How to view Sunday’s Annular Eclipse

Path of the Annular Eclipse in Western United States

Path of the Annular Eclipse in Western United States

This Sunday, May 20, there’s an annular eclipse — a ring-around-the-moon not-quite-a-total eclipse.

I’m traveling to an area where it’s as total as possible this weekend (the SW corner of Utah), but here’s instructions for how when to view it where you are. The Exploratorium has a how to view it post.

The Goddard Space Flight Center has a javascript-run page that will help you see LOCAL time and place info. Follow these instructions:

You need to know three things:

  • your lat-long coordinates
  • your elevation (altitude) in meters
  • what time zone you’re in

Convert Street Address (Location) to Lat-LongGeocoder.us will convert a street address into lat-long info.

For an example, I’ve put in the address of the Jet Propulsion Laboratory, and gotten the lat-long coordinates. I looked up the elevation for the city that JPL is located, and decided to average the high and low elevations to 500 m.

Geocoder info for JPL

Then, on the JavaScript page, I clicked the link for North America, Central America and the Carribbean.

In the first section, I entered those JPL coordinates as follows:

Entering JPL's coordinates

Entering JPL's coordinates

JPL is in the Pacific time zone which is GMT -8, but since it is daylight savings time I changed it to -7. The little pop ups in the JavaScript page want you to express the time zone as east or west so I put 7 W.

Here is the result after clicking the 20th century button

JPL Eclipse details

JPL Eclipse details

Compare that to the result for Cedar City, Utah, which does have annularity to the eclipse. (The eclipse is listed as A — annular, and there are additional details for times of entering annularity)

Eclipse details for Cedar City, Utah

Eclipse details for Cedar City, Utah

The key to the table says that for the eclipse magnitude it’s a fraction of the sun’s diameter that’s obscured by the moon. For annular eclipses the magnitude is less than 1.0

I learned from the Planetary Society’s night guide for Summer 2012 that it’s possible to get Eclipse viewing glasses, and so I made a trip out to the store in the San Fernando Valley where they sell them. Here’s my stash for the Family Eclipse Viewing partipants. Oh, and I got a special filter to use on the telescope.

Eclipse Viewing Glasses

Eclipse Viewing Glasses

IMPORTANT! If you do not have this special optical filters that make it safe to look at the sun, use the pinhole camera method of viewing as described in the Exploratorium article.

Last, but not least, it’s important that you have an unobscured view of the sun. There was a lovely annular eclipse in the early 1990s, and I didn’t see it, even though I was in the right place. A group of us stood at the top of Mount Wilson and cursed the clouds.

The outlook for our viewing location looks perfect. Sunny, no cloud cover.

Weather Forecast for Cedar City, UT

Weather Forecast for Cedar City, UT

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