Updated software for Guide 8.0, continued

(18 Apr 2003) Ability to show DSS-2 images in color: If you look in "Extras... DSS/RealSky Images", you'll see that Guide can download DSS-2 R and B images. It seems reasonable to download both, then combine them on-screen to make a passable "color" image (admittedly lacking a green channel).

Guide now supports this. There is a fourth radio button, for "DSS-2 B color overlay." You first download a DSS-1 image or DSS-2 R image. It shows up as before. Then you select the new radio button and download the DSS-2 B image. Instead of simply overwriting the existing image, it provides a blue overlay. Red stars look red and blue stars look blue.

There are really only two problems with this system. First, controlling contrast/brightess is tricky; you have to click on the image, and you may get either the "ordinary" image or the blue one (if you don't get the one you want, use of "next" will solve that problem.) Then you can adjust its contrast/brightness. That is, you have to adjust the red image, then the blue one, or vice versa.

The second problem is the lack of a green channel. It's tough to get anything "realistic" with what we've got here. Still, you can at least get some color data that was previously lacking completely.

(18 Apr 2003) Options to download B1.0 and 2MASS data: Very similar to the existing options in "Extras... Get Ax.0 Data" for getting A2.0 and GSC-2.2 via Internet. You zoom in on the area of interest, click on either option, wait a bit, and B1.0 stars or 2MASS objects appear in the background. As with the A2.0 and GSC-2.2 options, you can click on a star from that catalogue and on "display" to turn it on/off or select labelling.

With all four "dynamically downloadable" datasets (A2.0, GSC-2.2, B1.0, and 2MASS), the "more info" section includes an entry you can click on to delete the accumulated downloads, enabling you to start over from scratch for that particular dataset.

Click here for more information about USNO-B1.0.

Toolbar buttons are available for these functions, and (as with any function for which a toolbar button is available) you can select hotkeys to work with these functions.

(18 Apr 2003) Some better "Go To" functions: The "Go To... Star... Nearby Star", "Globular Cluster", "Messier", "Galaxy... Common Name" and "Nebula... Common Name" functions have all changed from their former style, in which you just got a list of objects and selected one from the list. Now, you get a "help"-style screen, much as with "Go To... Planet" or "Go To... Constellation". As with those functions, the objects are color-coded according to visibility; and you can click on column headings to sort according to assorted parameters. For example, the "nearby stars" list gives parallaxes, distances, RA, dec, and magnitude, and you can sort on all of these.

(18 Apr 2003) Planets shown in perspective: Previously, planets have been shown with isometric views (as seen from infinity). In theory, when you view (say) Mars from Phobos, you should see a foreshortened view in which the polar regions can't be seen. In Guide, you always could see exactly half of whatever planet you looked at. This has been fixed.

This also let me lift a restriction: previously, if you were within one radius of a planet, Guide simply stopped showing it. Now, you can view planets from "close up"; you can, for example, shift your viewpoint to be from the International Space Station (or other satellites) and see what the view from the window looks like, in real time or for other times. Animating in this mode can be nifty, too.

(I'd hoped that this change would also result in a tremendous speedup. No such luck.)

(18 Apr 2003) Display of J002E3: J002E3 is the name of an object assumed to be the empty S-IVB rocket stage from the Apollo 12 lunar mission. After this stage was detached, it went past the moon and took several orbits around the earth/moon system, until it was ejected. It then spent over thirty years orbiting the sun.

In 2002, it was again captured by the earth/moon. It spent most of its time between us and the sun, and therefore wasn't actually noticed until September. Bill Yeung, an amateur astronomer with an impressive setup for surveying for asteroids, came across it in a few images. He assumed it was a near-earth asteroid and gave it the designation J002E3. We were soon able to compute an orbit for it that put it back near the earth around 1970. (I briefly thought it was the Apollo 12 S-IVB stage, because the initial orbit indicated that it was in the neighborhood of earth at the time. It was quickly pointed out that this stage, and most of the Apollo stages, was deliberately "thrown" at the moon... which I should have remembered, having rigged Guide to be able to show the impact points.)

You can click here for astrometry and ephemerides and comments about J002E3.

