-- Welcome to the University of New Hampshire Observatory Webpage --
UNH Observatory FAQs
- How powerful is this telescope?
-
Well, that's actually a more complicated question than one
might expect. Many people, when they ask this question, want
to know how many times an image is magnified when you view it
through the telescope, as compared to when you view it with
your naked eye. If this is what you're interested in, the
magnification ranges from 122.2 x with our 32mm eyepiece, to
54.8 x with our 72 mm eyepiece.
For astronomers, however, magnification is less important
than light gathering power. The more light a telescope can
gather, the fainter the objects that one can view with it.
Magnification is nice, it makes it easier to see details of
objects, but without sufficient light gathering power, the
nebulae, and galaxies that we're interested in observing, will
be too faint to see.
The light gathering power of a telescope is determined by
the diameter of its primary or objective mirror. Telescopes
are basically light buckets, the wider they are in diameter,
the more light they can collect, and therefore the fainter the
objects are that we'll be able to see. Our telescope is 14
inches (355 mm) in diameter. As the light leaves the
telescope's eyepiece at the spot where the image comes into
focus (known as the exit pupil), it is about 7 mm in diameter,
so the telescope's primary mirror is about 50 times wider
(350mm/7mm) than the exit pupil. That means that the mirror
has 2500 times more surface area than the exit pupil (50 x
50). So, using our 14 inch telescope, we'll be able see
objects that are 2500 times fainter than we would with our
naked eye. This means that we should be able to use this
telescope to see objects that are about 14th magnitude.
Magnitude is a measure of how bright a star appears when
seen from Earth. It is related to how much energy is leaving
the star as visible light and to how far the star is away from
Earth. The smaller the magnitude, the brighter the star. The
brightest star in the sky other than the sun is Sirius, which
appears to be -1 magnitude. The faintest stars that a human
eye can see on the clearest night are 6th magnitude; there are
thus 7 magnitudes between them. The stars at the limit for
observing through our telescope are thus slightly fainter
compared to the faintest ones we can see as those stars are to
Sirius.
This assumes though, that we are looking through a vacuum,
which we are not. Air currents in the atmosphere and scattered
light from street lamps, nearby cities, and sometimes the
moon, brighten the background of the sky and limit how faint
the objects are which we will be able to see. Since we are
fairly close to sea level, there's a lot of atmosphere and
moisture to look through, and since we're on campus, albeit at
the edge, there's a significant amount of light from nearby
buildings and street lamps as well. I usually have success
with spotting objects which are brighter than 8.5th magnitude
and have been able to spot on occasion objects nearly as dim
as 10th. Since the light from these objects, usually nebulae
or galaxies, is spread out and not concentrated at a point,
like a star, I expect that the dimmest stars that I see on
those nights are between 10th and 12th magnitude. The Keck
telescopes in Hawaii, which are 10 meters in diameter, can
detect stars at about 22nd or 23rd magnitude.
- How old is the telescope and how much did it
cost?
-
I don't have a concrete answer for this one. The manual for
the telescope is for a 1981 model, but I think it was donated
to the university around 1984, costing then around $11,000.
I've seen reviews of a comparable 1990's model priced in the
$6000 range. You can get a good idea about how much telescopes
go for nowadays by looking at the advertisements in such
magazines as
Sky and Telescopeor
Astronomy.
- What kind of research has this telescope been
used for?
-
The physics department uses this obsesrvatory strictly for
educational purposes. In addition to the public nights that we
offer, students of the introductory astronomy class (Physics
406), and of the introductory astrophysics class are brought
out to the observatory at least once a term (there are many
sections, so this can take the entire term). Students in the
introductory class then must write a laboratory report about
the telescope and the objects that they see.
While it might be possible to do some rudimentary research
with a telescope this size, these days it is more of a 'scope
for a dedicated amateur. Such amateur astronomers are noted
for spotting new comets and asteroids. The
High Energy Astrophysics Group
research grouphere does do astrophysical research, but
uses a telescope (COMPTEL) on an orbiting satellite - the
Gamma Ray Observatory. Unlike the Hubble Space Telescope,
COMPTEL looks at light that is of much higher energy, and
therefore of much higher frequency than we can see directly
with our eyes.
- How Far? How large? How long ago?
