Analog vs Digital - Astronomical Observations


I have been capturing a lot of data regarding the sun lately…
… and a pattern has formed that some of you may find interesting…

In an earlier thread of mine, we observed how the “dayLength” changes dramatically around the Equinoxes, and it slows to a crawl around the Solstices…

To gather this new data, I used the new information found in:
$twcweather.conditions.sunriseTimeLocal and

This allows us to capture the SECOND the sun rises/sets.
(If we use $sunset, it drops down to the nearest minute)
So this new $twc option is much more accurate when talking about sunrise/set times.

The graph below shows (yesterday’s dayLength) minus (today’s dayLength).
(101 days… one dataPoint per day)

It is important to note that, because we are rounding four times to the nearest second…
(yesterday’s sunset - yesterdays sunrise) - (today’s sunset - today’s sunrise)
… then the final results may be up to two seconds off. (which is why the graph is jagged)

From the chart above, I would guess that day 58 (the highest point) was the Equinox… but it actually occurred 4 days earlier on day 54. Perhaps the green “trend” line helps us to see that:

(the arrow points to the Equinox)

If we zoom in, it is a bit easier to see…
Here is 68 days, centered around the Equinox, with each number (on the Y axis) representing one sec:

(Notice the highest point in the trend line is on the Equinox, even though some dataPoints may be higher)

I find it especially interesting that there are SIX days with a bigger change than the Equinox…

For the really observant, the slope of the angle changes gradually before the event, and a bit more aggressive afterwards…

Anyways, even with the analog data, the new $twc times for sunset still surpasses $sunset.

When I used $sunset, my dayLengthPercent would vary up to 0.43% on any given day…
Now, using $twc, it can only vary 0.007%. (or within a half second of each event)


Updated images to show the recent data

Gauge for Length of Day (showing Solstices & Equinoxes)

New image showing 144 days straight…

  • The highest point was the Fall Equinox…
  • The very last dataPoint finally dropped to zero on the Winter Solstice…

I am really looking forward to seeing the entire year graphed out this way.


I predict it will look something like this:


Nine days after the Winter Solstice, and the first indications of a shift in the other direction…


Here is exactly 6 months of data gathering so far…

(Am I the only one that finds this math beautiful?!?)


We are 30 days away from “bottoming out” on the Spring Equinox…

I am curious to see if the negative number will match the positive one precisely…


We are three weeks away from the Spring Equinox…

If my math is correct, then it will reach the lowest point in 21 days.
(shown highlighted at the extreme far right)

In other words, over the next 6 weeks, every dayLightLength will increase about the same number of seconds.

Interesting side note:

As observed here, the next six weeks also has the largest increase in dayLength, on a day-by-day basis.

So while my last two statements may sound contradictory, what I really mean is:
The next six weeks will have the “largest consistent increase in daylight” …
(When comparing today’s dayLength to yesterday’s)

In other words, for the next six weeks, the day light length increases at giant steps, (the biggest of the year)… Each day, with the step being almost the same size as the day before.

Well, technically, the largest steps are the week of the Equinox. They slowly start to shrink after that.

… Man, this stuff is hard to talk about sometimes, LOL

Since incorporating astronomy into my SmartHome,
I’m understanding rhythm & cycles on a “whole… 'nother … level…


I dunno… It is going to be close.

We’re literally one second away from max increase of dayLight, and there’s still 16 days until the Equinox.
(meaning the next 32 days will all have almost identical giant increases in dayLight)

My hunch is the Spring Equinox may surpass the Fall Equinox by a second or two.


When I started tracking this data, I had no idea what range of data would come in. Looking back on almost 8 months of data, it makes more natural sense to make the “up-stroke” of the graph represent when the dayLight durations are accelerating… and the “down-stroke” of the graph to represent when the dayLight durations are decelerating.

So, here is the exact same data inverted.
(I made all positive numbers negative, and visa versa)

I will be using this from this point forward…
(today’s dayLength) minus (yesterday’s dayLength)


Interesting… We just hit the time change, and the DayLength increase reached the maximum amount on the same day…




We are 3.5 days away from the Spring Equinox, and it looks like my math is quite accurate!


Well, the Spring Equinox has arrived, and my math was spot on… To the exact second!

For the next six months, the dayLength increase will slowly drop each day…
(the dayLength will still increase for 3 months, but less dramatically each day)

Months 4-6 will actually be moving in the other direction (with days getting shorter).