Eyecup packing (1 Viewer)

I read now and then about "O" rings being used to hold the eyecups in an extended position.

I have had binoculars with eyecups that move back down fairly easily, so had to find some way of packing them in the extended position. Lately, I had a binocular that I had to lock the eyecups in a mid-way position.
Strips of velcro, the sort used as cable ties (plenty on the bay), cut to the right width and length is a good way to do this...and is easy to remove and replace as necessary.
The fine hook variety works and looks better than the more coarse velcro shown on my binocular.

Dave

What a good idea, thanks

Oh, I should say not the packs of velcro like actual cable ties but the velcro off the roll by the foot/meter. Good stuff to have around for other things too.

Cluster

You mention O-rings but not bicycle inner tubes.

Bicycle inner tubes are another good resource for
'adapting' binoculars.

Some non-cyclists attracted by the header of your most
useful post may find a little 'cycle' information
helpful.

My former bicycle shop would automatically throw away
the inner tube after a puncture repair. Part of the
reason for not handing the tube back to the customer was
no doubt the danger of legal liability. But the inner
tubes were often easily repairable, and the sale of new
inner tubes is good business for bicycle shops.

I used therefore to explain that I wanted the inner tube
to cut off sections to adapt a binocular, and carefully
beg particularly only for CUT inner tubes.

[Sometimes a shop deliberately cuts old inner tubes
before putting them in the gash bin in order to
frustrate 'skip pickers'; but not always ... .]

My memory is that for adapting a binocular eyecup, the
inner tube for 26 x 1.9 mountain bike tyres spans a
useful diameter when stretched a little to fit.

For adapting the barrel of an extendable eyecup, an
inner tube for a lesser section tyre may afford the
necessary span.

[This is a work in progress for me too. I've got the
adjustable eyecups to stay extended for a reasonable
time, but need to do the job properly. I may yet adopt
your method!]

The section of a 26 x 1.9 mountain bike tyre is given by
the second figure, namely 1.9 inches.

The section of a 700 x 32 road bike tyre is given the
same way, except that it is expressed in millimetres, ie
32mm (1.26 inches).

Without looking, I think it is common practice to mark
the inner tube itself, and not just the box it is sold
in, with the dimensions of the tyre that it is intended
for.

Inner tubes also vary as to the thickness of their
rubber. For my mountain bike, the inner tubes feature
much thicker rubber than the inner tubes of my road bike
(Good doubled back for making eyecups extend out more).

The inner surface of inner tubes is dusted with a chalk
like powder. It make obvious good sense to wipe it off
thoroughly before fitting a section of tube to an
optical instrument like binoculars.

I have never had to learn how the dimensions of inner
tubes themselves, as apart from the tyres they are
instended to fit, are expressed.

As for the dimension of tyres, a useful reference is;

http://www.ctc.org.uk/cyclists-library/components/wheels-tyres/tyre-sizes

But in practice I don't use the reference; rather I
maintain a selection of cut inner tubes, and select one
by eye to cut from that I think will do the job.


Stephen

Packing eyecups in up position

Cluster

1. Packing eyecups in up position

Further to my message, I have just had to 'pack' the
eyecups of a Celestron Nature 8x30 (truly 6.9x27?!) in the
up position.

The external diameter of the eyecups is 40mm spreading
outward a millimetre or two at the base. The external
diameter of the barrel of the eyepiece is 31mm.

I left approximately 5mm of the eyecup uncovered to
allow the rainguard to seat.

I used Kenda bicycle inner tube marked as suitable for
tyres sized: 27.5x2.10/2.35 (650B).

The key part of the tyre size is the section: 2.10 to
2.35 inches. Tyres of this section are typically
mountain bike tyres.

I attach a photo.

The eyecups are held firmly in the fully extended
position -- Before they would hardly stay up for 30
seconds. Also they no longer rattle -- Before they
seemed to have at least one millimetre of free play.


2. Extending eyecups

While I am writing I should mention another use for
bicycle inner tube: Extending the eyecup.

I have an Opticron 8x32 SR.GA.

I found that my eyelashes would dirty the outer surface
of the ocular lens. It would happen so quickly that I
would frequently find myself having to clean the ocular
lens: Not good!

So I used bicycle inner tube to extend the eyecups a few
millimetres, and since I did so, I have had clean the
ocular lens far less often.

I attach a photo.

I have used this fix on other binoculars to cut down the
amount of distracting bright light that can enter the
eye from the side.

Also it may help to reduce 'competition' from the image
that is viewed by the 'open' eye when using a porro
monocular with short fixed eyecup.

Warning: I have only removed the bicycle inner tube from
the rubber eyecups of the Opticron once in four or so
years. The Opticron rubber eyecup was undamaged, but I
don't have longer experience of the fix.


Stephen

The photos explain it well. My SRGA also get too close to my eyelashes. Sometimes it's a problem. If I keep them, I will try the inner-tube mod. I did try to extend the eye-cups using velcro, but the hook part just plucked my eye-brows.

Dave