Sinus Iridum, or Bay of Rainbows, is one of the most charming features of the moon. He goes out into the Mare Imbrium and was named by the famous lunar observer Giovanni Riccioli on your map drawn in 1651. In those days, of course, it was believed that the dark areas were really seas and that the moon could very well be a world fit for life.

Sinus Iridum is called bay, but is actually a crater whose wall off was virtually destroyed; only a few, very low disconnected fragments can be traced. Elsewhere the 'wall' mountain is continuous and quite high if there highlighting the Montes Jura, although the outer edge is disturbed by the prominent crater Bianchini. The continuous section is bounded by two covers, Promontorium Heraclides and Promontorium Laplace.

Iridum The floor slopes downwardly from the Imbrium, so that the opposite side is about 200 feet (61 meters) less than the sea level. There is nothing like this anywhere else on the moon, but the sequence of events seems to be quite simple. The very Mare was formed during the lunar time in his honor - the Imbrium - which ended more than three billion years, so that is after the Great bombing. The Iridum impact occurred before the great lava-floods, which represents the flood wall toward the sea.

I said Sinus Iridum is one of the most charming features of the moon. For this, you should catch it at the right time. As the sun rises over him, the mountainous border is illuminated on the one hand, and the tops of the peaks catch the sunlight, while the downstairs is still in darkness. The result is that the wall appears to be out beyond the terminator, giving the impression that is completely separate from the main body of the Moon. Lunar observers refer to this as the "Jewelled Handle".

This occurs once every lunation (lunar cycle), well before the full moon, but does not last long, and as the sun creeps on the lower floor is in effect 'handle' disappears. It is fascinating to follow the changes with increasing altitude of the sun; even a small telescope will show them as well. The floor itself is very smooth, and just a few fairly well marked cratereletas.

Sinus Iridum can always be identified when it is lit by the sun; notice the two craters well marked Laplace and Helicon in Mare Imbrium north. Except at the time of sunrise, the area looks quite common - but at the coming of the next lunation, make sure you do not forget to pay attention to the glory of the Jewelled Handle