Display Not Corrected for Observer Elevation
| Affects | Status | Importance | Assigned to | Milestone | |
|---|---|---|---|---|---|
| Stellarium |
Opinion
|
Wishlist
|
Unassigned | ||
Bug Description
After some interpretation frustration, I can accept that "apparent" position and "set / rise" times are counterintutive. Technically it appears the these topocententric quantities are based on the Horizontal Plane (i.e. 90° from the zenith), and NOT the Apparent Horizon defined as where sky meets earth. Stellarium follows suit with NASA Horizons and USNO ephemerides.
Although it may not be a bug, I think the Stellarium's display should correctly reflect the sky as viewed from the Observer. It does not for v11.3. For example, at 99km altitude, the "dip" (due a finite spherical Earth) of the Horizon is >9° below horizontal! The dip for an observer on Mt. Everest is ˜ 3° which is significant considering the accuracy of the apparent coordinates. Even here, the observer sees a sunrise considerably earlier than the "official" time. To show this apparent horizon correctly allows one to find these "apparent" values which are more meaningful. Another specific example is exploring the midnight sun visibility on Mt. McKinley. For these kinds of investigations, it would be great to have the Observer's Horizon displayed. Stellarium nicely adjusts key visibilty parameters, but the horizon & sky wrt the landscape does not change at all :(
Within Stellarim it is possible to correct for observer elevation after some calculation and landscape adjustments. I think these corrections (with or without refraction ) should be managed by Stellarium. Corrections I employ are straight forward and could, in the simplest case, utilize the refraction settings if two temperature settings are input: Observer and Horzion.
Bottom Line: I'd like to see the Stellarium correctly display the Horizon (horizontal plane) for any reasonable elevation. (It would be nice to have the elevation include the ISS :) Maybe an optional dashed line to reference the Observers' on an ideal sphere?
If there is something I've missed, I happily await for the answer.
Thank you for any attention to this matter,
Jon Seamans
| Changed in stellarium: | |
| status: | New → Triaged |
| importance: | Undecided → Wishlist |
| gzotti (georg-zotti) wrote | #1 |
| Changed in stellarium: | |
| status: | Triaged → Opinion |
The use of "apparent" is consistent with use in astronomical literature. Likewise, using the mathematical horizon (z=90°). If you configure a landscape, this is always enclosing the observer. If you want to create a landscape for high altitudes, you must configure it for that, we cannot just slip down the landscape because we don't know how far away the visible horizon is.
The atmospheric refraction model implemented is based on regular observing sites, and may not not be accurate to predict sunrise on Mt. Everest. The model is not applicable for below about 0 degrees, and is therefore likewise unsuitable for stratospheric balloon observers.
Recent development (0.13 series) would allow querying the landscape and may help developing a "sunrise over landscape horizon" prediction in the future.