Re: [PSUBS-MAILIST] my optronic mast idea with sketch

[Jon Wallace <jonw@psubs.org>]

An optical periscope is nothing more than a refracting telescope, 
although military models have ranging and hash-marks for direction 
indication embedded within the optical train.  As Jens has suggested, a 
good optical periscope/telescope requires excellent optics and accuracy 
in construction.  You'll need to match the focal length of the primary 
lens to the length of the tube you want or you won't be able to focus 
the image.  You'll need a compound primary lens to counter chromatic 
aberration, and hi quality lenses throughout the optical train to 
counter spherical aberration.  You'd be surprised of how soon you tire 
of viewing multicolored and distorted images terrestrial objects.  Good 
refractor type lenses are expensive which is why the vast majority of 
telescopes in the world, both research and amateur, are reflectors 
(mirror primary).

Unless you really want to build such a periscope for the sake of the 
challenge or "just because" (perfectly valid reasons in my opinion), it 
doesn't make financial or practical sense given the proliferation of 
very good quality, and cheap, digital cameras that can easily be housed 
in home-built water proof containers.  A $300 eight inch screen NETbook 
with a few web cams attached to it is the way to go here.  You can even 
record the entire dive directly on the netbook.

But again, for someone who just wants to meet the challenge of building 
an optical periscope, internet research on building refracting 
telescopes will provide you all the information you need.

Jon


Jens Laland wrote:
> Brian
>
> An optical periscope is actually a rather complicated and accurately built
> instrument, see the US Navy WWII Submarine Periscope Manual, at
>
>   




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