Video on Winter Solstice sunrise alignment at Izapa

Re: Video on Winter Solstice sunrise alignment at Izapa

Wed, 08 Dec 2010 17:43:43 +0000

In case it might be useful, Aveni talks about this sort of stuff in pp.103ff of Skywatchers. Here's where you can view it on line for free:

http://books.google.com.mx/books?id=JDBu_x6vlZ4C.

He also gives references and appendices with formulas for horizon-based astronomy.

Re: Video on Winter Solstice sunrise alignment at Izapa

Wed, 08 Dec 2010 16:10:53 +0000

Azimuth isn't affected by refraction.
I assume that if the Maya were making an intentional alignment with the solstice sunrise, it would have been with the point at which the Sun actually appears over the hills, even though this may have been several minutes after astronomical sunrise. Maybe I'll have a look at Google Earth and see if I can estimate the azimuth of the ballcourt (if I can find it).

Re: Video on Winter Solstice sunrise alignment at Izapa

Wed, 08 Dec 2010 13:57:43 +0000

But I expect that at dawn on Winter Solstice day, the place will be a zoo.

A zoo filled with some very strange and unusual specimens, I expect.

Re: Video on Winter Solstice sunrise alignment at Izapa

Wed, 08 Dec 2010 13:24:53 +0000

Starry Night sounds awesome. Maybe I'll get it someday. (Like in 2013?)

Thanks for putting real numbers on how much effect the change in the Earth's tilt would have. Jenkins mentions that the tilt has changed since 2100 BCE, but (like Aveni) concludes that to a naked-eye observer, that change wouldn't make much difference. I thought I'd let it go at that, since the point of the video is that Jenkins himself is documenting that there's never been anything "unique" about the Solstice Day sunrise at the Group F ballcourt.

The hills in the background do make a difference. Atmospheric refraction counteracts the effect of hills, but the Sky Charts azimuths I give seem to account for refraction. (I.e., the azimuths calculated by Skycharts varied with atmospheric pressure, and in the right direction.) The bottom line is that the Sunrise azimuths I presented should be correct for a horizon without hills, in a lowland area like Izapa. I considered getting a topo map of Izapa so I could look into the effect of the hills, but as Aveni describes in Skywatchers, it would be a fair amount of work, and I was afraid I'd just lose the viewers in the details.

I still might do it sometime, because it's a problem that might interest students here. And since I live only a day's travel from Izapa, I might even go there someday. But I expect that at dawn on Winter Solstice day, the place will be a zoo.

Re: Video on Winter Solstice sunrise alignment at Izapa

Wed, 08 Dec 2010 04:19:20 +0000

Another interesting video, Jim.
Are there are hills in the distance and do you have any idea how long the first appearance of the Sun might be delayed compared with the theoretical time of sunrise? Presumably the trees which blocked Jenkins' view weren't there originally. I'd be interested to know how his 'triangulation' worked.
Jenkins claims that if the sunrise is aligned today, it was also aligned 2,100 years ago. Not so. Due to the varying tilt of the Earth's axis, the sunrise was 0.3º farther south 2,100 years ago (according to a simulation on my Starry Night program).

Re: Video on Winter Solstice sunrise alignment at Izapa

Wed, 08 Dec 2010 03:25:42 +0000

OOOOPS!!!

The link is fixed now. (Thanks.)

Re: Video on Winter Solstice sunrise alignment at Izapa

Wed, 08 Dec 2010 03:01:34 +0000

The link needs to be connected up.

Video on Winter Solstice sunrise alignment at Izapa

Wed, 08 Dec 2010 02:23:02 +0000

Just in case the Winter Solstice (which is only two weeks away) stirs up some interest in the "Maya" aspect of 2012, I've made a video about observations that John Major Jenkins made at the Izapa archaeological site a week after the 2006 Solstice:

On-Site at Izapa: J. M. Jenkins Demonstrates the Solstice Sunrise Alignment
http://www.youtube.com/watch?v=plyvVeZi0zo

I'll be happy to read any comments.