Thursday, March 17, 2011

calculating optimal date nights

This is what happens when I have a few hours off one evening after several weeks of nonstop staring at a computer screen or notebook and generally stressing myself into premature greying.

Or rather, this is what happens when that coincides with the day of having lunch with my friend Mike, who is the first person in my own generation that I've met who is as enthusiastic, if not more so, about amateur astronomy as I am.

First I go rockclimbing since I haven't had any exercise whatsoever in a week.

Then I splurge on tuk tuk thai takeout for dinner.

And then I spend over an hour calculating the required azimuth of the sun at sunset, and the dates when it falls in that range, to see the sun set over the water from the Eastbay, as it slithers just between the city and Marin county and under the Golden Gate bridge.

Backing up. The graduate student lounge in the Berkeley department of economics (known as the P-room) has an unbelievably gorgeous view from the 6th floor of a building at the top of the hill, looking out over the entire bay. The main upside to spending evening after evening banging my head against problem sets as a first year student was seeing sunset and twilight progressively fill this room. For some reason, I always only saw it set over Marin county and didn't think twice before writing off the possibility of sunset over the water.

(Backing up further: I've somehow only seen sunset over the water four times in 7 years of residence in California. In LA, the coast faces south, and here, the eastbay is hugged inland by Marin and the peninsula. The first time I saw it completely unintentionally while on a motorcycle trip up highway 1, and it so shocked me with how beautiful it was compared to the normal thing, which is already pretty dang great, that I've been somewhat obsessed with the phenomenon ever since. Plus, every time is both beautiful and comes with a ticket to the green flash lottery, which I've yet to win. But it IS real.)

I guess I got too accustomed to the beautiful bay area scenery, because it took until a couple months ago to come back to this question. That was when I was fishing on the Berkeley pier at sunset and lamenting the fact that it sets behind the city. (I'm really unbelievably obtuse sometimes; even then I didn't remember well enough or think about it enough to realize that that means that sometime during the year it must go from the north peninsula to the south with a window of opportunity in between.)

But today at lunch, Mike and I got on the subject of Cassini and Saturn fly-bys, astronomy videography, clear sky prospects, and the upcoming showing of Mercury a full ten degrees above the horizon half an hour after sunset next week. And then onto sunsets. And only then, when Mike told me flat out that it's definitely possible, did I realize I had never figured this out.

An itch like that can't go unscratched, even if it means that you find yourself playing with mathematica at 1:30 in the morning, while studying tables of sunset azimuths by gps coordinates and going absolutely giddy over the scrumptious trove of practical geekiness that is this website.

So to get to the punchline: we just missed it, unfortunately. The south end of the golden gate bridge is at about 250.4 degrees azimuth, and the north end at 254.6. There's also the obstacle of the southern suspension tower at 251.7. The sun itself is right around half a degree wide, which gives you probably one day unobstructed under the southern portion, and 9 or so days under the main body of the bridge. That was from approximately February 4-14. (No, I'm not going to try to be more exact than that... there's all kinds of other factors to take into account, such as elevation above the horizon and atmospheric refraction, but the fact of the matter is that the table of sunset azimuths has three significant digits so that's the limiting bottleneck.) The next run will be from October 27-November 5 (with a gap day or two on the back end from the suspension tower).

BUT, you still have a day or two to catch it from treasure island. If the turnoff from the highway that I'm thinking of is where I think it is on google maps, this is about the ideal time to watch the sunset directly under the bridge from there, which has the added benefit that you're half as far away and on level with the water, so the gap between bridge and horizon is much larger.

That's where I'll be tomorrow at 7:18 pm.

3 comments:

Sam said...

Rock climbing eh? Haven't done that in years!


Would be nice to hear some of your views on world developments on my blog.

litwm said...

Pictures of that would be nice

Vera said...

ohh I should've included this video of it, it's beautiful: http://www.facebook.com/video/video.php?v=10150107878613400