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KEYGUIDE.TXT
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Coeli (TM)
A Guide to Mouse and Key Functions
In which we present Coeli's functions alphabetically and offer
hints and tips on more effective use of the program. Upper
case letters, such as [A], require you to hold down [shift]
while pressing the key.
Where an alternative is given, this is usually for the benefit
of users of the Scandinavian / Finnish keyboard layout.
Users of national keyboards other than the UK/US or Finnish
configuration may be unable to access a few of Coeli's
functions. There are two alternatives if this is the case:
1) Register now, and you will receive a copy tailored to your
preferences.
2) Use DOS or Windows to temporarily change your layout to the
U.S. configuration, returning to your national keyboard setup
after you quit Coeli. You will be able to set this up in a
batch file (See a good DOS or Windows guide for how to
accomplish this if you are unsure).
Keypresses
[a]
Switch auto-resolution on/off.
Default setting: on.
Auto-resolution exists to save you the trouble of manually
altering both the number and apparent brightness of stars
displayed in a given field at a given magnification.
We all know that when we turn a pair of binoculars on the
heavens, we see many more stars than the naked eye can
resolve; also, that the brighter ones look brighter still.
When you zoom in with Coeli's [z] key, auto-resolution
attempts to achieve a similar effect while keeping
proportional the ratio of stars displayed to the chosen
magnification.
Compromises and personal preferences were inevitable here,
which is why you can turn it off. It will be far more
satisfying to achieve balance for a given starfield manually,
but it demands time and practice. Our settings are a good
compromise. Experience and experimentation will pay dividends
with this function.
[A]
Adjust the screen's aspect ratio.
You needn't bother with this if Coeli first presents you with
a more or less circular representation of the sky.
If your monitor or other software has necessitated adjustments
to the horizontal and vertical dimensions of your display, you
can press [A] repeatedly within Coeli until you acquire a view
of the correct proportions. This is a cyclic control, so if
you overshoot just keep pressing until the desired ratio comes
round again.
[b]
Brighten all stars by enlargement.
Auto-resolution ([a]) automates this for you.
Creates the effect of an increase in magnitude. Use of this
key is part of the process of manually 'perfecting' a
starfield. Only experience and experimentation will avail you
here.
The complementary function is [d].
[B]
Brighten all stars by 'whitewashing' the colour palette.
Pressing this key will progressively drain each star of colour
until eventually it appears white. The opposite of [D] below.
Only individual taste will dictate when, or whether, you use
this function.
Restore Coeli's original colours instantly with [R].
[c]
Centre the display on the currently selected star.
Arguably the most important of all Coeli's key functions. It
is the principal means by which your view is moved about the
visible sky-area. Use the stars as 'stepping stones' as you
shift your gaze. The technique goes like this: click on the
first star, centre the display, click on the next star, centre
the display, and so on.
It is, however, important to note that centering a star in
this way does not centre the projection on this star, merely
the display. For the greatest accuracy in depicting the
immediate surroundings of a given star, it is necessary to
make that area the centre of projection, the more so if a
horizon-view has been specified. To centre the current
celestial projection on a desired star, Coeli provides the
traverse and elevation tools as described under [arrow keys].
[C]
Switch rise/set/transit alarms on/off.
Default setting: off.
Coeli provides you with an automatic early warning of optimal
/ challenging observing conditions for any given star. Suppose
you intend to observe a heliacal rising of Sirius one early
autumn morning. First use the [i] key to switch on continuous
information readouts, then select Sirius either by
right-clicking on it or using [f] to locate the star for you.
Now, provided you have activated rise/set/transit alarms with
the [C] key, you can get on with something else until Coeli
audio-visually advises you that the moment is right for the
observation. You can similarly use the function to warn you
when a desired star is approaching the meridian (transit), an
ideal time to turn a telescope on it, or when it is about to
set (another observational challenge).
However, these alarms can be a bore when you don't need them,
especially when zooming and centering, so [C] also provides
the means to turn them off.
[alt]+[c]
Switch comet displays on/off
Default setting: on
In the shareware release, Hale-Bopp is the only comet
available, and then only during its period of perihelion.
Fully registered versions of Coeli will include more comets
(Hyakutake, Halley etc), and in a future release there will be
the facility to add and remove comets along with their orbital
elements at will.
Please bear in mind that it is always preferable to switch off
comets if none are currently visible, as this will improve
program responsiveness immeasurably. Indeed, in the case of
Hale-Bopp in the shareware version, this is taken care of
automatically.
[d]
Diminish ('shrink') all stars.
The opposite of [b].
Creates an effect of dimming or reduction in magnitude.
[D]
Deepen each star's perceived colour.
The opposite of [B].
This tends to bring out a star's 'character' or essential hue,
emphasising colour at the expense of brilliance, and as such
is likely to be used more than its complementary function
(which merely washes out colour). Again, whether any use is
found for this keypress is a question of individual taste.
As regards spectral type and colour index, it makes for easier
comparison between adjacent stars. It is also useful for
bringing out colour on the DSTN screens of notebook computers.
Restore Coeli's original colours instantly with [R].
[e]
Face east and update all star positions.
An alternative to using the [left/right] arrow keys, this will
orientate you instantly to one of the four principal compass
points. Your view's elevation is not affected.
East is on the left when Coeli starts up.
