Wednesday, February 23, 2011

Tracking the Light

Having decided to get married on a Friday at the top of the city, and being two people who are completely mesmerized by the city lights, Mr. NM and I didn't even have to consult with one another about what time of day to have our ceremony.  We knew it would be an evening ceremony, after work and after sunset.  We were even more sure about this when we visited our site last November to take some pictures of the space after dark.  On that night, it was jet black outside - a completely cloudless and fogless evening, and there was the most incredible full moon visible through the windows of our ceremony space.  I'm sorry to say that I don't have photographic documentation of that, so you'll just have to believe me that it was gorgeous. 

In order to be absolutely certain about the lighting conditions on our wedding day, I consulted to get the lowdown on sundown for November 11, 2011 in San Francisco. 

At this point you may be thinking what I was thinking: "What's the difference between astronomical, nautical, and civil twilight, what do they have to do with sunset, and how do they impact my wedding?"  Well folks, I'm here to answer that question for you in as brief and painless a way as possible.  And I promise that, if you're having an evening wedding or an early morning, you do care about this information..

(Note: I am summarizing this from several sources, but primarily here.  I am in no way an expert on this issue, so please feel free to correct me if I'm wrong.)

Astronomical Twilight:  The beginning and end of light during the day.  Faint stars, galaxies, and other objects begin to disappear as this phase starts and they reappear as this phase ends.  The end of astronomical twilight would be prime city lights-viewing conditions.   

Nautical Twilight:  The middle of the full sunrise/sunset process.  Bright objects are visible in the sky, as is the horizon.  It is too dark to do activities outside without extra lighting, but some light remains.  Not the ideal light-gazing opportunity, but not impossible. 

Civil Twilight:  During this phase the sky is illuminated and you will not need additional lighting for outdoor activities.  In the evening, only bright lights will be visible.  Good enough to see a full moon, but not good enough to take advantage of all the city lights.

Sunrise:  When the upper part of the sun becomes visible. 

Sunset:  When the sun disappears below the horizon. 

As all of us already know, light becomes visible before the sun has actually risen above the horizon line in the morning, and light remains visible after the sun falls below the horizon in the evening.  Thus it's not that helpful to look only at sunrise and sunset times if you're interested in gauging the amount of light you'll see in the early morning or late evening. 

And now comes the part where I super excitedly tell you the good news about our wedding day.  If you consult the chart above you'll see that on 11.11.11 astronomical twilight ends at 6:32 p.m.  Purely by chance, we slated our wedding ceremony to begin at...  6:30 p.m.!  Yay for prime nighttime darkness!  Crazily enough though, if you take a closer look at that chart, you'll also see that daylight savings time ends A MERE 5 DAYS before our wedding date.  So if we had picked a date only a week earlier, then a half hour ceremony beginning at 6:30 would've meant that it would just be getting dusky outside (end of civil twilight, going into nautical twilight) and we would have completely missed out on that city lights look we love so much. 

Clearly the stars were aligned for us (astronomical pun intended).  Oh, you don't believe me?  You want proof?  I'll give you proof.

November 11, 2011...  Full. Freakin'. Moon.  

Proof - Bam!  There you have it.  We SO have the awesomest wedding date and time ever, there's no denying it.

How have the stars aligned for you and your significant other?  And do you have a need to track the light for your wedding day?

1 comment:

  1. Hi! Looks like a nice blog you have. Congratulations on the impending hitching. I wandered in here while researching the various flavors of twilight for the purpose of evening sailing, and since you invited "correction", I just wanted to further illuminate (heh heh) that it's my new understanding that astronomical twilight is relatively meaningless in big cities. That is, you can't really see any increasing degree of darkness once nautical twilight ends, because light pollution has more of an effect on brightening the sky than astronomical twilight does. (Although, I have not actually tested this myself. Yet.) Not that this has any bearing upon the perfection of your timing, but just because you seem like a detail-oriented person.


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