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Thursday May 17, 2012
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From the Nasa website: Dec. 8, 2009: Make hot cocoa. Bundle up. Tell your friends. The best meteor shower of 2009 is about to fall over North America on a long, cold December night. “It’s the Geminid meteor shower,” says Bill Cooke of NASA’s Meteoroid Environment Office. “and it will peak on Dec. 13th and 14th under ideal viewing conditions.” To read the rest of this article click on this link. NOVEMBER 24, 2009 Time: 7PM – 9PM BSCS Building PRESENTATION [? To Be Determined]  Apodizing Mask Many people have seen me use a home-built apodizing mask while observing planets and have inquired about its use and design. An apodizing mask (I sometimes call it my “60’s filter”) is used to cut through the seeing much like an aperture stop. Technically, it is supposed to approximate a gaussian curve for the aperture instead of the sharp edge of the normal scope. In a refractor, it basically removes the first diffraction ring of the airy disk at the expense of fattening the central part of the disk somewhat. In an obstructed design like a Newtonian or SCT, there is some debate about it’s value. Also, the larger the secondary’s obstruction, the less it helps. It isn’t very useful in a scope smaller than 8 inches. For my scope (reflector) and my eyes, it seems to help on those less than perfect nights of seeing. Another “side effect” that it makes is a rainbow pattern around the object–hence “60’s filter” (psychedelic man)! The bottom line is that it helps see detail on planets and split double stars. Continue reading A Do-It-Yourself Apodizing Mask |
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