[E]
Show / hide the ecliptic line.
Default setting: hidden.
A simple dotted guideline in grey is drawn. At higher
magnifications best switched off, as it only increases
Coeli's response-time (though not by very much).
The ecliptic is the path the sun, moon and major planets
appear to follow in their 'peregrinations' through the
heavens. The constellations which straddle the narrow band
north and south of the ecliptic are the 12 astrological signs
of the Zodiac.
[f]
Find individual star.
Conveniently locates any star, either by Bayer, Flamsteed,
Variable star reference, or common name.
First decide by what system you wish to identify your star.
To locate by Bayer nomenclature ( ie. Greek letter ), simply
click the <right> mouse button after highlighting the desired
Greek letter, followed by the <left> mouse button after
highlighting the desired constellation. It is possible to
achieve this vice versa, ie. first designating the
constellation and then the Greek letter, but it is as well to
choose a method and stick to it.
Locating a star by Flamsteed number or Variable star reference
is only different in that you may need to click more than once
with the <right> button to form the required multi- digit or
letter combination.
To find a star by name, click the <left> mouse button after
highlighting the entry 'common names' at the end of the
constellation list. You will then be prompted to enter the
star's initial letters via the keyboard. Notice that Coeli
saves you the trouble of capitalising the initial. If you are
unsure of the correct spelling, pressing [backspace] will
bring up the full list of stars whose common names Coeli is
currently aware of.
When you recognise the name you wish to locate, slowly type
its initial letters as displayed on the list until this single
name is highlighted. Finally, press [ return ] or [ enter ] to
confirm your choice. If you make a mistake, use [backspace] to
expand the list again. The things to remember are that a
unique name must ultimately be highlighted, and that [ enter ]
must be pressed to confirm the name as your selection. [ esc ]
will allow you to back out of the operation unconditionally.
If Coeli's search succeeds, the star will be centred in your
display adjacent to the mouse monocle, accompanied by all
relevant readouts.
[F]
Find a constellation.
This is simplicity itself. Just use the mouse to highlight the
name of the constellation you wish to locate, and press the
<left> button. The constellation will be spotlighted, and the
screen centred on its principal star. To return the display to
a normal state (ie. all stars illuminated), press [F] again
and select the item 'Constellation not designated' at the end
of the list.
This function is most useful for appreciating the true extent
of each star-group, something which constellation lines often
fail to reflect.
[g]
[G]
Brighten/darken text colour.
Simply a matter of taste versus dark-sensitivity.
It is as well to enable continuous information readouts with
the [i] key in order to be instantly apprised of the result.
[h]
Call up the quick help screen. This takes the form of a list
of available key-functions, and a brief reminder of what each
does. You will also see a copyright message and find the
address of Swimming Elk Software.
In the shareware version, there will be a short (3 second)
delay while our address flashes. We want you to know that we
exist!
[H]
Horizon view.
The centre of your personal view (your line of sight) will be
directly ahead. In other words, this key centres the current
celestial projection at zero degrees altitude.
Please be aware that, although a horizon view is the one which
most approximates the experience of standing and casually
viewing whatever quarter of the heavens confronts you, it is
also the one which introduces the most distortion into the sky
representation as a whole. The distortion is of course most
pronounced at the field's extremities: the top, bottom, and
edges. If you use this viewpoint a lot, and you probably will,
please remember to make liberal use of the 'traverse tool' to
bring the required sector of the 360 degree horizon into the
centre of your field. See [arrow keys] for further details.
Certain projections (the stereographic, for example) are
better at coping with edge-distortion, but do this by
compromising in other areas. The stereographic will always
render the shapes of the constellations more or less
faithfully, but with extreme enlargement at the limits. It is
nevertheless probably the best projection to select when
viewing the horizon closely, especially with constellation
lines.
In many situations, and for accuracy, an intermediate view
between zenith and horizon is more effective. You will of
course eventually reach a horizon view by using the 'elevation
tool', but [H] is the fastest way to achieve it.
[i]
Switch continuous information readouts on or off.
Default setting: off
With this function set, textual information displays will not
be cancelled by map-redrawing during real time updates or
while advancing / retarding the simulation's date and time.
Changes in coordinates as the earth rotates will be more
readily noted, but zooming / unzooming will be slower.
Enabling this setting is advisable if you wish to use the
rise/set/transit alarms to best advantage, as described under
the [C] heading.
[I]
Inverted image on / off.
Default setting: off
Inverts the display in the y-axis. Invaluable for telescopic
observers. Please refrain from using the elevation tool with
this function set: it can get confusing!
[alt]+[i]
ImageIcons on/off
default setting: on
ImageIcons, as their name suggests, are iconised images of
celestial objects (primarily planets & DSOs). In the shareware
release, the DSO ImageIcon is generic - a spiral galaxy,
actually M100 - but in fully registered copies of Coeli the
icon will either be a photograph of the object itself (in the
case of Messier), or a true image of the object's type or
class.
Please note that, due to dithering effects, ImageIcons are at
their best in the higher resolutions (above 800x600, mode 3).
And, of course, it scarcely needs adding that planet icons are
not shown to scale!
Tip: if you'd like a different generic ImageIcon in the
shareware version, simply rename your Messier .icn file of
choice to 'g_spiral.icn'. For example, suppose you preferred
the Andromeda Galaxy - M31 - as your generic ImageIcon: just
COPY 'M31.icn' to 'g_spiral.icn', leaving the original M31
file intact.
