Fred Espenak
To Be Published in Observer's Handbook 2008, Royal Astronomical Society of Canada
During the year 2008, two solar and two lunar eclipses occur as follows:
- 2008 Feb 07: Annular Solar Eclipse
- 2008 Feb 21: Total Lunar Eclipse
- 2008 Aug 01: Total Solar Eclipse
- 2008 Aug 16: Partial Lunar Eclipse
Predictions for the eclipses are summarized in Figures1,2,3,4,5, and6.World maps show the regions of visibility for each eclipse. Thelunar eclipse diagrams also include the path of the Moon throughEarth's shadows. Contact times for each principal phase aretabulated along with the magnitudes and geocentric coordinates ofthe Sun and Moon at greatest eclipse.
All times and dates used in this publication are in UniversalTime or UT. This astronomically derived time system iscolloquially referred to as Greenwich Mean Time or GMT. Tolearn more about UT and how to convert UT to your own local time,see Time Zones and UniversalTime.
Annular Solar Eclipse of February 07
The first solar eclipse of 2008 occurs at the Moon's ascendingnode in Capricornus. An annular eclipse will be visible from a widetrack, that traverses Antarctica and southern regions of the PacificOcean. A partial eclipse will be seen within the much larger path ofthe Moon's penumbral shadow, which includes the southeastern third ofAustralia, all of New Zealand and most of Antarctica (Figure 1).
The annular path begins in Antarctica at 03:20 UT when theMoon's antumbral shadow meets Earth and forms a 581 kilometre widecorridor near the base of the continent's peninsula region. Travelingwestward, the shadow quickly crosses Antarctica and turns north as itheads into the Pacific. Greatest eclipse[1] takes place at 03:55:05 UTwhen the eclipse magnitude[2] will reach 0.9650. At this instant, theannular duration is 2 minutes 12 seconds, the path width is 444kilometres and the Sun is 16° above the featureless horizon ofthe open ocean. The central track continues north before graduallycurving to the east where it ends at local sunset at 04:31 UT. Duringits 1 hour 10 minute flight across our planet, the Moon's antumbratravels approximately 5,600 kilometres and covers 0.59% of Earth'ssurface area. Path coordinates and central line circ*mstances arepresented in Table 1.
The most unusual characteristic of this eclipse is that itbegins and ends along Earth's sunset terminator. Most eclipse pathsthat travel from west to east. However, the 2008 annular eclipse pathbegins by running east to west and slowly turns north before curvingwest to east near its terminus.
Partial phases of the eclipse are visible primarily from easternAustralia, New Zealand and the South Pacific. Local circ*mstances for anumber of cities are listed in Table 2. All times are given inUniversal Time. The Sun's altitude and azimuth, the eclipse magnitudeand obscuration are all given at the instant of maximum eclipse.
This is the 60th eclipse of Saros 121. The series began with the firstof six partial eclipses on 0944 Apr 25. The first central eclipse wastotal in the Northern Hemisphere on 1070 Jul 10. It was followed by 41more total eclipses before the series produce two hybrid eclipses in1827 and 1845. The first annular eclipse of the series occurred on 1863Nov 11. The series will produce 11 annular eclipses the last of whichis 2044 Feb 28. This means there are only two more central eclipsesafter the 2008 eclipse. The series terminates on 2206 Jun 07 after 9more partial eclipses. Complete details for Saros 121 may be found at:
http://eclipse.gsfc.nasa.gov/SEsaros/SEsaros121.html
Click for special web page on the Total Lunar Eclipse of 2008 Feb 21
Total Lunar Eclipse of Feb 21
(Note: The Feb 21 date used here corresponds to the Universal Time of greatest eclipse. However, observers throughout North and South America will actually see the eclipse on the evening of Feb 20.For more information see Special 2008 Lunar Eclipse Page).
The first lunar eclipse of 2008 is perfectly placed for observersthroughout most of the Americas as well as western Europe. The eclipseoccurs at the Moon's descending node, midway between perigee andapogee. During the eclipse, Saturn lies about 3° northeast ofthe Moon and shines brightly (mv = +0.2) because it is near opposition.
