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100-561: Gerard de Vaucouleurs was born on April 25, 1918 in Paris, he took the maiden name of his mother as his last name. He had an early interest in amateur astronomy and received his undergraduate degree in 1939 at the Sorbonne in that city. After military service in World War II, he resumed his pursuit of astronomy. He was married to fellow astronomer Antoinette de Vaucouleurs on October 31, 1944, and

200-657: A battle between the Medes and the Lydians . Both sides put down their weapons and declared peace as a result of the eclipse. The exact eclipse involved remains uncertain, although the issue has been studied by hundreds of ancient and modern authorities. One likely candidate took place on May 28, 585 BC, probably near the Halys river in Asia Minor . An eclipse recorded by Herodotus before Xerxes departed for his expedition against Greece , which

300-425: A celestial object in a telescope equipped with a DSC computer, one does not need to look up the specific RA and Dec coordinates in a book or other resource, and then adjust the telescope to those numerical readings. Rather, the object is chosen from the electronic database, which causes distance values and arrow markers to appear in the display that indicate the distance and direction to move the telescope. The telescope

400-472: A few specific techniques. Star hopping is a method often used by amateur astronomers with low-tech equipment such as binoculars or a manually driven telescope. It involves the use of maps (or memory) to locate known landmark stars, and "hopping" between them, often with the aid of a finderscope . Because of its simplicity, star hopping is a very common method for finding objects that are close to naked-eye stars. More advanced methods of locating objects in

500-540: A fortuitous combination of circumstances. Even on Earth, the diversity of eclipses familiar to people today is a temporary (on a geological time scale) phenomenon. Hundreds of millions of years in the past, the Moon was closer to Earth and therefore apparently larger, so every solar eclipse was total or partial, and there were no annular eclipses. Due to tidal acceleration , the orbit of the Moon around Earth becomes approximately 3.8 cm more distant each year. Millions of years in

600-400: A high degree of experience in astronomy and may often assist and work alongside professional astronomers. Many astronomers have studied the sky throughout history in an amateur framework; however, since the beginning of the twentieth century, professional astronomy has become an activity clearly distinguished from amateur astronomy and associated activities. Amateur astronomers typically view

700-508: A longer lens is needed (over 500 mm). As with viewing the Sun directly, looking at it through the optical viewfinder of a camera can produce damage to the retina, so care is recommended. Solar filters are required for digital photography even if an optical viewfinder is not used. Using a camera's live view feature or an electronic viewfinder is safe for the human eye, but the Sun's rays could potentially irreparably damage digital image sensors unless

800-454: A maximum of a few minutes at any location because the Moon's umbra moves eastward at over 1700 km/h (1100 mph; 470 m/s; 1500 ft/s). Totality currently can never last more than 7 min 32 s. This value changes over the millennia and is currently decreasing. By the 8th millennium, the longest theoretically possible total eclipse will be less than 7 min 2 s. The last time an eclipse longer than 7 minutes occurred

900-608: A method he called "spreading the risks." During the 1950s he promoted the idea that galactic clusters are grouped into superclusters. The de Vaucouleurs modified Hubble sequence is a widely used variant of the standard Hubble sequence . De Vaucouleurs was awarded the Henry Norris Russell Lectureship by the American Astronomical Society in 1988. He was awarded the Prix Jules Janssen of

1000-536: A more precise alignment between the centers of the Sun and Moon , and because the Moon's apparent size in the sky is sometimes too small to fully cover the Sun. An eclipse is a natural phenomenon . In some ancient and modern cultures, solar eclipses were attributed to supernatural causes or regarded as bad omens . Astronomers' predictions of eclipses began in China as early as the 4th century BC; eclipses hundreds of years into

1100-590: A partial eclipse at the opposite polar region. A saros series lasts 1226 to 1550 years and 69 to 87 eclipses, with about 40 to 60 of them being central. Between two and five solar eclipses occur every year, with at least one per eclipse season . Since the Gregorian calendar was instituted in 1582, years that have had five solar eclipses were 1693, 1758, 1805, 1823, 1870, and 1935. The next occurrence will be 2206. On average, there are about 240 solar eclipses each century. Total solar eclipses are seen on Earth because of

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1200-420: A practically identical eclipse will occur. The most notable difference will be a westward shift of about 120° in longitude (due to the 0.3 days) and a little in latitude (north-south for odd-numbered cycles, the reverse for even-numbered ones). A saros series always starts with a partial eclipse near one of Earth's polar regions, then shifts over the globe through a series of annular or total eclipses, and ends with

