Binoculars Double image - Collimation?

[davewaldo]

Hi Everyone!

Today is my birthday, and I was lucky to receive a pair of Andrews 15x60 binoculars. Our family now have several pairs of these binos and they really are great value for money!

However the pair I received see a long way out of alignment. The image through each EP is good however they don't point exactly at the same object, and my eyes can't merge the image.

When I line up the left eye on an object, the right eye is 25% of the FOV to the right. When both eyes are open I see double images.

There doesn't seem to be any adjustment screws for the prisms just a spring clip which holds them in place.

Does anyone have any idea of how I can fix this myself or should I be sending them back? I'd rather not pay for more postage....

Any help would be great!

Cheers,

David.

[erick]

How did you find out about the spring clip?

[davewaldo]

I know from pulling apart my father's identical pair. I removed the prism cover just under the EP and it reveals a prism held down by a sprung piece of metal and some silicone on its base. Its also the same story when you remove the lens barrel to look at the other prism.

Doesn't look particularly easy to adjust.... and I wouldn't even know where to begin or which direction to adjust.

[erick]

The spring clip makes sense. However, I would have expected these binoculars to have small adjustment set screws, two per prism, set at 90 deg to each other. Maybe you are just not seeing them from the inside. They are normally at the eye lens end of the prism. [EDIT - duh! two are at the eye lens end of the prism and two are at the objective lens end] They are likely to be under the rubber cover that is over the prism housing. Use a fine jeweller's screwdriver, or reverse side of a knife blade, to gently lift that rubber and work around the edge to see if you find the screws. [EDIT - do the front edge first, then the rear edge to find the other pair] They may have a blob of something over them to fix them in place from the factory. Once you scrape that out, it's hard to claim you never touched them!

25% different (left/right) is probably enough to fuddle your eyes/brain. If you can get that back to 10% or less, you may find your eyes can merge the images. Miscollimation of the images up/down is the real problem - a small difference here is a problem because while we can move our eyes independently left/right, most of us cannot move independently up/down.

Full collimation - where the binoculars maintain collimation as you adjust the interpupillary distance (IPD) (ie. bend the eyepieces together or apart!) - is an art left to an expert. Conditional collimation - where the binoculars are collimated at a chosen IPD can be done by us - with care. But I'm a bit worried about starting from a position where the images are level up/down, but one is displaced 25% left/right. A thought - check that the barrels are screwed in cleaning. I have seen a pair of binoculars with one barrel screwed in cross threaded, so it was pointing the wrong direction.

Let us know what you find.

I'll look up some references to collimation with some photos and post.

Eric

[VK2KR]

Hi David

I have the same problem as you with the 15x60 binoculars from Andrews and have been perusing the net to try and find info on collimation. There are some notes on a similar pair on I think "Cloudy Nights" that might be useful.

However the 15x70's that I obtained at the same time are perfect.

I guess that it is a lousy batch from the manufacturer. I have not got back to Andrews regarding the problem.

I note that the small collimation??? screw under the rubber casing has a spot of clear paint locking the screw in place, and any fiddling with it would void any warranty (if there is any).

Good luck mate.

regards

Alex

[erick]

Here you go:-

http://www.oberwerk.com/support/collimate.htm

http://www.cloudynights.com/item.php?item_id=416

Before you go adjusting anything, do look at the exit pupil and see if it is nice and round or "cat's eyes"? See the Cloudy Nights article.

Woops, I also made a mistake re the adjustment screws. Two are at the eye lens end of the prism, two (at 90 deg to the first) are at the objective lens end of the prism. See the Cloudy Nights photos. Usually, you only ever have to worry about a small tweak of one of the screws near the eye lens end. Your miscollimation sounds more gross.

