_NOTES ON TELESCOPIC WORK._
Preparation.—Working-Lists.—Wind.—Vision.—Records.—Drawing.—Friendly
Indulgences.—Open-Air Observing.—Method.—Perseverance.—Definition in
Towns.—Photography.—Publications.—Past and Future.—Attractions of
Telescopic Work.
_Preparation._—An observer in commencing work in any department of
astronomy will find it a very great assistance to his progress if he
carefully reads and digests all that has been previously effected in
the same line. He will see many of the chief difficulties and their
remedies explained. He will further learn the best methods and be in
the position of a man who has already gained considerable experience.
If he enter upon a research of which he has acquired no foreknowledge
he will be merely groping in the dark, and must encounter many
obstacles which, though they may not effectually turn him from his
purpose, will at least involve a considerable expenditure of time and
labour. On the other hand, a person who relies upon guidance from prior
experimentalists will probably make rapid headway. He will be fortified
to meet contingencies and to avoid complications as they arise. He
will be better enabled to discriminate as to the most eligible means
and will confidently endeavour to push them to the furthest extent.
By adopting existing instructions for his direction and familiarizing
himself with the latest information from the best authorities he will
in a great measure ensure his own success or at least bring it within
measurable] distance. The want of this foreknowledge has often been
the main cause of failure, and it has sometimes led to misconceptions
and imaginary discoveries; for after much thought and labour a man
will overcome an impediment or achieve an end in a way for which he
claims credit, only to find that he has been anticipated years before
and that had he consulted past records, his difficulties would have
been avoided and he might have pressed much nearer the goal. Too much
importance cannot be attached to the acquisition of foreknowledge of
the character referred to, though we do not mean that former methods
or results are to be implicitly trusted. Let every observer judge for
himself to a certain extent and let him follow original plans whenever
he regards them as feasible; let him test preceding results whenever
he doubts their accuracy. We recommend past experiences as a guide,
not as an infallible precept. It would be as much a mistake to follow
the old groove with a sort of credulous infatuation as it would be to
enter upon it in utter ignorance of theoretical knowledge. An observer
should take the direction of his labours from previous workers, but be
prepared to diverge from acknowledged rules should he feel justified in
doing so from his new experiences.
[Illustration: Fig. 18.
Refracting-Telescope on a German Equatoreal.]
_Working-Lists._—Full advantage should be taken of good observing
weather. Sir John Herschel most aptly said that no time occupied in the
preparation of working-lists is ill-spent. In our climate the value
of this maxim cannot be overrated. If the 100 hours of exceptionally
good seeing, available in the course of the year, are to be profitably
employed, we must be continually prepared with a scheme of systematic
work. The observer should compile lists of objects it is intended to
examine, and their places must be marked upon the globe or chart so
as to avoid all troublesome references during the actual progress of
observation. If he has to consult ephemerides and otherwise withdraw
attention from the telescope he loses valuable time: moreover the
positions hurriedly assigned in such cases are frequently wrong and
entail duplicate references, involving additional waste of time; all
this may be avoided by careful preparation beforehand. If he has a
series of double or variable stars to observe he must tabulate their
places in convenient order so as to facilitate the work. If he intend
hunting up nebulæ or telescopic comets he must carefully mark their
positions relatively to adjoining stars. In the case of selenographical
objects or planetary markings he may equally prepare himself by
previous study. Adopting these precautions, objects may be readily
identified and the work expedited. When no such preparation is made
much confusion and loss of time result. On a cloudy, wet day observers
often consider it unnecessary to make such provision and they are taken
at a great disadvantage when the sky suddenly clears. A good observer,
like a good general, ought to provide, by the proper disposition of his
means, against any emergency. In stormy weather valuable observations
are often permissible if the observer is prompt, for the definition is
occasionally suitable under such circumstances. The most tantalizing
weather of all is that experienced during an anti-cyclone in winter.
For a week or two the barometer is very steady at a high reading, the
air is calm, and the sky is obscured with an impenetrable mass of
clouds.