I've had inquiries about displaying J002E3 in Guide. This presented a problem, since it is too high for the "normal" artificial satellite methods to work, but is still orbiting the earth. I have worked out a somewhat graceless solution, though. If you download this file (about 68 KBytes) to your Guide directory, and unZIP it there, you can then see J002E3 as a bright "asteroid" (I made it ten magnitudes brighter than it really is.)

You can see in this ephemeris for J002E3 that we'll have good opportunities to observe this object in March 2003. It then spends much of April at apogee between us and the sun, then comes in to be readily observed in May. But after that, it climbs up to the L1 point (inner "balance point" between the earth and sun) and leaves the earth/moon system again, to go back into orbit around the sun. So this is our last opportunity to gawk at a piece of Apollo hardware "in flight" for a long time.

(18 Apr 2003) Use of COM5 or COM6 for scope control: Guide previously supported only COM1 through COM4. Don Dillinger asked on the Guide user list if there was any good reason not to support COMs 5 and 6. I couldn't think of one, and suggested a way to find out if Guide could access those ports. Don confirmed that Guide could do it, so I've modified the "Settings... Scope Control" dialog to include two more radio buttons.

(18 Apr 2003) "Pick" data stored in a file: On the Guide user mailing list, there was a request to dump the mouse cursor RA/dec to a file. I've decided to generalize this a bit: when you right-click on an object, a file called showpick.txt is created or overwritten. The first two lines in the file are the RA/dec of the pixel on which you have clicked; the next two are the RA/dec of the object on which you have clicked. The format and epoch of these coordinates match those specified in the Settings... RA/Dec Format box.

Following these four lines are the text appearing in the "short info" dialog box. All of this may, I think, be of use to people with some custom scope control programs.

(14 Jan 2003) Guide in Polish: Marcin Siekierko has provided the file needed to get most of Guide to appear in Polish. Once you install the current update, you will be able to click on "Settings... Languages" and see a "Polish" entry. Also, you can go into "Settings... Toolbar" and see, almost exactly in the middle of the list of toolbar options, an entry for "Polish". This allows you to add a toolbar button to toggle between English and Polish. You can also select a hotkey to perform that function.

(6 Dec 2002) Keyboard/toolbar options to "go to" compass points: Jim Opalek asked if it would be possible to set up Guide so that you could (for example) hit "E" and have Guide recenter on the Eastern horizon. It wasn't (best you could do was to right-click on the alt/az shown in the legend, then click on the "E" button). However, I was able to add this capability.

To see this, click on "Settings... Toolbar" and go to the bottom of the list. There are ten new "center on" options listed: eight for the compass points, one to center on the zenith, one to center on the nadir. As with any other toolbar option, you can add a button for that action to the toolbar, and/or set a hotkey to perform that action. Thus, one can easily set "W" to center on the western horizon, and so forth. ("N" is a slight problem, since one is used to this being linked to "go to NGC". Personally, I'll probably set up "N" to correspond to "center on northern horizon", with "G" linked to "go to NGC". Your mileage may vary, but then again, you can link up keys to actions in any way you choose.)

(6 Dec 2002) Revised 'go to satellite' function: This function still asks for the name of a satellite, and if you enter the entire name, it will center on that object. This part is unchanged, except that you can now enter the five-digit NORAD catalogue number for the object, or its international designation.

If you enter part of the satellite name, Guide will give you a list of all satellites containing that text. For example, enter "molni", and you'll get a list of Molniya satellites (plus, perhaps, some others containing those five letters.) The list will be color-coded using the colors for indicating visibility, with a few bits of detail on each satellite (NORAD and international designations, name, and magnitude). Click on one of the entries, and Guide will center on it.

If you enter a "blank" (no text at all), Guide just lists all the satellites in the currently-selected satellite element file.

(6 Dec 2002) Better tooltips: Previously, Guide showed tooltips in the application title bar area, a really unconventional method that left people wondering just what was going on. In particular, people didn't necessarily notice that tooltips were given at all.

