Stunning images. If I can get some shots with my D70 that are a fraction as good I'll be happy! Erwin, do you have any details about your equipment and methods for our perusal?
I notice each sub is 640 seconds..you must have a very dark site to be able to go so long without a sky glow problem..or is there something you do to fight that ?
The sky is pretty dark in Leyburn, skyglow is not an issue.
The reason why I shoot @ 800 ISO for 640 s is that 800 ISO for 10 minutes is a good comprimise between banding and dynamical range, 640 s because my master ampglow and thermal noise map is derived from a master dark that consists of 19 dark frames that have been made @ 800 ISO for 640 s each.
The camera is a modified D70, this means the original filter in front of the CCD has been replaced with a Baader IR+UV cut filter.
Focusing is done with the green focusing indicator in the view finder when aimed at a 3rd magnitude star (last turn has to be counterclockwise), and guiding is done with a Celestron off-axis guider with an unmodified Quickcam VC that sends it's images to the Astrovideo guide program on my laptop. This program sends LX200 commands to a relay box designed by Albert van Duin, which controls the hand controller of my Vixen GP DX mount. For every image I shift the telescope a few arcseconds to prevent hot pixels to overlap each other when stacking them later on.
IRIS:
For every RAW image I synthesize a dark frame by multiplying the master ampglow and thermal noise map with an optimal factor and adding these together. The factor for the master ampglow is the exposure time / average exposure time of the 19 dark frames as mentioned above, the factor for the thermal noise map is determined by averaging 8 opt command values while selecting 8 different parts of the image without oversaturated pixels or bright stars.
Every RAW image is dark frame subtracted with it's own synthesized dark frame, flat fielded and gradient CFW converted.
The CFW converted images are aligned and stacked with the composit command with a sigma of 1.5.
Then I apply a logaritm function and a Saturation of 1.5, convert it to BMP (sadly 8 bits) and apply a curve layer in Paint Shop Pro.
Instruments used are the C9.25 with the f/6.3 focal reducer/corrector ot the Celestron 80 ED @ f/7.5.
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to the forum, and hope to see many more shots like that from you! 
