The Night Sky in October, 2017

This month I have received an email from Peter Martinson who regularly reads this Newsletter. If

any of you are thinking about buying a telescope then you may find his comments useful:

“Thanks for your regular newsletter. I also wanted to thank you for your advice in helping me

choose my astronomy equipment. I finally got round to buying a telescope and binoculars this

summer and I'm having great fun even with the light-polluted and restricted view from our back

garden.

I went with your recommendation and bought the Startravel 120 refractor with AZ4 mount and

tripod from First Light Optics and got some decent carry cases and a few other items that FLO

didn't have from Rother Valley Optics, who were also very helpful with a fast and convenient

delivery service. I'd seen a few favourable web reviews of this telescope where people had

described it as a good "grab & go" scope, which is what I was after. The AZ4 mount/tripod is also

sturdy (I got the one with stainless steel legs although it seems they also make one with aluminium

legs, which would have been a bit lighter). One thing worth noting about the AZ4 though is that

the azimuth scale seems to be calibrated upside down, e.g. when the telescope is pointing East it

reads 270, and West is 90, so you have to do some mental arithmetic and interpret indicated

azimuth angles as (360 minus angle). A quick Google seems to suggest I am not alone and

someone commented that the mounts are manufactured for use in the southern hemisphere. I

don't know if that's true. Anyway, it's not a problem, just seems a bit odd.

I'm gradually learning my way around the night sky. The first evening I went out, I realised

afterwards I must have seen the space shuttle so checked the Web for timings and we both looked

out for it the following evening. That was a pleasant introduction to watching the night sky. After

pointing the telescope at a few bright objects (Arcturus and Vega) I used the Plough to point me

in the direction of Polaris (I knew I must have got the right object because I didn't have to keep

nudging the telescope). I also pointed it at Capella, which intrigued me because of its many

colours. I later found out that the colourful twinkling is caused by our atmosphere when it's at a

low angle.

Years ago, Lesley bought me a copy of the Collins Pocket Guide to Stars and Planets, which I'd

never really looked at as I couldn't figure out the charts. However, now with a real interest to

focus on and real night sky to work with I have found it to be an invaluable companion. I found

the Summer Triangle and hence Deneb and Cygnus and the book's write up spurred me on to

look more closely at the pair in Cygnus that makes up Albireo, which the telescope resolved very

well. I like to try and familiarise myself with a constellation and its components and learn to

navigate around in this way, so I'm glad you recommended not getting a Goto mount to begin

with.”

Many thanks Peter! It always lifts my spirits when I hear that someone has taken up astronomy and

are happy with the things I have recommended. Don’t forget all of you out there, please contact me

if there is something you would like to share with other readers of this Newsletter.

Before I move on, you might like to see this image taken by Joel Kowsky of NASA. It is a

composite image showing the International Space Station crossing the surface of the sun at the time

of the partial phase of the eclipse! It is travelling at 5 miles/second and has six people on board!

Now on to the October sky. At the beginning of the month, the Sun will rise at 07:11 BST and set at

18:46 BST. By the end of the month it will rise at 07:07 GMT and set at 16:39 GMT. There will be a

New Moon on October 19th and a Full Moon on October 5th, so the middle and end of the month

will be the best for stargazing.

The star chart above shows the sky high in South above Oxfordshire at 23:00 on October 19th. In the

centre you can see the constellation of Pisces the Fish with the head of the fish (the circlet) clearly

visible. You can find the planet Uranus in this part of the sky. It is at opposition on this date which

means that it is at its best and is visible all night. You need a small telescope to see its blue/green

disc and a 12inch scope or larger to get a good image of it. Above the circlet is the Great Square of

Pegasus and above that is the Andromeda Galaxy, M31. To find M31, first find the star Alpheratz

at the top left of the square of Pegasus. You can see two lines of stars leading out to the left from

this. This is the constellation of Andromeda. With binoculars or a telescope scan along the bottom

line until you find the bright star Mirach. Scan up from this to the star above it on the top line of

Andromeda and then go up the same distance again. There you will find the Andromeda galaxy.

Above it is M110 and below it is M32. Note that these will be the opposite way around through a

telescope as shown in the image below. M110 is at the bottom right and M32 at the top left of

Andromeda. These are both dwarf elliptical galaxies and approximately 2.6 million light years away.

Note that the letter “M” means that these objects are in the Messier catalogue.

In the bottom right of the star chart above you can see the planet Neptune in the constellation of

Aquarius. It is well positioned high in the sky but you need a telescope and a magnification of about

150x to see its bluish disc. In the far left of the chart you can see the beautiful open cluster of stars

called the Pleiades (or the Seven Sisters), M45. Saturn can still be seen low in the southwest. On

October 24th there will be a slender crescent Moon just above it which will make a beautiful sight.

Venus and Mars are both morning objects and in the star chart above, can be seen rising in the east

at 05:30 on October 1st. They are in the constellation of Leo the Lion. They will gradually move

closer together until on October 5th and 6th they will appear to be touching (only 22 arcseconds

apart). Then on October 7th Mars will be above Venus and on October 17th there will be a lovely

grouping in the east at around 05:30 of a thin crescent Moon with Mars and Venus as can be seen in

the star chart below.

