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Stephen.S
member
Reged: 08/05/06
Posts: 22
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Hi,
I received my 25x100 binoculars from Telescope Service yesterday, they arrived in just two days from Germany. That is the positive news.
I haven't had chance to use them yet, but the news on the build and quality control is mixed. On the plus side, they do seem very substantial with thick rubber coating, and as long as the lens coating stays in tact, I expect them to last many years.
On the negative side, there were some scratches on the central bar, with the largest being about 2 inches. Also the lens caps are very loose, and easily fall off.
As discussed before on this forum, the model that I have bought, made by the Kunming Optical Instruments Company, is available from many retailers and at different prices. Again, much research has gone into this model by follow forum members, but it seem that the most important difference is that wholesalers and retailers have a choice of 4 different coating options. The company says on its own web page that option 4 costs 15 times more than option 1. Here is a link to the relevant part of the Kuming site:
http://www.binocularschina.com/coating.html
Another thing to be wary of, is the suffix numbering. According to the Kunming web site, the latest version of the model is the FB. However, mine came with the suffix of 25x100LX. I queried TS about this, and they said that they use their own numbering. There is nothing wrong with this, but it leaves the buyer not knowing if they have bought the latest model or not, as every model looks identical.
About three years ago,I bought a Chinese 10" Dobsonian, and there were build and quality control issues there too. So its sad to learn that the Chinese still have problems of this nature three years later.
Finally, I would like to ask forum members how do I test the image for sharpness and collimation etc? At the moment, I don't intend to send them back, but I would do if the image was poor.
Best wishes
Stephen
Edited by Stephen.S (06/28/08 06:45 AM)
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GlennLeDrew
sage
Reged: 06/18/08
Posts: 310
Loc: Ottawa, Ontario, Canada
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One test of sharpness is the splitting of doubles. My 25X100 Celestron fairly easily splits xi Cep (6"), in the middle of the "house" shape of Cepheus. I can't recall other such tests off hand. Saturn's rings should be resolvable, with gaps between them and the planet (unless the tilt is small).
As for collimation, if they feel comfortable during extended viewing, and your eyes don't seem to be out of whack immediately after you look away, they're probably OK. To get a better idea, you could do this...
Mount the bino on a tripod, aim it at a distant street light, at least 1/4 mile away, and focus the light's images on a piece of white card. Just like solar viewing. Actually, if you feel comfortable doing this (I've done it, with no problems), use the sun itself.
On the card, mark a horizontal line, with two tick marks on the line as far apart as your eye spacing (or whatever IPD you have set when doing the test). Ideally, a very distant object should project its two images exactly on the tick marks. Of course, the card must be oriented such that the horizontal line is aligned with the eyepieces.
This test becomes more sensitive as the card is moved back farther from the eyepieces. Ideally, the only kind of mis-alignment you should see is when the images project a little wider than the tick mark spacing (this means that your eyes only have to make a very easy "cross-eyed" realignment). Too much vertical displacement means that your eyes have to work like a chamaeleon's!
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Home-made 11X50 right angle bino, 8.1 deg. FOV
Modified 26X100 bino, 3.5 deg. FOV
Mediocre minds discuss people. Good minds discuss events. Great minds discuss ideas.
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