The Moon's orbital trajectory takes it through the southern half ofEarth’s umbral shadow. Although the eclipse is not central,the total phase still lasts nearly 51 minutes. The Moon’spath through Earth’s shadows as well as a map illustratingworldwide visibility of the event are shown in Figure 2. Thetimings of the major phases of the eclipse are listed below.
Penumbral Eclipse Begins: 00:36:35 UTPartial Eclipse Begins: 01:43:19 UTTotal Eclipse Begins: 03:01:10 UTGreatest Eclipse: 03:26:05 UTTotal Eclipse Ends: 03:50:57 UTPartial Eclipse Ends: 05:08:47 UTPenumbral Eclipse Ends: 06:15:39 UT
At the instant of greatest eclipse (03:26 UT) the Moon lies near thezenith for observers in French Guiana. At this time, the umbralmagnitude peaks at 1.1062 as the Moon’s northern limb passes7.2 arc-minutes south of the shadow’s central axis. Incontrast, the Moon’s southern limb lies 3.3 arc-minutes fromthe southern edge of the umbra and 38.4 arc-minutes from the shadowcentre. Thus, the northern half of the Moon will appear much darkerthan the southern half because it lies deeper in the shadow. Since theMoon samples a large range of umbral depths during totality, itsappearance will change dramatically with time. It is not possible topredict the exact brightness distribution in the umbra, so observersare encouraged to estimate the Danjon value at different times duringtotality (see Danjon Scale of Lunar Eclipse Brightness). Note that itmay also be necessary to assign different Danjon values to differentportions of the Moon (i.e., north vs. south).
During totality, the spring constellations are well placed for viewingso a number of bright stars can be used for magnitude comparisons.Regulus (mv = +1.40) is 3° northwest of the eclipsedMoon, while Procyon (mv = -0.05) is 40° to the west, Spica (mv= +0.98) is 51° to the southeast, and Arcturus (mv =-0.05) is 58° to the northeast. Alphard or Alpha Hya (mv =+1.99) is 23° to the southwest and Saturn (mv = +0.2)is just 3° to the northeast of the Moon.
The entire event is visible from South America and most of NorthAmerica. Observers along North America's west coast miss the earlystages of the partial eclipse because it begins before moon rise.Alaskans in Anchorage and Fairbanks experience moonrise during totalitybut bright evening twilight will make it difficult for sourdoughs toview the event. Western Europe and northwest Africa also see the entireeclipse. Further to the east (east Africa and central Asia), the Moonsets before the eclipse ends. None of the eclipse is visible fromeastern Asia or Australia.
Table 3lists predicted umbral immersion and emersion timesfor 20 well-defined lunar craters. The timing of craters is useful indetermining the atmospheric enlargement of Earth’s shadow(see Crater Timings During Lunar Eclipses).
For more information see Special 2008 Lunar Eclipse Page.
Total Solar Eclipse of August 01
On Friday, August 01, a total eclipse of the Sun is visible from anarrow corridor that traverses half the Earth. The path of theMoon’s umbral shadow begins in Canada and extends acrossnorthern Greenland, the Arctic, central Russia, Mongolia, and Chinawhere it will end at sunset [Espenak and Anderson, 2006]. A partialeclipse is seen within the much broader path of the Moon’spenumbral shadow, which includes northeastern North America, and mostof Europe and Asia (Figure 3).
The path of totality begins in northern Canada, where theMoon’s umbral shadow first touches down in the province ofNunavut at 09:23 UT (Figure 4). Along the sunrise terminator in QueenMaud Gulf, the duration is 1min 30s from the centre of the 206km widepath. Traveling over 0.6km/s, the umbra quickly sweeps north acrosssouthern Victoria Island, Prince of Wales Island and Northern SomersetIsland. The shadow's northern limit clips the southeastern corner ofCornwallis Island and just misses the high Arctic town of Resolute. Thenearly 200 residents of this isolated settlement will witness a partialeclipse of magnitude of 0.997 at 09:26 UT with the Sun 7° abovethe horizon.
