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

WHAT'S UP?

by Ronald A. Leeseberg, the Star Geezer

May 2011 - Vol. 15 No. 5

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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.

As the days lengthen, the stars of the Winter Triangle asterism disappear into the evening twilight. Now another asterism, the Big Dipper (Ursa Major), is well placed for observation. Follow the curve of its "handle" to the bright star, Arcturus (Bootes) and continue on to another bright star, Spica (Virgo) in the SE. Regulus (Leo) is still high in the SW while Vega (Lyra), one of the stars of the upcoming Summer Triangle, becomes visible in the NE. Don't confuse bright Capella (Auriga) with the pale yellow planet, Saturn, as it moves along the ecliptic in the NW. Look for my favorite spring constellation, Corvus, with its rather dim but distinctive kite-shaped asterism low in the SSE. Later this month look for the familiar "W" shaped asterism of constellation Cassiopeia high in the N. If you follow a "line" along the end side of the Big Dipper's "bowl" up about half way up to Cassiopeia, you will discover Polaris (Ursa Minor). This is the North Star, about which the rest of the stars appear to rotate.

MERCURY is one of the four dawn planets this month. It rises only 5 degrees above the E horizon and will probably be visible only in binoculars. Bright VENUS stands a few degrees above Mercury. Dim MARS appears about about 10 degrees above the E horizon. It will be "paired" with the much brighter JUPITER. For the first 10 days of the month these planets will all appear in a single field (view) of most binoculars. During the early part of the month, the crescent MOON will also be visible among these planets. SATURN is this month's only bright night time planet. It becomes visible about 40 degrees above the SE horizon at dusk, moves S by midnight and sets in the W about an hour before dawn. It "rings" are open about 8 degrees to our line of sight. Through even a small telescope, the ring's Cassini Division should be visible. It is a dark zone that divides the the rings approximately in half and is caused by "Shepard Moons" whose gravity "clears" a path through the ring. A small star-like body some distance from Saturn is its largest Moon, Titan. The Eta Aquarid meteor shower occurs early in the month.

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
01
Look E at 3 AM to see a conjunction (less than a degree) between a very narrow crescent Moon and Jupiter.
04

Look WNW at dusk to see a pseudo-conjunction of the crescent Moon and M45, the famous open star cluster, the Pleiades, of Constellation Taurus.

06
The Eta Aquarid meteor shower peaks early in the morning. Although it is one of the best of the year, its radiant (point at which the meteors seem to originate, the Constellation Aquarius, is only 20 degrees above the ESE horizon so one can expect only about 25 events/hour from a dark site with a good view of the horizon. Fortunately the Moon will have set by midnight.

This shower is the result of our atmosphere "ramming" through dust deposited by Comet Halley as it passed through the Earth's orbit around the Sun. It is interesting to note that October's Orionid meteor shower is the result of Earth's passage through the same dust stream ejected by Comet Halley.
10
Look E to see a close conjunction (2 degrees) of Mercury and Jupiter at about 7 PM. Unfortunately, the sky may be too bright to see this event.
11
Look E to see a conjunction (6 degrees) between bright Venus and Jupiter at 5 AM. This event will not repeat until August, 2014.
20
At dawn, Venus forms a tight right triangle (triple conjunction) with Mercury (below) and dim Mars (to the left) in the E sky.
30
Look for a conjunction (4 degrees) of the Moon and Venus at midnight.
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Lunar Almanac for May 2011

Phases of the Moon Phase and Date(s)

Best viewed before local midnight

New
03

Deep Space Objects

1st. Qtr
10

Planets & Moon

Full
17

Moon

Last
Qtr 24

Deep Space & Planets

Topic of the month: Eyepieces II: Special Eyepieces and Useful Accessories

 

Last month we ended our discussion of eyepieces before we got to the Barlow lens system. (Please review last month's article showing a diagram of a Barlow lens). The Barlow lens, although not really an eyepiece, serves as a "focal-length amplifier". In effect, the unit pictured above doubles the power (or magnification) of any eyepiece attached between it and the telescope. For example, my 40X eyepiece becomes 80X when attached. Thus, I now have two eyepieces! In addition, the Barlow-eyepiece combination provides a sharper view at the edge of its field and, more importantly, provides increased eye relief over a single lens of equal power. This is very important when working with a large group since viewing is much easier.

focal reducer with extension

A Focal Reducer, on the other hand, works exactly opposite the Barlow. Its main use, for me, is to expand the image of my eyepiece camera to better fill the screen of this NetBook computer, allowing a person who can not reach the telescope's eyepiece to still see the object in its focus (provided it is bright enough.) The focal reducer will be discussed again when we get to imaging for the street astronomer.

As a street astronomer, I do not often used two other accessories, the coma corrector and the "zoom" eyepiece. I find the zoom eyepiece to be too difficult to use, especially with children. Changing magnification usually moves the telescope off target, wasting precious time. Zoom

The Coma Corrector, as its name implies, corrects comma-like star images at the edge of the field. This can occur when using large, "fast" (wide angle) reflectors. (Since I use only refractors as a street astronomer, a come corrector is not needed.)


Here the Binoviewer is attached to my 8" Celestron telescope, located in my Ohio observatory. It provides mind blowing low power stereoscopic images. Since it is portable, it can be attached to any telescope. It's great when viewing the Sun's Sunspots or our Moon features. (Since it is quite heavy, telescope balance can be a problem.)



Some eyepieces have a pattern or reticule etched on a thin optical glass "window" superimposed of its field of view. They can be illuminated (above) of unilluminated (below) and are commonly also found in a telescope's finder. Although they can be very complex, I find the "bull's-eye" and "cross-hair" the most useful for my purposes.

--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. Images used in this installment of "Whats Up?, Ron"are ©2011 by Ronald A. Leeseberg.

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