The Meade 8-inch Equatorial Wedge w/LX90 Adapter Plate will eliminate field-rotation effects when you're using your LX90 telescope for astrophotography. You can do astrophotography with the LX90 scopes in the standard altazimuth mode but for longer exposure times an effect called field rotation becomes evident. Stars at the edge of the field will appear as small concentric arcs or streaks on the film rather than as star points. This effect which does not relate to the accuracy of the telescope's computer or internal alignment occurs on all altazimuth-mounted telescopes. It's simply a side effect of the altazimuth-type mount itself. Preventing Field Rotation To prevent field rotation your LX90 can be polar-aligned by using the wedge. A wedge allows you to align the telescope's axis of rotation with the Earth's rotational axis. This eliminates the effects of field rotation and gets the streaks out.This wedge also can be used with an 8-inch LX200 telescope if purchased with a different adapter plate. An alternative to using a wedge is employing the field de-rotater. The de-rotater allows you to stay in altazimuth mode and correct field rotation for longer-exposure astrophotography and CCD imaging.