To: atm{at}shore.net
From: tkrajci{at}san.osd.mil
Reply-To: tkrajci{at}san.osd.mil


>From: "N. Foldager" 
>
>I purchased an adapter that should fit a web cam to a male T-thread.
>
>However, the supposed T-end of the adapter is too big for the device
>on which I planned to use it: a tube from Tele Vue (originaly
>intended for eyepiece projection). The female "T"-thread of the
>adapter slips completely over the male thread on the Tele Vue tube
>and goes to its shoulder.
>
>The outer diameter of the Tele-Vue *male* thread is 41,54 mm.
>A "Canon-T2 ring" that I have fit to this this thread.
>
>These problems give me that suspicion that maybe a "T-thread" is not
>well defined?
>
>I would very much appreciate it if somebody on the ATM list can
>inform me, what is the exact definition of a T-thread (inner and
>outer diameter and threads per inch?).

See: http://www.astronomydaily.com/atm/thread.asp (you will have to
register at the site to gain access, but it's free)

Summary of data from above page:

 T-Mount
  Internal / External
Pitch Diameter 41.57mm ñ 0.04 / 41.44mm ñ 0.04 Pitch 0.75mm / 0.75mm
Depth         ?
Relief         ?
Major Diameter 42.02mm min / 41.93mm ñ 0.04 Minor Diameter 41.25mm ñ 0.04 /
41.17mm max Shoulder to Focal Plane 55mm

>Are there more than one definition ( T and T2 ?? ).

I am not aware of more definitions, but I'm not an expert...so there may be
other definitions.

Tom Krajci
Tashkent, Uzbekistan

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