Cassegrain Telescope Walkthrough Video

How does a telescope collect and magnify light?

Check out the Cassegrain Telescope SIM at

Learn more about Mirrors at

View all of CK-12’s free, high-quality STEM resources at


Mark Tredway says:

Thanks so much!!! That was great!! Love the visuals!! Does the secondary mirror actually extend the standard focal length? I mean if it was a flat secondary mirror it would be a shorter focal length, right? Doesn’t the quality of the image get worse with each reflection too?

Soundharya Premanand says:

Thank you.

AGS-TECH Inc. - Custom Manufacturing says:

Well explained and simulated. Thank you !

Matthew Ferrie says:

Wouldn’t the secondary mirror look like it’s in the way, making a hole in the center of the field of view?

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