Mooning Around with Perfesser Friar


The Moon looks huge on the horizon, but it’s not, really.   Regardless of where it is in the sky, it’s about the size of an aspirin tablet held out and arm’s length. (Try it if you don’t believe me).

If you consider the sky being 180 degrees from horizon-to-horizon, the Moon is about half a degree in diameter. This means you could fit 360 Full Moons across the sky, end-to-end.

If you want to compare the apparent size of the planets,  it would take anywhere from about 35-60 Jupiters end-to-end to span the width of a Full Moon.

You know when you see the Moon in the sky during the daytime?   Well, try this trick.   Take a white round object, like a softball, and throw it into the sky, close to the moon.   The shadow on the ball and the moon will be the same.  They’ll appear to have similar “phases”.

By definition, a Moon is full when it’s 180 degrees opposite the sun.  So if you see a big moon rising in east while the sun is still above the horizon, it’s not technically full yet.   They can’t both be completely in the sky at the same time.

The moon causes most of our tides, but not all of them.   The sun contributes about a third.

The moon rises about 49 minutes later each day.  It’s orbital period is about 29.5 days.  If you multiply 29.5 x 49.5 minutes, this gives 1446 minutes, or roughly  24 hours.   Makes sense, when you think of it.  One month later, you’ll see the same type of moon rise at about the same time.  (Of course, this isn’t exact, I’m just approximating here, because the earth moves too.  But you get the idea).

The First Quarter-Moon is defined when the sun and moon are separated by 90 degrees.   Think of a right-angle triangle, with the earth at the square corner, and the Sun and Moon on opposite ends. Here’s another trick you can to do check this:  Next time you see the quarter-moon during daylight, take two sticks (or ski poles, whatever) and point one towards the moon, and one towards the sun.   You’ll see your arms make a nice 90-degree angle.

Okay, let me get this straight (some people still get this wrong).  There is NO SUCH THING as the “Dark Side” of the moon!!   Yes, there is a FAR SIDE of the moon, which we never see.  But it’s certainly not always dark. It receives sunlight at least half the time, just the same as the Near Side does.


Getting back to the Full Moon.   Like I said, it’s always opposite the sun.   So during the summer months, when the sun is high in the sky, the Full Moon will always be low on the Horizon.   Conversely, during the Winter Months, when the sun is low, the Full Moon will always be high overhead.   At least, this is how it works in the Northern Hemisphere.

Use these tricks to approximate the time, if you don’t have a watch:

– A full moon rises at sunset, peaks at midnight, and sets at sunrise.
– The First Quarter-Moon  rises at noon, peaks at sunset, and sets at midnight.

You’d think we’d only be able to see 50% of of the Moon’s surface, if the Far Side is always facing away from us.   But actually, the Moon wobbles slightly when it orbits us, and some of the Far Side likes to play peek-a-boo.   Not much…but enough that over time, we end up seeing 60% of the total Lunar Surface.   This is called Libration.

The Full Moon is upside down in the Southern Hemisphere.  (I knew this, but it still kinda freaked me out when I visited Australia).

The moon forms a very thin crescent when it’s almost directly between us and the Sun.    Under these conditions (I’m sure you’ve noticed this), you can not only see the bright crescent part, but the entire dark part a well. (It’s not completely black, it’s more of a dark brown/grey).   This is due to Earthshine.    Just like the Full Moon brightens up our night time here on Earth, the “Full Earth”  will brighten up the night time on the moon.

We get perfect total solar Eclipses because the Moon is almost exactly the same apparent size as the Sun.  Is this a coincidence?    Well, yes, actually it is.

Eons ago, or eons from now, the Moon’s orbit will change and we’ll no longer get total eclipses.   Even now,  the Moon’s apparent size varies slightly in it’s orbit, and there are times it doesn’t completely block out the sun.  These are called “Annular”, or “Ring” Eclipses.