[j]
Star designation labels on/off
Default setting: off
You have the choice, as with [N], of a completely 'natural'
display of the heavens or a map-like labelling. This key
switches Bayer designations ( Greek letters ) and Flamsteed
numbers on or off.
[k]
[K]
Turn Sunshine/moonshine on / off
Or Brighten/darken sky
Default setting: sunshine/moonshine off
The [k] key's dual function depends on whether you have
enabled solar/lunar displays with [S].
With solar/lunar displays active, this key will alternate
between a realistic reflection of the amount of daylight or
moonlight present and a completely dark sky. The former will
be an invaluable aid in gauging the likelihood of favourable
observing conditions without actually having to venture
outside. However, during daylight hours Coeli's stars will be
almost as hard to observe as the real ones, which is why we
have made it easy to revert to 'perfect' conditions!
With solar/lunar displays inactive, [k] manually brightens and
[K] darkens the sky background. This mode may be of help in
maximising contrast on certain types of LCD laptop displays.
[l]
Location Browser.
One of Coeli's special features is the ease with which it is
possible to 'travel the world' and observe the sky from any
earthly position. The Location Browser's operation is so
simple, it scarcely needs explaining. You simply move the
mouse-monocle around the world map until you're where you want
to be, whether this happens to be Tierra Del Fuego or the Kola
peninsula. Click the <left> button to look up once again and
see the heavens as they appear from the place you have chosen.
A useful display of latitude/longitude and (putative) time
zones will accompany your peregrinations as you move the mouse
over the continents.
As mentioned in the manual, potential confusion might arise if
you were previously centred, for example, on a northern
circumpolar star and then suddenly transported yourself to,
say, South Georgia. Remember first to click on a star
somewhere in the middle of your new sky before performing zoom
/ unzoom / centering operations.
[L]
Switch daylight-saving adjustments on/off.
Default setting: on
Many of us set our clocks forward or back in the autumn and
spring, which is why this adjustment is built into Coeli. But
you may not need it if you live near the equator, or if you
have 'travelled' there using the Location Browser.
When you register your copy of Coeli, we will set your precise
preferences in this regard permanently.
[m]
Advance Coeli's date by (x) months.
Coeli can situate you in time as easily as in space. [m] is a
cyclic control, so if you keep pressing you will eventually
end (start?) up at January again. To help you keep an eye on
your progress, 'Observer info' always pops up when you press
this key.
Using the numeric keys (x) can be set anywhere from 1 to 9
months, thus permitting large 'single step' advances.
[M]
[alt]+[m]
Display the position of all objects listed in Messier's
catalogue & the most notable of those from the NGC.
Since Coeli's primary function as planisphere is to guide you
with ease and practicality around the constellations, this key
is an 'extra'. But a great deal of Messier is within the reach
of binoculars, a small telescope, and even the naked eye, so
there is every justification for including these 'deep sky'
objects.
Entries from the more extensive NGC list will appear if you
press [alt] and [m].
An ImageIcon of the DSO or its type will appear if this
setting is active (as it is by default). Note that in
shareware releases the image is a generic spiral galaxy but
in registered copies the ImageIcon will reflect the object's
true type. Indeed, in the case of Messier, it will be an
iconised photo of the object itself.
[n]
Face north and update all star positions.
An alternative to using the [left/right] arrow keys, this will
orientate you instantly to one of the four principal compass
points. Your view's elevation is not affected.
North is in the screen's upper portion when Coeli starts up.
[N]
Label stars with their common names.
Default setting: off
If the colour-option is set, each label will reflect the
star's spectral type: thus 'Aldebaran' will print in bright
orange, 'Procyon' in white, 'Capella' in pale yellow etc.
Note additionally that this option is tied to magnitude and
magnification, so the closer you zoom, the more labels will
appear.
There will be more names to label if you put a 'Y' on the
command line as explained under 'Loading and running' in the
manual.
[o]
Switch 'observer info' on or off.
Default setting: on
As you know, Coeli reserves a textual readout for each corner
of the screen. This one appears in the top right, and conveys
useful information pertaining to you, the observer of Coeli's
skies, as follows: Your name, if known / your home or
observing location, if known / your present latitude and
longitude / your international time zone, if known, otherwise
your putative time zone / daylight-saving settings / the
Gregorian date ( international day/month/year format),
changeable as you advance or retard Coeli's clock / the
Julian date / your present line of sight expressed as traverse
('Facing' + compass point) and degree of elevation ('View') /
and finally, Coeli's current mode, either Temporal ('Real
time') or Map.
[p]
Switch between Temporal Mode ( real time ) or Map Mode.
Default setting : Temporal Mode.
Freezing Coeli's display can have certain advantages:
suspension of real-time star updates will ensure that every
star always appears where it should, even during extended
zoom/ unzoom/ centering operations. What you are now observing
is essentially a static map for the given time and place.
Most functions available in Temporal Mode will still be
accessible in Map Mode, including the Location Browser.
If you forget which mode you are currently in, the simplest
way to clarify the situation is to bring up the time-display
with the [t] key. With Coeli's clock paused, the display will
be greyed out, 'frozen' at the hour when you initiated Map
Mode. Alternatively, you might bring up the 'observer info'
readout in the top right hand screen corner with [o].
