For very accurate measurements micrometer calipers are used.

Micrometer Caliper

For very accurate measurements micrometer calipers are used.

For very accurate measurements vernier calipers are used.

Vernier Caliper

For very accurate measurements vernier calipers are used.

A device for measuring very small distances, objects, or angles, especially one based on the rotation of a finely threaded screw, as in relation to a microscope.

Micrometer Gage

A device for measuring very small distances, objects, or angles, especially one based on the rotation…

"Sir David Gill devised a measuring machine which combines the rapidity of the glass—scale micrometer with the accuracy of the spider—line micrometer and simplifies the reductions of the observations at the same time." —Encyclopaedia Brittannica, 1910

Gill's Measuring Machine for Micrometer

"Sir David Gill devised a measuring machine which combines the rapidity of the glass—scale micrometer…

"The horizontal section in the direction of the axis of the telescope. The eye-piece ab consists of two planoconvex lenses a, b, of nearly the same focal length, and with the two convex sides facing each other. They are placed at a distance apart less than the focal length of a, so that the wires of the micrometer, which must be distinctly seen are beyond b. The eye-piece slides into the tube cd, which screws into the brass ring ef, through two openings in which the oblong frame, containing the micrometer slides, passes." —The Encyclopedia Britannica, 1903

Micrometer

"The horizontal section in the direction of the axis of the telescope. The eye-piece ab consists of…

"The vertical section in the direction of the axis of the telescope. The eye-piece ab consists of two planoconvex lenses a, b, of nearly the same focal length, and with the two convex sides facing each other. They are placed at a distance apart less than the focal length of a, so that the wires of the micrometer, which must be distinctly seen are beyond b. The eye-piece slides into the tube cd, which screws into the brass ring ef, through two openings in which the oblong frame, containing the micrometer slides, passes." —The Encyclopedia Britannica, 1903

Micrometer

"The vertical section in the direction of the axis of the telescope. The eye-piece ab consists of two…

"The original Merz micrometer of the Cape Observatory, made on Fraunhofer's model. 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 eye-piece E. C is the clamp and M the slow motion in position angle, L, L are tubes attached to a larger tube N; the latter fits loosely on a strong hollow cylinder which terminates in the screw V. By this screw the whole apparatus is attached to the telescope." —The Encyclopedia Britannica, 1903

Micrometer

"The original Merz micrometer of the Cape Observatory, made on Fraunhofer's model. S is the head of…

"A plan of this slide; the divided drum of the screw is omitted for sale of clearness. The screw S has a shoulder at k, carefully fitted and ground to a bearing so as to work sweetly in a hole in the very strong spring o o; the other extremity of the screw is formed into a pivot, which fits a hole in the brass piece B B. The end of this pivot—hrdened, polished, and slightly rounded—rests on the flat surface of an agate a, which is imbedded in the end of the slide, and kept firmly in its place by the brass piece B B." —The Encyclopedia Britannica, 1903

Micrometer

"A plan of this slide; the divided drum of the screw is omitted for sale of clearness. The screw S has…

"A plate of glass about 2.5 inches square is ruled with twenty-one lines in one direction .1 inch apart, and two lines in the other direction 2 inches apart. The extreme lines of the set therefore form a perfect square of 2 inches. These lines are ruled with exceeding accuracy and care, but provision is left for ascertaining any errors that remain either as to distance or want of perfect squareness." —The Encyclopedia Britannica, 1903

Micrometer

"A plate of glass about 2.5 inches square is ruled with twenty-one lines in one direction .1 inch apart,…

"a is the sphere, placed in half-holes on the axis bb, so that when its principal axis is parallel to the axis the telescope it gives only one image of the object. In a direction perpendicular to that axis it must be so placed that when it is moved by rotation of the axis bb the separation of the images shall be parallel to that motion. The angle of rotation is measured on the grduated circle C. The angle between the objects measured is = r sin 20, where r is a constant to be determined for each magnifying power employed." —The Encyclopedia Britannica, 1903

Micrometer

"a is the sphere, placed in half-holes on the axis bb, so that when its principal axis is parallel to…

