The Celestron #94223 Polar Axis Finderscope is a battery-free (non-illuminated) polar alignment aid with an 18mm clear aperture made exclusively for Celestron's CG-4 and Omni series German-type equatorial mounts. It doesn't work for the CG-5. This finderscope's patterned reticle allows you to fairly easily obtain exact polar alignment in both northern and southern hemispheres, and threads into the rear of the polar axis of your mount after removing the black ring (with three chrome thumbscrews) from the mount.
Instead of using the 3 exposed chrome screws to align finder/mount, this newer version uses 3 setscrews in its body to accurately align with the scope's rotational axis. The newer screws are recessed a bit, helping to prevent their damage.
You only aligning this finderscope to your mount's axis of rotation once, and it just takes a moment or two and can be done in daylight. After that you leave it installed within the mount.
After being aligned to your mount, in the northern hemisphere you place the mount in such a fashion as to align with the finderscope's patterns representing the Big Dipper, Cassiopeia, and Polaris. A little target circle represents the acceptable range for Polaris' location within the finderscope's view, and after you get that set up you can expect pretty good results from longer exposures.
The technique's much the same for use in the southern hemisphere, except that Octans is used as the guide constellation.
Polar Axis Finderscope