From: "Dwight K. Elvey" 
To: atm{at}shore.net
Reply-To: "Dwight K. Elvey" 


>From: "Mel Bartels" 
>
>> I understand but explain this then....
>>
>> A defocused star that shows the diagonal shadow in the center of the star
>> image, shows no coma when brought to focus.  All stars that display
>> off-center diagonal shadows display coma when focused that exactly
>> corresponds with the off-center position of the diagonal when defocused.
>
>
>But they *do not* - not for stars on-axis.  Where did you get this idea?
>There is no coma for on-axis star images, no matter the shape of the
>aperture - obstructed, crazy-8, whatever.  Try the moving obstruction
>experiment I suggest and see for yourself.
>
>Mel Bartels

Hi mel
 I think you miss understand. I think he is saying that
that is the effect he sees in his scope, not the effect he expects to see.
Like I said, it is most likely something in his alignment that makes it end
up this way or something wrong with his focuser that just happens to align.
Dwight

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