Re: [guide-user] Jupiter and SAO79126

Luc Desamore Apr 19, 2013

Hi Bill,

Thank you for your answer, I understand now the problem.
It could even be the case with the Earth's umbra in Lunar eclipses !

I do not think that it is worth the big trouble to correct this, as we
always can check dubious cases in the sky view.

Luc


----- Original Message -----
From: "Bill Gray" <pluto@...>
To: <guide-user@yahoogroups.com>
Sent: Friday, 19 April, 2013 05:06
Subject: Re: [guide-user] Jupiter and SAO79126


> Hi Luc,
>
> On 04/18/2013 03:43 AM, Luc Desamore wrote:
>> Not a problem just a borderline case : there is a very close
>> approach
>> between Jupiter and SAO79126 on 2013 sept 15 at 04:27 UTC
>> (separation
>> lower than 3 arcseconds).
>>
>> In the sky view at the right position (and with a big zoom) there is
>> no occultation, but the eclipse view shows a small occultation in
>> the
>> polar regions. Actually I think that there is no occultation nowhere
>> on Earth.
>
> Ouch. A problem due to Jupiter not being round. The
> eclipse/occultation
> maps assume spherical objects. The actual sky view _does_ show
> flattened
> objects, mostly noticeable only with Jupiter and Saturn. (Though
> Phobos and
> Deimos and a few others show up as potato-like objects if you zoom in
> far
> enough. Again, occultation charts for those objects will assume
> they're
> spheres.)
>
> I'll look into this. It's been a while since I worked on the
> mathematical
> end of this. (Basically, Guide uses the method of Besselian elements
> to
> compute eclipse/occultation/transit circumstances. The sources I used
> for
> this all were thinking about essentially round objects such as the
> sun,
> moon, Mercury and Venus. I'll probably have to derive some of the
> math
> and see what I get, and may find that it's not really feasible at
> all.)
>
> -- Bill
>
>