Notes

I started these pages going pretty much on theory, but I've gone out and observed each of the planets and augmented my projections with actual observations. I rediscovered that although Uranus is an easy binocular object, it's a hopeless naked eye object from my home in Fairfax, and it can be difficult to find in binoculars because of nearby stars with similar magnitudes. It's around magnitude 5.5, but I found I need to include stars to magnitude 7 on the charts so I could be sure which of the objects I could see was Uranus. I have been able to spot it without binoculars from a dark site.

In 1999 both Uranus and Neptune were in the constellation of Capricorn. Neptune still is, but Uranus has now moved into Aquarius. To see an animation of their movement from May 2003 to January 2004 click here. The animation includes the dramatic retograde movement of Mars. A good way to locate Capricorn is to start with alpha Cap. This is an interesting multiple star and is easy to identify.

You'll need binoculars to locate Neptune. Don't even try less than an hour before sunrise or after sunset because the twilight overwhelms this dim planet. I tried numerous times to locate it with binoculars from my home, and it hovers at the edge of detection.

For some additional insight into locating Uranus, Neptune, and Pluto see my article "The Elusive Wanderers"

I've tried to spot Mercury, Saturn, and Mars less than an hour after sunset and had minimal success. I spotted Saturn an hour before sunrise on June 16, 1999 at 4:45 a.m. It was 14.5º above the horizon and shining at magnitude 2.1. At 5:50 am (31 minutes before sunrise) on the morning of August 10, 1999, I spotted the Moon and Mercury. The sky was clear except, of course, along the horizon where I needed to look. I used 10x50 binoculars to scan the horizon and spotted the Moon peeking between the clouds. Raising my gaze about 5 degrees brought Mercury into view. Without the binoculars I was able to see the Moon, but Mercury was lost in the morning twilight. The Moon's altitude was 6 degrees, and according to SkyChart III, it was 1% illuminated. Mercury was shining at magnitude -2.2 and 10 degrees above the horizon. I expect Mercury would have been visible without optical aid 15 - 20 minutes earlier.

2004 November 17, 6:03 AM

Found Mars in the pre-dawn sky from a parking lot in Gaithersburg, MD. Mars, shining at magnitude 1.7, was 9.2º above the horizon. Sunrise was at 6:53, so it was 50 minutes before sunrise with severly light polluted, but clear, skies. I used a pair of 8x22 binoculars to locate the planet, but then was able to see its faint flicker without optical aid. There was only one small cloud in the sky, but it was right next to Mars and may have been partially obscuring the view.

Over the course of a single night a planet will move across the sky from East to West, but when a planet is observed from one night to the next it usually appears to move from West to East against the background stars. However, sometimes the planet's motion will appear to reverse direction, and the planet will, for a short time, move from East to West against the background constellations. This reversal is known as retrograde motion. This animation illustrating retrograde motion is from the University of Tennessee's Astronomy 161 Solar System lectures. Addtional illustrations of retrograde motion can be found here, here, and here.

Retrograde Motion Illustration (Courtesy University of Tennessee's Astronomy 161 Solar System lectures)

Updated on 2004-11-17