DSO with OIII in them

[Glider]

I'd taken some Ha of the Cocoon a few weeks ago and tried some OIII to go with it last night and got, absolutely nothing! Tried 15min subs, the same as I'd done before for the Ha and got just the faintest smudge so I was on the target!

Then rain appeared so packed up quickly without getting chance to slew and try a few other targets for comparison.

Was I fooling myself or was there high cloud or something else about?

Do Ha and OIII appear in some sort of 'ratio'?

[RobH]

They vary a lot.

M27 has tons of OIII, and it looks very different in Ha and OIII.

The Veil remnants are as strong in OIII as Ha, and very beautiful in this wavelength.

Rob.

[Glider]

I'd had a look at M27 last month and I guess I was expecting similar on the Cocoon.

I'll give it another go when I'm sure everything else is spot on, if there's still nothing I guess it's the nature of the target.

[riklaunim]

Planetary nebulae are rich in O-III and sometimes also in S-II, Ne, He, Ar emission. Also N-II in them may add to the H-alpha channel (unless you have very narrow H-a filter). Regions rich in hydrogen usually won't show any other emission (depending of the origin, supernovae remainments etc. may show other emission too)

[Ibbo!]

I think pick your target and go longggggg

PN's are good, as has been said but unfortunately they are normally small

Steve