Re: [APML]: Astrophotography on southern hemisphere

[Chuck Vaughn <aa6g@aa6g.org>]

The Astro-Photography Mailing List
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Michael,

>      In order to get rid of the halo problem, you only have to do two
> things.  First, do not use a refractor for tricolor work.  Both Bill
> Fletcher and I have learned this several years ago.  You will never see a
> tricolor photo taken with a refractor by Bill.  His standards are too high.

I don't find blue halos all that distracting, certainly no more so than
diffraction spikes in Newtonians. I'm aware of James Foster's blue halo 
reduction technique.

> His excellent tricolor work is all done with reflectors and he does not have
> a halo or "color" problem.

I don't know what you mean by "color problem". I hope you don't mean that
his photos are balanced properly. You told me before that no tests were
run to determine approximate exposure times. Adjusting them in Photoshop
until they look like what you think they ought to look like doesn't count.

> Secondly, halos can be seen with over exposure
> resulting in excessive halation.  This is especially evident (red halos)
> when using PPF color film with high quality refractors.

Overexposure? What bright stars are *not* overexposed on an astrophoto?

BTW, I haven't seen any new photos out of S. Cal. this season except for
Martin's. You guys got anything new to share?

Chuck <aa6g@aa6g.org>