Continuing on its northeastern trajectory, the umbra crosses DevonIsland and reaches the southern coast of Ellesmere Island. The centralline cuts across Nares Strait as the shadow straddles Ellesmere Islandand Greenland. Canada's remote outpost Alert, the northernmostpermanently inhabited place on Earth, lies near the northern limit ofthe eclipse track and experiences 43s totality with the Sun at16° altitude at 09:32 UT.
After crossing northern Greenland, the track passes between Franz JosefLand and Svalbard. By the time the central line reaches the northerncoast of Novaya Zemlya (10:00 UT), the duration is 2min 23s with theSun at 31°. The track crosses both the island and the Kara Seabefore reaching the Yamal Peninsula and the Russian mainland.
The instant of greatest eclipse occurs at 10:21:07 UT(latitude 65° 39'N, longitude 72° 18'E) when the axisof the Moon’s shadow passes closest to the centre of Earth(gamma = +0.8307, where gamma is the minimum distance of theMoon’s shadow axis from Earth’s centre in units ofequatorial Earth radii). Totality reaches its maximum duration of 2min27s, the Sun’s altitude is 34°, the path width is237km and the umbra’s velocity is 0.507km/s.
During the next hour, the Moon's umbra works its way across centralAsia (Figure 5). The shadow gradually picks up speed and its coursechanges from south-southeast to nearly east at its terminus.Novosibirsk, Russia's third most populous city, lies only 18km from thecentral line. The midpoint of Novosibirsk's 2min 18s total eclipseoccurs at 10:45 UT with the Sun's altitude at 30°. Three and ahalf minutes later, Barnaul is plunged into a 2min 16s total eclipse.
The centre of the track follows the China-Mongolia border for severalhundred kilometres while the central duration and the Sun's altitudeboth decrease. From Altay, China, the total eclipse begins at 10:59 UTand lasts 1min 25s with the Sun 25° above the horizon. Acrossthe border, western Mongolia is very sparsely populated and the AltanMountains bring cloudiness to the area. Ten minutes later, the umbrajust misses Hami, China where a deep partial eclipse of magnitude 0.998occurs at 11:10 UT. This region in northwest China is noteworthybecause it offers some of the most promising weather prospects alongthe entire eclipse path. Its position between the Gobi Desert to theeast and the Talikmakan Desert to the west spares it from the monsoonsystems that affect much of Southeast Asia during the summer months.
During the final ten minutes of the umbra's track, it quickly sweepsacross northern China as the duration of totality and the Sun'saltitude decrease. The major city of Xi'an straddles the southern limitwhere maximum eclipse occurs with the Sun just 4° above thehorizon. From the central line 106 km to the north, the duration oftotality still lasts 1min 35s. Seconds later, the axis of the Moon'sshadow lifts off Earth and the central eclipse ends (11:20 UT). Overthe course of 2 hours, the Moon’s umbra travels along a pathapproximately 10,200 km long and covers 0.4% of Earth’ssurface area. Path coordinates and central line circ*mstances arepresented in Table 4.
Partial phases of the eclipse are visible from most of Asia, northernEurope and northern Canada. Local circ*mstances for a number of citiesare listed in Table 5. All times are given in Universal Time. The Sun'saltitude and azimuth, the eclipse magnitude and obscuration are allgiven at the instant of maximum eclipse.
This is the 47th eclipse of Saros 126. The series began with the firstof eight partial eclipses on 1179 Mar 10. The first central eclipse wasannular in the Southern Hemisphere on 1305 May 24. It was followed by27 more annular eclipses before the series produce three hybrideclipses in 1828, 1846 and 1864. The first total eclipse of the seriesoccurred on 1882 May 17. The series will produce 10 total eclipses, thelast of which is 2044 Aug 23. Thus, there are only two more centraleclipses after the 2008 eclipse. The series terminates on 2459 May 03after a long string of 23 partial eclipses. Complete details for Saros126 may be found at:
http://eclipse.gsfc.nasa.gov/SEsaros/SEsaros126.html
Partial Lunar Eclipse of August 16
The last eclipse of 2008 is a partial lunar eclipse at the Moon'sascending node in Capricornus. It is visibile primarily from theEastern Hemisphere as well as eastern South America (Figure 6).Greatest eclipse takes place at 21:10:06 UT when the eclipse magnitudewill reach 0.8076. The timings of the major phases of the eclipse arelisted below.
