[Milsurplus] What is this optic item on Craigslist

[Michael A. Bittner]

Over water, we measured drift with respect to a smoke-flare buoy that we tossed out in the old PBM-5.  Mike, W6MAB
  ----- Original Message ----- 
  From: John Vendely 
  To: milsurplus at mailman.qth.net 
  Sent: Saturday, May 04, 2013 9:03 AM
  Subject: Re: [Milsurplus] What is this optic item on Craigslist


  Looks like a driftmeter, or "driftsight", an optical device used for 
  measuring an aircraft's wind drift during over-water navigation.  
  They're usually gyro-stabilized, with a graticule used for measuring the 
  aircraft's ground track angle with respect to waves on the ocean 
  surface, which are an indication of surface wind direction...

  73,

  John K9WT

  On 5/4/2013 11:39 AM, R PRECHTL K7DFW wrote:
  > Claimed to be for aircraft use.
  >
  > What is this?
  >
  >
  > http://portland.craigslist.org/mlt/atq/3763216348.html
  >
  >
  >
  >
  > RP
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