I'm going to continue last week's theme of things appearing close to each other, but this week the observations will be a bit more tricky!

First of all, if you fancy an early morning start on Monday 23rd, look towards the east north east at 3.30am to see a thin 7%-lit waning crescent Moon rise above the horizon.  To the right of the Moon will be a very bright planet Venus.  The Moon will also appear to be extremely close to the Pleiades open cluster of stars.  If you oversleep, the challenge will become virtually impossible in the dawn twilight sky!

Pop back outside on the evening of Friday 27th, around 10pm, to see a 7%-lit waxing crescent Moon setting towards the west north west horizon.  Slightly to the right of the Moon and closer to the horizon, you could try to spot planet Mercury, while to the left and higher in the sky, Mars will be more obvious.

We will have had a New Moon on Wednesday 25th, so the crescent you observed on Monday is classed as "waning" and you will notice that it was the left hand limb of the Moon that was illuminated.  On Friday, the crescent will be "waxing" and this time, it will be the right hand limb of the Moon's surface that is lit-up by sunlight.

"Waxing" and "waning" are old English terms meaning "becoming brighter or stronger" and vice versa.  The Moon is described as "waxing" as it heads towards a Full Moon, when it is at its brightest.  Because of the angles between us, the Sun and the Moon, when it is waxing, the right hand side of its surface is always illuminated and if in a waning phase, then the left hand side is lit-up.

It's going to be a week of things appearing close to each other, starting with Mars sitting just above the bright (magnitude +1.3) star Regulus.  The date and time for your diary is Monday 16th, around 11pm and you will need to be looking towards the west, as Mars will be setting below the western horizon a little later.

Saturn appears to be near a last quarter Moon in the early hours of Thursday 19th.  The pair will pop up above the eastern horizon around 2am.

If you've brought your telescope out, a faint magnitude +7.8 planet Neptune will be located roughly half way between the two.

Stay up until 4am - the Moon and Saturn will have drifted towards the south east while a bright planet Venus appears to the east in the dawn sky.

Believe it or not, Saturday 21st is the Summer Solstice, when the Sun reaches is most northerly declination (or highest point).  Pity it doesn't really feel like it!

Pop back outside again in the early hours of Sunday 22nd to see a 15%-lit waning crescent Moon close to Venus.  The pair will be rising above the east north east horizon around 3.30am and at this point, Venus will have a magnitude of around -4.1 which is very bright.

On the evening of Tuesday 10th we have a Full Moon.  Around 11pm, the Moon will be approaching the south and you will notice that it appears very low in the sky, close to the horizon.

This unusual occurrence is known as a "major lunar standstill".  What on Earth does that mean?  The Moon's orbit around us is anything but symmetrical and every 18.6 years, its declination (or angle between the Moon's orbit and the equator) reaches a minimum.  This is what's happening on the 10th.

Lunar standstills had particular significance for people back in the Bronze Age and they built monuments to line up with the direction in which the standstill occurred.

Because the Moon will be so close to the horizon, observers will also experience a phenomenon called "Moon illusion" where our natural satellite appears much larger than normal.

It isn't really larger (or closer to us) and the effect is purely a trick that your brain plays on you when looking at objects near the horizon.  A logical way of understanding it is that the Moon will seem smaller compared to objects on the Earth that are close to you, but larger compared to objects in the distance.

Lunar size comparison image courtesy of C M Glee

Sticking with the Moon, go back outside around 1am on Sunday 15th and a waning gibbous Moon will be poking its head up above the south east horizon.  The Moon's libration or "wobble" favours its western limb, where you can find the Mare Orientale.

The evening of Wednesday 4th, around 11pm, is the optimum time to spot one of those clair-obscur visual effects on the lunar surface.  This time, it's the turn of "Plato's Hook", so named because the shadow of crater Plato's rim creates a curved shape.

At 11pm, a waxing slightly-gibbous Moon will be located towards the south west.  Plato is situated on the northern part of the Moon's surface, on the edge of Mare Imbrium.  The crater itself is about 100Km in diameter.

