How do I process my NB data

[nightster]

I got my first CCD in the spring right before the clouds moved in for the summer.  The fall clear dry air has arrived along with nebulas.  Last night I got my first try at capturing NB data from the wizard.  I got a solid 7 hours equally divided between each of the three filters.  Those subs are calibrated, aligned and stacked and look rather good to my sophomore eye. Funny thing is I'm not sure what the next step should be. Any pointers? 

[swag72]

If you have data from all three filters then I guess you are looking at processing some form of Hubble palette.

FIrstly take your three filters and assign them to individual channels. Put Ha into the Green, OIII into the Blue and SII into the Red channel. Then start to stretch the image and you will begin to see something probably rather green looking as Ha is normally the filter that has the most dominant data, 

From there follow this excellent guide from Bob Franke that shows you how to manipulate the colours in Photoshop using the colour select tool. Its better than anything I could type

Hope that helps.

[nightster]

Thanks for the reply and Congratulations on the Astronomy Now image. It is a beauty. I get that magazine many weeks after it first comes out and it is great to see images from people that post here get published.

I captured with all three filters without any specific palette in mind. I know you prefer the Bi-Color (Ha and Oiii?) and I want to learn that technique eventually. For me, I am trying to take small steps up the processing skills ladder. I will deep dive into the link you provided.

Couple of specific questions: Where does does the detail come from since there is no Lum? How much noise reduction is necessary for processing the NB stacks? I assume there shouldn't be much NR at all as that could destroy detail. Lastly, I got a little more that an 2 hours per filter line but I got 3 nights of clear and dark forecast ahead, I am assuming that is not enough time and should continue to focus on The Wizard. How much time should I be setting as a goal when capturing NB light?

[fwm891]

As your just beginning try processing what you have but carry on collecting data and add that in to the existing data. Process that and see the improvement the extra data gives you and continue gathering sub frames until you feel the need to move on.

Keep your data so as your processing improves you can go back and re-work the older subs with the newly acquired skills. The more data you have the easier it is to process as noise reduces and signal grows.

[nightster]

I am noticing the Ha stars seemed slightly bloated vs the Oiii and Sii. I had very low FWHM on the Ha filter.  Is this normal for that filter?  Its a 12nm Astronomik.

[swag72]

Regarding the detail I use the Ha data as a luminance layer. To that end I mash the Ha and OIII colour layer as required and then the Ha overlay adds the detail back in - Presto!

I am a fan of lots of data - I am looking at the moment at 25x1800s on each filter on a target I am looking at right now. It may be a pain when collecting it, but it will make it easier to process.

I normally found that the Ha has smaller stars than the OIII certainly. You can split the channels at an early processing stage, make the OIII smaller then recombine. 

[ollypenrice]

What about the stretch? I go for a very aggressive series of curves in Ha, though they become less aggressive each time.

A first curve might look like this.

Olly

[carastro]

No-one has yet mentioned registering the images.  The chances are your images will be pretty good if taken the same evening, but you might need to slide around the different filters (within channels to make all the stars line up.  

Consider if you took that data on different evenings, or even different set up dates, and the resulting filters are perhaps rotated to each other.  There are various software for lining up the images but I recommend the purchase of Registar as this does the job excellently.  

Yes I use the Ha as the luminance or detail channel and normally find the Oiii stars are larger once the different filters have been stretched.  This is a pain to sort out, but I do pretty much the same as Sara but much as I would like lots of data, English weather and LP home skies limits what I can get.  

Carole 

[nightster]

As far as the stretching in PS, is it Curves then Levels back to Curves until the desired contrast is achieved or. And is this done with each filter line Before adding them to a channel or after they have been combined.  I do add them to a channel and not a layer, correct?  

Carole, I've done all my Calibration, Registrations and Stacking in PI.  It seems to work well for me.  I used Flats for each filter and BIAS no darks, but I think I need to research using Bias only a bit more.  I'm gonna do my best to stay on this target next 3 nights and aim 7 hours per filter.

Ha as a Lum, got it, I need to check each of my Ha subs to see why that line has stars larger than the Oiii/Sii.  I know I broke a cardinal rule and did not refocus between filters, work night and I need a little sleep. Hoping to get a motor focus this winter to automate this function.

[nightster]

First try. Not great, but a start I suppose.