Sebastien Roy <sebastien@xxxxxxxxxxxxxxxxxxx> wrote:
>I was also wondering... (this might be a stupid question)
>Since stars are quite close to true point light source,
>could we use them to evaluate the resolution of a lense?
>
Hardly a stupid question. Stars are truly a point source. We do not have
enough magnigication power to resolve a star to a shpere. Hubble has done
it, but even at that it was just barely. Stars are an excellent subject for
evaluating a lens. As a bright point source, a star will show any
abberation on a lens very well. That is one of the reasons why may fine
photographic lenses make very poor astrophotography lenses - the design
compromises that must be made for *any* optical system are different.
That said, also realize the many other factors that come into play.
Atmospheric "seeing", the movement of layers of air, have much to do with
image quality. Also, the steadiness of the mount, accuracy of the drive and
so on impact image quality too. Its not only the lens, but the whole
system, that must be understood and optimized for good image evaluation.
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