If you look in the "Settings... Toolbar" dialog, you'll see a new "Tooltips" option. Check this, and Guide will show tooltips in a more "normal", Windows-like manner. (I have hopes that this will draw attention to one of the features I think is really nice in Guide, namely, the fact that you can get a lot of functions by clicking on legend items. You wouldn't normally think to click on the time shown in the legend, for example, to reset it. With a tooltip, the function becomes blatantly obvious.)

There was quite a bit of discussion of this option on the Guide user group, with many people finding tooltips to be obtrusive and actually preferring the previous, though unconventional, method. So by default, Guide will continue to show tooltips on the application title bar.

(6 Dec 2002) Bug fix for AVIs: Ever since I added the ability to create .AVI animation files to Guide, the color output has been pretty bad. I assumed this was due to compression artifacts, but a recent post on the Guide user list asked about this and prompted me to dive back into the code. I hadn't actually written this part of the program; instead, I found some helpful code on the CodeGuru site and fitted it into Guide, all the while not noticing that it's limited to 8-bit images! Changing an "8" to a "32" caused the images to suddenly become correct.

(6 Dec 2002) SIMBAD data for some stars: SIMBAD is a widely-used on-line system for getting data on celestial objects; you can go to its search page and type in an identifier such as "NGC 1234" or "HIP 5678" or "ZZ Cet", and get lots of current information and cross-references for that object.

If you ask for "more info" for a variable star or Hipparcos star, you'll see a link that says "Click here for SIMBAD data". Clicking on it fires up your Web browser, sending a query to the SIMBAD site and fetching the requested data for display within the browser.

I should be able to extend this, in very straightforward manner, to most other objects shown by Guide.

(6 Dec 2002) Use of SDP4 for high-altitude artificial satellites: There are two algorithms in common use for modelling the motion of artificial satellites. The most commonly-used is SGP4 ("Standard Generalized Perturbations 4"), a method which computes ephemerides for satellites with good accuracy. This is the method generally used by Guide.

But for higher-altitude satellites (anything with an orbital period of 220 minutes or greater, which includes all Molniyas, GPS, and geosynchronous/geostationary satellites), SDP4 is the preferred model. This model includes some of the effects of lunar and solar perturbations and some of the more subtle variations in the Earth's irregular gravitational field. None of these effects are all that noticeable for the vast majority of satellites, but at higher altitudes, they can be significant.

Some months ago, I posted source code for SGP4/SDP4 and other satellite motion models on this site. (The other models don't appear to get any real-world use.) If you download this file (about 47 KBytes) and unZIP it in your Guide directory, then Guide will use SDP4 for all high-altitude satellites. (You don't need to change any settings in Guide; it will automatically detect and use the new .DLL.)

(6 Dec 2002) Several minor changes:

  • Better 'go to... constellation' and 'common star' functions: The "Go To... Constellation" function now brings up three lists of constellations: first, a small grid of constellation abbreviations, then the sort of four-column list present in the last few updates, and finally a full listing giving abbreviations, names, descriptions, and genitive form for each constellation. The color scheme indicating visibility remains as before.
  • The "Go To... Star... Common Name" function is also now given in a "help"-style form, complete with color-coding for visibility.

  • Searchable help/more info/table screens: In all such "help" screens, you can type a few letters and have Guide find that text. For example, fire up the "Go To... Constellation" list and type "hunt", and Guide will find "Orion, the Hunter". Hit Enter, and it will center on that constellation. Similarly, if you go into Quick Info and type "twilight", after the first few letters, Guide will be showing you twilight times.
  • Added conic projections: There are three new conic projections listed under "Settings... Projections". These are of almost zero use in celestial mapping, but are some slight interest for terrestrial maps.
  • Asteroid/comet rates of motion: The rate of motion of an asteroid or comet has long been given in "more info", expressed as a speed and position angle. In response to an inquiry on the Guide user list, they are now also given as rates in RA and declination. By default, both rates are given in degrees/day, but I realize that some people will want assorted other rates. To do this, you can edit the file strings.dat and look near the bottom for this line:
  • 1,1:RMotion is %.2lf ^degree^s/day in RA, %.2lf ^degree^s/day in dec\n

