Crescent Venus Setting Trails in the Northern and Southern Hemispheres

October 13, 2023

 

20230724_29金星OK (1)

Photographer: Meiying Lee  
Summary Author: Meiying Lee  

These two images show the difference in the western setting trail of Venus in the northern and southern hemispheres. The one on the left was taken in Taipei, Taiwan at approximately 25.0° north latitude at about 6:00 p.m. (local time) on July 24, 2023, and the one on the right was taken in Sydney, Australia at approximately 34.0° south latitude at about 5:30 p.m. (local time) on July 29.  That's right, I was in Sydney too!

This comparison photo reveals some interesting facts:
1. The difference between the northern and southern hemispheres can be seen from the westward trajectory of Venus, and the latitude of the shooting location can also be judged. Stars fall to the right (north) and down (west) in the northern hemisphere, while stars fall to the left (south) and down (west) in the southern hemisphere. Because of the difference in latitude, the degree of inclination of the two trajectories is also different. Taipei's track is steeper than Sydney's, indicating that Taipei's latitude is comparatively lower.
2. Venus was only about 10% illuminated in late July, so the phase is crescent shaped. Therefore, the position of the Sun in the sky can be determined from the direction of the crescent – it’s lower right in the northern hemisphere, indicating that the Sun is northwest of Venus. In the southern hemisphere, the Sun is to the southwest of Venus.
3. The color of the sky in the two photos also has an important meaning. It’s summer in the northern hemisphere, and the shooting time is 6:00 pm, which is about 40 minutes before sunset in Taipei, so the sky is still very bright blue. However, it’s winter in the southern hemisphere, and the shooting time is 5:30 p.m., 20 minutes after sunset in Sydney. Thus, the sky here is already a slightly darker orange.

 

Taipei, Taiwan Coordinates: 25.0330, 121.5654

Sydney, Australia Coordinates: -33.8688, 151.2093

Related Links:

The Moon on the Same Day from the Northern and Southern Hemispheres

Meiying’s Website