One big difference between porro and roof prisms. Roof prism systems must include a phase correction coating.
So inexpensive porros will always give a better image compared with inexpensive roof prism systems that
don't have phase correction.
Yes, those little pieces of rubber 'o' ring material are what gives the friction.
I have about 30 different sizes in my workshop as the smallest difference in diameter.
will mean the eyecups are too loose or jam. If you can accurately measure one of
the existing pieces , I will see if I have...
Your binocular was made in 1979 and was a close copy of the C Zeiss Jena Jenoptem 8x30. Many parts are interchangeable especially the prisms.
The covers were sealed with a heavy black wax and the gaps around the eyepieces were fitted with greased green felt so they are virtually
water proof and...
Maybe you don't realise that the front lenses are in eccentric rings.
Having got the prisms roughly in place, you can unscrew the covers around the lenses; release the lock ring
and rotate the eccentric ring and or the mount that contains the object glass.
It's not quite that straight forward...
Definitely 7x50. The eyepieces were fixed focus but could be altered by a technician if required. However as the young fit men
who used these, had 20/20 vision, they are rarely changed form the factory set up.
The repair was carried out over 4 days as I kept having to wait for my turn with the...
with patience and practice it is possible to get perfect alignment without a collimator.
I am however pleasantly surprised when I adjust a binocular using a distant object
and find the alignment is absolutely correct when checked on a collimator.
It's only taken about 57 years.
As you are not so very far away, do you fancy bringing your binocular to my workshop and using one of my collimators?
I'm on the outskirts of Hythe, Southampton. I'm around this coming week then off for a break.
You can see me and my portable collimator on The Repair Shop on Tuesday at 4.30...
The thread pitch of Whitworth and UNC is the same up to but not including 1/2 inch.
Whitworth threads have a 55 degree angle and rounded crests.
UNC have 60 degree flattened crests.
That might explain why some mismatched bolts wobble or unscrew more easily in use.
It's interesting what you say about Tax and duty. I have not experienced the new rules yet but in the past, items from "abroad" were allowed in free of duty and tax as long as the parcel was marked "For repair and return." I'll have to see if I can get a ruling from the authorities.
I refurbished one of these models on The Repair Shop a little while ago.
The optics look to be coated but the main haze etc is likely to be on the uncoated slopes
of the prisms and should be able to be removed with causing damage.
The prisms are held in place / adjusted by tiny grub screws and...
Can I offer a word of caution about keeping a binocular in a bag on the handlebars. The bag would need to offer quite a bit of
soft protection against vibration. Optical instruments do not like being jarred. I should know as it is how I have made a living
for many years - resetting prisms and...