Why is this Space Telescope so Tiny?

Optical Engineer Rik ter Horst shows us how he makes very small telescopes (at home) which are intended for use in micro-satellites.
Contents:
0:00 Intro
1:06 About telescopes and focal length
3:35 The Cassegrain telescope
4:38 The Schmidt-Cassegrain telescope
5:18 The monolithic telescope concept
6:30 Rik ter Horst Interview
10:25 Riks' polishing setup
13:51 About manufacturing aspherics
16:50 Advantages of solid telescopes
17:49 Dreaming about a VLTT

ORESAT PROJECT CORRECTION. I was notified that the name of the university behind the OreSat project is erroneous: It is the "Portland State University" (https://www.pdx.edu/), not University of Portland. Sorry about that! Direct link to the Oresat project: https://www.oresat.org/

The video contains images of external sources. Please visit their websites for more information:
- Star party image was taken from: https://www.nps.gov/cebe/planyourvisit/star-party.htm
- More amazing astro-photos made by Dick van Tatenhoven can be found at: https://www.sterrenwachtalmere.nl/donateurs/dick
- NOVA-Astron website: https://www.astron.nl/about/organisation/nova/
- Yerkes telescope photo from: https://www.space.com/26858-yerkes-observatory.html
- Source of image at 0:41 is http://www.bxoptic.com/production-workshop/
- Image of the Schmidt plate and Cassegrain telescope taken from their respective Wikipedia pages:
https://en.wikipedia.org/wiki/Schmidt%E2%80%93Cassegrain_telescope
https://en.wikipedia.org/wiki/Schmidt_corrector_plate

Did I forget a reference? Objections? Please let me know and I will set it straight and add a link.

telescopemonolithictiny