Saturday, March 5, 2022

Made in USA

I have been looking for some H-alpha filters not made in China.  What is an H-alpha filter?  It is a narrow band (typically 3 to 5 nm wide) filter used to catch only the brightest parts of nebulae on astrophotographs.   It is the light emitted when a hydrogen electron drops from shell level 3 to level 1 (or more precisely from energy level 3 to level 1).  This makes nebulae such as M42 stand out brighter than they otherwise would.

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