Astrophysics (Index)About

plate measuring machine

(APM, automatic plate measuring machine)
(machine to measure position of images on photographic plates)

The term plate measuring machine has been used for equipment that records information about the content of photographic plates, specifically providing information necessary to determine the celestial coordinates of objects imaged on astronomical photographic plates. The term automatic plate measuring machine (or APM) is used, often for one specific machine that is located at Cambridge University, UK (aka, the Cambridge Automatic Plate Measuring Machine).

The machine must sense the images, by passing light through the plate to/from a known location in relation to the plate (a device called a densitometer), and record that location. Then locations of the imaged objects can be determined from information about the coordinates of the plate's target region of the celestial sphere and through use of measured distances across the plate to recognizable objects of known location.

Such machines have been used to gather data from plates, often decades old, which has been useful regarding astrometry as well as locating galaxies imaged on the plates. The large-scale photographic surveys, such as POSS and the UK Schmidt Survey have been processed in such fashion. Examples of plate measuring machines:


(instrument,astrometry)
Further reading:
https://en.wikipedia.org/wiki/Densitometer
https://en.wikipedia.org/wiki/Astrometry
http://ui.adsabs.harvard.edu/abs/1984NASCP2317..277K/abstract
https://www.ast.cam.ac.uk/~mike/casu/apm/apm.html
http://sundog.stsci.edu/first/APM/HTML/node3.html
https://ui.adsabs.harvard.edu/abs/2008PASP..120..644Z/abstract
https://ui.adsabs.harvard.edu/abs/1994AAS...184.2701L/abstract
https://ui.adsabs.harvard.edu/abs/1994AAS...184.3501L/abstract

Referenced by pages:
APM Galaxy Survey (APMUKS)
Large Bright QSO Survey (LBQS)
rare designator prefixes

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