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Binocular Magnification

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#1 eyeoftexas

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Posted 09 April 2020 - 10:13 PM

Hi All,

I recently acquired a couple of binoculars (8x42 DX ED and 20x80 SkyMaster Pro) and have really enjoyed the views (when the clouds allow).  Of course, aperture fever has crept in, and I was wondering about something larger.  In particular, I've looked at 25x100 glasses, like the Oberwerk 25x100 Deluxe.  But, here's my question.  Is there actually significant difference in the views between 20x80 and 25x100?  I don't mean quality, but what can be seen.  I know the FOV will be narrower with the 25x100's, but the magnification is only ~25% greater.  Would that be enough to, say, see more DSO's or better resolve star clusters, etc?  No need to bring in the really big guns, like the Oberwerk BT-100XL, into the discussion.  I recognize that with interchanging eyepieces, you can really crank up the magnification, but such glasses are not in my budget for now.  Plus, I already have an AT115EDT that can go to significantly higher mag.  All said, I'm asking if the step from 20x80 to 25x100 is worth it?

 

Clear Skies and Safe Shelter to all.



#2 Astro-Master

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Posted 09 April 2020 - 11:10 PM

Unfortunately the answer I would normally give you is not possible at this time.  If we were not in the middle of a pandemic, I would suggest trying a pair of 25x100's yourself at a star party, or maybe a telescope and binocular store near you would let you try a pair for a night or two.

 

I guess you could contact an Oberwerk outlet that has a 30 day return policy if you're not satisfied.


Edited by Astro-Master, 09 April 2020 - 11:13 PM.


#3 Cali

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Posted 09 April 2020 - 11:13 PM

For me the answer is Yes regarding DSOs. Note that the Obie 25x100 clocks in at 10LBs. I added a p-gram mount to accommodate it. You want something solid underneath because of the narrower FOV.

 

On the other hand you may want to look into a binoviewer for your AT. It blew the 25x100s out of the water for local orbs, but that was expected.

 

- Cal


Edited by Cali, 10 April 2020 - 08:49 AM.


#4 Jetstarz99

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Posted 09 April 2020 - 11:27 PM

Brightness wise how do the 20x80 compare to the 8x42?

 

I have a cheapo set of 10x50, and I am looking to something else.

 

I have considered the Skymaster, more from the 80mm, than the 20x

 

Can't decide, so many choices.

 

Your feedback based on using them could be helpful.

 

 

For your dilemma, the 100 vs the 80 for increased brightness

would seem more important than the increased magnification.

 

For me brightness wins over magnification

 

Cheers



#5 Cali

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Posted 09 April 2020 - 11:56 PM

Brightness wise how do the 20x80 compare to the 8x42?

 

 

I have both the Obie 20x80 and 8x42. The 8x42 is a nice spotter but the 20x80 is the "sweet spot". Everything looks mighty fine, especially M45 which just fits in the 20x80 FOV.

 

- Cal  


Edited by Cali, 10 April 2020 - 12:01 AM.


#6 Garribaldi

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Posted 09 April 2020 - 11:56 PM

I have owned a pair of Celeston 20 x 80 Giants since 2001, they were a big step up from my 10 x 50s & the new views I got with them were impressive to me at the time. They needed to be mounted of course, so I bought a Bogen tripod & a fluid head for them. Years later, after I had essentially stoped using them more than a few times a year, a friend that was more into astronomy than I build a couple aluminum parallelogram mounts & gave 1 to me. It made a big difference in comfortable viewing & sparked my interest again. My friend owns the Oberwerk 100 XL Ed, & after looking through those I knew I wanted something better, but couldn’t afford the big binocular telescopes.   I decided to get 25 x 100s, but which ones were the question. Celestron  & Orion make very affordable ones, the Oberwerk 25 x100 IF are better & a bit more. The more I researched the more I wanted really good optics...so I bit the bullet so to speak and bought the APM 25x100 MS ED binoculars, & because of the greater weight I had to upgrade the mount as well, but Wow! What a difference the extra 5x & probably more importantly the 100mm objectives make.  



