The Ha and OIII data are looking very fine. Well done.
[ominous sounds of Mike getting up onto his High Horse]
The purpose of the SII is not to put red in the image, nor to stop it being green, nor to get a certain look. It is to find areas of recent ejection of star guts, most commonly in the form of a huge supernova remnant, but also from Wolf Rayet nebulas, and at the smallest scale, from planetary nebulas.
It is completely impossible to even begin to guess what the SII might look like from the OIII and H-alpha alone. Therefore, it should not be attempted.
[Happy sounds of Mike dismounting from High Horse].
You're already romping ahead there. Do get yourself an SII filter. Places where you'll quickly get results:
- Tarantula nebula
- Gabriela Mistral Nebula.
Both these show glorious SII emisision, well localized and separate from the general H-alpha.
The Chalice Nebula has a beautiful SNR and other features which only shows up in SII, but it is much more difficult. Just about any other super-violent region in the LMC and SMC, and any supernova remnant at all will show discretely localized SII, but don't start with those.
Thor's Helmet and Norma Bipolar Nebula are good examples of WR nebulas with good SII, the mechansim being entirely different from past supernova activity. The stuff is spewing out of a huge hot star right now, long before the explosion.
Another good one is the Dumbell nebula, a planetary nebula which looks quite different in SII. Again, the mechanism is completely different from the previous two. A much smaller more sun-like star has lost its atmosphere, but enough SII has been dredged up and blown off the beyond white-hot core for us to see.
Total waste of time are gentle star-forming regions where nothing much extra-violent has happened yet:
- Trifid nebula, Running Chicken. Not so much SII to be found, and what there is tends to be co-localized with H-alpha. That is of itself of great interest, but not one to practice on.
Anyways, welcome to broadband and keep up the superb work!
Best,
MnT