Star targets are ideal for identifying focus errors, astigmatism, and other aberrations existing in an imaging system. We have several targets to choose from. Our 60mm diameter (#58-832 and #58-833) targets feature an unresolved core of 100μm, and are ideal for high-resolution or high magnification imaging systems. Both targets are chrome on glass. Our 4” x 4” targets, available as chrome on glass (#46-247) or photo paper (#46-246), feature an unresolved core of 2.7mm, and are designed for mid- to low-range spatial frequencies common in macro imaging systems.