Re: (IAAC) Orion Natrium Filter

The filter that Yann is referring to is a broadband filter made by Orion
Optics UK and from my brief look at one of the early ones is a complete
waste of money. Their EHC filter is not too bad. Natrium as you suggested
is a corruption of the latin for sodium. Stear well away from this one Yann

At 15:06 28/05/98 -0400, you wrote:
>Oops - come to think of it, it's more likely these "Natrium" filters BLOCK 
>sodium than narrowly bandpass it... After all, at least in the US, much of
>artificial skyglow derives from sodium-vapor (Na emission) lighting. Is it 
>possible that "Natrium" is Orion's European name for their "Ultrablock"
>(similar to the Lumicon "UHC" filter)?
>Lew, awash in emission lines