Coeli Overview and Display Highlights
The Cosmos at your Fingertips
Requirements
Minimum
This Coeli software can be installed on any IBM compatible PC with a 486 DX processor or higher running Windows 95, 98, or NT. The more video and conventional RAM you have, the better - 1 Mb or more for the former, and at least 8Mb of the latter.
Recommended
The recommended system for running this program, however, is a Pentium 75 or higher with 16 Mb of RAM and a graphics card equipped with at least 2 Mb VRAM.
Additionally, your Windows display should be in either Hi-color or Truecolor mode at a resolution of at least 800x600 pixels. The optimum screen resolution for the Coeli display is 1024x768. Please note that a display of only 256 colors is bound to be a disappointment. If your video subsystem is not up to displaying in at least Hi-color at 800x600, we would strongly recommend purchase of our slightly less demanding Coeli - Electric Planisphere, with which this Coeli product is maintaining maximum compatibility. Just point your Web browser at
http://www.coeli.com
for details.
A Quick Excursion around your Coeli Software

Hints on General Navigation

What the

Sky window initially presents you with is the entire celestial sphere for the preset location, with South at the bottom, East at the left. Vega will be the initial focus for northern observers and Canopus for the southern hemisphere. Stars plotted in dark green or grey lie below your horizon: they have set, not yet risen, or may never rise at your position.

Display the

time bar by pressing [t] Now hide it again using the right-click menu entry |Clock|Bar|. It is worth noting here that enabling the timebar prevents the use of single keypresses in the sky window, unless the timebar itself was invoked with keypress [t] and not accessed with the mouse. So during intensive manipulation of the display it is as well to avail yourself of the Viewbar's comprehensive functions while the Clock bar is present.
Coeli's virtual Earth revolves in real time, and the apparent motion of the stars is from left to right when facing south.

Your Coeli display's default celestial projection is an azimuthal Equal Area,

[F3], centered on your zenith. It is of the type used by planetaria the world over, so it is in good company, but if you happen to desire a change, there are three more to experiment with: Equidistant [F2], Stereographic [F4], and Orthographic [F5]. When you gain a little more experience using this Coeli software, you'll want to begin experimenting with contrasting viewpoints too.
Start by pressing [H] for a horizon view of the southern sky. To traverse through the 360 degrees of the compass, access the traverse and elevation tools with [ctrl][D] or [ctrl][E]. Alternatively, you may prefer to enable auto-centering at the outset with |Viewpoint|Projection|Auto-center| thus doing the job of the traverse and elevation tools automatically each time you click on a new object. With its often abrupt switching of view, this setting can prove disorienting on occasion, especially if you have not yet attained full familiarity with your local celestial geography! As with all things Coeli, it will therefore pay to experiment a little.
[Z] will return you to a zenith view, but at the new line of sight you traversed with the tools.
It is worth stressing that after any operations which somehow change your viewpoint, pressing [F12] immediately is the safest way to ensure an accurate display of all stars visible at the current magnification. For extra responsiveness, some operations do not incorporate this process.
By default, [a]uto-resolution of stars is switched on. What this means is that you only begin to see the dimmer stars as you increase your resolving power (change to binoculars/telescope), in imitation of reality. Initial magnification is negative in order to encompass the entire sky. Zoom down to zero magnification to receive an impression of the sky as seen on a clear night by the naked eye. To adjust the number of stars visible at any given magnification, press [+] or [-]. Auto-resolution will need to be disabled with [a] if you wish your changes to survive any zooming or unzooming operations you might perform subsequently.
For Coeli's representation of the sky, realism has been the watchword, and we are confident that this ideal has been achieved. Color is the key. The essence of a star is its color, linked intimately to its spectral class. Astronomers have given all the brighter stars a color index, and the program's palette is based on it. So, if you see a deep crimson in your Coeli display, you can be certain that it is an M, or a piercing white an F, or an orange like Arcturus or Aldebaran a K. Not that this may matter to you, but it will to many. Observe the true heavens on a crystal night - each star has its tint, each planet its hue, albeit cast over with tropospheric blue.
The program itself provides these keys for tampering with colors: [B] , [D] , and [R].
[B] brightens (lightens) the palette uniformly, giving a washed-out effect, and finally washes color out completely. [D] achieves exactly the opposite, darkening - and thereby deepening - all the colors. Unrealistic, as if seen through sunglasses, but you may find it a change. It at least reveals a star's underlying 'character', subleties that the brightness may have hidden.
[z] does just what it says: zooms you in (or narrows the field of view, like a pair of binoculars or a telescope), displaying the magnification factor as you go. Try this on Albireo, Izar, Castor, Mizar and many others. They will eventually resolve as true doubles, imitating reality. [x] widens the field, and zooms you out. Your Coeli display automatically resolves stars for you in proportion to the magnification, like a real instrument: the bigger the objective glass, the more stars you will see and the brighter the more brilliant ones will appear. Conversely, the more extremely your field narrows, the fewer stars will be seen, because this Coeli product's database is restricted, unlike the galaxy's.
Perhaps the [a]uto resolution feature merits a bit more elaboration. Firstly, if you disable it, you will have to add and brighten stars manually via the keys listed on the [h]elp screen. This is long winded, but the best way to achieve the most impressive results for the given magnification, and to derive the most personal satisfaction. We all see the sky differently and are affected by different facets of it. But for quicker and yet still fairly realistic resolution, our preset values are quite good. Keep it automatic until you come across a starfield which you truly deem worth perfecting.
The Coeli interface allows you to use [f] to find a specific constellation, star, DSO, or planet. If a constellation was selected, the group of stars will be spotlighted for you against a neutralised star background. Selecting 'not designated' from the dropdown list will always return you to a normal display.
Stars may also be searched for by common name: your Coeli program has almost 200 of these recorded, and you may add more if you've the inclination.
Above all, this Coeli software is a point-and-click introduction to the skies, and the mouse-crosshair its most useful instrument. Use the crosshair to select a star, then click the <left> button for a short display of the star's name and designation as follows:

