Second go with LRGB

[Tim star]

So after my first attempt with the new Atik 460 producing a rather blue M27 which I posted last week I got a go at M51. SW 80ED on HEQ5 Pro with Celestron manual FW and Baader LRGB filters. TRF 2008 reducer. Temp -15C. Luminance 10x300s, binned 1x1, LRGB 5x 120s binned 2x2. 10 darks (300 s) and 10 flats (electroluminescent panel). Guided with Orion MM autoguider. Had to use foil to keep light out of the filter wheel - v bright LED on the Orion MM. Astroart and PS. Confess omitted refocussing and taking flats with each filter, also no flat darks (presume these are darks with the same exposure time as the flats). Will get more detail with longer exposure times I guess. Have a problem with Astroart - get "different size image" on LRGB synthesis. Think Ive sorted it but not sure. Autoalignment works well though. Any comments?

[StargeezerTim]

I use a DSLR and know nothing about CCD's and mono imaging, so can't really help with any suggestions... I like the roundness of the stars, I am having trouble with that at the moment. I find the image a little 'harsh', too much black and white and not enough shade and depth or detail. It almost looks a bit over sharpened and 'posterised', though I am sure that terminology is wrong. 

I also know that sometimes when i post images, they can look very different online as opposed to my own PC!

DSLR imaging is difficult enough, hats off to you for going down the ccd route. Tim.

[poogle]

Nice second attempt. As Tim suggests the processing is a bit to rough, I think you might have clipped both the black- and the white point in the image.

You should never touch the white point in the histogram when doing layers. Have a look here: http://www.sgastrophotography.com/Sgastrophotography/Levels.html

I think that there is a great deal of data in your image that is just waiting to be revealed. Hope this helps

/Patrik

[Tim star]

Thanks guys. I think I have my head around the hardware, now for the processing!

[Astrosurf]

Nice second attempt. As Tim suggests the processing is a bit to rough, I think you might have clipped both the black- and the white point in the image.

You should never touch the white point in the histogram when doing layers. Have a look here: http://www.sgastrophotography.com/Sgastrophotography/Levels.html

I think that there is a great deal of data in your image that is just waiting to be revealed. Hope this helps

/Patrik

This is superb! I've been doing it all wrong!

Great start on your image, Tim. I have a short LRGB tutorial from someone on here. I'll post it up when I get home. I'm new to it all too!

Alexxx

[Astrosurf]

Sorry for the delay. Here's the tutorial. I hope it makes sense!

1. I take an RGB and L into PS separately and stretch/process them before combining. The L, I process for sharpness, contrast, detail. The RGB does not need processing for detail and is best without it since it will add noise. I go for good strong colour saturation because the L will dilute it.

Often the L overwhelms the colour but don't worry.

Paste the L on top of the colour and set the blend mode to Luminosity. Reduce the opacity to maybe 30%.

Slightly increase the saturation in the colour layer.

Put a slight Gaussian Blur into the L layer (say 0.6) and flatten.

Repeat this process until with the L getting progressively higher levels of opacity, until you can apply it at full opacity and on the last application you don't apply the blur, so restoring all the detail.

In stretching RGB, keep an eye on the top left of the histo peak in each colour channel and use the black point to keep this top left aligned in each channel. Also use the colour sampler to check your background sky. Personally I like parity, so about 23/23/23 in each channel but sometimes an image seems to demand something a little different from that.

When stretching and processing your colour I would not process it quite like a DSLR image myself. You don't need detail in your colour layer so don't push for it. Concentrate on low noise and high saturation. The luminance will bring in the detail and dilute the colour.

ALSO

2. Briefly, you can take your stretched RGB and make sure you have left lots of room to the left of the histo peak then go to Image, Mode, Lab colour. In Channels, activate first the 'a' channel, then go to Image, Adjustments, Brightness and Contrast and and increase the contrast by a whacky amount, say 30 to 40 equally and also the 'b' channel

Re-convert the image to Mode RGB after that.

ALSO

3. RGB or LRGB, make two copy layers. Set the top one to Blend Mode Soft Light and flatten it onto the middle layer. Set the blend mode now to colour, add a slight Gaussian blur (say 0.6) and flatten. Repeat if you like.

These are low noise ways to increase saturation.

[Tim star]

Thanks for the really helpful advice, will give it a go!