60 mm f/12 refractor binocular

· 7 inch aluminum irrigation tubing holds optical assembly.

· ¾” fir plywood bulkhead holds upper 60 mm Carton objective lense.

· A second bulkhead holds the lower objective which “looks” through a hole in the forward bulkhead.

· Brass knurled knobs adjust the forward bulkhead in relation to the rearward so both objective lenses are “looking” at the same point in the sky.

· Lower knobs on back adjust an interior secondary elliptical mirror to send light cone from lower front objective upward to left hand eyepiece.

· Upper knob on back secures an interior elliptical mirror which sends light cone from upper front objective to right hand eyepiece.

· To accommodate interocular spacing the left hand eyepiece swings inward or outward and the lower elliptical is adjusted to “follow” it.

· Upper eyepiece platform is mounted with nylon spacers to maintain alignment with tube.

· Left hand lower knob captures the eyepiece assembly which pivots on the upper left hand bolt.

· Focusing Kellner eyepieces provide variable focus for each eye.

· The eyepiece base and upper ring as well as moveably ring are made from ¼ inch masonite.

This binocular, at f/12 with excellent Carton achromats will resolve the bands of Jupiter and the rings of Saturn and show fine lunar detail. It is two 60 mm refractors working in tandem. The upper light path secondary can be collimated accurately while the lower light path is always out of collimation to accommodate interocular spacing. 28 mm Kellner eyepieces result in 26x. I tried higher magnification but found above about 35x the difference between the accurately collimated light path and the de-collimated light path became noticeable. The 26x provides a good balance between detail and light and it is very difficult to see any difference in the two images. Internal reflection is diminished by a panel dividing the tube in half length-wise, isolating the two light paths. 2 1/3 inch elliptical secondary mirrors on diagonal mounts (just like the mount found on a spider in a Newtonian reflector) are attached directly to the rear panel of the scope, the lower secondary being adjusted remotely via the brass thumb screws. With enhanced secondary mirrors and one light bounce for each light path, the scope does much more than a 60 mm refractor monocular and at f/12 provides edge to edge pin point star images. I currently use it on a heavy duty tripod but feel an alt-az mount on a sturdy wood tripod would be better. The right angle view is comfortable horizon to zenith.

The mission was to build a binocular without prisms and with one light bounce for each optical path.

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