Pressing [p] again will return you to real-time updates
(Temporal Mode).
[P]
[alt]+[p]
Planet displays on/off.
Default setting: on
The nine planets are now an integral part of Coeli. With
planets enabled, you can use the mouse monocle with a left or
right click to obtain up-to-the-minute readouts in exactly the
same way as for stars.
Clicking on a planet with the mouse will also result in an
ImageIcon of the selected planet appearing on the left of the
display, provided an appropriate icon is available.
Alternate between planet names and symbols by pressing [alt]
followed by [p].
At present, you may not [centre] or [zoom] on a planet.
[Q]
[q]
Initialise Sky Quiz.
Get the next quiz question.
As far as we're aware, Coeli is unique in offering the luxury
of a fully-fledged online quiz for consolidating your
knowledge of the heavens. It must be stressed that Sky Quiz is
in no way sequestered from the rest of Coeli: there is no
'quiz page' to move off to - the sky will still lie before
you, the stars will still move in their courses, you can
utilise all Coeli's functions. Sky Quiz is integrated,
seamless.
You press [Q] to instruct Coeli to begin the quiz. Thereafter,
[q] will prompt Coeli to ask you a question on the sky-area
currently under display. The subject is tied to your field of
view, so depending on your needs, the question might concern a
single constellation, even a single part of a constellation,
or the entire sky. This question 'stands' until you answer it.
You can perform most other viewing functions in the interim,
although Coeli will try and prevent you from cheating.
You can have as many attempts as you like at answering the
current question, even indefinitely, or until you hit upon the
right response. After all, it's only mouse-clicks. Coeli will
adjust your score downwards in accordance with the number of
tries, but you'll get something provided you finally hit on
the right answer.
If you cannot answer the current question, pressing [q] again
will inform Coeli and get you another.
Sky Quiz is not available in the shareware release. It is a
bonus. We believe it is your best reason for registering
( apart from lifetime support by mail, total personalisation,
and complete absence of reminder screens ), as you'll be
astonished at how quickly this method gains you familiarity
with the stars. Through Sky Quiz, you will eventually 'read'
the sky as effortlessly as you can read this.
[r]
Coeli's online registration facility.
If you are not a registered Coeli user, [r] for you means
'Registration'.
At any time, simply press [r] to see how our convenient
registration routine works. You are free to abort with [ESC]
whenever you wish.
What happens, briefly, is that you are asked to fill in some
details onscreen, principally your name, address, preferred
method of payment, and as much as you can tell us about your
geographical location and various related matters such as time
zone and local daylight-saving arrangements. Don't worry if
you haven't a clue about the latter. Either come back to them
after some research or let us do the hard work.
During the registration process you are free to leave as many
questions blank as you wish (even all of them). Coeli will
save a copy of your form as it stands under the name
REGISTER.FRM in your current disk directory, where you can
edit, peruse, or delete it at will. Ideally, you will want to
print it out straight away. Coeli will do this for you too.
We think registration is worth your while for the Sky Quiz
alone, but you'll discover yet more exclusive incentives when
you contact us. We look forward to hearing from you.
Maybe you'd like to register online right now?
----------------------------------------------
- Just point your Web browser at
http://ourworld.compuserve.com/homepages/coeli/homepage.htm
and follow the link to the special secure order forms of
PsL or Share-It!.
We even welcome pre-registration enquiries. So just drop us a
line or E-mail and we'll let you know we exist!
[R]
Restore Coeli's original colour palette.
Useful if you make a mess of [B], [D], [K], or [G].
[s]
Face south and update all star positions.
An alternative to using the [left/right] arrow keys, this will
orientate you instantly to one of the four principal compass
points. Your view's elevation is not affected.
South is the compass direction you face when Coeli starts up,
and is in the screen's lower portion.
[S]
Turn solar / lunar displays on or off.
default setting: on
In terms of Coeli's textual readouts, this means the bottom
right corner of your screen. With Sun and Moon enabled, this
section will convey a plethora of useful data which includes
solar and lunar co-ordinates, phase of the Moon, sunrise,
sunset, hours of darkness and astronomical twilight.
In terms of Coeli's sky, you will either see or not see the
solar and lunar discs, depending on the setting of [S].
Dynamic brightening of the sky background is directly tied to
this setting. If you switch solar/lunar displays off, [k], [K]
will simply allow you to alter the sky colour manually. But if
they are switched on, both sunshine and moonshine will be
simulated. You will be able to watch the dawn, and await with
anticipation the approach of night.
[t]
Display the simulated time of day.
This is a cyclic control with four settings, and three
varieties of time are available: Local (L), Greenwich (G), and
Local Sidereal (S). The fourth setting is the default, namely
no time display.
[T]
Track current star.
Simply stated, this function will attempt to keep your object
of interest at the centre of Coeli's display when in Temporal
mode. A small red 'T' will flash in the bottom left corner to
remind you that tracking is active. Again, no good for screen
saving.
Especially useful if the magnification is high, when otherwise
stars might 'hop' out of view during a screen update.
Currently for use only with stars.
[u]
Advance Coeli's clock by 1 sidereal day.
