And Ketu.

Similar questions arise for Ketu too. Ketu is the other NODE of moon, the point on Ecliptic where moon crosses it from north to south. It will not be diametrically opposite to previous Rahu position but a little away. ketu is also only a position and at Ketu there is nothing. Like rahu, ketu also moves backwards in successive moon orbits. It can hardly be described as motion of Ketu as it is not a continuous motion like planets but a series of spots.

As in case of Rahu, I wonder whether our ancient Astronomers had the same concept of Ketu as the current one. With visual observation, how can one decide where the moon crosses the Ecliptic? As Ketu is supposed to cause Lunar Eclipse, did they understand Ketu as Earth's shadow? It is known that Lunar Eclipse is caused by Moon passing through Earth's shadow (Umbra and Penumbra). How do the old astronomers describe the movement of Ketu and specify its position at any given time?

Moon will pass through Ketu in every orbit. Only if it happens to be a Full moon night, there will be a Lunar Eclipse. Even if Sun and Moon are not exactly 180 degrees apart but + - 6 degrees, a partial Lunar Eclipse is possible when mMoon is at Ketu. This is probably the explanation why Lunar Eclipses are more frequent compared to Solar Eclipses. For Solar Eclipse to occur, Sun must be at Rahu Node, (which itself does not happen frequently. Does it happen once in each Year?) and moon too must be at the same place on Ecliptic, not too much above or below.

I am interested in knowing what exactly our ancestors understood by Rahu and Ketu. I am not convinced that they understood them as Nodes of Moon on Ecliptic. I invite readers to share their information on these points.