#7 Astro-Master

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Posted 09 April 2020 - 11:57 PM

Brightness wise how do the 20x80 compare to the 8x42?

 

I have a cheapo set of 10x50, and I am looking to something else.

 

I have considered the Skymaster, more from the 80mm, than the 20x

 

Can't decide, so many choices.

 

Your feedback based on using them could be helpful.

 

 

For your dilemma, the 100 vs the 80 for increased brightness

would seem more important than the increased magnification.

 

For me brightness wins over magnification

 

Cheers

I would not even consider the Skymaster's they have a problem with the focus drifting when held at a high angle.  Oberwerk's binoculars don't have that problem.  I guess you get what you deserve going cheap.

 

  I learned my lession years ago on a pair of Celestron 15x70mm Skymasters I bought for $99.  I've never had a problem with my Oberwerk's.


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#8 TOMDEY

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Posted 10 April 2020 - 12:23 AM

Well... it's around 56% more light. Like going from an 8-inch to a ten-inch scope. Or (come to think of it?!) Like when I sold off my pathetic little 29-inch scope and upgraded to my current 36-inch. It's a lot bigger and sure shows a lot more.    Tom


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#9 TOMDEY

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Posted 10 April 2020 - 12:51 AM

Interesting Experiment:

 

When comparing the advanages of more or less aperture (both have their place) just advance and recede from a structured scene. Think of your distance as inversely proportional to aperture. On the final leg of one of my hiking paths (NYS Forest Canadice Lake South end), the last few hundred yards is a straight shot to the gate. There's a red Stop Sign and a yellow caution sign, and a white sign with park rules on it. When I round the bend outa the woods, and first see it (~300 yd range), I can see the signs OK, but not read them. As I draw closer, their shapes, lettering and details become more and more and more resolved. My absolute field is diminishing, but the detail gets proportionally better.

 

That's the same thing as we go up in aperture, assuming good optics and good seeing. Here's a cartoon I made to give a feeling for that.

 

So, go outside and get 100 paces from something familiar... your house, whatever. Think of that as 80mm binos. Now walk 20 paces closer. That improvement is like going to the 100mm binos. You'll probably be surpirsed at how much more detail you can see, even with that rather modest improvement in affinity.   Tom

 

~click on~ >>>

Attached Thumbnails

  • 107 The Aperture Advantage Invariant Luminance 88.jpg

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#10 edwincjones

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Posted 10 April 2020 - 05:12 AM

A difference-yes       but

 

it is very  subjective  as to which instrument do you enjoy more,

binoculars  to see the forest

or

telescope to see the trees

 

edj


Edited by edwincjones, 10 April 2020 - 06:40 AM.

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#11 eyeoftexas

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Posted 10 April 2020 - 07:23 AM

I have both the Obie 20x80 and 8x42. The 8x42 is a nice spotter but the 20x80 is the "sweet spot". Everything looks mighty fine, especially M45 which just fits in the 20x80 FOV.

 

- Cal  

For me, the two provide different perspectives and show different views.  The 8x42 is excellent for viewing large areas, like seeing the star field of Auriga, for example.  I can then switch to the 20x80 and see individual objects in Auriga, like M36, M37, and M38.  Importantly, the views are complementary.

 

And that is what I was actually asking in the first place.  Not whether Oberwerks are "better" than Celestrons, but whether 25x100 provides a different/complimentary view to 20x80.

 

TOMDEY: I appreciate the thought experiment.  But, maybe I am missing something but I had thought the difference in terms of zooming in (walking towards the signs) is 20x vs. 25x, not 80 vs 100.  The 80 vs. 100 is how much light is gathered.  So, yes a 80mm and 100mm telescope gather different amounts of light, but not whether you can resolve stars in a cluster; that requires changing magnification.  And so where I come to this question is that in my AT115, changing eyepieces to go from 20x to 25x is the difference between using 40mm or 32mm eyepiece.  When I go from 40mm to 30mm (eyepieces I actually have), the view is only just ever so slightly different in terms of seeing an object.  If I were trying to find a DSO, I would not expect to do it with that small change.  It indeed really only changes the FOV (again, only slightly if AFOV is held constant).