1300-442: A scientific conference or convention. They may also have sections devoted to particular topics, such as lunar observation or amateur telescope making . There have been many significant scientific, technological, and cultural contributions made by amateur astronomers: Amateur astronomers and other non-professionals make contributions through ongoing citizen science projects: Solar eclipse A solar eclipse occurs when

1400-422: A small local society located in dark countryside may focus on practical observing and star parties , whereas a large one based in a major city might have numerous members but be limited by light pollution and thus hold regular indoor meetings with guest speakers instead. Major national or international societies generally publish their own academic journal or newsletter, and some hold large multi-day meetings akin to

1500-455: A solar eclipse was taken on July 28, 1851, by Johann Julius Friedrich Berkowski , using the daguerreotype process. Photographing an eclipse is possible with fairly common camera equipment. In order for the disk of the Sun/Moon to be easily visible, a fairly high magnification long focus lens is needed (at least 200 mm for a 35 mm camera), and for the disk to fill most of the frame,

1600-826: A telescope a great distance away in a dark location. The observer can image through the telescope using CCD cameras. The digital data collected by the telescope is then transmitted and displayed to the user by means of the Internet. An example of a digital remote telescope operation for public use via the Internet is the Bareket observatory , and there are telescope farms in New Mexico, Australia and Atacama in Chile. Amateur astronomers engage in many imaging techniques including film, DSLR , LRGB , and CCD astrophotography . Because CCD imagers are linear, image processing may be used to subtract away

1700-501: A total eclipse and only very briefly; it does not occur during a partial or annular eclipse). Viewing the Sun's disk through any kind of optical aid (binoculars, a telescope, or even an optical camera viewfinder) is extremely hazardous and can cause irreversible eye damage within a fraction of a second. Viewing the Sun during partial and annular eclipses (and during total eclipses outside the brief period of totality) requires special eye protection, or indirect viewing methods if eye damage

1800-420: A total eclipse occurs. The Moon orbits Earth in approximately 27.3 days, relative to a fixed frame of reference . This is known as the sidereal month . However, during one sidereal month, Earth has revolved part way around the Sun, making the average time between one new moon and the next longer than the sidereal month: it is approximately 29.5 days. This is known as the synodic month and corresponds to what

1900-481: A total solar eclipse was made in France in 1706. Nine years later, English astronomer Edmund Halley accurately predicted and observed the solar eclipse of May 3, 1715 . By the mid-19th century, scientific understanding of the Sun was improving through observations of the Sun's corona during solar eclipses. The corona was identified as part of the Sun's atmosphere in 1842 , and the first photograph (or daguerreotype ) of

2000-439: A year, when the Sun and Moon are not exactly in line with Earth and the Moon only partially obscures the Sun. This phenomenon can usually be seen from a large part of Earth outside of the track of an annular or total eclipse. However, some eclipses can be seen only as a partial eclipse, because the umbra passes above Earth's polar regions and never intersects Earth's surface. Partial eclipses are virtually unnoticeable in terms of

2100-424: Is a way for the hobby lovers to share their new sightings and experiences. The popularity of imaging among amateurs has led to large numbers of web sites being written by individuals about their images and equipment. Much of the social interaction of amateur astronomy occurs on mailing lists or discussion groups. Discussion group servers host numerous astronomy lists. A great deal of the commerce of amateur astronomy,

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2200-461: Is about 400 times the Moon's distance, and the Sun's diameter is about 400 times the Moon's diameter. Because these ratios are approximately the same, the Sun and the Moon as seen from Earth appear to be approximately the same size: about 0.5 degree of arc in angular measure. The Moon's orbit around Earth is slightly elliptical , as is Earth's orbit around the Sun. The apparent sizes of the Sun and Moon therefore vary. The magnitude of an eclipse

2300-416: Is commonly called the lunar month . The Moon crosses from south to north of the ecliptic at its ascending node , and vice versa at its descending node. However, the nodes of the Moon's orbit are gradually moving in a retrograde motion , due to the action of the Sun's gravity on the Moon's motion, and they make a complete circuit every 18.6 years. This regression means that the time between each passage of

2400-466: Is moved until the two angular distance values reach zero, indicating that the telescope is properly aligned. When both the RA and Dec axes are thus "zeroed out", the object should be in the eyepiece. Many DSCs, like go-to systems, can also work in conjunction with laptop sky programs. Computerized systems provide the further advantage of computing coordinate precession. Traditional printed sources are subtitled by

2500-448: Is no warning that injury is occurring. Under normal conditions, the Sun is so bright that it is difficult to stare at it directly. However, during an eclipse, with so much of the Sun covered, it is easier and more tempting to stare at it. Looking at the Sun during an eclipse is as dangerous as looking at it outside an eclipse, except during the brief period of totality, when the Sun's disk is completely covered (totality occurs only during