_Wind._—The influence of wind on definition has been much discussed
in its various aspects, but it is scarcely feasible to lay down
definite rules on the subject. The east wind is rarely favourable to
good seeing, but the law is far from absolute. We must remember that
several distinct currents sometimes prevail, and the air strata at
various elevations are of different degrees of humidity and therefore
exercise different effects upon telescopic definition. A mere surface
breeze from the east may underlie an extensive and moist current from
the south-west, and telescopic definition may prove very fair under
the combination. Calm nights when there is a little haze and fog,
making the stars look somewhat dim, frequently afford wonderfully
good seeing. As a rule, when the stars are sparkling and brilliant,
the definition is bad; planetary disks are unsteady and the details
obliterated in glare. But this is not always so. I have sometimes
found in windy weather after storms from the west quarter, when the
air has become very transparent, that exceptionally sharp views may be
obtained; but unfortunately they are not without drawbacks, for the
telescope vibrates violently with every gust of wind and the images
cannot be held long enough for anything satisfactory to be seen. The
tenuous patches of white cirrous cloud which float at high altitudes
will often improve definition in a surprising manner, especially on the
Moon and planets. Of course this does not apply to nebulæ or comets,
which are objects of totally different character and essentially
require a _dark_ night rather than good definition before they may be
seen under the best conditions. As a rule, a steady, humid atmosphere
is highly conducive to good seeing, and it is rather improved than
impaired by a little fog or thin, white cloud. Some unique effects
of peculiar definition, such as oval or triangular star disks, have
been occasionally recorded, but we must content ourselves with a bare
reference to these phenomena. With regard to the general question it
may, however, be added that the character of the seeing often varies at
very short intervals in this climate. In the course of a night’s work
the definition will sometimes fluctuate in a most remarkable manner. An
observer who comes to the telescope and finds it impossible to obtain
satisfactory images should not entirely relinquish work at the first
trial. After an interval he should again test its performance, for
it frequently happens that a night ushered in by turbulent vapours,
improves greatly at a later period, and in the morning part becomes so
fine that it is worthy to be included in the select 100 hours assigned
by Sir W. Herschel as the annual limit. Those who reside in towns
will usually get the best definition after midnight, because there
is less interference then from smoke and heated vapours. It would
greatly conduce to our knowledge of atmospheric vagaries as affecting
definition, if observers, especially those employing large aperture,
preserved records as to the quality of the seeing, also direction of
wind and readings of the barometer and thermometer.
_Vision._—There are perhaps differences quite as considerable in
powers of vision as in quality of definition. It is not meant by
this that the same person is subject to great individual variations,
though some people are certainly liable to fluctuations, according to
state of health and other conditions. Some eyes, as already stated,
are less effective in defining planetary markings than in detecting
minute stars or faint satellites of distant planets. Of course the
natural capacity is greatly enhanced by constant practice, for the
human eye has proved itself competent to attain a surprising degree of
excellence by habitual training. Frequent efforts, if not overpressed
so as to unduly strain the optic nerves, are found to intensify rather
than weaken the powers of sight. Thus a distinguishing trait among
astronomers has been their keenness of vision, which, in many cases,
they have retained to an advanced age. It is true Dr. Kitchiner said
his “eye at the age of forty-seven became as much impaired by the
extreme exertion it had been put to in the prosecution of telescope
trials, as an eye which has been employed only in ordinary occupations
usually is at sixty years of age!—to cultivate a little acquaintance
with the particular and comparative powers of telescopes requires many
extremely eye-teasing experiments.” But the Doctor’s opinion is not
generally confirmed by other testimony, the fact being that the eye is
usually strengthened by special service of this character. To unduly
tax or press its powers must result in injury; but it is well known
that the capacities of our sight and other senses are enhanced by
their healthy exercise, and that comparative disuse is a great source
of declining efficiency. Before the observer may hope to excel as a
telescopist it is clear that a certain degree of training is requisite.
Many men exhibit very keen sight under ordinary circumstances, but
when they come to the telescope are hopelessly beaten by a man who has
a practised eye. On several occasions the writer was much impressed
with evidences of extraordinary sight in certain individuals, but upon
being tested at the telescope they were found very deficient, both as
regards planetary detail and faint satellites. Objects which were quite
conspicuous to an experienced eye were totally invisible to them. I
believe it is a good plan for habitual observers to employ method in
exercising their sight. In my own case I invariably use the right eye
on the markings of planets and the left on minute stars and satellites.
