Reading monocular and binocular numbers?

If you have an item that's say 10x50, doesn't this mean that it's 10x magnification and a 50mm diameter aperture? But looking at various ads for monoculars and binoculars on places like eBay and Amazon, I'm finding many times, the numbers in the specs when you look at all the details aren't matching up to the product's description.

For instance, with one 40x60 monocular listing, it shows the aperture as 40mm. So wouldn't this mean it's actually a 40x40 monocular? In a listing for a similar item, the details say the objective lens is 50mm with a magnification of 40. So wouldn't this be a 40x50 monocular not a 40x60?

And with a 60x60 binocular, it says the magnification is 60 with an aperture of 40. So wouldn't this mean it's really a 60x40 binocular? There's another one that says it's 30x60.  So it appears that many, if not most of the listings I'm finding just don't seem to match up.Is this how they scam people? 

5 Answers

  • 2 months ago

    msoexpert, you are exactly correct. I have even complained to Amazon about that very thing.

    Don't even think of buying any item if its description is wacky. The description is likely not the only problem.

    When Amazon shopping (I do lots of it), pay close attention to 2 things: 1) what the reviews say, and 2) how many reviews each item for sale has. If one item has 12 reviews, and another similarly-described item has over 4000 reviews, I recommend the 4000 review item. If, for some reason, the 12 review items looks really good to you, go for it.

  • 2 months ago

    The standard calls for the 'magnification power X the aperture' in MM.

    You see something like 6-40X57, that is an adjustable power from 6X to 40X with a 57 MM primary aperture.

    There are reasonable limits to this ratio, Back in my scope building days, I made a tiny 15MM Newtonian scope with 200x power. (200X15)

    The problem was the image was so dark, there was no detail. (lack of light gathering ability). the focal distance works the resolution, so with 70 MM focus, not very good resolution. It worked otherwise.

    Yea, you see adds for zoom telescope/monocular boasting high magnification,,SORRY, they don't zoom unless fixed to a camera with zoom function, dirt cheap glass for optics so they suffer 'coma' and internal reflections.

    Actually not worth the $12 cost, but they do work, about 12 power and the focus is touchy, so yea, you got your numbers right, save for misprints or bloated specs to sell a product.

  • 2 months ago

    The numbers on binoculars and telescopes, monoculars, mean different things. On binoculars 10 x 35 or 10 x 50 means the binoculars magnify things 10 times. The second number is the diameter of the objective lenses in millimeters.

    Telescopes are a lot more varied because there are many different types of telescopes that may use only lenses or a lenses and mirrors

    The focal length of the telescope is different from the diameter of the objective lens or mirror. The f/ rato is the focal length of the telescope divided by the diameter of the objective lens or mirror using the SAME units. Neither of these is the magnification of the telescope. Magnification depends entirely on the focal length of the eyepiece in millimeters.

    This explains telescope numbers al lot more clearly:

  • 2 months ago

    You are correct.  Common practice is to give the magnification followed by the aperture of the objective.  I reckon that most of the people writing the advertising blurb haven't the faintest idea what anything means, and are just concerned with making whatever it is sound far better that it really is.  As far as the accuracy of most advertising goes, it could be called a scam, even if unintentional.  As ever, Buyer Beware ! - and always will be.

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  • 2 months ago

    "Looking at various ads... on eBay and Amazon... details aren't matching up..."

    So far, no surprise there. This is just an observation that could be confirmed by many of us.

    eBay and Amazon do not verify the claims of sellers. At best, they verify that what is posted matches whatever the seller wrote (and even that is uncertain).

    A binocular with an aperture of 40mm and a magnification of 60x would be useless if it really existed.

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