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Astronomy Know How
Helping you See the Night Sky - Newsletter No. 16 February 2008
In this issue:
  1. February's Highlights
  2. Total Lunar Eclipse
  3. What's an Asterism?
  4. Saturn at its Best
  5. Tip of the Month
  6. News Links
  7. Become a confident Astronomer
  8. Contact Us
February's Highlights

Without a doubt, the highlight for this month is the Total Lunar Eclipse on the 21st. Please see below for more details on this spectacle.

Take at look at the constellation of Cancer the Crab this month. This somewhat overlooked constellation has many interesting objects including the 'Beehive' Cluster M44. The name will make immediate sense to you the moment you turn a pair of binoculars onto this lovely open cluster.

If you would like to test how good your binoculars are, then while you are in the vicinity of the Beehive cluster, go and hunt for the star Iota Cancri which is the northernmost star of the inverted 'Y' shape that forms the shape of the constellation. This star is a close double star only 31 arc-seconds apart and is a challenge for 10x50 binoculars, although a small telescope should split it relatively easily. Nearby is the star 55 Cancri lying to the south-east of Iota. This star has been found to have at least 5 (that's right, five) planets in orbit around it. Although we cannot see these planets directly from Earth, we know that they are there from the movement of the star. Of course the question has to be, does one of these planets harbour life?

If you like hunting galaxies, then go and take a look at M81 and M82 in Ursa Major the Great Bear or the Big Dipper as it is known in the USA. These two galaxies can be found by extending an imaginary line from the bottom left star in the 'pan' of the Dipper, to the top right one (Alpha Ursa Majoris) and on for a similar distance the other side of Alpha. A small telescope with a low power eyepiece should be able to pick up the faint smudges of light that are these two distant island universes. Good hunting!

Jupiter and Venus are in close conjunction on the 1st of the month very low down in the east just before dawn. So you will need a very clear horizon to be able to see these two bright planets occupying the same region of sky, but you may be lucky...

If you are interested in stars that vary in brightness, then Mira 'The Wonderful' is expected to be at its maximum brightness this month. The star is much larger than our Sun and pulsates with a period of 80 to 1000 days varying in brightness by at least 2.5 magnitudes. You can find Mira low down in the south in the early evening from mid-northern latitudes.

Total Lunar Eclipse

This month brings you the chance to observe a Total Eclipse of the Moon. This is when our Moon's orbit takes it into the shadow cast by the Earth from the Sun's light. You will have to stay up late (or get up early) to see this event on Thursday the 21st February. The Moon will by eclipsed by the Earth's shadow starting at 1h 43m UT and will continue until it exits at 05h 09m around dawn as seen from Europe.

As the Moon passes into the umbral shadow of the Earth, it will appear to go quite dark although the shadow will not show a sharp edge such as you get with a partial or total solar eclipse. As the Moon becomes totally immersed in the shadow, it will likely take on a reddish or 'coppery' hue. This is because some of the light from the sun is bent through the Earth's atmosphere and illuminates the surface of the Moon.

This is a similar effect to a sunset here on Earth where the red light emitted by the sun is bent or refracted more than any other colours in the spectrum. If you were to stand on the Moon during a total Lunar eclipse you would see a red ring around the dark Earth where the sun's light is being bent through the Earth's atmosphere. It is this red light that faintly illuminates the Moon.

What's an Asterism

I'm sometimes asked to explain the word 'asterism'. It is a group of stars that make up a familiar shape, sometimes from a part of a constellation, or sometimes made up of stars from more than one constellation. An example of this would be the Summer triangle. This is a large triangle of stars in the sky formed from Deneb in Cygnus the Swan, Altair, the bright star in Aquila the Eagle and Vega the brightest star in Lyra the Harp. A familiar sight throughout the summer months in mid-northern latitudes.

Other such asterisms are the Plough or Big Dipper in Ursa Major the Great Bear, or the Teapot found in the constellation of Sagittarius the Archer. Another is the 'W' of Cassiopeia and yet another the 'Keystone' found in Hercules.

You can of course make your own up to help you find your way around the sky. They might not pass into common usage, but they would at least be familiar to you. So have a go...

Saturn at its Best

This month will see Saturn at its best for the year. However, due to our position in relation to the planet the famous rings are apparently slowly tilting away from us, so they seem to be getting thinner from our perspective. The famous Cassini Division, the gap between ring A and ring B, is now becoming harder to discern due to the shallow angle from which we are viewing the rings.

Keep watching Saturn as you may see the Seeliger Effect on or around February 24th when the planet is at opposition; that is when it is directly opposite the Sun in the sky. This effect is an apparent brightening of a planet when it is at opposition, so you will have to have been observing the planet for a few days before to notice it.

You will find Saturn between the feet of Leo the Lion and near the star Rho Leonis. It looks like a yellowish star, a little brighter that the star alpha Leonis (magnitude +1.3) known as Regulus, the brightest star in the constellation.

Tip of the Month

More about binoculars...

Tip: If you are using a pair of 7x50 or 10x50 binoculars for astronomy, the best type for this activity, you need to make sure that the optical axis of each side of the binocular is in line with your eye. In other words, when you look through your binoculars, you should see one complete circle as the field of view and not two! So make sure that the inter-pupilery distance is set correctly for your own eyes. That is to say you must push the two sides of the binoculars together or pull them apart as needed so that you only see this one circle of the field of view.
  Here are some links to some other recent news stories that I thought you would find interesting...

Better-suited for the moon's surface
NASA revising astronauts' wardrobe for missions on dusty landscape

Beyond Our Solar System: In Search of Extrasolar Planets
What if the Universe contains other planets like Earth outside the Solar System? After all, the Sun is only one of 100 billion stars in the Milky Way Galaxy alone...

Number 1
Last month we gave you the news...

UK Plans Withdrawal From Telescope Teams
"This decision is a serious mistake and a shock to all of us, " Michael Rowan-Robinson, society president, said in a press release

This month you can help because the BAA are organising a petition to go the government to protest the withdrawal of funding to physics and astronomy - the loss of the use of these northern hemisphere telescopes is only part of a bigger funding cut...
You can read the whole story here and help out by adding your weight to the protest.
PLEASE do this because the petition will only get to the government if lots and lots of us sign up.... more...

Number 2
Can you see the stars?

2008 marks a monumental shift in human history when more than half the people on Earth are expected to be living in cities. Because of the ambient light of urban landscapes, many city dwellers have never seen a sky full of stars.

You can help map the world light pollution by joining in for the 2008 GLOBE at Night Campaign from 25 February - 8 March where you can report you observations as part of a huge project... Click here to learn more
  Do you want to learn more about the night sky and how to use telescopes and binoculars to see it better?..

My online course gives you all the essential information to be a good astronomer, without lots of jargon or difficult maths. You'll get loads of free bonuses and it also has videos and animations to help make the explanations clear and concise. So if you want to know what Sir Patrick wished for...

...please take a look at my eCourse called
'Basic Astronomy with a Telescope'. It's what Sir Patrick wished he'd had when he started out in astronomy!

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