One of the big events in October is always the appearance of the Orionid meteor shower. This will

peak between October 21st and 23rd just after the New Moon which is ideal if the sky is clear. The

star chart below shows Orion rising in the east at 23:30 on October 22nd. Meteor showers occur when

particles of dust left behind by comets enter the Earth’s atmosphere. The dust particles burn up

giving a streak of light. The Orionids are caused by the dust left behind by Halley’s comet. Meteors

can be seen all over the sky but if you trace them back they all seem to originate from the same point

in the sky. This is known as the radiant and is very close to the star Betelgeuse in Orion for this

meteor shower. This is the reason the shower is called the Orionids.

October is the month when astronomers start to think about deep sky observing during the dark

nights. This involves looking for faint but distant objects some of which are distant galaxies outside

our Milky Way. I must admit I still get a buzz when I find a distant galaxy which is millions of light

years away! You can do some deep sky observing with a powerful pair of binoculars such as the

Celestron 15x70 bins I recommended a few months ago. But you will be able to find more distant

objects with a telescope. You need completely dark skies and allow yourself 30 minutes to get

yourself dark adapted. Then use only red lights which won’t spoil your night vision.

I will write about deep sky objects in later Newsletters throughout the winter. But this month I would

like to finish by describing the naming of objects in the sky. When you look at a star chart such as

the one above, you are often faced with a bewildering array of names and labels. The International

Astronomical Union (IAU) is the only body allowed to name objects in the night sky. But often they

take over names already given.

All the bright stars you can see in our sky are part of our own Milky Way galaxy. Many of these

were named by the Arabs and these names have been retained. This is particularly true of any star

name beginning with “Al” such as Alnitak and Alnilam in Orion’s belt or Aldebaran in Taurus and

Alpheratz in Pegasus. Many of the constellations were named by the Greeks and represent figures in

their mythology such as Orion, Gemini and Taurus. The IAU has retained these names but has

defined a total of 88 constellations including those in both the northern and southern hemispheres.

Many of the bright stars in a constellation are given a name but they are also named alphabetically

depending on their brightness. Greek letters are used – that is “alpha, beta, gamma, delta” rather than

“a,b,c,d”. The brightest star in a constellation is labelled alpha (α), the next brightest is beta (β) and

so on. In Orion, Betelgeuse is α Orionis, Rigel is β Orionis and Bellatrix is γ Orionis. Numbers are

assigned to the less bright stars. For example, one small star near Betelgeuse is called 52 Orionis.

Then there is a bewildering array of star catalogues often named after the person who developed

them. The most famous is the Messier catalogue which contains 109 objects. These are either

galaxies, star clusters or clouds of gas called planetary nebulae. The catalogue was developed by the

18th century French astronomer Charles Messier. The names in the catalogue all begin with M such

as the Andromeda galaxy M31. Patrick Moore produced a supplement to the Messier catalogue

called the Caldwell catalogue also containing 109 objects. These all begin with C after Patrick’s

middle name Caldwell. Patrick could see further south than Messier and so included more objects in

the southern sky. It is interesting to see the Messier and Caldwell catalogues side by side as shown

below. The Messier catalogue is on the left and Caldwell catalogue is on the right.

I also find the following chart fascinating. Patrick named his objects in order from north to south. So

C1 is the most northerly object and C109 the most southerly. As ever, thank you Sir Patrick

Caldwell Moore!

Objects beginning with NGC are included in the New General Catalogue produced in 1888 by

John Dreyer so it is not exactly new (like the New Forest)! It is one of the largest and most

comprehensive catalogues and contains 7,840 deep sky objects whose names all begin with NGC. It

is an extension of John Herschel’s original General Catalogue. Dreyer produced an extension to his

NGC catalogue in 1895 and another in 1908. He called these the Index Catalogues and they contain

an additional 5,386 objects whose names all begin with IC (sorry Ian Calderbank, these are not

named after you)!

Almost all Messier objects have NGC numbers as well. For example, the Andromeda galaxy, M31 is

also NGC 224 There are many, many more catalogues but this is enough for one Newsletter! I will

introduce some more in the following months.

Now to the Southern hemisphere!

What's Up in the Southern Hemisphere?

Uranus and Neptune are very favourably placed for you to observe this month. The star chart below

shows the sky high in the north over Sydney at 23:00 on October 23rd. In the centre of the chart you

can see Uranus in the constellation of Pisces the Fish. The head of the fish (the circlet) can be seen

on the left. Above the circlet is the planet Neptune in the constellation of Aquarius. Below the

circlet you can see the Great Square of Pegasus and the Andromeda galaxy can just be seen at the

bottom of the chart.

In the next star chart, you can see the sky in the east at 00:30 on October 23rd. Orion has risen in the

east and is quite favourably placed for you to see the Orionids. The radiant is near to the star

Betelegeuse which for you is at the bottom right of Orion. To the left of Orion, you can see the

constellation of Taurus the Bull with the Pleiades to the left of it. On the right of the chart is

Orion’s large hunting dog, Canis Major, with the dog star Sirius shining brightly.

Saturn is still well placed for observation for you particularly at the beginning of the month when

you will have a three-hour observing window before it sets. The star chart below shows the sky high

in the west at 21-00 on October 1st. There you can see Saturn beautifully placed in the constellation

of Ophiuchus close to the Messier objects in the constellation of Sagittarius! To the left you can

see the constellation of Scorpius in all its glory! There are excellent imaging possibilities in this part

of the sky.

Venus and Mars are not well placed for you this month since they are very close to the eastern

horizon in the morning just before sunrise. You may catch a glimpse of Jupiter and possible

Mercury in the west just after sunset at the start of the month.

Well that is all until next month. Meanwhile happy stargazing! Dark skies!

Valerie Calderbank FRAS