stupid question

I have a canon Xsi that I wanna try piggyback w/75-300mm lens.....it came with a skylight 1a filter....is there any advantage in using this filter or would it be better off? Should be the same setup before taking dark,flat and bias.

Thanks for any advice
Gary

I would take it off. If you leave it on, you will get ghost images of the brighter objects in the field from reflections off the lens. I spoiled some otherwise good shots like that!

I second Steves's advice. Don't use the filter because it will create reflections. I know about this first hand.

Joe