Stellarium

lp:~georg-zotti/stellarium/gz_fix-ecliptic-obliquity

Created by gzotti on 2015-06-13 and last modified on 2015-07-28

This branch provides the definite fix for a long-standing issue (suspected and reported in 2010!) about wrong ecliptical obliquity and precession of the equinoxes. I implemented a model valid for 200.000 years from now. The resulting version has become much more accurate for applications in historical research or archaeoastronomical simulation.

2015-07-21: It seems to work correctly for earth-based observers.
It demonstrates that VSOP87 is indeed valid only for -4000...+8000: sun runs correctly along the newly displayed ecliptic of date, but only between those dates, and moves towards J2000 ecliptic (i.e. plane Z=0 in VSOP87) within 100 years from those limits, most likely to provide "some" position that is reasonable close.

2015-07-24: Introducing precession circles around the ecliptic poles (of date).

I avoid now drawing ecliptic of date and its grid if we are not located on Earth.

2015-07-27: Corrected planetocentric distance of the observer for ellipsoid planets.

I would like to merge this into trunk at this point before changes become too large. As it is now, there are a few TODOs marked to be fulfilled in the next weeks, and hopefully before creating V0.14. Ongoing work should first fix application sequence of DeltaT, and only then IAU-2000A nutation should be added to get the final arcseconds.

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Merged into lp:stellarium at revision 7748

Alexander Wolf: Approve on 2015-07-28

gzotti: Needs Resubmitting on 2015-07-28

Related bugs

Bug #512086: ecliptic line is for J2000.0, not for current date	High	Fix Released
Bug #1126981: Apparent positions need improvements	Medium	Fix Released
Bug #1240070: Add option to display ecliptic grid of date	Wishlist	Fix Released
Bug #1282558: equinox in Alexandria at 140CE	Medium	Fix Released
Bug #1444323: Pole precession circles	Wishlist	Fix Released

Link a bug report

Related blueprints

Branch information

Owner:: gzotti

Project:: Stellarium

Status:: Merged

Recent revisions

7625. By gzotti on 2015-07-28: added another test
7624. By gzotti on 2015-07-28: First unit test for precession complete.
7623. By gzotti on 2015-07-28: added toString() functions for matrices. Clarified (unused) upper3x3().
7622. By gzotti on 2015-07-28: avoid debug print also in "regular" debug builds.
7621. By gzotti on 2015-07-28: harmonized visible (grid) and displayed ecliptical coordinates for non-earth locations. We cannot compute orbit-related coordinates for other planets yet :-(
7620. By gzotti on 2015-07-28: commented away XYZ and planetocentric observer coordinates
7619. By gzotti on 2015-07-28: added test case files
7618. By gzotti on 2015-07-28: added unit tests (themselves untested, TBD on other platform)
7617. By gzotti on 2015-07-27: ensure getDistanceFromCenter() does not cause problems while observing from SpaceShipObserver
7616. By gzotti on 2015-07-27: show ecliptic obliquity also with non-decimal string

Branch metadata

Branch format:: Branch format 7

Repository format:: Bazaar repository format 2a (needs bzr 1.16 or later)

Stacked on:: lp:stellarium

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