Struve was hardly a good teacher: because of his devotion to research and frequent trips, he missed up to two-thirds of his lectures. Nobody was allowed to take his place and students had to do personal research in his absence. Yet, he kept the highest standards of knowledge at the qualifying exams. On the other hand, his infrequent appearances magnetized many students with his passion to astronomy. During his early years at Yerkes, he developed the practice of looking with one eye into the microscope of a micrograph instrument and with another at the nearby numerical table. This probably resulted in his eyes looking into slightly different directions.