Monday 24th to Sunday 30th April 2023

If you venture outside around 11pm on Tuesday 25th and look towards the west, a 32%-lit waxing Crescent Moon will be just to the right of planet Mars.  Look further right, down close to the horizon and you should be able to catch a glimpse of Venus just before it sets.


Go back outside and look to the west again a couple of days later, on Thursday 27th and Mars will appear to be roughly in the same position, but because the Moon is much closer to us and orbiting around the Earth every 27.3 days, it will appear to be in a different position.  This time it will be above and to the left of Mars.


As the Moon orbits around us, the angle of sunlight hitting its surface changes every day which causes the different phases.  On Tuesday you will have seen a crescent shape, but by Thursday evening it will have become what is known as a First Quarter.  The Moon is currently "waxing" which means that it is heading towards a Full Moon when you see the whole of the surface that faces us illuminated.  Then it will become "waning" as it heads back towards a New Moon.


While you are looking at the Moon on the Thursday evening, point your telescope slightly down and to the left of it to find the open cluster of stars known as the Beehive Cluster or M44 in the Charles Messier catalogue.  M44 is a bit further away from us than the Hyades cluster that we looked at last week - about 610 light years and it is also larger with around 1000 stars.



Monday 17th to Sunday 23rd April 2023

If you venture outside just after dark, say around 9.30pm, on Tuesday 18th and look towards the west, there is an interesting group of objects to spot.  Imagine a triangle - Venus will be at the top corner.  Down and to the right will be the Pleiades open cluster of stars that I've often mentioned.  Down and to the left of Venus, making the third corner of the triangle, will be the bright star Aldebaran and just below Aldebaran, another open cluster known as the Hyades.


The Hyades contains several hundred stars and is the nearest open cluster to us - only around 153 light years away.  Aldebaran appears close to the cluster because of the angle we are viewing it from in two dimensions.  In reality, Aldebaran is nothing to do with the cluster and it is much closer to us - 65 light years away.


Objects in space always appear two dimensional because the distance they are away from us is huge compared to the distance between your eyes.  When objects are very close to you, then the stereoscopic view from your eyes is three dimensional and you can perceive distances.  Try looking at some trees in your garden and then some on the horizon and you'll see what I mean!


On the evening of Saturday 22nd, a waxing Crescent Moon will have set below the horizon just before midnight.  This is great because the Saturday night / Sunday morning sees the peak of the Lyrid meteor shower.  The radiant point of the shower will be located towards the east, a little to the right of the bright star Vega in the constellation of Lyra.  The shower has a zenithal hourly rate of 18 meteors and the lack of light pollution from the Moon will be a bonus.




Monday 10th to Sunday 16th April 2023

On the evening of Tuesday 11th, planet Mercury reaches its greatest eastern elongation from the Sun.  In other words it will appear to be as far away from the Sun as it ever gets and so this is the best time to try and observe it.


If you venture outside just as it's getting dark, say around 8.30pm, then Mercury will be setting below the horizon to the west.  A little above and to the left of Mercury will be Venus shining brightly.


Wait until it is properly dark and you should see that Venus is very close to the Pleiades open cluster of stars.  By then, Mercury will have disappeared below the horizon.  To the left of Venus and the Pleiades will be the red giant star Aldebaran that I mentioned last week and further left again you will see the constellation of Orion with its red giant Betelgeuse and much younger, hotter star Rigel.


Orion is considered to be a "winter constellation".  During the winter months it appears high in the sky and you can easily observe it through most of the night.  During summer months it is close to the horizon and soon after dark, the constellation disappears below the horizon.


I was asked the other day why sometimes you can see Venus, but not at other times.  The reason is that Venus is orbiting the Sun closer than us - when the planet is the same side of the Sun to us, then we can see it close to sunrise or sunset.  When it is the opposite side of the Sun to us in its orbit, then we can't see it simply because the Sun is in the way!  I have created a diagram that plots the orbit of Venus as seen from the Earth and at the moment, the planet is placed very favourably.