If you look towards the east around the same time, any evening next week, try to identify an area of the sky known as the "Summer Triangle" that has its three points marked by the stars Deneb in Cygnus, Vega in Lyra and Altair in Aquila.

Astronomers love this part of the sky as it contains numerous deep sky targets for your telescope.  Some of them, like the Dumbbell Nebula M27 and Ring Nebula M57 appear in the Charles Messier catalogue.  Others are listed in the New General catalogue and a great one of these to observe with your telescope is called the Blinking Nebula.  The nebula does not blink on and off!  It has a bright centre star and if you use your peripheral vision in the eyepiece to look at the nebula's gas through the side of your eye, you will see it.  Stare towards the centre and the gas of the nebula will seem to disappear as the light from the star overwhelms your eye!

Sir Patrick Moore liked it so much, he included the nebula in his Caldwell catalogue of interesting objects for amateur astronomers,  where it is listed as number 15.

 On Tuesday 27th we have a New Moon, when the entire surface of the Moon that faces us is in shadow.  By Saturday 30th, it will have become a thin waxing crescent shape, as just a little bit of the surface facing us is illuminated by sunlight.

If you venture outside just after dark on the Saturday evening, say around 11pm, the crescent Moon will be setting towards the west north west, with planet Mars to the left of it, due west.

Because the Moon takes the same amount of time to orbit around us as it takes to rotate on its own axis, the same face of the Moon is always pointing towards us.  Some lunar features like the crater Tycho and the Sea of Tranquility are always visible when the surface is illuminated.  You can also identify the locations of all the Apollo Moon landings as no missions attempted to explore the "dark side of the Moon".

As it orbits around us, the Moon does experience a phenomenon known as "libration" or in other words, it wobbles a bit!  This means that sometimes you can see a little further around the western or eastern limbs of its surface.

On Saturday 30th, libration favours the eastern edge and you should be able to see the Mare Marginis and Mare Smythii that are about 360Km and 200Km in diameter respectively.

Unlike most seas or "mare", Marginis has an irregular outline and small features that are thought to be the result of impact craters being covered by lava.  Of course, you will need a telescope to see such detail.

If you are an early riser, look towards the east around 4am on Saturday 24th to see a 12%-lit waning crescent Moon just to the left of a very bright planet Venus.  At the same time, further to the right of Venus, you will find Saturn.  Venus will be shining very brightly at a magnitude of around -4.5 while Saturn will be dimmer, at a magnitude of about +1.1

Using a telescope to observe Venus will reveal it to be a beautiful crescent shape at this point in its orbit around the Sun, relative to us.  It will look almost like a last quarter Moon.

If an object is located between us and the Sun, you can observe different phases, but if a planet is further away from the Sun than Earth, then you will only ever see it as a fully-illuminated disc.

If you have brought your telescope out, then you could also have a go at observing the dust rings around Saturn, although they are currently sideways-on to us, so not in the greatest position.  Some of Saturn's many moons should be obvious though.

By 5am, the Sun will be rising, so please make sure that your telescope is packed away by then!  You will notice that because they are so bright, the Moon and Venus will still be visible, but Saturn will have disappeared from view in the dawn sky.

Something for the evening observers - May sees the start of the noctilucent cloud season, where sunlight is scattered by ice crystals in the upper atmosphere at twilight.  There were some great occurrences of this phenomenon in 2024, so keep your fingers crossed!

Noctilucent cloud image courtesy of Wikipedia

Whenever astronomers talk about globular clusters, that can contain thousands to millions of stars bound together by mutual gravity, they always refer to the Great Globular Cluster in Hercules, also known M13 in the Charles Messier catalogue.  There are other nice examples though and one in particular is well-placed in the night sky at the moment - M5 in the constellation of Serpens "The Snake".

