Hydrogen Alpha filters for dummies

[DavidNg (David)]

Hi,

I bought a secondhand CCD awhile ago which came with a set of LRGB, S, O and 2 HA filters, one is darker than the other when viewed with naked eyes. What are the difference between the two and when to use one or other?

Help appreciated.

David

[Lee]

They are probably different bandpass filters - do they give any indication to their specs on the rim of the filters?? I have an Astronomik 12nm HA filter, I know Astrodon make one at 3nm.... the lower the bandpass, the less light is let through, and you get a higher contrast image, with longer exposures needed....

[DavidNg (David)]

Thank you Lee for your explanation. I will have a closer look for specs when the filter wheel opened.

[pluto (Hugh)]

Even knowing the brand might help, my Baader Ha filter is 7nm.

[DavidNg (David)]

Originally Posted by pluto

Even knowing the brand might help, my Baader Ha filter is 7nm.

Thanks Pluto, I will find out if there is any logo or mark on the filter rim when it is open.