2600-409: Is one such example. Amateur astronomers use a range of instruments to study the sky, depending on a combination of their interests and resources. Methods include simply looking at the night sky with the naked eye, using binoculars, and using a variety of optical telescopes of varying power and quality, as well as additional sophisticated equipment, such as cameras, to study light from the sky in both

2700-496: Is possible for amateurs to see them. There are a large number of amateur astronomical societies around the world, that serve as a meeting point for those interested in amateur astronomy. Members range from active observers with their own equipment to "armchair astronomers" who are simply interested in the topic. Societies range widely in their goals and activities, which may depend on a variety of factors such as geographic spread, local circumstances, size, and membership. For example,

2800-610: Is searching for overlooked phenomena (e.g., Kreutz Sungrazers ) in the vast libraries of digital images and other data captured by Earth and space based observatories, much of which is available over the Internet. In the past and present, amateur astronomers have played a major role in discovering new comets . Recently however, funding of projects such as the Lincoln Near-Earth Asteroid Research and Near Earth Asteroid Tracking projects has meant that most comets are now discovered by automated systems long before it

2900-605: Is sometimes promoted as one of the few remaining sciences for which amateurs can still contribute useful data. To recognize this, the Astronomical Society of the Pacific annually gives Amateur Achievement Awards for significant contributions to astronomy by amateurs. The majority of scientific contributions by amateur astronomers are in the area of data collection. In particular, this applies where large numbers of amateur astronomers with small telescopes are more effective than

3000-467: Is that of archaeologist Bruce Masse, who putatively links an eclipse that occurred on May 10, 2807, BC with a possible meteor impact in the Indian Ocean on the basis of several ancient flood myths that mention a total solar eclipse. Eclipses have been interpreted as omens , or portents. The ancient Greek historian Herodotus wrote that Thales of Miletus predicted an eclipse that occurred during

3100-435: Is the ratio of the apparent size of the Moon to the apparent size of the Sun during an eclipse. An eclipse that occurs when the Moon is near its closest distance to Earth ( i.e., near its perigee ) can be a total eclipse because the Moon will appear to be large enough to completely cover the Sun's bright disk or photosphere ; a total eclipse has a magnitude greater than or equal to 1.000. Conversely, an eclipse that occurs when

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3200-455: Is this effect that leads to the difference between total and annular eclipses. The distance of Earth from the Sun also varies during the year, but this is a smaller effect (by up to about 0.85% from its average value). On average, the Moon appears to be slightly (2.1%) smaller than the Sun as seen from Earth, so the majority (about 60%) of central eclipses are annular. It is only when the Moon is closer to Earth than average (near its perigee ) that

3300-481: Is to be avoided. The Sun's disk can be viewed using appropriate filtration to block the harmful part of the Sun's radiation. Sunglasses do not make viewing the Sun safe. Only properly designed and certified solar filters should be used for direct viewing of the Sun's disk. Especially, self-made filters using common objects such as a floppy disk removed from its case, a Compact Disc , a black colour slide film, smoked glass, etc. must be avoided. The safest way to view

3400-467: Is traditionally dated to 480 BC, was matched by John Russell Hind to an annular eclipse of the Sun at Sardis on February 17, 478 BC. Alternatively, a partial eclipse was visible from Persia on October 2, 480 BC. Herodotus also reports a solar eclipse at Sparta during the Second Persian invasion of Greece . The date of the eclipse (August 1, 477 BC) does not match exactly the conventional dates for

3500-460: The epoch year , which refers to the positions of celestial objects at a given time to the nearest year (e.g., J2005, J2007). Most such printed sources have been updated for intervals of only about every fifty years (e.g., J1900, J1950, J2000). Computerized sources, on the other hand, are able to calculate the right ascension and declination of the "epoch of date" to the exact instant of observation. GOTO telescopes have become more popular since

3600-399: The 2023 April 20 hybrid eclipse 's totality is over a minute in duration at various points along the path of totality. Like a focal point , the width and duration of totality and annularity are near zero at the points where the changes between the two occur. Central eclipse is often used as a generic term for a total, annular, or hybrid eclipse. This is, however, not completely correct:

3700-454: The Moon or asteroids , or by discovering transient astronomical events , such as comets , galactic novae or supernovae in other galaxies . Amateur astronomers do not use the field of astronomy as their primary source of income or support, and usually have no professional degree in astrophysics or advanced academic training in the subject. Most amateurs are hobbyists, while others have

3800-442: The Moon passes between Earth and the Sun , thereby obscuring the view of the Sun from a small part of Earth, totally or partially. Such an alignment occurs approximately every six months, during the eclipse season in its new moon phase, when the Moon's orbital plane is closest to the plane of Earth's orbit . In a total eclipse , the disk of the Sun is fully obscured by the Moon. In partial and annular eclipses , only part of

