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Dear Bruce,
I am glad you purchased an SNO-T inverting scope,
so I can discuss some specific points with you
(maybe we should do it off-the-list, I am not sure).
It seems to me that my inverting scope has the following problems:

1. It won't simultaneously focus on a remote object
(a star) and the cross hair. From what I read about Kepler
telescopes of this type I conclude that the cross hair assembly
should be adjustible by changing its distance from
the objective lens. This does not seem to be the case
with my scope, but actually I am not sure. Do you think the black
part of the tube which holds the cross hair can be moved
somehow with respect to the objective lens?
It has two holes which look like the holes for an
"optical spanner wrench" but on the other hand, I afraid that
this part is glued to the main tube, so I'm afraid to break it
by trying to adjust.

By the way, the cross hairs are barely visible or invisible
when it is really dark... and I suspect they were not designed
for Lunar distances.

2. Bright objects like stars and sometimes the sun are surrounded
by some spots ("coronas") of light which look like hair growing from
the object. If the object is exactly in the center of the field
of view, and my eye is exactly on the optical axis,
the star is visible in the middle of this
"corona" of light. When I shift a little my eye or the sextant,
the corona becomes excentric, and sometimes shifts completely
to one  side (so that the "hair of light grow" only
on one side of the star). A professional astronomer explained
that this kind of aberration is called "coma", and it is typical
for Kepler scopes. Do you notice anything of this sort in your
inverting scope? I found that this aberration does not influence
much my star observations; the star at the vertex of its "coma"
is sharp enough, but sometimes it obstructs my sun observations.

(That's why I said once that the inverting scope
seems to work better at night (I mean star-to-star distances)
while the
Galileo one is
better for the sun, which is exactly contrary to the Russian
SNO-T manual: "to use the inverting one in daytime and the
Galileo one at night".
I agree that the star scope (Galileo) gathers more light.
But the 7x30 inverting one, despite its coma aberration seems to have
better resolution and better
permits to tell the moment when the images
of two stars collide).

> The wires are nearly 2 degrees apart in the field.
> Two vertical,
> two horizontal. Why the horizontal ones, I don't know.
> But they do make it easy
> to measure the angular distance between wires.

Apparently these wires were fitted not for lunar distances
but to help the observer to hold the objects in the middle
of the point of view. That's why there are 4 of them
making a square rather than a cross in the middle.

> or do accurate
> work with an artificial horizon, you'll find the
> inverting scope invaluable.

Could you explain more about how the cross hair help with
artificial horizon?
Do you mean a Davis-type or bubble art horizon?

> My guess is, a right-side-up scope with a reticule
> would be far more
> expensive.

And more importantly, it would let less light through.
As I understand at least two extra lenses or prisms are
required to make the image straight.

(Contrary to what many people say, I experience no inconvenience
with this inverting scope. Maybe because I never used a sextant
and started learning with both types of scopes simultaneously.
This shows that this "inconvenience" is just a question of habit.)

Alex.

   

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