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ZEISS DTI thermal imaging cameras. For more discoveries at night, and during the day.

Tethered objective covers for the Yosemite (1 Viewer)

Kevin Purcell

Well-known member
I'm curious is anyone has added tethered objective covers on their Yosemite.

Given the markings on the plastic covers provided (an embossed "44") and actually measuring the covers with my cheapo ruler they're 44mm ID.

So that seems like the "Eagle Optics Tethered Binocular Lens Cover Set (Small)" should work.

http://www.eagleoptics.com/index.asp?pid=3185

Anyone used these? What sort of plastic are they made from (the Vortex soft rubbery stuff or the harder plastic?).

The 44mm is a bit larger than I expected given the stated 30mm aperture. In fact the aperture diameter is (again eyeballing the cheap ruler) is greater than 30mm, perhaps about 32mm.

Henry Link has said there is an internal aperture stop that results in a smaller effective aperture (of 28mm). I've not measure the exit pupil of my Yosemites yet (but I have an accurate way to do it, I think).

One can see an aperture stop immediately behind the objective which I suspect sets the aperture to the specified 30mm though there may be other stops in the system.
 
I got the "Eagle Optics Tethered Binocular Lens Cover Set (Small)".

They fit though that fit is a bit looser than I could have liked. In normal use they stay put if put on firmly (say bin shaking or even rubbing up against a jacket or sweater) but they won't stay put when removing them from the case. That's good enough for me thought. Most of the time when they're around my neck the covers are off but it's nice to have the option of keeping the objective covered without fiddling with the original covers.

BTW, I now tend to store them in the case "sideways" (i.e. a barrel down rather than objectives down). Makes it easier to pull out of the case and as they're almost square they fit rather well. I use the same scheme when they're in a Pajaro belt case and that works well too.
 
I have those on my Yosemites as well. However mine are too big where the band goes around the barrel. That is always coming off if I'm not real careful. However, your solution in putting them in the case objective end up might just be the thing. The caps on mine fit nicely enough over the objectives.
 
Yes, the rubber tethers are very loose and because the Yosemite doesn't have rubber armoring just that roughened ABS (?) shell surface they don't "stick" in place. But I haven't had the tethers come off.

I have an equivalent set (bigger!) on my Eagle Optics Raptors (the Audubon 820 like enclosure) with very grippy rubber coat. Those tethers don't move when placed and the end caps don't fall off either.
 
Don't mess with the tethered lens caps. Buy a pair of Butler Creek flip up objective covers (#21 standard or #6 blizzard style). They're much faster and much more secure, and they go right on the Yosemite.
 
Fireform,

Thanks for the size reference. I was in a Sporting Goods Store the other day and looked at those and thought they were just ehat the doctor ordered. I was not sure what size I needed. By the time I next had the Yosemite in hand, I forgot to measure.
 
I measured my Yosemites and they are 1.75" diameter of the objective barrels. Mine have the #6 blizzard caps on them, although I prefer the regular type when I can find them. The packaging for the Butler Creek caps can be opened and closed without harming anything, so most sporting goods stores would let you bring in your bins and fit them in the store. I like to do that when I can, just to be sure. I use them on all my bins and almost never need to clean my objectives.
 
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If you take a look on the Yosemite objective caps (and most caps in fact) they have a number on them which is the ID in mm usually (even down to the half mm in some cases) so you don't have to make the measurement (except to verify it's not an odd part number ;) )

IIRC it's 44m for the Yosemite - that's where I got the number from.
 
I got the #21 objective covers. I would have gotten the #19 Eyepiece cover because it has the spring loaded lever "snap open" feature, but the store only had one. The Yosemite measures 43mm on the outside measurement.
 
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