<p>Can the eccentricity of a planet's orbit be found just from the analemma of its star? We can draw an analemma given the axial tilt and eccentricity, but how do we find the reverse?<br>
Note: I already know that the highest and lowest points indicate the amount of axial tilt</p>

CC BY-SA 4.0
2019-06-30T08:50:58.427Z
This is a really interesting question! It may be easier if the analemma is really produced as a series of photographs at the same mean solar time each day, then the spacing between each solar position and the next will give some information about the speed of the orbit. For a highly eccentric orbit, you will have a large number of overalpping sun exposures near aphelion, and much wider spacing near perihelion.
uhoh
CC BY-SA 4.0
2019-07-01T16:08:41.650Z
@uhoh how do I process that information into something numerical?
Arnab Chowdhury
CC BY-SA 4.0
2019-07-01T16:09:06.017Z
@barrycarter could you please elaborate your process
Arnab Chowdhury
<coordinate><data-analysis><celestial-mechanics>
Eccentricity from Analemma
Arnab Chowdhury
# Eccentricity from Analemma

(Asked by: username_0 on 2019-06-29)

Can the eccentricity of a planet's orbit be found just from the analemma of its star? We can draw an analemma given the axial tilt and eccentricity, but how do we find the reverse?  
Note: I already know that the highest and lowest points indicate the amount of axial tilt

**Tags:** coordinate, data-analysis, celestial-mechanics
> **Comments:**
> **username_1**: This is a really interesting question! It may be easier if the analemma is really produced as a series of photographs at the same mean solar time each day, then the spacing between each solar position and the next will give some information about the speed of the orbit. For a highly eccentric orbit, you will have a large number of overalpping sun exposures near aphelion, and much wider spacing near perihelion.  
> **username_0**: @uhoh how do I process that information into something numerical?  
> **username_0**: @barrycarter could you please elaborate your process  

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