11x80 vs 20x100
Posted 19 May 2004 - 09:46 AM
Which is better, 20x100 or 25x100?
Posted 19 May 2004 - 09:55 AM
Posted 19 May 2004 - 10:01 AM
Posted 19 May 2004 - 10:43 AM
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.
Posted 19 May 2004 - 11:08 AM
Posted 19 May 2004 - 11:28 AM
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.
Posted 19 May 2004 - 12:59 PM
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.
Posted 19 May 2004 - 01:35 PM
Posted 23 May 2004 - 03:38 PM
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.