-Brian 14" Hubble Optics ATM Newtonian Paracorr II Ethos Eyepieces VE9WTH
Quote:Tube thickness is the thickness of the panel that your focuser will be mounted on, NOT the ring thickness. You have the next 3 questions right. Not sure how much, if any, extra backfocus you need for the paracorr
Quote:A Paracorr needs about 1/2" of infocus. I usually put the focal plane about 3/4" above the fully racked in focuser height if it is a scope that will use a Paracorr.JimC
I am from New Zealand under nice dark southern hemi-sphere skies.Been in and out of astronomy and telescope making for 50 years now. Slogan: The heavens declare the glory of God. Scopes: 6" f6.5 Newt. 14" f5.09 Hubble Optics powered Dob. 25.2" f4.68 Strut Dob.(Home grown primary) Eyepieces. ES82 30mm,24mm,11mm 8.8mm.TV Nagler 20mm type 2.TV Plossl 7.4mm.Some GSO eyepieces and barlows. WO Binoviewers.
Quote:Astrosystems has excellent spiders and secondary holders, but for the secondary itself I like to have one that comes with test data. That pretty much limits the choice to Protostar or Antares Optics. Protostar also makes nice spiders/holders but their delivery times have been quite long. Maybe they are caught up? Anyone ask them at NEAF?JimC
Quote:Astrosystems has excellent spiders and secondary holders, but for the secondary itself I like to have one that comes with test data. That pretty much limits the choice to Protostar or Antares Optics.
Quote:To be conservative, you can treat the mirror as a solid mirror with equivalent thickness of 1.2"
Quote:Hi Brian, I just noticed this thread or I would have replied sooner. I also built a truss dob for a 14" Hubble Optics sandwich mirror, completed last October.
The thread for my build is here:
Quote:I ended up with an 18pt cell
Quote:One issue I ran into with the 14" HO mirror is that it only weighs 18 lbs (compared to a full thickness mirror at around ~25lbs). So keep that in mind when you are deciding on the height of your mirror box, or you could get into trouble with balance issues.
Quote:Another potential gotcha is when calculating the tailgate dimensions, measure the actual diameter of the mirror to account for the ~3/16" bevel around the circumference.
Quote:I would like to rebuild my mirror cell so that I can use 45 degree edge supports.
Celestron 8SE Dobstuff 13.1": Swayze refigured Coulter mirror, 6 pt mirror cell (2 pt edge support) and CF focuser board made by me StarBlast 4.5 ST80/PortaMount II Zhumell 20x80/Oberwerk 15x70 on a Seronik-style tripod boom mount Hubble Optics 18 inch F/4 mirror.
Quote:I have to admit, I stole a few of your ideas from that thread.
Quote:In using PLOP you should use the actual thickness of the sandwich mirror for the mirror thickness
Quote:A couple of them didn't go in straight, they seem to be tipped to one side. Any way to straighten them out?
-DannyMy warehouseMy Channel
Quote:to straighten them out they will have to go deeper as you straighten them.
Quote:I used the Stellarvue finderscope mounting ring kit (#R50A) they recommended for dobs
ATM 13.1" reflector Sky Watcher BK 120 ED Orion 80 ED HEQ5 Pro and EQ6 Pro Modded Rebel XT and T3i unmodded KWIQ Guider http://www.pierresplace.ca
Quote:I'm going to use 3/8" bolts for collimation and am thinking of going with the Belleville springs. On McMaster Carr there are many different springs for this size with different load ratings..from 110 lbs to 597 lbs. Which would be ok for an 18lb mirror? I don't want to buy something that a tank could drive over and not depress...or something too mushy either