How to Find an Asteroid

Thursday, May 19 2005 @ 10:38 pm EDT

Contributed by: Marcus

Asteroid 1/Ceres - The first asteroid discovered, Ceres shows its best face to date in this Hubble Space Telescope Near-Infrared image. At nearly 600 miles in diameter, not even Hubble can see much detail, yet it's obvious that Ceres is spherical. Marcus Blair's observation and description of Ceres appearing as a small "disk" is an accurate description. - Bob Moody
We’ve had great, clear skies the last couple of nights, so I’ve been doing a lot of observing. On Monday night, despite the nearly half moon, I spotted several Messier objects to add to my log. All of this is made much easier by my Meade ETX 90 scope with the “go to” feature. It’s becoming second-nature to set up this scope and have it locked on and accurate within a few minutes. The only trade-off is the lack of aperture, but a true beginner like me can greatly benefit from the go-to function.

Despite what some might say, having a go-to scope is not cheapening the experience for me, but is enriching it. I struggled for years to find things in the sky. Now, I am able to find them, but best of all, I learn and remember their positions. For example, once I finally locate M82 with the ETX, I will be able to find it next time without the go-to feature because I know (a) what it looks like and (b) where to find it.

Monday night I decided to try something entirely different, so I was scrolling through the AutoStar controller’s memory banks of thousands of objects. I came across the “Asteroids” category and wondered whether I could find one. I knew Ceres is the largest known asteroid, so I told the scope to go to it.

The scope slewed to an area containing several star-like objects. Nothing was obviously an asteroid. I looked at the area with different magnifications and finally decided the brightest object in the field was Ceres, but I wasn’t sure.

Tuesday, I decided I had to discover which object was Ceres. I went to, an extremely useful Web site on which you can input your observing location and discover the locations of thousands of things. It also will tell you when satellites, the International Space Station, and the Hubble Space Telescope will be sailing over your area. Luckily, it also has a good “minor planets” section that has detailed diagrams of what will be in the eyepiece when you look for things like Ceres.

I printed out the diagram of Ceres’ location in Libra and waited for dusk. I turned the ETX toward the supposed location of Ceres and BAM! – with the help of the diagram, the asteroid basically jumped out of the eyepiece! It became very obviously a planetoid body. What I had thought was Ceres was really a star that the asteroid is fast approaching. I compared the two. When you look for asteroids, you will notice that stars shed light and twinkle a bit, while asteroids, like planets, will reflect light, appearing much more solid, immediate, close, and pale than the stars. Ceres appeared to me as a salmon-colored disk about 3-5 times larger than one of Jupiter’s moons (though far less bright). There are many other asteroids to be found as well. Vesta is the brightest, though it currently is in Auriga and below the horizon at dusk. The Astronomical League awards an asteroid observing certificate similar to the Messier certificate.

It’s astonishing to have observed an asteroid. I’m going to track it again tonight and tomorrow night, just to be 100 percent sure (this is science, after all ), that I have indeed seen Ceres. For those of who may be interested in seeing it tonight, go to this page to see it’s current location:

I imagine this is also a good way to search for Pluto, though I lack the aperture for that. I encourage everyone to give this activity a shot. If Piazzi could see this rock in the year 1801, you can certainly see it today.

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