Fall Equinox Show Friday: How to Watch Online

On Saturday, Sept. 22, the sun crosses the celestial equator heading south. This is the autumnal equinox in the northern hemisphere and the vernal equinox in the southern hemisphere. CREDIT: Geoff Gaherty/Starry Night Software/SPACE.com View full size image

This weekend marks the transition from summer to fall in the Northern Hemisphere, and viewers around the world can watch a special webcast Friday (Sept. 21) to celebrate the event.

The online Slooh Space Camera, which broadcasts live views from telescopes around the world, will stream shots of the sun Friday beginning at 4 p.m. EDT (2000 GMT). The free show is in honor of the September equinox, which on Saturday (Sept. 22) rings in the Northern autumn and the Southern spring.

Slooh will also air telescope views of the moon during the webcast to mark International Observe the Moon night, which falls on Saturday this year as well. The sun and moon shots will come from observatories in Prescott, Ariz., and the Canary Islands off the west coast of Africa, Slooh officials said.

The webcast can be accessed at the Slooh Space Camera's website.

A panel of experts will be on hand to discuss the equinox, International Observe the Moon night and the views seen by the telescopes. Participants include:

• Patrick Paolucci, Slooh president
• Bob Berman, Slooh editor, Astronomy Magazine columnist and author
• Matt Francis, Prescott Observatory
• Lucie Green, solar researcher and frequent BBC contributor
• Paul Cox, Slooh engineer

The word "equinox" comes from the Latin for "equal night," referring to the fact that day and night are of roughly equal length worldwide on that date.

But the equinox isn't actually a day; strictly speaking, it's a moment in time, defined as the instant the sun crosses the celestial equator (which is Earth's equator projected onto the sky). The sun is above the celestial equator for half the year (spring and summer) and below it for the other half (fall and winter).

International Observe the Moon Night is put on by a coalition of scientists, educators and moon enthusiasts around the world, in an attempt to instill a sense of wonder and curiosity about Earth's nearest neighbor. [How to Observe the Moon (Infographic)]

Moon-viewing parties will be held at multiple sites around the world on Saturday. To find one near you, visit http://observethemoonnight.org/.

While Slooh's webcasts offer amateur stargazers access to world-class observatories, the organization is working to make the experience more interactive. It's currently developing an app called MySky, which will allow users to command Slooh robotic telescopes via their own tablet computers or cellphones. The first version should be available in the next few months.

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