[gregbradley]

Good points. I have done some planetary imaging with a ToUcam but it was a while ago. But I don't think I imaged at much faster than 10 or 15fps.

The 180mm refractor won't have the light grasp of a C11 but it may work well in less than perfect seeing - not sure. Visually the advantage of a refractor is higher contrast and ability to cut through poorer seeing. But planetary imaging may require aperture more than anything.

The best visual image I have seen of Saturn was through my C11. I got some super seeing once early in the morning at my dark site when Jupiter was rising again (Aug?). Looking through a Tak FS152 and a TMB planetary eyepiece it was very steady and sharp although image scale was a bit small.

It may be the formula is lowest read noise, greatest sensitivity, fastest download time (firewire or USB2.0), largest aperture with sharpish optics and then a site with good seeing. Then add good capture software.

Paul Haese and Damien Peach are using C14's. Paul's is cooled with 3 peltier coolers. RCOS scopes all have fans to get rid of the thermal boundary layer that sits on top of the mirror and affects performance with as little as 1C
temperature difference between the mirror and the air. Mirrors are usually pretty thick so temperature differences are almost always bound to be there to some degree.

Seems like these chips are good:

Kodak KAI0340 200 frames per second 640 x 480 (Point Grey Research Dragonfly Express (about US$400 or so)
Sony ICX424 648 x 488 9.9um pixels 60 frames per second (Point Grey Research Dragonfly 2 US$795 or so)
Sony ICX285 but its only 15 fps 1384 x 1036 (Point Grey Research Grasshopper US$2595 expensive for planetary)
Sony ICX274AL 1624 x 1224 30 frames per second also ICX445 is a good performer.

Lumenera uses ICX205 1392 x 1040 in SKYnyx 2-1 (only 15 fps though although you can speed it up by using a smaller part of the chip - called region of interest (ROI).
SKYnyx 2-0 is the ICX424 chip and 60fps
SKYnyx 2-2 ICX274 1616 x 1232 but again 15 fps.

So if you have a large aperture scope you'd probably go for the one with the fastest frame rate all things being equal.
If you have poorish seeing your best bet would be large aperture and fastest frame rate with low noise as above.
If you have good seeing and moderate aperture (my situation) then large pixels and moderate frame rate with high sensitivity and low noise may be the go.

That would be the KAI0340 or the ICX424 with 9.9um pixels. Larger pixels usually means lower noise and higher sensitivity. Not sure if the extra megapixels affects the image that greatly as they are usually pretty small images.

What do you think?

Greg.