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New to astrobinoculars--need advise w/ problem.

Started by tomdisco, 09/20/2003 07:32PM
Posted 09/20/2003 07:32PM Opening Post
Although I am well equipped regarding telescopes the only binoculars I own are a pair of 35-year old Belmont 10 x 50's made in Japan. I tried them out for the first time on the sky last night and was extremely dissapointed with the results. When looking at a single source target such as Mars it revealed two images side by side. Twisting the binoculars closer together reduced this effect somewhat but no matter what I did I could not eliminate the double image. This problem has probably always existed during daytime use but was masked by the overall sceinc view as apposed to a tiny single point target.

Is this a problem with a cheap pair of binoculars, astigmatism in my eyes, or possibly both? I wear driving glasses for astigmatism but don't need them with my telescopes (with one eye closed) so I did not use them with the binoculars. In fact, until I began writing this thread, my glasses never even occurred to me.

I would like to purchase something in the 12-to-20x by 60-to-80mm range for new binoculars but don't want to spend several hundred dollars if I'm just going to experience the same problem.

What's happening here?
Posted 09/20/2003 10:17PM #1
With astigmatism, you may need your glasses with binoculars. Two exit pupils of 5mm is a lot different than one of 3mm or 2mm or 1mm.

I'd try that first and see if it helps, but you might have an out of allinment collimation problem there. On an old pair of binoculars, it is not likely there are any accesible adjustments for you to tinker with.

edz
Posted 09/22/2003 03:50PM #2
James,

Double star image in binoculars sounds more like a problem with collimation of you old Belmont to me. Especially if you don't have to wear glasses to correct for astigmatism when using your telescope. One way to verify this is to cap one objective of your binocular and see if the double image goes away. If you see a single image with either eye but double with both then collimation is the problem.

Our eyes are definetly more senstive to out of collimation condtions with a single point light source at night. I purchased a pair of Burgess 20X80 LW binos six month ago. They arrived perfectly collimated. They still work fine for me in daytime viewing but I can tell they are just a hair out of collimation when viewing stars. Our eys can merge images easier in daytime terrestrial viewing.

Erik D
Posted 09/23/2003 07:01PM #3
Also remember that your eyes can get "lazy" in the dark trying looking at a point source. I tried some binoculars that were supposedly spot on. Worked great (even in the dark) until I was tired. I happen like to spend an hour or so before bed out on the deck with my 12X60s so I began to notice that if I was really tired at the end of a long day the star images would split and I'd have to concentrate to get them to merge again. I also suspect some manufactures may merge the images at less than infinity if they think the binoculars will be used mainly close-up during the day.

Folks who use Binoculars and Bino viewers on telescopes at star parties also notice big differences in how different people can "merge" the right and left images.

I suspect this may be an issue with some folks who run into "the star splits" even on well-aligned optics because their own eyes merge images a bit differently than "normal" folks. My own solution is to have binoculars I can align myself to fit their use with my own eyes. But of course your mileage may vary.

FWIW - TM

Tom Mengel
Moderator Equipment Talk

“Insanity: Trying the same thing over and over and expecting different results”.
Albert Einstein