Software of the Month Club 1997 April

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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 - 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. [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 PsL's special secure order form. 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 objects 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 by not loading so many stars at startup - between 500 and 1000 is ample for this effect, 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.