TheSkySearchers

3/27/20

Most of smaller binoculars used for astronomy deliver large exit pupil (5-7mm). In telescopes however such large exit pupils result in washed out views and bright background sky, at least from locations I typically observe. In telescopes I prefer 3-4mm exit pupil for low power wide views and was wondering if that would be the case for binoculars to.

B&H Photo was having March sale and I picked Nikon Action EX 16x50 for a good price. Last Friday I did a side by side shootout between them and my trusty Orion Worldview 10x50.
Fit and finishes look similar, although Nikon priced about double of Orion. Hopefully, it translates in better glass/coatings. In any case both are good quality mid-range binoculars. Both are waterproof, with rubber armor and long eye relief. Comfortable to use with eyeglasses, and lightweight (~2 lb) for free hand use. Orion has 6 degree and Nikon 3.5 degree FOV.

On the night of testing Ursa Major was in the right position for binocular observing. First immediate impression is darker skies in 16x50 and wider views in 10x50. While narrower, 3.5 degree of Nikon was not limiting, and overall aesthetically I preferred the views of 16x50 better.

M101 – Pinwheel gal - views were very similar, averted vision round spot.
M108 – gal – not resolved in 10x50, maybe (faintest AV spot) with 16x50.
M81 and M82 – Bode’s and Cigar gal – resolved in both binos; better details, shapes resolved in 16x50.
M109 – gal – not resolved in 10x50, small spec with AV in 16x50.
M97 – Owl Nebula – not resolved in 10x50, fuzzy star in 16x50.

C/2019 Y4 (ATLAS) – comet – faint round spot with AV in 16x50. Maybe in 10x50, but only because I found it in 16x50 first.

Overall, the exit pupil results seems to be consistent between telescopes and binoculars, and for my observing location 16x50 deliver better results than 10x50 on small to mid-size faint targets. Still, on large open clusters and nebulae, wider FOV of 10x50 could be advantageous. So, I am not throwing away 10x50 yet.

Nice shootout Bigz!

Sounds like they both have their purpose.

I have only looked through my Bushness 10x50’s. My son in law brought his Celestron 20x50’s on our last camping trip. I really had a hard time with them. Way too dark compared to my 10x50’s. I really didn’t like them. Is this typical of hi mag smaller objective bino’s?

Thanks Jim! 20x50 with 2.5mm exit pupil might be pushing it too far. Sounds more like daytime binos.

You should try them from your home location. Brighter skies favor small exit pupils and dark - large.

My 25x100's seriously outperform my 15x70's and 10x50's - though my 10x50's are my goto binoculars for each evening. 25x100 requires that I set up the mount and attach the binos. Looking at the zenith is a bit difficult because you have to crane your neck, would be much better with some right-angle prisms like the binocular scopes have.

The exit pupil is smaller in the 25x's versus the 15x70. I never really thought about the sky lightening effect but now that you mention it Andrey I realize it's kind of a problem with the faint stuff.

Thanks for the great review/comparison.

Thanks Michael! 100mm binos collect twice more light than 70mm, and 70mm twice more than 50mm. This definitely helps with fainter targets, but on top of that larger binos tend to have smaller exit pupils (4mm in 20x80 and 25x100), to improve the contrast.

I have come to the same conclusion. My previous instrument was a C8 equipped with William Optics binoviewers. I would often choose my trusty pair of Edmond RKE 28mm ep’s for low power scanning of clusters. In the scope/binoviewer combination they produced 131x with 1.6mm exit pupils offering beautiful contrast. I sold off the C8 and replaced it with a 100mm binotelescope. The focal length of this instrument is f5.5. I plugged in the 28mm RKE’s and found that the views are washed out. It is producing 20x and a 5.1mm exit pupil. I have a pair of Oberwerk 22mm ep’s that are producing 26x and a 3.9 exit pupil. The background sky is much darker. The reduction in exit pupil was 1.2mm and it made a huge difference in view quality. I use the 22’s for extended objects but my favorite ep’s with the Binotelescope are 14mm with 2.5mm exit pupil. Clusters that fit in the field of view look better than in the 22’s.

