Wrong focus range in Sotem 15x50 (ussr) (1 Viewer)

[rodrigator]

Hello friends, I bought a 15x50 sotem (ussr) for very little money.
He has several problems to solve but what worries me the most is that the focus range is very wide.
The near focus is above 50 meters and infinity is too much.
I have disassembled more than 50 binoculars from my collection but this is my first Russian.
I have disassembled it in its entirety and there is nothing that I can say that it is badly assembled.

The eyepiece lenses are correct and so are the objective lenses.
Somehow this binocular is asking me to lengthen its focal length to achieve better close focus.
What would be the problem?
Hopefully they can help me.
I already have thought about how to improve it but I want to know why that focus range is so bad.

 

[Binastro]

I have the 15x50.

When it arrived one barrel was bent so much it touched the other barrel.

The parcel was badly damaged.

With oil filter wrenches I managed to unscrew the bent barrel and very carefully screwed the damaged thread half back into excellent alignment.

Is there a way to screw the objectives to a different position?

I don't know if unscrewing the barrels will move the optics the right way, but if so, I suppose large washers might work as spacers.
But there might be too much sideways movement still to keep collimation.

Regards,
B.

 

[jring]

I don't know if unscrewing the barrels will move the optics the right way, but if so, I suppose large washers might work as spacers.

Hi,

it will - bringing the EP closer to the objective moves focus towards infinity - and beyond... so moving them apart will give better near focus.

Joachim

 

[rodrigator]

Thank you friends for your answers.
It is correct that if we separate the barrels with supplements we will gain in close focus.
I want to avoid that to keep the original aesthetic. What I'm going to do is cut the inner tube of the focus wheel so that the stop on its axis (the auger that moves the eyepieces) allows the eyepieces to stick out more.
What is the close focus of your 15x50?
Is it normal that these Russian binoculars have that factory fault?
Infinity focus is very wasteful and close focus is very far😒

 

[Binastro]

All the higher magnification USSR binoculars seem to have long close focus.

That is the 15x50, 16x50, 20x60 and 26x70.

If the observer is far sighted then the close focus is even longer.

This also seems to apply to their spotting scopes, some of which use relay lenses.

I suspect the reason for no close focus is that the binoculars are military or astronomy based.

Regards,
B.