The Engagement Ranger at Ham Hill, where I run some of my astronomy talks, asked me a question the other day and it prompted me for an interesting topic here.  She had seen a white ring around an almost-full Moon - a phenomenon known as a "Moonbow".

This is a rare occurrence where sunlight reflected from the lunar surface is refracted by water droplets as it passes through our atmosphere.  If the light is quite strong, you may even see the colours of the rainbow, just like a regular rainbow here on the Earth, although the Earth-based ones are much more obvious as the sunlight is coming direct from the Sun and so is far more intense.

White light, that originates from the Sun, is a combination of the three primary colours - red, green and blue.  If white light reflects off a surface (like a mirror) it stays as white light.  If white light passes through a lens or prism (or in this case, water droplets), then the different wavelengths of light or colours take slightly different paths and it has the effect of splitting up the colours - this is refraction.

The sky is blue during the day because white light coming from the Sun is scattered by tiny air molecules.  Blue light has a shorter wavelength than red, so the blue light is scattered more - hence the sky looks blue.  When the Sun is low in the sky at sunrise and sunset, its light has to travel further through our atmosphere and then the blue light gets scattered so much that the red light, which has a longer wavelength, can then pass through and be detected by your eyes.

Having mentioned Ham Hill at the start.....a reminder that my next astronomy talk and star party at their Visitor Centre is scheduled for the evening of Friday 28th February.  Please contact the Rangers Office on 07973 887129 to reserve a place.

At the moment, Venus is a spectacular sight in the early evening sky as it sets below the western horizon.  It is currently shining at a very bright magnitude of around -4.5 so easy to spot with the naked eye.  Because Venus is between us and the Sun, it is also possible to observe different phases, just like our Moon.  You need a telescope to be able to see the phases however.

Look towards the west south west at 7pm on Monday 10th to find Venus, with Saturn below and to the right of it, just about to disappear below the horizon.

Please don't be tempted to set-up your telescope too early though, as you mustn't risk catching an accidental glimpse of the setting Sun in the eyepiece.

We used to consider Venus to be our sister planet and possibly a refuge if we needed to abandon the Earth.  To ancient Greeks and Romans, Venus represented the goddess of love.  In reality, nothing could be further from the truth!

Venus has a very dense atmosphere comprised mainly of Carbon Dioxide with Sulphuric Acid clouds.  The thick atmosphere traps heat and the surface temperature is almost 500 degrees Celsius.  This "greenhouse effect" in turn causes high pressure some 92 times that of the Earth!  In other words, if you tried to land on Venus you would be suffocated, dissolved, cooked and squashed.....but not necessarily in that order!

Views in the eyepiece can be very deceiving sometimes!

At 10.45 pm on Wednesday 5th February, a 55%-lit waxing gibbous Moon will be located towards the west, with the Pleiades open cluster of stars and planet Jupiter above and to the left of it.

This is the optimum time to try and identify another of those clair-obscur visual effects on the lunar surface known as the "Stars of Aristillus".  The crater Aristillus is located towards the top of the Moon.  It is 55Km in diameter and prominent peaks in the centre of the crater's flat surface create the visual effect.

If you've brought your telescope out to see the Stars of Aristillus, at the same time, planet Uranus at a magnitude of only +5.7 will be located a little below and to the left of the Moon.

A few weeks ago I mentioned the Moon's libration or wobble.  On Thursday 6th, this wobble favours the south east part of the lunar surface where there is a cluster of dark lava-filled craters right on the edge of where you can see.

Around 7pm on 6th, the Moon will be found towards the south, above Jupiter and the constellation of Orion.  Look to the west and you should be able to catch Saturn and Venus setting below the horizon.

Go back outside again around 7pm on Sunday 9th and the Moon will be located towards the south east this time.  It will appear more gibbous now, with a greater percentage of the surface illuminated, as the Full Moon is only a few days away.  Mars will be very close to the Moon's south east limb and easy to spot with just the naked eye.

I haven't made much mention of deep sky objects recently - targets that are outside of our Solar System and much further away.  Well the evenings next week are an ideal opportunity to go hunting them as the Moon will be below the horizon and not causing any light pollution.