The reason for wishing to advance by this unit may not be
immediately apparent. A sidereal day is slightly less than a
solar day, being approximately 23h 56m. It is the time taken
by the STARS to return to their exact positions of the night
before. You thus have a way of holding the stellar backdrop
steady while you watch the bodies within our Solar System
shift against it.
The fleetest mover is of course the Moon, due to proximity,
followed by the Sun and the inner planets, whose 'dance' can
be very instructive to watch. The outer planets shift at a
much more sedate pace.
For faster animation, a wide angle of view is necessary,
preferably one encompassing the entire celestial sphere. A
zoom factor well into negative figures is in order. Speed up
still further reducing the visible number of stars with [-].
Between 200 and 1000 should be ample for this effect,
depending on processor speed, since it is not the stars
themselves which interest us here.
Set the ecliptic line with [E] to better trace the path
followed by the Sun, Moon, and planets with the passage of
time.
This is one function where the lower resolutions come into
their own: the 'frame rate' is greatly increased in mode 2 and
below.
Return to your starting date by pressing [HOME]. This will
cancel your current zoom, colour, and location settings, so
make sure you have stored them with [F7] if they are important
to you.
[w]
Face west and update all star positions.
An alternative to using the [left/right] arrow keys, this will
orientate you instantly to one of the four principal compass
points. Your view's elevation is not affected.
West is on the right when Coeli starts up.
[x]
Unzoom. Reduce magnification.
Unzooming widens your field of view. If you keep zooming out,
you will eventually have the entire sky (both hemispheres)
projected before you. This is of course highly unrealistic,
worse than looking through the wrong end of a telescope, but
extremely useful for finding your way around the heavens
quickly.
Auto-resolution will continue to ensure the correct ratio of
stars to view-field, so this can be a nice way of reducing the
sky to its essentials.
[X]
Switch double accuracy on/off.
Default setting: off
For that final bit of reassurance, Coeli can incorporate extra
precision in all computations, at the expense of a certain
amount of speed when functions like [space] and [enter]
refresh the display.
We recommend you enable double accuracy when in Map Mode. If
your PC is a DX4 or Pentium, it is preferable to switch this
function on at the start of your session and keep it active
throughout.
[y]
Advance Coeli's clock by (x) years.
Coeli can situate you in time as easily as in space. This key
moves you forward by (x) years. To help keep an eye on your
progress, 'Observer info' always pops up when you press it.
Using the numeric keys (x) can be set anywhere from 1 to 9
years, thus permitting large 'single step' advances.
[Y]
Retard Coeli's clock by (x) years.
Coeli can situate you in time as easily as in space. This key
moves you backward by (x) years. To help keep an eye on your
progress, 'Observer info' always pops up when you press it.
Using the numeric keys (x) can be set anywhere from 1 to 9
years, thus permitting large 'single step' advances.
[z]
Zoom. Increase magnification.
Zooming narrows your field of view. It achieves what a good
telescope can: the brighter stars are brighter still and a
myriad appear that weren't discernible before. Auto-resolution
balances their number and their relative brilliance.
Coeli's zoom is powerful enough to separate close doubles like
Castor and Mizar, to name but two, but don't be fazed by
anomalous effects at high magnifications: these are computer
'artifacts'.
The manual warns you not to overdo zooms / unzooms and it
bears repeating here. For your convenience and instruction, no
limit has been set on Coeli's magnification, so there is also
plenty of room for abuse. We cannot be held responsible for
the latter's unforeseeable results.
[Z]
Zenith view.
The view presented when Coeli starts up. In the centre are the
stars directly above your head; the 360 degrees of your
horizon lie on the 'bright circumference', delineated in blue
if you have set your horizon line with the [_] key; on the
outer or green circumference lie the unrisen (and perhaps
unrising) stars of the opposing hemisphere.
The least realistic, due to the horizon's extreme curvature,
but the best all round picture of the heavens, and the one
used by all (real) planispheres.
A zenith view offers the least overall distortion of your
visible sky area, and hence the most compromise, although the
latter is distributed evenly. The two projections best
tailored to a zenith viewpoint are the equal-area and
equidistant (Coeli's default projection).
If you advance the hour continuously on Coeli's clock, the
zenith view most effectively shows you the stars as they wheel
about the celestial poles, Polaris and Ursa Minor in the
north, Octans in the south.
[']
Mirror image on / off.
Default setting: off
Reverses the display in the x-axis, showing the sky as if in a
mirror. Invaluable for telescopic astronomers. Please refrain
from using the traverse tool with this function set: it can
get confusing!
[@] or
[ä]
Turn atmospheric effects on / off.
Default setting: off
By 'atmospheric effects' we mean specifically the two
phenomena atmospheric refraction and atmospheric extinction.
In practical terms, atmospheric refraction causes
discrepancies between the position of the stars as viewed in a
vacuum and that of the same stars as viewed through the
distorting 'lens' of our atmosphere. The difference at the
horizon, depending on temperature and atmospheric pressure and
thus also on height above sea-level, can sometimes amount to
several minutes of arc. Atmospheric refraction becomes
negligible as we raise our eyes toward the zenith.
With atmospheric extinction, Earth's atmosphere causes a
star's apparent magnitude (brightness) to diminish in
proportion, again, to its proximity to the horizon. On Coeli's
textual readout the amount of reduction in brightness ( a
positive figure ) follows the magnitude value when atmospheric
effects are switched on. This effect can be very pronounced.
