How do you achieve focus with a CCD camera since there is no live focus mode?
As Patrick and Joe note, all cameras come with some driver software that displays the current camera view with an option to change the length of exposure. Generally, again as Patrick and Joe note, it boils down to three cases: 1) There is bright star (mag. > 8.0) in the DSO image frame (occurs infrequently) Focus on the bright star with a short exposure time (e.g. 5 - 15 secs). The DSO will not exposure. Turn your focus knob in and out focus taking repeated images. When the bright star is a pinpoint, then you are at focus. Now up your integration time to expose the DSO. 2) There is no bright star in the DSO image frame but there is a faint star (mag. 11 to mag. 9) in the DSO image frame (most frequent case). Use the procedure above, but find _one of the faintest stars_ in the image field. When you are out of focus, the faintest star disappears. When the faintest star is out of focus it is a blurred disk, the star's disk brightness decreases, and the star merges with the background brightness of the image's field. You can see this effect with a telescope or binoculars by rolling the scope in or out of focus and watching what happens to the visibility of the faintest stars in the eyepiece. Now here's where motorized focuser controls come into play, if you are using a short focal length optical tube. Images are less forgiving to being out of focus as compared to visual observing. (The mind's wetware compensates for the blurred image.) Short focal length tubes have a very thin focus play - sometimes measured in less than one millimeter. Your hand cannot turn the focus knob accurately enough to get an ultra precise focus. The gear reduction ratio on a motorized focus controller can turn the number in 10ths of a millimeter and really gets the focus adjustment set exactly. 3) There is no faint star, just the DSO in the image (occurs infrequently). Slew off center until you find a faint star. Use the case no. 2 procedure to focus, then slew back to the target. Hope that additional explanation helps. Clear Skies - Kurt