To: olympus@xxxxxxxxxxxxxxx
cc: lhawkins@xxxxxxxxxxxxxxxxxxx
From: Steven Read/CAM/Lotus @ NOTES@ALPHABETA
Date: 12/22/98 09:54:50 PM
Well after writing the following and then reviewing Lee's post, I'm convinced
he's not going stargazing - besides I rather suspect he's got access to some
really good telescopes. However those of you, who like me are forever trying to
make out comets or even Orion's belt in light polluted skys, may get something
from this and hopefully not repeat my mistake.
Someone said "magification" in the same paragraph with astronomical as though it
were a good thing, to which I reply (without naming names ;-):
For stargazing on the cheap (those monsters from Meade et al are too darned
expensive, you're better off getting a small Newtonian) I had always thought
that what really mattered was the size of the objective lens - read light
gathering - and about magnification - who cares, stars are point sources and the
Moon is to big for comfort without getting 10x'd thus I ended up with Nikon
10x50's for comet gazing, and they're ok . Unfortunately, I didn't RTFM and I
didn't know about exit pupil, most binoculars are set up for an exit pupils of
~3 to 5mm, just right for daytime viewing. But now I'm in the dark trying to
make out a faint comet and my pupils are wide open, and... the exit pupil is
still 3-5mm.
Exit pupil = (Objective lens diameter)/Magnification
so my Nikon "Stayfocus Plus II" 10x50 = ~5mm not too bad. But I could have had
a much brighter set of binoculars. The Olympus "Pathfinder" line has a 7x50 =
7.1 eye relief of (5 elements/3groups) and an 8x42 = 5.3 (6 elements/4 groups).
The Nikon line also has a 7x50 with an exit pupil of 7.1 and eye relief of
16.4mm (rest of line is 9mm)
<< here's hoping the table comes through readably>>
|--------------------+-----------+----------+------------+--------------------|
|Model |exit pupil |eye |relative |Notes |
| |(mm) |relief** |brightness* | |
|--------------------+-----------+----------+------------+--------------------|
|Olympus Pathfinder |7.1 |23.7 |51 |5 elements/3 groups |
|7x50 | | | |790 grams |
|--------------------+-----------+----------+------------+--------------------|
|Olympus Pathfinder |5.3 |16 |27.6 |6 elements/4 groups |
|8x42 | | | |630 grams |
|--------------------+-----------+----------+------------+--------------------|
|Nikon Stayfocus |7.1 |16.4 |50.4 |975 grams |
|PlusII 7x50 | | | | |
|--------------------+-----------+----------+------------+--------------------|
|Nikon Stayfocus |5 |9 |25 |955 grams |
|PlusII 10x50 | | | | |
|--------------------+-----------+----------+------------+--------------------|
* not sure what this is based on, but both pamphlets I was working with had it
** the Oly pamphlet says eye reliefs over 13mm are considered long, and long eye
relief is "particularly important for people who wear glasses..." c'est moi!
___________________________________________________________
* * * Previous Memo History * * *
From: "R. Lee Hawkins" <lhawkins@xxxxxxxxxxxxxxxxxxx> @ ALPHABETA
Hi all:
I'm thinking about getting a pair of binocs soon, and was wondering if
the Olympus binocs are a good choice. I've suffered through some pretty
bad binocs in the past, so I want to make a good choice this time. I
really can't afford a pair of Zeiss or Steiner, though! The specific
models that I am interested in are the 10x42, 12x24, and (perhaps)
12x50.
Cheers,
--Lee
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