Horsetail Falls, Jan 31, 2010
Horsetail Falls attracts hundreds of photographers each year in February, all of whom are drawn by the hope of capturing that elusive, magical glow on the waters. Michael Frye has very good information up on his blog this year on how he now calculates the dates for when the light will be best. I think it’s time to really go in depth on just what happens to make the water glow at sunset at Horsetail Falls.
The following explanation assumes that
A) Water is actually flowing over Horsetail Falls, and…
B) There are no clouds to the west to obscure the light from actually reaching the falls.
Here in the northern hemisphere, the days are lengthening, and have been since the Winter Solstice in December. If you can, imagine a huge circle around you, right on the horizon, with compass degrees around the perimeter. True North is a few degrees away from magnetic north, and 0? is aligned with true North. Going clockwise, there are 360?. The word for each of these degrees on the horizon is “azimuth“.
During the course of the year, the sunset azimuth changes, each day the sun sets on the horizon just a bit more North, or to the viewer’s right. Tonight, the sunset azimuth was 249.4?, tomorrow it will be 249.8?.
Another thing to keep in mind is that the sun doesn’t arc directly overhead; It kinda slides along above the horizon to the south, and then slides down toward the North as it sets. As the year progresses, each day the sun rides higher (or closer to the center) of the sky. It reaches its highest arc on the Summer Solstice in June–and how high it is from the horizon (or how far from the celestial equator) depends on how far north you are on the planet. The words we use to describe the position of the sun in degrees above the horizon or from the celestial equator are “elevation” and “declination“.
The lower the sun is on the horizon, the more atmosphere it has to penetrate. The amount of particulates (read dust and pollution) will color the light. Generally speaking, the later in the day, the warmer the light will be. It takes on gold to red hues.
So, what does all this mean? Well, Horsetail Falls is positioned in such a way that as the sun sets each day in the month of February, it catches the light and turns bright gold or red, depending on where you’re standing when you view it. The best angle is east and south of the falls; The top of Horsetail Falls is by rough guestimate located at Lat/Long 37.7310N by 119.6268W. One of my favorite locations to shoot from is on the east end of the El Capitan Picnic area parking lot, 37.7280N by 119.6193W.
I can hear you guys thinking: “How on earth does she know all this stuff? Is she using a GPS unit?” Nope. I don’t have a GPS unit. Kinda wish I did, it’d make things a bit easier. I used one heck of an application.
The Photographer’s Ephemeris, by Steven Trainor
Go, download it, use it, and love it as much as I do. It’s free. But put a bill or two in his tip jar. He’s earned it.
Part Two will cover the sunset azimuth of some of my favorite shots. Stay tuned, friends and neighbors!
ETA: Disclaimer! I have received no consideration or compensation for endorsing TPE. I am simply a happy end-user of this free application.
Also, it was a bust tonight out at the El Capitan picnic area tonight. Clouds blocked most of the sunlight. On the other hand, it is noted that the roadway and parking lot have been cleared of snow, but the entry gates were closed when I arrived. NPS, if you’re reading this, can we get those gates opened so we don’t have to park on the roadway? And thanks for ploughing. It’s appreciated!