Penumbral Eclipse Begins: 18:24:49 UTPartial Eclipse Begins: 19:36:07 UTGreatest Eclipse: 21:10:09 UTPartial Eclipse Ends: 22:44:16 UTPenumbral Eclipse Ends: 23:55:25 UT
The Moon’s trajectory takes it through the northern umbralshadow, resulting in a partial eclipse that lasts 3 hours 8 minutes. At mid-eclipse the Moon's northern limb passes 5.9 arc-minutes outside theumbra's northern edge. The Moon's southern edge is then 16.5arc-minutes from the shadow's centre.
Table 6 lists predicted umbral immersion and emersion timesfor 17 well-defined lunar craters. The timing of craters is useful indetermining the atmospheric enlargement of Earth’s shadow(see Crater Timings During Lunar Eclipses).
Solar Eclipse Figures
For each solar eclipse, an orthographic projection map of Earth showsthe path of penumbral (partial) and umbral (total or annular) eclipse.North is to the top in all cases and the daylight terminator is plottedfor the instant of greatest eclipse. An asterisk (*) indicates thesub-solar point[3] on Earth.
The limits of the Moon's penumbral shadow delineate the region ofvisibility of the partial solar eclipse. This irregular or saddleshaped region often covers more than half of the daylight hemisphere ofEarth and consists of several distinct zones or limits. At the northernand/or southern boundaries lie the limits of the penumbra's path.Partial eclipses have only one of these limits, as do central eclipseswhen the Moon's shadow axis falls no closer than about 0.45 radii fromEarth's centre. Great loops at the western and eastern extremes of thepenumbra's path identify the areas where the eclipse begins/ends atsunrise and sunset, respectively. If the penumbra has both a northernand southern limit, the rising and setting curves form two separate,closed loops. Otherwise, the curves are connected in a distorted figureeight. Bisecting the 'eclipse begins/ends at sunrise and sunset' loopsis the curve of maximum eclipse at sunrise (western loop) and sunset(eastern loop). The points P1 and P4 mark the coordinates where thepenumbral shadow first contacts (partial eclipse begins) and lastcontacts (partial eclipse ends) Earth's surface. If the penumbral pathhas both a northern and southern limit, then points P2 and P3 are alsoplotted. These correspond to the coordinates where the penumbral shadowcone becomes internally tangent to Earth's disk.
A curve of maximum eclipse is the locus of all points where the eclipseis at maximum at a given time. Curves of maximum eclipse are plotted ateach half-hour Universal Time. They generally run between the penumbrallimits in the north/south direction, or from the 'maximum eclipse atsunrise and sunset' curves to one of the limits. If the eclipse iscentral (i.e. total or annular), the curves of maximum eclipse runthrough the outlines of the umbral shadow, which are plotted atten-minute intervals. The curves of constant eclipse magnitudedelineate the locus of all points where the magnitude at maximumeclipse is constant. These curves run exclusively between the curves ofmaximum eclipse at sunrise and sunset. Furthermore, they are parallelto the northern/southern penumbral limits and the umbral paths ofcentral eclipses. In fact, the northern and southern limits of thepenumbra can be thought of as curves of constant magnitude of 0.0. Theadjacent curves are for magnitudes of 0.2, 0.4, 0.6 and 0.8. For totaleclipses, the northern and southern limits of the umbra are curves ofconstant magnitude of 1.0. Umbral path limits for annular eclipses arecurves of maximum eclipse magnitude.
Greatest eclipse is defined as the instant when the axis of the Moon'sshadow passes closest to Earth's centre. Although greatest eclipsediffers slightly from the instants of greatest magnitude and greatestduration (for total eclipses), the differences are negligible. Thepoint on Earth's surface intersected by the axis at greatest eclipse ismarked by an asterisk symbol. For partial eclipses, the shadow axismisses Earth entirely, so the point of greatest eclipse lies on theday/night terminator and the Sun appears on the horizon.
