So... I've got a Circular Polariser

[silverJON]

John also asked "I just put it on top of my UV(protection) filter, which I now realise may have been a mistake. Anyone able to shed some light on this?"

I would also like to hear if this is OK.

There's nothing wrong with stacking filters, as long as you bear in mind that each piece of glass reduces image quality by some amount.

The only danger is that of vignetting - if the filters are stacked sufficiently high (just a single overly thick filter will do on some wide lenses) then the corners of the picture will be darkened.

So, only stack filters if you need them all, and bear in mind the effects.

 

[laser_jock99]

Something to be aware of if using a circ pol with a very wide angle lens is possible un-even effect in the sky (as seen in some previous posts). It's hard to notice when your taking the shot but could spoil an otherwise good photo.