If you are up at around 3am on the morning of Thursday 27th, a gibbous Moon will have risen above the horizon towards the south east.  Just to the left of the Moon will be Saturn, shining quite brightly at a magnitude of around +0.7

Remember that the Moon appears to travel differently across the night sky compared to the planets, because the Moon is orbiting around us every month while the planets, like our own Earth, are orbiting around the Sun every year.

To prove this, if you repeat the experiment at 3am on Friday 28th, the Moon will be slightly more towards the east and this time, Saturn will be located to the right of the Moon.

How about trying to spot the dwarf planet Ceres in the Asteroid Belt?  At 1am on Sunday 30th, the constellation of Sagittarius will be sitting just above the horizon to the south.  Sagittarius contains an "asterism" or easily-recognisable shape known as "The Teapot".

Ceres will be located just below the handle of the teapot.  The little 900Km diameter planet will only have a magnitude of about +7.3 so it will be time to dig that telescope out as with the naked eye from a dark location, you can only resolve objects to a magnitude of around +6.0

Ceres was the first asteroid ever identified, back in 1801 and it is considered to be a dwarf planet rather than just a lump of rock like other asteroids because of its complex composition that includes water ice and different minerals.

Believe it or not, it is actually summer at the moment!  On Monday 17th we have the earliest sunrise of the year, officially at 4.42am in London.  From here in the south west, it actually occurs about ten minutes later because we live at a more-westerly longitude.

Confusingly, the Summer Solstice, when the Sun reaches its most northerly point in the sky, takes place on Thursday 20th.  The Earth's axis is tilted approximately 23.5 degrees and on 20th June, that angle makes the northern hemisphere point more towards the Sun.  At midday, the Sun will be directly over the latitude line known as the Tropic of Cancer.

Six months later, the opposite happens and the northern hemisphere is tilted away from the Sun......or in other words we have the winter solstice.

Stonehenge was built to align with the Sun on the solstices and every year, many people make a pilgrimage to the historic site.  English Heritage are allowing free access to Stonehenge between 7pm on the Thursday evening and 8am on the Friday morning.  You have to visit their website and pre-book because parking is very limited and although access to the site is free, there is a parking charge per vehicle.  For those that can't make it, there will also be a livestream of the event on the English Heritage website.

Over the last few weeks I have been mentioning deep sky objects: open and globular clusters of stars, areas of gas known as nebulas and galaxies which are collections of billions of stars, like our own Milky Way.

Well there are actually five different types of nebulas and I am often asked about them, so thought it would be an interesting topic for Stars Over Somerset.

First of all we have "Emission Nebulas" and the best example is the Great Orion Nebula, M42 in the Charles Messier catalogue.  These are large areas of ionised Hydrogen gas that emit light and they are "stellar nurseries" where stars are being born.

Secondly we have "Reflection Nebulas" such as M45.  Hang on.....isn't M45 the Pleiades open cluster of stars?  Well yes it is, but with a powerful telescope, you can see the remains of the gas that created the stars - the gas isn't giving off its own light anymore, but it is illuminated by the reflection of light coming from the recently-formed stars. 

The next type of nebula is known as a "supernova remnant" such as the Crab Nebula M1 in the constellation of Taurus.  These nebulas are the leftovers from a star that has exploded as a supernova.

Then we have "Planetary Nebulas" that have nothing at all to do with planets!  A good example is the Dumbbell Nebula M27 in the Summer Triangle.  These are glowing ionised gases ejected from a dying red giant star.  The misnomer originates from the 1700s when using early telescopes, astronomers thought their round shapes looked like planets!

Finally, a "dark nebula" like the famous Horsehead Nebula in Orion is a cloud of gas and dust that is revealed due to the bright material and stars behind it.  The nebula is silhouetted against the bright background which creates interesting shapes.

On Wednesday 5th the crescent Moon will have risen above the north east horizon by 4am, just as it's getting light.  You might be able to identify planet Mars at the same time over towards the east.  Please don't be tempted to use binoculars or a telescope though, as the Sun will be rising in the same area.

If evenings are more your thing, on Friday 7th the crescent Moon will be setting towards the north west just as it's getting dark, say around 10pm. One curious thing to note is that a waning crescent always appears to be on the left edge of the Moon, where a waxing crescent is always on the right.

The coming week would be an ideal opportunity to dig that telescope out and see if you can hunt down some of them!  A star chart to help you find the Summer Triangle and identify some of the nebulas contained within it is available below, under last week's post.

If you are up early on the morning of Friday 31st May, say around 4am before dawn and look towards the south east, you will be greeted by a 45%-lit waning crescent Moon with planet Saturn a little to the left of it.

During the summer months, astronomers enjoy looking at an area of the night sky known as the "Summer Triangle" which is formed between the stars Deneb in the constellation of Cygnus, Vega in Lyra and Altair in Aquila.  Currently, if you are outside around 11pm, the Summer Triangle will have risen above the horizon to the east.

Why do astronomers get so excited about it?  Well firstly, you will notice a patch of faint cloud running across the triangle - it's not really cloud, rather the centre of our Milky way galaxy and you are seeing the light from millions of stars in the distance.

