The Lumicon 12.5mm Orthoscopic Eyepiece with Illuminated Reticle, LG1090 fits the Easy Guider System and provides enhanced focusing assistance.
Over the course of a long exposure, one's telescope alignment with "celestial north" (which is the optical center in the sky about which everything seems to rotate from our point of view) becomes especially critical. When merely observing a sky object, a small variance between your telescope mount's approximation of celestial north and true celestial north matters very little; the object of interest will just veer out of the center of the eyepiece if you're off, and you'll just tweak your telescope to correct it.
But, with astrophotography, you can't see what the camera sees; otherwise, you'd be blocking the exposure. Why? Because when you hit the shutter, the mirror goes "up" and you can't see what the camera is actually recording. Thus, you must be absolutely certain that the objects aren't drifting, and the best way to do that is to observe a small portion of the telescope's field of view(seen by the scope, but not by the camera attached to the scope) and align a reticle with a registration point (i.e. one particular star).
The Lumicon 12.5mm Orthoscopic Eyepiece with Illuminated Reticule can play a large role in precise astrophotography. The more control the viewer has over keeping the telescope properly aligned, the better the chance for crisp, sharp images.