August Opens With an Evening Show

Evening Show

The waning crescent Moon creates a majestic skyscape to open the month of August, shimmering against the dusk sky with the shiny colors of Spica, Mars and Saturn in the path. Each evening the trio of planets and stars will have the Moon in their midst, and the Moon will slip gradually eastward with each successive night.

I enjoy seeing the waxing Moon with its delicate shape and edge-on illumination from the Sun. It's fun to see in a telescope and it always holds the promise of the gentle glow of Earthshine. In the middle of summer, the ecliptic is low on the southern horizon and the Moon slices a gradual slope across the sky.

This view will be enhanced by binoculars, if you have them. You will see deeper into the details of the Moon and into the constellations along the southern horizon with the fringes of the Milky Way in view due south as darkness falls.

Image courtesy of Sky & Telescope.

Sun and Moon and Ebb Tides

A kayaking friend of mine referred me to a question posed by a fellow kayaker regarding tides in and around the Golden Gate: Why are Ebb Tides strongest in SF Bay at night during the summer and during the day in winter? I love this kind of question, where the celestial mechanics of the Solar System impact the daily experiences of hobbyists and average people on Earth. 

First of all, why are there differences in size of high & low tides throughout the month and year? Each month the highest highs and lowest lows occur when the Moon is Full or New. That’s pretty simple. But there are two important factors regarding the Moon’s proximity to Earth on any given Full or New Moon. And there is one important factor regarding the Sun’s proximity to Earth on any given Full or New moon.

1. The Sun’s Changing Proximity

The Earth’s orbit around the Sun is elliptical, meaning that there is a close approach each year on January 4th (“perihelion”) and a corresponding far point in our orbit in July (“aphelion”). The New and Full Moon phases just before or after January 4th have higher high tides at the noontime tide, leading to a very fine ebb tide in the middle of the afternoon.

2. The Moon’s Changing Proximity

The Moon’s orbit around the Earth is elliptical, so there are times when the Moon is closer (“perigee”) and farther (“apogee”). Lately the press has made much to do about the “Super Moons” that occur when the Full Moon lines up with Perigee. On August 10, 2014 we will have a very fine Super Moon precisely at the same time as Perigee, so there will be higher high tides at midnight and lower low tides at dawn, leading to a very fine ebb tide in the middle of the night.

Another factor is the Moon’s location along its orbit from a north-and-south perspective. The Moon’s orbit around the Earth is inclined slightly and follows the “ecliptic” which also meanders above and below the plane of the equator, meaning that sometimes it is physically above the plane of Earth’s equator and sometimes below (“ascending and descending nodes” of the lunar orbit). If the Moon is above the plane of the equator, it is actually a bit closer to the land and water north of the equator, exerting a slightly greater tidal pull. The next peak of this effect is on August 9, 2014, so we can look forward to some amazing high and low tides at the next Super Moon. The ascending node and its impact are not tied directly to winter or summer, so this effect is less predictable.

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To answer the original question: there are good ebb tides each month at New and Full Moon, but the changing effects of perihelion and perigee cause the solar influence to be greater in Winter (hence the better daytime ebb tides) and the lunar influence to be greater in Summer (hence the better nighttime ebb tides).

This website offers additional insights into tides. 

Fun subject to think about! Wow!

Binocular Astronomy

From an urban setting such as my home in San Francisco, I have a reasonable view of the night sky, knowing that from my own backyard I can see a good number of stars if I have clear skies and I am patient, allowing my eyes to dark adapt. In a city setting you are limited in the depth of the night sky you can experience by the ambient light in your exact setting, and the light pollution dispersed into the sky. But you can overcome these factors somewhat, by using binoculars.

Every time I am at a star party or astronomy gathering, in addition to a telescope I bring my binoculars. These are the fastest way to enhance your viewing whether you are in a dark sky or city setting. No matter what conditions you have, you will see deeper and will experience more richness in the night sky with binoculars. They are intuitive and require no special technical knowledge to use. You just point at a part of the sky and enjoy. Gary Seronik of Sky & Telescope publishes regular articles focused on binocular viewing and has an excellent resource book (I have a copy, of course) just for binocular viewing, Binocular Highlights. I highly recommend it.

Summer Milky Way in binoculars

During the summer months, point east and above to experience the richness of the Milky Way through binoculars. Even in city settings where the true outline of the Milky Way is not visible, binoculars will reveal some of that richness, exposing clusters and nebulae in the depths of the galaxy. I am particularly fond of the charts from the Great Smoky Mountain Astronomical Association for highlights in the summer galactic zone.

My old Celestron 10x50 binoculars have served me well for years and I carry them with me virtually everywhere I go. You should consider the same.

Image courtesy garyseronik.com.

