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Part I
For months now I have
been looking over the market's best products trying to identify the optimal
way for a serious student to get into the field of observational astronomy,
while keeping the budget under one thousand dollars.
The idea was to not compromise on either - the quality of optics, or
the needed accessories.
I formulated my goal in familiarizing myself with all the major
planets, constellations and star clusters within our galaxy, and larger
neighboring galaxies.
Task required either a set of powerful binoculars or an acceptable size
telescope.
I approached the problem from both theoretical and practical perspectives,
in two phases:
Phase one entailed
a few weeks of reviewing basic principles of optics, terminology, types
and prices of available equipment, communications with vendors, manufacturers
and optical technicians, purchasing and reading few volumes on history
and theory of astronomy etc. I also went over the last four years of major
product reviews in leading astronomy magazines and ordered catalogues,
some videos and samples of available products from leading telescope manufacturers,
and talked to vendors and optics engineers in Russia, China, US and UK.
And, having realized the depth of field of my ignorance ... came to some
educational conclusions:
1. Do not rely on labels as indications
of origin or quality, as excellent (and not so excellent) optics are often
made, labeled and sold by different parties.
2. If you buy mail order, make sure they
take returns, no questions asked.
3. If you purchase at a local store, do
not spend twice as much.
4. Provided the lenses and mirrors are
the state of the art (and in this age of high-tech components do not be
embarrassed to ask who and to what level of tolerances produced this or
that lens or mirror, and with how many and which coatings -- as some anti-reflective
coatings have excellent scratch-resistant properties, while others do not...),
the larger the aperture and corresponding light gathering capacity of an
instrument (diameter of the objective lens in a refractor, or primary mirror
in a reflector), the more and with higher contrast resolution you may observe.
The only limits here are budget and portability (more on that later).
5. The 'faster' the optics (the smaller
the focal length to objective lens or primary mirror diameter ratio) the
more wide field astrophotography adept and, often (aside from Newtonians),
more complex and expensive is the instrument.
6. Be ware of X vs. Y, and 'best in it's
class' product reviews. Who cares if X is better than Y, if Z is cheaper
(or reasonably more expensive) and better than either. Who cares if X is
best in it's class (of aperture, type of construction, or price), if no
instrument in this 'class' will be adequate for the purpose (be it deep-space
viewing or astrophotography), or will not be outgrown in six months time.
Watch out for the double negatives and do not buy optics on basis of marketing
eloquence alone.
7. Very few optics are of vari-focal nature
allowing for optimal wide field of view astro- photography and high power
of magnification narrow field of view observation. (Many professional models
consist of a fast 'photo' telescope attached to another observational unit,
which combo is outside of most budgets under $20,000). Even fewer allow
for coupling with a medium format photo camera, such as a Pentax 6x7cm.,
as opposed to a standard 35 mm.
8. In early days of serious amateur optics,
the often accentuated difference was one between refracting (dioptric=
utilizing lenses) and reflecting (catoptric or catadioptric= utilizing
mirrors, or mirrors and lenses, respectively).
In the middle ages of telescope-making, when complex aberration correcting
systems were advanced, primary distinctions were accentuated between the
simpler large Newtonian tubes with their curved primary and flat secondary
mirrors, and more complicated and portable light path folding Shmidt-Cassegrain
(with parabolic mirrors), or Maksutov-Cassegrain (with spherical mirrors),
or hybrids with spherical and parabolic primary and secondary mirrors -
all with tube sealing menisci of varying aberration-correcting qualities...
Now, it is the 'maintenance-free' versus 'cost-efficient' (dollars per
unit of aperture) distinction that often delineates practical alternatives
for the end user.
Most closed optical tube systems (refractors or reflectors with a front
lens or a correcting meniscus) allow for maintenance-free use, with the
total loss of light due to extra multi-coated glass element being less
than a negligible 1%! Unfortunately, due to costs of additional mutually
configured components, closed optical tube systems are typically more expensive
than their open tube Newtonian counterparts. If you don't mind cleaning,
re-aligning and re-coating mirrors now and again, save money and buy a
Newtonian. I, unfortunately, prefer the maintenance-free concept
of astro-navigation.
Phase two entailed
unaided observation of the milky way from high altitude and clear ocean
side premier locations, review of existing astrophotographs (while paying
close attention to the type and SIZE of optics utilized in obtaining the
images), and ordering and field testing a number of binocular and telescope
systems.
Surprisingly, stargazing trips to clear skies locations made two points
abundantly clear.
First. Anyone who cares about practical astronomy will get out of the
city & light pollution areas (instead of splitting hairs on a gnat's
ass, as the saying goes, by impressing themselves with how relatively well
they can actually see through all that smog...) Amazingly, some people
actually get paid to review professional optics systems just so...
Second.
Binoculars are not an option but a 'must'! -Why? After all, to many first
time astro-optics purchasers it is not entirely obvious. When left behind
occasionally star sprinkled city skies give way to shimmering vicissitudes
of the glittering sea of a myriad heavenly wonders, the advantage of the
wide angle binocular panorama becomes self-evident. Whether you do or do not ever obtain a serious telescope, a powerful
pair of large aperture binoculars is a must and a panacea for anyone entering
the field of stars.
A set of powerful binoculars, like Tasco 124 RB1, is essentially a set
of two joined 70 mm refractor telescopes bringing to your mind's
eyes (the visual cortex, if you will) an equivalent of light gathering
quantity of an about 100 mm (4'') refractor telescope. Price-tag of a 100
mm apochromatic refractor is over $2,000.
And
(no matter how many perfectly polished and coated synthetic fluorite apo
lenses it packs) it will not give you either the majestic View of wide field
giant binoculars, or the penetration of quality larger (150 to 200 mm reflector);
both of which - the large binoculars and a powerful refractor - may cost
much less.) But I am getting ahead of myself.
Whatever the instruments, optics and accessories must suffice for the
applications.
Optics:
Optics
must allow to observe the desired range of stellar and planetary cosmos
(be of substantially large primary aperture to not require periodic upgrading
to larger models), and be of textbook perfect quality (for lack of contrast,
coma or other avoidable optical defects negate the whole purpose of sky
watching). Review of resolved galactic images suggested that 150 mm (6'')
- with at least 120 mm unobstructed - is the minimum of aperture which
would allow for the high contrast and resolution viewing and astrophotography
desired. In light of the stipulated budget, this requirement displaced
otherwise excellent apo-chromatic (corrected for 3 primary wave-lengths)
refractors, as well as most of the less expensive (yet, too expensive) and
portable catadioptric Cassegrain models from my consideration.
Accessories:
The system(s) should allow for uncompromised quality of stellar observation
at full range of magnifications (and hence, include the requisite variety
of eyepieces and barlow lenses to allow powers of magnification for planetary
and stellar observation), as well as allow for serious astrophotography
work (which, in addition to availability of a suitable camera with adapters,
requires a sturdy tripod and an equatorially mounted motor drive.)
The long and the short of it came to this:
For one thousand dollars I had to find an optically perfect set of two
instruments:
A. Optically excellent giant binoculars
(with aperture of at least 70 mm), and
B. Closed tube maintenance-free suited
for astrophotography reflector telescope of no more than F10, of at least
120 mm unobstructed aperture, with tripod, equatorial mount, motor/clock
drive, eyepieces and barlow lenses, included.
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