Telescope Reviews: Easy to collimate Skymaster 15x70s ?

Well, Oberwerk has provided the bare minimum of instruction on conditional alignment, but really has not explained completely what is going on when you start turning prisms screws. Frankly, people who think they are collimating binoculars when they start messing with prism screws are just a bit less than completely informed. While I wouldn't say do not use the instructions on Oberwerk's website (they are better than some I've seen), I would add, those instructions describe conditional alignment AND they leave some information out of the discussion and it is easily possible that anyone referring to those instuctions could end up in far worse condition than when they started.

The most common error made by individuals attempting their own adjustment is turning the wrong screw (there are 4 screws, Oberwerk doesn't even mention that, nor do most other articles on "collimation", even another article that has been published here on Cloudy Nights for 5 years now). The end result, as Kenny pointed out, can be a conditionally aligned image, but at the expense of having moved the wrong one of four prisms, resulting in a severely tilted prism, which gives the cat's eye image. I've seen binoculars that have been user "collimated" by adjusting the wrong prisms, and while the user did indeed merge the misaligned images, the user also effectively cut off about 30%-40% of all the light entering thru one barrel.

The common end-user does not have any of the equipment required to do a real collimation procedure on any type of binocular. That is an age-old argument we've had here many times and it is fully documented with several years of explanation. However, people still mistakenly use the term, most often because they do not understand the difference between true collimation and conditional alignment, nor do they care to take the time to learn. The industry doesn't help matters much by constantly referring to the process by using the wrong term.

If you want to understand collimation and the equipment used to collimate binoculars, I would suggest you pick up a copy of "Basic Optics and Optical Instruments", Carson, Fred A., Dover Publishing 1997, 1989; a book prepared by the Naval Education and Training Program Development Center.

Please refer to this article for a more in-depth discussion of "conditional alignment", which is the process the end-user has available to correct any mis-alignment between the objectives.
“Collimating” Binoculars

edz

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