Whats Up, Ron? is a monthly almanac for Northern American astronomersastras

WHAT'S UP?

by Ronald A. Leeseberg, the Star Geezer

August 2011 - Vol. 15 No. 8

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Features: Calendar | Lunar Almanac | Monthly Topic

This Month's Night Sky - NOTE: The next paragraph describes the sky as it appears at 10 pm EST (11 pm EDT) near mid- month. The sky also looks this way at 11 pm EST (midnight EDT) during the beginning of the month and at 9 pm EST (10 pm EDT) by month's end.

Angular Measurement Review: It is interesting to note that the relationship between the angle subtended by combinations of fingers on your fully outstretched arm are the same for all viewers. This is due to the fact that the hand's size is proportional to the arm's length. A shorter arm is attached to a smaller hand while a longer arm is attached to a larger hand, thus the angle measured remains the same. If you hold your arm fully outstretched, your little finger, when sighted down your arm, is one degree wide. Your three middle fingers is five degrees, your fist, 10 degrees, and the distance between your little finger and your pointer finger is 15 degrees no matter what your age or size.

The Summer Triangle asterism is high as the sky darkens. The reddish glow of Arcturus (Bootes) sinks towards the W horizon while the stars of another asterism, the Big Dipper (Ursa Major), dip low in the NW. You may see Antares, also reddish,(Scorpius)in the SW. Very low in the SE, Formalhaut [FO-mel-hote](Piscis Austrinus)[PIE-sees OS-tra-nis], rises all alone. In the E, the Great Square of Pegasus rises and is followed by the stars of Andromeda. You may also see Capella (Auriga), high in the NE.

MERCURY passes between the Sun and the Earth (inferior conjunction).  By month’s end it will have returned to the early morning E. sky.  It will be visible from the 17th of this month through the 18th of next month.  VENUS, the “morning star”, passes from view at mid-month from the E. early morning sky as it “hides” behind the Sun (superior conjunction).  It will return to the evening sky as the “evening star” in October.  The next and final conjunction of this century will occur on July 5-6, 2012.  It will cast its shadow across the Sun’s face during this transit.  Plan now to safely observe this historic event  Don’t miss it!!  MARS, visible in the E early morning sky, is still too distant to show surface detail in most amateur telescopes.  It rises in the NE after midnight and disappears in the Sun’s glare.    JUPITER rises in the E before midnight and glows brightly all night, finally disappearing in the S as the Sun rises.   Only the Sun and the Moon shine more brightly this month.  Lovely SATURN appears in the SW sky at Sunset.  Its rings tilt some 9 degrees towards us and will continue to widen during the rest of the year.  It sets in the W well before midnight.  Any telescope or binoculars capable of showing its rings will also show its biggest and brightest Moon, Titan.  This year’s PERSEID METEOR SHOWER will be disappointing since it peaks on the same day as the full MOON.

Calendar of Events

NOTE: For those observers not in the ET zone, convert the calendar times to your zone's time by subtracting one hour for CT, two for MT and three for PT. Don't forget to adjust for Daylight Savings Time when necessary by subtracting one hour from your planisphere's time.; Dawn and dusk times must also be corrected. See your local newspaper, TV news, or cable TV's Weather Channel for sunrise and sunset times. Unfortunately some of these events may occur during daylight hours in your area.

DATE EVENT
03

Look WSW, about an hour after Sunset, to see creamy Saturn shining about 10 degrees directly above the crescent Moon.

04

Look WSW, about an hour after Sunset, to see a pseudo-conjunction of the crescent Moon and the bright star Spica (Virgo).

10

Binoculars and telescopes show the occultation (covering) by the gibbous Moon, of the bright star, Pi Sagittarii (Sagittarius). Browse “skyandtelescope.com/aug2011occult” for further details.

