Binoculars- exit pupil versus eye relief

[DJDD]

hiya,

I am trying to decide between these binoculars:

AOE - 10x50HR
or
AOE - 9x60

The reason for the difficulty is simply trying to decide the most important factors between eye-relief and exit pupil.

My wife and I wear glasses and are mid-30's.

So, is Eye relief or exit pupil of greater importance.

For the 10x50HR's:
Exit pupil = 5 mm
Eye-relief = 23 mm
Weight = 900g

For the 9x60's:
Exit pupil = 6.7 mm
Eye-relief = 21 mm
Weight = 1.2 kg

We will take these bushwalking and will most likely be lying down or against a rock when viewing.

thanks for any comments.

cheers,
DJDD

[erick]

Seems that you are talking predominantly daytime use? Under those conditions, surely your pupils are no where near fully dilated (maybe only 2-3mm dilated at most?? Check some references?) so exit pupil is probably not an issue for this use. I'd suggest then that you go for the best eye relief and the best magnification at the smallest aperture that gives you a manageable weight to carry while walking. But if you wanted to use them to look at the night sky as well, that's a different story!

[DJDD]

thanks, eric, for the *prompt* reply.

actually, I meant primarily night time use. I would rarely use them during the day (maybe occasionally looking at a bird or distant object).

sorry for the confusion!

DJDD

[erick]

In that case we start again :D

What I read suggests young healthy eyes open to pupil size around 7mm and ancient eyes like mine might struggle to 5+mm. Let's presume that you will both be closer to the 7mm. As I understand it, any binoculars producing an exit pupil greater that 7mm will produce an image that is bigger than your eye can see. I understand that, therefore, you lose some of the light being collected and focussed by the binoculars. If you are an extremist, this probably matters. If you are not, than you probably wouldn't get too fussed. But within reason. I wouldn't get a pair of binoculars that produced a 9mm exit pupil for my use under dark skies. If I can stick to 5mm or less, and all the other factors are OK, then I'll do that.

Now, if you read some of the articles, they go to extraordinary lengths describing all the parameters and how they interact. I've seen arguments for and against which is the most important. Do your own searchs for such articles so you can make up your own mind. AOE have useful info on their site. See also the articles in this forum (at left). Go reading here:-

http://www.cloudynights.com/ubbthreads/postlist.php/Cat/0/Board/binoculars

probably in the "Best of..." thread.

However, eye relief is pretty important, it seems to me. If the eye relief isn't sufficient, then your whole viewing experience is pretty poor. Unlike if you are losing 20-30% of the image through exit pupil mismatch - then you get 70-80% of the "experience", not 0%. Other factors such as weight, magnification are resolved through good mounts etc. Obviously, the largest aperture you can get and good multicoatings throughout the binoculars are very important for faint fuzzies.

My thoughts.
Eric :)

[DJDD]

:)


that sounds very reasonable.

Google is usually my first point of call but i have found this forum is so helpful and useful that I completely forgot to use google. :)
That forum is great and the best of topic is very useful. I subscribed immediately!



From your comments and some further reading I have done in the last hour or so (what else is work time for except planning my next purchase and extra-curricular activities?) it seems eye-relief will probably be the most important factor for me. certainly, some of the skies are so bright with stars out where we walk that it would be hard to say if I would get full dilation. :D

certainly, everyone seems happy with 10x50's, as well..


cheers,
DJDD

[erick]

Where's zat? I wanta' walk your way!




Well, I bought AOE's 12x60s, and I think they are super.

[DJDD]

:D
well, most anywhere on the bogong high plains in VIC, etc. although the best place I think (with my limited experience in astronomy) would be Mt Speculation (not really the Bogong High Plains area but in the alpine region of VIC). When it is clear it is very bright out- no haziness but bright enough to walk without tripping over at all. crazy!

of course, it is a long way to walk only to find the skies cloudy. :)

I think I will buy the 10x50's as the eye relief seems quite important and I am on the older side of mid-30's so exit pupil will only deteriorate. :whistle:

cheers,
DJDD

[Glenhuon]

I've been using my old 10x50 (S/H) Nikons for the last 15 years and still find them good for me at 60. Just bought a pair of 20x80's but that was more for the bigger light bucket than anything else :) The Nikons exit pupil is 5mm and I think the 80's are 4mm which still suits me fine. 10x50's will give you many years of use starting at late 30's and they are lighter for hand holding than the bigger aperture bino's.

[erick]

especially with my 8" dob strapped to my back :screwy:

[DJDD]

thanks for the reply, Glenhuon.

It sounds to me that the 10x50's are a great all round choice that will last for a long time.

And that exit pupil, whilst important for a novice like me that wears glasses, is probably of lesser importance than eye relief.

cheers,
DJDD

[DJDD]

you know, I thought about that last night but decided it is not feasible.
:lol:

cheers,
DJDD

[DJDD]

well, the AOE 10x50HR binoculars have been ordered. :)

hopefully they will arrive early next week so I can get some practice in before the lunar eclipse.

thanks for everyone's advice and comments,
DJDD