 

The brightness factor would change, but then again by much?  20x80 and 25x100 have the same exit pupil (4 mm), and so to Garribaldi: when you said that the jump made a "wow" difference, I do not doubt it one bit, but I guess I'm asking how?  Does this mean that despite the same exit pupil, the view was brighter or did you resolve dimmer stars?  Or, is this a case of different coatings, ED glass, etc?


Edited by eyeoftexas, 10 April 2020 - 07:39 AM.

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#12 eyeoftexas

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Posted 10 April 2020 - 07:42 AM

Well... it's around 56% more light. Like going from an 8-inch to a ten-inch scope. Or (come to think of it?!) Like when I sold off my pathetic little 29-inch scope and upgraded to my current 36-inch. It's a lot bigger and sure shows a lot more.    Tom

I sure wish you would have sold that pathetic 29 inched to me wink.gif



#13 Cali

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Posted 10 April 2020 - 09:18 AM

For me, the two provide different perspectives and show different views.  The 8x42 is excellent for viewing large areas, like seeing the star field of Auriga, for example.  I can then switch to the 20x80 and see individual objects in Auriga, like M36, M37, and M38.  Importantly, the views are complementary.

 

And that is what I was actually asking in the first place.  Not whether Oberwerks are "better" than Celestrons, but whether 25x100 provides a different/complimentary view to 20x80. If you are in really dark skies and have agood mount

 

 

eyeoftexas,

 

Yes, the 8x42 is excellent for viewing large areas, hence my suggestion that they are good spotters.

 

The 20x80 is gonna get you a whole lot closer. The 25x100 will get you closer still but you're gonna lose FOV. Also, its a _big_ instrument.

 

If you are in dark skies and have a good mount, the 25x100 is definitely gonna give you a different/complimentary view. Again, you're gonna need a good mount or everything is gonna jump out of your FOV when you so much as blow a fart.

 

I don't know whether the Oberwerks are "better" than Celestrons. What I Do Know is that when scouting for new glass, I can ping Kevin (the owner) at Obie and do a one on one.

 

Try that with any other manufacturer. 

 

- Cal


Edited by Cali, 10 April 2020 - 09:42 AM.

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#14 eyeoftexas

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Posted 10 April 2020 - 09:48 AM

Yep, I have my Farpoint UBM for my 20x80, which should handle 25x100.


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#15 Jon Isaacs

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Posted 10 April 2020 - 09:52 AM

TOMDEY: I appreciate the thought experiment.  But, maybe I am missing something but I had thought the difference in terms of zooming in (walking towards the signs) is 20x vs. 25x, not 80 vs 100.  The 80 vs. 100 is how much light is gathered.  So, yes a 80mm and 100mm telescope gather different amounts of light, but not whether you can resolve stars in a cluster; that requires changing magnification.  And so where I come to this question is that in my AT115, changing eyepieces to go from 20x to 25x is the difference between using 40mm or 32mm eyepiece.  When I go from 40mm to 30mm (eyepieces I actually have), the view is only just ever so slightly different in terms of seeing an object.  If I were trying to find a DSO, I would not expect to do it with that small change.  It indeed really only changes the FOV (again, only slightly if AFOV is held constant).

 

 

I think that Tom was working with your example, constant exit pupil, magnification and aperture increase in identical proportion.

 

In terms of stars in a cluster and what one sees, stars are brighter in a larger scope so when you increase from 20x80s to 25x100s you see more stars because they're both brighter and more highly magnified.

 

In my telescopes, I see quite significant differences between a 41 mm and a 31mm in terms of what I see. Even the difference between a 35mm and a 31mm is quite visible.

 

Basically what Tom is saying is the 25x100s bring you 25% closer than the 20x80s. It's pretty much an exact model. Stars get brighter, objects get larger without increasing their intensity/surface brightness.