Practice has given each eye a superiority over the other in the special
work to which it has been devoted, and I fancy the practice might be
more generally followed with success.
It is an advantage to keep both eyes open when in the act of observing,
especially when surrounding objects are perfectly dark and there is no
distracting light from neighbouring windows or lamps. The slight effort
required to keep the disengaged eye closed interferes with the action
of the other, and though this is but trivial, critical work is not
efficiently performed under such conditions. Whenever light interferes
the observer may exclude it by a shade so arranged as to afford
complete protection to the unoccupied eye.
If faint objects are to be examined the observer should remain in a
dark situation for some little time previously, so that the pupil
of the eye may be dilated to the utmost extent and in a state most
suitable for such work. After coming from a brilliantly lit apartment,
or after viewing the Moon or a conspicuous planet, the eye is totally
unfit to receive impressions from a difficult object, such as a minute
star or faint nebula or comet; some time must be allowed to elapse
so that the eye may recover its sensitiveness. As a rule amateurs
will find it best to confine their attention to one class of objects
only on the same evening, for if the Moon is first examined and then
immediately afterwards the telescope is directed upon double stars
and nebulæ, the latter objects are little likely to be seen with good
effect. If faint objects generally are persistently studied night after
night and the observer refrains from solar and lunar work, his eye
will acquire greater sensitiveness and he will readily pick up minute
forms which are utterly beyond the reach of a man who indiscriminately
employs his eye and telescope upon bright and faint objects.
_Records._—With regard to records, every observer should make a note
of what he sees, and at the earliest possible instant after the
observation has been effected. If the duty is relegated to a subsequent
occasion it is either not done at all or done very imperfectly. The
most salient features of whatever is observed should be jotted down in
systematic form, so as to permit of ready reference afterwards. It is
useful to preserve these records in a paged book, with an index, so
that the matter can be regularly posted up. The negligence of certain
observers in this respect has resulted in the total loss of valuable
observations. Even if the details appear to possess no significance,
they should be faithfully registered in a convenient, legible form,
because many facts deemed of no moment at the time may become of
considerable importance. The observer should never refrain from such
descriptions because he attributes little value to them. Some men keep
voluminous diaries in which there is scarcely anything worth record;
but this is going to the other extreme. All that is wanted is a concise
and brief statement of facts. Some persons have omitted references to
features or objects observed because they could not understand them,
and rather distrusted the evidence of their eyes; but these are the
very experiences which require careful record and reinvestigation.
_Drawing._—Few observers are good draughtsmen; but it is astonishing
how seldom we meet with real endeavours to excel in this respect. Every
amateur should practise drawing, however indifferent his efforts may
be. Delineations, even if roughly executed, are often more effective
than whole pages of description. Pictorial representations form the
leading attraction of astronomical literature, and are capable of
rendering it more interesting to the popular mind than any other
influence. They induce a more apt conception of what celestial objects
are really like than any amount of verbal matter can possibly do.
For this reason it becomes the obvious duty of every observer to
cultivate sketching and drawing, at least in a rudimentary way. He will
frequently find it essential to illustrate his descriptions, so as
to ensure their ready comprehension. In fact, a thoroughly efficient
observer must of necessity become a draughtsman. It should, however,
be his invariable aim to depict just what he sees and in precisely
the form in which it impresses his eye. Mere pictorial embellishments
must be disregarded, and he should be careful not to include doubtful
features, possibly existing in the imagination alone, unless he intends
them simply for his own guidance in future investigations. If he sees
but little, and it is faithfully delineated, it will be of more real
value than a most elaborate drawing in which the eye and imagination
have each played a part. It is an undoubted fact that some of the most
striking illustrations in astronomical handbooks are disfigured by
features either wrongly depicted or having no existence whatever. There
is very great need for caution in representing such markings only as
are distinctly and unmistakably visible. In all cases where the object
is new or doubtful the observer should await duplicate observations
before announcing it. It is better that new features should evade
discovery than that delusive representations should be handed down to
posterity. As regards selenographical drawings I would refer the reader
to what Mr. Eiger advises on p. 21 and 22 of volume v. of the ‘Journal
of the Liverpool Astronomical Society.’ My own plan in sketching at
the telescope is to first roughly delineate the features bit by bit
as I successively glimpse them, assuring myself, as I proceed, as to
general correctness in outline and position; then, on completion, I go
indoors to a better light and make copies while the details are still
freshly impressed on the mind. To soften details a small piece of
blotting-paper must be wrapped round the pointed end of the pencil, and
the parts requiring to be smoothed gently touched or rubbed until the
desired effect is attained. This simple method, properly applied, will
enable delicate markings to be faithfully reproduced, and it certainly
adds in no small degree to the merit of a drawing.