Data pertinent to the eclipse appear with each map. At the top arelisted the instant of ecliptic conjunction of the Sun and Moon (i.e.,New Moon) and the instant of greatest eclipse, expressed in TerrestrialDynamical Time and Universal Time. The eclipse magnitude is defined asthe fraction of the Sun's diameter obscured by the Moon at greatesteclipse. For central eclipses (total or annular), the magnitude isreplaced by the geocentric ratio of diameters of the Moon and the Sun.Gamma is the minimum distance of the Moon's shadow axis from Earth'scentre in Earth radii at greatest eclipse. The Saros series of theeclipse is listed, followed by the member position. The first membernumber identifies the sequence position of the eclipse in the Saros,while the second is the total number of eclipses in the series.
In the upper left and right corners are the geocentric coordinates ofthe Sun and the Moon, respectively, at the instant of greatest eclipse.They are:
R.A. - Right Ascension
Dec. - Declination
S.D. - Apparent Semi-Diameter
H.P. - Horizontal Parallax
To the lower left are exterior/interior contact times of the Moon'spenumbral shadow with Earth, which are defined:
P1 - Instant of first exterior tangency of Penumbra with Earth's limb. (Partial Eclipse Begins)
P2 - Instant of first interior tangency of Penumbra with Earth's limb.
P3 - Instant of last interior tangency of Penumbra with Earth's limb.
P4 - Instant of last exterior tangency of Penumbra with Earth's limb. (Partial Eclipse Ends)
Not all eclipses have P2 and P3 penumbral contacts. They are only present in cases where the penumbral shadow falls completely within Earth's disk. For central eclipses, the lower right corner lists exterior/interior contact times of the Moon's umbral shadow with Earth's limb which are defined as follows:
U1 - Instant of first exterior tangency of Umbra with Earth's limb. (Umbral [Total/Annular] Eclipse Begins)
U2 - Instant of first interior tangency of Umbra with Earth's limb.
U3 - Instant of last interior tangency of Umbra with Earth's limb.
U4 - Instant of last exterior tangency of Umbra with Earth's limb. (Umbral [Total/Annular] Eclipse Ends)
At bottom centre are the geographic coordinates of the position of greatesteclipse along with the local circ*mstances at that location (i.e.,Sun altitude, Sun azimuth, path width and duration of totality/annularity).At bottom left are a list of parameters used in the eclipse predictions, whilebottom right gives the Moon's geocentric libration (optical + physical) atgreatest eclipse.
Lunar Eclipse Figures
Each lunar eclipse has two diagrams associated with it along with datapertinent to the eclipse. The top figure shows the path of the Moonthrough Earth’s penumbral and umbral shadows. Above thisfigure are listed the instant of ecliptic conjunction of the Moon withthe point 180° from the Sun (i.e., Full Moon) and the instantof greatest eclipse, expressed in Terrestrial Dynamical Time andUniversal Time. The penumbral and umbral magnitudes are defined as thefraction of the Moon’s diameter immersed in the two shadowsat greatest eclipse. The radii of the penumbral and umbral shadows, P. Radius and U. Radius, are alsolisted. Gammais the minimum distance in Earth radii of the Moon’s centrefrom Earth’s shadow axis at greatest eclipse, and Axis is the sameparameter expressed in degrees. The Saros series of the eclipse islisted, followed by a pair of numbers. The first number identifies thesequence position of the eclipse in the Saros; the second is the totalnumber of eclipses in the series.
