Posts Made By: Curt Renz

Here's a link to a nice article on the constellation that dominates our southern sky during summer evenings.

http://news.yahoo.com/news?tmpl=story&cid=96&e=3&u=/space/20050722/sc_space/thewondersofscorpius

I've created an August astronomical calendar that can be downloaded as your computer's desktop background wallpaper or printed to paper. The Moon is the main feature. Information on planetary visibility is included.

To see it, click:
http://www.curtrenz.com/astronomical.html

For those interested in details, read on:

Most of the information on the calendar is topocentric and assumes that the observer is located at the Adler Planetarium in Chicago. Although, it should well serve those in most northern hemisphere locations.

Each daily Moon image is depicted as it would appear on the night of the two dates it straddles. That includes the orientation of the illuminated portion and its relative apparent size. Specifically, a waxing Moon is shown as it would appear midway between sunset and moonset. A waning Moon is shown as it would appear midway between moonrise and sunrise. The effects of earthshine and the oppositional flash are also demonstrated.

The phases shown at the bottom of the page are calculated for more classical and intuitive definitions, rather than the simplistic ones employed in more recent times but before the advent of computers. Dark Moon is the moment during the monthly cycle in which the apparent lunar disk is least illuminated. Full Moon is when the disk is most illuminated. Half Moon comes when the disk is 50% illuminated. The fraction illuminated is printed under each image.

Only the apogee and perigee data are geocentric: kilometers from center of Earth to center of Moon. Otherwise, this information might seem somewhat chaotic as the Earth's rotation causes a daily oscillation of the distance between a surface based observer and the Moon.

Here are the meanings of the planetary visibility tables: For this explanation the horizon has been divided into two halves, eastern and western. A Morning Star is a planet that at sunrise is either above the western horizon or at least 10 degrees above the eastern horizon. An Evening Star is a planet that at sunset is either above the eastern horizon or at least 10 degrees above the western horizon. A Midnight Star is a planet that is above the horizon at local midnight, the time midway between sunset and sunrise (the evening date is posted.) It is possible for a planet to be all of these during a particular night. Lost in Glare means the planet fails to meet any of the previous three criteria and is therefore too close to the Sun to be easily observed.

Very interesting, Michael. Back in 1930 astronomers thought they were searching for a Planet X with 10 times the mass of the Earth. Pluto turned out to be so dim that they assumed it must be as black as coal. It wasn't learned until decades later that Pluto is 1/500 of Earth's mass and quite reflective. It's extreme orbital characteristics are more that of a distant asteroid and not that of a stable major planet. Although for many reasons I am not arguing that it should be designated an asteroid. If astronomers had been alert and not so taken with the notion of a planet being discovered by an American, they might have determined that Pluto belonged to a new class of objects.

Early 19th century astronomers may have been more reasonable. The first asteroid to be discovered was originally classified as a planet. But after several more were found, they realized it would be more sensible to place them in a separate category. Later astronomers might have learned from them and been less eager to simply discover a planet.

Clyde Tombaugh would have impressed me much more as a scientist, if he had questioned his discovery and investigated its characteristics more deeply. If he had done so, we might today be calling Pluto a TBO: Tombaugh Belt Object. That would have given Clyde more lasting and deserved fame. Our understanding of the evolution of the solar neighborhood would have progressed more rapidly. Let's stop placing significance on what our fourth grade teachers taught us by rote, and move to a more rational classification system for objects orbiting the Sun. Emotional attachment is not good science. Pluto must be accepted as one of many KBO's. These latest discoveries may put to rest the argument that Pluto should be classified with the major planets.

Who will be first to spot the New Moon by naked-eye after its conjunction with the Sun on 2005 AUG 05 at 03:05 UT?

This slender young crescent Moon, a day or two old, was traditionally referred to as the New Moon. On the day of conjunction our ancestors called it the Dark Moon. However, most modern calendar makers insist on labeling the conjunction day as that of the New Moon.

We’ve entered the months of the year during which the ecliptic makes a sharper angle with the horizon after sunset for observers in mid-northern latitudes. That makes the spotting of a one-day-old Moon virtually impossible. However, almost everyone should be able to sight it when it is two-days-old. Venus will serve as a guide. It’s that really bright star-like object situated low and almost due west in the very early evening. From Chicago on the 6th after sunset the Moon will be about 13° from Venus in the 4 o’clock direction. The description would be similar for most North American observers.

