All the HA is the red channel. So discard the G and B. For O3 you will find that the O3 is recorded in both the G and B channels almost equally. So in this case dicard the red channel. This is why O3 is a lovely cyan colour. Cyan is the absence of red in an additive colour system.
The Bayer filters in a colour DSLR stop any useful light getting to the other channels. If you do use them you are basically only adding noise.
For something like the Helix Neb which is nearly all HA and O3 you will get what looks like a 'natural' colour image if you assign colours thus.
HA red to RED Channel
O3 green to GREEN Channel
O3 blue to BLUE Channel
See here
http://www.iceinspace.com.au/forum/s...light=achromat
and here
http://www.iceinspace.com.au/forum/s...light=achromat
Bert