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11x80 vs 20x100

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#1 Guest_**DONOTDELETE**_*

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Posted 19 May 2004 - 09:46 AM

What would be the difference in what I can see with my celestron 11x80s (which I love) and a pair of apogee 20x100s?

Which is better, 20x100 or 25x100?


Thanks!!!

#2 BluewaterObserva

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Posted 19 May 2004 - 09:55 AM

Oh yes... I use 11x80's for my hand held duties, and 25x100's for my mounted duties these days. Man, what a difference a little mag and little more aperture make!!!!!

#3 Craig Simmons

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Posted 19 May 2004 - 10:01 AM

Better contrast with the 25x100 over the 20x100. Exit pupil of 4mm and 5mm vs. 7.27 on the 11x80s.

#4 AJTony

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Posted 19 May 2004 - 10:43 AM

As an owner of a pair of Apogee 25 X 100 binos, I can only say that they are the most enjoyable optics I own for all uses, especialy deep sky objects. I know they are not comparable to high end optics such as Miyauchi's, but they give the biggest "bang for the buck". I bought them for $299, and now I see Apogee is selling them for $249. I use them with out difficulty mounted on an Orion Paragon HD tripod. Of course, the use of a standard tripod mount does limit viewing anywhere near the zenith, but I plan my viewing by month and time of night to compensate for this. I hope you go for the 25 X 100's.

Note: When my wallet says OK, I am considering the purchase of the Burgess 20X-40X 100 binos ($1000). Reason: Power increase, a $250 tripod included, and best of all 45 degree eyepieces.

AJ

#5 Guest_**DONOTDELETE**_*

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Posted 19 May 2004 - 11:08 AM

This sounds great. If I can convince my wife, I think I will order a pair.

#6 Guest_**DONOTDELETE**_*

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Posted 19 May 2004 - 11:28 AM

11x80 vs. 20x100?

Based on EdZ's data (if I did the calculations correctly), you would have a 0.75 and 0.14 limiting magnitude gain from the increased magnification and aperature respectively. That's almost a total 1 magnitude increase.

Just based on the specs, I would say the 25x100 is mostly "better" for the reasons Craig mentioned.

#7 EdZ

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Posted 19 May 2004 - 12:59 PM

I would agree with that gain for the most part.

It is probable you would get far more gain from the aperture than you might think, for this reason. It is extremely unlikely that you are currently getting the full benefit of the 80mm aperture as you would need to have 7.25mm eye pupils to get it all. Very few people fall into that category.

Unless you can tell us what your dark adapted pupils actually measure, let's just assume for statrers you have eyes that can dialate to 6mm. If that's the case, then your 11x80s are delivering light to your eyes as if they were 11x66. If your eyes can only dialate to 5mm then thay act like 11x55. In either case, you will get a much greater gain from the apereture when you jump to a 100mm aperture with a 4mm or 5mm exit pupil, maybe as much as another 0.25 magnitude.

Under any circumstances, the magnification is going to provide much greater gains in magnitude.

A 5mm exit pupil in the 20x100 will provide for brighter views of nebula and galaxies. Sky background will be just a little brighter and field of view should be just a little wider.

A 4mm exit pupil in the 25x100s will be less bright but gives greater magnification, makes images larger, and probably has a narrower field of view. It will give a darker sky background, which helps some objects stand out better, but it may not necessarily provide better contrast.

Contrast will be determined by the quality of the glass, baffles, coatings, lack of reflected ghost images internally, fineness of focus point and a lack of chromatic abberations. The higher quality binocular will provide better contrast.

edz

#8 Guest_**DONOTDELETE**_*

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Posted 19 May 2004 - 01:35 PM

Ah, good point EdZ. I forget about the exit pupil - eye dilation relationship with regards to an effective aperture size.

#9 Guest_**DONOTDELETE**_*

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Posted 23 May 2004 - 03:38 PM

AJTony:
Just read your post about purchasing the Burgess Optical 20-40x100 Astros. I've been using mine for a couple of weeks now and am very pleased with them. (See my post on my "review" of them). Bill included a heavy duty padded metal case; magnesium tripod with extra mounting plate and soft case. I never expected the tripod case to be included.
You'll be pleased when you receive them. Have a good day
and clear skies.

George
NY


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