Skywatch April 2005

Skywatch Line for Friday, April 15, through Sunday, April 17, 2005

By Alan French

On Saturday, April 16, there will be a celebration of National Astronomy Day, at the Albany Heritage Area Visitors Center  & Henry Hudson Planetarium.  Astronomy Day programs will be held from 2:00 PM until 4:00 PM.  There will be a variety of activities for children, and a planetarium show.  Call the center at 434-1217 for further details.

The moon was at First Quarter phase at 10:37 on Saturday morning.  The term First Quarter Moon may seem confusing since it is obvious that more than one-quarter of the moon’s face is lit.  Instead,  First Quarter refers to the fact that the moon is one-quarter of the way around the Earth as seen from the sun.  When the moon is at First Quarter phase, it appears about half lit.

Near First Quarter, the moon is well placed for viewing during the evening. A few features are visible even to the unaided eye.  Most obvious is the terminator, the line between the light and dark portions of the moon.  Right now, this is the line that shows where sunrise is occurring on the moon. The terminator is creeping very slowly to the left across the face of the oon, but within the course of one night its progress usually goes unnoticed to the naked-eye observer.  If, however, you look at the moon again tomorrow night, you should be able to see a noticeable shift of the terminator to the left from tonight's position.

It is also quite easy to notice distinct light and dark areas on the moon. The dark areas are called maria (MAR-ee-uh) which means "seas" in Latin. Galileo and other early astronomers assumed that the maria were bodies of water.  We now realize that there is no water on the moon.  The maria are actually dark and relatively smooth plains caused by ancient lava flows that spread over the floors of huge impact basins.

The bright patches on the moon show us places where mountains and craters are found.  Although these highlands make the moon appear quite brilliant, the moon's surface is actually rather dark.  On the average, the moon only reflects about 7% of the sunlight that falls on it.  This means that the moon's surface is approximately as dark as an asphalt parking lot.

When you turn a pair of binoculars toward the moon, the view is wonderfully improved.  If you can support the binoculars steadily, a few dozen craters and mountain peaks become clearly visible.  Details are most obvious along the terminator.  Since that is the sunrise line, objects near it cast long shadows that make them stand out in bold relief.  Any telescope will improve the view further, and you may find the sharpest view is at one of your lower powers.

The Albany Area Amateur Astronomers hold monthly Star Parties during much of the year.  The first two Star Parties "west" are scheduled for this weekend.  Unfortunately, the weather does not sound promising.  If the weather unexpectedly improves, there will be a Star Party at 8:00 PM on Friday night at George Landis Arboretum in Esperance.  There will be another at 8:00 PM on Saturday night in Indian Meadows Park in East Glenville.  They will not be held if the skies are mostly cloudy, and may be canceled if the grounds at either location are exceptionally wet.  Call 374-8460 for directions, status, and conditions if the skies do clear either night. Future Star Parties will be publicized on the weekend Skywatch Line.

 This weekend we set our clocks ahead one hour for daylight savings time. Set your clocks ahead one hour before going to bed on Saturday, or after getting up on Sunday morning.  Amateur astronomers are not generally fond of daylight savings time.  Because the Sun is well north of the equator in mid-summer, it does not get truly dark until after 10:00 PM, so public Star Parties start at a rather late hour for many people.

 The Sun now rises around 5:36 AM and sets around 6:23 PM, but these times are pushed ahead an hour by Sunday and the start of daylight savings time. The Moon is at last quarter just before midnight on Saturday, and rises at 2:23 AM Saturday morning.  Around 6:30 AM Saturday morning, you might notice a pair, washed out crescent Moon low in the south.

 Jupiter is at opposition on April 3, which means it is directly opposite the Sun in our skies, and is visible all night.  You will find bright Jupiter low toward the east at dusk, high in the south at midnight, and low toward the west at dawn.  It is the brightest star in that area of the sky, so it is easy to spot.  Jupiter is best observed with a telescope when it is due south and highest in our skies.  Views are steadiest and detail sharpest when the telescope looks through as little of our atmosphere as possible.

 Saturn continues to be well placed for telescopic views, with the ringed beauty appearing due south and highest at 8:40 PM (9:40 PM EDT on Sunday!) Any modest telescope providing a magnification of about 30 power will show the planet's rings, and Saturn is one of the most impressive sights in a telescope.

Skywatch Line for Friday, April 15, through Sunday, April 17, 2005

By Alan French

On Saturday, April 16, there will be a celebration of National Astronomy Day, at the Albany Heritage Area Visitors Center  & Henry Hudson Planetarium.  Astronomy Day programs will be held from 2:00 PM until 4:00 PM.  There will be a variety of activities for children, and a planetarium show.  Call the center at 434-1217 for further details.

The moon was at First Quarter phase at 10:37 on Saturday morning.  The term First Quarter Moon may seem confusing since it is obvious that more than one-quarter of the moon’s face is lit.  Instead,  First Quarter refers to the fact that the moon is one-quarter of the way around the Earth as seen from the sun.  When the moon is at First Quarter phase, it appears about half lit.

