H Alpha filter query

Every time I image with the Astronomik H Alpha filter I get an west to east gradient. The gradient is not uniform but banded. Is it a problem with the filter or do you think its due to the sensitivity of the ccd. This image shows what I mean

Nice image of the Rosette.

Are you sure it's not a light source?
Have you tried rotating the camera relative to the filter?

Tried a few things Michael. I have noticed it is worse on moonlite nights but I understood that the H alpha would cut through this.

It should do, and it should be even across the image.

If you're sure it's not the camera or stray light, then I would send back the filter.

All other filters give an even background. If anyone wants I can post them the filter to test it out (and of course return it)

what do you mean "return it" ???

What diameter is it?