scholarly journals Ultraviolet photometry of stars obtained with the Celescope experiment in the Orbiting Astronomical Observatory

1970 ◽  
Vol 36 ◽  
pp. 109-119
Author(s):  
Robert J. Davis
Keyword(s):  
Astronomical Observatory ◽  
Published Data ◽  
The Sun ◽  
The Moon ◽  
Wavelength Band ◽  
Giant Stars ◽  
Outer Atmosphere ◽  
Consistent Picture ◽  
Far Ultraviolet ◽  
Star Fields

We have used the television photometers in the Celescope OAO experiment to measure the far ultraviolet brightnesses of several thousand stars, including parts of the constellations Draco, Lyra, Puppis, Vela, Taurus, and Orion; and the Moon. As of this date (22 July 1969), three of our four cameras continue to operate satisfactorily, and we are making measurements in additional star fields distributed throughout the sky. Our shortest wavelength band, which includes the Lyman α line of atomic hydrogen, provides information on the Earth's outer atmosphere, as well as on star brightnesses. The intensity of the Lyman α radiation from the geocorona is a maximum when the Sun is near the horizon as seen by the OAO, and a minimum when the Sun is in the nadir. The direction that the telescope points does not much affect the measured intensities.Because of the heavy logistic problems of identification, calibration, and measurement for so many stars and because of the survey character of the program, the scientific interpretation of the results is, as expected, lagging the measurement program. However, one consistent picture beginning to emerge from our data is that our observed stars are about equally divided between those that fall within 0.5 magnitude of the predicted ultraviolet brightnesses and those that are significantly fainter than predicted. Most of the giant stars we observe exhibit these ultraviolet deficiencies. Since some of these giants are stars for which little or no interstellar reddening is predicted, we attribute the observed deficiencies to the stars themselves.Many of the objects we observe do not have accurate ground-based published data regarding magnitude, color, and spectral type; new ground-based observations of these objects are required to ensure satisfactory interpretation of our results.

scholarly journals Astronomy at the service of the Islamic society

2009 ◽  
Vol 5 (S260) ◽  
pp. 514-521
Author(s):  
Ilias M. Fernini
Keyword(s):  
Proper Time ◽  
Astronomical Observatory ◽  
The Sun ◽  
The Moon ◽  
Scientific Institutions ◽  
Mathematical Astronomy ◽  
Islamic Empire ◽  
New Moon ◽  
Islamic Society

AbstractThe Islamic society has great ties to astronomy. Its main religious customs (start of the Islamic month, direction of prayer, and the five daily prayers) are all related to two main celestial objects: the Sun and the Moon. First, the start of any Islamic month is related to the actual seeing of the young crescent after the new Moon. Second, the direction of prayer, i.e., praying towards Mecca, is related to the determination of the zenith point in Mecca. Third, the proper time for the five daily prayers is related to the motion of the Sun. Everyone in the society is directly concerned by these customs. This is to say that the major impetus for the growth of Islamic astronomy came from these three main religious observances which presented an assortment of problems in mathematical astronomy. To observe these three customs, a new set of astronomical observations were needed and this helped the development of the Islamic observatory. There is a claim that it was first in Islam that the astronomical observatory came into real existence. The Islamic observatory was a product of needs and values interwoven into the Islamic society and culture. It is also considered as a true representative and an integral par of the Islamic civilisation. Since astronomy interested not only men of science, but also the rulers of the Islamic empire, several observatories have flourished. The observatories of Baghdad, Cairo, Córdoba, Toledo, Maragha, Samarqand and Istanbul acquired a worldwide reputation throughout the centuries. This paper will discuss the two most important observatories (Maragha and Samarqand) in terms of their instruments and discoveries that contributed to the establishment of these scientific institutions.

scholarly journals Alternative explanation of some total so-lar eclipse related phenomena

2017 ◽  
Vol 5 (2) ◽  
pp. 83
Author(s):  
Salah Abunayib
Keyword(s):  
Mirror Image ◽  
The Sun ◽  
The Moon ◽  
Before And After ◽  
Integral Effect ◽  
Edge Surface ◽  
The Face ◽  
Outer Atmosphere ◽  
Peculiar Phenomenon ◽  
Diamond Ring

Diamond ring, shadow bands and coronal heating are some phenomena of great interest to concerned scientists and observers during total eclipse of the sun. These phenomena are explained here in a different way which is simply based on the familiar fact that the sun and the moon are actually spherical objects and not just plane disks. Firstly, the diamond of the diamond ring is seen here as two symmetrical seamless joined halves. One-half is the directly seen single spot of the sun that is uncovered by the moon just at the beginning and end of totality. The other half is a mirror image of that spot reflected by the edge surface of the moon. Secondly, the shadow bands phenomenon is explained as due to interference of light from two seamless joined hair crescents. One is the inner edge of the thin crescent sun that can be seen immediately before and after totality. Light from this inner edge hair crescent falling on the edge surface of the moon gets mirror reflected creating another hair crescent image and both are seamlessly embraced by the main crescent sun. Thirdly, during totality when looking at the outer atmosphere of the sun around its eclipsed face, one is actually looking through a very deep transparent atmosphere of the sun. The viewed depth in the outer atmosphere is geometrically hundreds of times greater than that of the photosphere at the center of the face of the sun. Theoretically, the solar energy gets concentrated by the integral effect of all the points along the viewed depth. This may, hence, stand as one of the factors to be considered in explaining the peculiar phenomenon that the temperature increases as we go away from the surface of the sun.

