Filar micrometer

Filar micrometer

A filar micrometer is a device used in astronomical telescopes for precision measurements. The word "filar" derives from Latin "filum", a thread. It refers to the fine threads or wires used in the device.

Construction and use

The filar micrometer consists of a micrometer and a reticle that has two fine parallel wires or threads that can be moved by the observer using a screw mechanism. At one time, it was common to use spider silk as a thread. [Berenbaum, May R., "Field Notes - Spin Control", The Sciences, The New York Academy Of Sciences, September/October 1995]

By placing one wire over one object of interest and moving the other to a second object, the distance between the two wires can be measured with the micrometer portion of the instrument. This yields the angular distance between the two objects.

A common use of filar micrometers was measuring the distance between double stars.

Filar micrometers are little used in modern astronomy, having been replaced by newer techniques. However, they are still used in teaching astronomy and by some amateur astronomers.

Prior devices

The precursor to the filar micrometer was the micrometer eyepiece, invented by William Gascoigne.

Earlier measures of angular distances relied on inserting into the eyepiece a thin metal sheet cut in the shape of a narrow, isosceles triangle. The sheet was pushed into the eyepiece until the two adjacent edges of the metal sheet simultaneously occulted the two objects of interest. By carefully measuring the position where the objects were extinguished and knowing the focal length of the eyepiece, the angular distance could be calculated. Christian Huygens used such a device.

References

* George O. Abell, "Exploration of the Universe", fourth edition, Saunders College Publishing, 1982, ISBN 0-03-058502-3


Wikimedia Foundation. 2010.

Игры ⚽ Нужно сделать НИР?

Look at other dictionaries:

  • Filar micrometer — Micrometer Mi*crom e*ter, n. [Micro + meter: cf. F. microm[ e]tre.] An instrument, used with a telescope or microscope, for measuring minute distances, or the apparent diameters of objects which subtend minute angles. The measurement given… …   The Collaborative International Dictionary of English

  • filar micrometer — n an instrument for accurately measuring small distances or angles that usu. consists of two parallel fine platinum wires mounted in the focal plane of a microscope or telescope with one wire being fixed and the other movable by means of a finely …   Medical dictionary

  • filar micrometer — Bifilar Bi*fi lar, a. [Pref. bi + filar.] Two threaded; involving the use of two threads; as, bifilar suspension; a bifilar balance. [1913 Webster] {Bifilar micrometer} (often called {a bifilar}), an instrument form measuring minute distances or… …   The Collaborative International Dictionary of English

  • filar micrometer — siūlinis mikrometras statusas T sritis Standartizacija ir metrologija apibrėžtis Mikrometras, kuriame yra rėmelis su matavimo siūlais. Naudojamas mažiems atstumams matuoti teleskopo židinio plokštumoje. atitikmenys: angl. crossbar micrometer;… …   Penkiakalbis aiškinamasis metrologijos terminų žodynas

  • filar micrometer — siūlinis mikrometras statusas T sritis fizika atitikmenys: angl. crossbar micrometer; filar micrometer vok. Fadenmikrometer, n; Kreuzfadenmikrometer, n rus. нитяной микрометр, m pranc. micromètre à fils, m; micromètre à réticule, m; micromètre… …   Fizikos terminų žodynas

  • filar micrometer — noun : an instrument for accurately measuring small distances or angles usually consisting of two parallel fine platinum wires mounted in the focal plane of a microscope or telescope, one wire being fixed and the other movable by means of a… …   Useful english dictionary

  • Micrometer — Mi*crom e*ter, n. [Micro + meter: cf. F. microm[ e]tre.] An instrument, used with a telescope or microscope, for measuring minute distances, or the apparent diameters of objects which subtend minute angles. The measurement given directly is that… …   The Collaborative International Dictionary of English

  • Micrometer caliper — Micrometer Mi*crom e*ter, n. [Micro + meter: cf. F. microm[ e]tre.] An instrument, used with a telescope or microscope, for measuring minute distances, or the apparent diameters of objects which subtend minute angles. The measurement given… …   The Collaborative International Dictionary of English

  • Micrometer gauge — Micrometer Mi*crom e*ter, n. [Micro + meter: cf. F. microm[ e]tre.] An instrument, used with a telescope or microscope, for measuring minute distances, or the apparent diameters of objects which subtend minute angles. The measurement given… …   The Collaborative International Dictionary of English

  • Micrometer head — Micrometer Mi*crom e*ter, n. [Micro + meter: cf. F. microm[ e]tre.] An instrument, used with a telescope or microscope, for measuring minute distances, or the apparent diameters of objects which subtend minute angles. The measurement given… …   The Collaborative International Dictionary of English

Share the article and excerpts

Direct link
… Do a right-click on the link above
and select “Copy Link”