The later English artists have somewhat changed the mode of communicating motion to the slides, by attaching the screws pdrmanently to the micrometer head and tapping each micrometer screw into its slide.
S is the head of the micrometer screw proper, s that of the screw moving the slide to which the so-called " fixed web " is attached, s' that of a screw which moves the eyepiece E.
The short screw whose divided milled head is shifts the zero of the micrometer by pushing, without turning, the short sliding rod whose flat end forms the point d'appui of the micrometer screw at I.
2940, Dr Repsold proposed a method of meridian observing which consists in causing a web to follow the image of a star in transit by motions communicated by the observer's hands alone, whilst electrical contacts on the drum of the micrometer screw register on the chronograph the instants corresponding to known intervals from the line of collimation.
It should be mentioned that an essential feature of the travelling wire micrometer is that the eyepiece as well as the wire shall be moved by the micrometer-screw.
The plate A i is mounted on the dove-tailed slide B 1, upon the metallic stage T, and can be moved to right or left relative to T by the micrometer-screw S; whilst the plate A2 is mounted on the dove-tailed slide B2 and can From Zeitschr.
The micrometer-screw S has a pitch of 0.5 mm., its head is divided into too parts.
It must be mentioned 4 _ 28 that the pressure of the cushion C on the type-wheels 6 - 30 has no influence whatever upon the micrometer-screw, 7 -32 because the type-wheels are mounted on a hollow cylindrical axis, concentric with the axis of the screw, but entirely disconnected from the screw itself.
Having selected the most suitable one he directs the axis of the finder to the estimated middle point between the comet and the star, turns the finder-micrometer in position angle until the images of comet and star lie symmetrically between the parallel position wires, and then turns the micrometer screw (which moves the distance-wires symmetrically from the centre in opposite directions) till one wire bisects the comet and the other the star.
pp. 199-209) the rays from the object-glass pass successively through lenses as follows: The lens b is divided, and one of the segments is moved by a micrometer screw.
In Scott's sight, mark iv., there is a longitudinal level pivoted at one end and provided with a degree scale up to 4°; the level is moved by a spindle and micrometer screw reading to 2'.
-- The screw is an important productive measuring instrument, whether used as a micrometer-screw of less than an inch in length, or as a master-screw of 20 feet in length.
This in its simplest form consisted of a ring of wire nearly closed terminating in spark balls very close together, adjustable as to distance by a micrometer screw.
The most used is the micrometer screw adjustment (fig, 51).
- Micrometer Screw FIG.
The end of the column C is traversed by the micrometer screw D which is set in action by the knob E.
In other fine adjustments by means of springs and balance wheels either a micrometer screw is moved (Zeiss), or a curved disk fixed to the balance wheel is turned (Leitz), or an oblique disk arranged more or less in a circle and attached to the balance wheel is revolved (Reichert).
eyepiece a slide b can be moved by a micrometer screw a; the slide carries a little glass plate c provided with a graduation.
The dead motion of a micrometer screw is best avoided by working the screw always from one and the same side.
5) the eyepiece can be made to follow the star for a considerable distance along a position-web parallel to the screw, the bisection of the web by a star moving by the diurnal motion at right angles to the micrometer screw can only be followed for a limited distance, viz.
9, are cut on the axis of the micrometer screw.
The pinion z and the toothed wheel d are connected by an intermediate wheel and pinion Y; the numbers of teeth in the wheels and pinions are so proportioned that twenty-four revolutions of the micrometer screw produce one revolution of the drum and wheel d.
Contact of the web-frame of the micrometer with the side of the box at y would therefore take place, were it not for the micrometer screw.
position-angle by the screw K and slow motion in position-angle is given by the screw p. The small drum-head T opposite the micrometer head S turns a screw which acts upon a short cylinder that cannot turn but can move only in the direction of the axis of the micrometer screw.
parts of the micrometer screw in order to eliminate the effects of periodic error of the screw.
The method consisted in having motion transmitted to the micrometer screw from an axis on which is mounted a disk that presses with friction-contact upon a cone that revolves uniformly by clockwork.
The velocity of rotation of the micrometer-screw could therefore be varied for stars of different declination by varying the distance from the apex at which the revolving disk presses upon the revolving cone.
This rod turns a worm-screw which acts on a worm-wheel fitted " spring tight " upon the axis of the micrometer-screw.
In Scott's sight, mark iv., there is a longitudinal level pivoted at one end and provided with a degree scale up to 4Ã‚°; the level is moved by a spindle and micrometer screw reading to 2'.
By directing the telescope to a distant object, or to the intersection of the webs of a fixed collimating telescope (see Transit Circle), it is easy to measure the effect of a small change of zenith distance of the axis of the telescope in terms both of the level and of the micrometer screw, and thus, if the levels are perfectly sensitive and uniform in curvature and graduation, to determine the value of one division of each level in terms of the micrometer screw.
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