Heads UP! for September 2010

Heads UP!  for September 2010

Venus calls for us to pay attention to the western twilight where her dimmer brothers Saturn and Mars do a fade out, hiding behind the Sun’s glare.  Jupiter makes his grand entrance, inviting any optical aid to visualize the giant planet and his four brightest moons.

Western Sky Just After Sunset

Venus is about as bright in the sky as she gets, but you’ll need a clear view of the horizon to see her.  Your fist held at arm’s length will cover the distance between the horizon and Venus.  You’ll see that Venus is off to the left of the brightest part of twilight.

On September 1st, Mars and Venus make a great sight in binoculars with Virgo’s alpha star, Spica, between them.  So, aim your binoculars in the direction of Venus and you’ll see brother Mars dimly in the same view.  Saturn is harder to find off to the lower right and slips off into bright twilight by the middle of the month.  Mars seems to fight the flight behind the sun, as he continues to set after the Sun though the end of the year.  But by the end of the month, Mars, is also deep in the solar glare. But, until then, Mars shyly hangs out in the bright twilight near Venus’ dazzling radiance.  Check out a plot of the position of the planets in the solar system and you’ll see how the Earth is moving around the opposite side of the Sun from Saturn and Mars.

In the meantime, can you find Venus before sunset?  Earlier means easier to see in a telescope against a brighter sky, with less atmosphere and haze in the way.  If you have a telescope and can put it in the shade to block the dangerous sunlight, you can check out Venus’ thinning phase while the planet’s overall size increases as it races around the sun and swings closer to Earth.

Jupiter the King Rules the Night

The Earth makes its closest approach to Jupiter this month.  Ok, maybe 370 million miles isn’t close, but Jupiter looks large in any scope.  He’s that really bright star rising in the east after sunset.  And this is the best time to check out Jupiter’s four brightest moons, which should be visible in any telescope and in almost any pair of binoculars.  In a small scope, can you see that Jupiter has one darker band.   Usually there are two bands, but one has disappeared.  In a larger scope, the “Great Red Spot” is visible on occasion.  Jupiter rotates once every 10 hours, so this giant storm can glimpsed only for a few hours every day.  The GRS is predicted to be on our side of Jupiter during our Westchester Astronomers’ September 4th observing night.  The spot has been redder ever since the brown belt, usually found in its area, disappeared.

Balancing an Egg?

The autumnal equinox occurs at 11:09pm EDT on the 22nd.  People try to balance an egg on its end at the time of the equinox.  There aren’t any cosmic forces make this trick easier at that time.  Sprinkling salt on the table helps at any time of year.

Subway Astronomy is Back !

In late September and for the month of October, it’s an opportunity for those poor souls who have to catch an early train or subway to have something to look at in the sky while they are waiting.   From mid-September until daylight time ends on November 7th, darkness lingers later in the morning, making it a good time for Subway Astronomy.

People who take the early morning train or subway from elevated platforms get to see Mercury between 5:30 and 6:00am in the last half of September in the area of brightening in the eastern sky.  Mercury doesn’t get farther from the horizon than the width of your fist held at arm’s-length, but it’s easier this month to see than most of the time.  Two fists up is the bright star Regulus, as Leo the lion emerges from behind the Sun.

If early morning Subway Astronomers turn their backs on Mercury, Jupiter beams brightly very low in the opposite part of the sky.

Look Up for the Moon

The Moon makes a splendid appearance high in the morning sky in the first week of September and again in the first week of October, inviting early risers to picture the Moon against the bluing sky.  Most of us will more readily check out the Moon around the first quarter, in the evening sky around mid-month.  At that time, the rough terrain is highlighted along the edge of the sunlit section.  However, the Moon ‘rides low’ in the evenings at this time of year, frustrating those of us whose houses are bounded by tall trees.

Uranus, a Naked Eye Planet?

Uranus is within a degree or so of Jupiter this month, making it an excellent opportunity for those of us who don’t get to see the outer planets to find this almost naked-eye planet in the same telescopic field.  See the diagram (below).  I’ve labeled a few days along the path to provide a rough idea of which way Uranus is from Jupiter during this month.  They should be in the same view in binoculars and should just fit inside the view when using a low power eyepiece on your telescope.  Does Uranus look different from the nearby stars?

[Last night (August 26) Jupiter’s moons looked like a chain of sparkling glitter off to one side of Jupiter in my 8×25 binoculars.  There was a star above Jupiter than can be mistaken for Uranus.  Uranus is further to the right of Jupiter into the first week of September.]

Jupiter and Uranus – Magnified view (attached)

Use this chart to find Uranus from Jupiter in the evening hours

for dates in September.  Interpolate for dates in-between the labeled dates.

Try viewing this scene in JPL’s Solar System Simulator on the Internet.  Fill in the request for to ask for a view of Jupiter, from Earth, then set the field of view for five degrees.  You’ll see where Jupiter, Uranus and background stars are in a view you can see with binoculars.  If you set the time and date, and zoom in by setting a field of view of 0.5 degrees, you can see where Jupiter’s moons are.  Make sure you set the time for four hours ahead of our time (for example 8pm our time on September 1st is 12 midnight (00 hours) on September 2nd in the SSS), since the program uses Universal Time, also known as Greenwich Mean Time.  Click the box for ‘extra brightness’ to make the moons easier to see on the output.

The International Space Station, often nearly as bright as Venus, is visible for up to four minutes at a time in the post-sunset sky from now until September 15th, then the ISS is visible in the pre-dawn skies from September 28th through October 20th.

Only two launches left for the Space Transportation System – November 2010 and February 2011.  Congress is considering legislation to allow one more launch in June 2011.  Then, there’re off to the museums.

Got binoculars?

Whatever the size or quality of your binoculars, just take them outside on a clear night and point them at a bright star overhead.  Focus them until the star is as tiny a pinpoint as you can reasonably make it.  Then find the moon or Jupiter and see what detail you can see.  Give yourself a few minutes to really look.  Relax your eyes and let the scene come to you.  Lean the binoculars against a tree, the house or a car to help hold them steadier.  When you get a chance, lay down in a lounge chair or picnic bench and just look generally overhead.  Wander around slowly with your binoculars, noting bunches of stars or areas with more stars or less.  Whatever you get to look at, let me know what you can see and what size your binoculars are** see below for information on what those numbers mean on your binoculars.

** Binoculars – What do those numbers mean?

What size are your binoculars?  Just like clothing has size tags, most binoculars are ‘tagged’ with their size, but the size is stamped directly on the binoculars.  Look and you should see something like ‘7 x 35’.  The second number is the size of the opening where the light comes into the binoculars – the larger end.  This number is the diameter of the lens in the opening in millimeters.  So 25 would be 25 millimeters (mm), which is about one inch.  The larger this lens is, the more light you get to see, more light means fainter objects are visible.  And, as a bonus, the larger the opening, the more detail you can see.  That’s helpful when looking for details on the Moon or trying to pick out the moons of Jupiter.

The first number is the magnifying power of the opening you put next to your eye – the eyepiece.  So 10 x50 makes objects look larger than 7 x 50.  And 7×50 lets you see fainter objects than 7×35.

The downside of more power is a narrower picture in your eyepiece.  The downside of a larger opening lens is that it’s heavier and harder to hold still.

The best binoculars depend on what you use them for.  7 x 50 tends to be the best combination of low weight, wide field of view and bright enough to see fainter objects.  7 x 35 is lighter in weight, but still good for most viewing.  For watching the football game at the stadium, even lower powers can allow a wider view, and a smaller lens for the incoming light can be used since the field is bright enough that you don’t need extra light-gathering capacity.


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