Another M1 Crab Nebula - How should I add Ha?

[JonTT]

Never posted this separately as I got excited about a nearby asteroid. I have some Ha subs grabbed, but how should I layer them into this image?

[astro mick]

Hi JonTT.

Im no expert,and my images dont get many comments,but one way of adding the H-Alpha is to load the image into Photo-shop,in the channels box make the Red channel the active image.Copy this Red channel to the clipboard,and minimize.

Select File/New from the menu,and create a new window,make sure the size matches your image.Call this new window (H-Alpha.Red).

Paste the copied Red to this new window.

Open your H-Alpha image(If its an old version of Photo-Shop,you may have to covert to 8bits).

Select and copy this to the clipboard.Minimize.

Now paste this H-Alpha channel onto your active H-Alpha.Red window.

Change the opacity to around 25% and Flatten.

Copy this image to the clipboard.

Open your RGB image and select the Red channel.

Now paste your copied image into the red channel.

Now in the channels box make your RGB image active,and you should see a difference.

Basically all you are doing is adding your H-Alpha data to the Red channel of your image,at a reduced opacity.

Hope this helps.

Mick.

[Stephen]

Found this : Telescope Reviews: Ha blend tutorial for DSLRs explained, Rowe techn.

[RobH]

Mick's technique is what I use, although adding a reduced opacity Ha layer to add to your luminance can work quite well on the Crab too....don't go to far with this though as it's easy to wash out the reds.

Cheers

Rob

[RobH]

Forgot to mention....when adding Ha to Red (or anything else), set the blend mode to 'lighten'. Stars tend to be smaller in Ha so if you use it in 'normal' mode then you will throw your star colour off and get some odd effects. In 'lighten', your normal red stars will be unnafected.

[ollypenrice]

I was just going to append the 'Blend mode lighten' bit but Rob's covered it. This is much better than Blend Mode Normal.

I would also try a second iteration at a higher opacity and repeat this to see how it looks.

If I have a very strong red signal in the RGB I find sometimes that the Ha has little effect so while it is pasted over the red I try lifting it in Curves to see what it brings to the red channel. Sometimes I go well beyond the noise limit of the Ha image on its own but you get away with it.

I process Ha images differently for adding to red than for standalone, going for harder contrasts and more sharpeing.

Lastly, with an image like the Crab, it would be easy to paste the Ha RGB onto the RGB and remove the Ha affected field stars altogether, leaving them as prue RGB.

Olly

[Zul]

Looks awesome!

[JonTT]

Thanks everyone! I'll give it a try when I get some free time!