Recent content by roufeng

I before saw this data link, but it is too short and too distant. From 1600 to 2010, more than 400 years, there must be many observations, but where are they kept now? If one looks through internet, you nearly cannot find anymore.

I used a different method (non-elliptical model) to calculate the angle S-O-T (Sun-Earth-Mars) from 09/10/2000 to 08/10/2010, which accouts to 3650 position points and time span is 1 day, and make comparison with horizons system to find an average of the deviation is 2.98 degrees and the maximum...

That means that one still may use horizons data (as replacement of real measurement) to work. Is it right? Can you please show me where to find these observations? I through out websites but find nothing.

Thanks a lot. So, how about the precise of the data from Horizons system? But if one wants to calculate the position of Sun and planets, if he does not have starting position data, where/which kind of data may be selected?

Dear all, reading your reply lines makes me understand I have missed so much. Sorry, I know NASA's horizon' data not good. Because somebody once told me that horizon's data is good match with real observation. That means it is equal to real-time observation. So, I always use the data to make...

I used a different model (hierarchical two-body) to simulate the angle of Sun and Mars (S-O-T) from 9/10/2000 to 8/10/2010, time span is 1 day, 3652 position points are totally selected, and make comparison with NASA's horizon system to find an average of the deviation to be 2.98 degrees, and a...

Thanks a lot. Could you please show me anymore about how to undertake such a measurement? I note that sextant can take a scope of at most 144 degrees, so, if S-O-T is too much (larger than 144 degrees), we need to use background stars to make comparison with Sun and planet to obtain this angle...

I see, that means the angle of Sun and planet in NASA horizon system is from deduced but not from direct observation.

NASA's horizon system shows the angle (S-O-T) of Sun and planet from the view of Earth. Could you please tell me how one measure the angle of Sun and Mars when opposition nearly takes place. In other words, if S-O-T approaches 175/176/178 degrees, how does one from the view of Earth measure this...

This discussion has gone far from the topic of this thread. Now, a conclusion is reached that the 687 days for Mars is from the average of a series of observations that last very long time. That means that if we select different observation time length, the average could be different. And then...

This is a different thing. We see, the 687 days for Mars is from an average of a series of observations, and based on 687 days, if one adds enough mathematical skill, along with the information of other bodies (Sun, Earth, and so on), he could predict position for Mars in the future. So, send...

That means different people uses different observations (within different time length) to obtain different orbital period for Mars. So, how do we now accept that the orbital period of Mars is just 687 days. And I even think the real orbital period for Mars is still unknown. Best wishes!

I have the same question on this point. Dear Sir, I collected the documents from NASA's horizon's system to find that the synodic period of the Earth and Mars during past 10 years is very uneven, which is respectively 806 days, 802 days, 777days, and 767days. If one uses fomula...