The entire frame of the instrument is made of cherry and it will save the builder much time if he will purchase cherry “furniture” which is used by printers and can be obtained from any printers’ supply company.  It is best quality wood free from imperfections in straight strips one yard long and of a uniform width of about 5/8 in.  As to thickness, any multiple of 12-point (about 1/8 in.) may be obtained, thus saving much work in fitting up joints.  Fifty cents will buy enough wood for an entire instrument.  All corners are carefully mortised and braced with small brass angle-pieces.  The frame is held together by small brass machine screws.  After much experimentation with bearings, it was found best to make them in halves as metal bearings are usually made.  The loose half is held in place by guides on all four sides and is tightened by two screws with milled nuts.  A great deal of trouble was experienced in boring out the bearings until the following method was devised.  One hole was bored as well as possible.  The bearing was then loosened and a bit run through it to bore the other.  Finally, a piece of shafting was roughened by rolling it on a file placed in both bearings and turned with a brace.  The bearings were gradually tightened until perfectly ground.

The declination axis must be perpendicular to both the hour axis and the line of sight over the pointer.  To insure this, a positive adjustment was provided.  The end of the shaft is clamped in a short block of wood by means of a bearing like the ones described.  One end of the block is hinged to the axis frame, while the other end is attached by two screws, one drawing them together, the other holding them apart.  The axis is adjusted by turning these screws.  Each shaft, save the one in the pipe, is provided with this adjustment.

The pointer is of two very thin strips placed at right angles and tapered slightly at each end.  The clamp is attached as shown in the illustration.  The eye piece is a black iron washer supported on a small strip of wood.  The aperture should be 1/4 in., since the pupil of the eye dilates very much in darkness.  The error due to large aperture is reduced by using a very long pointer which also makes it possible to focus the eye upon the front sight and the star simultaneously.  The forward sight is a bright brass peg illuminated by a tiny electric lamp with a reflector to shield the eye.  The pointer arranged in this way is a great improvement over the hollow tube sometimes used, since it allows an unobstructed view of the heavens while indicating the exact point in question.

The circles of the instrument are of aluminum, attached to the shafts by means of wooden clamps.  They were nicely graduated by a home-made dividing engine of very simple construction, and the figures were engraved with a pantograph.  The reading is indicated by a cut on a small aluminum plate attached to a pointer.  The hour circle is divided into 24 parts and subdivided to every four minutes.  The figures are arranged so that when the instrument is set up, the number of hours increases while the pointer travels oppositely to the stars.  The declination circle is graduated from zero to 90 deg. in each direction from two points 180 deg. apart.  It is, adjusted to read zero when the pointer and two axes are mutually perpendicular as shown in the picture.