Nikon D40 Owner's Manual page 56

Long Time-Exposures
Shutter speeds of "bulb" and "--" can be used for long time-exposure photographs of mov-
ing lights, the stars, night scenery, or fireworks. To prevent blurring caused by camera shake,
use a tripod or an optional remote control (
Shutter speed Description
bulb Shutter remains open while the shutter-release button is held down.
Optional remote control required. Select mode M, choose a shutter speed of "bulb, " and
then select delayed remote or quick-response remote mode
--
when the shutter-release button on the remote control is pressed and
thirty minutes or until the button is pressed a second time.
To prevent loss of power before the exposure is complete, use a fully charged battery or an
optional AC adapter. Note that noise may be present in long exposures; before shooting,
choose On for the Noise reduction option in the shooting menu.
44 Reference: P, S, A, and M Modes/Mode M (Manual)
33, 103).
35s, f/25
( 33). Shutter opens
remains open for