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(meteorobs) rotating shutters



In a message dated 96-08-27 12:57:20 EDT, you write:

<< Actually, I think the actual rotation speed of your shutter might be 625
instead of 
 1250 or 2500. 625 RMP gives about 20 breaks per second with a two-blade
shutter 
 which gives reasonable meteor pictures. 1250 rpm already gives a lot of wind
noise 
 (but better meteor pictures) and 2500 rpm sounds incredibly fast. I do not
have a 
 stroboscope at hand here, but if your true speed is 625, I would expect to
see a 
 single (two blade) shutter image with stroboscope speeds of 625 and 1250,
and a 
 double  image (cross) of the shutter when the stroboscope speed is 2500.
 The discrepancy of 100 out of 2500 (4% error) is not unusual for analogue 
 measuring instruments. If your instrument has a digital display something
could be 
 wrong.
 
 Success with photographing,
 
 Marc
  >>
-----
Marc,
Perhaps you are correct...but this leaves me with the problem of accepting
which reading is correct...however, Wayne has mentioned an idea that seems to
be worth while in doing and that is to mark one of the blades.  I will do
this the next time out and see what kind of readings I get.  I will let you
know then....the chopped meteor images I do get are quiet nice and clean
looking. 
George Z.