Highlights for the week of Mar 20 - 26, 2011

Sun. March 20 - At last! Spring officially begins at 4.21pm PDT. By this time we will have heard about preparations by the OC RASC  Penticton meeting group to mark the equinox at the Pen Henge standing stone array on Munson Mountain. At the winter solstice event when the array was dedicated, clouds prevented the light of the setting Sun from casting a shadow from the southernmost stone directly to the heel stone. Hopefully clear skies will allow the Sun to peak over the equinox stone and extend a shadow to the heel stone this time.
 
Mon. March 21 -  The bright star that can be seen near the Moon tonight is Spica, the brightest star in the constellation of Virgo. It might be of interest to know that it is the 15th brightest star in the sky, and that it is a blue giant sun that is 7 times the radius of our Sol. It is located 260 light years from us. In other words, when you look at it, the photons that are entering your eye and becoming part of your body left Spica about the year 1751.
 
Mon. March 21 - The next two weeks or so is a good time to view and identify the Zodiacal light, an extended triangle of faint light that extends up into the early evening sky from the western horizon. Made by the light of the Sun reflecting off dust particles in the equatorial plane of the solar system, the Zodiacal light can be seen by skilled observers from mid winter to late spring and again in the eastern sky from early autumn to late fall. Now however, its spring appearance is easiest and most dramatic to view.
 
Sat. March 26 - It's Last Quarter Moon time. Sky watchers can again enjoy the crisply silhouetted craters, mountains and plains along the Moon's terminator with a telescope or binoculars. This time the sunlight streams from the opposite direction than it did at first quarter, producing a starkly different view of the same terrain.

The Okanagan Observatory is 4 kms up Big White Rd from Hwy 33. That makes it only 17 kms from Big White Village. We are opened every Friday night for public viewing. We start the night with a 30-minute educational slide show at the Sky Theatre. Then we move on to telescope viewing. The Gamble 25” telescope chugs out on its railway and is pointed at many wondrous celestial objects. Club members will also have their telescopes in use. We will be pointing out the Milky Way and constellations with special astronomical laser pointers as we tour the night sky. More information can be found at www.okanaganobservatory.ca. Phone the Okanagan Observatory Event Phone, 250-300-8SKY (8759) for an event update after 3 pm on Friday.

Iridium Flares

International Space Station

What is Zodiacal Light?

It is a cone of light that can be seen on clear, Moonless nights. It extends upwards, sometimes 30-40 deg (about 1/3 the way up the sky from the horizon) and can occasionally be as bright as the Milky Way. The Zodiacal light is the reflection of light from the countless billions of tiny dust particles that are present as a disk in the inner solar system and extends out as far as the orbit of Mars.

What is a Blue Moon?

What's an Iridium Flare?

An Iridium is a communication satellite that tumbles through space as it orbits the Earth. Iridiums have very reflective solar panels and as they tumble, they can reflect sunlight to the Earth at a very predictable time in a very predictable place showing up as a 'flare'.

• Time, the time for an Iridium is given in 24 hour clock format. So, 16:52:30 means 4:52:30 pm.

• Mag, this means the magnitude of the flare or how bright it will get. It's a reverse scale so 0 is bright but -8 is brighter.

• Altitude, this is the place above the horizon where you will see the flare. The horizon equals 0 deg and directly overhead is 90 deg. So, half way between would be 45 deg and 2/3 of the way up would be 66 deg.

• Azimuth, this is the North-East-South-West direction to look. North equals 0 deg, East is 90 deg, South is 180 deg and West is 270 deg.

Enjoy the show!