Finding and centering an object on a small CCD chip can be a tricky business if you do not have a telescope with a computerised high precision GOTO function like the Meade LX200.  Even with an LX200 it is often desirable to visually check that the GOTO successfully centered the object before taking the image.  What is needed is a device that allows you to look through the telescope while the camera is attached and focused.     A flip mirror finder is just such a device.  The finder is placed in the optical path of the OTA, directly in front of the CCD camera. The front of the finder attaches to either the telescope visual back, focal reducer or telenegative and the camera attaches to the rear of the finder.  The finder contains a small mirror which can be rotated from a horizontal to 45 degree position.  When the mirror is horizontal, light passes over it and into the camera.  When in the 45 degree position, light is reflected up through a standard eyepiece allowing you to see what is centered in the telescope FOV and thus on camera.  Finding and centering objects for the camera is now easy.  Just set the finder mirror to the 45 degree position and place the object in the finder eyepiece FOV using your normal methods (star hopping, finderscope, analogue setting circles, digital setting circles, GOTO etc..).  Now adjust the RA and DEC of the OTA to centre the object in the finder eyepiece, move the mirror to the horizontal position and you are ready to take your image!  I use the True Technology Flip Mirror Finder.