If you aim your telescope towards the south around 1am in the early morning of Friday 16th, the cluster can be found below and to the left of the bright star Arcturus.  You could try a little earlier in the night or earlier in the week, but we had a full Moon on Monday 12th and if you leave your observing until after 1am, then (what will be a waning gibbous Moon) will have risen above the horizon, creating lots of light pollution.

The cluster can be a little tricky to find.  Firstly, the constellation of Serpens is unusual because it is split into two halves.  The right hand part of the constellation goes by the wonderful name of "Serpens Caput".  M5 is to the right of this, just above the star "5 Serpens".

The cluster was first observed as a fuzzy blob by German astronomer Gottfried Kirch while he was tracking a comet back in 1702 and Charles Messier added it to his list in 1764 so he wouldn't get fooled during his own comet-hunting activities.  It wasn't until 1791 that the astronomer William Herschel identified individual stars within the cluster and counted 200 of them.  The cluster is about 24,000 light years from us and heading away at a speed of 50Km/s.  Although that sounds fast, in astronomical terms it isn't, so you'll be able to observe the cluster for a good few million years yet!

In the early morning of Monday 5th, we will be just past a first quarter Moon and this is the optimum time to look for that clair-obscur visual effect known as the Lunar X and V.  At 1am on the Monday morning, the Moon will be located towards the west, with planet Mars a little below and to the right of it.

While you are trying to spot the "X" and "V" shapes, it will also be very easy to find the Sea of Tranquility to the right of them, where Apollo 11 made the first Moon landing back in 1969.

A good question I am sometimes asked is whether there is a telescope on the Earth powerful enough to see the descent state of the Lunar Landing Module or the American flag that Apollo 11 left behind.  The short answer is "no" unfortunately.  The smallest features we can see with a telescope are still several kilometers across at least and compared to that, the Apollo hardware is miniscule!

If you've brought your telescope out to see the "X" and "V", you could also aim it towards Mars and try to observe its polar ice cap.  You may notice that Mars is extremely close to the Beehive open cluster of stars, known as M44 in the Charles Messier catalogue.

The cluster contains about 1000 stars and is between 500 - 600 light years away from us.  It's existence has been known about since ancient times and the cluster was first observed by the Greek mathematician Ptolemy around 150AD.  Galileo made observations of it in 1609 with his basic telescope and Charles Messier added the cluster to his list in 1769.  Because the light takes so long to reach us, if you do observe the cluster next week, you will be seeing it how it was before Galileo was even born!  The cluster is about 600 million years old, so to be fair, its structure won't have changed much over the last few hundred years!

In the dawn twilight of Monday 28th, Venus will be an easy target to spot shining at a magnitude of -4.4 which is very bright.  Around 5am, Venus will be located towards the east, with a harder-to-see, magnitude +0.8 Saturn a little below and to the right of it.

Using a telescope will show Venus as a beautiful crescent shape, but please be careful, as the Sun will be rising in the same direction shortly afterwards and you mustn't risk catching an accidental glimpse of it in your eyepiece!

Sticking with crescent shapes, look towards the west as darkness falls on the evening of Wednesday 30th, around 9pm, to see a 13%-lit waxing crescent Moon, with a magnitude -1.8 Jupiter just below and to the left of it.  Further left and closer to the horizon will be the red giant star Betelgeuse in the constellation of Orion.

You may notice a bright star just above the Moon.  This is Elnath that is a blue-white giant star and the beta star (or second-brightest) in the constellation of Taurus.  Elnath has a magnitude of +1.65  making it the 27th brightest star in the night sky overall.  By comparison, Betelgeuse shines at an average magnitude of +0.5 and is the 10th brightest - remember the magnitude scale works backwards!

Finally there are three good opportunities to spot the International Space Station next week, but you will need to be an early riser!  Tuesday 29th April at 4.20am, Thursday 1st May at 4.20am and Saturday 3rd May at 4.21am.  In each case, the ISS will appear in the west and spend over five minutes passing almost directly overhead, before disappearing towards the east.