[Craig_]

Originally Posted by Atmos

Good detail and nicely resolved The colours do look good, you'll never get an accurate SHO colour palette but you've done well to get close with just the Ha and OIII emissions

Thanks

Originally Posted by Placidus

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

Thanks for the comments and wealth of insight on Sii I guess the reason I don’t already have one is that Sii has a rep for being a fairly weak emission on most objects and given with an OSC I’d only be using 25% of the pixels to gather Sii data, I imagine I’d need very long subs and a large amount of total integration to gather anything useful in all but the richest Sii objects? Ha being much more prominent (typically) seems viable with an OSC despite the same limitations of it only hitting 25% of your pixels. Maybe someone needs to develop an Sii and Oiii dual band pass filter in the same vein as the plethora of Ha and Oiii ones - at least then I could be gathering more Oiii data at the same time

I’m really looking forward to imaging Tarantula Nebula actually and just ordered a bigger OTA (Esprit 120) which should do nicely on that object when it’s a bit higher in the sky. A mono camera is on my wish list but I don’t have much interest in the tiny pixels of the 183MM and the 1600MM whilst a workhorse for many, I feel a bit ripped off paying $2000 for something with such an old sensor (12 bit ADC, micro lens diffraction issues etc.) A 6200MM would be a dream but a bit much I think... I’ve been really really impressed with the 533MC sensor but OSC certainly has its limitations.