III) I align my Luminance & my RGB frames :

The last step before the final work. I convert my Luminance image in JPEG. The RGB frame is in TIFF format.

I use MaxIm DL CCD 4 align tool :

I use the Manual 2 Stars for this work, better. MaxIm asks to select 2 stars in each image to align them correctly.

IV) Final step under Photoshop :

For the final step, I use the famous PhotoShop software (sorry for the french version).

The first step is to reduce the noise in the RGB frame. For that, I use a Gaussian Blur of 1.2 pixels :

The second step is to Cut & past the Luminance (HαOIII) image on the RGB frame :

For the final step, I select  "Luminosity" under "Layers" tab with the Opacity at 100% :

The final LRGB image is there.

This method is used for all my LRGB images and gives beautiful results. If you have more questions don't hesitate, contact me.