From: "Jack Schmidling" 
To: 
Reply-To: "Jack Schmidling" 


From: "Nils Olof Carlin" 

> > the sight tube, while centered over the diagonal,
> > is not centered in the reflection of the diagonal.  It is offset to
>> the front of the scope.

> As it should be - but relative to the optical axis that is centered in
> the sight tube, it is the reflection of the diagonal that appears
> offset towards the primary....

Isn't this a contradiction?  What did I miss?


> You seem to draw the conclusion that the decentered diagonal shadow in
> the defocused images represents coma, rather than the normal diagonal
> offset. But the main question is of course whether there is coma in
> the *focused* image..........

That is the "bottom line" I referred to.  I can not get rid of
the real coma on one side or the other in real images when trying to focus.

 But as a point of interest, a de-centered diagonal shadow always resolves
itself into a coma when focused so it is a true symptom of the disease, in
spite of what everyone says about having to be very close to focus and at
high power.

js

--- BBBS/NT v4.01 Flag-4