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That means most BVs are being used for high-power observing

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Mine certainly do quite a bit of that ... but certainly not exclusively.
mike b

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"I have been paddling in the shallows of a great ocean of knowledge." - Sir Isaac Newton

* * 15" F4.55 Starsplitter Dob & a Denk II binoviewer * *

http://peaceofsky.wordpress.com/

Pacheco State Park
Fremont Peak

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I think the only "bad" scopes for BVs are those that aren't really good for monoviewing also. Very small aperture, poor optics, or narrow focal range.

There are some scopes that are "easier" to use in BVing and some which are more difficult. But in general, a good scope is almost always a candidate for BVing.

My :twocents: [Hmmm, the twocents graemlin is gone]

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Gill-

....More recently, Denk has come out with yet another Newt corrector, enabling them to work at their native F#... no Barlow effect at all....

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That means most BVs are being used for high-power observing

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I purchased one of Denk’s “Newt focal reducer” lens units at NEAF this year (along with D21s, all at a substantial “show-special discount”, saving over a $100). It fits into the Denk bino above the PowerX switch. This adds yet another “lever”, giving me four power settings with one pair of eyepieces ( I use Denk 21s and Rini 30s). My Obsession 20 will only come to focus with the higher power OCS ( I have both), even with that, the field of view at the lowest setting is the same as the “native” field/power of the eyepieces used. If I were to cut the poles on my Obsession for a little more in-travel, I could use the low-power OCS, and then the new “Newt reducer” would actually work as a true reducer, giving an even lower power and wider field of view than that provided by just putting the eyepiece in the scope. Of course this adds even more glass and weight, but that is not so much of an issue with a 20-inch.

Bottom line: This rig allows what I would normally consider low-power/wide-field observing with a bino-viewer on a 20-inch F/5 Newt that is the same as what I did most ‘mono’ observing at. Being able to ‘click’ between 4 different powers is a big advantage over switching eyepiece pairs when you are 3 rungs up a ladder!!

BTW, the scope will come to focus with the low-power OCS, but it sticks about 2-inches into the tube, so I don’t use it.

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George N

Obsession 20
Optical Guidance Systems 10" F/9 R-C Cass
6" F/5 & 8" F/8 home-made Newts
Explore Scientific 127mm ED
MI-250 mount
Denk II bino-viewer, with PowerX and Newt reducer
SBIG STL-1301E CCD
Member, International Dark-Sky Association

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You must use light binos. Use ultralight eyepieces. I use EF19 for low power and Brandons for higher mag. Siebert's eyepieces should also work. To reach focus, Siebert's 1.25x OCS is very light, but more than one inch of it will stick into the optical path. Harry made mine with T2 threads so the Maxbright will attach directly. This also allows the bino to rotate in the T2 coupling so you can easily reposition it for different parts of the sky.

With these considerations, the portaball works well for binoviewing and gives some really nice images.

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Steve,

Thanks for posting this. I have a friend that has both the 8 & 12.5, and I LOVE these scopes. I used to own a 14.5 Starmaster but have thought about picking up a PB for years. I always balk because of the BV use issues with it. This combination might be the ticket.

I had written to Dave Juckem about possibly overcoming the balance issues with a BV and he did say he was working on something that should make it easier to use a BV with the Portaballs, but I have not yet heard back from him as to whether or not he was able to implement the enhancement. At least now I know it is possible to make it work even if Dave is unable to successfully integrate something on the scope itself. Thanks again.

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Kerry

• Astro-Physics 92mm f/7 Stowaway
• Takahashi Mewlon 210
• Denkmeier BV
• Giro III mount
• Brandon, Nagler, Leica single EPs, UO Ortho and Edmund RKE Binoviewer sets

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At this point, I need to select the telescopes and accessories. Currently I am thinking about purchasing the following scopes over the next two years: Meade EXT-125PE 5" f/15.0 Maksutov Cassegrain compound w/ GoTo, Discovery 15" f/5.0 Dobsonian reflector (if it will be friends with the Denk), and an APO 4" or 5" refractor. I want to do binoviewing on all three scopes. As I said earlier in this post—if I cannot observe at a particular scope with Binocular viewers, then I do not want to keep that scope.

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I have the Denk Std Universal Power Switch. I use it in my AP refractor, my 10" dob, and in a Tak Mewlon 210. The universal package, whether standard or the II's, should get you most of the accessories you need for most scope designs. I also highly recommend the Power Switch - nice feature for changing mags without changing EP's so much.

As EdZ suggested, get the reducer for the Maks, and I also had to get " Part SR " (I think that's right) which is a 2" low-power OCS for use with low-profile diagonals like the AP MaxBright or TV EverBright. It screws into the field end of the diagonal and helps the backfocus issues with low-profile units. You may want to call Russ and verify that's the correct Part #.

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Kerry

• Astro-Physics 92mm f/7 Stowaway
• Takahashi Mewlon 210
• Denkmeier BV
• Giro III mount
• Brandon, Nagler, Leica single EPs, UO Ortho and Edmund RKE Binoviewer sets

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