Look towards the south around 9pm any evening next week and the constellation of Orion will be easy to spot with Mars above and to the left of it.  Jupiter and the Pleiades open cluster of stars will be above and to the right of Orion.  At this point, the constellation will be at its highest in the night sky, so less atmospheric disturbance.

Let's focus our telescope on what is called the "sword" of Orion to find the Great Orion Nebula, also known as M42 in the Charles Messier catalogue.  You are looking for a faint fuzzy blob half way down the sword.

M42 is known as an "emission nebula" because its gas is very active and radiating its own light.  It is an area where new stars are born and is about 1600 light years away from us.

When you see a photograph of the nebula, it is always in glorious techni-colour and looks stunning.  This is because a camera soaks up light (a bit like a sponge) and the image will be heavily processed to highlight detail.  When using an eyepiece in real time, your eye only senses a little bit of light and cannot resolve colour at those low levels.

This is why the lack of Moon is important, as sunlight reflecting from the lunar surface spoils the contrast of deep sky objects in your eyepiece.

Because the Moon takes the same time to rotate on its axis as it does to orbit around us, we always see the same face and are never able to see what is called the "dark side".  However, our natural satellite exhibits something called "libration" which means it wobbles a bit and sometimes we can see a bit further around the surface than at other times.

A couple of weeks ago I mentioned the seas or "mare" on the lunar surface and the obvious Sea of Tranquility where Apollo 11 landed.  The Mare Orientale on the western limb of the Moon is much harder to spot, but on Saturday 25th, the Moon's libration tilts Mare Orientale and a crater near it called Grimaldi into a slightly more favourable position.  You will need to be up early though, to catch what will be a crescent Moon, rising above the south east horizon from 6am.

There are a number of excellent early evening opportunities to spot the International Space Station next week:

Monday 20th at 5.46pm

Tuesday 21st at 6.34pm

Wednesday 22nd at 5.45pm

Thursday 23rd at 6.33pm

Friday 24th at 5.45pm

At least one of those evenings has got to be clear surely!

You are looking for a bright pinpoint of light that appears towards the west and spends up to six minutes passing silently overhead, before disappearing to the east.

Finally, a reminder that my next astronomy talk and star party at the Ham Hill Visitor Centre is scheduled for 7pm on Friday 31st January.  To reserve places, please contact the Ham Hill Ranger's Office direct on 07973 887129.

If you look towards the south east at 7pm on Monday 13th, Jupiter will be an easy "naked eye" target, shining at an extremely bright magnitude of -2.6 and sitting above the constellation of Orion.

Whip your telescope out and there is an opportunity to see the shadow of Jupiter's moon Ganymede as it transits across the face of the planet.  The shadow should be visible until 9pm.  With even a modest telescope or binoculars, you should be able to observe all four of Jupiter's Galilean moons - Io, Europa, Ganymede and Callisto.

Sometimes you can't see all four moons at once because as they orbit around the planet, the moons are blocked from our view, but at 7pm on 13th they will all be visible.  At that point, you will actually be witnessing what Galileo saw in the 1700s, when he first realised that we orbit around the Sun along with the other planets in the Solar System.

When the transit of Ganymede's shadow has finished, look to the left of Jupiter and a Full Moon will be very close to planet Mars.  Mars will be easy to spot at a magnitude of -1.4 and it has an obvious red tint.

Of course, around the time of a Full Moon, its light pollution spoils the contrast of faint deep sky objects, so let's stick with our neighbours in the Solar System.

Look towards the south west around 7pm on Saturday 18th to see a magnitude -4.6 Venus close to a dimmer magnitude +1.1 Saturn as the pair set below the horizon.

On Monday 6th, a little after dark, there is an opportunity to see the clair-obscur visual effect known as the "Lunar X & V" on the Moon's surface.  At 6pm, a waxing quarter Moon will be located towards the south, with Venus and Saturn disappearing below the horizon to the south west, while Jupiter and the constellation of Orion will be found towards the south east.

Sunlight falling at particular angles on the Moon creates different visual effects at different times during its orbit around us and in the case of the "Lunar X & V" (that resemble the shape of those two letters in the alphabet) the effect can be seen on the terminator, which is the barrier between sunlight and darkness on the Moon's surface.  The "X & V" are only visible for a brief period at the time of a waxing quarter Moon and are caused by sunlight hitting the rim of certain craters.

