"Peter Abrahams" telscope.at.europa.dot.com wrote in message
4...
a refracting telescope based on H. D. Taylor's design

There is nothing earth shattering about Taylor's design. It uses one
abnormal dispersion flint in triplet configuration to achieve a modest
reduction of secondary spectrum, not 10x less.

It is unclear if this response was to Taylor's 'Cooke Triplet', as
titled, or to Taylor's 'Photovisual' triplet, as described.

But Taylor's Photovisual was a very significant advance beyond the
refractors of its day. Abbe / Zeiss and C. Hastings were involved in
similar work, but Taylor was right there with them, and Cooke was ahead
of them in production, which was unfortunate since the glass
deteriorated badly.
Some details on the glass, and more text than I really should send out
in a post to a newsgroup, are below, part of a text on HDT found on my
site:
----

SNIP!

Interesting read. Thanks!
--
Jan Owen

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