Post by Chicago Astronomer - Astro Joe on Jun 18, 2005 1:22:05 GMT -6
Where to catch Comet Temple 1
From Starry Night Times...
NASA’s historic Deep Impact mission is set to climax on July 4th with the planned collision of a man-made projectile with a comet called 9P/Tempel 1. The 820-pound, washing-machine-sized “impactor” launched from the Deep Impact spacecraft will smash into the comet’s nucleus at 23,000 miles per hour, expelling ice and dust debris and gouging out a crater a couple of football fields wide and some 50 yards deep.
WHEN: Impact will occur around 0600 hours Universal Time July 4th, which is 11 PM Pacific Daylight Time on July 3rd.
WHO: Observers in the westernmost region of North America will be favorably positioned to view the impact, and sky-watchers around the world should have a good view shortly thereafter.
WHERE: Look for the comet low in the southwestern sky in the constellation Virgo. The comet will be faintly visible with just about any telescope or full-sized binocular.
WHY: By analyzing the blown-out debris and the freshly excavated crater itself, scientists expect to learn more about what comets are made of. And from that they hope to gain new insights into how the solar system was formed.
HOW: To get a good look at Comet Tempel 1, a telescope is the way to go. Any telescope design will do—refractor, reflector, or Cassegrain, but the bigger its optics, the more vivid the image will be. From a dark-sky site, a telescope with 4” optics should begin to reveal the comet’s hazy glow. (if you have a smaller telescope, go ahead and give it a try. You just might get lucky.) You’ll have better luck with an 8” or larger telescope, which will be a reflector or Schmidt-Cassegrain. Remember that moonlight will wash out the comet from June 8 to 23, so plan on starting your observations on the 24th, if you haven’t already, when the Moon comes up later in the evening.
To get the telescope pointed in the right direction, locate Spica in the finder scope and use your telescope’s slow-motion controls to center it on the finder’s crosshairs. Remember that the view in a typical finder scope will be upside-down compared to a normal view. If you’re using a star chart, rotate it 180 degrees to match the view in the finder scope. It’s also important to know how the image in the main telescope’s eyepiece compares to the star chart. In a reflector telescope the image will be upside-down. In a refractor or Cassegrain used with a “star diagonal” in front of the eyepiece, the view will be mirror-reversed, so you will have to mentally flip it back or else turn your star chart over and read it from behind to match the eyepiece view!
From Spica, move the telescope a few degrees in the direction of the comet using the mount’s slow-motion controls. Refer to the detailed star chart to determine where the comet should be relative to Spica. With a low-power eyepiece in the telescope’s focuser, see if you can identify the comet’s fuzzy glow. If you can’t, sweep the area a little with the slow-motion controls until you find it.
Once you have Tempel 1 in the eyepiece’s field of view, study its appearance for a while. Can you detect any shape to its diffuse tail? Now insert a higher-power eyepiece, one that provides 100x magnification or so. The view will be dimmer but you may resolve more structure. Try other magnifications using other eyepieces, too, if you have them.
Of course, after the impactor slams into the comet on July 3/4, it should become much easier to see. Will the blown-off debris cloud cause the comet to look any bigger, or just brighter? How soon after impact will its appearance start to change? And how long will the “extreme makeover” persist? Nobody has the answers to these questions right now. But with a good telescope, a good eye, and patient observation, you can have fun finding out!
A PDF of Deep Impact details can be found here: www.space.com/media/pdf/definal6142.pdf