    The "1,1:R" tells Guide to multiply the rates in RA and dec by 1 and 1 (i.e., not scale them at all). If you wanted rates in arcseconds per day and arcminutes/day, you would revise that line to read:

    3600,60:RMotion is %.0lf ^arcsecond^s/day in RA, %.1lf ^arcminute^s/day in dec\n

    Units can be set on each axis. By changing the ":(space)" to ":R", you can switch the RA to be in time units rather than straight angular units. Mix-and-match all this, and you can get combinations such as:

    15,60: Motion is %.1lf ^RA minute^s/day in RA, %.0lf ^arcminute^s/day in dec\n
    .625,2.5: Motion is %.2lf ^RA minute^s/hour in RA, %.2lf ^arcminute^s/hour in dec\n
    .625,2.5: Motion is %.2lf ^RA second^s/minute in RA, %.2lf ^arcsecond^s/minute in dec\n
    37.5,150: Motion is %.1lf ^RA second^s/hour in RA, %.0lf ^arcsecond^s/hour in dec\n

    The above gives positive RA motion to the west. To reverse this, negate the RA multiplier; for example, the first line would become

    -15,60: Motion is %.1lf ^RA minute^s/day in RA, %.0lf ^arcminute^s/day in dec\n
  • Can enter RA/decs in new formats: Previously, when entering an RA, you had to include the 'h', 'm', and 's' separators. For declination, you had to use ' and " to indicate minutes and seconds. You can now omit these. You can also omit spaces; Guide will treat a six-digit number as HHMMSS (or, for a declination, ddmmss), with an optional fractional part '.SSS' (or '.sss') appended. Furthermore, you can enter all of these in the RA box, an option requested by those who cut-and-paste coordinates frequently. So, if the RA box contained:
  • 031415.9, +265358.9
    03 14 15.9 +26 53 58.9

    or some combination thereof (intermediate spaces and commas don't matter), Guide would center on RA=03h14m15.9s, dec=+26o53'58.9".

    I'd avoided doing this because I thought that requiring rigid formatting would decrease chances for unintentional "user errors", but have rethought the matter. Being able to do this makes entering RA/decs a bit simpler; I think it will be worth the risk of occasional error.

    (5 Oct 2002) Adjustable color for 'night' (red) mode: The "Display... Backgrounds" dialog now contains a color button for use with red mode. Some people have commented that they find the default mode excessively bright, and I've had one inquiry from a gent who wanted a green mode. His theory is that the eye is more sensitive to green light, and has greater resolution in that color. Therefore, you can use a faint green light instead of a bright red one, and see things more clearly without ruining your night vision.

    I have no idea as to how correct this is, but the matter should be easily tested now. You can now choose a fainter red, or a green of desired intensity, and so on.

    (5 Oct 2002) More (extremely minor) irregular satellites: Very few people will be seriously interested in these: Guide can now show another eleven irregular satellites of Jupiter (S/2001 J 1 to S/2001 J 11), and the recently-announced new satellite of Uranus (S/2001 U 1). Given this, Guide shows almost every natural satellite in the solar system. (The exceptions are some inner satellites of Saturn in odd or poorly-known orbits.)

    (5 Oct 2002) Three bugs fixed: A few people had reported problems with the function to download DSS-2 R and B images. Users of WinNT, XP, and 2000 systems found that the full screen mode wasn't exactly full-screen; the menu bar insisted on remaining on-screen. With the 22 September 2002 version, people who had Guide partly (but not completely) installed to the hard drive sometimes experienced crashes when running without the CD-ROM in the drive.

    The currently-posted version should fix all three problems. However, as of 5 October 2002, the DSS-2 function has another, totally different problem: the server from which Guide downloads images is not providing DSS-2 images (only "original" DSS-1 images). You'll get a suitable message from Guide along the lines of "a DSS-2 image is not available for this RA/dec." With any luck, STScI will get around to fixing this eventually.

    (22 Sep 2002) True "full screen" mode: It's now possible to switch Guide to a "full screen" mode in which the chart expands to cover the full screen. The menus and system tray vanish, leaving nothing but the chart.