13

The Perseid Meteor shower peaks between midnight and Sunrise. Unfortunately the bright light of the full Moon will blot out all but the brightest meteors. Under better conditions, one could expect to see up to 100 meteors/hour…this year you will be lucky to see 20/hour! Try to view during the early morning hours when the shower’s radiant (between Perseus and Cassiopeia) is higher in the sky and the full Moon, lower. Also observe where a tree or building blocks the Moon’s glare. You might view a few days before the peak.  On the 11th, the Moon sets before 4 AM giving you about a half hour before the sky brightens as the Sun rises. Although the meteor count/hour will be lower, the Moon won’t interfere.

19
Look ENE at 5 AM to see a conjunction (5 degrees) of Jupiter and the Moon at 9 PM.
20

Look ENE around midnight to see a pseudo-conjunction (5 degrees) of the gibbous Moon and M45, the Pleiades, the bright open star cluster of constellation Taurus.

25

Look E, about an hour before Sunrise, to see a conjunction (3 degrees) of reddish Mars and the crescent Moon. The Gemini “twins”, Castor (above) and Pollux (below) are off to the left.

27
Look E, about 45 minutes before Sunrise, to see dim Mercury, very low on the horizon, form a right slanted arc that includes the crescent Moon and finally, the bright star Procyon (Canis Minor).
28
If you have access to a telescope, find Jupiter in the E sky at2:45 AM. Now watch Ganymede’s (one of its Galilean Moons)shadow, crawl across Jupiter’s face.
31

At dusk, look for a neat triangle formed by the thin crescent Moon and Saturn (upper right) and the bright star, Spica (upper left).

Look WSW, about an hour after Sunset, to see creamy Saturnshining about 10 degrees directly above the crescent Moon.This is a repeat performance of the event of the 3rd.

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Lunar Almanac for August 2011

Phases of the Moon Phase and Date(s)

Best viewed before local midnight

New
01

Deep Space Objects

1st. Qtr
08

Planets & Moon

Full
15

Moon

Last
Qtr 28

Deep Space & Planets

Topic of the month: Spectroscopy

It is always amazing to me when I consider that nearly all that we know about deep space objects (those, like stars, that are beyond our solar system) has come from light that has passed through a SPECTROSCOPE.

From the spectra of stars we can deduce their chemical composition, temperature, motion through space as well as the speed of their rotation, etc.  (Attached is a more detailed explanation of stellar spectroscopy. DON'T PANIC! Many years ago I wrote this tutorial for junior high schoolers to use in conjunction with a paper, razor blade and bit of grating sheet used to make functioning spectroscopes as possible science fair projects. This document is available upon request, send e-mail to Aastra using the contact information link.)

Now the amateur can also study star spectra by using a clever eyepiece spectroscope made by Rainbow Optics: “http://www.starspectroscope.com/index.html

The lens cell in the upper right fits over the telescope eyepiece (ocular) and the grating cell (below the lens cell in the image) screws into the bottom of the eyepiece.  The three empty cells (to the left) are "spacers" used to bring the spectra produced into sharp focus, depending on the mechanics of the telescope.

An interesting observation is to randomly point the telescope and examine the image produced when the spectroscope has been installed.  Without the spectroscope, all one can see are dots of light. With the spectroscope, only the stars produce little colored "rainbow" spectra. Planetary nebula (expanding gas clouds from stars that have shed their outer shells) and many other objects, do not produce spectra since their light is monochromatic (of only one color). It makes a nice demonstration.

A daytime demonstration is to point the spectroscope attached telescope at a patch of sky near (not at) the Sun.(Direct unfiltered sun light would nearly instantly destroy the spectroscope’s grating then the observer’s retina!)The spectra produced is that of the Sun’s.

NOTE:  If you have doubts, you can look directly at the sun with the spectroscope attached if you use an appropriate Objective solar filter sold specifically for a telescope.Unfortunately, my filters tend to alter the Sun’s spectra.

--See you next month!
Ron, the star geezer

This installment of "Whats Up?" is ©2011 Ronald A. Leeseberg, encoded by Dawn Jenkins for Astra's Stargate.

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