Hi all, I'm planning my august work. I've purchased a Kenko R64 H-alpha cutoff filter. If I can expose about 30 minuts at f/4 without any filter, what exposure can I take with this filter without fogging too much the image? Thanks! Vicent. _______________________________________________ Astro-Photo mailing list Astro-Photo@seds.org http://seds.org/mailman/listinfo/astro-photo