The Interpretation of Solar Spectral Intensities

1988 ◽  
Vol 102 ◽  
pp. 329
Author(s):  
R.W.P. McWhirter
Keyword(s):  
Emission Measure ◽  
Physical Nature ◽  
Atomic Data ◽  
The Sun ◽  
Atomic Properties ◽  
Outer Atmosphere ◽  
Spectral Intensities ◽  
Thin Plasma ◽  
Number Of Authors

The intensity of a specrtal line from an optically thin plasma such as the outer atmosphere of the sun depends on both the atomic properties of the atomic ion responsible for the line and the physical nature of the plasma. In this paper we discuss the various ways in which the measured spectral intensities from the sun are used to discover something about the nature of the sun’s atmosphere. The technique has been referred to as the emission measure method. It has important limitations in terms of the accuracy of the specrtal data as well as the atomic data. We discuss some of these and suggest methods by which they may be assessed. The technique is illustrated by application to real observations from a number of authors.

Modelling Lunar Extremes

2018 ◽  
Vol 3 (2) ◽  
pp. 207-216 ◽  
Author(s):  
David Fisher ◽  
Lionel Sims
Keyword(s):  
High Precision ◽  
Celestial Mechanics ◽  
Computer Modelling ◽  
Landscape Context ◽  
The Sun ◽  
The Moon

Claims first made over half a century ago that certain prehistoric monuments utilised high-precision alignments on the horizon risings and settings of the Sun and the Moon have recently resurfaced. While archaeoastronomy early on retreated from these claims, as a way to preserve the discipline in an academic boundary dispute, it did so without a rigorous examination of Thom’s concept of a “lunar standstill”. Gough’s uncritical resurrection of Thom’s usage of the term provides a long-overdue opportunity for the discipline to correct this slippage. Gough (2013), in keeping with Thom (1971), claims that certain standing stones and short stone rows point to distant horizon features which allow high-precision alignments on the risings and settings of the Sun and the Moon dating from about 1700 BC. To assist archaeoastronomy in breaking out of its interpretive rut and from “going round in circles” (Ruggles 2011), this paper evaluates the validity of this claim. Through computer modelling, the celestial mechanics of horizon alignments are here explored in their landscape context with a view to testing the very possibility of high-precision alignments to the lunar extremes. It is found that, due to the motion of the Moon on the horizon, only low-precision alignments are feasible, which would seem to indicate that the properties of lunar standstills could not have included high-precision markers for prehistoric megalith builders.

Sweat of the Sun and Tears of the Moon. Gold and Silver in Pre-Columbian Art

1967 ◽  
Vol 71 (2) ◽  
pp. 215
Author(s):  
Earle R. Caley ◽  
Andre Emmerich
Keyword(s):  
The Sun ◽  
The Moon

scholarly journals How dim is dim? Precision of the celestial compass in moonlight and sunlight

2011 ◽  
Vol 366 (1565) ◽  
pp. 697-702 ◽  
Author(s):  
M. Dacke ◽  
M. J. Byrne ◽  
E. Baird ◽  
C. H. Scholtz ◽  
E. J. Warrant
Keyword(s):  
Dung Beetle ◽  
The Sun ◽  
The Moon ◽  
Polarization Pattern ◽  
Animal Group ◽  
Straight Line ◽  
Celestial Orientation ◽  
Polarization Compass ◽  
Celestial Compass ◽  
Diurnal Species

Prominent in the sky, but not visible to humans, is a pattern of polarized skylight formed around both the Sun and the Moon. Dung beetles are, at present, the only animal group known to use the much dimmer polarization pattern formed around the Moon as a compass cue for maintaining travel direction. However, the Moon is not visible every night and the intensity of the celestial polarization pattern gradually declines as the Moon wanes. Therefore, for nocturnal orientation on all moonlit nights, the absolute sensitivity of the dung beetle's polarization detector may limit the precision of this behaviour. To test this, we studied the straight-line foraging behaviour of the nocturnal ball-rolling dung beetle Scarabaeus satyrus to establish when the Moon is too dim—and the polarization pattern too weak—to provide a reliable cue for orientation. Our results show that celestial orientation is as accurate during crescent Moon as it is during full Moon. Moreover, this orientation accuracy is equal to that measured for diurnal species that orient under the 100 million times brighter polarization pattern formed around the Sun. This indicates that, in nocturnal species, the sensitivity of the optical polarization compass can be greatly increased without any loss of precision.

scholarly journals XLIV. Variation of the compass, as observed on board the Endeavour Bark, in a voyage round the World

1771 ◽  
Vol 61 ◽  
pp. 422-432 ◽  
Keyword(s):  
The Sun ◽  
The Moon ◽  
The World

The day of the month is noted according to the nautical account, which therefore in all observations noted P. M. is one day forwarder than the civil account. The latitude in is deduced from the last preceding meridian altitude of the Sun; and the longitude in is corrected by the last observations of the distances of the moon from the Sun and stars.

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