You will need binoculars or a telescope to see the shapes, but beside the "V" is a dark, flat area called the Sea of Tranquility that can easily be spotted with the naked eye.  It is where Apollo 11 landed in 1969.

Early astronomers with basic telescopes used to think that because these areas were dark and flat, they must be oceans of water.  Of course we now know that not to be the case.  The Sea of Tranquility does have a slightly bluish tint however, which is thought to be due to a higher metallic content in its rocks - nothing to do with water at all!

Sticking with the lunar theme this week, if you go back outside around 9pm on Thursday 9th, an 81%-lit waxing gibbous Moon will be located towards the south, just to the left of the Pleiades open cluster of stars.

How about celebrating the beginning of the New Year with a simultaneous occultation and transit?  Sounds a bit like some sinister black magic ceremony, but we're actually talking about a couple of Jupiter's Galilean moons!

From 9.45pm on Thursday 2nd, Ganymede is occulted by the planet as this largest of Jupiter's moons orbits behind the gas giant and so is blocked from our view.  Ganymede reappears from behind Jupiter again at 11.50pm.  At the same time, Io begins to transit in front of the planet and about half an hour later, its shadow will be cast on the planet.

During the event, Jupiter will be very easy to spot, shining very brightly at a magnitude of around -2.7 and located towards the south, above the constellation of Orion.  Mars will be to the left of them, shining at magnitude -1.2 which is also pretty bright!

Of course, although the planets themselves are easy "naked eye" objects, you will need a telescope to be able to see Jupiter's moons doing their thing!  Our Solar System neighbours always look bright because they are relatively close to us and you can only see them because sunlight reflects off the planets' surfaces.  Stars are fainter because they are much further away and radiating their own light.

The evening of Friday 3rd into the early morning hours of Saturday 4th sees the peak of the annual Quadrantids meteor shower.  At midnight, the radiant point, where the shooting stars appear to originate from, will be located towards the north east.

I have managed to sneak a preview of the top secret plans for Santa's route on Christmas morning, delivering all the presents!  If you are up early and it is a clear sky, you might be able to see him.  Look towards the north north west at 6.08am on 25th and you should be able to spot what looks like a bright star, travelling almost directly over your head.  It will disappear towards the east three minutes later.

You won't be able to make out Santa's sleigh or the individual reindeer because they are so high up and travelling so fast to be able to visit all the houses around the World - just look for that pinpoint of light travelling at supersonic speed!

Keeping with the festive theme.....how about a free gift?  For years I have used some free software on my computer called Stellarium to plan an evening's stargazing and to make the screenshots that I post on the Stars Over Somerset website.  It is excellent and in many ways, superior to the commercial software packages that can cost a small fortune!

Well Stellarium is also available through the App Store as a free download for your phone.....and it works brilliantly if you are outside and would like to know what you are looking at in real time.

It will even show you the International Space Station when it is passing over the UK, like on the morning of 25th.

On that note, it just remains for me to wish all our listeners a very peaceful Christmas and clear skies for the New Year. 

We've all had enough of the recent weather forecasts and storms, but did you know that scientists are also interested in what is called "Space Weather"?  It is a branch of space physics concerned with the effect that the Sun has on our planet - things like the radiation from solar flares and the Solar Wind.  Space weather can cause disruption to our radio communications and is also responsible for creating those visual Auroras that could (unusually) been seen from here in the UK this year - guess space weather can have extremes, just like our own weather!

Saturday 21st is the Northern Hemisphere's winter solstice - the time when the Sun reaches is most southerly declination or lowest maximum height above the horizon.  This represents the shortest day, so it will now start staying lighter in the evenings by about 4 minutes each day.  Everyone works on an Earth day being 24 hours long, but in reality it takes 23 hours 56 minutes and 4 seconds for the planet to rotate once, hence the difference of roughly 4 minutes.

Sunday evening 22nd sees the peak of the annual Ursids meteor shower.  The radiant point is located near the constellation of Ursa Minor, which is itself easy to find, because the constellation includes Polaris, the pole star, located towards true north.

