Astronomy Question: Darkness and Meteor Showers

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Janet asks,

Dear Astronomer,Why does it always say that the best time to watch for
meteorites during a meteor shower is between midnight and dawn?

Are there really more meteorites at that time, or is just because the sky is usually
darker at that time?

We live in the high mountains of Colorado, 21 miles from the nearest small town.

When we crawl out of bed at 3 AM to watch a meteor shower, I wonder if we couldn’t see it just as well at 9 PM.

We seem to see just as many stars at that time.

Thanks, Janet

Great question Janet!

There are a number of factors that can affect visibility of a meteor shower, some of which you touched on in your question.

I’ll explain a number of things that go into an “ideal” meteor shower viewing experience.
Keep reading to learn more on making the most of your next meteor shower.

As Janet touched on briefly, there are a number of factors that can affect the number of meteors visible during a shower.
For starters, meteor showers can be slightly variable, with the meteor per hour counts varying from one year to the next.
One other variable is which phase our Moon is in. There were a few meteor showers in 2011 that were pretty much spoiled by a full moon. This year’s crop of meteor showers look to be less hampered by our closest neighbor in the solar system. A variable many people in urban settings have to content with is light pollution. While many meteors leave incredibly bright streaks, there are some that are fainter and can easily be lost in the glare of streetlights.

You’ll see in many online guides for viewing meteor showers (including this site) that the best time to view a meteor shower is between midnight and dawn. Janet points out that she lives away from city lights and can generally see the same number of stars at any point in the evening. I too live in a semi-rural area and enjoy a fairly dark night sky after about ten PM. There’s a few reasons why it’s suggested to view a meteor shower past midnight.

For starters, many localities do actually have lighting ordinances which require outdoor lights to be dimmed or turned off by 11PM. Many people have gone to bed for the night, and have turned off most of the lights in their houses. While the dimming of outdoor lights certainly helps, it’s just one of several reasons.

In many cases, the peak activity of a meteor shower happens to occur during the pre-dawn hours, rather than the late evening/early night hours. My experience has shown more meteors to be visible from between 1 and 3AM, but other astronomers may have different experiences. One other reason, and possibly the most important reason is the position of the “radiant” in the night sky. In the context of meteor showers, the radiant is the constellation that the meteors appear to originate from.

For example, the upcoming Perseid meteor shower will have a radiant in the constellation Perseus. In the northern hemisphere, during early August, Perseus is just barely over the eastern horizon at 10:30 PM! Not a particularly great place for the radiant. By midnight though, Perseus is well above the horizon and will continue to climb through the night. That being said, the Moon rises around 1AM and will diminish the view of meteors somewhat.

I’ll have a more detailed viewing guide for the Perseids in early August, but for now, I hope I’ve been able to help you understand why an enjoyable meteor shower experience might require staying up late or getting up early.

Ray Sanders is a Sci-Fi geek, astronomer and blogger. Currently researching variable stars at Arizona State University, he writes for Universe Today, The Planetary Society blog, and his own blog, Dear Astronomer