These days you can't just grind
your own mirror in the basement, buy some Kellners and enjoy the night-sky
from your back yard. Astronomy has been
improved immensely by the internet and companies that truly understand
marketing. If you want to succeed in this exciting new incarnation of
the hobby, you need to be prepared to pay the price of admission and avoid
potential mis-steps. This guide is intended as a short introduction to
the major aspects of astronomy as a social phenomenon. It will acquaint
you with the basic concepts and principles you will need to run with
the
pack in the 21st century!
You want to be with the in-crowd when
engaging in a hobby so dangerously close to geeky scientific pursuits, so
learn to spot the right people in
any group.
Most importantly, "experts" have spent several
tens of thousands of dollars on optical tube assemblies (OTA's) and eyepieces,
generally preferring
an instrument and eyepieces that meets the following criteria:
The best specialties
are galaxies under
1 arcsecond and/or dimmer than 18th magnitude. Also good are open clusters
in other galaxies or globular clusters anywhere. By spending enough money
and using averted vision (q.v.), you should be able to achieve a sort of
space-trance
in which you convince yourself that the grainy dust-mote-sized ball you
are looking at is stunning! Do be extremely careful, however, picking a speciality:
once you have declared your interest and become an expert, it is bad form
to look at other types of objects. Example, you decide that visual examination
of objects from the 2MASS survey is what you need to spend your money and
time
on. After you have established this as your area, you must avoid looking
at planets and curse any and all lunar appearances, even if you might really
enjoy
taking a quick look at Posidonius. If you get caught, you may clear yourself
by claiming to be testing your optics with the authoritative "craterlets
in Plato" test, but make sure you see at least 10!
Also, some specialities
that seem good are really not. For example, double-star work, since it
requires good optics and favors unobstructed tubes would seem ideal at
first, but
there are several reasons not to take it up: a) high magnifications required
generally
obviates need for expensive wide-field eyepieces; b) there are some well-known
limits to resolution; c) the math implied in common terms such as "angular
separation" makes this a nerd's racket. Similarly, while you may most
enjoy the "multi-colored splendor of unidentified open clusters",
don't make the mistake of trying to analyze stellar spectra or anything
of that sort!
Industry Experts:
These are the celebrities
of your hobby. They are generally altruists, good listeners and scrupulously
honest; most completely transcend self-interest.
You know this because you have met them, if you are an expert.
Novices/Newbies
Novices are in all ways the
most pathetic type of astronomers. They have been known to spend less than
a hundred dollars on all their equipment
combined and then compound this transgression by spending a long
time looking only at truly spectacular sights. Some have been known to look
at
the moon
with 60mm refractors and think it was interesting, obviously ignorant
of the delicacy and subltety of detail they could see in the Virgo cluster
instead. Or, perhaps worse, they pretend that their 10" Dobsonian's
diffraction spikes are not a big deal and that they can actually
see more with it than the expert with an exquisite 30mm apochromatic
refractor.
Try not to hang out with novices unless you intend to take them under
your
wing and recommend significant upgrades to their equipment.
Professionals
Spend even more than experts,
with distinction that they favor large apertures and usually no eyepiece
and occasionally know what they are talking about.
Do not associate with them.
Nerds
These are the less and less common, since
they tend to avoid crowds. Fortunately, younger nerds are probably not inclined
(or cannot afford) to pursue astronomy
and are more likely to be drawn to computers. Typically nerds will
be too busy conducting measurements of some esoteric nature to be a threat
to
your social status.
Observing Techniques/Other Terms
"Averted Vision": Expert turns head, squints eyes
and pretends to see barred-spiral structure in very dim, distant galaxy.
One occasional faux
pas with this technique is that it is performed in front of ignorant
novices or professional astronomers while the scope cap is still in place;
also make
sure the drive is turned on!
Dark Adaptation: If you have children, just say: "No, honey, those
men are not pirates." Otherwise, practice and exhibit your dark adaptation
at every opportunity, e.g., "Do those EMT idiots realize they are destroying
my night vision with their headlights!"
