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Tony,

As to your question about actually shooting these, it's extremely difficult. Getting accurate high altitude sights is tough.  The big reason is you don't know what direction to face most of the time.  You can literally spin around in a circle and the body never leaves the sexant scope, so you almost have to pre-calculate the azimuth in advance.  If you didn't know your latitude, it can be even harder.  I've accidently shot backsights when attempting these sights.  I find them harder than Lunars to shoot correctly.  It's even worse if you shoot the moon.

Jeremy