_Friendly Indulgences._—Every man whose astronomical predilections
are known, and who has a telescope of any size, is pestered with
applications from friends and others who wish to view some of the
wonders of the heavens. Of course it is the duty of all of us to
encourage a laudable interest in the science, especially when evinced
by neighbours or acquaintances; but the utility of an observer
constituting himself a showman, and sacrificing many valuable hours
which might be spent in useful observations, may be seriously
questioned. The weather is so bad in this country that we can ill
spare an hour from our scanty store. Is it therefore desirable to
satisfy the idle curiosity of people who have no deep-seated regard for
astronomy, and will certainly never exhibit their professed interest
in a substantial manner? Assuredly not. The time of our observers is
altogether too valuable to be employed in this fashion. Yet it is an
undisputed fact that some self-denying amateurs are unwearying in their
efforts to accommodate their friends in the respect alluded to. My own
impression is that, except in special cases, the observer will best
consult the interests of astronomy, as well as his own convenience and
pleasure, by declining the character of showman; for depend upon it
a person who appreciates the science in the right fashion will find
ways and means to procure a telescope and gratify his tastes to the
fullest capacity. Some years ago I took considerable trouble on several
evenings in showing a variety of objects to a clerical friend, who
expressed an intention to buy a telescope and devote his leisure to the
science. I spent many hours in explanations &c.; but some weeks later
my pupil informed me his expenses were so heavy that he really could
not afford to purchase instruments. Yet I found soon after that he
afforded £30 in a useless embellishment of the front of his residence,
and it so disgusted me that I resolved to waste no more precious time
in a similar way.
_Open-Air Observing._—Night air is generally thought to be pernicious
to health; but the longevity of astronomers is certainly opposed to
this idea. Those observers who are unusually susceptible to affections
of the respiratory organs must of course exercise extreme care, and
will hardly be wise in pursuing astronomical work out of doors on
keen, wintry nights. But others, less liable to climatic influences,
may conduct operations with impunity and safety during the most severe
weather. Precautions should always be taken to maintain a convenient
degree of warmth; and, for the rest, the observer’s enthusiasm
must sustain him. A “wadded dressing-gown” has been mentioned as
an effective protection from cold. I have found that a long, thick
overcoat, substantially lined with flannel, and under this a stout
cardigan jacket, will resist the inroads of cold for a long time. On
very trying nights a rug may also be thrown over the shoulders and
strapped round the body. During intense frosts, however, the cold will
penetrate (as I have found while engaged in prolonged watches for
shooting-stars) through almost any covering. As soon as the observer
becomes uncomfortably chilly he should go indoors and thoroughly warm
his things before a fire. He may then return fortified to his work and
pursue it for another period before the frost again makes its presence
disagreeably felt. On windy nights a knitted woollen helmet to cover
the head, and reaching to the shoulders, is an excellent protection;
but an observer had better not wear it more often than is imperative,
or it becomes a necessity on ordinary nights. It is a great mistake to
suppose that “a glass of something hot” before going into the night air
is a good preventive to catching cold. It acts rather in the contrary
way. The reaction after the system has been unduly heated only renders
the observer more sensitive, and the inhalation of cold air is then
very liable to induce affections of the throat.
