Binoviewers will not focus.

[superuman]

Hi I hope someone can help. I recently purchased as set of Revelation Binoviewers and cannot get them to focus at all. I’ve tried attaching them to my Skywatcher Heritage 114P. I’ve tried maximum and minimum focusing but to no avail. I’m using two 17mm wide angle eyepieces. Thanks.

[Ricochet]

You will need to screw the nose piece from a barlow to the front of the binoviewers. With no barlow the binoviewers have an optical path length of about 110mm. This means that you would need to wind the focuser in 100mm from the point at which you normally focus to use them this way. Different barlows will change the amount of in focus required by different amounts, so you will have to experiment with the barlows you have to see if any of them produce useful results. 

[Cornelius Varley]

Try placing a barlow lens between the focuser and binoviewer. The problem is that the binoviewer adds extra distance between the eyepieces and the position where the eyepieces need to be to reach focus. The barlow lens will move the point of focus outwards which, hopefully should be sufficient to reach focus. You might also find that just the lens screwed onto the nosepiece is enough to move the point of focus outwards.

[superuman]

Thanks for your help guys, much appreciated...

[Louis D]

I use the nose piece of a 1990s vintage, Meade Series 4000 140 APO 2x Barlow screwed into the nose piece of my Arcturus binoviewer (same as the Revelation) to reach focus in my Newt.  It works out to yield 3x magnification, which isn't bad considering the Barlow alone yields 2.4x rather than 2x.  The field of view is sharp and color free from edge to edge, but wide fields of view are not possible with this setup.  These Barlows come up used for $40 or so on this side of the pond quite regularly.

Not all Barlow nose pieces are removable, and not all that do are 1.25" filter threaded.  For example, the Tele Vue 1.25" 2x Barlow is threaded smaller and thus won't grab 1.25" female filter threads.

To achieve wide fields of view, I added a 0.5x 1.25" focal reducer and 45mm of 1.25" spacer tubes between the binoviewer and the Barlow nose piece to reduce the magnification of the Barlow and make a home brew OCS/OCA/GPC since I had all the parts anyway.  However, this results in massive field curvature, so it's not at all a perfect solution.  However, scanning rich star fields with two eyes with such a setup is still gratifying if you focus your attention strictly on the center of the field.  It's just not useful for critical observing edge to edge.