E 510 versus film

Look at page 51 of the manual - Shutter release priority. You can set it on or off for both single and continuous focus modes. If you have it on the shutter will not fire while it is trying to AF. Turn it off and you don't have this restriction. To change it - Menu - settings 1 (wrench icon) - Release Priority S or Release Priority C ON/OFF

Easiest way to get into Manual Focus mode - Hit AF button to right of OK button (also functions as right arrow key in other menus) then arrow to MF setting. You can also set via SCP on back (just below metering mode) or via Menu- Camera 2 - AF mode.

For shots of the moon it is best to be in full manual mode.