Using the above guideline, a maximum magnification of 400x is all that's needed. On good nights, you should be able to observe faint star clusters, nebulas, and galaxies. You should even see individual stars in the cores of the clusters and some of the structure of the galaxies. Brighter nearby objects should be visible in great detail. You can study the moon's craters, the "canals" on Mars, and the rings of Jupiter and Saturn with ease.