 

Jon


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#16 earlyriser

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Posted 10 April 2020 - 10:11 AM

I would expect the improvement in how deep you can go switching from 20X80 to 25X100 to be similar to what is seen going from 8X42 to 10X50, which in my experience is quite noticeable.  


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#17 Cali

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Posted 10 April 2020 - 10:31 AM

Yep, I have my Farpoint UBM for my 20x80, which should handle 25x100.

Yes it will. But just barely.

 

Notes from an actual user.

 

- Cal


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#18 eyeoftexas

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Posted 10 April 2020 - 10:32 AM

Great, thanks everyone for your thoughts and comments.  As soon as the budget allows, I definitely see larger binoculars in my future.  Now, let me see, which ones... grin.gif



#19 Jon Isaacs

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Posted 10 April 2020 - 10:33 AM

I would expect the improvement in how deep you can go switching from 20X80 to 25X100 to be similar to what is seen going from 8X42 to 10X50, which in my experience is quite noticeable.  

 

Noticeable but in the big picture, not earth shattering, 

 

Jon



#20 Rich V.

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Posted 10 April 2020 - 11:13 AM

For star fields and open clusters, you'll clearly notice that 25x shows more stars than 20x.  Magnifiation trumps aperture.  In my case, I clearly see more stars in the Pleiades, for example, with my 22x70s than my 16x70s despite the smaller exit pupil of the 22x binos.  I'd expect the same with the 20x80s vs 25x100s.

 

You must decide if the smaller FOV and greater bulk tradeoff is right for you.

 

Rich


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#21 TOMDEY

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Posted 10 April 2020 - 11:42 AM

The danger in all this... I already have and enjoy my 100mm binos... but know there are 120mm and 150mm out there. And seem to be foolishly talking myself into considering buying something that I --- should not afford. Ehhh... NUTS!    Tom


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#22 eyeoftexas

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Posted 10 April 2020 - 11:50 AM

Rich: Perfect, that's exactly the kind of answer I was looking for.  Of course, you just made my aperture fever go up a few degrees wink.gif



#23 Garribaldi

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Posted 10 April 2020 - 11:51 AM

I would answer yes to both brightness & to the resolving of dimmer stars.  The Trapezium in Orion for example, in the 20 x80 Celestrons, I was only able to see 3 stars to the left of the actual Trapizoid which looked to me as 1 or two stars. In the APM 25 x 100s I clearly see 4, not 6 though. Color & contrast are much better, stars are sharp pinpoints, the moon displays little or no color fringing at the edge. I believe the ED glass has much to do with this. They were not cheap though, I’ll admit. You get what you pay for.


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#24 sonny.barile

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Posted 10 April 2020 - 03:19 PM

I would answer yes to both brightness & to the resolving of dimmer stars.  The Trapezium in Orion for example, in the 20 x80 Celestrons, I was only able to see 3 stars to the left of the actual Trapizoid which looked to me as 1 or two stars. In the APM 25 x 100s I clearly see 4, not 6 though. Color & contrast are much better, stars are sharp pinpoints, the moon displays little or no color fringing at the edge. I believe the ED glass has much to do with this. They were not cheap though, I’ll admit. You get what you pay for.

 

With the 4 bright stars of the Trapezium it is more about angular separation than aperture. Seeing as a, b, c, and d are all bright.  The rest of that group require added aperture to see.



#25 edwincjones

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Posted 10 April 2020 - 04:35 PM

The danger in all this... I already have and enjoy my 100mm binos... but know there are 120mm and 150mm out there. And seem to be foolishly talking myself into considering buying something that I --- should not afford. Ehhh... NUTS!    Tom

I had a miyauchi 100mm pair, added a fujinon 25x150 and enjoyed both,

but choose to keep the 100mm and sell the very big, heavy, not very portable fuji

 

the 100mm could do almost as much as the 150 and was a lot easier to manage

 

it is not just bigger is better, but also what do you want to do with bigger

that you cannot with smaller

 

edj


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