"a is the sphere, placed in half-holes on the axis bb, so that when its principal axis is parallel to the axis the telescope it gives only one image of the object. In a direction perpendicular to that axis it must be so placed that when it is moved by rotation of the axis bb the separation of the images shall be parallel to that motion. The angle of rotation is measured on the grduated circle C. The angle between the objects measured is = r sin 20, where r is a constant to be determined for each magnifying power employed." —The Encyclopedia Britannica, 1903

Micrometer

"a is the sphere, placed in half-holes on the axis bb, so that when its principal axis is parallel to…

"The circles for position angle and declination are read by micrometer microscopes illuminated by the lamp L; the scales are illuminated by the lamp l. T is part of the tube proper and turns with the head. The tube V, on the contrary, is attached to the cradle, and merely forms a support for the finder Q, the handles at f and p, and the moving ring P. The latter gives quick motion in position angle; the handles a p clamp and give slow motion in position angle, those at f clamp and give slow motion in right ascension and declination." —The Encyclopedia Britannica, 1903

Micrometer

"The circles for position angle and declination are read by micrometer microscopes illuminated by the…

Micrometer

Micrometer

Micrometer

This micrometer is composed of a frame, anvil, thimble, and ratchet stop. Used in most mechanical trades for precision measurement. Micrometers use the principle of a screw to amplify small distances that are too small to measure. The accuracy of a micrometer derives from the accuracy of the thread form.

The Precision Micrometer Screw Gauge

This micrometer is composed of a frame, anvil, thimble, and ratchet stop. Used in most mechanical trades…

A Repsolds micrometer used by Cape Observatory. The large micrometer is used to accurately adjust the telescope by series of knobs and screws.

Repsolds Micrometer in Cape Observatory

A Repsolds micrometer used by Cape Observatory. The large micrometer is used to accurately adjust the…

A micrometer with the box removed from Cape Observatory. The device rotates the telescope accurately by turning the wheels. This view of the micrometer is attached to the base.

Repsolds Micrometer with Removed Box Cape Observatory

A micrometer with the box removed from Cape Observatory. The device rotates the telescope accurately…

"Repsolds' more recent form of the spider—line micrometer (since 1893) for large telescope. Quick motion in Position—angle for rough setting or for the measurement of close double stars is given by the large ring R." —Encyclopaedia Britannica, 1910

Repsolds Spider Line Micrometer for Quick Position Angle Motion

"Repsolds' more recent form of the spider—line micrometer (since 1893) for large telescope. Quick…

"Simple microtome for clamping to table. P, P, plate glass ways for the section knife; S, milled-head for clamping the object; M, micrometer milled-head for turning the screw that raises the object as the sections are cur; C, milled-head for clamping the microtome to the table." -Stevens, 1916

Microtome

"Simple microtome for clamping to table. P, P, plate glass ways for the section knife; S, milled-head…

"The eye-end of a telescope. The reader will recognize the micrometer previously described. L is a paraffin lamp fitting by a bayonet joint into a copper cover c. This effectually defends its glass chimney against accident, and protects the lamp from wind. The simple means by which this lamp is made to preserve its verticality in all positions of the telescope is evident from the figure. By this lamp alone the bright wire or bright field illumination is given at pleasure, and with any desired intensity, simply by movement of the small pin p." —The Encyclopedia Britannica, 1903

Telescope

"The eye-end of a telescope. The reader will recognize the micrometer previously described. L is a paraffin…

"The micrometer box, and of course with it the whole system of spider webs, is moved by the screw s, whilst the measuring web is independently moved by the screw S." —Encyclopaedia Brittannica, 1910

Repsolds Micrometer Box for Telescope Cape Observatory

"The micrometer box, and of course with it the whole system of spider webs, is moved by the screw s,…

A Repsolds micrometer box for Yerkes Telescope. The wheels on the sides adjusts the telescope sideways, up, and down accurately.

Repsolds Micrometer Box for Yerkes Telescope

A Repsolds micrometer box for Yerkes Telescope. The wheels on the sides adjusts the telescope sideways,…