Drizzle: To do LRGB or RGB x1 or x2 ????

[kirkster501]

I have been capturing LRGBha all at 1x1.  However, I am starting to do RGB binned 2x2 to get make my camera more sensitive because at 1x1 I do not feel I am getting enough colour.

Regarding drizzle integration, when binning 1x1 I have drizzled all channels at default 2x2.

So I was thinking that with L at 1x1 and RGB at 2x2 binning,  I could still drizzle luminance 1x1 scale in the drizzle config and then drizzle RGB (captured binning 2x2) with x2 in drizzle configuration?

What do you folks think please?

[ollypenrice]

I'll let someone else comment on the dither parameters. However, getting colour out of RGB data can be like getting blood out of a stone. After putting the RGB together, running it through DBE and SCNR green, I look at it and think, Here we go. This is the stone. Lets find the blood!

There are three key tricks in Photoshop but I can't remember whether you're a Ps man or not? If so I'll outline them.

Olly

[kirkster501]

I'm a PI man normally Olly.  But I have Photoshop and have been known to dabble........

[ollypenrice]

Just now, kirkster501 said:

I'm a PI man normally Olly.  But I have Photoshop and have been known to dabble........

OK, so avoid Saturation at first. It's a noise monster. This is on the RGB only, not LRGB.

1) Convert image to Mode LAB colour. In Channels use the basic contrast tool (Image - Adjustments - Brightness and Contrast) to lift the contrast by 35 points first in 'a' channel then in 'b'.  Re-convert the image to RGB mode.

2) Make 2 copy layers. Set top layer to Blend Mode Soft Light. Flatten this onto the middle layer. Set Blend Mode to Colour and add a slight Gaussian Blur (0.6 or so.) Flatten.

Both of these can be saved as one-click actions and both can be repeated.

3) Add luminance to RGB in small iterations, say 20% to start with. With the L on top at 20% in Blend Mode Luminosity increase the saturation on the bottom layer, put a slight blur (0.6 again) on the top L layer, flatten and repeat. On the final iteration don't blur the L and full sharpness will be restored.

Some stars may become super-saturated by this method but that's an easy fix. Copy layer, lower the saturation in the bottom and erase the desired stars from the top layer.

Olly

[vlaiv]

Why do you want to drizzle in the first place?

Drizzle is not going to work as expected on amateur setup. I've written recently about that in another thread on drizzle, let me see if I can find that for you.

Have a look at the thread and things I've written there to get the idea why drizzle won't work with amateur setups.

If that is too long read, just think of it in simple terms - are you undersampling by at least factor of x2?

My guess is that you are either very close to optimum sampling, or you are over sampling as is - this is based on your listed gear in signature. Any way, drizzle is just going to hurt your data and you won't get anything meaningful out of it.

[kirkster501]

Thanks for the replies folks.  Will read into it.

[wimvb]

On 02/04/2019 at 13:11, kirkster501 said:

I'm a PI man normally Olly.  But I have Photoshop and have been known to dabble........

To squeeze blood out of a rock with pixinsight requires the use of Mark Shelleys arcsinh stretch and masked stretch. Barry Wilson has an excellent tutorial:

https://barrywilson.smugmug.com/PixInsight-Tutorials