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When given a Sunrise or Sunset time for today, where is the point of reference?
Is Sunrise based upon when sunlight first strikes a certain place in the valley (SL Airport??), or is it where we would first see the sunlight if no mountains were in the way (an "artificial horizon").
Same question would apply for Sunset, and when we would no longer see the sunlight.
Steve V. Riverton
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Sunrise and Sunset times are important to a lot of people, especially those planning events outside or if you're trying to get a photograph.
Actual Sunrise time and Sunset time is defined as the upper edge of the disk of the sun relative to the location of interest. For sunrise that would be the leading edge of the disk and for sunset it would be the trailing edge.
The time of sunrise and sunset may not be exact because of conditions going on in the atmosphere like the bending of light (refraction) at the horizon. Even when conditions might be perfect, there could be an error of a minute either way. Mountains and other topography and the height of the person observing it can also effect the time of the sunrise and set.
Most Sunset and Sunrise calculators just use the Latitude and Longitude of a city. So if you live in Riverton, your coordinates might be a little different than those in Salt Lake hence the sunrise and sunset time might be slightly different. You can calculate the sunrise and set time from the US Naval Observatory website and Riverton does show up.
Sunrise in Salt Lake today was at 6:14 am and sunrise in Riverton was at 6:15 am.
Answered by KSL Meteorologist Dina Freedman
