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.
-Brian 14" Hubble Optics ATM Newtonian Paracorr II Ethos Eyepieces VE9WTH
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:Stephen, are you thinking of adding a layer to your 25" mirror, or is this a new project you are thinking about?
Quote:This thread:http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/3828920/Main...Has this:"One epoxy I've had my eye on is Masterbond EP30LTE-LO. This is a low CTE epoxy with low shrinkage
Quote:There used to be some small cemented apo refractors about but I understand that the size was limited to under 3ins due to shrinkage of the cement deforming the glass. Also as sizes go up differential expansion rates breaking the bond.It's a subject that interests me as I like the idea of a glass disc that is more or less self supporting. One idea I have which may work out is to grind a series of pockets into 2 discs made out of the same glass and bond them together with "pegs" leaving a space in between the discs. It might be possible to make the pegs out of borosilicate laboratory tubing for instance. Problem - what to use to bore the holes in the glass discs and how thick could the the bonding be?I feel that this could result in a very rigid light weight structure that could reach the same levels of performance as old style full thickness blanks.John-