Misconceptions occur because students answer problems with explanations that are not in accordance with scientific concepts and are confident in their choice of answers. Identification of misconceptions is an important first step to uncover understanding of learning. The six-tier test was developed from a four-tier test by adding two questionnaire sources of choice of answers to see how the causes of misconception. This study aims to design and validate misconception diagnostic test instruments on Astronomy material. The research method uses mixed methods with the instruments used namely the six tier Astronomy diagnostic test sheet for aspects of reveal, answer, synchronize, relationship, clear, EYD and corresponding. Appraisers numbered four experts to assess the construct and contents of the test instruments. The validation test uses multi-rater test analysis on MINIFAC and MINISTEP software to be analyzed with Rasch. The results obtained from the six-tier Astronomy diagnostic test validation analysis are the suitability of the items fulfilling the appropriate category. Item validity assessment items obtained that the questions can be accepted in all aspects. The conclusion is that the six tier Astronomy diagnostic test instrument is appropriate for identify misconceptions on Astronomy.