aae0130 wrote: ↑Tue Mar 31, 2020 10:16 pm I have come to the same conclusion. My previous instrument was a C8 equipped with William Optics binoviewers. I would often choose my trusty pair of Edmond RKE 28mm ep’s for low power scanning of clusters. In the scope/binoviewer combination they produced 131x with 1.6mm exit pupils offering beautiful contrast. I sold off the C8 and replaced it with a 100mm binotelescope. The focal length of this instrument is f5.5. I plugged in the 28mm RKE’s and found that the views are washed out. It is producing 20x and a 5.1mm exit pupil. I have a pair of Oberwerk 22mm ep’s that are producing 26x and a 3.9 exit pupil. The background sky is much darker. The reduction in exit pupil was 1.2mm and it made a huge difference in view quality. I use the 22’s for extended objects but my favorite ep’s with the Binotelescope are 14mm with 2.5mm exit pupil. Clusters that fit in the field of view look better than in the 22’s.

I am considering Oberwerk BT-100XL-SD instead of fixed 25x100 binos. How do you like it so far?

Bigzmey wrote: ↑Tue Mar 31, 2020 11:09 pm

aae0130 wrote: ↑Tue Mar 31, 2020 10:16 pm I have come to the same conclusion. My previous instrument was a C8 equipped with William Optics binoviewers. I would often choose my trusty pair of Edmond RKE 28mm ep’s for low power scanning of clusters. In the scope/binoviewer combination they produced 131x with 1.6mm exit pupils offering beautiful contrast. I sold off the C8 and replaced it with a 100mm binotelescope. The focal length of this instrument is f5.5. I plugged in the 28mm RKE’s and found that the views are washed out. It is producing 20x and a 5.1mm exit pupil. I have a pair of Oberwerk 22mm ep’s that are producing 26x and a 3.9 exit pupil. The background sky is much darker. The reduction in exit pupil was 1.2mm and it made a huge difference in view quality. I use the 22’s for extended objects but my favorite ep’s with the Binotelescope are 14mm with 2.5mm exit pupil. Clusters that fit in the field of view look better than in the 22’s.

I am considering Oberwerk BT-100XL-SD instead of fixed 25x100 binos. How do you like it so far?

I have only had them for about a month but it’s definitely a quality instrument. No false color issues on the moon or bright objects like Venus. Considering it would be my only instrument I thought it would be worth the extra bucks to eliminate false color. Stars are nice all the way to the field edges. Being able to use different eyepieces gives it a leg up to the traditional 25x100’s with lunar and planetary.

After binoviewing with a C8 for many years it is a nice change. I went from 1/2 degree fields to 3 degrees.

Hello Andrey,

a very nice shoot out!
You will definitely love your 16x50 Nikon, I am also increasingly using my 15x60 Docters.

Thanks, and clear skies,
JG

Thanks for the comparison. I underline the conclusions, based on my experiences with a 10X50 and a 15X70, and a 20X80.
My eyepupil becomes 5 mm in the dark, so I have a rough match with the bino's exitpupils. As the 20X80 ( 2,5 kg) observations are better of with a tripod in my case, I use the 15X70 more often than the 20X80. So it is comfort against going a tad deeper in my case. The role of the 10X50 is beyond any doubt .

Thank JG and John! After experience with 16x50 I am considering now 20x70 to supplement 15x70.

