|
Peter,
The bandwidth required for safe Ha observing (and imaging) of the sun is a magnitude smaller than any Ha DSO filter. It needs around a 1A pass width (0.1nm)
To achieve this fine resolution the professional solar Ha filters are actually a combination of at least two filter elements - an etalon and a blocking filter. The quality requirements are MUCH higher than conventional filters and so unfortunately is the pricing!!
Coronado, Lunt and Daystar all produce good solar Ha filters.
HTH
|