How to create RRGB?

[Mark72]

Hello,

I do not have Ha filter. So to enhance RGB I just shoot R channel as Luminance - additionally after normal RGB session. It does respond very well in Ha emission nebula. The question is how to go about with it? Shall I apply the same technique as though it were Ha filter or are there any nuisances? Suggestions in PS or PI are welcome.

Thanks,

Mark

[Spikey]

In PS try applying the additional layer to the R channel in blend mode lighten, opacity 50%.

[Earl]

Harry did a tutorial for adding HA it might be worth looking at

http://www.harrysast...m/Hagalaxy.html

Or if you look at the official PI Tutorial use the R image as the L for the final step of LRGB Combination.

[Mark72]

Thanks guys!

Mark

[Zendrix]

Do u mean that after a normal session you can pick the R channel from the TIFF stacked image and re-combine it again with the RGB final pic in order to enhance the Ha emissions? or do you take subs with only Red channel (if that is possible with a DSLR)? Whats the best way to gather more Ha info with a DSLR?

Cheers,

Rui

[MartinB]

If I understand correctly, you are taking subs in R,B and G and then wanting to create a luminence using just the red channel. That should work very nicely with emission nebs with little colour data in them other than the Ha e.g. the Rosette (I know there's loads of OIII in there but it's swamped by Ha) All you need to do is create an RGB image and process. Then process your R subs to create a grey scale luminence and add as a luminence layer. Do you know how to create a standard LRGB? All you are really using the B and G channels for is to create star colour.

However, if you are wanting to capture emission nebulae containing other colour info such as OIII e.g. M27 or reflection nebulosity e.g. flame neb then you are much better capturing a clear filter luminence channel or, combining your RGB data to create a luminence channel (this is quite challenging to do well!).

A red filter won't capture better Ha detail than a clear filter. You could consider using a UHC filter which is a broad band OIII and Ha filter which might give you some benefit

[Zendrix]

Wow.. that's great precious info... im trying to grasp it all! lol

So... let's see if i am even close... if i understood correctly, for a nebula with little colors other than red (lets say the laguna nebula, m8), i can use the trick of making a luminence channel out of the Red channels of my RAW RGB subs.. all i have to do is go to DSS and re-stack the subs (but only the Red channel of it) and add this resulting TIFF to the overall RGB processed TIFF image in photoshop.. is that it? You mentioned a grey scale luminence... do i have to grey-scale it in, lets say, photoshop, after processed?

Sorry if im dead wrong... im new to this.

Cheers,

Rui

[MartinB]

Wow.. that's great precious info... im trying to grasp it all! lol

So... let's see if i am even close... if i understood correctly, for a nebula with little colors other than red (lets say the laguna nebula, m8), i can use the trick of making a luminence channel out of the Red channels of my RAW RGB subs.. all i have to do is go to DSS and re-stack the subs (but only the Red channel of it) and add this resulting TIFF to the overall RGB processed TIFF image in photoshop.. is that it? You mentioned a grey scale luminence... do i have to grey-scale it in, lets say, photoshop, after processed?

Sorry if im dead wrong... im new to this.

Cheers,

Rui

I was assuming use of a mono chip given that RGB filters were involved. That means that the red subs are already greyscale.

You can use a luminence channel for DLSR and one shot colour subs. You can do this in 2 ways, you can convert your combined sub tiff into greyscale and do a luminence process. Alternatively you can access the luminence channel of any colour photo in photoshop by selecting the LAB mode (the L stands for luminence). This allows you to selectively sharpen just the luminence component of the image.