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Archives of an email list on the history of binoculars. - page 78 / 150





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  The same magazine has an article on making disks. One could make collimator targets from it, sanding polycarbonate diffusers or targets, or combo target-diffusers as modernized versions of the Hanna in ATM II or III material.  Illuminators can now be low temperature LED arrays.  Radio Shack is selling 5 x20 Golf Scopes for $5.  Use for  error measurement, diopter setting , alignment, etc.  The reticle is not ideal, but can be used .

--Gordon Rayner


Subject: Miyauchi; booklet

From: Fan Tao <fantao@___t>

  The Miyauchi 7x50W sounds very promising.  Huge 5 element Erfle type oculars with a possibly aspherical surface, 22mm eye relief, Porro II prisms.  And the price tag of around $700 seems reasonable to me if it is close in performance to the B&L 7x50WF.  I would have preferred 8X magnification but other than that I like the specifications.

PDF data sheet at http://www5.ocn.ne.jp/~opt-m/

  Peter Hunt is selling a self-published booklet on eBay, "Collecting Old Binoculars".  It has 23 pages, around 50 photos of varying quality and as the title implies, shows older (mostly pre WWII) field glasses and binoculars.  This booklet is geared towards novices so an advanced collector may not find much information in it.  Still, any publication on binocular collecting is welcome since so few exist.  The booklet is published in England and the text is in English.  I obtained it for about US$12 shipping included and the author seems willing to ship it to other countries.  His eBay ID is briseham.

Fan Tao


Subject: Exit -Pupil Question

From: Kennyj2@___m

I would greatly appreciate any input from any "binocular group" member with regard to the following questions .

Are there any possible reasons why a middle -aged binocular user with an "average presumed "  eye -pupil dilation diameter of 3mm  in "average to bright " daylight conditions might see what he perceives to be a "superior" image when looking through a 7 x 42 binocular than the image he sees when looking at the same scene from the same distance in the same conditions  through the same binocular when that binocular has it's objective lenses "masked down" to 25mm ( and thus still providing an exit -pupil greater than the eye entrance pupil ) ?

Also , probably related , possibly not --- is there ANY DIFFERENCE at all  with regard to potential resolution , brightness or perceived "sharpness" of a magnified image between masking down a binocular's objectives as in the above example and masking down the exit pupil itself , or in a third possible scenario in which the human eye pupil is dilated to such an extent that it's diameter restricts "human eye entrance pupil area " regardless of the binocular configuration ?

Put another way - if the eye is dilated to only 3mm would for example a 10 x 70mm present an image EQUAL in EVERY WAY to that of a 10 x 30 binocular in the same circumstances , if :

(1) the same 70mm binocular was being masked down for the purpose of the experiment

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