04/23/2014

A year or so ago, a friend called to ask me to step outside and look at the strange color of the full moon. What I and others observed was intuitively strange, but I didn't realize how strange until a few days later when I was puzzling about the experience. What we observed had seemed to be a full moon of a deep orange color setting in the west. The unusual color was the focus of interest at the time. Only when I was recalling the experience did it strike me that the time of observation was a little before 10 P.M. The sun had set around 8 P.M. and it was already dark. A full moon should have been rising in the east, not setting in the west at that hour. My thought is that it must have been an optical anomaly of some sort such that the image was of the sun and not of the moon.

My location is in the Dallas/Ft. Worth area and the season was summertime. Can anyone offer a thought on this matter?

You are correct that the full moon would be rising as the sun sets. Are you sure yuo were\n't turned around - seeing a rising moon in the east as opposed to a setting moon in the west? In Dallas in late June the sun sets at around 8:40PM, so I don't see how you could have seen it at 10PM. If you can give us the exact date this occurred, or at least within a few days, I can figure out whether there was a full moon that night.

Here is a listing of the moonrise and moonset for the month of April 2013 in Dallas Texas (couldn't find one for Ft. Worth.. )There are a few days when it did set around 10:00.
Moonrise, Moonset and Moonphase for U.S.A. – Texas – Dallas – April 2013

Quote:

---

Originally Posted by aliseaodo

Here is a listing of the moonrise and moonset for the month of April 2013 in Dallas Texas (couldn't find one for Ft. Worth.. )There are a few days when it did set around 10:00.
Moonrise, Moonset and Moonphase for U.S.A. – Texas – Dallas – April 2013

---

Sure but the moon was not anywhere near full - it was just one or two days after new moon so would have been a sliver. We need to know the date of this event in order to tell if it was a full moon rising that day.

Thanks to all. I wish that I could help with a date but the best that I can do is summertime. I say that it was a full moon, but that is only because at the time of observation, that is what I felt that I was seeing. Only later did I realize that it was not possible for a full moon to be in that position at that time and as such it must have been an image of the sun but not a direct image because it was already dark outside. I was hoping that someone might have knowledge of some past experience of this sort of thing (similar to gravitational lensing).

Sorry, but the story just doesn't add up. Either (a) you were looking east (not west) at a rising full moon, (b) you were looking west at the setting sun and it was before 8:45 PM, or (c) you were looking west at a moon that was not full.

The absolute latest time for sunset in Dallas is 8:39 PM Central Daylight Time, which happens around the summer solstice June 22. Since Ft Worth is a bit further west its latest sunset time is a bit later: 8:41 PM. Regardless of where you were in the Dallas/Ft. Worth area sunset had to have occurred around that time.

As for other optical phenomena that may come into play - the atmosphere does cause some refraction of light which makes the sun appear to be above the horizon after it has actually set. But the effect is small - about 1/2 degree, or one diameter's worth of the sun's apparent size. In other words if the sun (or moon) appears to be just sitting on the horizon, in reality it is already just below the horizon. Since the sun (and moon) appear to move one diameter in 5 minutes, and given that the angle of the sun (or moon's) track to the horizon is tilted from vertical at an angle equal to your latitude, this means that when the sun (or moon) sets it lingers above the horizon about 5 min / cos(latitude) past when it has actually set. For Dallas this works out to about 6 minutes. So again - if you saw this over an hour after sunset it was not the sun.