This should result in a bicycle wheel orbit (a mark placed on the rim of a bicycle wheel will appear to move backwards when it is closest to the ground as the bicycle rolls past the observer) for the Earth around the sun. Viewed from the Sun the Earth would go into retrograde motion once a month. I had hoped to demonstrate this graphically but it appears that the effect is too subtle to appear in my charts.
The radar chart makes it appear that at apogee the orbit is nice and rounded but at perigee the turnaround is instantaneous. This is not the case. The chart should be a nice rounded curve on both ends. It appears sharply pointed at perigee because apogee is closer to the center of the circle where the triangle created by the angle of a day’s movement is smallest. If graphed out lineally the chart should be a smooth sine curve.
Making a linear chart of a portion of the same data only exacerbated the effect and I don't know why. Now both apogee and perigee appear as instantaneous changes in direction of the orbit.
| ? | Over the period of a lunation can I demonstrate a change in the rate of Sun/Earth distance that is repeatable with Moon phase? |
About half way through entering data points into Excel I realized that I was entering the wrong data. I decided to plot three lunations but realize that what I was trying to show would be masked by the change in the speed of the Moon at perihelion and aphelion. When I thought this project up in the middle of the night I had thought of this and decided to start the plot at perihelion and run it to aphelion. My hope was that in the center of the plot, and maybe even at the ends of it, there would be some wavering in the rate of distance change.
The plot that resulted from the first attempt is interesting in that there seems to be a connection between the distance and rage of change. The two graphs for each lunation bottom out about 6 days apart, distance followed by rate of change. The peaks appear to be on a cycle of around 8 days but there is only one lunation that has peaks for both distance and rate of change so I can’t be sure of the average displacement of the two peaks. The left end of the rate of change graphs is strange. The end of the Lunation 1077 chart (light blue) should flow smoothly into the Lunation 1078 chart (salmon) and the Lunation 1078 likewise into Lunation 1079 (light green) but instead the left end of each plot is sharply angled for some reason. The only thing I can figure is that it relates somehow to what time the moon was listed as 0.00 days in Virtual Moon Atlas. I found that once I found this time I could advance the day by 1 to get to 1.00 days and again by one day to 2.00 days all the way through to 29.00 days all without changing the hours, minutes or seconds. But at the end of the lunation it did not increment nicely to 0.00 days of the next lunation. I had to manually back the time setting up to get to 0.00 and I suspect that the funny left end of the line is an artifact of that change.
For my next attempt I looked up the date and time of perihelion in my Observers Handbook 2010 and set Virtual Moon Atlas to the local time equivalent. Then I played with the minutes until I found the lowest distance number and started taking data from there. I just incremented the calendar by 1 day and continued taking data until the distance began to decrease then moved to the next perigee date and started the procedure over again. This plot is a lot better behaved except that the time from perigee to apogee on the third iteration is three days shorter than the others. But any perturbation in the rate of change is hidden by the amount of distance covered by the moon from day to day (up to 7310 km in a day).
| Observing Location | Bryant Park | ||||||||||||||||
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| Observational Period | 1750-1815 EST | ||||||||||||||||
| Atmospheric Conditions |
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| Instruments | Naked-eye - Charlie | ||||||||||||||||
| Observing Party | Charlie Ridgway |
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