In the upper left and right corners are the geocentric coordinates ofthe Sun and the Moon, respectively, at the instant of greatest eclipse.They are:
R.A. - Right Ascension
Dec. - Declination
S.D. - Apparent Semi-Diameter
H.P. - Horizontal Parallax
To the lower left are the semi, or half, durations of the penumbral,umbral (partial), and total eclipses. Below them are the Sun/Moonephemerides used in the predictions, followed by the extrapolated valueof ΔT (the difference between Terrestrial Dynamical Time and UniversalTime). To the lower right are the contact times of the Moon withEarth’s penumbral and umbral shadows, defined as follows:
P1 - Instant of first exterior tangency of Moon with Penumbra. (Penumbral Eclipse Begins)
U1 - Instant of first exterior tangency of Moon with Umbra. (Partial Umbral Eclipse Begins)
U4 - Instant of last exterior tangency of Moon with Umbra (Partial Umbral Eclipse Ends)
P4 - Instant of last exterior tangency of Moon with Penumbra. (Penumbral Eclipse Ends)
The bottom figure is an equidistant cylindrical projection map of Earththat shows the regions of visibility for each stage of the eclipse. Inparticular, the moonrise/moonset terminator is plotted for each contactand is labeled accordingly. The point where the Moon is in the zenithat greatest eclipse is indicated by an asterisk. The region that iscompletely unshaded will observe the entire eclipse, while the darklyshaded area will witness no eclipse. The remaining lightly shaded areaswill experience moonrise or moonset while the eclipse is in progress.The shaded zones east of the asterisk will witness moonset before theeclipse ends, and the shaded zones west will witness moonrise after theeclipse has begun.
Shadow Diameters and Lunar Eclipses
To compensate for Earth's atmosphere when calculating the circ*mstancesfor lunar eclipses, Chauvenet [1891] introduced an empiricalenlargement of 1/50 to the diameters of the umbral and penumbralshadows . This rule has been employed by many of the nationalinstitutes in their official eclipse predictions (including theauthor's work at NASA). However, Danjon [1951] pointed out a flaw inthis method because it applies the same relative correction to theumbra and penumbra instead of using the same absolute correction. Fromeclipse observations, Danjon proposed to enlarge Earth's diameter by1/85 to compensate for the atmosphere. The umbral and penumbral shadowdiameters are then calculated based on this modified geometry. TheFrench almanac "Connaissance des Temps" has used the Danjon rule in itseclipse predictions since 1951. The resulting umbral and penumbraleclipse magnitudes are smaller by approximately 0.005 and 0.026,respectively, as compared to predictions using the traditional 1/50rule.
Beginning with Eclipses During 2007, we use the Danjon rule in calculating lunareclipse circ*mstances and magnitudes.
Danjon Scale of Lunar Eclipse Brightness
The Moon’s appearance during a total lunar eclipse can varyenormously from one eclipse to the next. Obviously, the geometry of theMoon’s path through the umbra plays an important role. Not asapparent is the effect that Earth’s atmosphere has on totaleclipses. Although the physical mass of Earth blocks all directsunlight from the umbra, the planet’s atmosphere refractssome of the Sun’s rays into the shadow. Earth’satmosphere contains varying amounts of water (clouds, mist,precipitation) and solid particles (meteoric dust, organic debris,volcanic ash). This material significantly filters and attenuates thesunlight before it is refracted into the umbra. For instance, large orfrequent volcanic eruptions dumping huge quantities of ash into theatmosphere are often followed by very dark, red eclipses for severalyears. Extensive cloud cover along Earth’s limb also tends todarken the eclipse by blocking sunlight.
The French astronomer André-Louis Danjon proposed a usefulfive-point scale for evaluating the visual appearance and brightness ofthe Moon during total lunar eclipses. L values for various luminositiesare defined as follows:
L=0 Very dark eclipse. (Moon almost invisible, especially at mid-totality)L=1 Dark eclipse, grey or brownish in coloration. (details distinguishable only with difficulty)L=2 Deep red or rust-coloured eclipse. (very dark central shadow, while outer umbra is relatively bright)L=3 Brick-red eclipse. (umbral shadow usually has a bright or yellow rim)L=4 Very bright copper-red or orange eclipse. (umbral shadow has a bluish, very bright rim)
The assignment of an L value to lunar eclipses is best done with thenaked eye, binoculars, or a small telescope near the time ofmid-totality. It’s also useful to examine theMoon’s appearance just after the beginning and just beforethe end of totality. The Moon is then near the edge of the shadow,providing an opportunity to assign an L value to the outer umbra. Inmaking any evaluations, the instrumentation used and the time shouldboth be recorded. Also note any variations in colour and brightness indifferent parts of the umbra, as well as the apparent sharpness of theshadow’s edge. Pay attention to the visibility of lunarfeatures within the umbra. Notes and sketches made during the eclipseare often invaluable in recalling important details, events, andimpressions.
