ATM [Fwd: Bino-viewers]

[Mel Bartels <mbartels@efn.org>]

Mattunes@aol.com wrote:

> Hi all ATMs,
>     My questions are: Do many of the large Dob (say, >14" ) owner/operators
> out there use these very expensive (>$600) Bino-viewers regularly?  It would
> seem to be a given for certain "favorites".  Any experience with brands and
> type (mirror vs. prism) would be very appreciated.
>     I've read estimates comparing aperture and resolving power that claim a
> bino-viewer plus all the optical cortex don't result in halving the light that
> hits each eye (or less, allowing for imperfect reflectivity) but effectively
> "seem" to approximate around 75% of the objective's size, such that a 16"
> would appear to the brain like looking through twin 12" (or so).  Does this
> claim jibe with experience?
>     Since I'm building a 16" from the grit up (my first effort, inspired by
> Greg Babcock), and want to incorporate a quality bino-viewer, are there any
> f/ratio considerations to um...consider?  I'm looking at f/5 to f/8.  (Is coma
> a problem for focal reducing masks on f/5 mirrors?)
>     Finally, I have heard rumors of someone who makes a kit version of a
> mirror style bino-viewer.  Presumably more affordable.  Any links?  Thanks.
>     Clear (and dark!) skies...
>
> Matt Terry  (Tampa, FL, USA)



--
Clear skies, Mel Bartels
http://www.efn.org/~mbartels