Sky watchers are being treated to their best view of Mars until 2001, with the mysterious Red Planet, Earth and the sun scheduled to be positioned in a straight line Tuesday.

Mars currently is about 20 times brighter than it was about a year ago, looking like a yellow-orange star in the northeast sky, said Alan MacRobert, associate editor at Sky and Telescope Magazine in Cambridge, Mass."This is a big time for amateur astronomers to get their last good look at Mars this century," MacRobert said Monday.

Alignment of Mars, Earth and the sun occurs about every two years, and Mars is closest to Earth around that time. Although the alignment, or "opposition," will occur about 3:30 p.m. Tuesday, Mars was actually closest to Earth - about 48 million miles away - on Nov. 19.

However, if viewers missed that chance, Mars still remains unusually brilliant. "Compared to a week ago, the difference in distance and brightness is very small," MacRobert said.

Mars rises about sunset, is highest in the sky about midnight and sets at sunrise. "Anybody can go out and look at it with the naked eye."

Except for Jupiter, which looks like a white star in the eastern sky, Mars is the brightest object in the night sky.