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Cheap 2.5x42s ordered (kinglux 2.5x42)


Joseki

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I've just ordered a pair of these 2.5x42 bins for £72:

http://www.gearbest.com/binoculars-and-telescopes/pp_325327.html?currency=GBP&gclid=CMSGk6CHo88CFYcK0wod8P0BSQ

& thought other people here might be interested in them (and make up their own mind about whether to take a chance on them :) ).

They 'look' a lot like the Vixen's though I've spent enough time on these forums to know there can be a lot of differences under the hood.  However what I could find online (American forums generally) sounds fairly positive so I thought I'd take a chance on them.  

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19 hours ago, Joseki said:

I've just ordered a pair of these 2.5x42 bins for £72:

Plus ~£14 VAT on delivery?

The comments on the cloudynights forum are very favourable. They could be a bargain, or a nightmare depending on the vendor. Any experience of  gearbest anyone?

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50 minutes ago, mattbee said:

Plus ~£14 VAT on delivery?

The comments on the cloudynights forum are very favourable. They could be a bargain, or a nightmare depending on the vendor. Any experience of  gearbest anyone?

Depends on their description on the package, the postal service and a game of chance but yes, possibly. Still much cheaper than any of the similar ones I've seen to date and always on the look out for a new toy. Will let you know how the transaction goes... I paid via Paypal and took insurance so should be covered in case of problems.

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Yes, I thought Id take a chance on it & import costs won't be too much. I've ordered from gearbest in the past and it was fine. I'll also follow up with how it goes but beung cautious I wouldn't spend more than I could afford to lose this way.  

At the moment it's been dispatched and I have a tracking number. :)

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35 minutes ago, haitch said:

Depends on their description on the package, the postal service and a game of chance but yes, possibly. Still much cheaper than any of the similar ones I've seen to date and always on the look out for a new toy. Will let you know how the transaction goes... I paid via Paypal and took insurance so should be covered in case of problems.

How much was insurance? I didn't see that as an option up front (just various shipping options, one of which was expedited and cost £7).

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28 minutes ago, mattbee said:

How much was insurance? I didn't see that as an option up front (just various shipping options, one of which was expedited and cost £7).

Insurance was only a couple of £ and there are a few free shipping options once you click through to them.

 

Definitely agree with Joseki on treating as a gamble and only spending what you could afford to lose... speculate to accumulate & all that. (Hope the missus sees it like that ?)

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On 24/09/2016 at 00:10, mattbee said:

Thanks Joseki, haitch for replies. Bins ordered - fingers crossed!

Got an email saying it's been shipped (from a UK warehouse). Tracking number, no courier details, but probably Yodel :-(.

Hope they treat it better than this guy:

 

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I'm guessing that these are "opera glasses", i.e. a pair of Galilean telescopes with a convex objective and concave eyepiece, thus giving an upright view - though the barrels do seem unusually short, which might suggest some clever optics, or an awful lot of aberration. With an exit pupil of 19mm there will be a lot of "wasted" light, somewhat negating the benefit of the relatively large objectives. Something like 3x25 is more usual for opera glasses - they were popular as cheap astronomical instruments in the 19th and early 20th centuries. Galilean telescopes have a restricted field of view, and I think the purpose of the large aperture in this case may be to widen the field of view. Maybe worth a punt but out of my price range for speculative purchase.

Edit: from a quick bit of googling I find that Vixen offer a similar 2.1x42 instrument, extensively discussed on Cloudy Nights (a 22-page thread):

http://www.cloudynights.com/topic/463676-vixen-sg-21x42-widefield-binoculars/

For those who can't stretch beyond a fiver, these 3x28s would raise a smile and you never know, might even give an acceptable view:

http://www.ebay.co.uk/itm/3x28-Fishing-Optics-Binoculars-Telescope-Glasses-Magnifier-Concert-Theater-Match/141935878876

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acey: yes I'm coming from the perspective of having read everything going on the Vixen 2.1x42s - including Steve's in depth review on his website binocular sky.  I sort of assumed everyone in the binocular section would be familiar with the Vixens since they made a bit of a stir when they came out with some very positive reviews.  I'm expecting a lot better performance than cheap opera glasses, especially since if you spend a bit more time on mr google you'll find hands on reviews by experienced people who've used them for astronomy - I don't just chuck my cash at random products on chinese web sites y'know :) 

 I'm not up on the finer points of optics but I believe the galilean optic design means the 19mm exit pupil isn't just wasted light btw though I can't remember why.  

