Hello All... I'm inquiring about filters to correct color shift during long exposures. Long as in Hours! My latest project is star trail photography such as the attached image.

The film manufactures recommend filters to use for their films to correct color shift during long exposures but they are only talking seconds not hours. I picked up a copy of The Complete Tiffin Filter Manual, it's really excellent but I'm confused about Primary, Secondary and Complimentary colors, and how they interact with each other. And more importantly which filters will block or pass what color. If I'm interpreting the book correctly wouldn't a cyan filter adjust the magenta out to give me a more "natural" looking image? Though I'm not sure what natural is exactly!

This image is a 4.5 hr exposure @ f8 on Provia 100 film. And on a related note... Which film would work best for this? I rummaged in the back of the frig and came across this Fuji 35mm which I'm experimenting with, dialing in F-stops and exposure times, before I start to burn the Expensive stuff. I've always heard Fuji is a "cooler" film with a blue cast while Kodak film is "warmer" so they will react differently. If anyone has experience with this technique I'd sure appreciate your comments... you'll save me a lot of time and money experimenting.

Thanks... Dave