You can check collimation in daylight, usually on a tripod or resting on a fence/rail/cushion. Find a distant straight left/right line (a gutter is usually a good choice). Set yourself up at 90 deg to it so it goes cleaning left to right across the view. You need to practice holding your head back until you see two separate images, them bring your head forward until they touch each other - do the straight lines in each come together, or is one above the other? You can attempt to adjust any up/down misalignment of the images using one screw (closest to eye lens). If you reach the end of travel (prism stops moving so image stops moving), you'll need to move to the same screw on the other prism. You can even do this is the dark on a bright star/planet. Practice pulling head back until two separate images, then move head forward allowing the images to come together and you'll see if the two images of the star are correct in the up/down direction. Remember, some left/right difference in images is not a problem - your eyes will adjust to that.

[erick]

ps. only adjust the screws when you are looking through the binoculars so you can see what that adjustment does.


edit - read the articles - I was a bit simplistic on the horizontal tolerance. Read convergence versus divergence

[davewaldo]

thanks guys.... I'll have to look into this further. I might start with a call to andrews.

Cheers,

[bojan]

I had the same problem with binos I bought on Sunday market couple of years back.
The method to sort the problem is very simple, I used it specifically for that purpose.

Draw a pair of circles on a piece of paper, the distance between the centres should be the same as the distance between the centres of eyepieces. This will be you template for collimation.

On a sunny day, project he Sun's images on that paper. Those images (bright circles) should fall exactly on tour drawn circles on a paper (in your case they will not, of course). watch for the shadow of the binos as this will help you to orient the template correctly in up-down direction.
The best would be if you can mount your binos on a tripod or some other fixture while doing this.

Now, the objective lenses are mounted inside two eccentric rings (one inside another), and those can be rotated individually (two notches are provided for this. Please note, those notches are accessible after you remove the top cover rings from objective by un-screwing it).
By adjusting those eccentric rings, you can center each lens such that previously mentioned Sun's images are aligned with drawing.
If you can not do it by means of adjusting objectives (or if your binos do not have those rings), then it is time to fiddle with prisms.
Your binos will be correctly colimated when the Sun's images centres are aligned with the template.

Most likely your binos were knocked.
Sometimes very slight hit will move the prisms out of alignment.
Very often this alignment was not done properly at the factory....

[fwhong]

Great tip bojan.

I'm sure someone will find that extremely useful. :thumbsup:

[Ian Robinson]

Take them back and ask for a replacement pair.

Or failing that , ask them to fix them.

I usually collimate my binos myself , I wait for night time and use one of the usually dammed Na vapour street lights about 1.5 km away on the Pacific Hw as my target when tweaking the collimate (when the double images are gone , I then star test).

[davewaldo]

Thanks everyone for your assistance.

In the end I sent them back for a replacement. They were just too far out for me to consider tweaking them myself.

I have now received a new pair and they work perfectly!

Its a shame some vendors insist customers pay the return shipping costs, but in this case they still work out to be a cheap pair of binoculars. :)

Dave.

[RobF]

Hope these are find their way to Cambroon...! ;) :D

[Davekyn]

I think I will be getting my next pair from AOE again.
Good to know about these things.

Cheers
Dave

[Om_Audio]

I joined the forum just to thank you- no other info on collimation actually gets into the specifics of which screws do what. I got a pair of Zhumell 20X80 that were way out. I got them used but in new cond and was pretty sure I made a $90 mistake until doing some research online. In the end I was ready to start turning screws but really wanted to know what prisms would actually move and in what direction. Anyway- I fixed them in the morning and then by that night out in the Mojave Desert was discovering for myself Jupiter and it's moons and more. Thanks. C

[erick]

Happy we could be of service, Clifford. Tell us about the Mojave - sounds like a great place to observe from! :)

[brian nordstrom]

:thumbsup:Bang on Eric , I used bout of these to collimate the beautiful 25x100 Zhumell Tachyon bino's I got off Georgio :D here in the clasifieds , it cost me $12 for a set of jewlers screw drivers at Bunnings and no more than 30 seconds to get a perfect image , that was 2 months ago and they have not moved since then .
I have since then collimated my 8x56 binos , and they too, were the left side screws moved the image in towards the centre or out and the right screws moved the image up and down . Easy as .
;)
Dont be afraid , David as its easy if you follow the instructions .
Brian.