There are some crackpots who claim there’s a “Conspiracy Theory” and that we’ve never been to the moon.   In 2002, a reporter confronted Buzz Aldrin, the second man to walk on the Lunar Surface.  He called Buzz a “coward” and a “liar”.

Buzz punched him out, and rightfully so, I think.

And he was 72 at the time.

Buzz, that was AWESOME!  😀

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41 Comments on “Mooning Around with Perfesser Friar”

  1. Steph Says:

    Whoa. This was awesome! I didn’t know all this stuff! I have to read it again when I’m less tired, though. I am totally in LOVE with the moon. I’m always aware of it, watching it. I stare at it for long periods of time. (But I don’t howl at it, or go mad when it’s full, honest!) I have yet to set up my telescope so I can see it better…

  2. Friar Says:


    No way? You have a TELESCOPE? (KEWL!!) What kind?

  3. Ian Parker Says:

    That was fun and informative, Friar. I knew a lot of that, but I learned a few new things, too. I’ve always had a fascination with NASA, but that’s only because my grandfather was one of the guys who drove Buzz and company out to the launchpad the day of liftoff. It’s a lucky thing the regular driver called off that day because my grandfather usually just did HVAC work for them. It’s funny how things work out.

  4. Friar Says:


    Man..that’s AWESOME!! Your grandfather drove Buzz to the launchpad! How cool is THAT, to have played a small part in such a historical moment?

  5. Ian Parker Says:

    It is awesome. I don’t keep much memorabilia, but I have kept most of his NASA stuff, and the newspaper from his hometown that ran an article on him when it happened. It’s amazing to me how a guy from Mt. Carmel, PA ( a small coal town) could end up tied to history, at least in a small way. Fun stuff.

    Regarding telescopes, I’ve had one for years, but I think it’s time to upgrade. Mine still works well, but have you SEEN the new models lately? They are so slick.

  6. Friar Says:


    Geez, I bet you your Grandpa’s memorabilia would be worth something on Ebay (NOT that you’d necessarily want to part with it, though!)

    But that’s pretty cool…you’re only one person removed from the guy who drove Buzz Aldrin to the launchpad of the most historical flight of all time…

    I bought a 4-inch Celestron Refractor in 1991. It was $1500 bucks back THEN…

    Today you get way more bang for your buck. Things have gone down in price…and all the bells and whistles. You can even look at live webcam shots of the planets on Youtube!

  7. Evelyn Lim Says:

    What a fun read to learn about the Moon!! Thanks!

  8. Steph Says:

    I have wanted a telescope since I was ten, and finally Colin bought me one for Christmas a couple of years ago. But we were in an apt and I had no where to use it. Here at the house there isn’t a clear view of the sky, either, and it’s too light out! Anyway, it’s a Meade DS-2000 series. I mean, I am supposed to see nebulae with it and very far away stuff. But it’s complicated and I don’t really get the instructions, and it’s not just a point and view one, you know? I have been meaning to try again but with so much stuff going on, I keep forgetting and just keep looking wistfully at the sky.

    I am in awe of space and the photos and stuff. But I don’t understand the language AT ALL.

    Hey, maybe you should start a sky watcher blog – in plain language!

  9. Steph Says:

    Better yet, come visit me and help me set this sucker up!

  10. Friar Says:


    You’re welcome! 🙂

    I was watching the moon last night at sunset. On the spur of the moment, I decided to write about it.


    I wanted a telescope since I was fourteen. It wasn’t till I was twenty seven, that I finally got out of Grad Skule, and earned enough money to buy a decent one.

    Nebulae are hard to see, unless it’s a very dark sky. And even then, they don’t look that impressive to the naked eye (just smudges of silver). The coffee-table book photos you see with all the fancy colors are the result of long time-exposures.

    But planets and the moon, …on the other hand. They’re AWESOME! You can see tons of great stuff in your backyard, right in front of a street light.

