heliograph

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heliograph

(hē`lēəgrăf) [Gr.,=sun-writer], signaling device using flashes of sunlight. It has two mirrors that are used to reflect sunlight on a distant point and a shutter through which the sunlight passes so that messages may be transmitted in telegraphic code by means of long and short flashes. It was used in ancient times and as recently as the 19th cent. by the U.S. army in the SW United States and by the British army in India.
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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Heliograph

 

(1) In meteorology, an instrument for automatically registering the duration of sunshine, that is, the time when the sun is above the horizon and not covered by clouds. There are many types of heliographs. The most widespread in the USSR is the Campbell-Stokes heliograph, in which a stationary sphere serves as a lens that gathers the rays of the sun onto a cardboard strip marked off by hour lines. The strip is burned through by the sun’s rays if irradiation exceeds 0.3 to 0.4 calories per sq cm per min. Because of the apparent daily motion of the sun, the burn is in the form of a line, the length of which serves to measure the duration of the sunshine. A continuously registering actinograph can also function as a heliograph.

REFERENCE

Sternzat, M. S. Meteorologicheskie pribory i nabliudeniia. Leningrad, 1968. Page 209.
(2) In astronomy, a telescope adapted for photographing the sun. It is used to obtain photographs of all or part of the solar disk in a wide range of wave lengths. A heliograph can be used in combination with a coelostat. Because of the tremendous illumination generated by the sun, the aperture ratio of the heliograph objective can be minimal. In order to obtain pictures of the sun with large linear dimensions, as large a focal length is chosen for the heliograph as possible. At the same time, so as not to increase the size of the instrument, additional magnification systems are used. The heliograph is equipped with a fast-action shutter (usually of the curtain type), giving exposure times of from 0.02 to 0.001 seconds. One of the first heliographs was installed by the Russian astrophysicist M. M. Gusev at Wilno (Vilnius) in 1854.
(3) In military affairs in the 19th and early 20th centuries, a light-signaling device for transmitting messages (by Morse code) with a mirror used to reflect light rays. The heliograph is effective over distances of 18 to 40 km in daytime and 3 to 8 km at night.
The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

heliograph

[′hē·lē·ə‚graf]
(communications)
An instrument for sending telegraphic messages by reflecting the sun's rays from a mirror.
(engineering)
An instrument that records the duration of sunshine and gives a qualitative measure of its amount by action of sun's rays on blueprint paper.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

heliograph

1. an instrument with mirrors and a shutter used for sending messages in Morse code by reflecting the sun's rays
2. a device used to photograph the sun
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
References in periodicals archive ?
There are 70 communications transmitters on Heliographic Peak; six campgrounds, 94 cabins, two artificial lakes, one Bible camp, and sundry other uses spread over 201,000 acres.
"I've been trying to locate (without success) a program which will calculate and depict the heliographic coordinates for the sun for any given date and time, in order to allow me to plot sunspots." He continues that just being able to print the grid would suffice, but if he could plot the spots on screen, even better!
At the same time, the designer was also tempted by the visual identity of Heliographic patterns.
The General Egyptian Authority for Books is organizing a workshop to teach Heliographic for children and a seminar by a variety of poets including prominent author Youssef Idris at the Book Fair in Faisal district.
Not only is this technique very convenient and eminently safe, it is also the most reliable way to obtain the heliographic coordinates of sunspots with precision.
The interest and value of your solar records will be greatly increased if you can determine the true heliographic positions of the plotted surface features.
All that remains is to add or subtract the number of degrees that a spot is west or east of the central meridian, and you will have the true heliographic longitude of the spot.
For example, there are extensive discussions of heliographic coordinates as well as the ways of determining positions and measuring motions, some of which are probably unknown to many professional astronomers.
The largest member exhibited a well-defined penumbra, and the whole complex spanned 9 [degrees] of heliographic longitude.
The magnetic and heliographic equators (the latter being perpendicular to the Sun's rotation axis) lie very close together on this imaginary surface at sunspot minimum, when the magnetic field close to the photosplere resembles a simple dipole.
Recently, however, researchers at Stanford University's Wilcox Solar Observatory, and a group of Alaskan and Japanese scientists (including the author), independently found that the Sun's magnetic equator begins to incline with respect to the heliographic equator as the sunspot cycle progresses.