DREAMS OF A SUPERCOLOSSAL TELESCOPE
by Terence Dickinson, SkyNews Editor

Astronomers ranging from the backyard stargazer peering through a small telescope to the Ph.D. astrophysicist planning where to point the Hubble Space Telescope all have the same wish. They dream of someday using a larger and better telescope. In those dreams, larger is almost always the most important part.

Larger in astronomy typically means doubling the size of the telescope’s main lens or mirror. Dreaming about it is called aperture fever.

The most serious case of aperture fever in astronomical history afflicted an Irishman named William Parsons (1800-1867), who, after age 40, was known as Lord Rosse. Using his considerable personal wealth, he built a large telescope even by today’s standards that boasted a main mirror 36-inches (0.9 metres) across.

After just a few looks through this instrument, Lord Rosse was so impressed by what he saw that he immediately began work on a behemoth with a 72-inch (1.8-metre) mirror. Completed in 1845, it was the largest telescope in the world until it was dismantled in 1908.

When pointed overhead, Lord Rosse’s monster scope was five storeys tall and was supported by ropes and pulleys strung between two massive stone walls. The telescope tracked the sky by pure manpower. Four men from the Lord’s estate were trained to crank and pull the giant telescope tube to follow each celestial object being viewed. Although cumbersome, the telescope’s main problem was frequent cloud cover at Birr Castle, 125 kilometres east of Dublin. Undeterred, Lord Rosse and his “gentlemen scientist” colleagues discovered the existence of spiral galaxies during the telescope’s first year of operation. Although no one at the time knew the nature of the spiral nebulae, as they were then called, drawings made at the eyepiece of the big scope led an American scientist, Stephen Alexander, to correctly suggest for the first time that our own galaxy, the Milky Way, might also have spiral arms.

The huge telescope at Birr Castle became a world centre for astronomy during the middle of the 19th century, and has now been restored to its original state as a historical exhibit. But the legacy of Lord Rosse as having the world’s most serious case of aperture fever lives on. In fact, it may be overtaken by research astronomers considering the successor to the Hubble Space Telescope with its 2.4-metre optical mirror.

One of the ideas being floated is a telescope on the Moon with a 30-metre mirror. That’s big enough to image an Earth-sized planet in orbit around a sunlike star 50 light-years away. It could also detect if there is any oxygen in the planet’s atmosphere--a key signature of life. For many billions less than the cost of the International Space Station, an international 30-metre telescope on the Moon could be operational in less than 20 years. It’s the ultimate aperture fever dream.

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CONSTELLATION WATCH
by Todd Carlson, Assistant Editor

The autumn and winter constellations are once again coming into view with the change of seasons. By 11:00 p.m., the constellations Cassiopeia, Andromeda and Perseus are all high enough in the northeast to allow a convenient look at their deep sky treasures.

Cassiopeia, easily identified due to its distinctive “W” shape, is embedded in the autumn and winter sector of the Milky Way. As you look at toward this part of the Milky Way, you are gazing toward the outer edge of our galaxy. Try this comparison: Using binoculars soon after dusk, note the difference in density of Milky Way stars visible while looking towards the centre of our galaxy in Sagittarius and Scorpius along the south-western horizon, compared to what can be seen looking towards the Cassiopeia Milky Way later in the evening. As you would expect, the “downtown” section around Sagittarius is more crowded.

Cassiopeia can be used as a guide to finding two deep sky treasures, NGC869 and 884 and the Andromeda Galaxy. Commonly known as the Double Cluster, NGC869 and 884 are two fifth-magnitude clusters 7,000 light-years away which are visible to the naked eye as distinctive hazy spots within the Milky Way. Located to the left of the “W” at this time of year, the Double Cluster provides a splendid view in binoculars, while a telescope will reveal a treasure-trove of stars.

From a dark observing site, Cassiopeia can aid in finding the Andromeda galaxy, also known as M31. Appearing as a fuzzy patch amongst the stars, at 2.3 million light-years away it is the most distant object that can be seen with the naked eye. Binoculars will show an elongated haze while a telescope will also show its two companion galaxies.

For a sky chart showing the location of the Andromeda Galaxy and NGC869 and 884, click HERE.


PLANETARY ROUNDUP

Jupiter is low in the southwest at dusk in September and early October. By the end of October the big planet is too close to the Sun to observe.
Venus hugs the south-eastern horizon just before dawn but will soon be disappearing behind the Sun.

Saturn rises a few hours before dawn, appearing as a yellow-coloured “star” in the constellation Leo. On September 19 the crescent Moon will be 5° below Saturn.

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SkyNews Observer's Guide
Are you considering buying a telescope for Christmas? Do you have an interest in astronomy but aren’t sure how to begin observing? What special events are occurring in the night sky this week? The SkyNews Observer’s Guide contains articles such as “Tips For First-Telescope Buyers” and “10 Steps to Successful Stargazing” as well as a synopsis of what can be found in the night sky for the upcoming week.

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In the September/October 2006 issue of SkyNews:

• 2005 SkyNews Photo of the Week contest winners.
• Exploring the Night Sky by Alan Dyer.
• Scoping the Sky by Ken Hewitt-White.
• Guide to the Outer Planets.
• Strange Bedfellows: Making Sense of M81 and M82.
• Moon map.
• Star chart for September and October.
• And more!

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