Seeing: While some have tried to rigorously quantify seeing, it is by nature
a fairly slippery concept, which can be useful -- it will be unique to your
specific time and place. When talking to your fellow astronomers, for example,
it is better to say that the seeing in your location was awful despite promising
transparency rather than admitting that you just felt more like staying in
and watching re-runs of "News Radio". Or, you might find that a
night of spectacular seeing allowed you to detect Charon as a tiny disk (and
perhaps some hint of detail with averted vision).
Dawes Limit: Strictly the minimum angular separation of equally bright stars
detectable by a telescope of a given aperture. The proper application of
this formula is to make sure that your new telescope can split a pair of
stars at a separation slightly larger than would be indicated by its aperture;
otherwise, there's not much further use for this kind of formula.
Magnification: While magnification is at its simplest the focal length of
the objective divided by the focal length of the eyepiece, it is at times
a source of almost religeous contention. As an expert, you are well-advised
to favour zealously either a low-magnification or high-magnification approach.
For example, if you are an expert on the outer planets, you might say that
you prefer to use a low magnification in order to frame Neptune and its moons
with a gorgeous field of stars. Conversely, you might favour a higher magnification
approach to work on globular clusters, so that you can increase the contrast
of the surrounding sky and zoom in on one or two of the more interesting
stars. As a rule of thumb, the best magnification is usually the one rendered
by the focal length of the eyepiece you paid the most for.
AFOV (Apparent Field of View): AFOV in eyepieces is a non-linear function
increasing with price and mass, with a sharp change in slope at around 50
degrees AFOV. You can always count on at least 50 degrees AFOV being usable,
with some distortion around the edges.
Equipment
In a hobby like astronomy, which was only recently
rescued from geeks, you have to have the right gear. Telescopes (OTA) and
eyepieces are critical.
Luckily, there are not a lot of acceptable options, although the market
seems full of products. Knowledge of 6 brands is adequate for good standing
in
the fraternity. What you want to say with your equipment is this: "I
know enough about astronomy to recognize the best, and I care enough
to spend whatever it takes for that little extra something that others
acknowledge
after spending their money to buy the same thing."
Astrophysics (AP): Top of the line APO refractor OTA's. Not only do they
cost as much as a good car, the waiting list is now approaching infinity.
This combination makes their quality inassailable. The cynical and jaundiced
might point out that there would be very few people honest enough to criticize
an instrument they just spent 20K and 10 years waiting for, but those people
are not experts (q.v., q.e.d.).
Takahashi (TAK): Only slightly less desirable than AP. Though they cost
more, they are generally produced in huge quantities of several dozen per
year, making their quality a bit suspect.
Televue (TV): Truly affordable in comparison to AP and TAK, these instruments
are only about as expensive as a reliable used car. While the quality is
obviously better than the "big three", it cannot compare with AP
and TAK, due to lower price and higher availibility. The stars of the TV
line, remarkably, are two achromatic refractors, the Pronto and Ranger, which
even experts are allowed to have as travel scopes, although they exhibit
chromatic aberrations that would scare children in a 60mm Tasco refractor.
Not to worry, however, TV makes most of their money on the high-end eyepieces,
some of which are bigger than the Ranger and Pronto.
Meade, Celestron, Orion, aka "the big three": These
companies obviously care nothing for astronomers or astronomy; if they did,
they would
make fewer instruments and charge more money. The only consistent exceptions
are:
Others: Risky. While a small or otherwise obscure company may produce a
good quality or adequately priced instrument or eyepiece, you want get the
name recognition and brand identity that is so essential to your development
as an astronomer. Judging equipment by what you can see with it opens you
up to criticism from others without the warm protection of fellow users.
Alternately, sometimes an expert can use uncertainty to his advantage, e.g.:
"This AstroRaqet ($4950 for OTA from Bluto and Oyle Optical) utilizes a
43mm objective made from the bottom of a 61/2 oz. coke bottle amd SDF glass with
a Yolo-inspired optical path, resulting in optical quality and resolution that
is only _just_ short of exquisite for my work with asteroid occultations of galaxies
in the Virgo group. Several of my fellow observers have been stunned by the quality
of images offered on the planets, and the compact multi-tubed design never fails
to get attention at star parties."
