|
I've had the opportunity of "testing" various filters with my spectroscope ( similar to Buil's tests) and find that the leakage of Hb into some OIII filters ( these emmision lines are very close together) can help visual observers of planetary nebulae. A good Light pollution filter is a better long term buy, in my opinion than very narrow filters which are really only used by DSO observers with Mono cameras.
My 2c
|