10 replies to this topic

[dblstar]

I've been considering a binoviewer for my TeleVue Oracle 76mm f/7.4 triplett. I've never owned a binoviewer or looked through one but thought it might be an option vs a 70 or 80mm binocular.

 

Has anyone had experience with this set up? 

 

Any recommendations for a binoviewer, say up to $500?

[plunk111]

I have a Denkmeier binoviewer and it won't reach focus on my TV Pronto - even with a couple of barlows. I suspect the Oracle would be similar, but YMMV. 

[betacygni]

Any refractor can be made to reach focus with binoviewers, typically it will require about a 1.5x or so amplification value to achieve it though, which will of course reduce your true field of view some.

If wide field is your only goal, at these apertures you’re much better off with binoculars. A 50mm pair of binoculars will exceed the wide field performance of a binoviewed 80mm class scope (and roughly equal that of a 90mm binoviewed scope). If you however plan to use them for medium to high powers also, then binoviewers still make sense even at these smaller apertures.

As for which binoviewer, with your budget i’d look for a used pair of Maxbright II binoviewers and pick up a 1.7x glasspath (which should be enough amplification for you to reach focus). They are the best entry level/mid range units. You can go cheaper, but are rolling dice a bit on quality, eyepiece holders, and collimation. Not worth the risk vs buying a quality unit like the Baaders.

Edited by betacygni, 07 February 2025 - 12:05 AM.

[GGK]

I've been considering a binoviewer for my TeleVue Oracle 76mm f/7.4 triplett. I've never owned a binoviewer or looked through one but thought it might be an option vs a 70 or 80mm binocular.

 

Has anyone had experience with this set up? 

 

Any recommendations for a binoviewer, say up to $500?

+1 on betacygni's reply.

 

I don't have the Oracle, but my TV-85 is likely similar.

 

I use two different binoviewers - a Baader Maxbright II and Zeiss prism binoviewer with a 25mm clear aperture.  I purchased both used for around $400 each.  Both are great, but I prefer the Maxbright II because of the clicklock eyepiece clamps. Both of my binoviewers have dovetail fittings that fit into the female end of a Baader T2 Quick Changer so I can connect directly to the diagonal without a nosepiece or eyepiece clamp, which reduces the light path (less Barlow power needed to reach focus)

 

My set-up uses a Baader T2 mirror diagonal with a 2" nosepiece and a Baader T2 Quick Changer on the other end connecting to the binoviewer,

 

The TV-85 will not reach focus without a Barlow (to extend out the focal plane and compensate for the long optical light path of the binoviewer), but I'm able to reach focus using a 1.25X Baader GlassPath corrector (GPC) when observing with 24mm Panoptics, all Delites, and Pentax XFs.  The GPC is a small lens element that screws into the top of the diagonal and adds zero physical length to the assembly.

 

Here's a picture of a T2 diagonal with a 2" nosepiece on one end and a GlassPath corrector and half of the QuickChanger installed on the binoviewer end:

 

 

I use the binoviewer for high power observing in all of my scopes. I generally see more faint detail with two eyes, and I likely see the same detail at 150X with the binoviewer as I do with about 180X with a single eye.  But this is just an opinion based on nothing but my perception.

 

I also change to a binoviewer at the end of a long session with my SCT even for lower powers when my eyes are tiring because it reduces my eye strain and enables me to extend the session another hour while maintaining eye comfort.  Again, this is just a personal thing, and I don't know if it's common to others.  I'll change eyepieces for more power, but I also have the option to use a 1.7X and 2.6X GPC if I want to stay with a certain pair of eyepieces.

 

One last point - I believe less expensive binoviewers are optically good too, but might not have self-centering eyepiece holders and likely have smaller prisms and a smaller clear aperture that will show some vignetting if using eyepieces with a 27mm field stop diameter for widest field of view.  I've read that vignetting usually doesn't show as long as the eyepiece field stop diameter is not more than 2 or 3mm larger than the binoviewer clear aperture, but I have no experience in the smaller clear aperture models to know.  I've given away a few 25mm Plossls for people to try binoviewers and have never had anyone complain about vignetting with those in even the least expensive binoviewers.  

 

Good luck,

 

Gary

[Lentini]

You could always try linear binoviewers, which don’t require any back focus or added magnification. There are threads devoted to the pros and cons.

[Lentini]

I have an Oracle and linear binoviewers, but haven’t used them together. I’ll post a note on first impressions  if I can get out in between clouds.

[Lentini]

So, to prepare for testing linear binoviewers with the Oracle, I realized my newly installed Finder would have to be moved, as I had it installed straight behind the Finder, and binos would block it. I also had to reverse the dovetail to give myself more accommodation of the added weight.

But that all worked well. Had a quick view of Venus before waiting on it to cool.

Should all work well… I’ll add a report tonight.

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[Lentini]

Jupiter had the “flare” in one axis, but was easily ignored. I was surprised at the view… Very good, with nice detail and not noticeable false color fringing. I was using 7mm TeleVue DeLites, btw.

The Orion Nebula was big and beautiful, or as good as these Bortle 200 skies in Northern Virginia allow. The Trapezium was surprisingly sharp, but I didn’t see E and F stars.

Eye placement was a bit tough, but I didn’t bother extending the DeLite eyecups. Too much hassle.

The Moon was really good, too, but when I saw some color fringe, I realized it was only one eye… one eye had none, and the color was all from the other. I didn’t have the diopter adjusted well… Adjusting it removed the color.

I usually use a 7mm Nagler Type 1 with this scope, so I didn’t have experience with single eyed DeLite to compare with. I’d say maybe it was less sharp than the Nagler single eye view. But the comfort of two eyes balances that.

There was certainly some room to improve with more attention to diopter adjustment and DeLite eye guard extension. But I think first impression is that the binoviewers work well with the Oracle.

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[Spikey131]

What diagonal are you using?

 

Are you using a GPC?

[Lentini]

The diagonal is the original TeleVue diagonal that came on the scope. No GPC.

[Spikey131]

A GPC might clean up some of the false color.