3900-720: The Société astronomique de France (Astronomical Society of France) in the same year. He and his wife and longtime collaborator, Antoinette, together produced 400 research and technical papers, 20 books and 100 articles for laymen. Amateur astronomy Amateur astronomy is a hobby where participants enjoy observing or imaging celestial objects in the sky using the unaided eye , binoculars , or telescopes . Even though scientific research may not be their primary goal, some amateur astronomers make contributions in doing citizen science , such as by monitoring variable stars , double stars , sunspots , or occultations of stars by

4000-438: The darkness described at Jesus's crucifixion was a solar eclipse. This research has not yielded conclusive results, and Good Friday is recorded as being at Passover , which is held at the time of a full moon. Further, the darkness lasted from the sixth hour to the ninth, or three hours, which is much, much longer than the eight-minute upper limit for any solar eclipse's totality. Contemporary chronicles wrote about an eclipse at

4100-468: The 1980s as technology has improved and prices have been reduced. With these computer-driven telescopes, the user typically enters the name of the item of interest and the mechanics of the telescope point the telescope towards that item automatically. They have several notable advantages for amateur astronomers intent on research. For example, GOTO telescopes tend to be faster for locating items of interest than star hopping, allowing more time for studying of

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4200-454: The Equator, but as the Moon is moving in the same direction as Earth's rotation at about 61 km/min, the umbra almost always appears to move in a roughly west–east direction across a map of Earth at the speed of the Moon's orbital velocity minus Earth's rotational velocity. The width of the track of a central eclipse varies according to the relative apparent diameters of the Sun and Moon. In

4300-399: The Moon is near its farthest distance from Earth ( i.e., near its apogee ) can be only an annular eclipse because the Moon will appear to be slightly smaller than the Sun; the magnitude of an annular eclipse is less than 1. Because Earth's orbit around the Sun is also elliptical, Earth's distance from the Sun similarly varies throughout the year. This affects the apparent size of the Sun in

4400-415: The Moon through the ascending node is slightly shorter than the sidereal month. This period is called the nodical or draconic month . Finally, the Moon's perigee is moving forwards or precessing in its orbit and makes a complete circuit in 8.85 years. The time between one perigee and the next is slightly longer than the sidereal month and known as the anomalistic month . The Moon's orbit intersects with

4500-402: The Sun (the bright disk of the Sun itself), even for just a few seconds, can cause permanent damage to the retina of the eye, because of the intense visible and invisible radiation that the photosphere emits. This damage can result in impairment of vision, up to and including blindness . The retina has no sensitivity to pain, and the effects of retinal damage may not appear for hours, so there

4600-402: The Sun is obscured, then an effect can be observed by which the daylight appears to be dim, as if the sky were overcast, yet objects still cast sharp shadows. When the shrinking visible part of the photosphere becomes very small, Baily's beads will occur. These are caused by the sunlight still being able to reach Earth through lunar valleys. Totality then begins with the diamond ring effect ,

4700-400: The Sun is obscured. Unlike a lunar eclipse , which may be viewed from anywhere on the night side of Earth, a solar eclipse can only be viewed from a relatively small area of the world. As such, although total solar eclipses occur somewhere on Earth every 18 months on average, they recur at any given place only once every 360 to 410 years. If the Moon were in a perfectly circular orbit and in

4800-403: The Sun is within about 15 to 18 degrees of a node, (10 to 12 degrees for central eclipses). This is referred to as an eclipse limit, and is given in ranges because the apparent sizes and speeds of the Sun and Moon vary throughout the year. In the time it takes for the Moon to return to a node (draconic month), the apparent position of the Sun has moved about 29 degrees, relative to the nodes. Since

4900-439: The Sun's brightness, as it takes well over 90% coverage to notice any darkening at all. Even at 99%, it would be no darker than civil twilight . A hybrid eclipse (also called annular/total eclipse) shifts between a total and annular eclipse. At certain points on the surface of Earth, it appears as a total eclipse, whereas at other points it appears as annular. Hybrid eclipses are comparatively rare. A hybrid eclipse occurs when

5000-513: The Sun's disk is by indirect projection. This can be done by projecting an image of the disk onto a white piece of paper or card using a pair of binoculars (with one of the lenses covered), a telescope, or another piece of cardboard with a small hole in it (about 1 mm diameter), often called a pinhole camera . The projected image of the Sun can then be safely viewed; this technique can be used to observe sunspots , as well as eclipses. Care must be taken, however, to ensure that no one looks through

