[Kstars-devel] Eclipse tool

[Daniel Baboiu]

For one thing, I'd have a separate tool for eclipses and occultations,
For one thing, there are selection criteria that significantly reduce
computing time. For example, eclipses occur only in April/October
(currently), so there is no point to calculate a potential eclipse in
August. Of course, the real selection criterion is more complicated than
that. But working through mathematical formula is my kind of fun.

I'm thinking that the tool will display a list of events of the selected
kind, just like the current conjunction tool. The extra information
would be displayed in a separate dialog, once the candidate is
selected. 

There is no closeness parameter for the eclipses and occultations, these
will be automatically set by the algorithm. I'll start with moon
eclipses since the algorithm is much easier, and they are NOT
site-dependent; all that matters is that the moon is above the horizon.
Extra data will be modeled after NASA's lunar eclipses: 
* Outer penumbra contacts
* Outer umbra contacts
* Inner umbra contacts
(these will be displayed in chronological order)
* Ecliptic conjunction
* Time of greatest eclipse
* Phase of umbral eclipse (I don't find much use for the penumbral
parts)

Perhaps the visibility map and eclipse diagram can be added at a later
time, on the same dialog.


On Sat, 2015-02-14 at 03:09 -0600, Akarsh Simha wrote:
> > KStars needs a proper Eclipse/Occultation tool. (yes, I'm offering to
> > implement these)
> >
> > Currently, these events can be predicted to some degree with the
> > Conjunction tool (for solar eclipses and occultations), which also does
> > oppositions (for moon eclipses). However, this is rather crude, and only
> > predicts the moment of smallest separation; sufficient in most cases to
> > predict if an event occurs. For example, on 4 April 2015 at 11:45AM UT
> > there is an opposition between Sun and Moon, with separation of 13'43".
> >
> > But this in not sufficient for more than a qualitative estimation. A
> > long time ago I went through the calculations for Moon eclipses, and got
> > external and internal contacts with umbra and penumbra within 2 minutes
> > of the officially published time in Astronomical Almanacs, even though I
> > only used something like 5 terms for the Sun and 13 for the Moon. Once I
> > got the coordinates, it is something like half a day of work to fully
> > implement the algorithm. but it is not a beginner's job, as it needs
> > some understanding of the phenomena.
> >
> > Since then, I went through the calculation for the Solar eclipses,
> > although I didn't get to the implementation part.
> 
> 
> This sounds like a good idea, but what do you have in mind? How do you
> plan to extend the occultations tool to handle these extra outputs?
> 
> Regards
> Akarsh