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Steve Napier
Carpal Tunnel
Reged: 05/10/04
Posts: 1559
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Hi,
Im confused by what Ive read about Image scale.
For example 20x60/20x80 Binoculars,obviously both have the same magnification and the image in the 80s will be brighter but is this the only difference? Ive heard it said on these boards about seeing a larger Image scale even though the magnification of the two Binoculars are the same.
Can someone please clarify this up for me?
Thankyou
Steve.
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lighttrap
Reged: 02/06/04
Posts: 3833
Loc: cloudy, foggy, humid NC, US
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Magnification determines image scale.
Aperture determines brightness.
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18" Starsplitter II f/4.5
8" Hardin Dob f/6
C5 workhorse mini SCT f/10 or f/6.3
70mm TV Ranger dual purpose birding/astro
77mm Leica Televid APO
16x70 Fujinons on UA Deluxe Mt.
12x50 Nikon SE
8x30 Nikon E2s
and many others
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wilash
Fairy Godmother
Reged: 09/30/03
Posts: 5746
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Steve, the magnification of any pair of binoculars is an approximation. So two different binoculars with the same specified magnification may give slightly different size images.
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Steve Napier
Carpal Tunnel
Reged: 05/10/04
Posts: 1559
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Perhaps I have worded it wrong.
I appreciate your replies but,like I said Ive read that Image scale is improved in the larger apertures even though the magnification is the same.
Steve.
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Scott Beith
SRF
Reged: 11/26/03
Posts: 33042
Loc: Gulfport, MS
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Steve,
All I can think of is if you are viewing diffuse objects - nebulae, galaxies, etc....
The larger aperture would give an appearance of larger image scale due to the fact that the object's edges are more clearly observed. You can see more of the Orion's Nebula with larger apertures. This would make the nebula appear larger. It didn't grow - the aperture increase allows you to see the fainter sections at the edges that were not visible in the smaller binos. On point sourses like stars, or a large bright object like the Moon - 20x = 20x in any bino's or scope.
The other thing you might notice is if the FOV in a set of binos is smaller, the object seems larger due to the fact that the object fills more of the visible area.
Hope this helps.
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  Scott
"The only thing necessary for the triumph of evil is for good men to do nothing." -- Edmund Burke.
"People sleep peaceably in their beds at night only because rough men stand ready to do violence on their behalf." -- George Orwell
"The measure of a man’s greatness is not determined by what he accomplishes for himself, but by what he accomplishes for others.” -- Some Bald Guy
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BarrySimon615
scholastic sledgehammer
Reged: 03/01/04
Posts: 918
Loc: New Orleans, LA
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My interpretation of image scale is that a larger image scale is simply put larger images with greater spacing between stars. Magnification gives you a larger image scale and a larger image scale becomes more impressive compared to a smaller image scale if the higher powered eyepiece used to give you a larger image scale has a correspondingly larger field stop diameter allowing it to have a larger apparent field and perhaps an equivalent true field. A good example of what I am trying to say can be illustrated by using both a 24 mm Panoptic eyepiece and a 32 mm plossl eyepiece in the same optical system and comparing the differences. If used in a 500 mm f.l. system the 24 Panoptic will yield about 21x and a 3.25 degree true field (68 degrees apparent). My 32 Televue plossl will yield 15.6x and a similar 3.25 degree true field but with only a 52 degree apparent field. The 24 Panoptic has no larger of a true field but the obvious magnification difference gives you more of a "being there" feeling. The images are simply "scaled up".
I dramatically saw the effect of image scale when I was comparing the same eyepieces years ago in a Brandon 94 Apo with a 640 mm focal length and a Televue Genesis with 500 mm focal length. Both had great performance but the larger image scale of the Orion Nebula seen thru the Brandon was, too me, much more impressive than the smaller scaled image seen thru the Televue Genesis.
Barry Simon
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