Astronomy for Non-Astronomers
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Answers to some frequently asked questions and topics, for
people who are curious about astronomy but not astronomers themselves.
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If you're referring to the big red telescope that looks
like a cannon, then yes, I did build it. You can read more
about it at my Telescope Making Page.
Well, city lights wash out a lot of what you can see with a telescope.
That's why we drive outside the city to dark skies on weekends, near
the new moon phase when the skies are darkest.
Within the city, nearly all the planets are visible except Pluto,
which is very dim. Mercury, Venus, Mars, Jupiter and Saturn are
all visible with the naked eye. Uranus can be found with binoculars,
and Neptune can be found with a telescope. I have also seen some
of the brighter asteroids from the city, as well.
Some of the brighter deep sky objects are visible. For instance,
M42, the Great Orion Nebula,
the M13 Globular Cluster in Hercules,
the M31 Andromeda Galaxy,
and the M57 Ring Nebula in Lyra have all been
seen from my front sidewalk in San Francisco. Other objects such
as double stars are also visible. Sometimes the hard part is
navigating the scope to these objects, since you can't see enough
stars in the sky to orient yourself!
Finally, the Moon is always easy to
see when it's up, and makes a great target in almost any telescope.
Magnfication isn't the most important thing that a telescope
does. In fact, you might be surprised to discover that experienced
amateurs don't consider magnification very much when they shop for
a new telescope.
There are two reasons for this:
The magnification is changeable. All telescopes use
removable, interchangeable eyepieces. By removing one eyepiece
and inserting another, I can get any magnification I want. I
can use a low magnification eyepiece for star clusters
like the Pleiades, or a high magnification eyepiece in order
to view subtle details on the planets or the Moon. So you can get
just about any magnfication you want on any telescope. Whether
or not high magnfication is usable on a given
telescope is another story.
The most important determining factor for a scope's resolving power
is its aperture, or the diameter of its main optical element (called the primary). Depending on the type of
telescope, this is either a lens or a mirror.
The larger a telescope's aperture, the more
light it collects, and the more detail it can show. High magnfication
with a small (low-aperture) telescope can often present a blurred image
with no visible detail. That is because the high-magnification eyepiece
simply magnifies a mushy image from the main telescope optics. The
primary optics aren't big enough to resolve a more detailed view.
Professional telescopes are
huge, elaborate constructs permanently mounted in big observatories. In the
world of telescopes, bigger is better!
If you want to know more about telescopes, please visit my
Beginner's Page.
The answer is, "it depends". It depends a lot on the darkness of the
sky, and also the size of the telescope you use. The bigger the scope,
the fainter and farther you can see (see the previous question).
One object that is observable in many amateur telescopes is the
quasar 3c273.
This is the first quasar discovered, in 1963. It is the brightest quasar in
the sky, but even so, it's about two billion light years away. One light year
is about six trillion miles. So, the light you're seeing from 3c273 is
2 billion times 6 trillion miles...that's pretty far away.
Closer to home, within our own solar system
Pluto (roughly 4 billion
miles away) can be viewed with an eight-inch telescope or larger
(that's a scope whose primary lens or mirror is at least eight inches in
diameter). I've observed Pluto with my big, red homebuilt
scope.
As explained elsewhere in this FAQ, the finest details a telescope can reveal are limited by the size of its primary optical element. The larger it is, the fainter
it can see and the finer the details it can resolve. Here on Earth's surface, we also have to deal with the effects of Earth's atmosphere, which distorts and blurs images, reducing detail.
The best and largest telescopes in existence are not powerful enough to resolve details as small as the Apollo moon landers. The Hubble Space Telescope is only capable of resolving details as small as 85 meters (280 feet) on the lunar surface. On Earth, even the largest professional telescopes under the best atmospheric conditions can only resolve lunar features down to about 1 kilometer (0.6 mile) in size.
To directly see the Apollo landers from Earth, we would need to have a telescope with a primary optical element exceeding 100 meters in size. And it would need to be in Earth's orbit, above our atmosphere.
Thanks to Sky and Telescope magazine for this information, which I have adapted from their October 2004 issue.
There are three methods we use:
- Star Hopping. You start with a star chart, either on paper
or on a computer screen. It plots many
more stars and objects than you can see with your naked eye. But the brightest
stars on the chart are naked-eye objects. So you pick a bright star that's
near the object you want to find, and center the scope on it - an easy task. Then
you look through the scope (or a smaller finderscope), compare the stars
you see against the chart, and nudge the scope until you reach your goal. This
is the lowest-tech approach. It takes a little work to get the hang of it, but
is blissfully simple and enjoyable once mastered.
- Setting Circles. Some telescopes have graduated rings (analog)
or a digital display indicating where they point in the sky. Every celestial object
has coordinates in right ascension and declination - like latitude
and longitude, only for the sky. You look up the coordinates on a chart or in
a book, then adjust the telescope until its indicators match up.
- Computerized Pointing. Several telescopes have built-in computers,
containing a database of coordinates for tens of thousands of objects. You
simply key in the name or designation of the desired object on the keypad,
and the telescope finds it for you. This is the most convenient and fastest
approach, but not all telescopes are equipped with computers. And like
anything involving computers, it can be cryptic and flaky at times. Scopes
that incorporate this technology are commonly called Go-To telescopes.