Since I began this series in 2004 March within several astronomical message boards, the overall champion is Navneeth (SN1987A) in Madras, India with a 2005 January sighting 24:51 hours after conjunction.

Please report your August observation within this thread, including location and time with zone. Even negative results would be interesting. Photos would be especially nice. No prizes, just bragging rights.

I've created a graphic previewing the western sky 25 minutes after sunset on August 6 as seen from Chicago's Adler Planetarium. Nevertheless, the diagram should be useful for most North American observers. To see it, click:

http://www.curtrenz.com/astronomical.html

Then click the small blue button for the "August New Moon Spotting Contest".

The graphic may be removed soon after August 6.

If you missed the evening apparition of Mercury last month, fret not. It will soon be popping into the pre-dawn eastern sky, albeit briefly. It was in Inferior Conjunction between us and the Sun on AUG 05. It will be near its perihelion when it achieves its Greatest Western Elongation of only 18.4° on AUG 23. Nevertheless, the celestial geometry will be favorable for northern observers as the ecliptic makes a broad angle with the horizon. For someone observing from Chicago 30 minutes before each sunrise, Mercury will be above the horizon from AUG 11 through SEP 11 and will reach its greatest altitude of 10.5° on AUG 25. The waning crescent Moon will appear to pass near Mercury on SEP 02. Its greatest brilliance will occur on SEP 04 at Magnitude -2.0. It will then move to Superior Conjunction on the far side of the Sun on SEP 17.

I've created a graphic that illustrates Mercury's morning apparition as viewed from Chicago's Adler Planetarium, although it should well serve most northern hemisphere observers. To see it click:

http://www.curtrenz.com/astronomical.html

Mars is again returning to our evening skies. It will become an especially bright orangish object this fall. No, not quite as close or as brilliant as in 2003, but higher in the sky (for northern hemisphere observers) making for better seeing conditions.

Mars will reach longitudinal opposition to the Sun on November 7. Due to Mars' orbital eccentricity it will approach Earth most closely on October 29 at a distance of 0.46405 AU. On that date it will appear 20.17 arcseconds in diameter with a peak magnitude of -2.4 (similar to Jupiter's brightness when at opposition.) As the Earth passes by Mars in their race around the Sun, Mars will appear in retrograde (reverse) motion from October 1 through December 9.

Mars has been rising earlier each evening and now appears on the eastern horizon around 23:00 local time. Around the date of opposition it will be rising near the time of sunset. I've created a graphic demonstrating the position of Mars in the eastern sky each evening at 23:00 as viewed from Chicago over the next three months. The Moon is pictured in the background. The image should well serve most observers in the northern hemisphere. I made another chart that demonstrates Mars' oppositional loop and retrograde movement in ecliptical coordinates. To see them both, click:

http://www.curtrenz.com/astronomical.html

The Moon is at the period in its 18.6-year cycle of nodes during which it can occult (cover) the Pleiades star cluster (M45) in Taurus. It can be an awesome sight to watch each of the Pleiades sisters blink out one at a time before again reappearing individually. 8)

The brightest star in the Pleiades is Alcyone at magnitude 2.9. The current occultation series of Alcyone began on 2005 FEB 15 and continues every 27.3 days until 2010 DEC 18 (2010 NOV is an exception.)

The observation of each occultation is restricted to certain belts on the Earth. During this early portion of the series and again in the latter portion it will be those in the southern hemisphere who will be in the path of the occultations. During the middle portion of the series, northern hemisphere observers will be favored.

I can’t provide predictions for everyone, but I’ve calculated for those of us in Chicagoland that occultations of Alcyone will occur during nighttime on the following dates:

2006 APR 01
2006 OCT 10
2006 DEC 03
2007 OCT 27 (emersion only)
2008 JUN 30 (emersion only)
2008 SEP 19 (emersion only)
2009 AUG 14

Emersion refers to reappearance. Immersion would refer to the initial covering.

This month during the early morning hours of the 26th, a close passage of the Moon beneath the Pleiades will be seen by many North Americans. I’ve created a graphic demonstrating how it will be viewed from Chicago. To see it, click:

http://www.curtrenz.com/astronomical.html

On 2005 SEP 01 at 21:43 UT geocentrically Venus will pass 1.2° south of Jupiter. That's about 2.4 times the width of the Moon. The bright star Spica in Virgo will appear about 6° away from the pair. The planets will be elongated 39.1° east of the Sun. Venus and Jupiter are normally the two brightest objects in the sky other than the Sun and Moon.

