T3D Re: Now yer in trouble

[bercov@xxxxxxxxxxx (John Bercovitz)]

>   Do we pick 36 mm FL as a compromise or
> go to 37 or 38 to make the design a bit
> easier?

I'd pick 35 if it's for 5P and 36 if it's for 5p and 7p.
Field costs money so we have to think seriously if we want 
7p.  I suspect we do.

>   How large diameter do we need to cover
> the spread :)

Depends on how much of the spread we want to cover.
I would suspect we should cover 65 +/- 5 mm IPD 
without adjustment and I suspect we should limit
the OD of the assembly to 45 mm to allow for the 
purported prodigious proboscis and beetled brow of 
some of our most famous exponenets.

>> or ~$100 each, $200/pair.  Is this too scary?

>   Kinda high for me. The dual Surplus Shack
> achromats cost from $22 a set to $32 a set
> depending on quantity.
...
>   The next step up might be the 6x Edmund
> magnifier that Eric G has. This works out
> to a FL of 41.7 mm.
...
>   Higher still, would be the Peak Aspheric
> Loupe, sold by B&H for about $139 each

If they make you happy, there's certainly no reason to go 
to a better lens (if a better lens can be designed).

>   So if we are talking $200 or more a set
> the question is what we gain over the Edmund
> and Peak loupes?

Someone should measure the magnification, distortion,
color, field coverage, and field flatness of these loupes 
to see if they really work perfectly for the application.
If they do, end of story.  If they don't, then we need
to see what a new design would cost.

So what's "work perfectly"?  Well, that's the list of specs
we need to come up with if we want to take the guy up on 
his offer.  Probably we should do the testing mentioned in 
the previous paragraph before bothering the guy, though.

John B


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