5100-415: The alignment process of telescopes. Setting circles are angular measurement scales that can be placed on the two main rotation axes of some telescopes. Since the widespread adoption of digital setting circles, any classical engraved setting circle is now specifically identified as an "analog setting circle" (ASC). By knowing the coordinates of an object (usually given in equatorial coordinates ),

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5200-478: The apparent size of the Moon is not large enough to completely block out the Sun. Totality thus does not occur; the Sun instead appears as a very bright ring, or annulus , surrounding the dark disk of the Moon. Annular eclipses occur once every one or two years, not annually. The term derives from the Latin root word anulus , meaning "ring", rather than annus , for "year". A partial eclipse occurs about twice

5300-571: The beginning of May 664 that coincided with the beginning of the plague of 664 in the British isles. In the Western hemisphere, there are few reliable records of eclipses before AD 800, until the advent of Arab and monastic observations in the early medieval period. A solar eclipse took place on January 27, 632 over Arabia during Muhammad 's lifetime. Muhammad denied the eclipse had anything to do with his son dying earlier that day, saying "The sun and

5400-524: The buying and selling of equipment, occurs online. Many amateurs use online tools to plan their nightly observing sessions, using tools such as the Clear Sky Chart . While a number of interesting celestial objects are readily identified by the naked eye, sometimes with the aid of a star chart, many others are so faint or inconspicuous that technical means are necessary to locate them. Although many methods are used in amateur astronomy, most are variations of

5500-673: The couple would frequently collaborate on astronomical research. He was fluent in English and spent 1949-51 in England and 1951–57 in Australia at Mount Stromlo Observatory . He was at Lowell Observatory in Arizona from 1957-1958 and at Harvard from 1958-60. In 1960 he was appointed to the University of Texas at Austin , where he spent the rest of his career. He was one of the first five faculty in

5600-415: The dark silhouette of the Moon completely obscures the bright light of the Sun, allowing the much fainter solar corona to be visible. During an eclipse, totality occurs only along a narrow track on the surface of Earth. This narrow track is called the path of totality. An annular eclipse, like a total eclipse, occurs when the Sun and Moon are exactly in line with Earth. During an annular eclipse, however,

5700-439: The definition of a central eclipse is an eclipse during which the central line of the umbra touches Earth's surface. It is possible, though extremely rare, that part of the umbra intersects with Earth (thus creating an annular or total eclipse), but not its central line. This is then called a non-central total or annular eclipse. Gamma is a measure of how centrally the shadow strikes. The last (umbral yet) non-central solar eclipse

5800-457: The duration of a total solar eclipse (in order of decreasing importance): The longest eclipse that has been calculated thus far is the eclipse of July 16, 2186 (with a maximum duration of 7 minutes 29 seconds over northern Guyana). A total solar eclipse is a rare event, recurring somewhere on Earth every 18 months on average, yet is estimated to recur at any given location only every 360–410 years on average. The total eclipse lasts for only

5900-459: The eclipse circumstances will be at any given location. Calculations with Besselian elements can determine the exact shape of the umbra's shadow on Earth's surface. But at what longitudes on Earth's surface the shadow will fall, is a function of Earth's rotation, and on how much that rotation has slowed down over time. A number called ΔT is used in eclipse prediction to take this slowing into account. As Earth slows, ΔT increases. ΔT for dates in

6000-427: The eclipse limit creates a window of opportunity of up to 36 degrees (24 degrees for central eclipses), it is possible for partial eclipses (or rarely a partial and a central eclipse) to occur in consecutive months. During a central eclipse, the Moon's umbra (or antumbra, in the case of an annular eclipse) moves rapidly from west to east across Earth. Earth is also rotating from west to east, at about 28 km/min at

6100-578: The ecliptic at the two nodes that are 180 degrees apart. Therefore, the new moon occurs close to the nodes at two periods of the year approximately six months (173.3 days) apart, known as eclipse seasons , and there will always be at least one solar eclipse during these periods. Sometimes the new moon occurs close enough to a node during two consecutive months to eclipse the Sun on both occasions in two partial eclipses. This means that, in any given year, there will always be at least two solar eclipses, and there can be as many as five. Eclipses can occur only when

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6200-438: The effects of light pollution, which has increased the popularity of astrophotography in urban areas. Narrowband filters may also be used to minimize light pollution. Scientific research is most often not the main goal for many amateur astronomers, unlike professional astronomers. Work of scientific merit is possible, however, and many amateurs successfully contribute to the knowledge base of professional astronomers. Astronomy

