ATM Anti reflection coatings and TDE (not related)

["Ashish, Balaya (IE10)" <ABalaya@meghadoot.hiso.honeywell.com>]

Hi everyone,
   I have a couple of things that have been bugging me and I thought I'll
place them before all of you :
1) How do anti-reflection coatings improve light transmission? I know that
they are of a thickness of some multiple of the wavelenght of light so that
destructive interference reduces the amount reflected from the surface, but
for the life of me I can't understand how reducing the reflection can
improve the TRANSMISSION 

2) TDE : How does it degrade the image? By definition, TDE means that part
is slightly convex so light coming in must, after reflection, be diverging
away from the cone that is being reflected (converging to focus). So how can
this diverging part interfere with the converging part and spoil the image.
Of course I know it does spoil the image because doing a star test on my
telescope (I'm hooked. The star test is wonderful and its amazing how well
it works. It showed me I have TDE. Thanks to all who encouraged me to try
the star test) shows me but the explanation eludes me.

Clear skies,
Balaya