Custom Made Equipment
External Rotary Shutter (Chopper)
This device is used to chop a time exposure into regular segments so that relative speed can be compared between exposures, and actual speed can be calculated if a measurement is known for the object/lights being photographed.
Blade: Aluminum sheet metal, 1.5 mm thick, 23.8 cm diameter; each notch 6.6 cm deep and 5.3 cn inside width.
Platform: Aluminum sheet metal, 21.7 cm long by 8.8 cm wide by 5 mm thick.
Electric motor: Canon Seike, Japan. DN35-R13G1B, CN35-06102, 3XGS. Nine volt.
Motor mount: Aluminum "L" bracket cut to 5 cm x 6.9 cm base; 5.8 x 6.9 cm motor-mount side.
Hollow set screws (5/64 key) used to mount motor to bracket and bracket to platform.
Switch: Radio Shack pressure switch mounted in a plastic box with aluminum plate on bottom; velcro mounted to platform (elastic bands for additional support).
Blade revolution: One complete revolution per second (3 chops), to an accuracy of +/- 3% depending on temperature and battery charge.
Ruler is 6 1/4 inches long (16 cm).
Tandem Mount for Two Cameras
Permits both time exposures and wide-angle camcorder video
Two cameras/camcorders can be mounted on the same aluminum base used for the chopper device described above. Set screws secure the cameras in positions determined by pre-drilled holes. Both cameras must be pre-aimed at a distant target at least half a mile away. Only wide angle can be used for the camcorder if zoom 300mm time exposures are taken, because one person cannot operate both cameras simultaneously with accuracy. A cassette tape recorder is positioned between the two cameras as both a backup for audio and for recording local sounds, while a shotgun mic has been installed on the camcorder to obtain target sounds made by the AOP. Works quite well so long as the camcorder is not rocked side to side once set screw tightened (causes plastic base to fracture and break off).
Can One Person Do It All? next.
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Copyright © 2000 Sirius Onion Works.
This page was last edited 01/03/2005