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Thermally Managed 10" Coulter Cassegrain

Discussion in 'Telescopes and Mounts' started by Scopejunkie, Feb 21, 2020.

Thermally Managed 10" Coulter Cassegrain

Started by Scopejunkie on Feb 21, 2020 at 11:08 PM

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  1. Scopejunkie

    Scopejunkie Well-Known Member

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    Scopejunkie, Feb 21, 2020
    #1
    Semi-new project. Yep, I’m experimenting again. I’m seeking to build a thermally managed 10” F/15 Cassegrain. The full thickness primary (Coulter Optics) is mounted like a refractor lens only supported on its edge. The front portion of the mirror cell has an outer felt seal isolating the side and rear of the primary mirror in its own chamber hopefully minimizing tube currents from primary mirror cooling process. The rear section of the mirror will be in a chamber allowing the naturally stored heat to flow passively out of holes in the tube never entering the light path. The Astro Physics 10” Maksutov shouldn’t have all the fun.

    Explain why the project is semi-new? Long story short: I built an open tube 10” Cassegrain that I sold. I shipped it against my own advice and the shipper broke it (professionally packed). The guy I sold it to had difficulty restoring the custom scope back to original condition even with the supplied replacement part to fix the scope (optics were fine). To me, it was not fair for him to suffer for the shipper’s carelessness. I bought the scope back and have now produced something different. Hope to share the “thermal” results. Fingers crossed.

    Still scope hacking…
     

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  2. Orion25

    Orion25 Well-Known Member

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    Orion25, Feb 26, 2020
    #2
    Wow! Great project, scopejunkie. Go for it! Keep us posted :D
     
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  3. Scopejunkie

    Scopejunkie Well-Known Member

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    Scopejunkie, Mar 16, 2020
    #3
    I finished detailing the tube of my 10" Coulter cass today. Interior and exterior paint were applied earlier in the week. Added front end edge trim and color tape. I plan to upgrade the vixen/cg5 dovetail to a CGE when it arrives later this week. Current weather: Snow. Come on spring!

    Still scope hacking...
     

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  4. Orion25

    Orion25 Well-Known Member

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    Orion25, Mar 17, 2020
    #4
    Cool beans! Do you build scopes as a sideline?
     
  5. Scopejunkie

    Scopejunkie Well-Known Member

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    Scopejunkie, Mar 17, 2020
    #5
    Thanks. Telescope making has been my primary hobby for over 40 years.
     
  6. Orion25

    Orion25 Well-Known Member

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    Orion25, Mar 18, 2020
    #6
    That's a wonderful hobby and a great skill. I always thought it was nice to be able to build things either you want to use or for someone else :)
     
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  7. Scopejunkie

    Scopejunkie Well-Known Member

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    Scopejunkie, Mar 18, 2020
    #7
    I've noticed that we ATM's seem to be "greying out." I still get great satisfaction from making my own scope stuff and helping others in the astro community. Keeps these old brain cells active ;) I'm now in the process of upgrading from the light weight Cave 1" mount to something a bit more substantial. I'm currently converting an old C14 wedge to a GEM. The basic drawings are complete and the parts have been ordered. The fabrication dust should be flying within the week. Wish me luck o_O Fingers crossed!
     

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  8. Scopejunkie

    Scopejunkie Well-Known Member

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    Scopejunkie, Mar 22, 2020
    #8
    The main parts are completed. Now the real fun begins o_O
     

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  9. Scopejunkie

    Scopejunkie Well-Known Member

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    Scopejunkie, Mar 25, 2020
    #9
    Upgrade in progress. My friend, and fellow ATM, Bob Schalck (AKA: Oregon-raybender) has
    graciously donated a Cave clock drive to this project. Now I need to design a tripod or pier that is strong but can still be handled by this old guy while I wait for the clock drive to arrive.
     

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    Last edited: Mar 25, 2020
  10. Scopejunkie

    Scopejunkie Well-Known Member

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    Scopejunkie, Mar 30, 2020
    #10
    She's got legs! Time to test all this out now that the skies have cleared. (clock drive coming soon)
     

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  11. Orion25

    Orion25 Well-Known Member

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    Orion25, Mar 30, 2020
    #11
    Sexy! ;)
     
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  12. Scopejunkie

    Scopejunkie Well-Known Member

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    Scopejunkie, Mar 31, 2020
    #12
    Clock drive installed. Time to do the remaining minor tweaks and detailing.
     

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  13. Orion25

    Orion25 Well-Known Member

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    Orion25, Mar 31, 2020
    #13
    Beautiful, SJ. You do excellent work :)
     
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  14. Scopejunkie

    Scopejunkie Well-Known Member

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    Scopejunkie, Apr 10, 2020
    #14
    To my surprise, I found the Cave clock drive case I attached to my ATM new mount to be very square to the polar shaft in both e/w and n/s so... I figured I should be able to attach a polar finder to it. After some minor brainstorming and CAD work, today I fabricated a "home brew" polar finder assembly (precision wood). The main plates are CNC machined and aligned to each other using 1/2" aluminum pins with matching CNC counter bored alignment holes in the plates. The pins have a "friction" fit. The finder scope is an old, but very good, Tasco 6X30 finder I had lying around. This polar finder setup should be good enough for general visual polar alignment//tracking. We shall see... The fun part is that this polar setup cost me nothing but time :cool:
     

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  15. Orion25

    Orion25 Well-Known Member

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    Orion25, Apr 10, 2020
    #15
    OMG, that looks just like the finder on my old Tasco reflector from the early 90s! You're bringing it back to life. Bravo!
     
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