Polaris is the alpha (or most significant) star in the constellation.  The radiant point of the shower is close to Kochab, which is the beta star.

Best to look for the shooting stars before 11pm as a 58%-lit gibbous Moon will then be rising above the horizon, creating some light pollution and spoiling your view.

Just after dark, say around 5pm, on Tuesday 10th, a waxing slightly-gibbous Moon will have risen above the horizon to the south east, with Saturn further to the right of it.

This is the optimum evening to have a go at spotting the clair-obscur lunar visual effect known as the Jewelled Handle.  Sunlight hitting the Montes Jura mountain range at an angle on the Moon's surface produces what looks like the shiny handle of a teapot!

Venture out again around 5pm on Friday 13th and a 96%-lit waxing very-gibbous Moon will now be located towards the east, extremely close to the Pleiades open cluster of stars.  Jupiter will be a little below and to the left of it.  Of course, light pollution from the almost-full Moon will spoil your view of the cluster.

A similar problem occurs on Saturday 14th when the Moon is just one day away from being full and it ruins the peak of the annual Geminids meteor shower.  If you do want to try and spot a few shooting stars, the radiant point of the shower is in the constellation of Gemini, which by 9pm on the Saturday evening, will be found towards the east.

Looking in that direction, you should also be able to see Jupiter and Mars while waiting for those elusive meteors to show up.  To the right of Gemini will be the obvious constellation of Orion with the bright stars Betelgeuse and Rigel, while above Orion you can find the constellation of Taurus with the bright star Aldebaran.

Take a look towards the south around 5pm on Thursday 5th to see a very bright magnitude -4.0 Venus setting below the horizon.  To the left of Venus, you will find a waxing crescent Moon.

You'll notice that the crescent shape, where sunlight is illuminating the lunar surface, is on the right.  This tells us that our celestial neighbour is "waxing", or in other words, heading towards the Full Moon on 15th December.  After the Full Moon, it is said to be "waning" and because of the angles between us, the Sun and Moon, the illuminated part will then appear to be on the left side of the Moon's surface.

If you look towards the south again at 5pm on Sunday 8th, Venus will be setting below the horizon once more, while further to the left and a bit higher in the sky, a magnitude +1.0 Saturn will also be easy to spot.  At the same time, a first quarter Moon will only be a few degrees away from Saturn.  Again, it will be the right hand side of the Moon's surface that is illuminated.

When you've finished observing them, a magnitude -2.0 Jupiter will be rising above the horizon to the east north east.  Above and to the left of Jupiter is the bright star Capella, while to the right you can find the Pleiades open cluster of stars.  All of these targets are easy "naked eye" objects, so no telescope or binoculars required!

My next astronomy talk and star party at the Ham Hill Visitor Centre is taking place at 7pm on Friday 6th December.  The last one filled very quickly, so if you'd like to come along, it is essential to reserve a place by contacting the Ranger's Office on 07973 887129.

If you look towards the east at 8pm on the evening of Tuesday 26th, the constellation of Orion will have just risen above the horizon, with Jupiter a little higher.

Around 8pm, Io will be passing (or transiting) in front of the planet and because of the angle that sunlight is illuminating the event, Io's shadow will be cast on the planet's surface.  See if you can make out what will look like a small black dot against the clouds of Jupiter's storms.

Io is the third largest of Jupiter's Galilean moons and a little larger than our own Moon.  It would be a pretty nasty place to live, with over 400 live volcanoes, making it the most geologically active object in our Solar System.  Being the closest moon to Jupiter, it is also constantly bombarded by magnetic radiation from the planet.  Io was the first moon identified by Galileo back in 1610 with his new-fangled invention called a telescope!

There are a couple of potentially excellent International Space Station passes next week if the skies are clear: Tuesday 26th at 6.17pm and Wednesday 27th at 5.28pm.  In both cases, the ISS appears in the west and spends several minutes passing almost directly overhead, before disappearing towards the east.

Finally, a reminder that my next astronomy talk and star party at the Ham Hill Visitor Centre is taking place at 7pm on Friday 6th December.  The last one filled very quickly, so if you'd like to come along, it is essential to reserve a place by contacting the Ranger's Office on 07973 887129.