    Actually, the two images shown in this post are from my telescope. The first one is a lunar eclipse (I had no equipment, I just manually placed the digital camera over the eyepiece with a tripod. The second one is a sketch I did, from another night. Years ago.

    PS. Star Party at Steph’s house!? Cool…!

  11. Brett Legree Says:

    If you don’t believe in the Dark Side of the Moon, listen to more Pink Floyd.

    Hey, you might link out to those programs I showed you the other day (I would but WP might mark me as spam) – that way folks who don’t have a scope could have a go at it.

    Celestia was one of them, and Stellarium was the other.

  12. Friar Says:


    Dark Side of the Moon: Awesome album. But astronomically inaccurate….! 🙂

    Here are the links, if anyone is interested (I know Allison will be!)

  13. Steph Says:

    I always wondered how you could take pics of what you were seeing through your scope! This is exciting! The instruction manual shows pics of Saturn, rings and all, taken as seen through my scope. I can’t even believe I can see those. I just don’t get why I’m so intimidated by the setup. It’s kind of digital, see. Like I tell it where I am and it can give me a guided tour of the universe, and also take me to Saturn or other things, it’s supposed to be rather beginner friendly, I think….

    Star party, yeah!

  14. Steph Says:

    Those links are awesome!! I installed an online scope once but I couldn’t get it to work…

    There’s a cool pic on Celestia of Jupiter and Europe. WOW! I love this stuff!!

    Sometimes I just can’t fathom us floating on a ball in space, and all these other balls are out there, and stars, and holes, and comets, and neat stuff. I can’t grasp the millions of light years and all that stuff. I can’t wrap my mind around it’s hugeness. I stare at the pictures in my The Universe book (a huge coffee table book) and I get all teary because it’s so overwhelming and utterly incredible.

    I just realized something about myself but I’m not going to spill it here. Just…interesting. And bloody bizarre.

  15. Steph Says:

    Damn. ITS hugeness, not it’s.

  16. Steph Says:

    DAMN! Europa, not Europe. DUH.

  17. Friar Says:


    Astrophotography used to be really nit-picky and complicated. Taking a film camera and sticking it on the eyepiece, and using a tracking motor and keeping the exposure open for minutes (or hours) at time.

    Now with digital cameras and web-cames, it’s much easier. There’s even software that will stack the digital images and pick only the best parts.

    You can stick a web-cam on the eye-piece and film the planets LIVE. I dont’ have one, but you can check these out on Youtube. Just search “Jupiter and Webcam”, etc…

    I find it blows my mind…to be staring at actual WORLDS…millions of miles away, in real-time.

  18. Allison Day Says:

    😀 My dad bought a telescope when I was in 6th or 7th grade, and we still bring it out every now and then. It’s cool to set it up on the driveway and check out the stars and planets. Sorry, I have no idea what type or model it is, though.

    I used to be way into astronomy in middle school. (A precursor to my QM obsession? Quite possibly. 😉 ) My GATE class went to this Science Olympiad with a bunch of other middle school teams, and my partner and I won 1st place in the regional “Reach for the Stars” (astronomy) competition. (Although we were murdered in the state competition – apparently they expected middle school kids to know Calculus. Needless to say, I had never even heard of calculus at that point in time. 😛 ) Tons of fun.

    As always, loving your science posts, Perfessor. 😀

  19. Kelly Says:


    Darn it, I got here too late to make Floyd jokes.

    I can still say that I was afraid your tush would play a part in this post, though.

    (Do they say tush in Canada?)

    Those pictures, wow. I can’t believe regular people can get such shots. Shows how much I know. I’m a lie-down-in-the-grass-and-watch-it-go-by kind of chick.

    & yeah, I thought there was a dark side of the moon. I love watching the sky, but I’ve never known anyone who “knew” anything about it, so it’s sort of an art object to me. Sit and be awed without a lot of ed-u-cay-shon in my way. (Pretty odd for me, actually.)