    This switching is normally done via hotkey. You'll have to select the hotkey corresponding to this function; to do so, click on "Settings... Toolbar" and scroll until you find, at the bottom, "Full Screen". When you select this, you'll see a "Choose Hotkey" button. Click on this, and you'll get a list of possible hotkeys to use. Select one, click OK, and you can then use that hotkey to get into (and get back from) full-screen mode.

    There is an alternative to using a hotkey to switch to and from full-screen mode. A menu or toolbar option wouldn't help, of course; these would let you switch to full-screen mode, but not back again. But you may have noticed that clicking with the mouse in the legend area causes assorted actions (with the actions described in the title bar, as the mouse moves over the legend.)

    You can configure Guide so that a right-click on the constellation abbreviation shown in the legend area toggles full-screen mode. To do this, edit the file legend.dat in Notepad or a similar text editor, and look for the lines:

      62     25    25     25
    # Click on constell = 'go to constellation' dlg

    Change them to read:

      62     25  2997     25
    # Left-click on constell = 'go to constellation' dlg; right = 'full screen'

    and save the file. Run Guide, move the cursor over the constellation abbreviation shown in the legend, and you'll see that the title bar tells you that right-clicking in this area will toggle to full-screen mode. And, indeed, you will find that it does so.

    (22 Sep 2002) Multiple aperture circles: Previously, you could have one circle of a specified angular diameter and color, that would stay centered on the chart. This has been revised slightly. Now, the "Display... Ticks, Grids, Etc." box has a button to "Add Aperture Circle". Click on this, and you can specify the size and color of a new aperture circle. Repeat as needed to add further circles.

    You can right-click on existing aperture circles, then on "Display", to modify their sizes or colors or to turn them off.

    (22 Sep 2002) Ability to make color PostScript files: Until now, Guide has only made PostScript files in black and white. It can still produce such, but it can also now produce color PS. The method used is almost exactly like the one for distinguishing between B&W versus color printouts. Go into "Display... Backgrounds" and select "Chart Mode", and the printouts and PostScript files will be in color. In all other modes, printouts and PostScript files will be in black and white.

    For both printouts and PostScript files, the reasoning is the same: to select colors in some sort of rational manner, you need a white background (since that's what the "printed page" will look like.) "Chart mode" provides such a background.

    (22 Sep 2002) More "standard", Windows-like menus: Arild Moland pointed out that in most Windows programs, menu options leading to a dialog box end in "...", but that Guide was not one of them. That struck me as a good idea, so I was happy when Arild sent me a revised STRINGS.DAT file (part of the above update file) that corrected this problem.

    (22 Sep 2002) New (Hammer-Aitoff) projection: This is not an astonishingly useful projection. It's a "compromise" projection, mostly used on terrestrial maps. Everything gets distorted a little (though not too badly), and both shapes and areas are a bit off (though not too badly, except near the poles... that last isn't a big deal for maps of the earth, but is more troublesome with star charts.) However, it gets a fair bit of use, and I felt it best to add it to the list of projections recently added to Guide.

    (22 Sep 2002) Better "realistic" mode: In the past, if you went into Display... Backgrounds and selected "Realistic", the sky would turn a light blue/cyan if it was daytime, various shades of darker blue if it was twilight, and would fade to black at night. If you do that now, the result will be much more realistic, with the sky being brighter near the setting (or rising) sun and showing the light-polluting effects of the moon.

    Guide has long had the capability to compute sky brightness using a method described by Bradley E. Schaefer. This does a great job of computing how bright the sky is, in assorted bands, in "physical" units of ergs per square centimeter per square arcsecond per angstrom. The main source of error in Guide's rendering of the sky is that converting these to proper colors on-screen is a black art, one I'm still working on. (The intensity is almost right, but the colors are not nearly as good as I'd like them to be.)

    (22 Sep 2002) NexStar improvements: I've swapped a few e-mails with Mike Swanson, who has an excellent Web page on PC control of NexStar telescopes. Given this data, it became clear that Celestron has played a few games with NexStar control: the code I added works well with the "classic" NexStar 5 and 8, but the GPS and 5i/8i scopes use a slightly different command set, and the GT scopes have yet another set of differences.

