Please advise how to set up the Nikon D3100 when shooting the night sky with the Bulb remote control. I kept talking. the inscription "The object is too dark!" and the camera shutter does not open. I need to photograph the movement of the stars in the night sky with the camera shutter open for 30-90 minutes using the remote shutter. I may keep repeating the same error when setting up the camera, but I can't come up with one. Thank you for your help or advice Mirek