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Equipment Discussions >> Binoculars

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QS3000
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Reged: 02/21/09

Loc: Southern California
Re: Meade 12x60 Astronomical Binoculars for $20 new [Re: Mark9473]
      #5693438 - 02/21/13 07:59 PM

At first this sounds like a good idea. Without thinking too much however I'll say that both stars would have to be at the same distance from earth so that the artificial line that connects them can be perpendicular to the line that connects their "combined" center to earth. Otherwise the geometry we use would not apply. It would be very difficult to locate two such stars. But I may be wrong.

Going back to Meade's customer service... I received today the email informing me that my binos have been shipped, 9 days after they had been actually received. Go figure.

Then I checked their web site and saw that they put the O-III nebular filter (for SCTs) on sale for $35 plus S/H. I have been waiting for over 2 years for the price to drop from $70 to a lower level. Good things come to those that wait. Naturally I clicked on the link and it took me to the item that was on that part of the page last week. I put it on my cart and the price was still $70.

I called Meade and they said that they did not handle their online store at all, Shopatron did. I called Shopatron and they asked me to wait a few minutes for them to check on the errors. About 40 minutes later I was able to place an order for the filter and I hope to have it by next week. In both cases the customer service rep was an American, not foreigner. In conclusion, if you plan to deal with Meade's online store learn to have low expectations and be patient.

DrF


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Rich V.
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Loc: Lake Tahoe area, Nevada, USA
Re: Meade 12x60 Astronomical Binoculars for $20 new [Re: QS3000]
      #5693563 - 02/21/13 09:04 PM

Quote:

At first this sounds like a good idea. Without thinking too much however I'll say that both stars would have to be at the same distance from earth so that the artificial line that connects them can be perpendicular to the line that connects their "combined" center to earth. Otherwise the geometry we use would not apply. It would be very difficult to locate two such stars. But I may be wrong.



It's got nothing to do with the distance stars are from Earth.

Mark is saying that a planetarium program will show you the angular separtion between the two stars you pick that fit opposite sides of your FOV. With most programs, you just click on the two stars and that angle reads out on your display. That will be the true field of view of your binoculars in degrees.

Rich


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QS3000
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Reged: 02/21/09

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Re: Meade 12x60 Astronomical Binoculars for $20 new [Re: Rich V.]
      #5693765 - 02/21/13 11:23 PM Attachment (7 downloads)

I made a little drawing so that I can explain my thinking and perhaps someone out there can explain to me where I am wrong, if that is the case.

Take stars 1 and 2 that happen to be located at the same distance from earth, E. When I look at the sky (with or without binoculars) I see their "projection" AB on the artificial celestial sphere. Due to the huge distances we can assume AB to be a straight line even though we are dealing with a sphere. Angle "omega", the FOV, is two times the inverse tangent of ((AB/2)/ZE). This is the formula I used to calculate the FOV of the binoculars and found it to be 4.524º, by using the numbers 79m/1000m that are printed on them.

Now, take stars 3 and 4. Looking at them from earth we have no easy way to know that they are not at the same distance from us. We see their projection CD on the celestial sphere. Even though the distances AB and CD are the same, "omega" and "theta" are not and we cannot use the previous formula to calculate "theta".

So, how are we going to define the FOV in the second case? I am not asking how to calculate it but how to define it.

DrF


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Jawaid I. Abbasi
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Re: Meade 12x60 Astronomical Binoculars for $20 new [Re: QS3000]
      #5693883 - 02/22/13 01:04 AM Attachment (7 downloads)

check the drawing s below

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Rich V.
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Re: Meade 12x60 Astronomical Binoculars for $20 new [Re: Jawaid I. Abbasi]
      #5693912 - 02/22/13 01:35 AM

Thanks Jawaid.

DrF, for the sake of this discussion I think all stars are at infinity...

A planetarium program with give you the angle in degrees between two stars at infinity. Let's not make this more difficult than it has to be!

Rich


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GlennLeDrew
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Loc: Ottawa, Ontario, Canada
Re: Meade 12x60 Astronomical Binoculars for $20 new [Re: Rich V.]
      #5694009 - 02/22/13 04:21 AM

Indeed, treat all stars as being 'painted' on the inside surface of a *very* large sphere, with Earth at the center. Whether it be the Sun (the nearest star)--or even a satellite in low orbit--or a distant quasar, all celestial objects are for these purposes at optical infinity. Their distance can be thought of as identical.

And even when considering objects at differing distance, the *angular* separation between them is completely independent of their distance. after all, what we're concerned about is only the angle as defined by the vertex where the two lines of sight converge at the observer, and which would be measured directly by a protractor placed in the plane defined by the relevant three points.


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rdandrea
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Re: Meade 12x60 Astronomical Binoculars for $20 [Re: QS3000]
      #5705479 - 02/28/13 02:46 PM

I ordered a pair of these. I share others' impressions. The binos arrived marginally poorly packed--just two layers of bubble wrap in a box. They were, however, well collimated on arrival. For $20, how long they STAY collimated is anyone's guess. I find the eyepieces have a somewhat narrow AFOV--like looking through a Kellner rather than the more common Erfle- or Koenig-style eyepieces. I haven't measured true aperture yet. For me, they won't be my main binos but they fill a hole between my 7x50s and my 20x80s and I have a spare L-bracket and a spare tripod so they were worth the plunge.

But that's not why I'm posting.

The binos come without a case. Most cases, even soft cases, will cost more than the bino itself. But one day I was browsing Cabela's Bargain Cave online and spotted this:

http://www.cabelas.com/catalog/product.jsp?productId=1349091&categoryId=0...

The size "Small" looked about right according to my measurement of the binos compared with the published dimensions of the case. At ten bucks, the price was right, too. I have a Cabela's in my town so I had one shipped site-to-store. It arrived yesterday.

It fits very well. I was concerned that it would be a hair tight, but it is actually a hair loose (though not loose enough to worry about). Padding is there but minimal, like a laptop case, but I wouldn't bang around any $20 binos, case or not.

If anyone wants a reasonably-priced soft case to keep dirt and dust off of these binos, look into the Cabela's case, size Small, at the above link. Even without site-to-store, I don't think shipping would be prohibitive as the case is very light.

The Small is still in stock in the Bargain Cave as of today (Thursday, 2/28/13).

The other sizes might work for other binos too. Just measure yours.


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