CN FORUMS ARCHIVE Telescope Reviews: Collimation disaster?

Hello Nachtmerrie:

If the image is not round, the field stop moved laterally —which is hard to do in inexpensive binos because they are on the ends of the eyepieces—or a prism has moved massively on the prism shelf.

To answer your early question: You didn’t make a horrible mistake. However, please understand that regardless of what those who do not routinely repair binos say, it is just as common to buy a binocular of that aperture that is out of collimation right out of the box as it is to get a good one. In the 80 & 100mm models it is MORE common. And while I would be crucified again for saying:

“Only the highest quality (and most expensive) binoculars will produce an image that is free of flaring. The term "tack sharp" and the phrase "tack sharp from edge to edge" is thrown around quite a bit in various circles, but it is truly a rare thing reserved for owners of Takahashi, Kowa, Fujinon, and Zeiss binoculars, and even these have a sweet spot, outside of which the image degrades,”

it’s nonetheless true.

In addition, the flat-spring systems used in most of these binos to not have the travel or the strength to do a good job of acquiring or maintaining collimation.

The photo below is of the inside of a West Marine “SeaSearch 750” / Fujinon AR / Swift Seahawk / Bushnell Navigator / . . .

The three large Phillips screws are holding three beefy coil springs that have the strength to do the job right for years. In addition, the metal back plate need not be removed unless a prism has come loose from the cluster.

The screws that hold these springs may be—and should be—tightened to provide solid tension when all the turning is done.

The small Phillips screws go through the shelf and bottom out on ledges on the other side. When they are turned, they force the shelf up on that side and play against the tension from the corresponding spring. I have still not received my first 7x50 Kunming bino, but hope it employees this system.

Just a thought or two.

Cheers,

Bill

PS While Sarah is very, very smart, I would ask that, before you start turning screws in the future, you try to determine WHICH telescope is out of alignment. IF only one side is out, and you address it alone, you will net a collimated binocular out of your conditional alignment efforts.

You may do this by first checking for “lean.” Look for a roof top or fence top and, alternating your eyes, see if one roof is tilted with reference to the other. If one side seems to be parallel to the horizon and the other is tilted, that is the offending side—at least the most offending. If lean is bad, the prism slipped its position, which means you will have to go inside, clean out all the gray glue shards that have broken free, and reattach the prism(s) to the shelf at a 90 degree angle.

If lean is not present, give a sigh of relief and look backwards through each telescope. Line up the first two concentric circles you see and note how close the remaining stop edges are to concentricity. If one side seems off a great deal, that is where you start.

Warning, there are some folk who claim to be able to tell if a bino is accurately collimated by looking backwards through them. They should stop drinking. These rings could look great with the bino still being massively out of collimation. Remember, any anomaly in alignment is going to be exacerbated proportionally to the magnification of the instrument.

Attachment

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William J. Cook, Chief Opticalman, USNR-Ret.
Ophthalmic Tech, Naval Station, Everett, WA
Optical Mechanic, Puget Sound Naval Shipyard
Founder, Amateur Telescope Making Journal
21-year Mgr., Optics Dept., Captain's Nautical Supplies
Optics Mechanic, Ft. Lewis, WA.
Contributing Editor for Numerous Magazines

It's better to be a "has been" than a "never was." But only barely; the pay is about the same!

Edited by BillC (08/03/06 11:47 PM)