A telescope permanently erected in the open, and exposed to all
weathers, must soon lose its smart and bright appearance, but it need
lose none of its efficiency, which is of far more importance; for it is
intended for service, not for show. The instrument should be kept well
painted and oiled. I find vaseline an excellent application for the
screws and parts controlling the motions, as it is not congelative like
common oils. The observer, before a night’s work and before darkness
sets in, will do well to examine his instrument and see that it is in
the best condition to facilitate work. Whole tribes of insects take up
their habitation in the base or framework, and even in the telescope
itself if they can effect a lodgment; and I have sometimes had to
sweep away a perfect labyrinth of spiders’ webs from the interior of
the main tube. On one occasion I could not see anything through the
finder, try how I would. I afterwards discovered that a mason-wasp
(_Odynerus murarius_) had adopted the vacuity in front of the eye-lens
as a suitable site for her nest; and here she had formed her cells,
deposited her eggs, and enclosed the caterpillars necessary for the
support of the young when hatched. On another night I came hurriedly to
the telescope to observe Jupiter with my single-lens eyepiece, power
252, but could make nothing out of it but a confused glare, subject
to sudden extinctions and other extraordinary vagaries. I supposed
that the branches of a tree, waving in the wind, must be interposed
in the line of sight, but soon saw this could not possibly be the
explanation. Looking again into the eyepiece, I caught a momentary
glimpse of what I interpreted for the legs of an insect magnified
into gigantic proportions and very distinct on the bright background
formed by Jupiter much out of focus. On detaching the eyepiece and
carrying it indoors to a light, an innocent-looking sample of the
common earwig crawled out of it. The gyrations of the insect in its
endeavours to find a place of egress from its confinement had clearly
caused the effects alluded to. Telescopic observers are thus liable to
become microscopic observers before they are conscious of the fact,
and perhaps also in opposition to their intention. Other experiences
might be narrated, especially as regards nocturnal observing in country
or suburban districts, where the “serious student of the skies” may,
like myself, find diversion to his protracted vigils by the occasional
capture of a too-inquisitive hedgehog or some other marauding quadruped.
[Illustration: Fig. 19.
The Author’s Telescope: a 10-inch With-Browning Reflector.]
_Method._—Nearly all the most successful observers have been men of
method. The work they took in hand has been followed persistently and
with certain definite ends in view. They recognized that there should
be a purpose in every observation. Some amateurs take an incredible
amount of pains to look up an object for the simple satisfaction
of seeing it. But seeing an object is not observing it. The mere
view counts for nothing from a scientific standpoint, though it may
doubtless afford some satisfaction to the person obtaining it. A
practical astronomer, with his own credit at stake and the interests of
the science at heart, will require something more. In observing a comet
he will either fix its position by careful measurement with reference
to stars near, or critically examine its physical peculiarities, or
perhaps both. In securing these data he will have accomplished useful
work, which may quite possibly have an enduring value. In other
branches of observation his aim will be similar, namely to acquire new
materials with regard to place or to physical phenomena, according
to the nature of the research upon which he happens to be engaged.
Such results as he gathers are neatly tabulated in a form convenient
for after comparisons. There have been instances, we know, where
sheer carelessness has resulted in the loss of important discoveries.
Lalande must have found Neptune (and mathematical astronomy would
have been robbed of its greatest triumph) half a century before it was
identified in Galle’s telescope, but his want of care enabled it to
elude him just when he was hovering on the very verge of its discovery.
Numerous other instances might be mentioned. Failure may either arise
from imperfect or inaccurate records, from a want of discrimination,
from neglect in tracing an apparent discordance to its true source,
or from hesitation. I may be pardoned for mentioning a case within
my own experience. On July 11, 1881, just before daylight, I stood
contemplating Auriga, and the idea occurred to me to sweep the region
with my comet eyepiece, but I hesitated, thinking the prospect not
sufficiently inviting. Three nights later Schæberle at Ann Arbor,
U.S.A., discovered a bright telescopic comet in Auriga! Before sunrise
on October 4 of the same year I had been observing Jupiter, and again
hesitated as to the utility of comet-seeking, but, remembering the
little episode in my past experience, I instantly set to work, and
at almost the first sweep alighted upon a suspicious object which
afterwards proved itself a comet of short period. These facts teach one
to value his opportunities. They cannot be lightly neglected, coming
as they do all too rarely. The observer should never hesitate. He must
endeavour to at least effect a little whenever an occasion offers;
for it is just that little which may yield a marked success—greater,
perhaps, than months of arduous labour may achieve at another time.
