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An eclipse of the moon Sunday night provides a chance to use three lunar clichés at once, as we’ll see a blood moon, super moon and harvest moon at the same time.
But more importantly, it’s an eclipse that occurs in mid-evening — just right for easy viewing from Ottawa. So far, touch wood, the forecast seems clear.
From NASA: “Earth’s shadow will begin to dim the moon slightly beginning at 8:11 p.m. (Eastern time). A noticeable shadow will begin to fall on the moon at 9:07 p.m., and the total eclipse will start at 10:11 p.m.”
The total part of the eclipse, meaning that the whole moon is in shadow, will last an hour and 12 minutes. Then it gradually brightens as the moon emerges into sunlight. Watch for the left side of the moon to dim first (as seen from the northern hemisphere.)
And yes, it’s completely safe to watch because you’re looking at a shadow. The dangerous kind of eclipse is a solar eclipse, when people have to be careful not to stare into the sun.
Now, about all those cute moon phrases you’re bound to hear:
• A supermoon sounds important than it is. This just means the moon is at its closest approach of the year to Earth, so it appears slightly larger than usual — about 14 per cent bigger than at its most distant position of the year, which is a difference that people often have trouble seeing with the naked eye. Supermoons are also brighter — but this won’t matter during an eclipse.
The moon’s orbit is not quite round. At its closest, the moon is about 50,000 kilometres closer to Earth than when it reaches the most distant part of its orbit.
If supermoons are your thing, then you’re in luck. The last time we had one during an eclipse was in 1982; the next will be in 2033.
• A “blood moon” is also less dramatic than it sounds. A lunar eclipse, when the moon slides through Earth’s shadow, isn’t a complete blackout of the moon. Instead it becomes dimmer, with a reddish-orange tinge, and lately some astronomy websites have started calling it a blood moon. (It’s not THAT red.) This coloration happens every time the moon is eclipsed, or about twice a year. The last eclipse was in April.
• The harvest moon is more interesting. A harvest moon (the first full moon of fall), doesn’t look any different from other full moons. All full moons appear extra-big when they are just above the horizon, but it’s an optical illusion.
The fall equinox does create one oddity that brings a dramatic view, however.
Here’s John Percy, astronomer at the University of Toronto:
“As a result of the moon going around the Earth, the moon rises on average 50 minutes later every night. So if the moon rises at 8 p.m. tonight, it will rise an hour later tomorrow night.” At least, that’s how it happens for most of the year.
But around the equinox (Sept. 23 this year), the sun is shifting southward in our sky and the moon moving north. This changes the timing of how we see them.
Percy again: “Because the moon is moving northward, it is rising about 25 minutes earlier than it normally would, or only about 25 minutes later each night. Therefore, for about a week, it’s rising at about the same time that the sun is setting.”
That means that for several nights before and after the actual full moon you’ll see the beautiful view of a nearly-full moon rising just as the sun’s light goes dim, but not yet black. During the rest of the year these nearly-full moons rise much longer before or after sunset.
tspears@ottawacitizen.com
twitter.com/TomSpears1
查看原文...
But more importantly, it’s an eclipse that occurs in mid-evening — just right for easy viewing from Ottawa. So far, touch wood, the forecast seems clear.
From NASA: “Earth’s shadow will begin to dim the moon slightly beginning at 8:11 p.m. (Eastern time). A noticeable shadow will begin to fall on the moon at 9:07 p.m., and the total eclipse will start at 10:11 p.m.”
The total part of the eclipse, meaning that the whole moon is in shadow, will last an hour and 12 minutes. Then it gradually brightens as the moon emerges into sunlight. Watch for the left side of the moon to dim first (as seen from the northern hemisphere.)
And yes, it’s completely safe to watch because you’re looking at a shadow. The dangerous kind of eclipse is a solar eclipse, when people have to be careful not to stare into the sun.
Now, about all those cute moon phrases you’re bound to hear:
• A supermoon sounds important than it is. This just means the moon is at its closest approach of the year to Earth, so it appears slightly larger than usual — about 14 per cent bigger than at its most distant position of the year, which is a difference that people often have trouble seeing with the naked eye. Supermoons are also brighter — but this won’t matter during an eclipse.
The moon’s orbit is not quite round. At its closest, the moon is about 50,000 kilometres closer to Earth than when it reaches the most distant part of its orbit.
If supermoons are your thing, then you’re in luck. The last time we had one during an eclipse was in 1982; the next will be in 2033.
• A “blood moon” is also less dramatic than it sounds. A lunar eclipse, when the moon slides through Earth’s shadow, isn’t a complete blackout of the moon. Instead it becomes dimmer, with a reddish-orange tinge, and lately some astronomy websites have started calling it a blood moon. (It’s not THAT red.) This coloration happens every time the moon is eclipsed, or about twice a year. The last eclipse was in April.
• The harvest moon is more interesting. A harvest moon (the first full moon of fall), doesn’t look any different from other full moons. All full moons appear extra-big when they are just above the horizon, but it’s an optical illusion.
The fall equinox does create one oddity that brings a dramatic view, however.
Here’s John Percy, astronomer at the University of Toronto:
“As a result of the moon going around the Earth, the moon rises on average 50 minutes later every night. So if the moon rises at 8 p.m. tonight, it will rise an hour later tomorrow night.” At least, that’s how it happens for most of the year.
But around the equinox (Sept. 23 this year), the sun is shifting southward in our sky and the moon moving north. This changes the timing of how we see them.
Percy again: “Because the moon is moving northward, it is rising about 25 minutes earlier than it normally would, or only about 25 minutes later each night. Therefore, for about a week, it’s rising at about the same time that the sun is setting.”
That means that for several nights before and after the actual full moon you’ll see the beautiful view of a nearly-full moon rising just as the sun’s light goes dim, but not yet black. During the rest of the year these nearly-full moons rise much longer before or after sunset.
tspears@ottawacitizen.com
twitter.com/TomSpears1
查看原文...
