Sadr region HaOSC

[Stub Mandrel]

Last night I got 11 reasonable 10-minute Ha subs before the cloud came in. I've added them as 75% luminance to my OSC data from 4 August. I think the yellow stars look a bit fierce.

 

[ollypenrice]

That's good.

I think it's a shame to add Ha as luminance, though, because it turns things pink and gives blue haloes around hot stars. In Photoshop (and maybe other layers based graphics packages) you can add the Ha to red in blend mode lighten and leave your stars unaffected because, in Ha, they are not brighter than the stars in red. This will also keep the reds redder and less pink.

Olly

[Stub Mandrel]

9 minutes ago, ollypenrice said:

In Photoshop (and maybe other layers based graphics packages) you can add the Ha to red in blend mode

I did try this but I got a bit lost! I'll have another go.

[MarsG76]

Nice one

[Stub Mandrel]

This is with Ha for red, it sent all the yellow stars green and made the blue ones a bit fierce so I used selective colour and HLVG to restore order!

A very different image. I think I need more practice at this, perhaps splitting the image, blending red and Ha, then recombining.

 

[ollypenrice]

What I do is get the Ha co-registered, select and copy it, then activate the RGB and split the channels. Make the red active and paste the Ha on top of it.  But then it's vital to change the blend mode to lighten. At this point you can get clever and manipulate the Ha layer while it's in situ over the red to make sure it's adding all it can and not lifting the background sky at all - or it will turn red in the result image. I do this adjusting in Curves but it isn't always necessary. Then flatten the Ha onto red and recombine the colour channels in RGB mode, being sure to put red in red, green in green and blue in blue.

You can't replace the red with Ha or mix it in with bend mode Normal because, as I suspect you found, the stars are much smaller in Ha so the star colour goes all over the place. It's blend mode Lighten which makes adding Ha to red easy.

Some people add the Ha in iterations but there is no need to do this. You can pile it on at full power and if it's changing the RGB image more than you want it to you just paste the HaRGB onto the original RGB in Layers and adjust the opacity to taste.

Olly

[Allinthehead]

I follow this tutorial http://bf-astro.com/tutorial/addHa.htm

Pretty much the same method as Olly but sometimes it helps to have a visual.

[Stub Mandrel]

Thanks @ollypenrice and @Allinthehead

In think the dreaded red background got me! I will revisit it later, when my eyes have readjusted ?

[ollypenrice]

1 hour ago, Allinthehead said:

I follow this tutorial http://bf-astro.com/tutorial/addHa.htm

Pretty much the same method as Olly but sometimes it helps to have a visual.

Yes, that's an interesting variation on essentially the same technique but, as you say, it shows the effect in real time. I'll be giving that a try! I think there's a case for using Curves as well as Levels to adjust the Ha Layer before flattening it, though. Sometimes I've had to stretch it to screaming point to get it above the red, notably in galaxies, but since only the brighter Ha is coming into play the low level noise doesn't matter.

Olly

[Allinthehead]

18 minutes ago, ollypenrice said:

I think there's a case for using Curves as well as Levels to adjust the Ha Layer before flattening it, though.

I might give that a try next time. Is there a particular shape of curve you use for this?

[ollypenrice]

8 minutes ago, Allinthehead said:

I might give that a try next time. Is there a particular shape of curve you use for this?

Yes, though it depends on the target. I usually pin the Ha background on the curve where it is before the stretch so I don't lift it enough to redden the background in the final image. It then tends to be the upper end of the curve I lift. This applies particularly to Ha for galaxies. Sometimes, though, it may be the faint Ha I want to lift so I raise the lower part. 

I've done some weird Curves as well. Trying to follow Fabian Neyer on the Ha-background Double Cluster stunt I gave the bottom end a huge lift and then white clipped everything just above the faintest clouds to take out the stars entirely. The Ha in this form looked utterly horrible but since it was only lightening the background it worked reasonably well.

Not as good as Fabian's though. No surprises there!

Olly

 

 

[Allinthehead]

A bit of experimenting next time so. Thanks for that and plenty of homework for Stub Mandrel?

[Stub Mandrel]

!

[Allinthehead]

That's a massive improvement on the first. Maybe a touch too red now. Which method did you use?

[tooth_dr]

Great to see the improvements. Lovely job. 

[Stub Mandrel]

The tutorial method, but I had to raise the gamma of the Ha layer to get an effect!

