Apparent positions need improvements
| Affects | Status | Importance | Assigned to | Milestone | |
|---|---|---|---|---|---|
| Stellarium |
Fix Released
|
Medium
|
gzotti | ||
Bug Description
An example - Saturn as seen from Bangkok.
1996 Jan 1 00:00 UT
==================
DE406 (J2000) : 23h 24m 33.26s / -06° 07' 16.6"
Stellarium (J2000) : 23h 24m 33.3s / -06° 07' 16.6"
(very close - that's good)
DE406 (apparent) : 23h 24m 20.78s / -06° 08' 35.1"
Stellarium (apparent) : 23h 24m 21s / -06° 08' 36"
(very close - that's good)
But,
1026 Jan 1 00:00 UT
==================
DE406 (J2000) : 00h 59m 32.10s / +03° 44' 57.2"
Stellarium (J2000) : 00h 59m 32.0s / +03° 44' 56.3"
(very close - that's good)
DE406 (apparent) : 00h 09m 40.80s / -01° 36' 41.4"
Stellarium (apparent) : 00h 09m 31s / -01° 35' 21"
(too far apart - needs to fix)
Notes:
1. I choose the dates when Saturn is near equinox because the Declination differences are easily visible.
2. DE406 position from IMCCE - http://
I think the differences may caused by incorrect(?) epoch conversion and it seems the nutation in longitude and obliquity of ecliptic that ignored in Stellarium(?) might be another reason as well.
Related branches
- Alexander Wolf: Approve
- gzotti: Needs Resubmitting
-
Diff: 2869 lines (+1419/-206)28 files modifiedREADME (+5/-1)
data/default_config.ini.cmake (+22/-6)
src/CMakeLists.txt (+19/-0)
src/core/StelCore.cpp (+82/-15)
src/core/StelCore.hpp (+61/-36)
src/core/StelObject.cpp (+39/-19)
src/core/StelObject.hpp (+12/-2)
src/core/StelObserver.cpp (+28/-2)
src/core/VecMath.hpp (+42/-2)
src/core/modules/GridLinesMgr.cpp (+273/-24)
src/core/modules/GridLinesMgr.hpp (+140/-17)
src/core/modules/Landscape.cpp (+6/-0)
src/core/modules/Planet.cpp (+62/-18)
src/core/modules/Planet.hpp (+9/-3)
src/core/modules/SolarSystem.cpp (+4/-0)
src/core/planetsephems/elp82b.h (+1/-1)
src/core/planetsephems/gust86.c (+1/-1)
src/core/planetsephems/gust86.h (+3/-3)
src/core/planetsephems/precession.c (+260/-0)
src/core/planetsephems/precession.h (+59/-0)
src/core/planetsephems/sidereal_time.c (+35/-20)
src/core/planetsephems/vsop87.h (+1/-1)
src/gui/ConfigurationDialog.cpp (+4/-1)
src/gui/LocationDialog.cpp (+1/-1)
src/gui/ViewDialog.cpp (+5/-1)
src/gui/viewDialog.ui (+89/-32)
src/tests/testPrecession.cpp (+121/-0)
src/tests/testPrecession.hpp (+35/-0)
| gzotti (georg-zotti) wrote | #1 |
| Worachate Boonplod (worachateb) wrote | #2 |
| Worachate Boonplod (worachateb) wrote | #3 |
| tags: | added: archaeoastronomy |
| tags: | added: ecliptic |
| Changed in stellarium: | |
| importance: | Undecided → Medium |
| assignee: | nobody → gzotti (georg-zotti) |
| status: | New → In Progress |
| Changed in stellarium: | |
| milestone: | none → 0.14.0 |
| Changed in stellarium: | |
| status: | In Progress → Fix Committed |
| Alexander Wolf (alexwolf) wrote | #4 |
| Changed in stellarium: | |
| status: | Fix Committed → Fix Released |
Thank you for your finding and suggestion where the problem may be. Stellarium uses VSOP87, not DE406. While an arcminute of error does not seem much, it is based on an earlier design decision (speed&download size vs. utmost accuracy). Reports like yours may help to identify weaknesses and improve accuracy over time, and also indicate demand for such improvements.
Depending on the version you tried, the disturbing effect can also be DeltaT which was not implemented at all in versions prior to 0.12 and certainly delivered bad positions centuries before today. This feature is currently being vastly improved!
G.