Determining Celestial Coordinates For An Image

A plate solving methodology determines celestial coordinates of an image. Star locations are extracted from the image in terms of pixel coordinates. A group of four stars, referred to as a “test quad”, is identified. A signature for the test quad is generated. In one embodiment, this test signature is derived by determining the separations of the four stars in the test quad, normalized by the largest separation. In one embodiment, the signature also includes the sum of these normalized separations. A query is performed, using the generated signature, against a database of reference signatures for known groups of stars (referred to as “reference quads”). A geometric transform is determined, establishing the relationship between the test quad and a reference quad that matches within a specified tolerance. This geometric transform defines the celestial coordinates of the image. Additional verification steps can be performed to confirm the accuracy of the match.