The central obstruction in this system (round aluminum disk attached to the concave Maksutov front lens) is considerably larger (40% of diameter of main optic) than the aluminized spot on the Maksutov corrector lens back. This was probably done to exclude stray light in daylight observation. Increased contrast can be achieved for night time by removing the aluminum disk or reducing its diameter to one more closely matching the aluminized "secondary mirror" on the rear of the corrector lens.