Monday 3rd to Sunday 9th April 2023

On the evening of Thursday 6th we have a Full Moon.  If you venture outside around 9pm, the Moon will have just risen above the horizon towards the east south east.  To the left of the Moon, due east, will be the bright Star Arcturus in the constellation of Bootes.


Arcturus is an aging red giant star that is a little over 7 billion years old.  It is relatively close to us - around 37 light years away.  It has a similar mass to our own Sun, but as its core Hydrogen has been used up, Arcturus has expanded to 25 times the size of the Sun and is 170 times more luminous.  This explains why it is the third brightest star in the night sky with a magnitude of near enough zero.


Talking of bright things, of course the light pollution from the Full Moon means that it is not the best time to go hunting for faint deep sky objects - best to do that when we have a New Moon or it is below the horizon.


Go outside at the same time, 9pm, on Sunday 9th and Venus will be shining brightly towards the west, just below the Pleiades open cluster of stars.  To the left of the Pleiades you will find the bright star Aldebaran which is another red giant about 65 light years away.  Aldebaran is believed to have a planet several times the size of Jupiter orbiting around it.  These planets are known as "exoplanets" and we keep detecting more and more of them.


The Pioneer 10 space probe that NASA launched in 1972 is heading out of the Solar System in the general direction of Aldebaran, but you will have to wait a while for confirmation of that exoplanet as the probe won't get there for another 2 million years!


Pioneer 10 artist's impression courtesy of Wikipedia



Monday 27th March to Sunday 2nd April 2023

At the beginning of the week, the clocks will have just moved forward to British Summer Time or BST.  This can cause confusion for amateur astronomers as most reports are quoted in a worldwide standard time format called UTC that stands for Universal Time Co-ordinated.  It used to be called Greenwich Mean Time or GMT that we use during the winter months because the World's time zones are calculated from the Greenwich Observatory that happens to be in the time zone where we live!  For the next six months, you have to remember to allow for the extra BST hour.  To save confusion, I will always quote BST or our local time on Stars Over Somerset during the summer months so you can just look at your watch!

Time Zone map courtesy of Wikipedia

Last week I suggested trying to spot a thin Crescent Moon in the evening sky.  Venture outside around 1 to 2 am local time in the early morning of Wednesday 28th and a 39%-lit Crescent Moon will be setting towards the west with planet Mars shining brightly a little above it.


If you prefer not being up quite so late, you could go outside around 10pm local time on Thursday 30th and Venus will be setting to the west, located below the Pleiades open cluster of stars.  Just a bit down and to the left of Venus is a fun challenge if you've brought your telescope outside - planet Uranus shining at a magnitude of +5.8 where Venus is very bright at a magnitude of -3.9


Remember that the magnitude scale works back to front, so the brighter an object is in the night sky, then the more negative its number will be!



Monday 20th to Sunday 26th March 2023

On Monday 20th at 9.25pm, the centre of the Sun crosses the celestial equator.  What it means in practical terms is the marking of the March equinox - the point in the calendar when we have equal periods of day and night - the Earth's tilt of 23.5 degrees is sideways on to the Sun.  In the northern hemisphere, it is known as the Spring or Vernal Equinox.  The same happens again six months later when we have the Autumn Equinox.


In-between those dates, the northern hemisphere is either tilted towards the Sun which gives us summer, or tilted away when we have winter.


The Moon is always popular with amateur astronomers and for someone who is just starting in the hobby, it is an easy target to set up in your telescope.  But that isn't always the case!  If you venture outside just as it's getting dark, around 7pm on Wednesday 22nd and look towards the west, you will be presented with an extremely thin 1%-lit Crescent Moon a little underneath Jupiter as the pair set below the horizon. 


Above them and slightly to the left you will find Venus shining brightly.


If a 1% Moon is too difficult to spot, wait a couple of days and then around 8pm on Friday 24th, a 9%-lit Crescent Moon will be located just above Venus towards the west.


The following night, Saturday 25th at the same time, the Moon will have become 20%-lit and will be close to the Pleiades open cluster of stars.




