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Bill,

> Many thanks for drawing attention to Shufell's paper,
> which has much more of interest than just the dip meter, including the
> use of sextant telescopes with very high (x16 or x20) magnification

They mention some yacht from which they made these observations
but I suppose the yacht was moored in the harbor:-)
My moderate experience suggests that such telescopes cannot be used from a
ship less than 10,000 tons in the ocean, even in good weather.

> having 50 mm objectives with mirrors to match.

This is for twilight sights. I've seen some 50mm telescopes on e-bay
fitted to C Plaths and even to some very old (pre-SNO) Russian sextants.

> used a 7x 30 monocular all the time,

7x30 prizmatic I tried once, and found no advantages in comparison
with 6x30 inverting. But the 6x30 inverting weights a small fraction
of the prizmatic. To pay for the upright image with this weight makes
no sense to me.

> conditions than the x4 Galilean supplied with the sextant.

Yes. And 6x30 SNO inverting seems much better to me than the standard
sextant Galilean telescope in all cnditions.

> I imagined that the dip meter would be based somehow on the Blish prism,

It definitely has two prizms and one mirror.
First I thought "what is the mirror for?" One can rotate one prizm, but
now I think I understand why a mirror is needed.

The picture in the last page of Shufeldt, in cubist style, is not very
informative. And for the Russian one, I only have a picture from the
outside. I can only conjecture what is inside.
I have a slightly better picture of Shufeldt's dip-meter from outside.
(Picture No 2 of his report). It seems more complicated than the
Russian one.

Today I scanned Russian-language Internet, and found that two N-5 were
recently sold on some inner Russian analog of e-bay. No pictures. I
registred for this
"Russian e-bay" and will try to watch. If all Soviet ships were supplied
with this, I hope I will find one sooner or later.

> I should very much like to have a copy of the
> Russian account of the meter.

The Russian one has different shape. I will scan and post it tomorrow
together with better exterior picture of the Shufeldt one.

> As
> my studies of Russian have not advanced

I will translate the description.

> This reads like a challenge that I may well take up

It was intended as a challenge. I just tried to express it gently:-)
Myself, I never did with my hands anything more complicated than a simple
home repairs. Yes, besides this, I cleaned one old C. Plath:-)

Alex.
P.S. BTW, here is a Russian sextant called SNO-M-T.
Very rare, I suppose. Looks like SNO-M, but somehow "tropicalized",
whatever this means. http://www.maurnavy.com/
Item 12 from the top, $248(sold).

   

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