Focus Scientific

USED Jaegers 125mm (5\") f/5 Refractor w/ Zeiss Binoviewer

Condition: Good. Includes an adapted tool box (Tuff Box brand) for storage/cartage. Includes tube rings and dovetail.

The Jaegers 5" f/5 refractor is one of the venerable scopes of the '60s, '70s and '80s. A cemented achromat, it exhibits the expected chromatic aberration inherent to the crown/flint objective of such fast f/ratio. And so these scopes are employed principally as rich field deep-sky sweepers, or RFTs.

This scope has been optimized for use with the included Zeiss binoviewer. The focuser is a 2" Astro-Physics rack-and-pinion, as used on their Traveler line of telescope. The Lumicon 1.25" mirror diagonal has been modified so that it imposes the absolute minimum separation between it and the binoviewer. Furthermore, we further reduced the aperture loss imposed by the long optical path of the binoviewer by shortening the diagonal's front barrel. In spite of this, do note that the effective aperture is 105mm--it was worse before that barrel shortening.

Don't look upon the aperture reduction as all bad news. By effectively stopping down the aperture somewhat, the aberrations are reduced in magnitude! Now, if one were to obtain a 2" diagonal that permitted the same kind of very close coupling to the binoviewer, much or all of the objective would then be utilized.

One could also attach the binoviewer and current diagonal to a scope of focal ratio about f/6 and slower, thereby employing the full objective aperture. Provided the scope provides sufficient in-travel in order to reach focus. SCTs tend to meet this requirement.

The Zeiss binoviewer is something of a marvel. It has an optical aperture fully equal to the 1.25" format, or 31mm or so. Most binoviewers have paltry apertures of 21mm, and a very few offer 27mm. This beauty is humongous by comparison. Note however, that there is a subtle darkening at one edge of the cemented interface in the beamsplitter. But this introduces no readily discernible impairment.

Our photo was taken so as to peer straight down into one of the binoviewer eyepiece barrels. This reveals the considerable clear aperture of the prisms. Indeed, some folk would consider the binoviewer to be by far the more valuable component here.

Includes clamping tube rings and a Vixen style 44mm wide dovetail, for attachment to a wide array of mounts.