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Most
of this article is from the March, 2003, issue of Bird Watcher's
Digest, "Taking a Complete Look at Scopes," by Michael
and Diane Porter. Here, not limited by space constraints of paper
publishing, we provide an expanded version of the article, with
extra material.
Part I —An Overview of the New Scopes
 Wow!
Since we last reviewed birding scopes for BWD, manufacturers have
been competing to satisfy the needs and wants of birders. The result
is a whole flock of innovative designs that raise birding optics
to unprecedented levels of performance.
We
were as excited as kids at Christmas about trying out the new toys.
We tested about two dozen scopes. Most are 80mm or 60mm dedicated
birding scopes. A few are primarily astronomical scopes, but small
and portable enough to serve also as birding scopes.
How
we evaluated the scopes
 We
invited a team of Iowa birders to spend a day judging the new scopes.
We lined up the scopes overlooking a lake at Jefferson County Park,
in Fairfield, Iowa, and listened to what the birders said about
the pleasure of looking through each scope, about its performance
and ease of use. The team's judgements went into the individual
accounts, below.
Over the following weeks we continued to test the scopes in more
detail. Using a standard optical resolution chart, we checked each
scope from a distance of 70 feet. To rank them, we assigned a score
of 20 to the finest level that the sharpest scope could resolve
at 60 power.
Many
of the scopes came to us with 20-60x zoom eyepieces, which we used
to test each scope at 20x and 60x. Some had 15-45x zooms: those
we tested at 20x, to keep the scores comparable with the others,
as well as at 45x.
We
compared scopes to one another at the same magnifications whenever
possible. Each time we tested a scope, we also took a reading through
a reference scope to make sure our results were not affected by
eye fatigue or changing light conditions. We made repeated tests
on many different days. You'll find the results of these trials
on the chart. Bear in mind that we had only one sample of each scope
to test, and it is always possible that a particular scope might
have been an atypical production example.
We
were amazed by some of the findings. In past reviews, the Questar
has been our lodestar, by which we measured all other scopes. But
now other manufacturers have caught up with Questar. On the chart,
you'll find that top score of "20" in the 60x column for the Zeiss
Diascope 85 as well as for the Questar Birder.
Swarovski's
ATS80 and Leica's 77mm APO Telvid
follow extremely close with scores of 19. These are scores of almost
unimaginable precision. Holding the resolution chart in hand, we
could barely discern lines that we could distinguish easily at 70
feet using the best scopes. The detail at this scale is so fine
that the printing process of the magazine where this article appeared
would not be able to reproduce it!
 Some
of the new smaller scopes also astonished us with their clarity
and brightness at high power. The Swarovski ATS65 (photo at right)
and the Kowa Prominar TSN663-ED resolved detail as well as many
of the good 80mm scopes. These smaller scopes offer a tempting alternative
for the prospective scope buyer who wants to shave off a little
weight, size, and cost.
In
the next pages we detail some scopes of note, with an emphasis on
what's new since our "Scopes Roundup" in Bird Watcher's Digest,
July, 2000.
Continued
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