Thanks for your report, Bigz! I completely agree with you about your preference of exit pupil size! Too bad I seem have shaky hands, which prevented me so far from investing larger-magnification binos. It seems that I can't make good use of anything beyond my 8x42 extra-lightweight roof-prism binos for night sky viewing without a tripod! And with a tripod, objects at high altitude become a pain in the neck (literally). So, I decided to wait with further bino acquisitions until I can spend $$$ a bino with 90 deg angled view and exchangeable eyepieces (without going into war with the spousal unit).
Until then, I will be just drooling on reports such as yours

stewe wrote: ↑Wed Apr 01, 2020 7:42 pm Thanks for your report, Bigz! I completely agree with you about your preference of exit pupil size! Too bad I seem have shaky hands, which prevented me so far from investing larger-magnification binos. It seems that I can't make good use of anything beyond my 8x42 extra-lightweight roof-prism binos for night sky viewing without a tripod! And with a tripod, objects at high altitude become a pain in the neck (literally). So, I decided to wait with further bino acquisitions until I can spend $$$ a bino with 90 deg angled view and exchangeable eyepieces (without going into war with the spousal unit).
Until then, I will be just drooling on reports such as yours

Thanks Steve! I can handle free hand or with monopod binos up to 70mm. Above that similar to you I have decided to save up for 100mm bino-telescope.

Thanks for the review Bigz! This is consistent with my experience, and is why I prefer (eg) 10x50 to 7x50 or 15x70 to 10x70.

The article in Sky and Telescope a number of years ago about the "visibility factor" sums it up nicely.
For those who haven't read this, all other things being equal the visibility factor is the aperture x magnification.
For your binos this is 16x50 = 800, vs 10x50 = 500

Here is the article: https://skyandtelescope.org/astronomy-e ... inoculars/

Of course there are other factors to take into account: just like with telescopes the quality of the glass and the control of CA and other aberrations makes a big difference. For example, my 22x60 Tak Astronomers (vf = 1320) give my 25x100 FB's (vf = 2500) a big fright- but because the Taks are actually 2 60mm apos stuck together they should punch above their weight! Now if only I could find some way of swapping out eyepieces in them without wrecking them...

Happy viewing and keep safe!

- Dean

Thanks Dean! Are your Taks triplets?

Bigzmey wrote: ↑Thu Apr 02, 2020 1:44 am Thanks Dean! Are your Taks triplets?

I believe they are the same as the FS60C. f5.9 Flourite doublets. No CA and sharp pretty much to the edge of the field. (Very slight drop off from around 90%.) I was very lucky to pick them up via an "ambit claim" offer to a friend...

stewe wrote: ↑Wed Apr 01, 2020 7:42 pm [...] with a tripod, objects at high altitude become a pain in the neck (literally).

Having a neck problem with somewhat limited mobility, I can relate to this. Something that's helped me is to use my tripod as a bipod - I extend two pod legs, get between them, lean back in a chair or reclining chair, and tilt the binos / tripod back above me. The third leg can be used as sort of a counterweight or something to steady with your feet / legs. It's not perfect but it's better than a handheld view. It's easier to do it than to describe it.
FWIW.

100% agree with you as I myself own 16x50 binoculars, and they work like a charm. It is important to remember, both of these binoculars have their own pros and cons. 10x50 binoculars are not very powerful, and using them for astronomy or stargazzing is not going to help anyway. However, 16x50 binos with better magnification power size offer better visuals. As long as their exit pupil is concerned, the 16x50 binos have the 3mm where as the 10x50 binos have 5mm however, I personally consider 16x50 a better option for stargazzig. Hopefully my response give you insight.
Reference: https://opticswhiz.com/10x50-vs-16x50-binoculars/

Anything more than 10x mag I cant hold steady so need some form of help , monopod, tripod, or the best a parallelogram , when using my 15x70 I have to use one but with 10x50 no , so 16x50 why ? one cant use them hand held so rather get 15x70
lots one can see even with 7x50 if the sky is dark

Richard wrote: ↑Tue Dec 12, 2023 4:13 pm so 16x50 why ? one cant use them hand held so rather get 15x70

And then why not 20x70 rather than 15x70?

It is all about matching the sky conditions to the optics. Large exit pupils for dark sky, small for light-polluted.