Crater Timings During Lunar Eclipses
In 1702, Pierre de La Hire made a curious observation aboutEarth’s umbra. In order to accurately predict the duration ofa lunar eclipse, he found it necessary to increase the radius of theshadow about 1% more than is warranted by geometric considerations.Although the effect is clearly related to Earth’s atmosphere,it is not completely understood, since the shadow enlargement seems tovary from one eclipse to the next. The enlargement can be measuredthrough careful timings of lunar craters as they enter and exit theumbra.
Such observations are best made using a low-power telescope and a clockor watch synchronized with radio time signals. Timings should be madeto a precision of 0.1 min. Record the instant when the most abruptgradient at the umbra’s edge crosses the apparent centre ofthe crater. In the case of large craters like Tycho and Copernicus,record the times when the shadow touches the two opposite edges of thecrater. The average of these times is equal to the instant of craterbisection.
As a planning guide, Tables 3 and 6 list 20 well-defined craters withpredicted umbral immersion and emersion times during the two lunareclipses of 2008. You should be thoroughly familiar with these featuresbefore viewing an eclipse in order to prevent confusion andmisidentification. The four umbral contacts with the Moon’slimb can also be used in determining the shadow’senlargement. However, these events are less distinct and thereforedifficult to time accurately. Observers are encouraged to make cratertimings and to send their results to Sky & Telescope (Sky& Telescope, 90 Sherman Street, Cambridge MA 02140-3264, USA)for analysis.
Note that all predictions presented here use Danjon's rule of shadowenlargement (see: Shadow Diameters and Lunar Eclipses). In particular, the diameterof the umbral shadow has been calculated assuming an enlargement ofEarth's radius of 1/85 to account for the opacity of the terrestrialatmosphere. The effects of Earth’s oblateness have also beenincluded.
Eclipse Altitudes and Azimuths
The altitude aand azimuth Aof the Sun or Moon during an eclipse dependon the time and the observer's geographic coordinates. They arecalculated as follows:
h = 15 (GST + UT - α ) + λa = arcsin [sin δ sin φ + cos δ cos h cos φ]A = arctan [-(cos δ sin h)/(sin δ cos φ - cos δ cos h sin φ)]whereh = hour angle of Sun or Moona = altitudeA = azimuthGST = Greenwich Sidereal Time at 0:00 UTUT = Universal Timeα = right ascension of Sun or Moonδ = declination of Sun or Moonλ = observer's longitude (east +, west -)φ = observer's latitude (north +, south -)
During the eclipses of 2008, the values for GST and the geocentricRight Ascension and Declination of the Sun or the Moon (at greatesteclipse) are as follows:
Eclipse Date GST α δAnnular Solar 2008 Feb 07 9.111 21.346 -15.516Total Lunar 2008 Feb 21 10.029 10.247 10.469Total Solar 2008 Aug 01 20.693 8.798 17.866Partial Lunar 2008 Aug 16 21.708 21.762 -12.925
Two web based tools that can also be used to calculate the localcirc*mstances for all solar and lunar eclipses visible from anylocation. They are the JavascriptSolar Eclipse Explorer and the Javascript Lunar Eclipse Explorer.The URLs for these tools are:
http://eclipse.gsfc.nasa.gov/JSEX/JSEX-index.html
http://eclipse.gsfc.nasa.gov/JLEX/JLEX-index.html
Eclipses During 2009
Next year (2009), there will be two central solar and four lunareclipses:
- 2009 Jan 26: Annular Solar Eclipse
- 2009 Feb 09: Penumbral Lunar Eclipse
- 2009 Jul 07: Penumbral Lunar Eclipse
- 2009 Jul 22: Total Solar Eclipse
- 2009 Aug 06: Penumbral Lunar Eclipse
- 2009 Dec 31: Partial Lunar Eclipse
A full report on eclipses during 2009 will be published in Observer’s Handbook2009.
