ngc1499 in SII

[Ivor]

Revisited ngc1499 Friday night and managed to get some SII data (still no OIII data despite seeing it in some other images) but I'm really struggling to get a good stretch on it.



This is the best I good do but I'm concerned with the histogram, I've had to heavily clip the black to acheive it.



I've used FITS Liberator to perform the stretch trying log(x) and arcsinh(x) I'd be interest to see how others would approach it?

I've put the FITS file here

https://www.dropbox.com/s/ne6dtm2o1yrxoc3/ngc1499_S_900_7_merged.fit

Not sure if I've got the dropbox thing working I couldn't see a way to make it public

[Carole]

I had a "go" at this Ivor and found it quite difficult to bring out the Nebula without affecting the background sky.

Carole

[Rocket Pooch]

Hi Ivor,

With narrow band imaging you will find that the SII and O3, Hb normally require a much longer integration time, you may find you need 2-4x the exposure to bring these components out and even then they will not be as bright a Ha. 

NGC1499 is mainly Ha, so SII and O3 will need a lot of exposure.  It might be worth while seeing an emission spectrum of it to work out whats in there 1st.

Chris

[Carole]

Juste-read your post Ivor, is this Ha and Sii combined, or just Sii?

Carole

[Ivor]

I had a "go" at this Ivor and found it quite difficult to bring out the Nebula without affecting the background sky.

Glad to see it isn't just me and yes it is just the SII.

With narrow band imaging you will find that the SII and O3, Hb normally require a much longer integration time, you may find you need 2-4x the exposure to bring these components out and even then they will not be as bright a Ha.

NGC1499 is mainly Ha, so SII and O3 will need a lot of exposure.

I agree with what you are saying and I've based my subs length around an example on the net http://bf-astro.com/ngc1499nb.htm with my scope and my local environment.

As the weather has been rubbish I decided I shouldn't risk 30mins subs and 15mins would have to do instead, the SII image is based 7 subs of 900s @-30c over 2 nights, I'm not expecting this to be as good as the reference site however I was hoping for say a 1/3 of the SII and just a hint of OIII.


I guess I stared this topic from the viewpoint  SII 7 X 15mins @ -30C gave me this result is there different techniques I can use to get more out of the data available?

And subsequently is it worth acquiring more data?

I'm also slightly concerned there is something wrong with my setup, I've recently introduced a few new items (dew heaters, AA5, ASCOM, CdC) into the workflow. I'm happy with CdC/ ASCOM control but I'm using AA5 for my stacking now and I'm slightly concerned the dew heater is added some thermal gradient.

If you look at the OIII merged it has an odd result

https://www.dropbox.com/s/kj60ggdzbd4ubie/ngc1499_O_900_11_merged.fit




Thoughts?

[Carole]

Hmmm, I had similar problems with my O3 recently when I did my Crescent nebula.

Will watch the comments with interest.

Carole

[MarkS]

If you look at the OIII merged it has an odd result ...

Thoughts?

Did you use a flat frame?

[Ivor]

My first thought was flats (hence the light box posting the other day) as well when I looked at the subs on the night, so I pointed the scope at M42 after the merdian and the OIII shots came out fine. I can't post to flickr during the day to demostrate. It's worth noting the M42 subs were only 5 mins hence my thought about the dew heaters having a greater effect with time.

Weather permitting I'm planning to come to DSC on Saturday so maybe I can borrow someone's lightbox to try and eliminate flats.