Polarizing filters - Uses besides the moon?

Is there any use for a polarizing filter besides the moon?

Also, in the conversation of the moon and polarizing/ND filters, what are their advantages over stopping down the scope? Most scopes come with a cap that has a stopping down hole in it from the factory.

Thanks

David

Using a polarizer is preferred to stopping down in good seeing, due to preserving the increased resolving power of the larger aperture. You also cut down on certain components of seeing disturbances.

If seeing is really bad, stopping down helps because your scope will not resolve larger pockets of disturbed air. You may see the image shift in apparent position as the air pockets pass through your field of view, but distort less. The tradeoff is you also lose resolving power on what you're observing.

Polarizers are a great brighness control on brighter planets too. You often see more detail in scopes of larger apertures.