NASA Solar Eclipse Bulletins
Special bulletins containing detailed predictions and meteorologicaldata for future solar eclipses of interest are prepared by Fred Espenakand Jay Anderson and are published through NASA’s Publicationseries. The bulletins are provided as a public service to both theprofessional and lay communities, including educators and the media. Alist of currently available bulletins and an order form can be found at:
http://eclipse.gsfc.nasa.gov/SEpubs/RPrequest.html
The most recent bulletin of the series covers the total solar eclipseof 2008 August 01 which is visible from northern Canada, Russia,Mongolia and China. Single copies of the eclipse bulletins areavailable at no cost by sending a 9 x 12-in. self-addressed envelopestamped with postage for 11 oz. (310 g). Please print the eclipse yearon the envelope’s lower left corner. Use stamps only, sincecash and cheques cannot be accepted. Requests from outside the UnitedStates and Canada may include 10 international postal coupons. Mailrequests to: Fred Espenak, NASA's Goddard Space Flight Center, Code693, Greenbelt MD 20771, USA.
The NASA eclipse bulletins are also available over the Internet,including out-of-print bulletins. Using a Web browser, they can be reador downloaded through the World Wide Web from the GSFC/SDAC (Solar DataAnalysis Center) eclipse page:
SEpubs/index.html
Eclipse Web Sites
The URL of the NASA Eclipse Web Site is:
http://eclipse.gsfc.nasa.gov/eclipse.html
The site features predictions and maps for all solar and lunar eclipseswell into the 21st century, with special emphasis on upcoming eclipses.Special pages are devoted to the total solar eclipses of 2008, 2009 and2010 that feature detailed maps, tables, graphs, and meteorologicaldata. A world atlas of solar eclipses provides maps of all centraleclipse paths from 2000 BCE to 3000 CE. The entire Five Millenium Canonof Solar Eclipses [Espenak and Meeus, 2006] can be downloaded in PDFformat and all maps are also available online as individual GIFs of PSFs.Additional catalogues list every solar and lunar eclipse over a5000-year period.
Detailed information on solar and lunar eclipse photography and tips oneclipse observing and eye safety may be found at:
Acknowledgments
All eclipse predictions were generated on an Apple G4 iMac computerusing algorithms developed from the Explanatory Supplement [1974] withadditional algorithms from Meeus, Grosjean, and Vanderleen [1966]. Thesolar coordinates used in the eclipse predictions are based on VSOP87[P. Bretagnon and G. Francou, 1988]. The lunar coordinates are based onELP-2000/82 [M. Chapront-Touzé and J. Chapront, 1983]. Forlunar eclipses, the diameter of the umbral and penumbral shadows werecalculated using Danjon's rule of enlarging Earth's radius by 1/85 tocompensate for the opacity of the terrestrial atmosphere; correctionsfor the effects of oblateness have also been included. Text and tablecomposition was done on a Macintosh using Microsoft Word. Additionalfigure annotation was performed with Claris MacDraw Pro.
All calculations, diagrams, tables, and opinions presented in thispaper are those of the author, and he assumes full responsibility fortheir accuracy.
Special thanks to National Space Club summer intern Sumit Duttafor his valuable assistance in preparing the web page (June 2007).
Footnotes
[1] The instant of greatest eclipse occurs when the distance between the Moon's shadow axis and Earth's geocentre reaches a minimum.
[2] Eclipse magnitude is defined as the fraction of the Sun's diameter occulted by the Moon
[3] The sub-solar point is the geographic location where the Sun appears directly overhead (zenith).
References
Bretagnon P., Francou G., "Planetary Theories in rectangular andspherical variables: VSOP87 solution", Astron. and Astrophys.,vol. 202, no. 309 (1988).
Chapront-Touzé, M and Chapront, J., "The Lunar Ephemeris ELP2000," Astron. andAstrophys., vol. 124, no. 1, pp 50-62 (1983).
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