Thanks Peter loo for interesting info, I don't calculate crop factor. I do calculate CCD scale pixel Arc, fov and f ratio exposure to imaging. yes, it is very fast imaging Refractor f/5 and f/3.5. I combined with reducer and it settled at F/3.5, I also took someimages with F/5 without any problem. why I need more lights? I do imaging all are under 45deg alt so you can't get open sky within this limits, usually start at 20+ deg to all the way to 45deg, depends on the object az, some can't go 45deg.
ICX429 is very sensitive ccd and the camera temperature controlled all the time within 1deg C so it can go deeper.