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Solar eclipse of April 29, 1976
An annular solar eclipse occurred at the Moon's descending node of orbit on Thursday, April 29, 1976,[1] with a magnitude of 0.9421. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. An annular solar eclipse occurs when the Moon's apparent diameter is smaller than the Sun's, blocking most of the Sun's light and causing the Sun to look like an annulus (ring). An annular eclipse appears as a partial eclipse over a region of the Earth thousands of kilometres wide. Occurring about 1.9 days after apogee (on April 27, 1976, at 13:30 UTC), the Moon's apparent diameter was smaller.[2] Annularity was visible from North Africa, Greece, Turkey, Middle East, central Asia, India, China. 5 of the 14 eight-thousanders in Pakistan and China—Nanga Parbat, K2, Broad Peak, Gasherbrum II and Gasherbrum I, lie in the path of annularity. A partial eclipse was visible for parts of the Canadian Maritimes, North Africa, Central Africa, Europe, the Middle East, Central Asia, and South Asia. Note that the central line of this annular solar eclipse followed a path extremely similar to that of the total eclipse that will occur 112 years later on April 21, 2088. ObservationThe Institute of Physics and Institute of Mathematics of the Chinese Academy of Sciences and the Xinjiang Earthquake Team conducted observations of gravitational effects using gravimeters, inclinometers, pendulum clocks and seismometers in southwestern Hotan County, Hotan Prefecture, Xinjiang near the Karakoram Pass at an altitude of 5,500 metres (18,000 ft). Results showed that the gravitational acceleration had no obvious effect within the accuracy of the instruments. No inclination was recorded on the photosensitive paper of the inclinometer due to the width of its lines. Three inclinations were pen-recorded, whose time and direction were clearly related to that of the eclipse. Due to the difficult conditions with the high altitude, the observation team was unable to obtain more comparative data.[3] Eclipse detailsShown below are two tables displaying details about this particular solar eclipse. The first table outlines times at which the moon's penumbra or umbra attains the specific parameter, and the second table describes various other parameters pertaining to this eclipse.[4]
Eclipse seasonThis eclipse is part of an eclipse season, a period, roughly every six months, when eclipses occur. Only two (or occasionally three) eclipse seasons occur each year, and each season lasts about 35 days and repeats just short of six months (173 days) later; thus two full eclipse seasons always occur each year. Either two or three eclipses happen each eclipse season. In the sequence below, each eclipse is separated by a fortnight.
Related eclipsesEclipses in 1976
Metonic
Tzolkinex
Half-Saros
Tritos
Solar Saros 128
Inex
Triad
Solar eclipses of 1975–1978This eclipse is a member of a semester series. An eclipse in a semester series of solar eclipses repeats approximately every 177 days and 4 hours (a semester) at alternating nodes of the Moon's orbit.[5]
Saros 128This eclipse is a part of Saros series 128, repeating every 18 years, 11 days, and containing 73 events. The series started with a partial solar eclipse on August 29, 984 AD. It contains total eclipses from May 16, 1417 through June 18, 1471; hybrid eclipses from June 28, 1489 through July 31, 1543; and annular eclipses from August 11, 1561 through July 25, 2120. The series ends at member 73 as a partial eclipse on November 1, 2282. Its eclipses are tabulated in three columns; every third eclipse in the same column is one exeligmos apart, so they all cast shadows over approximately the same parts of the Earth. The longest duration of totality was produced by member 27 at 1 minutes, 45 seconds on June 7, 1453, and the longest duration of annularity was produced by member 48 at 8 minutes, 35 seconds on February 1, 1832. All eclipses in this series occur at the Moon’s descending node of orbit.[6]
Metonic seriesThe metonic series repeats eclipses every 19 years (6939.69 days), lasting about 5 cycles. Eclipses occur in nearly the same calendar date. In addition, the octon subseries repeats 1/5 of that or every 3.8 years (1387.94 days). All eclipses in this table occur at the Moon's descending node.
Tritos seriesThis eclipse is a part of a tritos cycle, repeating at alternating nodes every 135 synodic months (≈ 3986.63 days, or 11 years minus 1 month). Their appearance and longitude are irregular due to a lack of synchronization with the anomalistic month (period of perigee), but groupings of 3 tritos cycles (≈ 33 years minus 3 months) come close (≈ 434.044 anomalistic months), so eclipses are similar in these groupings.
Inex seriesThis eclipse is a part of the long period inex cycle, repeating at alternating nodes, every 358 synodic months (≈ 10,571.95 days, or 29 years minus 20 days). Their appearance and longitude are irregular due to a lack of synchronization with the anomalistic month (period of perigee). However, groupings of 3 inex cycles (≈ 87 years minus 2 months) comes close (≈ 1,151.02 anomalistic months), so eclipses are similar in these groupings.
Notes
References
 Wikimedia Commons has media related to Solar eclipse of 1976 April 29. |
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