Winter officially begins at 12:47 p.m. Monday. But this week, we find ourselves with a marvelous miscellany of fall sights in the sky.

Sirius twinkles: The brightest star in the sky, Sirius, rises between 7:30 p.m. and 8 p.m. this week. And once it gets just high enough to escape the thickest air and haze near the horizon, there is something other than its glorious brightness to admire: the pulsing of its light through an ever-changing assortment of colors.

The star's true hue is blue-white. But when it shines through extra turbulence low in the sky, the different wavelengths get separated, so the star shoots and throbs with darting rays of red, blue, green and many other colors.

Pairings of the moon and Mercury: The moon passes through its invisible new moon phase Wednesday but by Thursday or Friday night, we should spot it low in the southwest sky at dusk. Thirty minutes after sunset Thursday, binoculars will help you find the ultra-thin lunar crescent down near the horizon much less than one fist-width at arm's length to the lower right of a point of light - the elusive planet Mercury. Forty-five minutes after sunset Friday, the thicker lunar crescent will be higher, and located to the upper left of Mercury.

Jupiter and Neptune conjunction: A conjunction is a close meeting of two celestial objects. This week is the year's last of three conjunctions between bright Jupiter and dim Neptune, and there will not be another for a dozen years.

On Sunday and Monday, the night of their closest encounter, Jupiter and Neptune will be only about a half-degree apart - only about one-third the width of your little finger at arm's length.

But you will need a telescope to see faint Neptune - especially since the moon, by then a thick, bright crescent, will be near them in the southwest sky. You will also need a finder chart to identify which speck near Jupiter is Neptune. Try the Web site:

Neptune is much fainter than the four big moons of Jupiter that dance around their parent planet.

Mars and Regulus: Mars and star Regulus can be seen easily with unaided eyes. Mars rises north of east between 8:30 p.m. and 9 p.m. and Regulus less than an hour later. Mars is the real prize for its orange-gold steady glow and now outshines all the stars except Sirius.

And Mars is getting rapidly brighter - and rapidly bigger in telescopes - as we approach our next encounter with it just more than a month from now. But this week is when Mars and the much less bright Regulus, heart of Leo the Lion, reach a minimum separation of just more than 10 degrees - the width of your fist at arm's length.

Mars will be moving away from Regulus in an amazing example of retrograde motion, or backward movement, these next few months.

Fred Schaaf is a local author and astronomer. He can be reached at: