Hi Debbie: Get a piece of black posterboard. Using a compass, draw a circle the same diameter as the aperture of the scope you want the mask for. Now inscribe inside the circle a hexagon that has it's tips touching the circle. In other words the hexagon fits entirely within the circle. Cut out the hexagon with a metal straight-edge and an X-acto knife or similar. Leave about 2" or 3" of posterboard around the hole after you're done, the outer perimeter doesn't have to be precisely cut. Now make a ring of posterboard that goes around the outside of the tube or dewcap, about 2 inches wide. A loose, sliding fit is fine. Holding the mask ceneterd on the front of the scope, slide the ring up against the back of the mask and tape the two together. Use tape every few inches around the entire circumference so the two won't come apart. You will now noitce six diffraction spikes around bright objects. These spikes are draining energy from the central spot and spreading it out away radially. Because they "channel" the energy, there are now dark areas closer to the central spot, that were swamped with light before using the mask. This is the principal that sometimes allows dim, close secondaries to be detected visually. Does this help? C. --- Debbie <utahdeb@aol.com> wrote:

Chuck,

How do you make an apodizing mask?

Debbie

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