    I can pick out Betelgeuse on Valentine’s Day, and I know a few constellations by name, & that’s it. So you just taught me tons of stuff. Cool.



  20. Ian Parker Says:

    I’ve used Celestia before and really like it. Is Stellarium any better? Can anyone who has used both recommend on over the other? I would be running it on Mac OS X, so all the better if a Mac user can attest to it. 🙂

  21. Friar Says:


    I was always into astronomy since I can remember. I learned the constellations from a book written by H.A. Rey (the same guy who wrote Curious George). The book is at least 50 years old, but it’s the best I’ve ever seen for learning the constellations.’re lucky to have had access to a telescope as a kid. I used to read and read catalogs and dream about owning one. Like I told Steph ,it wasn’t till I was 27 when I finally got one of my own.

    PS. Maybe it’s GOOD that you didn’t learn calculus in Middle School (That could cause brain damage!) 🙂

    Yes, they do say “tush” here. But it’s not something I hear to often.

    The local dialect around here refers to it as “ARSE”.

    And YES…there is NO dark side of the moon.

    (When it’s a half-moon, like it is tonight, where do you think the OTHER half of the daylight is going? 🙂

    Brett showed me these links just a few days ago. I haven’t had time to fart around with them too much yet.

    Hey Brett! (Mr. Mac Guru!). Can you answer Ian’s question?

  22. Allison Day Says:

    Friar – I was really lucky because my dad has always been into astronomy, so he was the one who got me into it. I always loved picking out the constellations – around the time of that competition, I had probably memorized most of them.

    Yeah, my middle school brain probably would have exploded if someone had tried to teach me calculus then. 😛

  23. Friar's Mom Says:

    Wee Friar,

    I remember the first time we borrowed Rey’s Astronomy book from the library, and that small book was renewed numerous times. We would bring it with us on our camping trips and sit by the fire with the family. We learned how to find the Big Dipper, then other stars and constellations. We stayed up long past your bedtime exploring the night sky. You quickly surpassed my knowledge and interest in astronomy.

    I also remember a camping trip to Prince Edward Island. During one of the National Park Interpretive Programs you, Friar’s Dad, and other campers took an evening walk along the ocean and were introduced to the stars. Wow! No city lights. At age 10 (?), you pointed out other stars and constellations, which the park interpreter was unfamiliar with.

    And to this day you continue to elucidate a captive audience with your knowledge.

    Friar’s Mom

  24. Brett Legree Says:


    I use both on a Mac and I’d say (so far, in my experience) that Celestia is better at zooming around and looking at different objects – the interface is a bit easier – but Stellarium is better at showing you what it “really looks like” from the ground. You can easily pick a point of reference e.g. I live in Eastern Ontario, so I pick Ottawa and it gives a pretty good approximation of what the stars look like from where I live at a given time of day and date.

    I suppose that sounds wishy washy but I recommend having both and then deciding which suits your purposes better.


  25. Friar Says:

    @(Friar’s) Mom

    Hey, Mom. Thanks for dropping by!

    I remember you always taking out astronomy books out of the local library, just for our camping trips.

    And I remember the one in PEI. Except I think I was a bit older..maybe 12 or 13.

    (And I remember the park interpreter didn’t really know her stuff…so it wasn’t too difficult to surpass her! Geez…if you’re going to go out and lecture to 30 people…you better know your material!)


    Thanks Perfesser Mac! 🙂

  26. Friar Says:


    My family was always into teaching us stuff (like astronomy). (See Friar’s Mom’s comment). Except we just didn’t’ have the money for a telescope. We didn’t even get binoculars till I was fifteen! (And when we did, I went nuts!)

  27. Kelly Says:

    “When it’s a half-moon, like it is tonight, where do you think the OTHER half of the daylight is going?”

    I’m embarrassed to say that I never, ever wondered. Quite embarrassed.

