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Originally Posted by dugnsuz
I recently enquired at Fronteir Optics about the WO binoviewer's suitability on my 12" f5 GSO dob - Daniel said it was a no-go but recommended the Denkmeier model at double the price as a better option.
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Danial is right about the WO unit. As is or with supplied corrector it won't work. My WO style binoviewer focuses in the 12" with a long 2" 2x barlow, which gives about 2.8x with the BV, so my minimum magnification is around 170x. You could try and get a different lower power corrector lens for it though, or you could move mirror and focuser closer together.
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My question is ...can you use a binoviewer with a dob without those multiplier lenses to reach focus?
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Yes move your mirror/focuser. But at f5 you'll want something to slow down the light cone anyway, otherwise you will not get full illumination of the field. (path length / clear aperture = 1/5 for WO binoviewer, so at f5 and faster the light cone is too steep to properly illuminate the focal plane)
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Will two 25mm plossls (60x magnification in the dob) give me 60X mag in the binoviewer?
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The lowest magnification you can hope for with the WO style unit is probably about 90x, and that will require buying a low power corrector, and then only the central 20 degrees or so will be fully illuminated. But in practice that is probably not as bad as it sounds.
