How to use Heliometer in a sentence
The present writer has successfully used a similar plan in measuring position angles of a Centauri with the heliometer, viz.
Again, in an ocular heliometer by Steinheil double image is similarly produced by a divided prism of total reflection placed in parallel rays.
Better determinations of the actual value came from the heliometer, and gave an angular diameter of 31' 59.26" =0.10", and the value of the polar diameter exceeded the equatorial by 0.038" =0.023".
One was to use a heliometer to measure the distance between the limbs of Venus and the sun during the whole time that the planet was seen projected on the solar disk, and the other was to take photographs of the sun during the period of the transit and subsequently measure the negatives.
To remedy drawback (2) Repsolds provided for the Yale heliometer an additional handle for motion in position angle, intermediate in velocity between the original quick and slow motions.Advertisement
This ring runs between friction wheels and is provided with teeth on its inner periphery, and these teeth transmit motion to a pinion on a spindle having at its other end another pinion which, through an intermediate wheel, rotates the heliometer tube.
The reading of the positioncircle of the finder is then the reading to which the position-circle of the heliometer should be set, and from the readings of the micrometerscrew he finds, by a convenient table, the proper settings of the heliometer scales in distance.
When the scales and position-circle of the heliometer have been set to these readings, the comet and the selected comparison-star appear together in the field of view.
Still more recently the Repsolds have completed a new heliometer for Yale College, New Haven, United States.
When the heliometer-part of Lord Lindsay's heliometer was acquired by Gill in 1879, he changed the manner of imparting the motion in question.Advertisement
A series of observations can be easily and more accurately accomplished with the Cape heliometer in half an hour; with the Oxford heliometer it would occupy 2 hours, and with the 4-in.
Heliometer observations of distance in their most refined sense cannot be considered absolute measures of angles.
Thus, for refined purposes, it cannot be assumed with any certainty that the instantaneous scale-value of the heliometer is known, or that it is a function of the temperature.
Gill introduced a powerful auxiliary to the accuracy of heliometer measures in the shape of a reversing prism placed in front of the eye-piece, between the latter and the observer's eye.
The measures were made with the Cape heliometer and have never been superseded, for the latest results with the minor planet Eros exactly confirm Gill's result-8.80" - while they decidedly diminish the associated probable error.Advertisement
Sir David Gill derived a highly satisfactory value of 8.78" for the long-sought constant from the opposition of Mars in 1877, and from combined heliometer observations at five observatories in 1888-1889 of the minor planets Iris, Victoria and Sappho, the apparently definitive value of 8.80" (equivalent distance, 92,874,000 m.).
The Germans laid the greatest stress on measures with the heliometer; the Americans, English, and French on the photographic method.
Had the internal contacts alone been used, which many astronomers would have considered the proper course, the result would have been 8.776" In 1877 Sir David Gill organized an expedition to the island of Ascension to observe the parallax of Mars with the heliometer.
Bouguer's heliometer was in fact similar to that of Savary's third model, with the important difference that, instead of both object-glasses being fixed, one of them is movable by a screw provided with a divided head.
Dollond adds his opinion that the third type is " much the best and most convenient of the three "; yet it is the first type that has survived the test of time and experience, and which is in fact the modern heliometer.Advertisement
Nor is it difficult to imagine the probable course of reasoning which led Bessel to select the model of his new heliometer.
In 1824 the great Konigsberg heliometer was commenced, and it was completed in 1829.
To sum up briefly the history of the development of the heliometer.
The Konigsberg heliometer is represented in fig.
There are three methods in which this heliometer can be used.Advertisement
On the other hand it is not necessary to reset the telescope after each reversal of the segments.4 When Bessel ordered the Konigsberg heliometer, he was anxious to have the segments made to move in cylindrical slides, of which the radius should be equal to the focal length of the object-glass.
He actually introduced them in the Konigsberg heliometer in 1840, and they were renewed in 1848 and 1850.
Bessel, having been consulted by the celebrated statesman, Sir Robert Peel, on behalf of the Radcliffe trustees, as to what instrument, added to the Radcliffe Observatory, would probably most promote the advancement of astronomy, strongly advised the selection of a heliometer.
This instrument suggested to Struve the abovementioned idea of employing a similar motion for the heliometer.
About 1840 a great advance was made by the Repsolds of Hamburg in the equatorial mounting of the Oxford heliometer.Advertisement
Bessel in the years 1837-1840, using a heliometer.
Apart from the large scope of his activity, he introduced such important novelties as the effective use of the heliometer, the correction for personal equation (in 1823), and the systematic investigation of instrumental errors.
Now measures made by Auwers with the Cape heliometer showed no difference, amounting to o I ", and so far negative the idea that the rays reach us after issuing from a level where is sensibly different from unity.
But when the relative positions of two adjacent objects or scaledivisions have to be determined (as, for example, in the case of heliometer scales), much time is saved by retaining the motion of the micrometer box.
He was the inventor of the stage-micrometer, and of a form of heliometer; and in 1816 he succeeded in constructing for the microscope achromatic glasses of long focus, consisting of a single lens, the constituent glasses of which were in juxtaposition, but not cemented together.Advertisement
No auxiliary filar micrometer was required, as in Savary's heliometer, to measure the interval between the limbs of two adjacent images of the sun, it being only necessary to turn the screw with the divided head to change the distance between the object-glasses till the two images of the sun are in contact as in fig.
But, as it came from the hands of the makers in 1849, the Oxford heliometer was incomparably the most powerful and perfect instrument in the world for the highest order of micrometric research.
The inventor claimed that it would supersede the heliometer, but it has never done anything for astronomy.
This particular instrument has historical interest, having led Struve to some of those criticisms of the Pulkowa heliometer which ultimately bore such valuable fruit (see ante).
He also invented a heliometer, afterwards perfected by Fraunhofer.Advertisement
To Fraunhofer, some time not long previous to 1820, is due, so far as we can ascertain, the construction of the first heliometer with an achromatic divided object-glass, i.e.
It is probable that the Bonn heliometer was in course of construction before these suggestions of Struve were published or discussed, since its construction resembles that of the Konigsberg and Pulkowa instruments.
As the transit of Venus of 1874 approached, prepara tions were set on foot by the German Government in good time; a commission of the most celebrated astronomers was appointed, and it was resolved that the heliometer should be the instrument chiefly relied on.
A similar heliometer was made by the Repsolds to the order of Lord Lindsay for his Mauritius expedition in 1874.
This lens is divided and mounted like a heliometer objectglass; the separation of the lenses produces the required double image, and is measured by a screw.Advertisement