We’re all familiar with the phases of the moon, going from new to full and back again with a period of just under 30 days. What might be a bit less obvious is that you can see the phase change over a single night.
A 360 degree phase change over 30 days is roughly 12 degrees per day. Over a good night’s observing, say about eight hours, that would mean that the sun’s light would cross about 4 degrees of the circumference of the moon. That ought to be visible, and indeed it is.
The following shows two images of the moon. The one on the left was taken at 5pm last night, 19th Jan. The one on the right was taken at 1am this morning, 8 hours later. Ignore the change in colour. The moon was close to the horizon in the right hand picture. It changes colour close to the horizon for exactly the same reason that the sun does: there’s more atmosphere to scatter the light.
Look at the area about a third of the way down from the top, close to where the light meets the dark. There’s a range of mountains running north-east to south-west. These are called the Apennine Mountains. They terminate in the south-west at a crater called Eratosthenes. The crater is clearly visible on the 1am picture, but is just emerging from the shadows in the 5pm one.
Here’s a closeup of the same two photos.The large crater at the bottom is called Clavius. Again, sunrise over Clavius is clearly visible.
I was hoping to catch Jupiter and the moon together earlier in the week but the field of view of my telescope and camera combination was just too small.
Instead, I stuck an old second hand zoom lens on the camera and caught this instead.
We’ve had beautiful clear skies here in Southend for the last week. Unfortunately, the moon’s been present for most of them. By the time it sets, there isn’t a lot left that my small telescope can see. Took a quick snap of the Beehive Cluster in Cancer though. (You have to use a bit of imagination sometimes to see anything remotely resembling their name in some objects.)
Platitude of the Day 
Superb pictures Peter!
Out of curiosity, what sort of exposure times did you need?
On a (very) rough order of magnitude guestimate, I’d expect anything slower than about 1/25 second t show some blurring from the Earth’s rotation [unless you have a special telescopic mount that compensates for this].
cheers
Birch
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ISO 200 1/60s
I’ve got a telescope that tracks things. It’s one of the very few pieces of equipment that I bought brand new.
SKYWATCHER HERITAGE 150P VIRTUOSO GTI
https://www.harrisontelescopes.co.uk/acatalog/skywatcher-virtuoso150p-telescope-.html
Almost everything else is second hand, mostly off ebay. The camera is a Panasonic GF3 mirrorless (£30). All my lenses are second hand.
The phone I use to control the telescope is second hand too (as is my main phone, as is my flute, all my computer stuff…).
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Thanks for the info.
By the way, I grew up in Southend, but haven’t been there since my Mum died, 10 years ago. DId you have much trouble with light pollution? It’s a big town. Or did you go out of town? From memory, places round Paglesham and Canewdon were far enough away to be dark.
cheers
Birch
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“DId you have much trouble with light pollution? It’s a big town. Or did you go out of town?”
I used to go out of town. There’s a field just outside Great Wakering that used to provide me some lovely views. However, back problems now mean that I’m limited to my back garden.
The council has been replacing streetlights with low light pollution versions for years. They’re still quite bright but at least they point at the ground now. I also have a lot of trees surrounding my garden. They’re both a blessing and a curse. They cut out a lot of surrounding light but often block bits of the sky that I’d like to see.
The worst thing is the current fashion for motion activated spot lights. Several neighbours have them and they come on at random, spoiling long exposures and ruining my night sight.
I’m at the north end of the town, near Garon park. Whereabouts did your mum live?
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I started reading this thinking that I was reading the latest TftD commentary. I was waiting for the other shoe to fall while thinking how is the idiot going to shoehorn God into this one? It’s been a long day.
Stonyground.
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It would be good if the Rev Dr Dr did the occasional TftD, based for example on what he has actually seen of the cosmos and how he knows it works. It would make a change from the all too many speakers who assert they know all about it, without being able to present any evidence other than what’s in their holy books. But that’s never going to happen.
Nice pics, by the way!
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I was thinking about doing a series on Pythagoras’ Theorem, how it extends to Special Relativity with its spacetime measure and discussing why there are exactly three dimensions of space and one of time (using Hamilton’s quaternions).
While discussing number systems I might offer some reasons why we need more than the real numbers to do Quantum Mechanics, and might even get onto the Dirac Equation.
I keep getting distracted by other things though.
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Peter, that sounds fascinating. Please do it!
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On these winter days I wonder if you could get a daylight shot too which would show even more mini phases?
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Yes, I think that would be perfectly possible. Although I may have to practise a bit setting up daylight shots. One problem is aligning the telescope during the day without any stars. I might experiment with some sticky tape to place the scope as close to the same position every time which might help.
I have managed a few daylight shots though.
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And while we wait for the sun and moon to grace us with their presence once again, here’s “The Sun whose Rays” sung by the the unsurpassed Valerie Masterson.
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I’m at the north end of the town, near Garon park. Whereabouts did your mum live?
Not far from you – in Sothchurch.
Although the parish church of Southchurch was at the bottom of the road, some of the neighbours liked to claim they lived in Thorpe Bay 🙂
[for non Southendians – Thorpe Bay was the posh end of town (but well over 2 miles away) — or at least it was considered so in my youth]
On another topic…
Without wishing to add an iota to your workload, can I add a vote for an idiot’s guide to quaternions? I’ve read about their definition and also about their use in rotating 3d models, but have no idea how they relate to physics.
cheers
Birch
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