Interesting the replies on my sunset discrepancy time. My horizon were not at sea level but I have judged that it was nearly so and could not explain my observation. Because the time that GUIDE tell for the sunset was over while I was able to see the full disk of the sun above the horizon… I didn’t put a horizon in the display; the reason is simply because I assume that GUIDE won’t bother to take in account in calculating the fact that a user put a horizon level in the west direction. Did I my hypothesis correct?

The remark of James Ellis is interesting. At this particular night, after the sunset, my friend and I agree that there was something in the atmosphere and we got the impression that the sky was a little whitish. During the civil twilight, we can observe a tin moon crescent but the dark side of the moon was surprisingly bright. As the dark side is lightening by the reflection of the sunlight from the earth atmosphere, a high content of aerosol within the earth atmosphere seems to increase the lightening of the dark side of the moon. For more info look at the following Web page for more discussion on this topic.

http://www.skypub.com/news/news.shtml#earthshine

Following the idea of James Ellis, if his hypothesis on the effect of aerosol or smog pollution is correct, we can theoretically make a relation between the discrepancy of theoretical and observed sunset and the aerosol content within the atmosphere.

By the way, does somebody know a Web site where we can grab some information on global content of aerosol within our atmosphere?