Most astronomers use either star-hopping or go-to computerized
pointing to aim their scope. Some folks use digital setting
circles, and hardly anyone uses analog setting circles (graduated rings)
to find objects anymore.
If you want a free all-sky star map for learning the constellations for
the current month, check out Skymaps.com.
The Abrams Planetarium at Michigan State University also publishes a
Monthly Sky Calendar with
a star chart, and a listing of interesting things you can see with the naked eye.
No telescope is required, though sometimes a pair of binoculars is useful.
You can purchase a monthly subscription for a very modest fee.
Also, check out my Software and Tools page
for more sky charts and computer software to show you the constellations.
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The Nine Planets is an excellent website that will tell you
everything you want to know about the Solar System.
Photo: James Mace
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I am deeply sorry to tell you that your
money has done nothing except line the pockets of a company that
has given you an empty promise.
You may have heard or seen ads from companies that will offer to
name a star on your behalf for a fee. They will send you a certificate
and a chart to make you think you actually named a star. In reality,
none of these companies are authorized to name stars.
They are simply taking your money. I hear the ads for these services
on a local newsradio station — often while taking my telescope
out for an evening observing session — and I'm concerned that by
running this kind of scam, they give astronomy a bad reputation.
No amateur or professional astronomer ever wants to break this news
to you personally. We don't enjoy telling you the sad truth directly,
because we know that you love your relative or pet deeply, and believe
this gesture on your part is the best way you could honor them or
the deepest gift you can give. But that doesn't stop other, less
scrupulous people from capitalizing on your feelings of affection
and devotion in order to simply take your money.
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No. Next question.
Okay, you're still curious. No, I have never observed anything
that I could not identify. Part of the reason is that I'm an
experienced observer. I've seen the Milky Way, planets,
artificial satellites, the International Space Station, the
Space Shuttle, and all manner of things in the sky. I know what
they look like, and I know where to look to find them. So very
little, if anything, of what I see in the sky surprises me. None
of the other amateur astronomers I know have reported seeing UFOs,
either.
Amateur astronomers like to look in the sky so much that
we've seen nearly all the things that people mistake for UFOs.
For instance, many people mistake Venus for a UFO. It's very,
very bright, and it seems to "follow" you around in the sky when
you move. It's an optical illusion of course, but its enough to
fool people. I (and other amateur astronomers)
just look at it and say "that's Venus, how lovely."
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Another example of mistaken UFOs are
Iridium flares. Iridium is
a group of 88 earth-orbiting satellites that are part of a failed
worldwide cellphone network (it's now owned and operated by the
US Department of Defense). No matter where you are on Earth,
every now and then one of the satellites will catch a glint of
sun - and you will see what looks like an incredibly bright star
that moves across the sky, lasts for maybe thirty seconds, then
mysteriously fades away. Lots of amateurs search out these flares (and
you can too). But
someone who is not aware of these flares can easily mistake
one for a UFO.
Do I believe in life on other planets or stars? There's so many
stars out there, and planets around stars have been proven to be
pretty common. So I believe that there's other life in
the universe. But no, I don't believe the aliens have found
us yet. Carl Sagan was quoted as saying "Extraordinary
claims require extraordinary evidence." Aliens from other
worlds are pretty extraordinary; and we just don't have the
extraordinary evidence to prove they're here.
No. Next question.
Okay, it might be fun to look at the newspaper horoscope, but astrology
truly has nothing to bear on our lives.
For one thing, astrology is based on science and stellar alignments from thousands of years
ago. For instance, the dates the Sun is currently in a given constellation
do not line up with the astrological dates of the constellation. Astrology is based on 12 constellations in the Zodiac, when in fact
there are anywhere between 13 and 24 constellations, depending on
your definition of the Zodiac.
The original
astrologers didn't even know Uranus, Neptune, and Pluto existed. How
could they have made accurate forecasts? Astronomers are discovering
new worlds in the outer solar system every day. In fact, as I write
this (March 2004), just last week a new world (Sedna) was discovered in
the outer solar system. How does this affect astrological forecasts?
What about the planets we are discovering, and continue to discover,
around other stars? Do they affect astrology, and how?
What about all the astrology forecasts that have been done up to
this point? Are they all wrong in the face of these new discoveries?
Finally, there's no evidence that any
alignment of the planets or the Sun has an effect on events on
Earth. This has been verified in scientific studies.
For a more detailed, common-sense argument, see
Your Astrology Defense Kit
by Andrew Fraknoi.
I've been asked this question, and I consider it a very personal
(and invasive) one. But here's my answer:
Science, including the astronomers, astrophysicists, and cosmologists,
has not been able to prove God's existence. Nor has it been able to
disprove God's existence. Nor is it likely to ever do so.
Given that science cannot answer the question of God's existence
one way or the other, it really comes down to a matter of Faith.
Do you believe in God? What I believe doesn't really
matter. But I certainly agree with
John Dobson when he says,
"The Exterior Decorator does good work!"
Copyright © 2004 Michael Portuesi. This work is licensed under a Creative Commons License.
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