Antares viewed from Finland is a different creature altogether
from the Antares seen from Andalusia!
The reason you can ignore the first atmospheric effect for all
practical purposes is that relatively few of us, unless we
sail the high seas, climb mountains, or fly, are granted a
pristine unimpeded view of a flat horizon, where refraction is
most pronounced.
[_]
Show/hide the horizon line.
Default setting: shown
The dark green 'unrisen' stars do a good job of delineating
a contrast between those below and those above the horizon,
but for extra emphasis, this blue horizon line is available.
It will slow zooms / unzooms / calculations down minimally.
One of those functions which it is advisable to disable if you
require peak responsiveness. Not particularly CRT-friendly,
either.
[/]
Draw Altitude/Azimuth graticule (grid lines).
This function draws a grid, but does not set it permanently.
Screen updates will erase it.
[?]
Show/hide altitude/azimuth graticule (grid lines).
Default setting: hidden
Not just a question of aesthetics, a grid can also be
instructive in revealing the underlying properties of the
selected projection model ( degree of distortion etc) and for
basic orientation. However, setting the grid lines is not
recommended during operations such as zoom / unzoom / centre,
while changing from one projection to another, or when using
the traverse and elevation tools, since it drastically reduces
the program's responsiveness.
An altitude/azimuth grid remains stationary while the stars
appear to move behind it, thus reducing Coeli's effectiveness
as a means of preventing burn-in to the cathode ray tube
(CRT). Simply put, if you leave the grid on, Coeli will not
function effectively as a screen-saver.
[\] or
[ö]
Draw schematic constellation lines.
The first press will load Coeli's line data from disk into
memory, and any subsequent call to this function will result
in an instant display. The relevant file is called COELINE,
and you can alter it if you've the inclination. See details at
the end of COELINE itself.
The staple fare of popular star atlases and Daily Telegraph
style 'night sky guides', constellation lines appear to be an
essential ingredient in most planetaria. 'Joining the dots'
may occasionally help a neophyte, but more often confuses the
issue, many if not most of the accepted patterns bearing
little true resemblance to the objects they are meant to
represent. It is probably far preferable for the aspirant
observer to allow the star groups to settle into their own
patterns, better remembered because self-invented.
Coeli's [F]ind constellation facility will 'spotlight' a group
of stars against a neutralised star background, arguably a
more efficacious means of discerning the extent of a
constellation and its overall form.
[|] or
[Ö]
Switch constellation labels on/off.
Default setting: on
Note: the Sky Quiz will refuse to commence unless you disable
this option.
[#]
Include Flamsteed and Yale Catalogue numbers on readouts.
Default setting: off
Normally the star designation readout (top left) shows only a
Bayer designation (Greek letter and Latin genitive). If the
star does not possess one, its Flamsteed number is the next
candidate for display. Only in the absence of both will the
star's Yale Catalog number be output.
In rare circumstances, you might need to know all of the
above, and that is the [#] key's purpose.
[,]
Retard Coeli's clock by (x) hours.
Coeli can situate you in time as easily as in space. This key
moves you backward in time by (x) hours. To help keep an eye
on your progress, 'Observer info' always pops up when you
press it.
Using the numeric keys (x) can be set anywhere from 1 to 9
hours, thus permitting large 'single step' advances.
[.]
Advance Coeli's clock by (x) hours.
Coeli can situate you in time as easily as it does in space.
This key moves you forward in time by (x) hours. To help you
keep an eye on your progress, 'Observer info' always pops up
when you press it.
Using the numeric keys (x) can be set anywhere from 1 to 9
hours, thus permitting large 'single step' advances.
[<]
Retard Coeli's clock by (x) days.
Coeli can situate you in time as easily as it does in space.
This key moves you back (x) days. To help you keep an eye on
your progress, 'Observer info' always pops up when you press
it.
Using the numeric keys (x) can be set anywhere from 1 to 9
days, thus permitting large 'single step' advances.
[>]
Advance Coeli's clock by (x) days.
Coeli can situate you in time as easily as in space. This key
moves you forward (x) days. To help you keep an eye on your
progress, 'Observer info' always pops up when you press it.
Using the numeric keys (x) can be set anywhere from 1 to 9
days, thus permitting large 'single step' advances.
[[] or
[;]
Retard Coeli's clock by (x) minutes.
Coeli can situate you in time as easily as in space. This key
moves you back (x) minutes. To help you keep an eye on your
progress, 'Observer info' always pops up when you press it.
Using the numeric keys (x) can be set anywhere from 1 to 9
minutes, thus permitting large 'single step' advances.
[]] or
[:]
Advance Coeli's clock by (x) minutes.
Coeli can situate you in time as easily as in space. This key
moves you forward (x) minutes. To help you keep an eye on your
progress, 'Observer info' always pops up when you press it.
Using the numeric keys (x) can be set anywhere from 1 to 9
minutes, thus permitting large 'single step' advances.
[*]
Change SVGA graphics mode.
You will be prompted to enter a mode number from 0-5, and
Coeli will immediately attempt to set it. No checks are
currently performed as to whether your graphics hardware will
support the requested resolution. In the event that it does
not, either an error message or system lock-up will ensue,
depending on the severity of the condition. In whichever case,
it will be necessary to restart Coeli.
