Meiying Lee wrote: ↑Tue Jun 21, 2022 10:08 pm
In 2021, I spent a whole year in Taipei recording the position of the sun at 7:30 am and 4:30 pm. In the northern hemisphere, the summer solstice of the sun analemma in the morning is at upper left, and the winter solstice at lower right. As for the sun analemma in the afternoon, the tilt direction is different from that in the morning. The summer solstice is at upper right, and the winter solstice at lower left. Whether it is in the morning or in the afternoon, sun analemma has a small circle above and a large circle below. It is also worth noting that the intersection of the figure-8 did not form at vernal equinox or at autumnal equinox. In addition, I recorded four days of sunrise and sunset tracks respectively in spring, summer, autumn and winter, and combined them with sun analemma. The degree of inclination of sunrise or sunset can be used to determine the latitude of the shooting location.
Very nice follow up, and yes! a beautiful capture of the analemmas over Taipei!!
What you describe now makes sense if your wording is as I read it.
The APOD description says the 4 days of sun tracks were the solstices and equinoxes. Your description simply states you took the track images on four days of spring, summer, autumn and winter - not claiming any were taken at the solstices or equinoxes. Is this true?
I'm clarifying because the only aspect that appears off was the APOD claim that the sunset tracks were made on both equinoxes because the sun does not deviate from 0° declination in less than a day. This contradicts the large separation error between both the spring and autumn sun tracks and the tracks end positions. You description, however, does not conflict with the image.
Yes, and equinoxes will not occur at the intersection point in the figure 8, but the space tracks will overlap on the equinoxes. Endpoint sun positions will be separated by ~16 minutes of time, → 15min÷60min x15° = 4°, whereas the separations of the endpoints in your posted image ≈ 6.5°.
I certainly think your description is right, and you were not
attempting to image the sunset tracks on the equinoxes.
Thanks again for a new view of the analemma. The link JohnnyDeep posted above is more instructive with all the annotations, but beauty is in the eye of the beholder right?