Posts Made By: Curt Renz

On the evening of Monday 2005 APR 11, Diana's Bow (name for 3-day old Moon) will pass near the Pleiades star cluster. For some southern hemisphere locations this will actually be an occultation. It should really be a pretty sight. If you take a photo, that might make a fine addition to this thread.

I've created a graphic of the event as it will appear 45 minutes after sunset as viewed from Chicago, although it should well serve most observers. To see it click:

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

Then click the small blue button for "Moon Conjuncts Pleiades".

The graphic may be removed soon after April 11.

Venus will soon be returning to our evening skies. Who will be the first to spot her? This observation was important to many ancient cultures. Here is your chance to take part in this ancient ritual. I propose a contest with three categories: Naked-Eye (the true champion), Binoculars, and Telescope. No prizes - just bragging rights.

Please report your sighting within this thread, including your location, date and time with zone. Other details of your observation would be appreciated. Photos would be most welcome. Even negative results would be interesting.

Venus' synodic cycle (time it takes to lap the Earth) is 19.2 months. On 2005 MAR 31 at 03:30 UT Venus was in superior conjunction with the Sun. During the coming months it will grow higher in the evening sky after each sunset. Below are calculations I've made that should help with your viewing. First is an explanation of the six columns.

1) Date (the time is 21:00 CDT or 02:00 UT the following day, except column #6)
2) Elongation in degrees between Venus and the Sun
3) Polar diameter of Venus in arcseconds
4) Fraction illuminated of Venus' apparent disk
5) Stellar magnitude
6) Altitude in degrees at sunset from Chicago

Date--Elon-Diam-Illum--Mag--Alt
04/15 04.2 09.7 0.997 -3.3 02.8
04/20 05.4 09.7 0.996 -3.3 04.0
04/25 06.7 09.7 0.993 -3.3 05.1
04/30 08.0 09.8 0.990 -3.3 06.2
05/05 09.3 09.8 0.987 -3.3 07.4
05/10 10.6 09.9 0.983 -3.4 08.4
05/15 11.9 09.9 0.978 -3.4 09.5
05/20 13.3 10.0 0.973 -3.4 10.4
05/25 14.6 10.1 0.967 -3.4 11.3
05/30 15.9 10.2 0.961 -3.4 12.2

The evening of May 8 will present an interesting opportunity to search for Venus in association with New Moon spotting. Venus and the Moon will appear near each other as shown in my graphic at http://www.curtrenz.com/astronomical.html 8O

During the early morning hours (US time zones) of 2005 APR 24 a Penumbral Lunar Eclipse will occur. The penumbra is the gray outer portion of the Earth's shadow. Anyone standing on the Moon within the penumbra would see the Sun partially occulted by the Earth.

During this month's event the Full Moon will come fairly close to the umbra, the dark portion of the shadow in which the Sun would appear totally occulted by the Earth. At mid-eclipse, observers should notice a moderate darkening toward one edge of the Moon. Your photos would be welcome additions to this thread.

I have created a graphic previewing three stages of the eclipse. It is customized for Chicago (especially the Moon's altitudes) but should well serve all observers experiencing nighttime. To see it, click:

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

Then click the small blue button for "Penumbral Lunar Eclipse".

The graphic may be removed soon after April 24.

I've created a May 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.

EDIT: The answers are revealed in the next post in this thread.

How well do you know the Moon? The first one to answer all five questions correctly will be designated Lunatic for the Night. 8O

1) What is "the Old Moon in the New Moon's Arms"?
-- A. The Moon aged 27 days
-- B. The face seen in the Moon a few days after it is full
-- C. The portion of a waxing crescent Moon lit by earthshine
-- D. Venus being occulted by the Moon
-- E. A waning Moon passing through the Pleiades

2) What is "Diana's Bow"?
-- A. The Moon aged 3 days
-- B. The front portion of a dark area of the Moon shaped like a boat
-- C. A portion of a lunar mountain range that curls like a ribbon
-- D. A rising Moon
-- E. A setting Moon

3) A Half Moon (semicircular disk - first or last quarter of a circle from the Sun) is on average what percentage of the photometric brightness of a Full Moon?
-- A. 64%
-- B. 50%
-- C. 36%
-- D. 22%
-- E. 8%

4) What is meant by a magnitude of 1.5 for a lunar eclipse?
-- A. An eclipsed Moon that is midway in brightness between a first and second magnitude star
-- B. The maximum depth of a penumbral eclipse
-- C. A lunar eclipse occuring one and a half years after the previous one
-- D. A totally eclipsed Moon with a distance equal to half its diameter separating its limb from the edge of the umbra
-- E. A total eclipse lasting 90 minutes

5) When was the last time that from any location on Earth the Moon occulted Pollux, the first magnitude star in Gemini?
-- A. 2005 APR 16
-- B. 1987 NOV 10
-- C. 1913 JUN 07
-- D. 1820 APR 19
-- E. 117 BC SEP 30

Apparently Hubble may be saved.

Click below:

http://dsc.discovery.com/news/briefs/20050425/hubble.html?msn=dsc_news

Who will be first to spot the New Moon by naked-eye after its conjunction with the Sun on 2005 MAY 08 at 08:45 UT (03:45 CDT)?

The 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.

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 at 24:51 hours after conjunction.

Americans in the Midwest will have a chance to spot the Moon aged about 16.5 hours on Sunday after sunset. It will be near Venus, which is a little more than a month past its superior conjunction. It won't be easy to sight the Moon that evening, but an opportunity presents itself to beat others around the world.

Please report your May 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 20 minutes after sunset on May 8 (Mother's Day) at 20:17:05 CDT as seen from Chicago's Adler Planetarium. At that time the Moon will be at Azimuth 296.3 and Altitude 3.6. Its elongation from the Sun will be 7.8 degees, which is only a little beyond the theoretical 7-degree Danjon limit for spotting the Moon. Venus will be at Azimuth 292.7, Altitude 4.6 and elongation from the Sun of 10.1. In any event, 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 "May New Moon Spotting Contest".

The graphic may be removed soon after May 8.

How well do you know the Moon? Don't be afraid to provide your answers/guesses. The first one to answer all five questions correctly will be designated Lunatic for the Night.

1) What is the average number of days between successive Full Moons?
-- A. 27.32
-- B. 28.10
-- C. 29.53
-- D. 30.44
-- E. 31.76

2) On average the Moon rises how many minutes later each day?
-- A. 11.91
-- B. 19.28
-- C. 31.19
-- D. 50.47
-- E. 81.67

3) What phase is the Moon if it rises about sunset and sets about sunrise?
-- A. Dark of the Moon (New Moon)
-- B. Waxing Half Moon (First Quarter)
-- C. Full Moon
-- D. Waning Half Moon (Last Quarter)
-- E. It could be any phase.

4) The phases of the Moon recur on approximately the same dates after what number of years?
-- A. 4
-- B. 7
-- C. 10
-- D. 14
-- E. 19

5) Over the long run (586-year cycle), what percentage of Full Moons are totally eclipsed?
-- A. 0.7%
-- B. 1.4%
-- C. 2.8%
-- D. 5.6%
-- E. 11.2%

I've created a free June 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.

Who will be first to spot the New Moon by naked-eye after its conjunction with the Sun on 2005 JUN 06 at 21:55 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.

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 June 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 30 minutes after sunset on June 7 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 "June New Moon Spotting Contest".

The graphic may be removed soon after June 7.