A fine and rare English 11/16-inch astronomical telescope
Unsigned, late 17th/early 18th Century, the telescope associated
the 73-inch (185.5cm.) long brass body-tube is in three sections, secured to one another via two brass joining bands each with twelve chessehead screws. The objective lens is in fact a plain glass disc, such as one would expect to find on a sighting level. It is secured in a short threaded section of brass tube arranged to screw into the end of the body tube, with a slightly flared brass ray shade incorporated. The inner edge of the ray shade is threaded for a further attachment. The body tube has two small brass fittings attached and protruding at right angles, each with a small unthreaded hole, perhaps originally for a bubble level. Each has been deeply incised, the forward attachment with a small X, the rearward one with a small V. At the other end of the body tube, a small brass box with a short tube section slides into the aperture at the end of the body tube. This is secured by means of a small retaining screw with a shaped head. The body tube also has a threaded section on the outside at this end, presumably for an alternative eyepiece arrangement, but with the eyepiece box in place, unusable. Within the body tube at this end is a movable lens mounting (with no lens present), adjusted by means of a simple sliding lever on the outside. The brass box itself contains two parallel sighting wires. Beneath the box is a rectangular brass casing for a tangent screw adjustment arrangement which moves the lefthand sighting wire. On the outside of this casing is a small index and an engraved scale 0-40, with one unit subdivisions. The tangent screw is operated by means of a butterfly handled turning screw at the lefthand end of the casing, which incoporates a second index, this time in the form of a hand with pointing finger, arranged to read off a small vertical circle graduated 0-100 around the circumference, with one unit subdivisions. This whole unit is held in place by two lengths of brass screwed to the underside of the box to form two lips over the edge of the plate to which the mechanism is attached, and by a pierced and shaped retaining screw. The box also incorporates a smaller length of tubing (sheared off but retained) into which slides the eyepiece mount with two lenses. The body tube has the appearance of being a later replacement, adapted from a large sighting level. The original telescope would most likely have been a long vellum-bound instrument.
The body tube is attached to the stand by means of two brass collars, each with a shaped retaining screw. These collars are each on a long brass rod which fits through a long horizontal piece of grained mahogany and is secured beneath by a butterfly nut. On the side of this piece are fixed brass-mounted eyepiece and objective sighting lenses. Constructed as an integral part of the mounting is a vertical half-circle of ash beneath the horizontal mahogany section, incorporating a brass declination scale around its half-circumference. This scale is numbered 80-90-0-90-80, with one degree subdivisions, and is labelled appropriately DECLINATIO AUSTRALIS and DECLINATIO SEPTENTRIONALIS. At the centre is a Zodiac scale with sigils and abbreviations for the houses of the Zodiac, Capricorn to Gemini over Sagittarius to Cancer. The lower edge of the half-circle has a racked brass attachment for adjustment via a tangent screw, and the whole mounting section is fixed via a square-headed screw and butterfly nut between two bevelled ash A-frame supports terminating in a round base. One of these supports is pierced to allow a reading off the vertical scale, and a vertical brass wire is fixed in the aperture for an accurate reading. A retaining screw on the other side keeps the vertical half-circle in position, or allows for its adjustment via a rack and pinion arrangment housed in the round base of the A-frame supports. The tangent screw is adjusted via a brass rod with a butterfly nut handle. This is jointed near to the base, but has a threaded collar which can be screwed into place to keep the rod in a horizontal position. Around the circular base of the vertical half-circle mounting is another brass section of racking, for horizontal adjustment of the telescope. This is operated by means of a similar tangent screw arrangment with brass adjustment rod, with a pierced and shaped handle and threaded collar to fix the rod in the horizontal position. The whole telescope mounting is fixed onto a horizontal turned ash cross-beam with tapering ends and shaped brass plaques on either side. One is left blank and the other shows engraved foliate and floral decorations. Stretching directly downwards from this cross-beam is a turned and tapering ash column, with acanthus leaf decoration at the top, and beaded decoration about half way down. This terminates on a 10 inch (25.4cm.) diameter circular ash plate mounted with two silvered and two brass volvelles. As one turns the adjustment rod for horizontal positioning, so the central brass volvelle rotates, at its edge an index to read off three concentric hour scales of, consecutively, I-XII (x2), 1-12 (x2) and again I-XII (x2), each with quarter-hour subdivisions. In addition there is small silvered minute dial off-centre graduated 0-60, numbered every 5 minutes and with one minute subdivisions. The shaped blued-iron needle in the form of an arrow also moves in relation to the horizontal tangent screw adjustment. The scale plate is further supported on either side by two square section grained mahogany supports which are attached via butterfly nuts to the ash cross-beam. The cross-beam itself is mounted at either end on a turned vertical pillar of grained beech, each incorporating a large brass quadrant which extends from the pillar at right angles to the ash cross-beam. Each of these is attached via a brass sleeve mounting and retaining screw to the corresponding square-section support for the scale plate. One of the quadrants is engraved with graduations 5°-105°, numbered every 10° and with ½° subdivisions. By means of these protruding brass quadrant supports, the whole telescope and mounting can be moved through the vertical axis. Between the two main turned upright pillars is a fixed and shaped cross-bar from which hangs a string and plumb weight. The point on the weight corresponds to a small brass plaque with a point on the stepped ash cross-beam base which supports the vertical pillars. There are also two smaller plaques in the shape of arrows, one at either side. Beneath the cross-beam base the vertical pillars continue with flattened bun feet with upside-down finials, a tapering section in the centre of the underside of the cross-beam fitting into a wide baluster turned ash housing on a triform base. The edges of the base are scroll-shaped, with square-section corners, each incoporating a horizontal screw which fits into a later brass foot, with a butterfly wing retaining nut. Each later brass foot has two holes for fixing the whole stand in position via mounting bolts. The underside of the base incoporates two wooden rollers (stiff) which can be used to move the stand if not bolted into place (all brass parts have been polished, with little original lacquer remaining, and areas of plish residue apparent. There is some old worming to the wooden sections, and some sections of the lacquer on the grained sections have chipped off)
59in. (149.9cm.) high