Category Archives: Astronomy 101

One of my main goals is to try and share a bit of knowledge and understanding about the incredible universe. I have been steadily writing and posting various articles to explain and educate the masses (that’s you, dear reader!) a bit more about some of the science behind the hobby. An urban astronomer might never see most of the things we talk about here, but it’s still good to know about them.

How do you calculate the date of religious festivals?

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Cultures around the world set aside special days every year as festivals, or times of remembrance.  Modern examples (Worker’s Day, Mother’s Day, Independence Day, Valentine’s Day and others) all last 24 hours and take place on the same date every year.  But the really old festivals, as observed by world religions, are often a little more flexible.  Their dates can vary from year to year, sometimes differing by as much as a month.  What gives? Astronomy wasn’t always the aesthetically … Continue reading →

Phases of the Moon

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Everybody knows that the Moon changes its face.  Sometimes we have Full Moons, other times it’s a Half-moon, or a crescent, or there’s no Moon at all.  And everybody knows that these are called the phases of the Moon.  But not everybody knows that these faces follow a regular cycle, or that the common descriptions are misleading at best.  A proper understanding of what’s actually happening to make the moon show different faces, and the nature of the “Dark Side … Continue reading →

What was the Star of Bethlehem?

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Merry Christmas to all readers (Not just the christian ones, since Christmas long since transcended a celebration of the Christ.  It’s even a huge deal in Japan, with less than 2% of the population reporting Christianity, for pete’s sake!), and a Happy New Year to you. Around this time of year, astronomers are often asked “What was the star of Bethlehem, exactly?”.  It’s a difficult question, because we have so little information to go on, and what we have precludes … Continue reading →

Finding your bearings

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One of the most practical skills in Astronomy is the ability to find your bearings.  Once you know where North is, you know East, West, South and all directions between.  There are many ways to find these directions, but the easiest and most accurate is by using a gnomon, and the sun. Knowing where your cardinal points are is important in astronomy.  Directions to find a particular object are either given in absolute coordinates (RA 11h56m25s, Dec -25°33’21”), or relative … Continue reading →

The Astronomer’s Enemy

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There’s one problem with Urban astronomy, and it’s a big one.  It is the reason so many historical observatories, places where great discoveries were made and the foundations of modern astronomy were set down, have been shut down and even demolished.  That problem is light.  Modern cities pump so much light into the sky that many of us have never actually seen a night sky at all.  Ask somebody what colour the sky is at night and they’ll confidently assert … Continue reading →