Binoviewers can be a pain

[dobsonian]

Hi,
Recently, when using my AE binoviewer I had a lot of trouble trying to get a fused image. I was using my 250mm F5 dob, and after about 20minutes I gave up I was using two 20mm Meade 4000 type eyepieces, with a 2Xbarlow. I suspected that the binoviewer was collimated badly. However when I fitted the device to myF9 130mm refractor, it worked fine. Something to do with the angle of the cone of light from the objective?
Regards,
John.

[terrymoseley]

Hi John,

I haven't heard of that problem before. Have you checked any other websites for info?

Did they fail to fuse just laterally, or was there another problem too?

Have you another matching pair of EPs with different focal lengths to try on the Dob?

Terry

[dobsonian]

Hello Terry,
The problem solved. Just fold down the rubber eyecups on the Meades and a wonderful stereo image appears. Mind you, the fact that a barlow has to be included in the optical path in order to get the thing in focus does not help. With my 250mm dob the overall power with 20mm Meade 4000 eyepieces is 125, and with 10mm 250. The higher the power the more critical any adjustment becomes.
John.