Download an evening`s viewing with your new `scope

AN EVENING’S VIEWING WITH YOUR NEW ‘SCOPE
By Professor Paul T.Curtis
So you’ve been along to our telescope evening, talked with some of our experienced amateurs,
read the articles and then you’ve bought a shiny new telescope. So what next, where do you
start ?? Most amateurs will look at the moon first, assuming it is visible, and the moon really will
look impressive in any telescope. Concentrate on the terminator, where the shadows are
longest, and see what you can see. Use a moon map if you have one – the popular star atlases
usually have reasonable maps (Norton’s Star Atlas and the Cambridge Star Atlas by Tirion are
well worth considering) or I can recommend the fold-out moon map by Phillips which has a
wealth of detail.
Some amateurs spend all their lives studying the moon, but most will want to move on or
perhaps the moon is not visible. Unfortunately there are no planets visible at the moment; we
must wait until the summer for Jupiter. Other targets worth looking at are the well-known major
astronomical objects. Try the Pleaides in Taurus and the Orion Nebula if you can catch them
before they set. Another object worth a first look is the beehive cluster (M44) in Cancer. Use
one of the star atlases to navigate, but all these objects are easily visible by eye so require only
a minimal knowledge of the sky.
But after this, where do you go ?? Most amateurs eventually focus on one type of object, such
as double stars, variable stars, planets etc. My own personal interest, as those of you who
came to my lunchtime talk will know, are deep sky objects. But I don’t only look at these and
certainly at first you should try at look at all types of objects.
Most amateurs will have some sort of plan of what they want to look at during a night’s viewing.
Indeed part of the fun is thumbing through star atlases and making a list and a viewing order.
So in this article I give you a good first viewing evening with your new ‘scope, covering a range
of easy bright objects, which will give you a taste of real amateur astronomy. I hope you enjoy it
– give it a try – and good luck !!
Start by identifying the Plough, which is close to overhead right now. Look for the three stars in
the handle and point your ‘scope at the middle of the three stars, zeta Ursa Major or Mizar. Use
your star atlas to help. Look closely by eye at first – can you see more than one star ?? This
star is actually a wide double star with the second star, Alcor, visible close by if you have good
eyesight. Alcor is about 12 minutes of arc (12’) away from Mizar, just under ¼°, which is
actually a quarter of a light year at the distance of the stars themselves. Alcor is a little fainter
than Mizar (magnitudes 2.1 and 4). Now look through the ‘scope using a low magnification and
you should clearly see the widely spaced stars. However, look closely and you should see that
Mizar has a much closer companion star, also magnitude 4 (and thus quite bright) but only 14”
(seconds of arc) away. You should be able to see this clearly, but if you have trouble then try
using a medium magnification (50-100x) which will separate the stars better and make them a
little clearer. Actually Mizar is also a spectroscopic binary, that is a double star so close that it
can only be detected by separating the two different star spectra. They are about 18 million
miles apart, about a fifth of the earth-sun distance, so very close on astronomical scales. So
you are looking at a possible quadruple system although Alcor may not be physically linked to
Mizar. This multiple star system is 88 light years away, so you are looking at light that left the
stars before any of us were born !!
From your first double star let’s try for a deep sky object. The closest of any note is the famous
Whirlpool Galaxy, M51 in Messier’s catalogue. Move the scope to the left hand star of the
Plough’s Handle (eta) them use your star map to guide the telescope down at right angles to a
line between eta and Mizar for about half the distance between the two stars. Make sure you
have your lowest magnfication eyepiece in. Try to make sure your eyes are dark adapted by
avoiding any white lights for at least 15 minutes, preferably 30, before you try this. Look
carefully through the eyepiece – if you cannot see anything then nudge the scope side to side
and up and down and check you position again. If this doesn’t work, use the star map and ‘star
hop’ (see April’s Astronomy Now for information on this technique) to get yourself to the right
area. Look closely; try looking to one side as your eyes are
M51, 5 min exposure, Farnborough
least sensitive to dark (most cones and least rods) straight
on, so you can see fainter objects off axis. You should see a
faint fuzzy blob, M51, which is one of the most impressive
spiral galaxies, some 30 million light years away. You won’t
see it as a spiral – you need at least a 10” scope and a
trained eye to see this. This galaxy was the first to be
recognised as having a spiral pattern, by Lord Rosse in
Ireland in 1845. Early astronomers thought they were looking
at ‘solar systems’ in the early stages of planetary formation
and it wasn’t until 1923 that their true nature as external
galaxies emerged.
M51 actually isn’t one of the brightest deep sky objects so don’t be disheartened if you cannot
see it – come back another time. Let’s move on to another deep sky object, this time much
brighter. Again use your star atlas and star hop a short distance to M63. Same advice again –
make sure it is dark and your eyes are dark adapted. M63 is a bright tight spiral, which you
should see easily as a bright fuzzy blob. It is slightly elliptical in shape, photographic size 15’ by
9’ but you will see about half this.
We have moved from the constellation of Ursa Major into the constellation of Canes Venatici
(the Hunting Dogs). Now move across to the star Cor Caroli, or alpha Canes Venatici. This is a
bright double star, whose components are magnitude 2.9 and 5.5 and separated by 19”, slightly
wider than Mizar and is a nice easy double star even at low power. Try a higher magnification
and see if that improves your visibility. The stars are a true binary separated by about 770
earth-sun units (called astronomical units). They lie about 120 light years away.
From Cor Caroli move a larger distance to the object M3, which is due south about the same
distance as Cor Caroli is from eta Ursa Major. This is a bright object and should be easy to see.
It is a good example of a large bright globular cluster. It is about 10’ in diameter and being so
bright can stand higher magnification, so try stepping up to 100x or more. Can you start to
resolve the stars at the edge of the cluster ?? The books suggest that a 4” scope on a good
night will do this. M3 lies about 40000 light years away and is 220 light years across with in
excess of 45000 stars.
M94, 3 min exposure, Farnborough
Now jump back to Cor Caroli – you can probably do this by
manually moving the scope rather than star hopping, as
you can probably spot the star by eye now. Then use the
map to move a little north to the object M94. This is
another very bright object, an elongated spiral about 11’ by
9’ (again you will see about half this size). It will appear as
a fuzzy blob with a very bright, almost stellar, core. You
really can’t miss this one !! It lies about 20 million light
years away !
Now hop onto beta Canes Venatici, which is nothing
special, then star hop to M106 to the North. This is another very bright elongated spiral, easy to
spot, and a whopping 20’ x 7’ in size. This really does look like a galaxy, even in a small ‘scope,
although you won’t see the spiral structure.
Well that’s probably taken you a good evening to get around. If you want to try some other
objects close by then take a look at M64 to the south, M109 to the north and the Coma
Berenices cluster to the south.
Good luck and I hope you enjoy this planned evening of viewing.