From kstars-devel  Mon Jun 28 19:25:30 2010
From: Akarsh Simha <akarshsimha () gmail ! com>
Date: Mon, 28 Jun 2010 19:25:30 +0000
To: kstars-devel
Subject: Re: [Kstars-devel] KDE/kdeedu/kstars/kstars/skyobjects
Message-Id: <20100628191330.GJ18611 () PINGU>
X-MARC-Message: https://marc.info/?l=kstars-devel&m=127775245503748

On Mon, Jun 28, 2010 at 07:17:57PM +0200, Alexey Khudyakov wrote:
> SVN commit 1143779 by khudyakov:
> 
> Add functions to calculate refraction corrections to SkyPoint.
> 
> Old code used lookup tables and linear interpolation to calculate
> corrections. Now code just calculate correctionusing formula.
> Optimizations could be added if needed.
> 
> Correctted altitude is continous which means that gap will
> not appear.
> 
> Reverce corrections are calculated by solving equation
> > h' = h + deltaH(h) iteratively
> This is acceptable from performance PoV. unrefract isn't
> called in loops. It's robust since it doesn't depend on details
> of refract implementation
> 
> Also function which returns refracted altitude is added to SkyPoint
> CCMAIL: kstars-devel@kde.org

Wow! This is pretty interesting. Where did you get a continuous
formula? Did you fit a smooth curve to the tables?

There was a rather annoying bug related to the use of lookup tables,
which was related to the behaviour of objectNearest at high zoom with
refract on. I don't recall the details, but it was because unrefract
and refract weren't exact inverses of each other. This should fix the
problem, then!

Regards
Akarsh
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