Coeli's 5 possible SVGA resolutions (all 256 colour) are as
follows:
(1) 640 by 400 pixels
(2) 640 by 480 pixels
(3) 800 by 600 pixels (default mode)
(4) 1024 by 768 pixels
(5) 1280 by 1024 pixels
Mode (0) is the conventional VGA/MCGA 320x200 pixels at 256
colours and is not recommended, being far too coarse-grained
for most of Coeli's advanced functions. It is a last resort
only, although workable if merely viewing the stars and
performing simple zooms etc.
Tip for Windows 95 users: multitask with Coeli by pressing
[alt]+[enter] when this function is waiting for input. Return
to full screen display by clicking the expand icon in the
toolbar and then entering your choice of resolutions (1-5) as
normal.
[arrow keys]
'elevation tool' and 'traverse tool'
The [up/down] arrow keys activate the elevation tool. With its
help your line of sight may be adjusted to within a degree in
the vertical plane. The elevation tool takes the form of a
'sighting rectangle' through which pass the stars as you move
it up or down. Use this tool to help you centre the projection
precisely on a given region or heavenly body in conjunction
with the traverse tool.
The [left/right] arrow keys activate the traverse tool. With
its help your line of sight may be adjusted to within a degree
in the horizontal plane. With a zenith view, this tool will
most resemble the hand of a clock: the sighting rectangle
(elevation 90) in the middle of your visible sky while the
'hand' sweeps the 360 degrees of your horizon.
From viewpoints intermediate between zenith and horizon, the
'hand' becomes a vector capped by the sighting rectangle: the
greater its extent, the higher your sights are raised. With a
horizon view, only the sighting rectangle will be visible,
since your elevation is zero.
When you use the traverse tool, you are 'turning in place' to
face whichever sector of the horizon you have chosen.
Along with the moving line and sighting rectangle will appear
changing readouts of the degree of elevation or traverse
(azimuth) currently set. In the case of traverse, the compass
direction will also be indicated (S,SSW,SW,W through N, and
back to S again).
Each tool is used separately, and [enter] or [space] should be
pressed between each 'swing' to draw the sky to the new
viewpoint, the latter if you plan to increase magnification
(zoom).
'Swing' speed will depend on your system's key-repeat settings
and the clock rate of your processor. We recommend you set the
former to their maximum responsiveness, the easiest way being
via the Windows Control Panel under Keyboard.
[enter]
[return]
Refresh the display of visible stars.
This is considerably quicker than refreshing with [space]
which recalculates the position of every star in memory
regardless of whether it is currently visible. [enter] merely
re-computes the positions of stars you can see at your present
magnification.
[space]
Recalculate every star position and refresh the display.
This should be done whenever you have completed a series of
zooms, changed the projection, or altered your viewpoint in
some way, merely as a precaution against possible inaccuracies
resulting from these operations.
Coeli's star co-ordinates are being recalculated continually
as a matter of course, but at times this mechanism is allowed
to slip out of step with certain functions for the sake of
responsiveness. The two operations most likely to put the
calculations out of sync are [zoom] and [change viewpoint].
Unzooming and centering are quite safe in this regard.
For pinpoint stability, it is often advisable to activate
[double accuracy] and enter Map Mode, where the positional
update mechanism - Coeli's clock - will be frozen. A first
press of [space] will then suffice for the entire session,
unless you substantively change viewpoint.
Alternatively, when in Temporal Mode, you might simply prefer
to let Coeli catch up. Updates occur automatically every two
minutes or so.
[backspace]
Return to your previous viewpoint (Undo).
This 'undo' feature is limited to your terrestrial
orientation. Its primary purpose is to back out of presses of
the following: [ l,n,s,e,w,H,Z ], all keys which drastically
alter your viewpoint in some way. You are thus permitted to
check another facing while retaining present settings.
It may be usefully employed as a toggle for comparing two
widely differing skies. From your current position, press [l]
to bring up the location browser and select, say, somewhere in
Antarctica. You will instantly acquire a view of the Antarctic
heavens, but pressing [backspace] will return you to your
PRECISE previous observation point. This is best carried out
with a fairly wide field, preferably the entire visible sky.
Note that this key will not undo zooms.
[home]
Return to your original time and location.
Settings will be as they were when Coeli started, including
facing, elevation, magnification, and projection. In fact,
everything - apart from the time and possibly the date - will
be as it was when Coeli first loaded.
Best used to return 'home' quickly after extended travels in
the Location Browser, lengthy journeys in time, or when simply
a little confused.
If you have not yet registered Coeli, please note that this
key will not return you 'home' as set via the command line,
but to Greenwich, England, which is always the pre-programmed
setting unless you have a personal copy.
This will also cancel your current zoom, colour, and location
settings, so make sure you have stored them with [F7] if they
are important to you.
[INSERT]
Increase blue levels in the colour palette. All monitors
differ in their general colour cast, some more appropriate for
astronomical displays than others. If you initially find the
general effect unsatisfactory, this function may improve
matters. The only advice is try it and see.
[DELETE]
Decrease blue levels in the colour palette. See above.
[PAGE DOWN]
Auto animate
Default increment: 1 sidereal day.
Saves you repeatedly pressing the [time advance] keys to watch
the movement of the stars and planets with the passage of
time. The clock will be repeatedly advanced by the step-size
and unit last accessed via the keyboard.
