Free pair of 7x50 bins. Good deal or what?

[michael.h.f.wilkinson]

I was looking for a pair of 50mm bins to donate some lenses for a project, and a local store kindly let me have a "broken" pair for free. They are a circa 1980 pair of "CombiFoto" (local chain of photo stores) 7x50s, made in Japan, 7.1 deg true FOV. I briefly checked them out, and found tere were only two things wrong: The diopter adjustment ring was loose (tightening three screws sorted that out), and the collimation was off. I noted a few little bumps in the covering of the prism housing at exactly the locations I would expect the prism adjustment screws. Lifting a section, of the cover confirmed my suspicion. A few tweaks later they were in very decent working order. Robert (my youngest, 8) immediately fell in love with them, and as Frank (my eldest, just turned 10) has already claimed the old (repaired) Omegon 15x70s, I was happy to let Robert have them. I might still give the optics a quick clean, but the only way to get a better deal is to get paid to take them away

Still need a defunct pair now, however, though I might have a look at non-achromatic lenses, as the project only involves H-alpha light.

BTW, how Frank (who is quite strong for his age) claims that the image through the 15x70 is stable enough for him without needing a tripod, I do not know. I have very steady hands, and even find them the limit of what I can hold comfortably.

[Mike73]

Thats great Michael!

Must be nice to observe with your sons aswell.

[Chris]

Great find, and its cool that your kids also like Bino's:) whats your H-Alpha project about? you've got my curiosity going:)

[michael.h.f.wilkinson]

I am thinking of placing a small etalon (<50mm) between two lenses (one collimating lens and one imaging lens). This can be achieved by a negative collimating lens, effectively turning the front half of the optical system into Galilean scope of very low magnification, and a positive imaging lens. You can also achieve this by using a positve collimating lens, in which case the front end acts as a low magnification astronomical scope. If the focal lengths of the imaging and collimating lenses are the same, the net focal length of the scope is unaltered. This set-up is longer, but it is easier to find matching pair of coated lenses.

[Chris]

Sounds like an intersting scope, I had to Google etalon, not sure I fully understood it, am I right in thinking this scope will basically have an adjustable filter system built in, and you say imaging lens, is it going to be an imaging scope?

[michael.h.f.wilkinson]

The imaging lens refocuses the parallel beams into an image. This image can be projected onto a CCD or viewed with an eyepiece.

[Chris]

I see, thanks:)

[michael.h.f.wilkinson]

I just spotted a pair of Yashica 7x50s on astrobuysell.uk, and they seem identical except for the brand name. I know Yashica built for others, so maybe also for CombiFoto. I still want to give them a clean with some Baader wonder fluid, but the images are nice and crisp even now.

[Stargazing_Cliff]

Good them 7 x 50 just watched video about binoculars can see DSO's with them

http://youtu.be/PN4KFT-QLck

will have to get pair 7 x 50 sometime.