting the length of the tube before the light hits the rear mirror. that is also true of schmidt-cassegrains, maks and any other reflectors. they just have a piece of glass at the front of the scope to direct the light differently to the primary mirror. yous still count the initial length of the tube before the light hits the primary.

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