    Friar’s Mom,

    My daughter and I take out the astronomy books from the library, too. We stare at the books for a while, then go outside, having forgotten everything we tried to learn, and marvel. Something about the enormity of it, I think. I can never memorize it because I’m so busy being amazed, especially when we’re able to get out of our urban area for a few days.

    The first time I visited my parents when they left the ratrace for Middle-of-Nowhere, I could not *believe* there were so many stars. Who knew? Now every time I visit, I get that same sense of awe. We can see fifty times the stars when we’re up there, at least. It blows me away.

    My parents think I turn into an idiot after dark. “Look, Ma. Look, Dad. Look at the SKY!” “Yes, Kelly. Still there.”

    Luckily, my little person shares my sense of wander, so there are two of us idiots when we’re out at night. 🙂



  28. BrettHead Says:

    Here is my favorite song to sing with my boys when we see the moon together:

    I see the moon and the moon sees me.
    The moon sees someone I’d like to see.
    God bless the moon and God bless me.
    God bless the someone I’d like to see.

    When they get older, I will teach them the art of mooning.

  29. Friar Says:


    What about the storybook “Good Night Moon” ? 🙂

  30. Karen JL Says:

    Gaa! So late to the party on this one. I’ll just throw you a “GEEK” and be on my way…


    (but this one isn’t *that* geeky)

  31. Kelly Says:

    Ohh! I love Good Night Moon! “Good night light, and the red balloon…” *sigh* Makes me wish I had little little ones again, to read it to…

  32. Friar Says:


    Uh-oh. If you think this is marginally Geeky, wait’ll you see my next astronomy post. 😮

    It reminds me of a Simpsons episode….where they had Christopher Walken reading “Goodnight Moon” to a group of little kids. He was using his intense, creepy voice…so of course, all the kids were terrified and crying! 😀

  33. t.sterling Says:

    I’m infatuated with the moon. I struggle to get a glimpse of it like it’s something new that no one has ever seen before. That’s all I’ll say for this post. And that I’ll probably bookmark it. Because I love facts about that lovely thing up there.

  34. Friar Says:


    Wow…you really made the rounds today. (You win the record for most comments in one day). I’ll try to answer them all…but please forgive me if I miss a few.

    Yeah, the moon is awesome. Have you ever looked at in with regular binoculars? You’d be awazed at what you’d see with just those.

  35. t.sterling Says:

    All my years of life and I don’t think I’ve took a gaze with binoculars. I used to have a telescope. I still might. I never used it because it didn’t do much for the sky above me, plus my house is surrounded by trees. If I find it, I’ll use it on the moon. I don’t have interesting or attractive neighbors, and if I did, they have their blinds closed, so I never used it horizontally either.

  36. t.sterling Says:

    And yeah, I can’t read your blog on my work computer and I have Fridays to do whatever the stank I want, so I had some time to kill and some of your posts to catch up on. All my friends were out and I have no money, so why not hang out with the Friar?

  37. Friar Says:


    You can also take your binoculars, and look at Jupiter. You can actually resolve the planet’s disc…it will look like a tiny creamy white sphere. Plus you can see it’s major satelites. Just with 7 x 35 binocs.

    PS. Yeah, I supposed you can’t read me at work. (The Deep Friar is a VERY subversive blog…the I.T. Police are always trying to block it! ) 😉

  38. […] My recent astronomy post reminded me it’s been a while since I looked at the […]

  39. That is a lot of moon facts.

    I love in “Bruce Almighty” when Jim Carrey (as God) pulls the moon closer so it looks super huge for his romantic date.

  40. Friar Says:


    Aww…I never saw that movie. (I’ve been meaning to rent it).

    Though (this is the geek in me talking), if the moon is pulled too close, the tidal forces caused by Earth would cause it to break up! 😀

  41. love quiz Says:

    Very interesting subject, appreciate it for putting up.

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