Why would you limit yourself to the cheap optics and low resolution of a p900 when far better option exist? It has a tiny light gathering capability (the actual size of the lens element) and a small sensor, not well suited to this kind of imaging. It's no surprise it doesn't do a good job. That's why anyone who is serious about astrophotography has a telescope like I linked earlier, and an slr or milc camera with a larger (APS-C or full frame) sensor for image capture.

The p900 is a toy vs what people use for capturing actual good astro images.