Re: How to distinguish 160 vs 170 mm eypieces?
- From: Rich <none@xxxxxxxxxxx>
- Date: Sat, 18 Apr 2009 21:18:19 -0500
Kevin Cunningham <smskjc@xxxxxxxxxxxxxx> wrote in
news:02540564-68cb-426f-aeb3-2cb95b5f925d@xxxxxxxxxxxxxxxxxxxxxxxxxxxx:
On Jan 11, 10:48 am, "Neil B." <neil_del...@xxxxxxxxxxxxxxx> wrote:
"Kevin Cunningham" <sms...@xxxxxxxxxxxxxx> wrote in messageww.surplusshed.com/pages/item/l1864d.html.
news:e6da30f7-5064-4c72-b33e-b38cca635d27@xxxxxxxxxxxxxxxxxxxxxxxxxxxx
...
Theo,
Actually the focal length for a 170 mm is 163mm. The primary
difference is how far out of par focal you go at low power. At 20X
and above there isn't that much difference, at low power you can
tell.
A 160 mm is noticeably longer from the edge of the eyepiece tube,
the area out side the eyepiece tube, to the end of eyepiece.
Thanks,
Kevin Cunningham
SMS
Theo Griep wrote:
I have both Orthoplan and Dialux microscopes, and many eyepieces.
All second
hand, and ofcourse I don't know what has happened with them over
the last
decades, maybe (/probably) eyepieces have been changed.
I've read everything I could find on the web about 160 vs 170 mm,
there
seems to be a difference between 160 and 170 mm eyepieces, you
should use
the right one on the right microscope (160 on Dialux and 170 on
Orthoplan),
but I couldn't find how to find out the difference between the
two.
Theo
Thanks for deeper tech dish but in any case, I didn't think eyepieces
(in contrast to objectives) had to be optimized ("within reason") to
a projection distance anyway. Just think of telescopes for example -
"9mm eyepiece" does not specify a focal length or f-ratio of the
telescope, unless some special optimized for very short fl (more
like, f-ratio anyway) etc. Indeed, I thought the virtual image was
pretty much "given" without containing much information, as it were,
of how far it was projected from. So I always thought for the most
case, "10x" eyepiece was just a standard 25mm (or is it 25.4mm per
controversy over English or Metric standard viewing distance?) "per
se" eyepiece. For example a Huygenian, just as well could be put in a
telescope and vice versa. Is that so?
BTW these folks have lots of good stuff it seems, try for
examplehttp://w
Comparing telescope eyepieces to microscope eyepieces just doesn't
make any sense. Telescope eyepieces are there to magnify a large,
distant object, microscope eyepieces magnify a tiny, close object.
Each is a different type of optics, no similarity.
Want to be shocked? Take a pair of Plossl or Orthoscopic telescope
eyepieces (say, 20mm's) of decent quality, and subsitute them for the
kind of eyepiece (compensating, doesn't matter) used on microscopes in
the 1970s and before. Your field of view will increase vastly and image
flatness and edge clarity will be FAR better. Huygens, Kellner, Ramsden,
etc, eyepices are terrible, for microscopy or astronomy.
.
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