Re: Why not Rigel?

"David Knisely" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> Art posted:
>
> > I have been pondering the pros and cons of the Rigel verses Telrad
finders.
> >
> > Because of the smaller footprint and lighter weight I lean towards the
Rigel.
> >
> > Is the advantage of the three ring Telrad target enough to change my
choice?
> > How do you feel about one over the other?
>
> Not to "steal" my own thunder (article on it will be appearing on
CloudyNights
> soon), but the main advantages of the Telrad are that it has a 3-ring
reticle
> and its window is larger than that of the Rigel.  This makes it a little
> easier to do extended star hops, and also makes eye positioning less
critical
> than the more tight requirements of the Rigel (you often have to have your
eye
> almost right behind the Rigel's little window just to see the reticle).
The
> Rigel also shows a small amount of parallax as you move your head around
(the
> rings move a bit), while the Telrad shows better performance here with
zero
> visible parallax.  The Rigel rings also become slightly distorted at long
eye
> positions and the parallax becomes worse.  The Rigel is smaller and
lighter
> than the Telrad, but it is also made of a thinner grade of plastic than
that
> used in the Telrad (easier to break).  The Rigel's tiny acrylic window is
only
> glued down on one end, so the window can be more easily broken out of its
> housing by accident, either in storage by something like a loose pen or
> pencil, or by a finger during operation.  The window is tiny and set
inside a
> small housing which can make cleaning it a little more of a chore.  Its
hood
> provides slight dewing protection, but unlike the Telrad, you can't easily
> wipe the window off if dew forms on it.  The Telrad's window is made of
hard
> glass, so a simple cloth can be used for cleaning, and there is no hood to
get
> in the way (although this also means that an external dew shield is
needed).
> That having been said, I have a Rigel on my 100mm f/6 refractor and a
Telrad
> on my 10 inch f/5.6 Newtonian.  Both are useful, although for the most
part, I
> do like the Telrad just a bit more.  Clear skies to you.
> -- 
> David W. Knisely  [EMAIL PROTECTED]
> Prairie Astronomy Club: http://www.prairieastronomyclub.org
> Hyde Memorial Observatory: http://www.hydeobservatory.info/
>
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I think David Knisely's assessment is right on the money.  Even though  we
have 3 Rigels and no Telrads, I consider the Telrad a more robust product.
That said, I think there are advantages to the Rigel (as noted above) and
for us, these out-weigh the disadvantages.  I would try them out and decide,
but you will probably be satisfied with either.

Dennis