The Summer Triangle is the location of many deep sky targets for your telescope, for example the Dumbbell Nebula M27 and Ring Nebula M57, so named because of their obvious shapes.  There are also objects that do not appear in the Charles Messier Catalogue; instead they are listed in the New General Catalogue.  You could try to spot NGC7000 which is known as the North America Nebula because it looks like the outline of the USA with the Pelican Nebula beside it.  See if you can make out the shape of the pelican.

Finally, near the middle of the triangle is the black hole Cygnus X1, but you won't see that because no light can escape from it.  You would need an X-Ray telescope to detect it!

I'm going to concentrate on the early hours of Friday 24th when we have a full Moon.  By 1am, the Moon will be heading towards the south and if you are outside at that time, the bright star Antares will be located a little to the left of the Moon.

Antares is a red supergiant and it is actually classed as a "variable star".  This means that its magnitude or brightness can change between +0.6 at its brightest, down to around +1.6 and I believe that currently it is around +1.0 so very easy to spot.  Antares is part of a binary star system, but you will only be able to resolve the main red supergiant star - its smaller companion will remain invisible.  Antares is huge - up to 16 times the mass of our Sun and if it was placed at the centre of our Solar System, the star would extend all the way out to Jupiter!

Binary stars orbit around each other because of their mutual gravity and if you can see both stars in your telescope, they are known as "visual binaries".

Getting back to 1am on 24th, immediately to the left of the Moon you can find the Spider Globular Cluster of stars, also known as M4 in the Charles Messier catalogue.  It will be a real challenge to see with your telescope because of the proximity of the full Moon which is the ultimate source of light pollution.

Globular clusters are collections of up to millions of stars, kept together by their mutual gravity and the centre of the cluster is brighter where they are concentrated.  Last week I suggested looking at M44 which is an open cluster - a small group of recently-born stars who gradually drift apart from each other.

If you are outside around 1am on the morning of Tuesday 14th, a 35%-lit waxing crescent Moon will be setting towards the western horizon.  Just below and to the left of the Moon you will find a nice target for your telescope that I have mentioned before - the Beehive open cluster of stars, also known as M44 in the Charles Messier catalogue.

It's also a week for spotting those curious clair-obscur visual effects on the lunar surface, starting with the "Lunar X and V" around 4pm on Wednesday 15th.  The Moon will have risen about the horizon towards the east and even though it will be daylight, the moon should be visible, with the "X and V" on the terminator, where sunlight just illuminates the lunar surface.

Early Friday morning 17th, around 2am, is the optimum time to observe the clair-obscur effect known as "Plato's Hook" in the crater Plato.  A slightly gibbous Moon will be setting towards the west.

Finally, May is the start of the noctilucent cloud season.  These night-shining clouds are caused by sunlight reflecting off water ice crystals in the upper atmosphere at twilight.  They are too faint to be observed in daylight.

I am just going to concentrate on one observing opportunity this time - before dawn on Monday 6th could be a very rewarding time to make an early start!  The constellation of Aquarius will just be rising above the east south east horizon from 4am and we have the peak of the Eta Aquariid meteor shower.  Just below the radiant point of the shower, Saturn will be poking its head up above the horizon if you have an unobstructed view in that direction.

At 4.17am, if you turn your gaze towards the west, the International Space Station should appear.  It will look like a bright star that is moving silently and the ISS will pass almost directly overhead, before disappearing 7 minutes later in the vicinity of the meteor shower's radiant point.  How cool is that!

Saturn will have a magnitude of around +1.07 so should be fairly easy to spot.  The ISS at that point will have a magnitude of approximately -1.31 or in other words, you won't be able to miss it!

If you delay heading back indoors for breakfast, Mars will then pop up above the eastern horizon and from around 5am, a very thin crescent Moon makes an appearance in the same direction.

Although Mars will have a magnitude around +1.2 it will be much harder to spot against the dawn sky.  The Sun will be rising shortly afterwards, which prompts me to give my usual warning about not taking the risk of using your telescope or binoculars, in case you accidentally catch a glimpse of it in the eyepiece.

First of all, something for the early risers!  From 4.30am on the morning of Wednesday 1st May, a quarter Moon will be just rising above the south east horizon.  This is an optimum time to observe one of the lesser-known clair-obscur visual effects on the lunar surface called "The Cutlass" because of its obvious sword-like shape.

At 2am on the morning of Friday 3rd, the famous "Globular Cluster in Hercules" reaches its highest point in the sky - this is the best time to observe the cluster as light from its hundreds of thousands of stars will be passing through less of our atmosphere.  Remember it is distortion created by our atmosphere that makes stars appear to twinkle and so the higher the angle, the better.

The constellation of Hercules will be located high in the sky towards the south east and the cluster, also known as M13 in the Charles Messier Catalogue can be found roughly halfway between the bright stars Vega in Lyra and Arcturus in Bootes. It is just to the right of the asterism (or shape) referred to as "The Keystone" in Hercules.

Finally, there are a couple of excellent opportunities to spot the International Space Station during the coming week; Tuesday 30th April at 4.24am and Friday 3rd May at 3.35am.  In both cases, the ISS will appear towards the west and pass almost directly overhead.