Improvements for TENTO 20x60 bino
Posted 25 July 2004 - 02:40 PM
The optics are surprisingly clear and sharp, but the bino is hard to use out of free hand. It needs practicing, or better a tripod, to hold it stable.
The only problem I experience is the focusing mechanism. This mechanism feels week and mostly asks two fingers to rotate the focus wheel. Does anyone know if this can be improved? I have no experience whit fixing bino's. I do have an older 10x50 bino whit *bleep* prisms but whit a smoothly running focus mechanism. Should it be possible to build this over? Or do I just have to live whit this minor failure?
Posted 25 July 2004 - 03:07 PM
Mechanical mediocrity is such a common problem with Russian binoculars that I'm surprised the cold war went on for so long :-)
I'm not optimistic that much can be done about these things unfortunately.
As you've noticed though , the good news is that the optics
themselves are very good , in fact I would say INCREDIBLY good for the money changing hands for these.
No amount of practice , weightlifting or nerve gas will ever
prepare you to or anyone else to hold 20 x 60s steady enough to get the best out of them.
You need a tripod / mount of some sort.
Clear skies , Kenny.
Posted 25 July 2004 - 03:16 PM
If the 20x60 Tento is as good as the 20x60 Kronos, then it is a very capable performer, but with some good amount of chromatic aberation and a tight FOV. You bought your 20x60 Tentos for the same price that I paid for some 7x50 Tentos. I have a closet full of more expensive binoculars. Yet the 7x50 Tentos sit right here on my desk in the den for looking out across the backyard. That's a position of pretty high regard in this household. The optics in them are nothing short of amazing for the price.
Actually, if the Russians could ever learn to make bodies and mechanicals that equal the current crops of Chinese binoculars, then they'd really have something. Unfortunately, after having Tentos, Red Stars and Kronos in various configurations, it seems like the weak spots in Russian binoculars are always mechanical. However, the good news is that the optics are usually quite good. So, you put up with junky focusers, and spindly focus wheels that feel like they were lubricated with some combination of sand and bacon fat and generally clunky designs that feel like they're straight out of some bad WWII movie. But, in exchange you get really good, if sometimes sepia tint optics for what amounts to pocket change.
Anyway, what you want to do for your 20x60 Tentos is something along the lines of what I did for a guy with 20x60 Kronos. Make a mounting bracket out of a piece of plywood. 1/2" is fine. All it needs to be is about 7-8" long by about 3" wide. Drill the exact center and glue in a 1/4"x20 "speednut". This will allow you to affix the unit to a standard photo tripod, or parallelogram mount with 1/4x20 adaptor. Next, afix 2 pieces of nylon strapping to the plywood by simply stapling or screwing them to the board. Each piece should be about 6-8" long and should be fixed to the board 1/2 the distance from the centered speednut to the edges. (So if it's an 8" board, then screw each nylon strap about 2" from the center hole/speednut. On the ends of the nylon straps, either glue or sew in matching velco pieces. The whole idea is that you'll wind up with a board that can 1)screw onto a photo tripod, 2) afix the binoculars by means of velcro straps around their objective barrels. I think it probably took me about as long to type this post as it takes to make one of these universal bino adaptors. They're also available commercially.
As to trying to make something better of the *bleep* mechanics and design of any of these Russian binoculars, I really wouldn't bother. I tried taking apart a set of one of them once, and had pretty much stripped out the screws just attempting to get it all apart. (I've never seen binos put together with such self demolishing, very badly threaded flat head screws before.) I seriously doubt that you'd be able to accomplish anything by way of refinements to any of these USSR binos. They're crude, but the optics in them are really quite good. Accept them for that and try not to curse the focuser too much unless your Ukranian is good enough to fool them.
Posted 25 July 2004 - 05:53 PM
I never saw a new Tento for sale. Not even a bino company selling them.
I absolutely agree on the fact that the Tento has fantastic optics. They are unbelievable good, most certainly for the price! I really love using my Tento but always need to support it to be able to have a steady view! For me it was the first bino that showed me the 4 moons around Jupiter and the minuscule rings around Saturn.
All very tinny, but clearly present!
I will have a go for the described mounting bracket. That sure will be a great help!
Just a pity the Western techniques can't fix the Eastern shortcomings. Oh well, nobody is perfect
Oh yah, about my Russian. The Tento comes with a Russian booklet. It took me 5 minutes to read it, but I didn't understand a word of it!
Posted 26 July 2004 - 04:39 AM
In the nineties I bought in Spain quite a few Russian 7x50 for work (environmental education), probably more than thirty. I found at least three different versions, and almost all these glasses were showing mechanical problems. Anyway, with some patience and experience they can be overhauled. I must say that I found some binoculars with optical faults too, showing not uniform loss of sharpness out of the centre of view.
The Russian binoculars I see nowadays show the same mechanical faults, except for the Komz 7x30 and the Komz 10x42. All the mechanical problems are not in the design (here the biggest problems are glare and stray lights) but in the assembly.
About the 20x60: at the assembly line there is less attention in minimizing the clearance between the eyepiece bridges. This is obtained with one or more thin washers of the right thickness. If there is too much clearance, bridges will tilt a bit when focusing, causing irregular movement of the eyepieces and variations in the focus balance between right and left eyepiece. On the other hand, if there is to much friction between the bridges, i.e. no clearance at all, they will suffer a torsion when adjusting the interpupillary distance. If you examine carefully the bridges moving up and down while turning the focus knob, you should detect irregularities in their motion. Even the shortest rotation of the focusing knob must produce the SAME movement of BOTH bridges. Check it at the end of each bridge, i.e. where is the eyepiece.
To adjust the clearance, unscrew the interpupillary disc, then the screw that tightens the bridges (there could be a grub screw to loose before unscrewing it), then remove the first washer, then the right bridge with its eyepiece (be careful, you can damage or dirty the surface of the field lens), then the second washer and finally the left bridge. Unlike in many Oriental binoculars, the shaft of the central focusing system is generally well done, with acceptable clearances. Now: if you find that there is too much clearance between the bridges, build a washer with a brass sheet of the right thickness (washers used in this part of the binoculars could be from 0,03 to 0,5 mm) and put it with the washer number one (or replace it with the new one). If the friction between the bridges is too high, reduce the thickness of the washer with a sheet of sandpaper. It is a question of patience, 0,05 mm of residual clearance could be already too much.
Sometimes a rough focusing mechanism could be caused by the plastic (onetime was velvet) band at the top of each eyepiece tube, it is thought to reduce the play between bridge and eyepiece tube, but sometimes it causes irregular focusing. Check these bands if you find that the clearance between the bridges is ok.
Posted 26 July 2004 - 11:33 AM
Thanks for your post.
That was VERY informative indeed. Very interesting.
You have obviously spent considerable time playing around with Russian binoculars !
Kind regards , Kenny.
Posted 26 July 2004 - 07:58 PM
But okay, you my read it as well...
Although a little afraid of working on optics due to the fact that I hardly know something about them other than that they are very vulnerable, I think, I know, I can do something about it whit the information you gave me!
On the next cloudynight I will give it a go!