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The Spider / Focuser Assembly
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This view shows the spider and helical focuser assembly. The spiders is attached to the invar cage with 3/8-24 nuts used for squaring the film plane. The helical focuser is the central part of the spider and is built with 2 parts threaded with a 40 thread per inch coupling. The part that turns is marked with 25 graduations giving a reading of .001" distance between marks. 2 dowel pins maintain alignment for picture framing composition. This system works extremely well because unlike the Celestron camera which involves matching focus plus squaring in one complex set of movements. With this you merely square the film plane first not worrying about the focus then use the helical focuser set the focus point first with a telescope pointed in the end and finally with short test exposures scanned and analyzed .The trap door has a 1/4 turn knob for locking the door. |