    However, this should no longer be a problem. When you hook up to a NexStar in Guide and first send it a command (either "Slew Scope" or "Slew Guide"), it should do a little interrogation step wherein it identifies which type of NexStar (or Ultima) scope is attached to the serial port. It will then announce its results, then go ahead and control the scope properly.

    (22 Sep 2002) Support for Astro-Physics mounts: I had long thought that Astro-Physics mounts were LX-200 compatible (or at least, were compatible for the small subset of commands used by Guide.) Turns out I was wrong; I inquired of Astro-Physics about an oddity in the way the "set declination" command works. Chris Marriott, the author of SkyMap, e-mailed me to confirm that yes, this is a problem, and kindly sent the relevant bits of code he's used to tackle the difference.

    In the "Settings... Scope Control" dialog, there is now an option for the Astro-Physics mount. Select it, and you should be able to control AP scopes.

    (22 Sep 2002) Handling of USB-to-RS232 devices for scope control: A few people with serial-port-free laptops have been attempting to use USB-to-RS232 converters with Guide, without success. I think I know why now. A bit of digging on the Web site of a manufacturer of such converters turned up a code sample that had some small differences from my own. I'm not sure just which differences were significant, but apparently, they combined to keep my code from using such gadgets.

    Anyway, with the above-posted version, everyone should be able to control scopes through Guide, whether they use a "real" COM port or a USB-to-RS232 converter.

    Note: For what it's worth, I've heard that some Belkin USB-to-RS232 converters are not as reliable as one might desire. Some have found problems when using them, which went away when other converters were used. I don't have much in the way of specifics, and it could simply be that the others emulated "real" RS232 better, thereby not requiring fixes such as the above. Or it could mean that some of these gadgets are better than others.

    (4 May 2002) New projections: The "Settings... Projections" menu used to list four projections. All were azimuthal projections, and none let you show much more than one hemisphere at a time (though you can trick the Equidistant projection into showing a bit of both hemispheres.)

    This menu now includes some new projections. Four are cylindrical projections: Mercator, Miller, Peters, and the "simple", or "plate-Carré", or "Cassini" projection. In a cylindrical projection, lines of latitude and longitude (for charts of the Earth), or of RA/dec (for charts of the sky), appear as straight lines, intersecting at right angles. (Note that, if you select "Zenith Up" in the Inversion dialog, it will be lines of altitude and azimuth that appear as straight lines; select "Ecliptic North" or "Galactic North" up, and it will be lines of ecliptic or galactic latitude and longitude that are so plotted. This may sound complicated, but select any of these cylindrical projections and the meaning will be immediately obvious.)

    The Mercator projection is really more useful in navigation than in astronomy, but remember that Guide does show charts of the earth (and all of these projections can be used for charts of the earth as well as of the sky.) The Mercator projection, like the stereographic, is "conformal", meaning that shapes are preserved; right angles in the sky stay at right angles on the chart, for example. But sizes are inflated toward the poles.

    The Miller projection is a sort of mathematical compromise: it looks a lot like the Mercator projection, and is almost conformal. Sizes are still inflated near the poles, but not quite as badly, and the poles are actually shown (in the Mercator projection, the poles would be plotted infinitely above and below the chart.)

    The Peters projection preserves areas perfectly. Unfortunately, shapes near the poles are stretched badly, even more so than in the "simple" projection.

    The "simple" projection allows you to show the entire sky, including the poles. This is really its only benefit. Scale is preserved along the vertical axis, but objects near the poles are stretched badly in the east/west direction.

    The menu also includes two "pseudo-cylindrical" projections: the sinusoidal and Mollweide projections. Both preserve areas: a given square degree in the sky will occupy the same amount of area on the chart. However, shapes get ruined; look near the poles, and you will see objects skewed into not-very-recognizable shapes. Both allow you to show the entire sky, both hemispheres at once.

    The "pseudo"-cylindrical projections halfway resemble the cylindrical projections, in that lines of declination or latitude will be straight and horizontal. But lines of RA or longitude will be curved.