Eyepieces
Televue: TV eyepieces are the only
ones consistently expensive and large enough to justify their use. Al Nagler
wisely takes the best ones out of
production quickly so that they retain their value, so don't worry
about the cost, as it is an investment.
Everyone else: Don't even consider it -- you may get lucky and see something
in the eyepiece that looks similar to what an expert sees in a Televue,
but you won't get the "space-walk" feeling or that undefinable
something you need to feel good about your hobby. Some possible exceptions
are certain
orthoscopics, with the stipulation that they are no longer in production.
Also, you can sometimes use big-three eyepieces if the better eyepieces
adversely affect your custom Dobsonian's balance or you fear your neighbors/kids/family
might not appreciate the view of the better eyepieces or might possibly
put
a bit of eyelash against it.
Telescope Designs
Refractors
Achromatic: Design using two-element
crown and flint glass objective. Can only focus a sub-set of the visible
spectrum, thus will display a
violet nimbus around very bright objects. There are at least four objects
in the
universe bright enough from earth to make this a problem, so it is
advisable to spend at least 5K more for an apochromatic refractor. Only
acceptable
design in certain small scopes from Televue.
Apochromatic: Design using (typically) three-element objective, with the
third consisting of a special type of glass. The better brands use glass
that is not only rare and expensive but also (preferably) prone to break
with normal changes in temperature. Apochromats are thus able to focus three
colours, but their capabilities do not stop there. In many cases, the owner
of an apochromat of 50mm or less is able to detect subltety of texture and
delicacy of coloration in objects that took years for the 200 inch reflector
at Palomar to find. This type of telescope is almost always owned by experts.
Experts generally use these instrument to demonstrate the fact that they
can achieve dangerously high magnifications on large, bright objects as well
as to view very small or faint objects at extremely low magnifications.
"60mm"/"Department Store Telescope (DST)": These are
a special class of achromatic refractor (typically) which should never be
used for astronomy, since fewer than 99.9% of the more interesting astronomical
objects can be seen with it. One real sign of an expert is that he will spend
a lot of time talking about how his 40K investment leaves the 40 dollar department
store scopes in the dust. Ironically, Huygens and Galileo (not to mention
Messier possibly) are thought to have made some serious discoveries with
this class of telescope. Of course, Huygens and Galileo did not have the
shaky mounts and inferior coatings of DST's to worry about...not to mention
the light pollution or the limited eyepiece selection amateurs have to deal
with nowadays.
Reflectors
Newtonians(including Dobsonian mounted(q.v.)):
These designs
use a parabolic mirror as an objective to focus light and therefore do
not have any problem with secondary color. Unfortunately, these designs
are plagued with a very high aperture for the dollar and are widely
available. Also, diffraction spikes from diagonal supports can be seen
on a a handful
of brighter objects, making these instruments useless for the serious
astronomer. Some mirrors, however, are exceptional and acknowledged to
be good even by
experts. Those mirrors almost invariably are no longer made.
Off-Axis
Reflector: Mildly interesting currently due to lack of diffraction spikes
and fairly high cost.
Compound:
Schmidt-Cassegrain: Once considered very good, even
by experts. Now commonly available, so not recommended. Similar to Dobsonians/Newtonians
inasmuch
as they may (in larger apertures) appear to have better resolution
and light-gathering capabilities than apochromats, but every expert knows
that
this is not the whole story -- the obstruction of the secondary (which
reflects light to the eyepiece from the concave primary) reduces
the contrast to the point where they are almost equal to "department
store telescopes (q.v)".
Maksutov-Cassegrain: Still considered interesting
in larger apertures (>6")
due to higher cost and smaller secondary obstruction (when compared
to SC). Older models from the time when a 3" Maksutov cost the same
as affordable housing were once considered capable of performance equal to
the best apochromatic
refractors.
Other: While other designs exist, they are not generally
capable of the exquisite performance and name recognition you need to succeed
in astronomy.
Mounts
This is one of the few areas still available
for individuality. Whereas the old wisdom was that the mount is more important
than the telescope, the new
ethos seems to be anything goes, although a few rules apply.
