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Binoviewer Zooms for Lunar?

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I’m thinking about getting a pair of Baader Zooms for my MaxBright 2, mainly for Lunar work.  The adjustability of the Zooms will, hopefully, optimise the view in variable seeing. 

However, I would like a bit more magnification than the raw Zooms provide, so there are several competing options. 

Would I be better off:

a)    using a Baader 2.25X Barlow on each of the zoom eyepieces, plus the 1.25X Glass Path Corrector in the Binoviewer?  OR

b)    Ditch the 2.25X Barlows and the 1.25X GPC, and just use a 2.6X GPC in the Binoviewer? (Baader say you can't stack GPCs)


Concerns would include:

  • Not sure if using multiple  Barlows would screw up the focussing
  • Not sure if using a GPC before the BV and Barlows after it would work.
  • Adding extra glass will reduce brightness.  The nominal target is the Moon, so that shouldn’t be too much of a problem.


Anybody used zooms on a binoviewer, and got any thoughts?

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Hi Bryan,


My take on it.....

I've tried zooms myself, but, to be honest i've never been a big fan of them. Managing 2 of them in the focuser in darkness is tricky, hoping they are in the right positions.

They are big and bulky too with a binoviewer, but as they often say over on the CN forum, YMMV (your milage may vary) 😉


Rather than a barlow or whatever, i would just get a 2.6x gpc.

Using a 2.25x barlow between the bino and the eyepieces may do some odd things, and throw the focal plane way out, and they won't correct for sphero-chromatism either,

which is what the gpc's are part designed to do especially at higher powers where it certainly interferes the most.


But if you do  decide to use zooms they will give you 100x - 300x in your 132 refractor. And its a good night in the UK if you're using 200x +


I much prefer the views through fixed focal length eyepieces with 24's 19's and currently 14's for my high power option. My 14's give me around 170x which is usually more than enough.

And the Baader viewers make switching eyepieces a doddle.


As i've mentioned before i have two diagonals : one for native viewing at low mag, and then when i want to crank up the power i change over to the other one

which has the 2.6 gpc in it permanently for my convenience as much as anything. I also have the 1.25 & 1.7x options but seldom use them unless i'm doing solar.


Remember the 2.6x gpc goes in to the diagonal, rather than the back of the viewer.

I don't know why its like that, there must be a reason for it ; i'm not sure. What i am sure of is that Roland Christen knew what he was doing when he designed them.


Btw, i've recently purchased a Maxbright 2 and i'm very impressed.

The eyepiece holders with their clicklocks and easy diopter adjustment are a joy to use.


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Thanks Rob. 

I've ordered one zoom and I'll see how I get on with it. 

I may end up just using a 2.6X gpc with the existing fixed lenses (19mm, 12 mm and 6.7 mm).  But the ability to crank up the power in a jiffy is attractive so I'll persevere a little.

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Cant speak for zooms in binoviewers but I have 2 Vixen 8-24 LV zooms I use in my binoscope but youve got me thinking about barlowing now. I have a Vixen LV 2x already so I feel an addition to tge eyepiece box is imminent.

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  • 2 months later...

Perhaps because I've been spoilt by my fixed eyepieces, I was disappointed in the Baader Zoom's image quality - lacking in clarity and contrast compared to what I was used to.  The lens has now been moved on.

My bino setup now consists of 19mm Panoptics and 12 mm and 8.5 mm Pentax XFs, with 1.25X, 1.46X and 2.6X Glass Path Correctors with the 1.46X (aka 1.7X) being favoured.  If I could trade the 19mms for 24s, I would.  Otherwise the difference wouldn't justify the cost of the 24s.

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