_Perseverance._—Persistency in observation, apart from the value
derived from cumulative results, increases the powers of an observer
to a considerable degree. This is especially the case when the same
objects are subjected to repeated scrutiny. A first view, though it
may seem perfectly satisfactory in its conditions and results, does
not represent what the observer is capable of doing with renewed
effort. Let us suppose that a lunar object with complicated detail
is to be thoroughly surveyed. The observer delineates at the first
view everything that appears to be visible. But a subsequent effort
reveals other features which eluded him before, and many additional
details are gradually reached during later observations. Ultimately
the observer finds that his first drawing is scarcely more than a mere
outline of the formation as he sees it at his latest efforts. Details
which he regarded as difficult at first have become comparatively
conspicuous, and a number of delicate structures have been exhibited
which were quite beyond his reach at the outset. The eye has become
familiarized with the object, and its powers fairly brought out by
training and experience. This training is very serviceable, but
is seldom appreciated in the degree of its influence. Many a tyro
has abandoned a projected series of observations on finding that
his initiatory view falls wofully short of published drawings or
descriptions. He considers himself hopelessly distanced, and regards
it as impossible to attain—much less excel—the results achieved by
his predecessors. He does not realize that their work is the issue
of years of close application, and that it represents the collective
outcome of many successive nights. I need hardly say that it is a
great mistake to anticipate failure in this way. No telescopic work
has been done in the past that will not be done better in the future.
No observer can rate his capacity until he has rigorously tested it by
experience. The eye must become accustomed to an object before it is
able to do itself justice. Those who have been sedulously engaged in a
certain research will, as a rule, see far more than others who are but
just entering upon it—not from a natural superiority of vision, but
because of the aptitude and power acquired by practice. No matter how
meagre an observer’s primary attempts may be, he should by no means
relax his efforts, but rather feel that his want of success must be
remedied by experience. It is a common fault with observers that they
leave too much to their instruments, and rely upon them for the results
which really depend entirely upon their personal endeavours. A skilled
workman will do good work with indifferent tools; for after all it is
the character of the man that is evident in his results, and not so
much the resources which art places in his hands.
Much also depends upon the feelings by which the amateur is actuated
when he commences work. A few enter into it with a degree of energy
and determination that knows no wearying and will accept no defeat.
Others display a half-hearted enthusiasm, and are constantly doubting
either their personal ability or their instrumental means. Many
others, again, when the circumstances appear a little against them
regard failure as inevitable. It need hardly be said, however, that
every difficulty may be surmounted by perseverance, and that a man’s
enthusiasm is often the measure of his success, and success is rarely
denied to him whose heart is in his work.
_Definition in Towns._—The astronomical journals contain some
interesting references to the definition of telescopes in large towns.
Of course the purer the air the better for observational purposes.
But observers who reside in populous districts need not despair of
doing really useful work. The vapours hanging over a large city are
by no means so objectional as is commonly supposed. When they are
circulating rapidly across the observer’s field of view they will
prove very troublesome at times; but in a comparatively tranquil
state of the air definition is excellent. I have frequently found
planetary markings very sharp and steady through the smoke and fog of
Bristol. The interposing vapours have the effect of moderating the
bright images and improving their quality. When there is a driving
wind, and these heated vapours from the city are rolling rapidly past,
objects at once appear in a state of ebullition, and the work of
observation may as well be postponed. Smoke from neighbouring chimneys
is utterly ruinous to definition: a bright star is transformed into a
seething, cometary mass, and the planets undergo contortions of the
most astonishing character. Large instruments being more susceptible
to such influences—and, indeed, to atmospherical vagaries of all
kinds—are chiefly affected by the drawbacks we have alluded to; but
there are many opportunities when their powers may be fully utilized.
In sweeping for faint comets, or in other work (such as the observation
of nebulæ) where a dark sky is the first essential, a town station
has a manifest disadvantage because of the artificial illumination of
the atmosphere. But for general telescopic work the conditions do not
offer a serious impediment, especially if the observer is careful to
seize the many suitable occasions that must occur. The direction of the
wind relatively to his position and the central part of the city, will
occasion considerable differences to an observer who uses a telescope
in a suburban locality.
