Attempting HOO

[rubecula]

This is the first time I've tried to create an HOO image.  I'm not that impressed with my result after the third go at developing the images.  The subs taken with an Atik 383L+ were: Ha 15 x 600s; OIII 22 x 600s and SII 15 x 600s all at -20C.  After stacking in DSS and a preliminary stretch in PS I decided to forget the SII as there was so little data in it and so I went for HOO using Steve Cannistra's technique.  Here's the result:

 

I've not tried reducing the noise and I know that I have some eggy starts which I'll have to try to sort out. 

Having looked at others images of this subject and trying to get an acceptable colour balance using Channel Mixer and/or Selective Colour in PS I am quite disappointed.  I've struggled to get any distinction between the Ha and OIII.  I'm surprised how much blue there is in the background and stars so that when I try to bring up the blue in the nebula the background gets all too blue.  I don't think that either the red or the blue is right.

I'm hoping for a pointer as to whether the problem is my lack of development skills or lack of sufficient data or probably both?

Thanks

[tooth_dr]

Hey Robin.

It does look quite pinky blue, and I see what you mean about the lack of distinction.  What do the stacks look like?   Last night I collected about 1.5 hours Ha and 1.5 hours Oiii with the same camera.  I plan to have a go at processing it tonight.  I'll try that method you used and see if it yields similar results.  I think we are also using the same filters.

[carastro]

Nothing wrong with that.  Just Go into image adjust/selective colour and play with the sliders, particularly in the blue range, until you get colours that please you.

Carole

[alan potts]

The image is very nice and I am sure one of the more experienced can help with the colour, never easy first time, says he that has never tried it.

Alan

[DaveS]

I use AstroArt (Currently 5, but will get 7 soon) and in Trichomy just drop the H stack into the Red channel, and the O stack into both the Green and Blue. Click Auto levels, and white balance and something resembling a HOO comes out. Further processing then occurs.

Edit: This is an HOO of the Crescent using the above method. Trouble is there's not enough [OIII]

Edited August 29, 2019 by DaveS

[rubecula]

Ah Dave, I do like your image, I wish mine looked something like that.

Here are the two stacks stretched before I tried to combine them, Ha first:

Then OIII

 

Have I stretched them too much>

Thanks

[DaveS]

Hi Robin, did a *very* quick HOO on your stacks, just following my quick 'n' dirty method

This is just Trichromy with H in red, O in green and blue. followed by auto balance and white balance. Not too bad at all really.

[david_taurus83]

I know CCDs are very different to the CMOS type I use but I'd have thought youd have much more signal in the stacks? What do your Ha subs look like?

[tooth_dr]

Hi Robin

I had a look at my own data, and did a crop like yours.  I've only 3 hours data, but it does look similar to what @DaveS achieved.  (ignore the stars, something wasnt lined up right).  It looks like something has went awry in your processing.

Edited August 29, 2019 by tooth_dr

[rubecula]

There is more data in the subs than those stacks show but when I first developed them I had even more trouble with blue in the background sky, so in those above I held it back a bit.  I even tried just selecting the nebula to stretch and colourise but that didn't look right either.  The more I look at your images the worse mine look.

I'm still surprised to see how much OIII there is in the background sky, it doesn't appear to be there with either of your examples above.  I'm going to go right back to the beginning and re-stack in DSS and try again.  I also may download a trial copy of  AstroArt and see what that makes of them.

Thanks all for your help,

[DaveS]

One thing I would try, and it's often a case of "suck it and see" is just make the stacks and do whatever gradient removal you chose, *then* do the colour stacking followed by stretch or DDP (In AstroArt). I often go through several iterations of Histogram Stretch.

 

Edit: If you're trialing AstroArt give the stacking a go, I found it much better than DSS.

Edited August 30, 2019 by DaveS

[rubecula]

Dave, it seems our processing is quite different.  I stack in DSS, in this case didn't do gradient removal, load into Photoshop (on Mac), stretch - these had at least 5 gentle stretches using the Curves tool, then load into new three layer file.  At this point things look quite good, but when I add adjustment layers and colourise the 3 layers (red, blue, blue) it all goes wrong.

I see that AstroArt is a windows app only.  That means I'll have to give it a try on my observatory laptop rather the Mac with a much larger screen.  Still, if the results are better then that'll have to be the way of it!

Cheers,

[DaveS]

Oddly I've never got involved with PS, even though I've done a fair bit of photography, I think the cost, and then Adobe product philosophy put me off, so I do all my stacking and post in AstroArt. You could try Pixinsight, something I've been promising myself to get involved with.

I thought there was a way of running Windows in a Mac environment? Again not something I'm familiar with, being Windows only.

[rubecula]

Mmmm......I don't know how I managed it but I've obviously done something seriously wrong (embarassingly so) in PS as this is what dropping the stacks into Trichromy in AstroArt on the laptop produced:

So, it's me not the data.  I'll have to work on trying to produce something like this with PS as I'd rather not have to buy yet another product unless I can help it.

 

[DaveS]

That's *much* more like it.

I guess we're on opposite sides of the same coin, as I have AstroArt and don't want to buy PS, while you have PS and, understandably, don't want to buy AstroArt. Mind you AA is cheaper and doesn't tie you into a rental contract.

[rubecula]

One more thing (I promise I won't keep pestering you) how do you keep your stars so tight?

[DaveS]

Probably a combination of 3nm filters and a superb mount, ASA DDM60 pro, no longer made alas. I don't do anything special in post, but I do keep a close eye on the stars during DDP to avoid either bloat or dark halos, both of which can occur.

[rubecula]

Thanks all for your help above.  I think I'm beginning to get a grip of developing narrowband images.  Obviously still a lot to learn but I'm much happier with these first two attempts at HOO.  Now to think about what to do with the stars 🤔

 

 

Thanks

[tooth_dr]

52 minutes ago, rubecula said:

Thanks all for your help above.  I think I'm beginning to get a grip of developing narrowband images.  Obviously still a lot to learn but I'm much happier with these first two attempts at HOO.  Now to think about what to do with the stars 🤔

 

 

Thanks

Robin, those look great. A major improvement 

[DaveS]

Agreed, very much better and a big leap in the right direction.

Processed in PS?