6300-499: The end of totality, the same effects will occur in reverse order, and on the opposite side of the Moon. A dedicated group of eclipse chasers have pursued the observation of solar eclipses when they occur around Earth. A person who chases eclipses is known as an umbraphile, meaning shadow lover. Umbraphiles travel for eclipses and use various tools to help view the sun including solar viewing glasses , also known as eclipse glasses, as well as telescopes. The first known photograph of

6400-403: The entire night sky. A range of astronomy software is also available and used by amateur astronomers, including software that generates maps of the sky, software to assist with astrophotography, observation scheduling software, and software to perform various calculations pertaining to astronomical phenomena. Amateur astronomers often like to keep records of their observations, which usually takes

6500-454: The form of an observing log. Observing logs typically record details about which objects were observed and when, as well as describing the details that were seen. Sketching is sometimes used within logs, and photographic records of observations have also been used in recent times. The information gathered is used to help studies and interactions between amateur astronomers in yearly gatherings. Although not professional information or credible, it

6600-446: The future can only be roughly estimated because Earth's rotation is slowing irregularly. This means that, although it is possible to predict that there will be a total eclipse on a certain date in the far future, it is not possible to predict in the far future exactly at what longitudes that eclipse will be total. Historical records of eclipses allow estimates of past values of ΔT and so of Earth's rotation. The following factors determine

6700-434: The future may now be predicted with high accuracy. Looking directly at the Sun can lead to permanent eye damage, so special eye protection or indirect viewing techniques are used when viewing a solar eclipse. Only the total phase of a total solar eclipse is safe to view without protection. Enthusiasts known as eclipse chasers or umbraphiles travel to remote locations to see solar eclipses. The Sun's distance from Earth

6800-405: The future, the Moon will be too far away to fully occlude the Sun, and no total eclipses will occur. In the same timeframe, the Sun may become brighter, making it appear larger in size. Estimates of the time when the Moon will be unable to occlude the entire Sun when viewed from Earth range between 650 million and 1.4 billion years in the future. Looking directly at the photosphere of

6900-418: The hobby of amateur astronomy. Although specialized and experienced amateur astronomers tend to acquire more specialized and more powerful equipment over time, relatively simple equipment is often preferred for certain tasks. Binoculars, for instance, although generally of lower power than the majority of telescopes, also tend to provide a wider field of view , which is preferable for looking at some objects in

7000-412: The invasion accepted by historians. In ancient China, where solar eclipses were known as an "eating of the Sun" ( rìshí 日食 ), the earliest records of eclipses date to around 720 BC. The 4th century BC astronomer Shi Shen described the prediction of eclipses by using the relative positions of the Moon and Sun. Attempts have been made to establish the exact date of Good Friday by assuming that

7100-429: The last bright flash of sunlight. It is safe to observe the total phase of a solar eclipse directly only when the Sun's photosphere is completely covered by the Moon, and not before or after totality. During this period, the Sun is too dim to be seen through filters. The Sun's faint corona will be visible, and the chromosphere , solar prominences , coronal streamers and possibly even a solar flare may be seen. At

7200-429: The latter being favored by most recent authors on the topic. A solar eclipse of June 15, 763 BC mentioned in an Assyrian text is important for the chronology of the ancient Near East . There have been other claims to date earlier eclipses. The legendary Chinese king Zhong Kang supposedly beheaded two astronomers, Hsi and Ho, who failed to predict an eclipse 4000 years ago. Perhaps the earliest still-unproven claim

7300-423: The lens and viewfinder protects the equipment and makes viewing possible. Professional workmanship is essential because of the dire consequences any gaps or detaching mountings will have. In the partial eclipse path, one will not be able to see the corona or nearly complete darkening of the sky. However, depending on how much of the Sun's disk is obscured, some darkening may be noticeable. If three-quarters or more of

7400-428: The lens is covered by a properly designed solar filter. Historical eclipses are a very valuable resource for historians, in that they allow a few historical events to be dated precisely, from which other dates and ancient calendars may be deduced. The oldest recorded solar eclipse was recorded on a clay tablet found at Ugarit , in modern Syria , with two plausible dates usually cited: 3 May 1375 BC or 5 March 1223 BC,

7500-414: The longest total eclipse of the 20th century at 7 min 8 s occurred on June 20, 1955 , and there will be no total solar eclipses over 7 min in duration in the 21st century. It is possible to predict other eclipses using eclipse cycles . The saros is probably the best known and one of the most accurate. A saros lasts 6585.3 days (a little over 18 years), which means that, after this period,

7600-424: The magnitude of an eclipse changes during the event from less to greater than one, so the eclipse appears to be total at locations nearer the midpoint, and annular at other locations nearer the beginning and end, since the sides of Earth are slightly further away from the Moon. These eclipses are extremely narrow in their path width and relatively short in their duration at any point compared with fully total eclipses;