Very instructive (and fun!) when auto-advancing by sidereal
days - see [u] function above.
For the best frame rate when auto-animating, switch off the
horizon and graticule, reduce the number of displayed stars to
a few dozen by repeatedly pressing [-], and keep your
zoom-index in the negative. To really see the planets whiz by,
you could switch their names to symbols with [alt]+[p], and
even banish the stars altogether by decreasing the limiting
magnitude yet more.
A fairly prolonged press of any mouse button should return you
to normality!
If you notice a perceptible slow-down, you may counter it with
one of two remedies after stopping the present animation:
a) switch off comet displays with [alt]+[c]
b) advance the clock by a minute or two with (])
and then re-activate the animation. Either or both usually
clear the problem for the session's duration.
[F1]
Azimuthal Equidistant Projection.
A fine overall compromise, this is Coeli's default celestial
projection.
Points along any straight line radiating from the projection's
centre will preserve their relative positions. In other words,
angular separations will reflect reality.
[F2]
Azimuthal Stereographic Projection.
Constellations will retain recognisable shapes even on the
extreme periphery, but the further from the projection's
centre a constellation lies, the more inordinately will its
dimensions be exaggerated. Akin to looking down a tunnel which
has astronomical murals: pictures to the immediate right,
left, and above our heads seem large regardless of their true
dimensions, while those ahead toward the tunnel's aperture
approach compactness through perspective. The tunnel's end -
the 'point at infinity' in painter's terms - is the
projection's centre.
The stereographic is useful if you plan to set a horizon view
and then concentrate on a particular area. Centralisation via
the traverse tool is not quite so critical.
[F3]
Orthographic Projection.
In Coeli, twin hemispheres are shown.
A classical 'globe'. Coeli's orthographic is most appropriate
for simultaneously displaying the antipodal sky. For example,
if you dwell in the north, the 'globe' on the left will show
the constellations of the southern celestial hemisphere
(unrisen, in green) and vice versa. In fact, Coeli's
orthographic will simultaneously display the obverse of
whatever viewpoint you have chosen: what you can't observe
from your time and location will always be visible on the left
hand face of the sphere. In this way, you can avoid the
extreme distortion caused by the equidistant and equal-area
projections to constellations which never rise at your
position.
Only low magnifications (less than zero) are of any practical
use with Coeli's orthographic.
If you intend zooming in on your observable sky and the
compactness this projection seems to offer appeals to you, we
would always recommend the azimuthal equal-area over the
orthographic.
[F4]
Azimuthal Equal-area Projection.
Whether this beats the equidistant is a matter of taste.
Certainly the compactness of the equal-area does much to
commend it. Aesthetically, it probably has the edge. Switch to
horizon view and negative magnification and you'll gain a fine
impression of the 'arch of the sky'.
At zenith view there is little to choose between this and the
equidistant. All constellations will preserve their relative
sky area, but will be more compressed and elongated at the
periphery.
[F7]
Store current settings.
All your preferences will be stored for retrieval at a later
date. Use [SHIFT]+[F7] to retrieve them at any time. This
function creates a permanent record, so it will work across
sessions.
If you have a favourite view to which you would always like to
return after other activities in Coeli, or preferred settings
that are not part of Coeli's defaults at startup, simply
pressing [F7] will preserve them for instant retrieval.
[F9]
Print current screen. Map Mode only.
Coeli assumes your printer is capable of IBM Proprinter
emulation. Please check your printer's manual if you are
unsure. Very few checks are performed prior to dumping the
screen contents to the printer. If your printer is not ready
(ie. switched off) you will see a message to that effect. If
it is offline, nothing will happen until you place it online.
The idea behind all this minimalism is that you are able to
have the map screen looking exactly as you want it prior to
printing it. So don't forget to click the mouse on empty space
to banish any messages that might still be present!
In 800x600 resolution (Coeli's mode 3) and above, your
standard A4 landscape page will not accommodate the entire
screen. The lower (horizon) half has been given priority. We
elected to preserve aspect ratio at the expense of
completeness. In any event, you will soon get a feel for what
will appear on paper and what will not. Coeli's mode 2
(640x480 resolution) is recommended if you intend to print
frequently.
Use [shift]+F9 to enter Printer Setup if your device is
not attached to the standard LPT1 (parallel port #1). Other
possible ports are: LPT2, LPT3, COM1, or COM2 (serial ports).
[F10]
Single page mode on/off
The video BIOS of some old and very new PC systems may
sometimes fail to interact correctly with your VESA driver,
often reporting the presence of more than one graphics page
whilst ignoring VESA requests to switch from one to the other.
Since by default Coeli will try to page for a smoother
transition during zooms, it may be annoying if your video card
cannot react to the instructions, causing the display to jerk
between redraws.
This is not an insoluble problem if you have 1 Mb or more of
video RAM, but it can involve extensive tinkering with your
VESA driver / video configuration settings. ( See the file
HELP-ME!.DOC for hints about this) If you haven't the time or
the inclination to fiddle until satisfactory results are
obtained, pressing [F10] is quite an effective stopgap,
especially if your PC is a fast 486 or Pentium.
The difference is difficult to describe so it's best simply
to try both modes a few times and decide for yourself.
FIN
oooOooo
Copyright (c) 1996 Swimming Elk Software. All rights reserved.