What modulates our Sun? The majority of science work on the principle that the Sun is self modulating and each solar cycle is a product of a random number generator. There are others that suspect the Sun is modulated by the planets with a special emphasis on Uranus & Neptune. Thanks to Carl Smith who has recently left us we have new knowledge that significantly adds to Jose, Landscheidt & Charvàtovà's work.

Geoff Sharp

This cannot be right

OK I am trying to write my own solar system simulator. Knowing that Saturn and Jupiter are nearly in opposition (or whatever you call being 180° apart) gives a good test of whether of not my ephemeris calculations are working correctly. But they don't look so good. I end up with J-S angular difference of ~260° for today's date. Jupiter at longitude 348° and Saturn at 92°. I  bang my head against the wall for a few days and then I realize I can use HORIZONS to see what their values of mean anomaly etc are. HORIZONS returns (nearly :) exactly the same values as mine (so all that head banging was for naught). So can someone tell me why the mean (and true) anomalies do not place J-S 180° apart using todays date?

Looking at the values for the two planets I see that the calculated longitudes for both planets on todays date are 180 degress apart, but the Kepler formulae start with mean anomaly = longitude - longitude of perihelion. Is that incorrect. Or am I misunderstanding something?

Lastly, I was using the jpl orbit diagrams as a visual standard and it states at the bottom that the vernal equinox is along the horizontal x-axis to the right, and yet, on Oct 1, 2101 it looks to me like the Earth is darn near right on the vernal equinox. 

Is it just me?

Thanks for any help you can give me with this.



Hello again all, I realize

Hello again all,

I realize now that the vernal equinox occurs when the Sun is in (or appears in the position of) the vernal. So I guess the JPL SSD folks know what they are doing after all Sealed

As for the Kepler Equations, I still cannot understand how they state that that the Mean Anomaly is calculated by subtracting the Longitude of Perihelion from the Longitude.....

Thanks again for any light you may be able to shed on this for me.



Gator, mathematician - one of those MUST be first, oh, and software developer: Smalltalk, Delphi, MUMPS

And to round out my own

And to round out my own thread:

It turns out the triangulations used to calculate the variation reuire that you reference the longitude with repsect to the perhelion. This yield a longitude with respect to the perihelion which must be transformed back to get the longitude with respect to the equinox, i.e. add the perihelion back in.....its all in black and white.

It is interesting to note that the opposition of Jupiter and Saturn has just occurred not ten days ago. Would one consider this an auspicious occasion? A bottoming out so to speak. The reason I wrote the silly simulator, so I cound calculate for myself exactly what day the two of them would be 180° apart. 

The software is available if anyone would like a look. You have to download Squeak, a cool Smalltalk implementation, and then load my code from the Squeak public repository. (or you could paste the following code in a Squeak workspace:

Installer ss project: 'MSQ'; package: 'KeplerEquations'; install.

Then type SolarSystem new view. and Do-It as well). Thats about all I can contribute at the moment. If it complains about Sea-anything just Proceed. I am going to make a web app out of it using Seaside, a Smalltalk web framework.


Gator, mathematician - one of those MUST be first, oh, and software developer: Smalltalk, Delphi, MUMPS

Thanks John, you are way

Thanks John, you are way ahead of me as I wouldnt know where to start when building what you have built.

Your comment about the importance of the Jupiter/Saturn opposition is a form of bottoming out but strictly speaking this only occurs when Uranus and Neptune are also opposing each other when it comes to solar AM.  Uranus and Neptune are together so the bottom out will happen a fair way after the Jupiter/Saturn opposition. But your statement of the opposition is important as that is the peak day for the AM perturbation that causes grand minima.

Many thanks go to Carl's brother Dave for providing the Domain, Server and Software.