When I tried Olly's I did something wrong and couldn't change the blending mode.

I agree it is a bit too red. This is less 'in your face'.

 

 

[Allinthehead]

When you paste the red image over the colour and you've set blend mode to lighten try going to image /adjustments / contrast and raising slightly or as Olly suggested try using curves. Do this directly after changing the blend mode without flattening.

[ollypenrice]

18 minutes ago, Stub Mandrel said:

The tutorial method, but I had to raise the gamma of the Ha layer to get an effect!

When I tried Olly's I did something wrong and couldn't change the blending mode.

I agree it is a bit too red. This is less 'in your face'.

 

 

Don't be afraid. If the first was too much the second is too little. Courage, man! Bring it on. A nice blend of both with more of the first, in my book.

lly

[Stub Mandrel]

1 hour ago, ollypenrice said:

Courage, man! Bring it on.

A hard taskmaster!

A single hit of the soft light/luminance does a nice red, rather than mix the two. But instead I've run a few doses of Noel's increase star colour, which still has a  gentle effect on the background and has pulled more colour into middles of the stars than the saturation boost would.

Not quite APOD standard yet ? but does make me think it may be worth trying an OIII filter - I used to think these were not as effective as Ha with a DSLR, but having read up a bit apparently they work well as you can use both green and blue channels so 3/4 of pixels.

Despite my recent comments on guiding only being a 'nice to have' this would have been impossible without 600s subs supported by PHD2.

[AstroAndy]

22 hours ago, ollypenrice said:

What I do is get the Ha co-registered, select and copy it, then activate the RGB and split the channels. Make the red active and paste the Ha on top of it.  But then it's vital to change the blend mode to lighten.

Olly

Hi...seing this article, a question presented itself...maybe I'm missing something, but when I paste an Ha layer directly on red, since I'm on the channel palette rather than the layers one, how do I get into blending mode (I usually extract red, and paste it on the ha, manipulate it, and save it as a new HaR image, which gets pasted back into the red channel, thus getting a layer and the option to change blending mode).

Andy

[Stub Mandrel]

1 hour ago, AstroAndy said:

Hi...seing this article, a question presented itself...maybe I'm missing something, but when I paste an Ha layer directly on red, since I'm on the channel palette rather than the layers one, how do I get into blending mode (I usually extract red, and paste it on the ha, manipulate it, and save it as a new HaR image, which gets pasted back into the red channel, thus getting a layer and the option to change blending mode).

Andy

That's exactly where I got stuck too.

I wish it had Photopaint's simple 'split channels' which produces three grayscale images that can be recombined just as easily.

[ollypenrice]

2 hours ago, AstroAndy said:

Hi...seing this article, a question presented itself...maybe I'm missing something, but when I paste an Ha layer directly on red, since I'm on the channel palette rather than the layers one, how do I get into blending mode (I usually extract red, and paste it on the ha, manipulate it, and save it as a new HaR image, which gets pasted back into the red channel, thus getting a layer and the option to change blending mode).

Andy

 

17 minutes ago, Stub Mandrel said:

That's exactly where I got stuck too.

I wish it had Photopaint's simple 'split channels' which produces three grayscale images that can be recombined just as easily.

In my PsCS3 I select and copy (Ctrl A ,Ctrl C) the Ha, activate the RGB, go to Split Channels in the Channels drop down menu, activate the red channel and paste (Ctrl V) the Ha onto red. Change the blend mode to lighten, tweak in levels and curves to taste then flatten (Ctrl E). Then I go back toChannels, merge channels, select RGB and put R in R, G in G and B in B. That's it.

Olly

[Adam J]

On 01/09/2018 at 11:02, ollypenrice said:

That's good.

I think it's a shame to add Ha as luminance, though, because it turns things pink and gives blue haloes around hot stars. In Photoshop (and maybe other layers based graphics packages) you can add the Ha to red in blend mode lighten and leave your stars unaffected because, in Ha, they are not brighter than the stars in red. This will also keep the reds redder and less pink.

Olly

That's how I used to do it with my dslr. It's the better method. 

[AstroAndy]

Thanks, Olly, I'll check into that.

 

[Stub Mandrel]

1 hour ago, ollypenrice said:

go to Split Channels in the Channels drop down menu

Yikes, that's well hidden! Spot the tiny 'play' symbol!

Got it now.