Under heavy atmospheric turbulence it becomes impossible to take images of the Moon or planets using large aperture telescopes. But there is a method to minimize the blurring effect of the atmosphere (with the con of losing a bit of resolution). This image shows Posidonius and Theophilus craters with and without masking.

Using an aperture mask, you may convert a 6-inch reflector into a 3-inch pseudo-refractor as showed in the image above. The action of the mask is equivalent to remove the diffraction effects of the presence of the secondary mirror given a better contrast to the image. Besides, the instrument becomes less vulnerable to atmospheric turbulence, so under certain circumstances, the aperture mask may be very useful.

On the other side, diaphragming the aperture may help to reduce the Moon brightness when viewed under low magnification.

by ComputerPhysicsLab on 2009-09-10 14:22:20 [Original Size] - [Next Image] - [Author's gallery]