equator hours

Now that we’ve gone thru daylight savings time(yay!)
I was wondering:
How many hours of daylight does Ecuador have?
When does the sun rise and set there?

What am I missing? I don’t get it.

Its a simple question…:smiley:

Neglecting the Equation of Time (which is quite negligible) all days at the equator have 12 hrs of sunlight and 12 hrs of darkness. The different lengths of day and night increase as you get farther away from the equator. I hope that answers your question.

Here ya go: http://www.timeanddate.com/worldclock/astronomy.html?n=190

Today, April 7, 2002, in Quito, Ecuador, sunrise is at 6:13 am and sunset is at 6:19 pm. That’s a bit more than 12 hours of sunlight.

This made me curious about something - apparently, the closest place to the Equator which operates DST would be part of Brazil:


It appears that some regions of Brazil at only a few degrees south latitude choose to use DST. Fiji and Tonga also use it. Most equatorial counties do not, which makes sense.

In the other direction, one notes that Iceland does not have DST, nor do a couple of the Baltic states (nor does Antartica, but that doesn’t count).

thank you very much

That’s 12 hours, 6 minutes of sunlight. Notice that six months from now, on October 7th, Quito gets 12 hours, 6 minutes of sunlight (5:59 AM to 6:05 PM). I think it’s safe to say that, roughly speaking, Quito experiences no real change in day duration over the course of the year, getting 12 hours, 6 minutes (more or less) every single day. I believe that the excess of 12 hours is attributable to the reflecting of light in the atmosphere—you see the light from the sun shortly before the sun appears over the horizon, and shortly after it disappears.

Archenar: You’re aware, are you not, that there’s six months between the equinoxes?

Hmm, I’d have thought it was because the Sun is visually a fairly large object - IE, it looks more like a basketball in the sky than a pinpoint. I tend to think that it’s “sunrise” when the leading edge of the Sun’s disk crosses the horizon in the morning, and “Sunset” when its trailing edge crosses the horizon in the evening.

But that’s just my guess.

>> I believe that the excess of 12 hours is attributable to the reflecting of light in the atmosphere—you see the light from the sun shortly before the sun appears over the horizon, and shortly after it disappears.

Achernar (mag. 0.6), refraction at the horizon for standard conditions is about 34’ which represents 2.26 minutes of time. The Sun’s semidiameter is about 15’ which represents one more minute. Total 3.26 minutes twice (dawn , dusk) or about 7 minutes.

If you go by the purely geometric geocentric coordinates of the sun I am sure the period between sunrise and sunset would not vary from 12 h by more than some seconds due to the equation of time .

WillGolfForFood you will find your answer in my previous post. Semidiameter has an effect but about half that of refraction. If we want to get precise we would need to account for parallax because the diameter of the earth is not insignificant compared to the distance to the sun which would shorten the day a bit.

An object infinitely far away would be over the horizon 12 hr but as it gets closer it is below the horizon more of the time. Imagine a satelite orbiting over the equator just a few hundred miles above the earth. You could see it above the horizon much less than half an orbit.

Motny: Yeah, I’m aware that there are six months between equinoxes. If you take two dates six months apart and average their daylight lengths, you should get approximately the average daylight length overall for that place. Think about it.

WillGolfForFood: You’re right that the Sun is not a point in the sky, and that does contribute for about two minutes’ worth of daylight per day, as sailor’s post points out. If you want an idea of how big the Sun is, though, look at the Moon! These two celestial objects are right around the same size as seen from Earth, which is why we get such neato and elusive solar eclipses.

sailor: Yes, Achernar is magnitude 0.6. Are you aware that that’s like the third time you’ve told me something about alpha Eri? :wink: Thanks for supplying numbers to back up my post; very informative, as usual. Looking at the magenta graph at the bottom of the page in your link here, it looks like the steepest slope occurs in December, and it looks to be about 30 sec/day. So, between sunrise and sunset, I would guess that the biggest discrepancy you would ever see is 15 seconds or so.

I’m curious about one thing. Do they really call it the semidiameter? I’ve never heard it called anything but the radius.

Achernar, I am not surprised your name would prompt a comment from me but, to tell the truth, I do not remember the other times. I have a terrible memory. The worst part is when I get into some argument with somebody and soon forget who it was with. Probably the other poster remembers and thinks I’m an idiot when in some other thread I’m acting like I don’t remember anything. At any rate, I expected that (0.6) to go unnoticed by everybody except yourself _ I happened to come across it while I was looking for the other information in the almanac. I am not going to lie and say I knew it by heart.

>> I’m curious about one thing. Do they really call it the semidiameter? I’ve never heard it called anything but the radius.

Well, I’ve never heard it called anything but semidiameter (SD) which just goes to show you astronomers and navigators are different people. I also never understood why astronomers use Right Ascension instead of the Hour Angle of navigators. If you visit any navigation pages you will see it called semidiameter. For example:
The altitude corrections consist of atmospheric refraction (Refr), semidiameter (SD), parallax in altitude (PA),
And some more information of no practical use: this is the formula I developed in my spreadsheet which would give a fairly good approximation of the SD of the sun using the day of the year (d 1 - 365) as argument:
SD = 0.266666666+0.0047COS(0.985645d)
that is in sexagesimal degrees and you can see the range during the year is quite small. The moon on the other hand has a much wider range and the effects of parallax are much greater.

This reminds me quite a few years ago there was an eclipse with the moon being over the Atlantic so it was visible from both sides. I was in DC talking to a friend in Europe and we were both observing the eclipse as we talked. I noticed and explained to her that we were seeing the moon in a different position in the sky due to parallax. The moon is close enough to the earth that people seeing it from different locations on earth will see it in a slightly different place in the sky. (not much, about 1 degree of arc at the most)

**Achernar **, Monty’s brief response was unhelpful, but I think I know what he was trying to get at. In New York on April 7, the sun rose at 5:30 and set on 6:27 - 12 hours and 57 minutes of sunlight. On October 7, it will rise at 6:59 and set at 6:28 - 11 hours and 29 minutes. But to conclude that New York “experiences no real change in day duration over the course of the year” would be ridiculous. You picked two dates very close to the equinoxes, so of course there are around 12 hours of daylight. On the equinoxes, there are 12 hours of daylight everywhere in the world. And the average daylight length everywhere is 12 hours. Think about it.

Oh, give it a rest, chula. & find a dictionary and look up the word Equinox.

I may be missing something but Chula is correct in that:
1- At the equinoxes day/night are 12h each everywhere on earth (neglecting refraction, semidiameter, parallax and other small corrections) and
2- on any place on earth over the course of the year the length of the day averages out to 12h but individual days’ hours of daylight can vary a lot from that, the longest/shortest days being at the slostices.

Monty, your response was rude and did not even attempt to contribute to the discussion on this thread. I might not have a four-digit post count, but in my opinion, this violates the anti-jerk policy. It appears that you did not even read my post and are just randomly lashing out at me. If I made a mistake in my statements, feel free to point that out; otherwise, take it to the Pit.

You know, chula, that’s exactly how I felt about your comment above.

Monty, you realize that chula and Achernar are different people?