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Subject: [M]: Re: Binoviewers
From: Dave Pisak
Reply To: mapug@shore.net
Date: Tue Mar 03 04:50:35 1998



>Date: Mon, 2 Mar 1998 12:00:58 -0500
>From: crzarnke@scaleable.com (Bob Zarnke)
>Subject: [M]: Binoviewers
>
>
>I also decided that I want to use a binoviewer and have read Todd Gross'
excellent discussion and John Shibley's review at the
>Televue site.
>
>Todd says that the f/6.3 telescope would be a better choice than the f/10 to
use with the binoviewer for medium/low power
>wide-field viewing. How much difference does the f-ratio make. What would be
the lowest effective power I could expect to get with
>the binoviewer.
>

Without the barlow expect a 20% power boost due to the extra 5.5" of light path
and the different
mirror position to reach focus with the binoviewer. Min. power would be around
60X with 10" f6.3
(32mm plossl).

>John says that it is unnecessary to use the Barlow lens (included with the
Televue) for telescopes with higher f-ratios, such as
>the f/10. Does this apply to f/6.3 telescopes too.
>

The barlow is probably necessary with most scopes in order to reach focus. SCTs
have the advantage
of long mirror travel and can reach focus without it.

>What are other member's experiences using the Televue or other binoviewers,
particularly about which eyepieces to use.
>

I use the Tele-Vue unit with my 12" LX200 and love it. Single eyepieces are no
longer used for planetary
viewing, it is that much better. Globular clusters are a toss up, views take on
a three dimensional efffect but are slightly less resolved than with one
eyepiece.

Best eyepieces to use are 19mm Panoptics followed closely by 18mm superwides.
Plossls work very
well, but wide field eyepieces give a more pleasing view IMO.

Good luck

Dave