[janoskiss (Steve H)]

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.

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.

My question is ...can you use a binoviewer with a dob without those multiplier lenses to reach focus?

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)

Will two 25mm plossls (60x magnification in the dob) give me 60X mag in the binoviewer?

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.