Monday 13th to Sunday 19th March 2023

If you are up early on the morning of Wednesday 15th, the Moon will just past the third quarter phase and its libration (or wobble) means that the north west edge of the Moon's surface will be tilted slightly towards us.  At 5am on 15th, the Moon will be located towards the south.  The red super giant star Antares will be to the right of the Moon.


I previously mentioned an observing opportunity called the Messier Marathon and it takes place over the weekend of 18th and 19th March this year, when it is possible to see all 110 Messier objects over one night.  It coincides with a New Moon, so there will be no light pollution from our celestial neighbour.


Charles Messier was a French astronomer who lived in the 1700s.  His particular interest was finding and recording comets, but he kept getting confused by other fuzzy blobs in the night sky.  To avoid being caught out by them, he decided to log these deep sky objects and this became known as the Messier Catalogue.


His list contains open and globular clusters of stars, different nebulas or areas of gas and distant galaxies.  The first edition of the catalogue was published in 1774 and contained 45 objects.  Over the following ten years, it grew to 103.  Much later, in the early 1900s, a further seven objects were added that Messier had noted, but not bothered to formally add to his catalogue.


Why not have a go and see how many you can find!  Star charts showing the locations are readily available on the Internet - just search for "Messier Marathon".



Monday 6th to Sunday 12th March 2023

On Tuesday 7th we have a Full Moon rising above the eastern horizon just as it gets dark.  This is the worst possible time to go looking for deep space targets as the sunlight reflecting off the lunar surface creates the ultimate light pollution and ruins the contrast of fainter objects.


Later in the month, we have the opposite, with a New Moon creating zero light pollution.  This occurs at the same time as the optimum date for this year's Messier Marathon over the weekend of 18th / 19th when it is possible to see all the 110 objects that astronomer Charles Messier originally catalogued back in the 1700s.


But for now, going back to the Full Moon on 7th, you will find that looking at such a bright object in your telescope can be almost painful and it could damage your eyes.  Most astronomers use a special filter, known as a Neutral Density Filter, in front of the eyepiece.  It works a bit like a pair of sunglasses and reduces the amount of moonlight reaching your eye.


If at the same time, around 7pm, you look towards the west then Jupiter and Venus can be seen just before they set below the horizon.  Jupiter will be the lower of the two bright pinpoints of light.


Using a telescope will reveal the Galilean moons of Jupiter - the same view  Galileo saw when he realised that the Earth was not in the centre of the universe!  Viewing Venus through your telescope can show phases, just like our Moon and currently, Venus will appear to be about 85%-lit like a Gibbous Moon.  Coincidentally, Galileo was also the first person to observe the phases of Venus!



Monday 27th February to Sunday 5th March 2023

During February, Jupiter and Venus have appeared to be getting closer to each other in the early evening sky.  On Wednesday 1st March they will be at their closest.  If you venture outside just after dark, say around 7pm, the pair of planets will be setting towards the western horizon.  Jupiter will be to the left of Venus.


I've mentioned a technical term called lunar libration before.  It's where the Moon wobbles a bit as it orbits around us.  On Saturday 4th March the Moon's southern polar region is tilted favourably towards us, making it a good opportunity to go looking for some of the lunar features on that part of its surface.  Of course, the most obvious feature is the enormous crater "Tycho".


If you are outside around 7pm on 4th, the Moon will be located towards the south east.  If at the same time you look towards the west, Jupiter and Venus will still appear to be quite close together as they set, but by now Jupiter will be a little below Venus.

 For early risers, there are several excellent opportunities to spot the International Space Station during the coming week.  Monday 27th February at 6.17am, Tuesday 28th at 5.31am, Thursday 2nd March at 5.31am and Saturday 4th at 5.32am.  In all four cases, the ISS appears in the west and spends 5 - 6 minutes passing almost directly overhead before disappearing towards the east.

It will look like a bright star that is moving smoothly and silently across the sky.  The Space Station is travelling incredibly fast at a speed of 8Km/s and completes an orbit of the Earth every ninety minutes.  Some keen astronomers have even managed to track and photograph the ISS with amateur equipment!


ISS image courtesy of Mark White / Sky At Night Magazine