02/22/2026.
Have you ever wondered why you can see the moon during the day, but you cannot see it rise or set? Here's what is going on.
Rises and Sets.
In this first picture, I'm trying to show what happens with the sun's rays during the day.
The yellow lines show the rays coming from the sun (off-screen at the upper right). The really dark blue area is for the darkness of space. The light blue shows where the atmosphere is. The earth is green. And say "hello" to Hugh standing there on the earth. It's Hugh, not me.
The ray labeled "a" is lined up with his eye. If he looks back along it, he'll being looking right at the sun and get blinded by it.
However, take a look at the ray labeled "c". As light passes through the atmosphere, it can get scattered, by both molecules (like oxygen, nitrogen, and water) and small dust/aerosol particles. Most of the light makes it all the way to the ground (absent clouds), but not all it. The light gets scattered in different directions—"f" shows two different deflections from that ray.
If you look at ray "b", some of it scatters off the atmosphere at "e". What Hugh sees if he looks in that direction is the deflected light. That light has a slighly bluish tint to it because blue light has a greated chance to be scattered than redder light. [Note: despite the picture, that scattered light is NOT orange—that's just how I am making it stand out in the picture.]
What I'm trying to show with "d" is that every ray of light that comes in can (and does) scatter ("h") some slightly bluish light into Hugh's eyes. It is slightly blue no matter where he looks. And that is why the sky appears blue. [Ray "g" just reminds us that most of the scattered light does not go into Hugh's eyes.]
Now let's add the moon to the mix. Here the moon is pretty high in the sky.
Here ray "i" gets intercepted by the moon and gets reflected towards the earth ("j") right into Hugh's eyes. Just like the sun's rays, the moon's rays can get scattered (and thereby diminished). That is what "k" is depicting. The ray j" is nowhere nearly as bright as the sun's rays (about 1/400,000). However, it is still brigher than the glow of the sky coming from all the scattered rays from the sun. What matters is the contrast. Thus, Hugh can see the moon, even during the day.
But here is the situation when the moon is rising, or setting. The moon is right along the horizon.
Ray "l" bounces off the moon as before, but now the reflection, "m", has a lot more atmosphere to pass through before it makes it to Hugh's eyes. And with more atmosphere, more of that ray is scattered away, as shown in the picture (with "n" and others).
One thing that whitens the sky near the horizon is that the bluish scattered light there gets scattered again coming back at you, and that scattering removes some blue, restoring the light more-or-less to its original white. There is another effect related to aerosols (small particles like droplets or pollution) that whitens the sky near the horizon. And, believe it or not, light reflecting off the ground makes a measurable effect of brightness there, particularly if there is snow on the ground. Along a whitened horizon, a white moon just cannot stand out very well. [Note: this is a cover-my-butt paragraph—every simple explanation seems to miss something.]
There is still light from the moon arriving at Hugh's eyes, there's just not enough of it to cut through the brightness and the whiteness of the daytime sky near the horizon. Again, it's a matter of contrast.
It's actually a close call. Once the moon gets about 8° in the sky, the length of atmosphere the light has to go through has lessened enough for the contrasts to even out, and the moon starts to become visible. Here's a picture I took a while ago with the moon 8° above the horizon.
You can see the lack of contrast from both the near-horizon dimness and the whiteness edging up.
Let me add that, when the moon rises or sets, it does so at an angle of about 45°. So, when the moon rises to 8°, it also moves to the side by around 8°, and no longer aligns with any mound making up the Octagon.
Seasonal Rises and Sets.
This is why I have noted that there are two viewing seasons for observing moonrises and moonsets at the Octagon.
The picture above shows my "seasonal clock" for what the moon is doing at boreal (northern) lunistices. The face of the clock is not hours but instead the seasons of the year, and it runs counter-clockwise. You can start at the bottom (summer solstice) and move through the year to fall equinox, winter solstice, and fall equinox. It shows the phase of the moon for each northern lunistice and whether the moon rises during the day or the night.
While this particular "clock" shows the year 2025, this situation is true every single year, within a variation of just a few days. What you should get out of the picture is that, for boreal lunistices, you can view moonrises from after the summer solstice until the winter solstice. From the winter solstice to before the summer solstice, you can view moonsets.
The situation is reversed for austral lunistices, with a corresponding reversal regarding full moons and new moons.
If you wish to view aligned moonrises at the Octagon this time of year (winter solstice to summer solstice), you need to look at legs aligned with the austral lunistice.
A Loophole.
There is a slight loophole in all this: that is when you have a full moon for your lunistice. (That is winter for the boreal and summer for the austral.)
During the full moon at the boreal lunistice, the moon rises just around the time the sun sets (and the moon sets just about the time the sun rises). That means that, depending on exactly how close one is to the solstice). That means that, during the transition from setting sun and rising moon, the sky will be dark enough for the moon to shine through. It also helps that the moon one is looking for is a full moon, not a sliver.
In addition, as the moon is rising the sky is darkening, so even if one misses the exact moonrise, the moon will nonetheless show up before reaching 8°.
The following picture was taken on January 2, 2026, eleven days past the winter solstice.
In this case, there were clouds blocking the moonrise before a brief clearing that made the wait worthwhile. The moon showed up quite strongly against the already darkened sky while only about 6° above the horizon (and, as you can see, no longer aligned with the Octagon by about 6°).