Re: [ATM] Re: Amateur

[Woodchuck <djv@bedford.net>]

On Sat, 15 Jan 2005, Rory Blake wrote:

> As amateur Telescope builders, we are all "newbes" in some aspects,
> especially when we come up against something we have never seen before:
> This time, I really do need your collective help because
> I'm certainly a newbe when it comes to this one:
>
> I've come up with a multi-coated apo stack of lens that I just don't know
> what to do with.
> The aperture is 7 inches and the focal length is 3.5 inches.  That's right
> F/0.5.

How do you know the aperture and f-number?  How do you know the FL?

> The stack is mounted in an aluminum housing almost 6 inches thick.  Clear
> focus from corner to corner, wide angle, and color is perfect.  The mount is

How do you know about apochromatic color correction and resolution?

> ultra machined and must have been very, very expensive.   Heck, Schmidt
> cameras are not this fast.  What could it have been used for?

I am guessing that it is 7" by ruler across the front lens element,
but really has a clear aperture of much less.  Place lens
on piece of white paper.  Holding ruler across front of lens, what
is the diameter of white paper visible?  This is a better estimate
of clear aperture than glass diameter.

My guess is that it is a wide-angle aerial camera lens.  I find it
curious that there is no writing on this device.  I'm guessing
something like a F:8 or so Hypergon or Super Angulon, FL= 6 in,
back focus of 3.5 maybe.  This might cover a field of half-angle
45 degrees.

> More important:
>
> What is the highest and best ATM use for such a fast light bucket?

Photographic sky survey?  Some sort of photographic comet/variable
star/ satellite seeker?  I think film -- if this lens is what I am
guessing, the useful field is *large*, too large to make use of
economically with CCDs.

It'd be interesting to have a look at a picture of the device.

Dave

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