_Photography._—Upon this branch of practical astronomy not much will
be said in this volume, as it is rather beyond its scope, and possibly
also beyond the resources of ordinary amateurs, so far as really
valuable work is concerned. A reference must, however, be made to an
innovation which has deservedly assumed a very prominent place, and is
clearly destined to exert an accelerating influence on the progress of
_exact_ astronomy. At present it is impossible to foretell how far it
may be employed and extended, but judging from recent developments its
applications will be as manifold as they will be valuable. Photographic
records possess a great advantage over others, because they are more
accurate and therefore more reliable. They are pictures from Nature
taken by means free from the bias and error inseparable from mere
eye-estimations or hand-drawings. The latter are full of discordances
when compared one with another, and can seldom be implicitly trusted;
but in the photograph a different state of things prevails. Here we
have a faithful portrayal or reproduction of the object impressed by
itself upon the plate. Hence it can be depended upon, because there
has been no intermediate meddling either with its position or features
by what may be termed artistic misrepresentation. True, there may be
imperfections in the process; trifling flaws and obstructions will
invariably creep in wherever comparatively new and novel work is
attempted, but these will but little detract from the value of its
results. Photography is obviously a means of discovery as well as a
means of accurate record; for nebulæ and faint stars quite invisible to
the eye have been distinguished for the first time upon the negatives.
Those of our amateurs who intend working in this branch will find it a
productive one, and not decaying in interest; but the necessary outfit
will be expensive if thoroughly capable instruments are to be employed
in the service.
[Illustration:
LONDON STEREOSCOPIC CO. PHOTOMEZZOTYPE
STANMORE OBSERVATORY.
OUTSIDE VIEW]
_Publications._—The observer of to-day may esteem himself particularly
fortunate in regard to the number and quality of the astronomical
journals within his reach. Discoveries and current events receive
prompt notice in these, and readers are fully informed upon the
leading topics. Among the best of the periodicals alluded to are ‘The
Observatory’ (Taylor & Francis, London), ‘The Sidereal Messenger’
(Northfield, Minn., U.S.A.), and _L’Astronomie_ (Gautier-Villars,
Paris). The _Astronomische Nachrichten_ (Kiel, Germany) is a very old
and valued serial, and ‘The Astronomical Journal’ (Cambridge, Mass.,
U.S.A.) may also be favourably mentioned. The ‘Monthly Notices’ of the
Royal Astronomical Society and the ‘Journals’ of the Liverpool and
British Astronomical Societies contain many interesting materials.
‘Nature,’ ‘The English Mechanic,’ and ‘Knowledge’ are among the
English journals which devote part of their space to the science;
and the beautiful illustrations in the latter entitle it to special
recognition. It is evident, from this short summary, the amateur will
find that his literary appetite may be amply satisfied, and should he
desire a channel for recording his own work or ideas the publications
referred to offer him every facility and encouragement.
As to almanacks, the ‘Nautical’ which has been termed “The Astronomer’s
Bible,” includes a mass of tabular matter, some portion of which is of
utility to the amateur, but it does not give data which are to be found
in some other publications. I refer particularly to ephemerides of the
satellites of Mars, Saturn, Uranus, and Neptune, to the dates of max.
and min. of variable stars, to the times of rising and setting of the
Sun, Moon, and planets, to the epochs and positions of meteor-showers,
&c. The annual ‘Companion to the Observatory’ furnishes most of
these details, and ‘Whitaker’s Almanack’ and Brown & Sons’ ‘Nautical
Almanack’ each contain a large amount of serviceable information.
The latter, however, is chiefly devoted to topics connected with
Navigation, while ‘Whitaker’s Almanack’ is an extensive repertory of
general facts.
With respect to handbooks much depends upon the direction of the
observer’s labours, for he will obviously require works dealing
expressly with his special subject. As a reliable companion to the
telescope, Webb’s ‘Celestial Objects for Common Telescopes’ (4th edit.,
1881) is indispensable; as a work of reference, and one forming an
exhaustive conspectus of astronomical facts, Chambers’s ‘Descriptive
Astronomy’ (4th edit., in 3 vols., 1889) may be recommended.
