Re: [APML] The perfect astrophoto book (Was: North American Nebula (or dodging aurora))

[Gene Horr <genehorr@texas.net>]

westergren wrote:

> A subject that hasn't been discussed much is Atmospheric Differential
> Refraction (ADR).  

That's because it generally isn't a issue.  Large (8" or larger)
wide-field instruments are rare plus most people tend to shoot at higher
altitudes above the horizon.

But even still, I for one am curious about your solution to this
problem.  If I understand the effect you are talking about I always
assumed it resulted in stars elongated parallel with the center, 
not perpendicular to it as with field rotation.

> I studied the
> causes of ADR and now have a way to control it.  

Gene Horr
genehorr@texas.net

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