Practical Astronomy Primer
Know Your Constellations
Equipment
A red light ; a star chart or map ; a pair of glasses ( if you need them ) ; a
deck chair ; warm clothes ( even Summer nights can get cold ) including a scarf,
cotton gloves and moon boots. Take a drink with you and maybe a snack, which
will give you energy and may help to keep up body temperature.
Summer
This is a good time to pick up your hobby, because the nights may not be too
cold. However, it doesn't get dark until later, by which time you may feel more
like bed, than setting up your kit outside for a session ! Locate Cassiopeia ( a
bright W not far from Polaris, the north pole star ). Then locate the Summer
Triangle ( large bright triangle formed by Vega, Deneb and Altair ). These stars
belong to Lyra, Cygnus and Aquila respectively. Back to Cassiopeia ; Andromeda
is next to it and leads you to the square of Pegasus which leads you back to
Cygnus and to the right of Cygnus, Hercules. The great bear is a well know
constellation, and the pointers will lead you to polaris in the little bear. Use
the little bear ( Ursa Minor ) to get an idea of your limiting magnitude. If you
can see all the stars in Ursa Minor, you're doing quite well. Get familiar with
these brighter constellations, before filling in the gaps with The dolphin,
Cepheus, Lacerta ( a bit faint ), and Sagitta. You don't need to cover the whole
sky in one session, so practice one or two constellations at a time, first
referring to the chart, then by heart. Try and identify the bright stars. If you
can point out Alpha Andromeda, or the Andromeda nebula quite quickly you are
doing well. If you still don't know what these are, then you've still got a long
way to go. Resist the temptation to look through binoculars or a telescope at
this stage, because you will be swamped and overloaded with a huge quantity of
stars.
Meteor showers
On certain nights, usually the same time each year, meteors can be seen
radiating from a particular point of origin in the sky. Typically one a minute
may be seen, but even without a shower, one may expect to see a shooting star
once every 10 - 15 minutes. These sporadic meteors may last less then a second.
Indeed if you catch one out of the corner of your eye, you may think you
imagined it, until that lucky moment when one passes right where you happen to
be looking, and you know for certain what you saw.
Binoculars
Fuzzies
If you think you know your night sky, then you can start looking for deep sky
object, otherwise know as "fuzzies" such as M13, M31, the Pleiades or
M42. You will need 10x50 Binoculars for these object, and you can usually expect
to see a fuzzy ball when you finally locate your objective ! Be patient, for
first timers may completely miss their target. Forget that subtle colour
photograph you have in mind of that fabulous whirling galaxy, Andromeda, and
look for a faint fuzzy patch in the sky. Colours will not show up, but the
chances are you are going to be seeing a few objects such as Galaxies and
Clusters that you have never seen in your life.
Planets
You will not see the Rings of Saturn in Binoculars, but you may see Titan, its
largest moon, and you will certainly see all 4 of Jupiter's Galilean moons if
they are visible. One or more may be in transit, or too close to the planet for
it to show up. You will know you are looking at moons of Jupiter, because they
will all appear in a line, or in the same plain, fairly close to the planet. You
can also spot Uranus with binoculars, but you will probably need a good software
planetarium program on your PC and an accurate print out of the area of the sky
involved. Mars will be in opposition around the middle of June 2001. Venus can
be a very bright morning or evening star ( brighter than everything except the
Moon and the Sun ). Binoculars would also be useful for spotting Mercury, a
Planet I have never seen ! I know Mercury will not show up as a large feature
filled disk in my telescope when I finally track it down, but the main thrill
will be seeing it, after having located it for the first time ever. As with
Venus, the main characteristic to note in Mercury will be its phase ( Just like
the Moon has phases ).
Doubles, Variables and Coloured stars.
This is one last category of observation to look out for. Some stars have a
companion star, or even several companion stars in their system. Some stars vary
in brightness, ( one reason being they may be eclipsed by a fainter star in
orbit ) and these changes in magnitude can be noted over a long period of time
by comparing their brightness to the stars around them. Red giants actually have
a reddish colour to them. Also blue, orange and yellow stars give distinct hues,
especially if the conditions are good.
Telescope Sessions
Setting up
You will need all your equipment including lenses and binoculars ( to scout out
the area you are going to zoom in on ). I have a 10x50 finder scope on my 10
inch reflector, and I also have a 10x50 pair of binoculars. These give me about
the same field of vision as the finder scope, so I know what I will see through
the finder, and therefore recognize the area in question more readily. You need
to align your equatorial mount ( this does not have to be accurate for the first
few sessions ). You also need to get comfortable, and you need another chair or
plastic sheet on which to lay out all your charts and maps and torches and
you-name-it without them getting wet or dirty.
Dew
As Autumn sets in, watch out for dew. If your scope gets colder than the
surrounding air ( typically after a couple of hours ) you either need a
secondary mirror heater ( the primary may stay out of trouble ) or you need to
pack up, because the dew is too severe to put up with. Test the conditions first
by spending 20 minutes or so with your binoculars. If they are affected by dew,
consider giving your telescope session a miss, unless you are happy with a quick
half hour session before the dew sets in. Beware that your scope will not have
cooled down enough in just half an hour, and will suffer some distortion from
rising heat waves.
Observing
When you have seen the brightest and most obvious objects, like the Moon,
Jupiter, Saturn and maybe Mars, you should turn to the so called deep sky
objects ( ever heard of the Messier Catalogue ? ) , then to doubles and
variables. Star hopping is a useful technique to learn, with a good sky chart. Plan your
observing time before hand. Don't make a long list, just 2 or 3 objects will be
enough. When you're finally tracking Jupiter or M42 with the right lens, don't just say
oooh aaah, but get a sketch pad out and pencil and start drawing what you see.
Note down what eyepiece you are using, and what the time was at the middle of
your sketching time. You might also note down the seeing conditions and what
your limiting magnitude is.
Pack Up
When you've had enough, pack up. Lie the scope indoors on its side for the dust
not to settle on the main mirror. Leave the dust caps off for the night for the
scope to adjust to indoor conditions. Put things away, and next day look up what
you were observing in an Astronomy book. Having seen an object "live"
will help you to relate to it and remember it more easily. Keep your records of
your observations tidy, and refer to them when you next need them. You are now
ready to show off some sights to your friends and family !
