The major problem of this study was the development of an instrument, the Planetarium Test on Annual Motion (PTAM), that would use an observational format in the planetarium as a reasonable substitute for the real sky to evaluate the attainment of instructional objectives related to selected concepts on the annual motions of the sun, moon, and planets. The instrument was designed to evaluate student performance on 17 objectives, 3 processes of science, and 3 intellectual skills. Thirteen concepts on annual motion were developed. Seventeen behavioral objectives congruent with the concepts were developed and two items written for each objective. The 34-item instrument was field tested with 471 sixth-grade students who received one of three treatments: a planetarium program, a similar classroom program, and no instruction (control). Both the planetarium and classroom treatments produced general gains in achievement more than mastery of concepts. The planetarium was significantly superior to the classroom on many mean and criterion scores for content objectives and, in general, the planetarium instruction fared well on objectives requiring evaluation of observational relationships and higher skills using these observations. (Author/MH)