Which HA and OIII filter do I get?

[ncjunk]

Hi,

Looking at getting an HA filter and OIII filter to go with some Baader LRGB filters I have just ordered but there seem to be a number of different wavelength filters. Which do I need for bringing out the Nebulosity in Galaxys or, say, in the horse head neb.

HA 7nm or 35nm?

Thanks

Neil C

[OzDave]

Good question, i'd like to know the answer too.

[shaunster]

Go for 7nm for best results, 35nm will let through more background light as its a broader bandpass

[Tim]

Agreed. You can use the 7nm in full moonlight with little detriment to the image.

If you have the newer LRGB Baaders then the Ha and O3 filters are parfocal with them too

[ncjunk]

Excellent!

I am getting the newer filters from FLO and I was thinking of getting the HA specifically to aid when there is a full moon as at present the subs get a bit washed out. (I want to get some usable subs during full moon!)

I wasn´t thinking of the rating as being the bandpass width....don´t know why I didn´t think of that.

So 7nm it is then.

Thanks again