Features of the Behavior of Ionospheric Parameters В0 and В1 in the High-Latitude Zone

After treating extraterrestrial and terrestrial solar radiations in the previous chapters, the use of this information in treating an important question regarding the installation of fixed solar systems, namely the tilt and orientation of the solar receivers, becomes possible. There are several rules that guide designers in this field. These rules are called the rules of thumb. There are two rules that are directly related to the subject of this chapter. One of these two rules says that a solar collector should be orientated towards Equator. The other one says that solar collector should have a latitude tilt value. Are these two rules valid all over the world? The present chapter focuses on presenting an algorithm for determining the optimum tilt angle all over the world and for any collector azimuth angle. The Earth surface, located between latitudes 66.45oS and 66.45oN, is divided into 3 characteristic zones. The first zone is the tropical between latitudes 23.45oS and 23.45oN. The second zone is the mid-latitude zone between 23.45oN and 43.45oN and between 23.45oS and 43.45oS. The third zone is the high-latitude zone between 43.45oN and 66.45oN and between 43.45oS and 66.45oS. For each of these zones an adequate method is proposed for calculating the solar collector optimum tilt. Moreover, four simple equations are proposed for predicting daily optimum tilt angle and optimum tilt angle for any number of consecutive days. It is found that the above mentioned rules of thumb are not applicable in the tropical zone while they could be applied with a sufficient accuracy when dealing with fixed installations all over the year in the mid- and high latitude zones.

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Objective-Prism Radial Velocities at High Latitudes

Highlights of Astronomy ◽

10.1017/s1539299600003117 ◽

1977 ◽

Vol 4 (2) ◽

pp. 77-77

Author(s):

J. Stock ◽

W. Osborn ◽

A. R. Upgren

Keyword(s):

Power Series ◽

Spectral Line ◽

High Latitude ◽

Sufficient Accuracy ◽

Radial Velocities ◽

High Latitudes ◽

Proper Motions ◽

Third Order ◽

Latitude Zone ◽

Objective Prism

Stock and Osborn (1972, 1973) have shown that objective-prism spectra taken with a conventional prism may be measured to produce radial velocities of sufficient accuracy for statistical purposes. They are determined by means of a third-order power series in both x and y coordinates. The same spectral-line measures can also yield positions such that proper motions can be determined if first-epoch positions are also available. For many stars, both tangential and radial velocities can be obtained with about the same error which is of the order of ± 20 km/sec. The field distortions caused by the prism are large but are constant and predictable to the degree that measured residuals are similar in size to those for direct images (Stock and Upgren 1968). A survey of a high-latitude zone between −30° and −35° in declination is underway and a catalogue of about 3000 stars has already been compiled by Stock. For each star, the catalogue lists an accurate 1950 position, spectral and luminosity type, apparent photographic magnitude, relative radial velocity and its weight, and the number of plates on which the star was measured.

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