[DJDD]

Originally Posted by erick

In that case we start again

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.

that sounds very reasonable.

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/ubbthrea...ard/binoculars

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

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!

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.

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.

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


cheers,
DJDD