- The Greek letter plus I.A.U. abbreviation (Bayer nomenclature), accompanied by the Flamsteed number. For dimmer stars, just a Yale Catalogue number will be given, and in the case of Hipparcos and SAO stars, the Henry Draper ID. If the star has a common name this will be displayed underneath.

Using the [c]entre key on a series of points is the best way to star-hop across the heavens: Use the stars as 'stepping stones' as you shift your gaze. The technique goes like this: click on the first point, centre the display, click on the next point, centre the display, and so on. The Coeli display interface does not restrict you to stepping across stars: you may also click and center on Deep Sky Objects, planets, comets, the Sun and Moon, or empty space.
The Celestial Sphere modeled by your Coeli display revolves in real time, updating itself without your intervention. Ever yearned to see a heliacal rising of Sirius on an unexpectedly clear southeastern horizon when all the zenith is thunderous overcast? Your Coeli software plots the moment of its rising, so effectively you're permitted to observe it twice - first on Coeli's virtual heavens, and then outside in the strangely silent dawn cold where Sirius twinkled ominously red for a fleeting instant in the atmospheric turbulence of sea-level. The Stella 2000 family even shows scintillation (twinkling) for that extra touch of realism.
Incidentally, if the relative positions of some stars begin to appear a little scrambled (as they may do during frequent use of functions which change your viewpoint in some way) , simply press [s], [n], [e], [w], or [F12] depending on your preferred orientation, for a full recalculation of all altitudes and azimuths. In any event, the program's ongoing calculations will eventually get around to returning every star to its correct position.
The Report function will get you what the left button gets plus ancillary data - things of interest include the following:

- A full expansion of the rather cryptic Bayer nomenclature. Eg. Omicron Ursae Majoris for 'o UMA'. A great help if you are new to astronomical conventions.

- The full Latin name for the constellation, followed, if applicable, by the English translation. Bare catalogue numbers, although they may lie slap in the centre of, say, Orion, will have no constellation associated with them. This will probably be cosmetically remedied in future versions.

- The brightness (apparent magnitude) and luminosity (absolute magnitude), based on the Yale Catalogue parallax value. If the star is among the 100 brightest, this will also be indicated.

- The star's approximate distance in light-years (LY) or parsecs (Pc), again computed from parallax figures in the relevant catalog. You may assume the lower numbers are about as accurate as we can get, but please take anything over about 500 LY with a pinch of salt - they may be reliable, they may be not. Don't say we didn't warn you! There doubtless exist more accurate stellar parallax figures in dedicated statistical catalogs, but this Coeli product hasn't access to them. All values are computed from Yale / Hipparcos / SAO catalog data.

- At the bottom, you will be shown some terrestrially-based information, the most important of which will be the rising, setting, and transit times for the currently focussed star, its altitude, azimuth, right ascension, and declination.

Useful extensions to the information tables now include proper motion, parallax, spectra, remarks where available, sunrise/sunset, dawn/dusk/hours of darkness, solar and lunar apparent and equatorial coordinates, astronomical twilight, as well as the phase of the moon.
oooO0Oooo
Grateful acknowledgements to Hartmut Frommert of SEDS for permission to incorporate his fine Messier thumbnail images into the Coeli display.
All trademarks and registered trademarks are the property of their respective owners.
The program packages Coeli ~ Stella 2000, Astromania, Adastra, and QuikSky and all documentation copyright (c) Swimming Elk Software 1995, 1996, 1997, 1998.