The solar system's three innermost planets, together with Earth, will be low in the southwestern sky this weekend. They are Mars, Venus and Mercury. And if you are looking for a fourth planet, look down and see the Earth. They'll be joined by a thin waxing crescent moon next Thursday night.

Everyone will be able to find Venus low in the sky, but try looking for Mercury. Mercury is here only for a couple of days. The planet is just to the right of Venus. If you can spot Mercury you deserve a prize. It is no where near as bright as Venus. Still, it is worthy making the effort to see. Mercury is one of the hardest visual planets to spot, since it is always close to the horizon of either the setting or the rising sun.

Mars is easier to spot. Look to the left of Venus for two bright celestial objects. The bright star Regulus is nearest to Venus. But look a little farther way for the ruby red planet Mars.

The crescent moon will first appear closest to the horizon on Wednesday night, but few will see it being so close to the sight of the setting sun. On Wednesday night, still hard to see, the thin crescent moon will appear right above Mercury.

You'll need a clear view of the western sky, unencumbered by trees or hills. The best place to look is at Menemsha, almost any where near the water of Aquinnah, West Chop overlook and in other places where there is a clear view of the area of the setting sun.