Mars and Spica Align

Mars and Spica Align

I've been watching Mars over the past few months as it slips steadily along the Ecliptic. It was near the bright star Spica several months ago as it was near opposition, then moved retrograde toward Porrima on the other side of the constellation Virgo, and now is back near Spica as it resumes prograde motion toward an August rendezvous with Saturn. The image shows where to spot the two bright objects in the south-west sky this week.

Image courtesy of Sky Safari.

The Start of a Lunar Cycle

Young Moon movements

Each time a lunar cycle begins, I look forward to each evening to see where the Moon is going to be, starting with a dark night sky at New Moon, and over the course of a week enjoying the waxing crescent of our celestial neighbor as it grows into First Quarter. Along this journey, I await alignments and close encounters, and in the early days of the current lunar cycle there are many objects in the path of the Moon.

Moon & Mars

New Moon is on Friday June 27th, and the first chance to spot the young Moon is Saturday 28th (which, if sighted, will start the month of Ramadan). The Moon on the 28th is very near Jupiter and both set shortly after sunset. It will pass very near Regulus in Leo on July 1st, and as it then travels across the ecliptic it will reach First Quarter and have a close encounter with Mars and Spica, covering Mars for a short while on July 5th, but this event will not be visible from North America.

After passing by Mars, the Moon will gradually move next to Saturn. More on that in my next blog post.

Images courtesy of Sky  & Telescope.

Why You Should See An Eclipse

Shadows during an eclipse

I gave a talk recently at an event in San Francisco called Ignite, a fun evening of short, fast-paced talks on a wide variety of subjects. Click here to watch my 5 minute video on the subject of eclipses. I think you'll be inspired (and if not, then it's only 5 minutes :-)

The Constellation Virgo

Late spring and summer skies are dominated by the big constellation Virgo, the Maiden. This grouping of stars is the second largest in the night sky (after Hydra), and includes the first magnitude star Spica, the double star system Porrima, and the Virgo Cluster, a region of the universe that has 1000s of galaxies in one place. [More on the Virgo Cluster and Supercluster in a future post]

The Constellation Virgo

A member of the 12-constellation zodiac, Virgo is directly in the path of the Moon, Sun and planets and consequently is host to wandering celestial objects. Now and for the coming months, bright orange Mars is passing through the constellation en route to a mid-July rendezvous with Spica. In mythology, the constellation represents a woman in the sky, but the identity is different depending on whether you read the Babylonian, Roman or Greek interpretation. And in any case, I find it quite difficult to see a distinctive pattern from the stars in Virgo. Nonetheless, it is a fascinating place in the sky, because it contains the Virgo Cluster of galaxies with notable telescope objects such as M86 and M87 and the magnificent Sombrero Galaxy.

Virgo occupies an interesting space in the sky, the First Point of Libra, a place where the Ecliptic (path of the planets and Moon) crosses the Celestial Equator (dividing line between the northern and southern hemispheres in the heavens). The Sun's arrival at the First Point of Libra marks the first day of Autumn in the northern hemisphere (Autumnal Equinox). The reason why this spot is called the First Point of Libra is that thousands of years ago the intersection of the Ecliptic and Celestial Equator was in the constellation Libra, but the effects of precession have moved that point from Libra to Virgo, and in 400 years that will move into the next zodiac constellation, Leo.

From city limits you can certainly find Spica, Porrima and for the next few months, brilliant orange Mars in Virgo. With binoculars you can gaze into the heart of the Virgo Cluster and although you won't see The Big Picture with 1000s of galaxies, you will certainly see a richness of stars and know that you are seeing light that is at the center of our own supercluster of galaxies that define our corner of the universe.

Images courtesy of Wikimedia Commons

Possible New Meteor Shower

Meteors are a delight to see in the night sky, appearing without warning and gracing the sky with their shimmer and speed, playful fireworks that quietly captivate those who take the time to watch. Annually there are many meteor showers that we can predict and prepare for, primarily because they are caused by debris in the path of Earth's orbit and are reliably there each time Earth passes through the debris. In most cases "debris" means the small particles of dust no larger than a grain of sand, left in the wake of a comet or asteroid.

Radiant in Camelopardalis

Friday night May 23 through Saturday morning May 24, Earth will travel through such a stream for the first time from a source that we have not encountered before. In this case it's Comet 209P/LINEAR, a fairly unimpressive comet from a visual point of view, but one that has left a debris stream in its wake and could be have initiated a new meteor shower. The peak for this will be Friday night / Saturday morning around 1:00 am pacific time, so find a dark spot with a clear sky, give your eyes time to adapt, and enjoy. You don't need a telescope or binoculars. The 'radiant' point of the shower is in the faint constellation Camelopardalis (see image) but you don't need to face that way - just have a clear sky and a good view overhead, a lawn chair or pad to relax on.

More information on the following sites:

Spaceweather.com 
Sky & Telescope
EarthSky.org

Image courtesy of Sky & Telescope.