June Moon at Ascending Node and a Solar Eclipse

   Sunday June 21st the new Moon will be crossing the plane of the ecliptic moving north. This is known as the ascending node, one of two intersections the Moon’s orbital path has with the ecliptic. The ecliptic is actually the Earth’s orbit, and the Moon’s orbit is inclined about 6o from the ecliptic. So there are two node intersections, the ascending and descending nodes.
   Whenever our Moon at either new or full phase crosses the plane of the ecliptic, a node crossing, there will be an eclipse of the Sun with a new Moon, or a lunar eclipse with the full Moon phase. On the 21st the new Moon will be aligned with the Sun for a solar eclipse. (Not visible from North America) However this solar eclipse is an annular solar eclipse, where at mid-eclipse the Moon does not completely cover the Sun. There is no ‘diamond bead’ effect, no corona like what is seen with a total solar eclipse. This is because the Moon and our Sun appear to be about the same size in the sky with the exception that the Moon’s orbit is more elliptical than the Earth’s orbit around the Sun. This means that the Moon can be closer or further away during a solar eclipse. With this annular solar eclipse the Moon is further away, appears smaller than the Sun, and at mid-eclipse leaves an annulus, a ‘ring of fire’ around the Sun as this animated graphic is showing.
Note, I have brightened the side of the Moon facing toward us. During a solar eclipse we would only see a silhouette of the Moon.

   Does our Moon actually go around the Earth as many graphics show? From our perspective on the Earth the Moon appears to circle around the Earth. However, in reality, the Moon orbits the Sun together with the Earth*
*Click here to read my 2006 Scope on the Sky column “The Real Shape of the Moon’s Orbit”. (PDF)

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February Moon at Descending Node and a Solar Eclipse

   Sunday February 26th the new Moon will be crossing the plane of the ecliptic moving south. This is known as the descending node, one of two intersections the Moon’s orbital path (dark green line) has with the ecliptic. The time for new Moon phase 14:59 UT while the time for the node crossing is 8 hours earlier at 6:40 UT. Given the close times for the two events means that there will be a solar eclipse. However the Moon, because of its elliptical shaped orbit, will be at a further distance from the Earth such that it will appear smaller in diameter than the Sun appears. This means that at mid-eclipse, or totality, the Moon will not completely cover the Sun, instead there will be a ring of sunlight around the Moon. The ring of sunlight is called the annulus and so this is an annular solar eclipse. The eclipse will be visible from parts of southern Argentina and western central Africa.
annular-eclipse-ani   On my birthday in 1994 I was ‘honored’ to not only have an annular solar eclipse on that day but the eclipse path, the path of annularity, crossed right over where I live southeast of Kansas City Missouri. This animation is of the May 10th annular solar eclipse.


Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to go to bobs-spaces.

September Annular Eclipse

node-close_up   The solar eclipse on Thursday September 1st, will have been brought to us by the nodes. No the nodes are not a scientific nor a musical group, but rather the nodes represent an intersection between the orbital path of our Moon, or another planet, with the Earth’s orbital path, the plane of the ecliptic.
   There are two nodes or intersections, the ascending node and the descending node. There are two nodes because the planets as well as our Moon do not orbit the Sun on the same level, or plane as does the Earth. Their respective orbits are inclined (tilted) away from the plane of the ecliptic by varying amounts such that they will at times appear below or above the plane of the ecliptic. There will be two times each orbit around the Sun where the planet or our Moon will be on the plane of the ecliptic as it crosses moving from below setting up the ascending node or from above toward below, setting up the descending node.
   So what is the significance of the nodes? The significance is all about timing. If the time of the new Moon phase, for example, occurs at or near the time for a node crossing then there will be a solar eclipse. Remember that at this moment the Moon is on the plane of the ecliptic and is more or less directly between the Earth and the Sun. More importantly, if the times are exact or very close there will be either a total solar eclipse or an annular solar eclipse. 29april-annular_eclipse-ani   During an annular eclipse the Moon is somewhere near its apogee, or most distant point for that particular orbit. This annular eclipse happens 5 days before the Moon reaches apogee on September 6th but the Moon is still far enough away so that its apparent diameter is less than the Sun’s apparent diameter. Both are around 0.5o or 30′ in apparent diameter, however for this annular eclipse the Moon will be about 3% smaller and not be able to completely cover the Sun at mid-eclipse. Instead at mid-eclipse there will be a ‘ring of fire’, the annulus, around the Moon.
   Thursday September 1st the new Moon phase is at 9:03 UT and the Moon is at its ascending node about 6 hours later at 15:27 UT. The Moon makes first contact with the Sun at 6:23 UT; maximum or mid-eclipse is at 9:06 UT; and the eclipse officially ends with last contact at 12:00 UT.
   To sort of complete this story, if there is a solar eclipse, no matter how total or less than total, there will be a lunar eclipse two weeks away at full Moon phase. Eclipses occur in pairs so this pair will be completed with the penumbral lunar eclipse at full Moon on September 16th.Moon Grazing the Earths ShadowFull Moon on September 16th is at 19:05 UT, about 19 hours after the Moon is at its descending node, 11:57 UT September 15th. Because of the time difference, the angle the Moon follows through the Earth’s shadows does not cross the dark inner umbral shadow but rather only takes it across the less noticeable outer penumbral shadow. Unless you knew about it you may not notice a slight dimming of the reflected moonlight.

