RE: [ATM] strange (collimation?) problem

["Koehler, Steve" <Steve_Koehler@securecomputing.com>]

I put another star collimation simulation in 

http://www.atmlist.net/contrib/steve_koehler-at-securecomputing-dot-com/starcol/
starcol_all.png

This shows the same miscollimation as my previous simulation, but increases the
defocus amount to +/-10 waves defocus in nine increments.  I also increased the
secondary offset by a factor of three, so the asymmetric shadow starts to become
visible.

Notice how at large amounts of defocus you can start to see that the secondary
shadow is a bit decentered, and that it is decentered in opposite directions on
each side of focus.  This decentering is not the indicator of miscollimation.
Instead, miscollimation is indicated by a brightening one one side of the
defocused star image that stays on the same side as you cross focus.  It looks
like this effect is easier to see closer to focus rather than farther away.

I'm curious to hear if my assessment is accurate, and whether the simulation
portrays what people see at the eyepiece.  Of course, in reality, there will
always been some amount of atmospheric turbulence you must "look through", so
the simulations are for the ideal case.

-- Steve Koehler
   steve_koehler@securecomputing.com

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