Collimating Help?

[kor84]

Hello, I don't really have much experience with bins so I may be wrong about the collimation, but I've read that if one side is in focus and the other side completely out of focus, then the star should be centered on the ring for them to be in collimation, is that right? If so, then that is my problem. That brings me to my second problem, I've recently been given some Pentax PCF V 7x50 bins, but I can't find anything on how to even find the collimating screws, not to mention actually collimating them ( however I suppose doing the collimating would be similar for most bins).

Any help would be appreciated, thanks in advanced.

[NGC 1502]

Hi Kelvin. Not sure what you mean by 'the star should be centered on the ring'.

If one side is in focus but the other is not, did you use the diopter setting on one of the eyepiece barrels ?

Lots of bins have the collimation screws hidden inside the prism housing. Some of the larger bins like the popular 15 x 70s do have collimation screws under the rubber covering.

You can check collimation by putting a star at the edge of the field of view and see if it's in the same place in both barrels. Vertical collimation can be checked by putting the star at the top or bottom of the field, horizontal by putting the star at one side. Our eyes can tolerate a tiny bit of horizontal miscollimation but not vertical. You can check this during the day on a chimney pot or similar, but make sure it's a distant object to avoid parallax error from the two barrels.

I have used a repair firm called Optrep at Selsey, but unless the bins are in the £100s, it can be cheaper to replace them.

Edit - it's easy to take bins apart, but getting all the bits back in and collimated is a different story, now how do you reckon I found that out

Hope that helps a bit, Ed.

[kor84]

Thanks Ed, I focused the left side and did use the diopter setting to put out of focus the right side, then checked if those left and right sides matched up, which they didn't. They aren't a mile off and after a while I seem to adjust to them, which I wouldn't have thought would do my eyes any good.

I've now checked using the chimney pots, they do seem to be out.

I can't find a way to get into them, there are no screws visible and the rubber wont pull back anywhere.

[NGC 1502]

Hi again Kelvin. If the collimation seems to be off, then that's why you can't seem to get a good view, even by using the diopter setting.

I'm guessing that fixing them would mean dismantling, as most of these type of bins don't have exterior collimating screws. Doing this successfully is a lot harder than collimating a scope, because there are more optical parts to align, and two barrels to align to each other. The other factor is that both barrels are hinged to allow use by people with different spaced eyes, so it can be possible to collimate for one position of the hinge, but not for others, that's called "conditional alignment" (only useful for people with the exact same distance between their eyes).

I'm not saying that a DIY fix is impossible, just that it's difficult. I'm sure there's much more to learn with a search on the 'net.

The firm I used in 2007 was this one http://opticalrepairs.com/ and I was very happy with what they did, the bins are still fine after an internal clean and collimation. But it's not just the cost of repair, but getting them there and back. I used a large box with loads of polystyrene and bubble wrap.

If you want to reply to this, I'll be off line until this evening.

Hope this is at least of some help, Ed.

Edit - I see you are at Southampton, so if it were me, I'd not post to Selsey, I'd deliver and collect, saves sweating on them being bounced in the post.........

[BinocularSky]

Hello, I don't really have much experience with bins so I may be wrong about the collimation, but I've read that if one side is in focus and the other side completely out of focus, then the star should be centered on the ring for them to be in collimation, is that right?

Yes, that is "perfect" collimation. However, your eyes can easily accommodate a degree of horizontal miscollimation, especially if it is causing your eyes to converge slightly. I know that some builders of binoscopes have found that deliberately introducing a tiny amount of convergence can make the experience more comfortable: essentially, if you perceive the image as being 5 feet away, instead of at infinity, then your eyes will naturally converge. I understand that some convergence is built into birding binoculars for this reason (I would appreciate confirmation or correction of this) . What we cannot tolerate is vertical misalignment (aka "step", aka "dipvergence"). Essentially, as long as a binocular is collimated within accepted tolerances which are (within the field of view) 45 arcmin for convergence (of eyes), 20 arcmin for divergence, and 15 arcmin for step, there should not be any discomfort.

That brings me to my second problem, I've recently been given some Pentax PCF V 7x50 bins, but I can't find anything on how to even find the collimating screws, not to mention actually collimating them ( however I suppose doing the collimating would be similar for most bins).

I think (i.e. I'm not 100% sure) that with that binocular the prism adjustment screws are under the cover plates (i.e. the prisms are in cages) and fine collimation adjustment is done via eccentric rings on the objectives. I note that you are in Southampton: give Richard Biggs of Action Optics a call; he should be able to advise you and he is only in Hythe if he wants to do a physical inspection.

[Astrobits]

I have come across three ways that the bino makers use to set the collimation.

1. as Steve mentions there could be eccentric cell rings around the objectives

2. adjusting screws that are usually under the body covering of the barrels and just push the prisms sideways

3. adjusting screws that can be accessed by removing the end plates near the eyepieces and adjust the platform that the prisms are mounted on

If you can unscrew the front cover around the objectives you will see if there are two slotted rings. One is the lock ring and the other is the eccentric carrier. If not then there are some hidden screws somewhere. Finding those can be almost impossible. I have some binos that have a black textured grips and the screw holes in that cover were filled with black wax. Took me many hours to find them.

Nigel

[kor84]

Thanks.

They do look to have those eccentric rings around the objectives, but I can't get the covers off. I think I'll give action optics and optical repairs a call for a price.