In a message dated 99-03-30 16:37:44 EST, you, Giles, write:
<< A number of users have reported a bit of chromatic aberation such that when
pinpoint light souces such as stars and street lights are photographed they
are surrounded by a purple halo. It would appear that this lens may not be
ideal for astronomy.
On the other hand, a number of people have reported that they are very happy
with
this lens when it is used for more normal terrestial subject matter. >>
A star (without atmospheric distortion) is just as bright as the surface of
the sun, give or take a few millilamberts. So with the star at a high
overexposure level some chromatic aberations may show up because the star is
overexposed but the coma or whatever is not overexposed. But in normal
photography with normal contrast level they would not. While this
astrophotography aberation information gives us some clue as to the sharpness
of a lens, terrestial tests work best for terrestial objects.
Warren
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