Quote:
Originally Posted by allan gould
It may be a cheap way to broad band H alpha imaging?
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Broadband H-alpha imaging would simply be using a red filter. Traditionally H-alpha filters come in 4.5nm through to 13nm band sizes. There is nothing broad about these band sizes. They all transmit a very narrow window of light. Producing and testing narrowband filters isn't cheap, so I can't imagine a "so called" cheap alternative especially combining two broadband filters as a light cutoff mechanism.