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Archives of an email list on the history of binoculars. - page 46 / 150





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Subject: Collimation Revisited

From: "William Cook" <billcook50@___l.com>

Arthur Wrote:

>>>Twice this week, I examined two porro prism binoculars which were cross-eyed:  the left tube had a field of view more to the right than than did the right tube; the right tube field's was more to the left than  was the left tube's field..  One failed a quick check for collimation, while the other seemed to be in collimation.<<<

  Any time the field in a left telescope is to the right of a corresponding right telescope, the FOV of the right telescope will automatically be to the left of the telescope—and vice versa.

  One thing rarely discussed on the list involves the lowly axle. This should not be. Binoculars not collimated to the AXLE are not collimated.

  Quite often an amateur will screw up a collimated TELESCOPE to collimate BINOCULAR as a whole. This would make the project MUCH harder for a professional—though a real professional wouldn’t make the mistake—and is maddening for the amateur.

Step 1: Collimate the swinging barrel to the AXLE using the “tail of the arc” method.

Step 2: Collimate stationary barrel to the Swinging Barrel. By doing so, it too will be collimated to the AXLE.

  By this, the binocular is COLLIMATED. And being collimated, it is collimated at all IPDs. Many years ago, I coined the term “Conditional Alignment” to cover the alignment situation that exits when the binocular is within standards at only one IPD—this distance being determined by 1) a specified IPD, 2) the observers IPD or 3) the blind luck of an untrained worker.

  Whenever possible, it is important to determine WHICH telescope needs the work before charging in. I am not a fan of being bitten by poisonous snakes.

  However, given the choice, I would MUCH rather be bitten by one than by two!

>>>I guess that both were collimated by poor workers or by amateurs.<<<

  Amateurs take heart, if the big companies keep closing the parts departments and farming out their work to unskilled workers who know more about slinging burgers than aligning prisms, you will soon be America’s “experts.” This, of course, will be much like wetting your pants while wearing a bark blue suit . . . it will give you a warm feeling, but nobody will notice.

Just a thought.

William J. Cook, Chief Opticalman, USNR-Ret.

Mgr, Precision Instruments & Optics, Captain’s Nautical Supplies, Seattle

Editor, The Best of Amateur Telescope Making Journal

  PS If there is a scientific name for that which I call “Conditional Alignment,” I would like to be advised. I have no need to be original at the expense of plagiarism.


Subject: Yellow tinted glass.

From: <astro.marko@___n.net>

  My name is Mark Hammons and I am a fairly new member.  Actually only own a few pair of Zeiss Binoculars and 2 pair of Leitz Binoculars, neither of which are very old -- but I enjoy the history of optics.  Also am an amateur astronomer with a rare Zeiss scope (AS 63/840) and some rare Zeiss eyepieces ( Orthos, Huygens, Monocentrics).

  The articles about finding yellow tint in some older Binoculars caught my eye.  I wonder if the reason could possibly be the use of radioactive rare-earth elements in the glass mix.  I have an early Leica screw-mount Summicron lens ( 50mm, F2.0 ) that has a yellowish tint to it.  Some years back there was an article in the "Viewfinder", a publication of the Leica Historical Society of America talking about how some of the Summicron lenses of that  period (mid to late 1950s) had a yellow tint to them.  The article concluded that it was because Thorium Oxide was used in one or more of the glass elements.

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