Near First Quarter, the moon is well placed for viewing during the evening. A few features are visible even to the unaided eye.  Most obvious is the terminator, the line between the light and dark portions of the moon.  Right now, this is the line that shows where sunrise is occurring on the moon. The terminator is creeping very slowly to the left across the face of the oon, but within the course of one night its progress usually goes unnoticed to the naked-eye observer.  If, however, you look at the moon again tomorrow night, you should be able to see a noticeable shift of the terminator to the left from tonight's position.

It is also quite easy to notice distinct light and dark areas on the moon. The dark areas are called maria (MAR-ee-uh) which means "seas" in Latin. Galileo and other early astronomers assumed that the maria were bodies of water.  We now realize that there is no water on the moon.  The maria are actually dark and relatively smooth plains caused by ancient lava flows that spread over the floors of huge impact basins.

The bright patches on the moon show us places where mountains and craters are found.  Although these highlands make the moon appear quite brilliant, the moon's surface is actually rather dark.  On the average, the moon only reflects about 7% of the sunlight that falls on it.  This means that the moon's surface is approximately as dark as an asphalt parking lot.

When you turn a pair of binoculars toward the moon, the view is wonderfully improved.  If you can support the binoculars steadily, a few dozen craters and mountain peaks become clearly visible.  Details are most obvious along the terminator.  Since that is the sunrise line, objects near it cast long shadows that make them stand out in bold relief.  Any telescope will improve the view further, and you may find the sharpest view is at one of your lower powers.

The Albany Area Amateur Astronomers hold monthly Star Parties during much of the year.  The first two Star Parties "west" are scheduled for this weekend.  Unfortunately, the weather does not sound promising.  If the weather unexpectedly improves, there will be a Star Party at 8:00 PM on Friday night at George Landis Arboretum in Esperance.  There will be another at 8:00 PM on Saturday night in Indian Meadows Park in East Glenville.  They will not be held if the skies are mostly cloudy, and may be canceled if the grounds at either location are exceptionally wet.  Call 374-8460 for directions, status, and conditions if the skies do clear either night. Future Star Parties will be publicized on the weekend Skywatch Line.

 This weekend we set our clocks ahead one hour for daylight savings time. Set your clocks ahead one hour before going to bed on Saturday, or after getting up on Sunday morning.  Amateur astronomers are not generally fond of daylight savings time.  Because the Sun is well north of the equator in mid-summer, it does not get truly dark until after 10:00 PM, so public Star Parties start at a rather late hour for many people.

 The Sun now rises around 5:36 AM and sets around 6:23 PM, but these times are pushed ahead an hour by Sunday and the start of daylight savings time. The Moon is at last quarter just before midnight on Saturday, and rises at 2:23 AM Saturday morning.  Around 6:30 AM Saturday morning, you might notice a pair, washed out crescent Moon low in the south.

 Jupiter is at opposition on April 3, which means it is directly opposite the Sun in our skies, and is visible all night.  You will find bright Jupiter low toward the east at dusk, high in the south at midnight, and low toward the west at dawn.  It is the brightest star in that area of the sky, so it is easy to spot.  Jupiter is best observed with a telescope when it is due south and highest in our skies.  Views are steadiest and detail sharpest when the telescope looks through as little of our atmosphere as possible.

 Saturn continues to be well placed for telescopic views, with the ringed beauty appearing due south and highest at 8:40 PM (9:40 PM EDT on Sunday!) Any modest telescope providing a magnification of about 30 power will show the planet's rings, and Saturn is one of the most impressive sights in a telescope.

This is the Skywatch Line for Monday, April 11.

The Sun sets tonight at 7:33, with nightfall happening at 9:14 PM. The Moon is already up and sets at 11:08 PM.

Dawn breaks at 4:37, and ends with sunrise at 6:18.

Tonight’s sunset is an interesting time for sky watchers. Some of most recognizable objects are visible either at sunset, or shortly thereafter.

As the sky darkens, a thin crescent Moon rides high in the southwestern sky. Since the angle of the Sun is rather steep, this is an ideal time to observe Moon’s cratered surface. As the sky darkens to night, look to the Moon’s right. Only a degree away are the magnificent Pleiades; this is a group of stars that form a mini dipper. Binoculars are ideal to appreciate the true beauty of this group; telescopes have very narrow fields of view. However, with dark skies and good telescopes, it is possible to see wisps of the gas clouds that gave birth to this group.

About the same time that the Moon becomes visible, Saturn pops into view. Saturn appears high in South, in the constellation Gemini. Saturn still forms a broken line with the twin stars of Castor and Pollux.

At nightfall, the telescope shows Saturn’s rings in all their glory, with an added attraction. Saturn is now at quadrature. This means that Saturn, Earth and Sun form a ninety-degree angle. This angle throws Saturn’s shadow on the rings. A sight to behold!

While Saturn attracts attention in the South, Jupiter has already risen in the East. Jupiter just passed opposition, which means that it rises at sunset and sets at sunrise.

Dawn skies offer the chance to see two planets for the price of one! Mars rises shortly before dawn. Though low in the East, it is bright and red amid the dim constellation Capricornus. However, much dimmer Neptune rises with it and lies a bit more than a degree away. Both planets fit in the same binocular field and finder scope field. Neptune should appear as a green “star” near the Red Planet.

Clear Skies

Joe Slomka

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