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Definitely not just opera glasses - I've seen the Vixens in the flesh so know what these sort of things are about. The idea is that you get such a wide field that you don't really notice you are looking through something but they increase your light grasp for wide fields. 

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These small, super wide field binos have a positive focal length objective lens and a negative focal length eyepiece (pos-neg). This is a Galilean optical design and is used in opera glasses, which these super wide binos essentially are. Galilean optics have no exit pupil! (You only get an exit pupil with a positive focal length objective and a positive focal length eyepiece, pos-pos, like a regular pair of binoculars or a telescope. )

Some properties of Galilean optics:

  • The closer you can get your pupil to the eye lens, the wider the field of view.
  • when the eye is not on top of the eye lens, peripheral rays are either vignetted or miss your pupil altogether. 
  • There is neither eye relief nor an exit pupil. Although you could say that the eye relief is zero and the exit pupil is of the size of the eye lens.
  • Rays from different directions diverge immediately after leaving the eye lens.
  • The size of  the objectives determine the maximum possible vignette-free view
  • There is no field stop. The view fades to black at the edge of the field.
  • The observer's pupil is the only functioning entrance pupil or, when the eye lens is smaller than the observer's pupil, the eye lens functions as entrance pupil. (Limiting pupil might be a better term than entrance pupil.)
  • Ideally, the light beam leaving the eye lens should be 7mm wide. Then, at night, all the light transmitted by the optics can enter the observer's eye and, during the day, the user's pupil can block any excess light by contracting a bit.
  • For any direction in the field of view only part of the objective is used. Which part depends on the direction of the incoming rays.
  • The effective aperture is a function of the entrance pupil (the user's pupil or the eye lens) and the magnification.
  • no erecting prisms are needed. The image is upright by itself.
  • There is light gain because the beam that leaves the eye lens is a compacted version of the beam that entered the objective. If the eye lens is bigger than your pupil, some light is lost, but you can move your head back a little from the eye lens without narrowing the field of view or causing vignetting. 

In this diagram you can see how wide view opera glasses work (Galilean pos-neg optics)

Opera glass.gif

And this diagram is for an ordinary positive-positive design, which has the rays converging into an exit pupil and would need image erecting prisms for convenient use as binoculars.

ep6a.gif pos-pos optics

 

Low magnification, wide field binoculars are wonderful little instruments! You gain about two magnitudes of light and will get a very rich viewing experience from them. They'll be you super eyes!

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I've been checking Yodel for delivery notification - nothing but then it was supposed to be 7-10 working days.  However I was pleasantly surprised when they turned up this morning.

  First impressions are good, they're solid metal items.  Focusing is individual focusing.  Only tested them on distant roof tiles and clouds (of course) so far but I haven't noticed anything to give me concern (but I'm a bins newbie relatively).  Here's some pics:

 

large.20160930_103916.jpglarge.20160930_104027.jpg

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One final update from me - I did get 10 minutes outside before the clouds rolled in ... the short version - it's all good.

Similar to what I've read about the Vixens there's a  central region of clarity with increased softness/distortion around the edges. Looking straight ahead and moving your head around works well.  Stars were nice pinpoints with no flare or internal reflections.  

I was using them in a light polluted urban location (aka the garden) but they definately helped me to see more stars and I'm hoping to get a better grip on learning the night sky with these. Hopefully I will get the chance to test them out at a properly dark site one day.

Any negatives? Only that they don't come with rubber eye cups. If the Vixens are a lot better than my Kinglux pair I think I'd prefer not to know - they definately pass the "good enough" test for me.  

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Nobody wanted to have a look through my Vixens apparently at Kelling so I had a look for you :icon_biggrin:. It was the first time that I had tried them at a dark sky site. In a nut shell, they do what it says on the tin, they enhance the view of the star fields and they are easy to hold still, pin point star images and no obvious CA. I would think that the gain over the naked eye is about 1.5 magnitude. Objects like M13, M32 and the Double Cluster are easily seen.

The downside or me is that they seem to have the reverse characteristics of "normal" small binoculars in that the 2.1 x 42 has a small apparent field of view and an enormous actual field of view instead of vice versa. It takes a while to come to terms with the difference.

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