T3D Re: custom lenses for viewers

[john bercovitz <bercov@xxxxxxxxxxx>]

> Give me a break on the VM, except as an example of what not to imitate.  
> I haven't seen a Star D, but it doesn't sound like a quality optic.

Well...   8-)  You're right of course.  But it's not too too bad.
It helps considerably that the fl is 50 mm and not 43 to 45.

> Ask your contact about viewing through an ocular lens of (x) dia., 5mm off
> axis.  It would be fantastic if he said you could still see [...]

I will.  I'm sure it'll be a topic of discussion when I give him the specs.  

You know...   You and Don have just made me think of something - we
need to weight these specs.  Don was saying my 2 moa res was pretty lame
and I agree - I was doing a match to the film.  But the reason I let
that slide was that I wqas thinking that would buy me something else like
low distortion, f'rinstance (which Don also says I've been loose on).
So we almost need an equation to give the relative values of these different
specs so that the guy will know where he can push a little.  Does this make 
sense?  Can we do it or is it too tough?

> Offhand, it seems to me that a loupe is a pretty close model.

You may well be right.  Don?  What's your thought on this?

> No, I'm probably wrong, but I believe most lens fabricators don't 
> routinely thrown in a cell.

Could be.  I'm not talking a focussing cell, of course.  8-)

> So the project is to take an existing viewer and fit a lens to it.
[...]
> so pick one that has good mechanical parts, is available, and has 
> mediocre optics.

That's the Star D (Brumberger) in whatever form it's now available.
One nice thing about it is that it's made of a more modern, if cheap, 
plastic so it's moderately droppable (not Bakelite).

John B


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