Hi All, I enjoy taking long exposure (30 second) astrophotography shots, the problem is that after taking a 30 second exposure the camera (Nikon D7000) seems to freeze for another 30 seconds before showing the image on the screen or allowing me to take the next shot. It has been suggested to me that the camera is automatically taking "dark frames". A I am not sure what dark frames are or how the improve the image. Also can I set the camera not to take dark frames as I want to do a series of 30 second exposures to capture star trails, having a 30 second gap between each image makes this impossible. Thanks in advance for any advise you might offer.