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More TMB 92mm Details

Started by jkurtz555, 05/12/2006 05:54AM
Posted 05/12/2006 05:54AM Opening Post
Thomas Back on his Yahoo site mentioned the following regarding his new 92mm refractor:
1-Price will be $699 including 2 speed focuser.
2-Describes scope as APO (said Roland took a look but didn't comment). Described looking at Moon with no color present.
3-Scope is F/7
4-Scope will be previewed at the Black Forest Star Party (I assume in production form).
Thomas has far more credibility with me so I'm actually hopeful this could become reality. Does sound great!
Posted 05/12/2006 06:04AM | Edited 05/12/2006 06:05AM #1
Jeffrey, you got that right!!! i'm on this puppy come august. Er, if it happens. smile
Posted 05/19/2006 12:15PM #2
OK, after going over my own memories of the discussion, and checking with bill, i can hopefully clear up the brick/aspheric saga:

While I was at NEAF, chatting with Bill and Tom, they indicated that:

1) the 92mm aperture was more out of neccessity than choice. bill wanted to do something other than 80mm, as there are tons of 80mm scopes now, andthe shop had tooling setup for a 95mm
blank (resulting in a 92mm clear aperture lens), so they made a run of ten lenses. these are the first "brick" design prototypes (type II, see below), to do proof-of-concept. the f/ratio was chosen to keep the tube length to 24".

2) Bill and Tom said there were 4 BRICK designs in the works (meaning
on Tom's computer, not at the optical shop yet) 3 (brick type I,II,III - their nomenclature) used a "new" (they're term, i won't speculate) airspaced triplet
design with glasses already conjectured here. *All 3* used
spherical curves, according to bill & tom. the 92mm was a type II.

3) the type IV is also a triplet but had 2 aspheric surfaces. that's the design that ought
to out-perform everything ever made ever by anyone ever anywhere,
evah. (my hyperbole grin ) this is also the most difficult to implement.

so there are 4 brick designs in the works, of which there are 10
prototypes extant of the type II, including the one at NEAT that bill wouldn't sell, lo-end tube/rings/focuser and all, for $1000 on the spot.

so brick does not equal apheric, unless it's the as-yet-unproduced type IV. bill did not give any dates whatsoever when the other "brick" scopes are coming out. the 92 from NEAF will be at BFSP, as well as possibly a 127mm (or one close to that aperture). There will be (according to Tom) other, as yet unspecified new TMB products on display there as well.

so, does that clear things up?

92 = all spherical, airspaced triplet with on-the-abbe line glass
type IV brick = not produced yet, some ashperic surfaces.
brick = airspaced triplet, first and last surface nearly plano, just a term of endearment for TMB's new designs.