From Chicago the closest approach between the planets will occur at 16:37 CDT during daytime at a separation of 1.2°. In the early evening Venus will be seen below and to the left of Jupiter, still by about 1.2°. Spica will be to their left.

I've created a graphic previewing the grouping as it will be seen from Chicago's Adler Planetarium 30 minutes after sunset on Thursday, although it should well serve most northern hemisphere observers. To see it, click: http://www.curtrenz.com/astronomical.html

I've created a September astronomical calendar that can be downloaded as your computer's desktop background wallpaper or printed to paper. It includes information on the naked-eye planets, Moon and eclipses. A new feature is the posting of planetary events and meteor showers on specific dates.

To see the calendar, click:
http://www.curtrenz.com/astronomical.html

For those interested in details, read on:

The lunar images and planetary visibility tables are topocentric and assume the observer is located at the Adler Planetarium in Chicago. Although, the calendar should well serve those in most northern hemisphere locations.

Each daily lunar image is depicted as it would appear on the night of the two dates it straddles. That includes the orientation of the Moon’s illuminated portion and its relative apparent size. A waxing Moon is shown as it would appear midway between sunset and moonset. A waning Moon is shown as it would appear midway between moonrise and sunrise. The effects of earthshine and the oppositional flash are also demonstrated.

The phases described at the bottom of the page are calculated for more classical and intuitive definitions, rather than the simplistic ones necessarily employed in more recent times but before the advent of computers. Dark Moon is the moment during the monthly cycle in which the apparent lunar disk is least illuminated. Full Moon is when the disk is most illuminated. Half Moon comes when the disk is 50% illuminated. The fraction illuminated is printed under each image.

The apogee and perigee data are geocentric: kilometers from center of Earth to center of Moon. Otherwise, this information might seem somewhat chaotic as the Earth's rotation causes a daily oscillation of the distance between a surface based observer and the Moon.

A grazing occultation is the most interesting variety. It occurs whenever a polar region of the Moon appears to just barely sweep by a star or planet. Observers at the right locations on Earth will see a star winking on and off as it moves behind lunar hills and valleys.

I've calculated that a grazing occultation of the first magnitude (1.1) star Antares in Scorpius will occur at very low altitude in daylight along a narrow strip of the southeastern United States on 2005 SEP 10. Antares can indeed be seen in daylight through a small telescope. This event will be quite a test of observational skill. It may even prove to be impossible, but perhaps worth a try for those who live along the path. Anyone's results, positive or negative, would be an interesting addition to this thread.

On land the graze line runs from Brick Landing, North Carolina to Big Creek, Tennessee. Those located south or west of the graze line will witness an occultation of the star, if it's above the horizon. Those north or east of the graze line will see a close passage, if the star is above the horizon. Those on the graze line will be the lucky ones. Or perhaps they'll be the industrious ones who make an effort to bring their telescopes to the graze line.

As viewed from downtown Miami, Florida there will be an occultation. Immersion will occur at 13:41:30 EDT at Zenith Angle 141.3° when the star will be at an Altitude of 3.3° above the horizon. Emersion will occur at 14:34:43 at Zenith Angle 19.1° and Altitude 12.6°. The Zenith Angle is measured counter-clockwise around the lunar limb with 0° pointing straight up toward zenith.

The apparent disk of the rising waxing Moon will be 42% illuminated. Its lighted portion will appear to the upper right.

Below I've plotted the graze path at one degree intervals of geographic longitude. If you wish to submit a more precise longitude, just reply within this thread and I'll calculate the rest of the data for you.

W 78° -- N 33.66367°
Alt 5.5° -- ZA 71.6°
14:10:47 EDT

W 79° -- N 34.24618°
Alt 4.5° -- ZA 71.5°
14:10:42 EDT

W 80° -- N 34.81938°
Alt 3.5° -- ZA 71.4°
14:10:39 EDT

W 81° -- N 35.38335°
Alt 2.6° -- ZA 71.2°
14:10:38 EDT

W 82° -- N 35.93816°
Alt 1.7° -- ZA 71.1°
14:10:40 EDT

W 83° -- N 36.48390°
Alt 0.8° -- ZA 70.9°
14:10:43 EDT