View Full Version : daytime moon

2001-Nov-06, 06:58 PM
The moon has always held a mild fascination for me. For some time, I have become especially interested in daytime viewing of the moon. I find it really interesting to look up in the sky while the sun is up and see the moon shining back. When I was little I didn't know that was possible.

This morning on the way to work, I had clear blue skies and a bright shiny sun, and a beautiful waxing gibbous moon.


2001-Nov-06, 07:17 PM
I teach high school physics. When I do optics, I always bring in my telescope and try to do it on a day when the moon is visible during class.

One year, I told the students we were going out to look at the moon. One student pips up, "You can't see the moon during the day. The moon only comes out at night."

I had no idea how to respond to this except walk outside with them, point at the moon and say, "Well, there it is. What do you mean you can't see that?"

"But it's not supposed to be there" the amazed student protested.


2001-Nov-06, 07:56 PM
It's really not too big a surprise that most people don't realize the moon is visible during the day.

Let's face it, the time of the lunar cycle when the moon spends significant time above the horizon during daylight is also when it is at its dimmest and smallest ("smallest" in terms of lit crescent, not in terms of distance from the Earth) -- not to mention that that bright blue sky tends to drown it out!

It's not like the daytime moon goes out of its way to draw attention to itself . . .

2001-Nov-06, 07:57 PM
On 2001-11-06 14:17, Hale_Bopp wrote:
"But it's not supposed to be there" the amazed student protested."


Wow. The moon looked quite nice to me too just after sun-up today.

Jupiter was beautifully "close" to the moon last night (05/Nov/01) and this morning while walking from my car to work I took a moment to strain my eyes to see if I could detect it. (Jupiter that is.) Nope, but several people wondered what I was looking at.) However, I do remember seeing Jupiter in the daytime with binoculars. It is just possible to see Jupiter with the naked eye in the daytime if the conditions are just right. (Good eyes, atmosphere clear, sun away from Jupiter, etc...)
It is quite possible to see Venus in the blue sky too, but you have to look in just the right place - namely where it is! If you spot it, try to align it with some terrestrial object from your point of view, (church steeple, telephone pole, tree limb,) so you can show it to a friend.

Planet spotting in the daytime is basically a stunt, but seeing the moon in daylight can be quite inspiring. Sometimes it seems bright or dim depending I guess on where it is in the sky, conditions, and the time of day. If the moon is in the tail end of the receding shadow opposite of the sun after sunrise, it can look quite bright in the blue sky.

As always when working with kids (and adults) in the daytime, safety is a factor if binoculars or telescopes are used. /phpBB/images/smiles/icon_wink.gif

Trivia footnote:
According to Saburo Sakai, Japanese fighter pilots in WWII were required to spot "stars" in the daytime. He probably meant Venus and maybe Jupiter.

Donnie B.
2001-Nov-06, 08:56 PM
This morning on the way to work, I had clear blue skies and a bright shiny sun, and a beautiful waxing gibbous moon.


Pretty, yes!

But waxing, no. Full moon was on 10/31 or 11/1, depending on your time zone. So we're past full, and the moon is waning.

Just picking my nit for the day! /phpBB/images/smiles/icon_biggrin.gif

<font size=-1>[ This Message was edited by: Donnie B. on 2001-11-06 15:58 ]</font>

2001-Nov-06, 09:26 PM
Actually, seeing Jupiter during the day is quite easy when it is about 90 degrees from the Sun (it's farther away now, so this trick won't work).

This is due to the partial polarization of sunlight. Using a polarizing filter, you can block out a lot of the sunlight and increase the contrast between the sky and Jupiter. I have polarized sunglasses and always look for it when I know it is in that region of the sky. The first couple of times, I had a real hard time. I practiced by waiting until the moon was nearby to act as a reference point. Now it is much easier and I can frequenly find it without the moon.

You have to wait a while for it to happen again. Jupiter is heading toward opposition now and you need to wait until we are 90 degrees ahead of it.


2001-Nov-07, 10:47 AM
Looking for a planet during daytime wearing sunglasses.

Why does this sound strange? /phpBB/images/smiles/icon_biggrin.gif

Kaptain K
2001-Nov-07, 10:54 AM
Because it is conter-intuitive??

Bob S.
2001-Nov-07, 03:40 PM
However, I do remember seeing Jupiter in the daytime with binoculars.

Did the same thing with Saturn and a telescope once. eons ago when I was a much more curious lad, the family was packing the car in the pre-dawn hours for an extended road trip. My stuff was packed and I was waiting out by the car, and there was Saturn shining brightly in the pre-dawn purple sky. I quickly pulled out my dad's homemade telescope to check it out. It is of sufficient power to see rings and all. The folks took longer than expected, and by the time they were ready, the sun was peeking just above the distant hills, turning the sky to an early morning blue. It washed out the stars, and Saturn was no longer visible with the naked eye, but there it was clearly with rings and all in the telescope's eye piece. Pretty cool.

2001-Nov-19, 02:49 PM
Drat, here I was trying to show off and then I screwed up. And of course someone here would catch me on it.

Waning, not waxing.

I figured it out after posting and before seeing Donnie B's message.

Note to self: If it's visible in the morning, it is waning. Visible in the evening, it is waxing.

2001-Nov-19, 06:39 PM
A telescope can make the invisible visible, as we know, but it can work in bit different ways.

A few years ago, a friend of mine had set up his telescope with a clock drive in the early evening at an elementary school. Since the night turned out to be cloudy, few people showed up. Still, he'd found Saturn and had set his scope on it. Even after the clouds had completely obscured it, and no stars at all were visible, you could look into the scope and make out the rings of Saturn. Very fascinating.

The Bad Astronomer
2001-Nov-19, 07:06 PM
On 2001-11-07 05:47, Simon wrote:
Looking for a planet during daytime wearing sunglasses.

Well, not quite. Polarizing sunglasses have polarizing filters on them, fo course, but also block out light using a neutral density filter (IIRC). So you don't need sunglasses so much as just polarizing filters. Sunglasses might actually make it harder to spot planets, if they block more light total than just polarized light.