1 / 24

Telescope Making

Telescope Making. Mike Lockwood March 25, 2002. What is a Telescope?. 1) Optics 2) Structure to keep optics stationary with respect to each other (to high tolerance!!) 3) Mechanism for aiming the whole thing Sounds like a big heavy object However, it must be portable and move easily. .

diata
Download Presentation

Telescope Making

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Telescope Making Mike Lockwood March 25, 2002

  2. What is a Telescope? • 1) Optics • 2) Structure to keep optics stationary with respect to each other (to high tolerance!!) • 3) Mechanism for aiming the whole thing • Sounds like a big heavy object • However, it must be portable and move easily.

  3. Optics - Newtonian • Primary mirror • Focuses light from  at a point • This requires a parabola shape, paraboloid

  4. Optics - Newtonian • Secondary mirror • Flat, reflects light to eyepiece

  5. Optics – Make or Buy? • Highest quality • Hand made by experts or amateurs • Good quality • Machine made by big companies • A 6” – 8” mirror is a good first mirror, 12” or larger requires skill and practice • Grind with carborundum, aluminum oxide, cerium oxide, jeweler’s rouge

  6. Making Optics - Grinding • Grinding – “Pushing Glass” • Randomness cancels out in theory to provide a nice spherical shape….. hopefully

  7. Making Optics:Polishing, Figuring • Polish mirror after grinding ~ 1 hr. / inch • Figuring is the process of getting a mirror to paraboloid shape (but first to a sphere) • Done by polishing on a “pitch lap”

  8. Testing • Focault tester • “Knife-edge” • Precision of 1/1000th inch in knife travel yields 1/1,000,000th inch surface accuracy

  9. Bad Figuring – “Dog Biscuit” – Mirror making gone wrong

  10. Building a Portable Newtonian • Old telescopes were heavy, cumbersome • Large mirrors have become common, so a new design was needed to accommodate portable amateur scopes

  11. Equatorial Mounts • Required for most photography, but heavy and not really needed for visual astronomy

  12. The Classic “Dob” • Made from readily available, cheap materials • Portable • Resembles a cannon (to cops late at night)

  13. Components of a Dobsonian • Common parts, made of Sonotube, plywood • Optics, spider, focuser available

  14. Many Variations – location?

  15. Mirror Cell • Holds mirror, provides adjustment of angle • For smaller mirrors, glue works fine

  16. Mirror Cell – going in

  17. Mirror Cell - installed

  18. The “Light Bucket” Dilemma • How do you build and transport a really big Dobsonian with a tube? • Answer: Buy a Mack truck • Big tubes = big $$, big weight, flexing • What do I mean by really big?

  19. Okay, this is really big.

  20. Truss Tube Dobsonians • Truss maintains alignment between primary mirror (in mirror box) and the secondary mirror and focuser (in diagonal cage) • Rigid, lightweight • Clamp, bolt, screw together • Make them the same length, and they’re interchangeable

  21. Components • Mirror box • Holds, protects mirror, can have a finder on top • Attaches to truss tubes • Diagonal cage • Attaches to truss tubes • Holds diagonal mirror, finder (sometimes), focuser

  22. What materials, skillsand tools are needed? • Optics, spider, focuser, finder – specialty • The rest: Plywood, formica, bolts, screws, tubes, misc. metal • Skills: Carpentry, common sense • Tools: Circular saw, jigsaw, drill, hacksaw • Nice things to have access to: table saw, drill press, belt sander

  23. Astrofest – Telescope Showcase:

  24. My Scope: Details • 10”, F / 6.8 • Built in 1992 • Cost: $250 • Hours: ~ 200 • Weight: ~ 80 lbs • Height: At zenith, ~ 6’ 4” • Building it

More Related