Ledger’s ‘The Sun, its planets and their satellites’ is another good
descriptive work. The beginner will find Noble’s ‘Hours with a 3-inch
Telescope’ full of very instructive and agreeable material; while the
more experienced astronomer, requiring a masterly exposition of the
principles of the science, must procure Sir J. Herschel’s ‘Outlines’
(11th edit., 1871). In departmental work books of more exclusive
character will be necessary. Thus, students of solar physics will
want Young’s volume on ‘The Sun;’ observers of our satellite will
need Neison’s ‘Moon.’ Those who find double stars interesting should
get Crossley, Gledhill, & Wilson’s ‘Handbook’ and Chambers’s revised
edition of Admiral Smyth’s ‘Cycle;’ others working on variable stars
will need the Catalogues of Chandler and Gore. Jovian phenomena are
well represented in Stanley Williams’s ‘Zenographic Fragments.’ Comets
have been fully treated of in works by Cooper, Hind, and Guillemin;
while to the observer of eclipses Johnson’s ‘Eclipses Past and
Future’ is a valuable guide. Everyone interested in nebulæ will of
course require Herschel-Dreyer’s ‘General Catalogue,’ containing 7840
objects and published by the Royal Astronomical Society in 1888. As
to planetary observations, the several works of Webb, Chambers (vol.
i.), and Ledger, first cited, supply a large amount of detail, almost
obviating the necessity for further books.
_Past and Future._—Observers and telescopes go on increasing day
by day, and the future of astronomy has a most brilliant outlook.
Photography has latterly effected a partial revolution in observation,
though it can never entirely supersede old methods. Spectrum analysis,
too, has formed a valuable acquisition during the last quarter of a
century. With the new and refined processes, and with the gigantic
instruments which have been erected, we may confidently anticipate
many additions to our knowledge, especially in regard to very small
and faint bodies which the inferior appliances of previous years
have failed to grasp. And it is certain that some of the presumed
discoveries of past times must be expunged, because not verified by the
more perfect and powerful researches of a later date. Let us place in
parallel columns (1) a few of the suspected objects thus to be erased,
and (2) some of those which the future will probably add to our store:-
(1.) (2.)
Satellite of Venus. Satellites of Uranus and Neptune.
Vulcan. Ultra-Neptunian Planet.
Active Volcanoes on the Moon. Changes on the Moon.
Detached cusps of Venus and Mercury Rotation of Mercury, Venus,
indicating high mountains. Uranus, and Neptune.
Rings of Uranus and Neptune. Minor Planets.
Multiple companions to Polaris Periodical Comets.
and Vega. Nebulæ and Double Stars.
Whatever may be the direction of future enquiries or the departures
from old and tried methods, ordinary amateurs with small instruments,
though handicapped more heavily as regards the prospect of effecting
discoveries, may yet always be expected to accomplish useful work.
Even to him who simply makes the science a hobby and a source of
recreation in a leisure hour after the cares of business, the sky never
ceases to afford a means of agreeable entertainment. He may neither
achieve distinction nor seek it; but this he will assuredly do—gain
an instructive insight into the marvellous works of his Creator, and
acquire a knowledge which can only exercise an elevating tone to his
life. The observer who quietly, from his cottage window, surveys the
evening star or the new Moon through his little telescope often finds a
deeper pleasure than the proficient astronomer who, from his elevated
and richly appointed observatory, discovers new orbs with one of the
most powerful instruments ever made.
_Attractions of Telescopic Work._—In concluding our comments we may
briefly refer to the importance and pleasure attached to telescopic
work, and the growing popularity of observation in the attractive and
diverse field of astronomy. A telescope may either be employed as an
instrument of scientific discovery and critical work, or it may be
made a source of recreation and instruction. By its means the powers
of the eye are so far assisted and expanded that we are enabled to form
a clearer conception of the wonderful works of the Creator than could
be obtained in any other way. Objects which appear to natural vision in
dim and uncertain characters are resolved, even in telescopes of the
smallest pretentions, into pictures of well-defined outlines containing
details of configuration far exceeding what are expected. And it is
entirely owing to the exact measurements obtained under telescopic
power that many of the most important problems of astronomy have been
satisfactorily solved. To this instrument we are indebted, not only
in a great measure for our knowledge of the physical features of many
celestial bodies, but also for the accurate information we have gained
as to their motions, distances, and magnitudes. Apart from this it is
capable of affording ample entertainment to all those who are desirous
of viewing for themselves some of the absorbing wonders of astronomy as
described in our handbooks. And a demonstration of this practical kind
is more effective than any amount of description in bringing home to
the comprehension of the uninitiated the unique and picturesque side of
astronomy.