7700-613: The moon do not eclipse because of the death of someone from the people but they are two signs amongst the signs of God." The Cairo astronomer Ibn Yunus wrote that the calculation of eclipses was one of the many things that connect astronomy with the Islamic law , because it allowed knowing when a special prayer can be made. The first recorded observation of the corona was made in Constantinople in AD 968. The first known telescopic observation of

7800-514: The most favourable circumstances, when a total eclipse occurs very close to perigee, the track can be up to 267 km (166 mi) wide and the duration of totality may be over 7 minutes. Outside of the central track, a partial eclipse is seen over a much larger area of Earth. Typically, the umbra is 100–160 km wide, while the penumbral diameter is in excess of 6400 km. Besselian elements are used to predict whether an eclipse will be partial, annular, or total (or annular/total), and what

7900-486: The newly formed astronomy department there. His wife Antoinette died in 1987. In 1995 he died of a heart attack in his home in Austin at the age of 77. At the time of his death he had a second wife named Elysabeth. His earliest work had concerned the planet Mars and while at Harvard he used telescope observations from 1909 to 1958 to study the areographic coordinates of features on the surface of Mars. His later work focused on

8000-469: The night sky. Recent models of iPhones have introduced a "night mode " option when taking pictures as well, that allows you to increase exposure, which is a period of time the picture is being taken for. This optimizes focus on light in the frame which is why it is used primarily at night. Amateur astronomers also use star charts that, depending on experience and intentions, may range from simple planispheres through to star atlases with detailed charts of

8100-406: The object. GOTO also allows manufacturers to add equatorial tracking to mechanically simpler alt-azimuth telescope mounts, allowing them to produce an overall less expensive product. GOTO telescopes usually have to be calibrated using alignment stars to provide accurate tracking and positioning. However, several telescope manufacturers have recently developed telescope systems that are calibrated with

8200-514: The projector (telescope, pinhole, etc.) directly. A kitchen colander with small holes can also be used to project multiple images of the partially eclipsed Sun onto the ground or a viewing screen. Viewing the Sun's disk on a video display screen (provided by a video camera or digital camera ) is safe, although the camera itself may be damaged by direct exposure to the Sun. The optical viewfinders provided with some video and digital cameras are not safe. Securely mounting #14 welder's glass in front of

8300-624: The relatively small number of large telescopes that are available to professional astronomers. Several organizations, such as the American Association of Variable Star Observers and the British Astronomical Association , exist to help coordinate these contributions. Amateur astronomers often contribute toward activities such as monitoring the changes in brightness of variable stars and supernovae , helping to track asteroids , and observing occultations to determine both

8400-449: The same orbital plane as Earth, there would be total solar eclipses once a month, at every new moon. Instead, because the Moon's orbit is tilted at about 5 degrees to Earth's orbit, its shadow usually misses Earth. Solar (and lunar) eclipses therefore happen only during eclipse seasons , resulting in at least two, and up to five, solar eclipses each year, no more than two of which can be total. Total eclipses are rarer because they require

8500-420: The same way, but not as much as does the Moon's varying distance from Earth. When Earth approaches its farthest distance from the Sun in early July, a total eclipse is somewhat more likely, whereas conditions favour an annular eclipse when Earth approaches its closest distance to the Sun in early January. There are three main types of solar eclipses: A total eclipse occurs on average every 18 months when

8600-542: The science of astronomy among the general public. Collectively, amateur astronomers observe a variety of celestial objects and phenomena. Common targets of amateur astronomers include the Sun , the Moon , planets , stars , comets , meteor showers , and a variety of deep sky objects such as star clusters , galaxies , and nebulae . Many amateurs like to specialise in observing particular objects, types of objects, or types of events which interest them. One branch of amateur astronomy, amateur astrophotography , involves

8700-420: The shape of asteroids and the shape of the terrain on the apparent edge of the Moon as seen from Earth. With more advanced equipment, but still cheap in comparison to professional setups, amateur astronomers can measure the light spectrum emitted from astronomical objects, which can yield high-quality scientific data if the measurements are performed with due care. A relatively recent role for amateur astronomers

8800-531: The sky at night, when most celestial objects and astronomical events are visible, but others observe during the daytime by viewing the Sun and solar eclipses . Some just look at the sky using nothing more than their eyes or binoculars, but more dedicated amateurs often use portable telescopes or telescopes situated in their private or club observatories . Amateurs also join amateur astronomical societies , which can advise, educate or guide them towards ways of finding and observing celestial objects. They also promote