If it's a clear evening, Wednesday 20th is when it's all happening next week.  If you look towards the south south west around 8pm, Saturn will be an easy target to spot.  Aiming a telescope towards the planet will reveal the shadow of Saturn's moon Titan as it passes in front of the planet.  The transit begins a little before 8 o'clock and will be all over by 11 o'clock.

When you've had enough of Titan, take a look towards the north east and a 70%-lit waning gibbous Moon will be rising above the horizon at 9pm, with Mars just below and to the right of it.

Further right, towards the east, will be the constellation of Orion, with Jupiter above it.  Orion is great for teaching astronomy, with lots of interesting things to see.  Betelgeuse is a great example of a giant red star, while on the opposite side of the constellation, Rigel is a much younger star that appears to have a blueish tint because it is much hotter.

If you still have your telescope out, the Orion Nebula (Messier 42) is a stunning target that can be found half-way down the "sword" of Orion.  The nebula's gas, where stars are being born, is around 1600 light years away, so if you look at it on Wednesday evening, you will be seeing the gas how it was 1600 years ago because its light has taken that long to reach us!

The best pass of the International Space Station next week occurs at 6.16pm on.....guess when.....Wednesday 20th, when it will appear in the west and spend about 4 minutes travelling almost directly overhead before disappearing towards the east.

The evening of Monday 11th sees the peak of the Northern Taurids meteor shower.  At 11pm, the radiant point (where the shooting stars appear to originate from) will be located towards the south east, just below the Pleiades open cluster of stars.  A little below and to the left of the radiant point you will find the bright star Aldebaran and planet Jupiter.  Below them, the constellation of Orion will be easy to spot.

If you look towards the south west at 11pm the following evening, Tuesday 12th, a 79%-lit waxing gibbous Moon will be an easy find.  Below and to the right of the Moon, Saturn will be about to set below the horizon.  Halfway between the two, telescope or binocular users should be able to spot a magnitude +7.7 planet Neptune.  Immediately beside Neptune is a star HIP117614 with about the same brightness and the pair could be confused for a double star system.

The HIP number refers to the Hipparcos Catalogue that was the result of the European Space Agency's Hipparcos mission in the early 1990s.  The Hipparcos satellite made high-precision measurements of almost 120,000 stars during its four-year life.

The evening of Friday 15th sees a Full Moon.  By 7pm, the Moon will have risen nicely to the east, with the Pleiades to the left of it and further left, Jupiter will just be poking its head above the horizon.  This Full Moon is known as a Supermoon because it occurs near perigee, when the Moon is closest to Earth during its orbit around us.  At this time, the Moon appears 14% larger and 30% brighter than when it is furthest away from us - a point called apogee.  An easy way to remember which is which is to think that at apogee, something is "apologising" for being further away!

First of all, a bit of a visual challenge just as it's getting dark on Monday 4th.  Look close to the south west horizon around 4.30pm and see if you can spot a thin 9%-lit waxing crescent Moon.  A little above and to the left of the Moon will be a very bright planet Venus, shining at a magnitude of about -4.0 so easy to find against the dusk sky.

If you look towards the south west any evening next week in the late evening, Saturn will be easy to spot with the naked eye at a magnitude of around +0.8 but it is not a great time to observe the rings of dust around the planet because their current "end-on" angle to us makes them appear to be very thin.

However this works to your advantage as Saturn's many moons are in the same plane as the rings, so appear to be nicely spaced out in their orbits around the gas giant.

At different times next week, three of Saturn's moons pass in front of the planet and cast a shadow on its surface.  Of course you will need a telescope to be able to observe what will look like a tiny black dot on the face of the planet.  The offending moons are Titan from 9pm on Monday 4th, Rhea from 11.30pm on Tuesday 5th and Dione from 7pm on Thursday 7th.  Because the time is a little earlier on the Thursday, Saturn will be more towards the south that evening.

Saturn is known to have 146 moons and their orbital periods (or the time they take to go around the planet) vary considerably, depending on how far they are away from the planet.  If you look at Saturn on the different evenings, the moons will therefore all appear to be in completely different places each time.

Screenshots courtesy of Stellarium

Copyright Adrian Dening and Radio Ninesprings 2025