Telescope Reviews: What can be Seen in Various Sizes Binoculars

This post collects a summary of the views of a selection of items through various sizes of binoculars from 10x50 all the way up to 22x100s, 25x100s and a BT100 binocular telescope with changable eyepieces from 24x100 to 62x100. It is not intended as a post on the differences in quality between binoculars. It's intended to give an indication of the differences in the VIEWS between various sizes.
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More Comparisons
Observations and Comparisons with 8 Binoculars from 8x56 to 44x100

Here's the record of a handheld observing session with nikon SE 10x42s
Binocular Serendipity

Here's a report from a viewing session with Oberwerk 25x100s
A cool August night with Oberwerk 25x100s

Views of globular cluster M26 Scutum and Planetary neb M57 Lyra
Several small binocular handheld observations and several mid-larger binoculars on the same objects

Deep Sky Observing with 70 , 80 and 100mm Binocs
Galaxy Hunting with Oberwerk 25x100

What can be seen with 16x70s?--a report
Some of these objects are a struggle for a 20x80 or a 25x100. But in this observing session under dark skies you can read what can be seen in ~mag 6 skies.

The lowly 15x70 Skymaster under really dark skies
A very nice observing report using a binocular we often refer to as lower on the scale. But you will see from this report, they are very capable.

How many stars should I be able to make out in the Trapezium through 11x56 binoculars?
For the answer to this question, see the discussion here
The Trapezium in Binoculars

and this exceptional observing report using 8x42 binocular
Finally a few steps up the Bortle scale.
the advantage of a very dark site cannot be overstated

What Binoculars for Viewing Planets?
Here are some good summaries of various sizes of binoculars and magnification that will allow you to observe some of the phenomenon that we look to the planets for. Disks, rings, moons, phases, shadow transits.

Surface Brightness (Sb)
Observing faint extended objects such as galaxies is complicated by the fact that books generally list the visual magnitude, but a better indicator of whether or not the object might be seen is Surface Brightness (Sb). Read this brief explanation.

Visual magnitude of an extended object would be the magnitude if you could compress all the light of the object to a size of 1 arcminute area. Surface Brightness of an object gives an indication of how spread out the light is and how faint it will really appear.

For an object like M101 that has a visual magnitude of mag 7.7, but an area of diameter 26 arcminutes, that light is spread out over 530 square arcminutes. Hence is has a very low Sb = 14.7. That is averaged. As you get out towards the extremities, it is fainter, in towards the center it is generally brighter. So for instance a galaxy with a bright core might be visible, but it would appear much smaller than its full size because you can see the core but not the extension.

M101 has some brightening towards the core, so the core area actually has a little brighter Sb than 14.7, while the extremities have a fainter Sb than 14.7. Another example is M33 in Tri at Sb 14.0 was easy, this one also has a broad brighter core, so in these cases we generally see just the brighter core area.

Take the example of a DSO listed as visual mag 7. If the object is 10'x10' then it has an area of 100 sq arcmin. The light would be spread over an area 100x greater than the compressed area used to determine the visual magnitude measurement. It would actually appear 100x fainter than the visual magnitude. A light difference of 100x is 5 magnitudes so the Surface brightness of this object would be Sb = 7+5 = Sb mag 12.0.

edz

These records above of what can be seen in various sizes is all well and good, but let's not lose sight of the simplicity of binocular viewing. Here's a post from a thread titled What's Your Use for binoculars?

Few people claim to be able to hand hold 15x70s. Although I rate a pair of Oberwerk 15x70s or my Fujinon 16x70s near the equal of a low power telescope, I am not among those that can hand hold such a size and I use these sizes mounted. So I will relate to you how I grew to enjoy binocular astronomy with my handheld Orion 10x50s.

Many a night I would gaze upon clusters such as the Pleaides and the Hyades. I learned intimately the positions of the stars that make up these wide asterisms. I would spend evenings lying about searching out all the globulars I could find. In a night M3, M92, M13, M5, M10, M12. On another night M4, M22, and all the populated open clusters of Sagitarius. The M24 star cloud, then afterwards M16, M17 and M18 all at once.

I found M33 in my 10x50s for the first time after looking for months using a scope. I learned then that exit pupil sometimes provides for the best view, not power.

Countless open clusters, some in areas of the sky that take on a whole new perspective when viewed at wide low-power views, like the Monoceros area, the Cygnus/Vulpecula area and Sagitarius.

Along the way, I learned star patterns much better than I ever had just using a scope. Afterwards, I could starhop navigate some areas by sight alone.

Double stars do not escape my binoculars, although at 10x the views are just the wider ones about 20" or more. But dozens upon dozens of doubles, not just the Alcor/Mizar or alpha Capricorn wide doubles.

Nebula seem to jump out in binoculars, more-so than in a scope. M27, M16, M17, M42 in the smaller binocs, but even more in larger binocs.

Of course the Milky Way, especially thru Cygnus and Perseus, in binoculars is a sight to behold, especially the densely populated rift thru Cygnus.

And back to open clusters, those in the Milky Way fields thru Auriga and Gemini, M38, M36, M37 and M35 are outstanding even in 10x binoculars. Or the fields thru the Cassiopeia / Perseus border, where near delta Cas you can see four clusters at once near M103 then just nudge little by little your way thru the area of Stock 2 and the Double Cluster, a beautiful contrasting pair.

Galaxies do not escape the 10x binoculars. I've viewed M81/M82 as a pair and even spotted M51 with 10x50s. Numerous others make it a tour thru Ursa Major, Canes Venatici and Coma Berenices. You can't pass by here without stopping to view Mel 20, Berenices Hair.

All along the way you get to see the patterns of the constellations as if you were traveling the map of the constellations in a chart book. You will pick up so much more than you ever could with a scope, you will gain a new appreciation for the patterns in the sky.

And all that with 10x50s.

So, what I use my binoculars for is to view the sky in a more intimate way, with a lot less work than any scope. Maybe the key is to just let your eyes learn how to see on a different scale.

edz

Edited by EdZ (03/18/07 03:06 PM)

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