8900-474: The sky include telescope mounts with setting circles , which allow pointing to targets in the sky using celestial coordinates , and GOTO telescopes , which are fully automated telescopes that are capable of locating objects on demand (having first been calibrated). The advent of mobile applications for use in smartphones has led to the creation of many dedicated apps. These apps allow any user to easily locate celestial objects of interest by simply pointing

9000-419: The smartphone device in that direction in the sky. These apps make use of the inbuilt hardware in the phone, such as GPS location and gyroscope . Useful information about the pointed object like celestial coordinates, the name of the object, its constellation, etc. are provided for a quick reference. Some paid versions give more information. These apps are gradually getting into regular use during observing, for

9100-518: The study of galaxies and he co-authored the Third Reference Catalogue of Bright Galaxies with his wife Antoinette (1921-1987), a fellow UT Austin astronomer and lifelong collaborator. His specialty included reanalyzing Hubble and Sandage's galaxy atlas and recomputing the distance measurements utilizing a method of averaging many different kinds of metrics such as luminosity, the diameters of ring galaxies, brightest star clusters, etc., in

9200-441: The taking of photos of the night sky. Astrophotography has become more popular with the introduction of far easier to use equipment including, digital cameras, DSLR cameras and relatively sophisticated purpose built high quality CCD cameras and CMOS cameras . Most amateur astronomers work at visible wavelengths , but a small minority experiment with wavelengths outside the visible spectrum . An early pioneer of radio astronomy

9300-659: The telescope user can use the setting circle to align (i.e., point) the telescope in the appropriate direction before looking through its eyepiece . A computerized setting circle is called a "digital setting circle" (DSC). Although digital setting circles can be used to display a telescope's RA and Dec coordinates, they are not simply a digital read-out of what can be seen on the telescope's analog setting circles. As with go-to telescopes, digital setting circle computers (commercial names include Argo Navis, Sky Commander, and NGC Max) contain databases of tens of thousands of celestial objects and projections of planet positions. To find

9400-449: The time of a new moon, the Moon will usually pass to the north or south of the Sun. A solar eclipse can occur only when a new moon occurs close to one of the points (known as nodes ) where the Moon's orbit crosses the ecliptic. As noted above, the Moon's orbit is also elliptical . The Moon's distance from Earth varies by up to about 5.9% from its average value. Therefore, the Moon's apparent size varies with its distance from Earth, and it

9500-419: The umbra touches Earth's surface is where a total eclipse can be seen. The larger light gray area is the penumbra , in which a partial eclipse can be seen. An observer in the antumbra , the area of shadow beyond the umbra, will see an annular eclipse. The Moon's orbit around Earth is inclined at an angle of just over 5 degrees to the plane of Earth's orbit around the Sun (the ecliptic ). Because of this, at

9600-508: The use of built-in GPS, decreasing the time it takes to set up a telescope at the start of an observing session. With the development of fast internet in the last part of the 20th century along with advances in computer controlled telescope mounts and CCD cameras, "remote telescope" astronomy is now a viable means for amateur astronomers not aligned with major telescope facilities to partake in research and deep sky imaging. This enables anyone to control

9700-454: The visual and non-visual parts of the spectrum. To further improve studying the visual and non-visual part of the spectrum, amateur astronomers go to rural areas to get away from light pollution . Commercial telescopes are available, new and used, but it is also common for amateur astronomers to build (or commission the building of) their own custom telescopes. Some people even focus on amateur telescope making as their primary interest within

9800-570: Was Grote Reber , an amateur astronomer who constructed the first purpose-built radio telescope in the late 1930s to follow up on the discovery of radio wavelength emissions from space by Karl Jansky . Non-visual amateur astronomy includes the use of infrared filters on conventional telescopes, and also the use of radio telescopes . Some amateur astronomers use home-made radio telescopes, while others use radio telescopes that were originally built for astronomical research but have since been made available for use by amateurs. The One-Mile Telescope

9900-488: Was June 30, 1973 (7 min 3 sec). Observers aboard a Concorde supersonic aircraft were able to stretch totality for this eclipse to about 74 minutes by flying along the path of the Moon's umbra. The next total eclipse exceeding seven minutes in duration will not occur until June 25, 2150 . The longest total solar eclipse during the 11 000 year period from 3000 BC to at least 8000 AD will occur on July 16, 2186 , when totality will last 7 min 29 s. For comparison,

10000-422: Was on April 29, 2014 . This was an annular eclipse. The next non-central total solar eclipse will be on April 9, 2043 . The visual phases observed during a total eclipse are called: The diagrams to the right show the alignment of the Sun, Moon, and Earth during a solar eclipse. The dark gray region between the Moon and Earth is the umbra , where the Sun is completely obscured by the Moon. The small area where

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