-
I keep losing track of all of this information so I have
selfishly put it onto the web. A few notes: Planetary (and
lunar) radii are given in terms of Earth radii (the Earth's
radius is 6,378.1 km at sea level at the equator.) Planetary
distances are given in astronomical units (AU), where one AU
is the average distance from the sun to the earth (which is about 93
million miles or 150 million km). Distances outside the solar
system are measured in light years (ly), the distance light
travels in a year, (which is 63,000 AU, 9.5 trillion km, 6
trillion miles).
|
Object |
How far? |
How large? |
How long ago (was it formed)? |
|
Moon |
250,000 miles; 400,000 km |
0.272 earth radii |
4.55 billion years |
|
Mars |
1.5 AU |
0.532 earth radii |
4.55 billion years |
|
Jupiter |
5.2 AU |
11.2 earth radii |
4.55 billion years |
|
Saturn |
9.5 AU |
9.449 earth radii |
4.55 billion years |
|
Sirius |
8.6 ly |
|
|
|
Procyon |
11.4 ly |
|
|
|
Altair |
16.8 ly |
|
|
|
Vega |
25.3 ly |
|
|
|
Spica |
262 ly |
|
|
|
M45, Pleiades |
380 ly |
|
less than 100 million years |
|
Betelgeuse |
428 ly |
|
|
|
Polaris |
431 ly |
|
|
|
M44, Praesepe ("manger"), aka Beehive cluster |
577 ly |
|
|
|
Stars in the constellation Orion (besides
Betelgeuse) |
over 700 ly |
|
2-12 million years |
|
Saiph |
722 ly |
|
|
|
Rigel |
773 ly |
|
|
|
Almitak |
818 ly |
|
|
|
Mintaka |
916 ly |
|
|
|
M27, Dumbell Nebula |
1,250 ly |
2 ly diameter |
|
|
M42, Orion Nebula |
1600 ly |
15 ly diameter |
|
|
M57, Ring Nebula |
4100 ly |
|
20,000 years ago |
|
M17, Omega Nebula |
5000-6000 ly |
|
|
|
M8, Lagoon Nebula |
5800 ly |
|
|
|
M1, Crab Nebula |
6300 ly |
10 ly x 15 ly, center ~4.4 ly diameter |
1054 C.E. |
|
M13, Great Globular Cluster in Hercules |
22,800 ly |
200 ly diameter |
|
|
M3 globular cluster |
30,600 ly |
|
|
|
M31, The Andromeda Galaxy |
2.9 (2.2?) million ly |
120,000 ly diameter |
|
|
M32 |
2.9 (2.2?) million ly |
8000 ly diameter |
|
|
M81, Bode's Galaxy |
12 (10.5?) million ly |
100,000 ly |
|
|
M82, Cigar Galaxy |
12 (10.5?) million ly |
smaller than M81 |
|
|
M65, one of Leo triplet of galaxies |
35 million ly |
|
|
|
M66, one of Leo triplet of galaxies |
35 million ly |
|
|
|
M51, Whirlpool Galaxy |
37 (20?) million ly |
65,000 ly diameter |
|
Data for this table was obtained from Dixon's
Dynamic Astronomy, Karl Kuhn's
In Quest of the Universe,
Galaxies by Timothy Ferris, the
Hipparcos catalog sample pages, and the
SEDS Messier Object
page. The data did not always agree between sources.
- What about meteor showers?
-
On any given night, if you go out to a dark sky and watch
the stars, you'll be able to see about one meteor streak by
per hour as a piece of rock enters the atmosphere and burns
up. During meteor showers however, one can see as many as 50
to 100 per hour.* We see these showers when the Earth crosses
the path of debris left behind from a comet. Because we cross
a number of the same paths year after year in the same
direction, meteors from indivdual showers appear to come from
the same spot in the sky each year and are named after the
constellation that that spot is in. The paths that these
meteors take, can cross the entire sky and the spot that they
radiate from is also fairly large. This makes observing meteor
showers something that you wouldn't want to do with a
telescope. The field of view is so small that you'd miss most
of the show. A better way to see a meteor shower is to find a
dark clearing away from city lights, lie down and look up at
the sky. For more information on meteor showers see
Sky and Telescope's meteor page.
Other objects that are better seen with the naked eye
include human-made sattellites including the International
Space Station (ISS). These also appear in the sky too briefly
and move to fast to easily catch in the telescope, generally
crossing the entire sky in a few minutes.
