Pointers to Collimating Carl Zeiss Jena 10x50

[Uplooker]

Hello One and All,

I have a pair of Carl Zeiss Jena 10x50 that require a slight tweak to the collimation. Has anyone here done this before. What tips and hints would you give. I plan on using a bahtinov mask for each objective, place at 90 deg to each other to achieve collimation. What have others done?

Can you also confirm the correct screws? On first inspection there are only 1 off screws top and bottom of the main body of the bins.

Any assistance gratefully received

[BinocularSky]

I may be wrong (&, if so, would appreciate correction!), but I'm pretty sure that these are collimated with eccentric rings in the objective cells. If so, it needs peg-spanners and a heck of a lot of patience!

 

[Uplooker]

I suspect you may be correct. I have just unscrewed one of the objective end covers and it looks as per the photo below, apologies for phone quality image.

 

can you please illuminate me further on how to go about the collimation of these bins. Serial No.6806422, so I reckon made in 1988 - open to correction

 

[BinocularSky]

From a certain book :-) (but note that the best you can get doing this is conditional alignment, not full collimation)

Eccentric rings. Binoculars differ from telescopes in that collimation is achieved by lateral movement of the objectives, not by tilting them. Moving the lens one way will move the image in the eyepiece the other way. However, it is all but impossible to move an objective only either laterally or vertically, and collimation with eccentric rings can be monumentally frustrating until you get the hang of it. It can be a tough test of perseverance and patience – you have been warned!

[5-17.jpg Caption: Eccentric Rings. Rotating these rings moves the lens laterally. Note that it is marked to enable its return to the original position.]

First of all, mark the positions of the rings (see Fig 5-17) so that, if you do not manage to improve matters, you can at least set them to their original position. Next, set the rings so that there is no eccentricity, i.e. the narrowest part of the inner ring aligns with the widest part of the outer ring and vice-versa. Rotate the objective lens assembly a small increment – say about 10 to 15º – at a time until it has made one revolution and see whether there is any movement of the image and, if so, if it is sufficient to bring the images into proper alignment. If it is not, slip the inner ring about 10º and repeat the rotation of the lens assembly. Repeat this until the images are aligned as well as possible. If there is not sufficient eccentricity in the rings, you will need to adjust the prisms.

 

Note:  It is usually better to set the binoculars so that there is a discernible amount of divergence, i.e. so the optical paths from the binoculars are converging (see Chapter 2, footnote 3), and then to gradually collimate from there than it is to approach collimation from the other way. This is because the eyes are more sensitive to divergence than to convergence. You may find them more comfortable if there is slight convergence (this is also known as the eyepieces being “coned in”) because the experience is that the image we see is perceived by some people to be relatively close, at a distance at which their eyes would naturally converge.

For more detailed accounts of collimation see:

·           J.W. Seyfried's  Choosing, Using, & Repairing Binoculars, which gives a more detailed account of conditional collimation, including building bench-testing apparatus .

·                     The Naval Education and Training Program Development Centre's (NAVEDTRA) Basic Optics and Optical Instruments, which gives accounts of full collimation with bench test apparatus.

[Uplooker]

Thank you Steve. That book that you refer to looks to be very good - so good in fact that I may have ordered a copy ;-)

 

[Peter Drew]

Ian. I'll tell you what I do in this situation . I think the Zeiss type construction means that the objective barrels can be unscrewed after loosening any hidden grub screws, if so release one side so that you can rotate it. Usually, a small amount of rotation will correct the collimation. Once done, mark the new position for future reference, if the barrel is loose at this point just apply a little adhesive.

[BinocularSky]

^^^
Love it!

The value of common sense and experience.