The REAL OCCULT:

Lunar & Solar Eclipses and Asteroid & Stellar Disappearances Sometimes

Involving Luna

By Dr. Harold Williams

of Montgomery College Planetariumhttp://montgomerycollege.edu/Departments/planet/

Types of Occultations• Lunar Eclipse, • Solar Eclipse, • Asteroidial Occultation,

• Lunar Occultation,– Grazing Lunar Occultation– Planet Lunar Occultation

• Transit of Planet across the Sun– Transit of Mercury (next one November 8, 2006)

– Transit of Venus (June 8, 2004, next one June 6, 2012)

• Planet disappearing behind moon

Lunar Eclipse

• Lunar Eclipse, shadow of the earth gets in front of the full moon at night time.

• When the moon, earth, and sun align in that order at a node.

• The reason we do not have 13 eclipses a year is because the orbit of the earth around the sun, the ecliptic, and the orbit of the moon around the earth are inclined by around 5 degrees, they are not aligned (it would be improbable if they were perfectly aligned instead of being close).

A Total Lunar Eclipse (1)

A Total Lunar Eclipse (2)A total lunar eclipse can last up to 1 hour and 40 min.

During a total eclipse, the moon has a faint, red glow, reflecting sun light scattered in Earth’s atmosphere.

Lunar EclipsesEarth’s shadow consists of a zone of partial shadow, the Penumbra, and a zone of full shadow, the Umbra.

If the moon passes through Earth’s full shadow (Umbra), we see a lunar eclipse.

If the entire surface of the moon enters the Umbra, the lunar eclipse is total.

Solar Eclipse• Solar Eclipse, new moon gets in front of the sun in the day

time. • When the earth, moon, and sun align in that order at a

node. • The reason we do not have an eclipse every month is

again, because of the 5 degree inclination of the orbit of the earth around the sun and the orbit of the moon around the earth.

• Fred Espenak's Eclipse Pages at http:/sunearth.gsfc.nasa.gov/eclipse/eclipse.html, best general scientific source of eclipse maps, dates, and general data for both lunar and solar eclipses. Everyone uses Fred Espenak, he is without peer for specific eclipse information.

• Wendy Carlos Eclipse Pages at http://www.wendycarlos.com/eclipse.html , some of the finest pictures taken by a true artist of solar eclipses and music.

Diamond Ring Effect

Solar Atmosphere Revealed

Solar Eclipses

The sun appears approx. as large in the sky (same angular diameter ~ 0.50) as the moon.

When the moon passes in front of the sun, the moon can cover the sun completely, causing a total solar eclipse.

Solar Eclise Viewing

• While lunar eclipses are inherently safe, Solar Eclipses, the partial phases, are of course dangerous to human eyes. Of course, they are no more dangerous than looking at the sun on any day time that the sun is visible. Toddlers and grasshoppers avoid blinding themselves every day when the sun is visible by not looking directly at it.

• If it hurts don't do it.

• Safe Solar Filters

Solar Filters

Places to get safe solar filters• http://www.tropicalsails.com/shades.htm• http://www.eclipse1999.com/• http://www.weatherman.com/ECLIPSE2000.htm • 301-482-0000 or 301-482-2210 Hands on Optics in

Damascus, MD 20872, http://www.handsonoptics.com . During the total solar eclipse though it is quite safe to look directly at the sun. I have spent a total of 4 minutes looking directly at the sun during two total solar eclipses; and it has not damaged my eyes.

Earth and Moon’s Orbits Are Slightly Elliptical

Sun

Earth

Moon

(Eccentricities greatly exaggerated!)

Perihelion = position closest to the sun

Aphelion = position furthest away

from the sun

Perigee = position closest to Earth

Apogee = position furthest away from Earth

Annular Solar Eclipses

The angular sizes of the moon and the sun vary, depending on their distance from Earth.

When Earth is near perihelion, and the moon is near apogee, we see an annular solar eclipse.

Perigee Apogee Perihelion Aphelion

Annular Solar Eclipses (2)

Almost total, annular eclipse of May 30, 1984

Conditions for Eclipses (1)

A solar eclipse can only occur if the moon passes a node near new moon.

The moon’s orbit is inclined against the ecliptic by ~ 50.

A lunar eclipse can only occur if the moon passes a node near full moon.

Conditions for Eclipses (2)

Saros cycle: 18 years, 11 days, 8 hours

Eclipses occur in a cyclic pattern.

Asteroidial Occultation• An asteroid orbiting the sun sometimes

get in front of a star as seen from the earth.

• This type of Asteroidial occultation is used to measure the size of the asteroid

• and to tell whether it has an any moons orbiting the asteroid.

• Here the alignment is earth, asteroid, and star in that order.

• http://scienceworld.wolfram.com/astronomy/Asteroid.html

29 October 2005 790 Pretoria

Asteroidial Occulation Updates

• http://www.asteroidoccultation.com/

Lunar Occultation• Moon traveling in it orbit around the earth occults stars. • When it occurs near the top or bottom of the moon this is

called a Grazing Lunar Occultation. As the star gazes behind the lunar edge profile the star appears to go out and then back on when it appears from a deep lunar valley.

• Grazing lunar occultations are used to determine the lunar edge profile very accurately so that when solar eclipses happen and the last part of the photosphere appears in deep lunar valleys, forming Baily's Beads. The timing of these Baily's beads can be used to tell whether the sun is getting larger or smaller over time, by comparing Baily's beads timing from solar eclipse to solar eclipse. This is basic long term research that answers extremely important critical questions about the size of the sun and future changes in our climate on earth. Global warming or cooling and all of that sort of stuff.

• Moon can get in from of a planet like Saturn (seen it).

Lunar Occultation Links

• http://www.lunar-occultations.com/iota/iotandx.htm

February 20, 2002 Moon occults Saturn

• http://antwrp.gsfc.nasa.gov/apod/ap020222.html Astronomy Picture of the Day February 22, 2002.

Transist of Venus Across the Disk of the Sun June 8, 2004

• http://www.montgomerycollege.edu/Departments/planet/planet/VenusTransit.html

• http://montgomerycollege.edu/Departments/planet/planet/Mercurytransit2006.html Transit of Mercury across the disk of the sun November 8, 2006.

• http://sunearth.gsfc.nasa.gov/eclipse/transit/venus/Map2012-2.GIF Visibility of June 6, 2012 transit of Venus across the Sun.