   For an outstanding web site about all eclipses including information for these two eclipses go to the Hermit Eclipse web site.

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to go to bobs-spaces.

Solar Eclipse – Not for the USA — Actually It Was!

Click on picture to see full size original

Click on picture to see full size original

   4 November: Not sure if I owe an apology or just say “My bad!” but clearly I got my description of the solar eclipse wrong. It was visible shortly after sunset for many along the U.S. eastern coastline as this picture shows from New York City taken by Chris Cook.

   On Sunday 3 November the rising Sun and new Moon as we see them from Earth will intersect or be aligned so that the Moon pass in front of the Sun briefly giving us a solar eclipse. However the circumstances for this solar eclipse are such that the eclipse starts as an annular eclipse where the Moon’s disk silhouetted against the Sun will not completely cover the Sun at the moment of mid-eclipse. This type of eclipse, a combination annular and total, can happen at either sunrise or sunset when the Moon’s umbral shadow does not quite reach the Earth’s surface. However for this eclipse very shortly after sunrise, less than one minute later, the Moon’s disk covers the Sun giving rise to a total solar eclipse for the duration of the eclipse.

   At sunrise along the parts of the east coast of the United States the eclipse will already be in progress and will really not be one that the U.S.A. should get ready for. Use the NASA prepared eclipse map for a ‘google-like’ interactive map that shows the eclipse path. Click anywhere on the map to get viewing information, if any, for that location clicked on. africa-eclipse-aniAs the map shows the Moon’s shadow follows a path that begins in the North Atlantic Ocean and ends on the east coast of Africa.
   Best viewing of this eclipse, at or near mid-eclipse, will be for the residents of western Africa at around mid-day local time. This animated graphic shows the eclipse as it would be seen from the west coast of Africa in the city of Dakar, a coastal city in Senegal. At mid-eclipse nearly 80% of the Sun will be covered.

eclipse-ani   What cities in the United States are involved? None. Click here to see or download a PDF document that shows a table listing local circumstance times for the eclipse. As the table shows, for all of the United States cities listed, the eclipse is already in progress and the Sun is at an altitude of 0 degrees – on the horizon. From the eastern coast of the United States maximum eclipse actually occurs before sunrise and the eclipse more or less is over within the next 30 minutes or so – which is about the time for local sunrise.

   Click here to see a static map of the eclipse path that includes contact times.

telescopeClick here to go to the Qué tal in the Current Skies web site for more observing information for this month.

Solar Eclipse

eclipse animation   Friday 10 May the new Moon will pass between the Earth and Sun setting up the circumstances for a solar eclipse. However this solar eclipse, is an annular eclipse, the type where at mid-eclipse the Moon does not completely cover the Sun as this animated graphic shows.
total   Most are probably familiar with a total solar eclipse as this graphic shows. The disk of the Moon has completely covered the disk of the Sun blocking out everything except the Sun’s corona. Typically during a total solar eclipse the apparent size of the Moon and Sun are essentially the same or the Moon appears larger than the Sun so that at mid-eclipse the sun is completely covered by the Moon.

   The difference between these two solar eclipses has to do with the shape of the Moon’s orbit. It is elliptical and that means that the Moon is not always the same distance from the Earth were it following a circular orbit. Each month the Moon reaches apogee, the farthest it will be from the Earth that month, and perigee, when the Moon is closest. So, if the new Moon occurs at or near apogee, when the Moon is farthest from the Earth, the Moon will appear smaller than the apparent size of the Sun. And if this also happens when the three, Earth, Moon, Sun, are aligned then we have the settings for an annular solar eclipse.

   The date for this eclipse has some personal meaning to me as did the solar eclipse last year that was also on May 10th so I wrote about the eclipse and something called the Saros Series in a recent Scope on the Skies column. Click here to download a copy of my April-May Scope on the Skies column about the eclipse and the Saros Cycle.

   Click here to go to the Qué tal in the Current Skies web site for more observing information.