The
Human Space Flightpage will tell you where & when to
look for the Space Shuttle and the ISS.
* Some years, if the source comet may have dumped more
debris into the section of its orbit that we cross, in which
case we might catch a meteor storm of 500 to 2000 meteors per
hour!
-
I want to be an astronomer, what should I do?
-
Well, first off, everyone can be amateur astronomers. All
that it takes is looking up at the sky on a clear night and
liking what you see. Try using binoculars as well and look at
the moon. The next thing you'll want to do and to continue to
do is read. Read a lot. If you want to learn more about the
names of the stars and constellations and a bit about how they
appear to move through the sky I recommend a book by H. A. Rey
(the author of the
Curious Georgebooks) called
The Stars. You'll also want to pick up some of the
astronomy magazines out there. Younger readers will appreciate
Odyssey, whereas older readers will find
Astronomyor
Sky and Telescopeto be excellent magazines all three of
which cover current events in astronomy as well as present
articles giving background information on various astronomy
topics. Most larger bookstores and most libraries will have an
astronomy section, and the web is an excellent source as well.
There is probably an amateur astronomy association in your
area. I've listed some of the ones closest to UNH just before
the links to this FAQ on
the main page. They are great
groups to get together with to talk about astronomy and to
have a chance to look through other people's telescopes.
Professional astronomy is mostly a specialty for
physicists, but it also overlaps with earth sciences and
mathematics. If you want to become a professional astronomer,
or at least have a more in depth appreciation for what they
do, you'll want to take as many math and science classes as
you can in high school, particularly the advanced math and
physics classes. If you are more interested in planets and the
moon than in stars, galaxies, nebulae, and what not, then
you'll want to look for colleges that have strong geophysics,
or meterology programs. They may even have a program that is
called "planetary science" (MIT, CalTech, U. of Colorado at
Boulder, Brown, and U. of Arizona do) or one that offers
astronomy as a degree separate from physics. If you are more
interested in stars, galaxies, quasars, and cosmology, you
want to look for colleges with strong astronomy groups within
their physics departments or even with a separate astrophysics
group. UNH has a gamma-ray astrophysics group, a
solar-terrestrial theory group, and a space science group
within our physics and earth, oceans and space departments.
Once you are in college, try to get involved with research as
a part time or summer job. They don't expect you to know
everything right away, but it is a great learning
experience.
- Why is the sky so bright at night?
-
Part of the reason the sky around our observatory can get
fairly bright is because of the lighting around campus. Much
of the light, along Mast Road, Main St. and A-lot as well as
some of the fields occasionally in use, is directed not only
toward the ground it is intended to illuminate, but also up
into the air. Whether it goes there directly, or is reflected
off the ground, the light then scatters around off of dust and
moisture in the the atmosphere, brightening the sky. The full
moon does this as well, and we see quite a bit of bright sky
showing up on nights when it is out. We tend to schedule
public nights for times when the moon won't be out so that we
can still see the dimmer objects.
For the most part, the campus lights are there for
additional security and I don't have a problem with that
(although some folks will argue that increased lighting
actually promotes crime activity and/or gives folks a false
sense of security - see the International Dark-Sky Association
site below for more details). The lights we have on campus
could be more efficiently designed and shielded though, to
send light more to where it is intended. Since refitting the
lights with more efficient fixtures, while in the long run may
be more economical, in the short term is probably a bit pricy,
the observatory uses a quick fix. We have a "Sky-glow" filter
which blocks out those lines in the spectrum coming from
Mercury and Sodium lamps. It works best in screening out light
from low-pressure Sodium lamps but enhances the contrast
noticibly even from the high-pressure kind and the mercury
ones we use. We can't do anything about the moon though beyond
scheduling most of our open nights for times when the moon is
not out. Light from incandescent bulbs can't be easily
screened out either.
Sky-glow is yet another reason why most major observatories
are located high up in the mountains, or in the case of the
Hubble Space Telescope, out in orbit. When you are above much
(or all) of the atmosphere, there's much less of an effect of
light scattered about - there are fewer particles to scatter
off of.
For additional information on light polution see the
Interational
Dark-Sky Association,
New England Light Pollution Advisory Group or if you're interested
in how serious the problem is around you, check out a map pertaining
to light polution found on our
Clear Sky Clock Site .
|