Terrestrial Binoviewing

I start the binoviewer test for terrestrial use. I believe this is not what any spotting scopes can do. I selected Baader one among many available in the market since it allows T-thread connection. I thought it is more secure and less light path.

The above is the setup with BORG 125SD and BORG erecting prism(# 7778). Main focuser is removed since eyepiece focuser allows for fine tuning. Surprisingly, I can reach the focus up to around 100m away with a regular long tube (360mm long). As anticipated, yes vignetting. Looks like 5 inch scope is stopped down to 4.  But as expected, binoviewing is very comfortable. This is not hand-held like regular binocular. But this allows for high power binoviewing, which can’t do with any spotting scopes and binoculars. This is really BORG-like concept.

I got Baader’s 45-degree amici prism too. This is 2x barlow buitl-in diagonal. So this might eliminate vignetting issue. But darker. So I wonder which way is more practical.

W/ BORG prism: straight-thru viewing. Focal length remains unchanged. But vignetting. If I suppose the actual aperture is 4 inch, it might become around F7.5. Still not bad. I wonder this calculation is correct. BORG prism is very good made. But issues are heavy and unfortunately expensive.

W/Baader prism: 45 degree. Probably I hope no vignetting. But F number will be F12 – darker. But it should be good advantage for higher power while staying same eyepieces.

I will keep playing around and try to find out the good solution.


~ by tedishikawa on December 7, 2011.

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