If you’re an amateur astronomer, or even just a night owl, today’s citizen science project will definitely appeal.

The International Occultation Timing Association (IOTA) wants you to measure an invisible asteroid at around 2:06 am on Thursday EDT, March 20th. How can you measure something you can’t actually see? You’ll be timing its “occultation,” or the length of time its passage through the sky blocks out the view of another celestial body.

Specficially, the asteroid 163 Erigone will be passing in front of the star known as Regulus in the constellation Leo, in what is predicted to be the best and brightest asteroid occultation ever to occur over a populated area. In the US, residents of much of the state of New York should be able to see the shadow, and in Canada the shadow will pass over a swath from Kingston right on up to North Bay. And if you happen to be wintering in Bermuda, you will get to see it as well, and a few minutes before everyone else to boot.

How can I take part?

To participate in the measurement project, grab a stopwatch, and head outside sometime before 2 a.m. on the 20th. Give yourself enough time to allow your eyes to adjust and to find Regulus. (If you’re new to this and not sure where to look, check out Heavens Above to generate a star chart for your location and time.) The simplest way to measure the occultation is to start timing when you see the star begin to disappear and stop the timer when it has fully reappeared.

If you’re good with a camera, you could try a regular digital SLR with a zoom lens to record the occultation into a video file. (Recommended settings: highest ISO, maximum zoom, widest aperture, and 30 frames per second at 1/30th second exposure). Record for at least two minutes before and two minutes after the predicted time to make sure you catch everything.

When you’re done, you can visit the public data reporting page at and upload your results.

What will we learn?

When the IOTA combines all of the time measurements from all of the different locations, it will be able to draw a rough silouette of the asteroid that will give us an idea of both the size and the shape of it; you can see an example here. Given that large chunks of rocks pass Earth at high speed all the time, and frequently hit Earth, it’s a very good idea to get as much information as possible about everything that is zipping about up there.

If you are interested in learning more about the 163 Erigone observation, check out the IOTA FAQ on their webpage here.

Good luck asteroid spotting!

Chandra Clarke is a Webby Honoree-winning blogger, a highly successful entrepreneur, and an author. Her book Be the Change: Saving the World with Citizen Science is available at Amazon. You can reach her at chandraclarke [at] gmail dot com.