[AZ-Observing] Ephemeris and Map for 2005 YU55
- From: Tom Polakis <tpolakis@xxxxxxx>
- To: AZ-Observing@xxxxxxxxxxxxx, evac@xxxxxxxxxxxxxx
- Date: Tue, 8 Nov 2011 14:19:22 -0500
It looks like we will have a clear night for tonight's close flyby of the
asteroid 2005 YU55. I used JPL's Horizons ephemeris generator to create a
table that shows coordinates for Phoenix between 7 and 10 p.m. Since the
asteroid is close enough for parallax to become a factor, the apparent position
against a star field shifts based on one's location on the Earth. Sky &
Telescope created a clever chart that makes it easy to offset for your
location. In addition to the ephemeris, I plotted the path in blue for
Phoenix, which should be close enough for all of Arizona. It's uploaded to
this site.
http://members.cox.net/tpolakis/astro/2005YU55_path.pdf
The expected magnitude peak is around 11, so S&T's estimate of at least a
6-inch scope sounds pretty good, since the moon will be bright. The key is
pointing in the correct position for the minute of your observation, since it
will moving quickly. At 6 degrees per hour, the position changes by the
diameter of the moon in only five minutes. If you can view it at a
magnification of 100x or above, the asteroid should be moving in 'real time' at
a rate of 6 arcseconds every second of time. Doing the trig for angular size,
the quarter mile asteroid at a distance of 200,000 miles produces a disc that
is a quarter of an arcsecond across, so too small to resolve in any scope.
Tom
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