A pleasure Dennis. Rarely do I gain access to data that was simple to process. Usually, I'm wrestling with gradients, blooms and noise which plainly compound ones efforts, but I enjoy the challenge. For the long FL you're running (~1800mm), I'd say you've got the rig tuned. Keep doing what you do with regards to the data acquisition - its on the money. The ST7 delivering (1.07 arcsec/pixel) provides good sampling. I wouldn't bother binning the chip at all - even for RGB data collection. You've got the sensitivity and the chip is small already.
Despite the additional work, mono chip with filters will provide the greatest level of control and is certainly my preference. Once you've been there, its difficult to go back. If anything, I'd invest into a bigger chip. Perhaps an ST10. I'd then consider buying some rental scope time from you.
Sure you can get off the SBIG boat, but there is a lot to be said about simplicity of self guiding on the optical axis...certainly as you go up in FL anyway. If you have problems finding guidestars through a Ha filter, simply bin the guide chip to boost the sensitivity. Guide star selection is over rated. Just takes planning, thats all.
For the benefit of others, the processing flow was as follows (summarised). Luminance passed through two iterations of deconvolution and saved as TIFF ready for PS. RGB was colour combined and saved as TIFF. I don't log stretch any of the data. I prefer total control over data stretching in PS - the only exception to this was the follow; A second RGB colour combine was created and DDP stretched heavily with saturation boosted to 180% - then saved as TIFF. All TIFFs opened in PS. Work on RGB, levels and curves with minor boost in saturation. I carefully watched the histogram while stretch. I did not stretch the data all the way to it full potential. I then worked on the luminance and started to stretch it. The luminance was added as a luminosity blend layered on the RGB previously stretched. The luminance was duplicated so that two luminance layers existed in the layer stack. The duplicated layer was then stretched further. All non-linear stretches (curves) were performed with specific top end adjustments to manage the stellar profiles. The two luminance layers contrast each other providing depth - simply use of opacity alters the integration into the layer stack. An alternative way of providing a contrast boost is to duplicate the luminance - stretch it hard - then use the multiply blend mode. The Luminance washes much of the colour in LRGB blends. You can use many methods to circumvent this by introducing the luminance at only 50% and flattening, to greater a so called super RGB, boost its saturation, then add the luminance again at 100%. So you end up with an LLRGB image. In this instance. I took the RGB DDP stretched TIFF and boosted the saturation, blending in as soft light into the layer stack (at top). Then altered the opacity to bring back a more natural feel and lightening the image (soft light is a darkening function). I performed some minor colour balance tweaks and selective sharpening through other layers, but nothing really out of the norm. Having a look at the image again this morning. I think think the blue cast over the image isn't too attractive. Increasing the blue channel black point or dropping it using colour balance shadows would bring out the vibrant reds of the region while not compromising the subtle star colours. Personal preference anyway. There is no end of ways to process LRGB images. What is important is to keep an eye on what you are doing with curves. As you boost the luminance, you need to counteract with colour saturation. You'll find if you stretch the luminance to its full potential, you'll struggle to bring back the colour. Work methodically on both luminance and RGB data sets. Finally, don't set your black point too high during the data stretches, just enough to see what you're working with. As you come closed to the end of the routine, then raise it to remove the "whitespace". You'll find that as its raised, the richer the colours will be become (watch out for white clipping). If they become too rich, simply desaturate the image to your liking. In this entire process, make sure you're still having fun. If processing is giving you a headache and stressing you out - take a break - its not worth it.
Thank you all for your kind comments. I appreciate your acknowledgement. I'm sure I'll bring back a few tricks with me from
AIC2008 to share.
Look forward to seeing more of your LRGB efforts with some new found knowledge Dennis.