    The Hammer-Aitoff projection is not really very useful. It's yet another "compromise" projection, mostly used on terrestrial maps. Everything gets distorted a little (though not too badly), and both shapes and areas are a bit off (though not too badly, except near the poles... that last isn't a big deal for maps of the earth, but is more troublesome with star charts.) However, it gets a fair bit of use, and I felt it best to add it to Guide.

    Guide supports three conic projections, ones in which the lines of longitude are straight lines converging toward the poles and the lines of latitude are concentric circles. In the 'simple conic' projection, distances along lines of longitude are preserved. In the 'equal-area conic' projection (also known as Albers' projection), areas are shown properly. The result looks quite a bit like the Peters projection, with polar countries flattened, but with a bit of a curve to it. In the 'conformal conic' projection (also known as the Lambert projection), shapes are preserved. This used to get a lot of use in maps of the earth, especially for mapping countries/areas with a large east/west extent and little north/south extent.

    (4 May 2002) Adjusting isophote contrast: In the past, one could right-click on an image or a planet, then use the Alt-arrow hotkeys (or four toolbar buttons that could be turned on from the Settings... Toolbar dialog) to brighten, dim, and/or adjust the contrast of the images or planets.

    In addition, one can now right-click on a nebula or Milky Way isophote, click "OK", and then use the same controls to adjust isophote contrast/brightness.

    (4 May 2002) More interesting horizon: If you've customized your horizon (read the comments at the end of HORIZON.DAT in your Guide directory for information about how to do that), you should ignore this. (Or at the very least, back up your HORIZON.DAT and OBJECTS.DAT files before trying it.)

    The default horizon in Guide is intended largely to provide a frame of reference, with a few houses, trees, cars, mountains, streetlights and other objects scattered around. Turn these on (with the "Horizon Objects" check-box in the Display... Background dialog), and you have some objects that let you look at the screen and think: "There's a tree there; that must be the horizon." It's also a good starting point for customizing your own horizon; you can move the objects around or replicate them at different positions ("put a tree here, here, and here") to get something that looks like what would actually appear as seen from your observing site.

    If you download this file (about 5 KBytes) to your Guide directory and unZIP it, the horizon will be replaced by one that is at least slightly more interesting. The all-sky chart in the center of Sky & Telescope shows a slight purple tint near the horizon, as well as a church with a steeple on the horizon; I've borrowed both of these features for the new horizon. The mountain is now snow-capped.

    (24 Apr 2002) Choice of photometric band and color saturation for stars: If you look in the "Star Display" dialog, you will immediately note that it's been rearranged a lot. This was simply because it had gotten tall enough that I would soon expect irate e-mails from persons running in 640x480 mode, informing me that it no longer fit on-screen.

    Aside from simple rearrangement, there are three new controls in this dialog. One is a way to set the "saturation level" for stars when displayed colored by spectral type (i.e., the "color stars" in the same dialog box is checked). Previously, this was always set to 100% full saturation: M-type stars appeared fire-engine red, O-type stars totally blue, G-types canary yellow.

    Set this value to be less than 100%, and you get somewhat more subtle tones which are slightly more realistic.

    The second new option is a "blurring" setting, which defaults to zero (no blurring). Set it to 1, and the edges of stars are no longer sharp, causing them to look a little more circular and aesthetically pleasing. Some people may prefer a still larger value, though be warned that anything past a blurriness of about 3 looks ugly.

    The third new control is a combo box from which one can select the magnitude band used in displaying Tycho and Ax.0 stars. You get a choice of VT or BT (the Tycho variants of V "visual" and B "blue"), Vj or Bj (the Johnson, or "standard", V and B), Rc or Ic (Cousins R "red" and I "infrared" bands), or Uj (Johnson U, "ultraviolet"). Select one of these, and Guide will compute and display magnitude data from the selected band.

    Select the R or I (especially I) photometric band, and the red stars tend to suddenly appear much brighter in Guide. Select the U band, and the hotter type-O stars suddenly become a lot more prominent.

    Some warnings have to go along with this, though.

  • The Tycho catalog provides VT and BT data. This can be converted to Johnson V and B with quite decent accuracy, and to R with passable accuracy. Conversion to I, R, or U is much shakier. Click here for details on how photometric conversions are done in Guide.
  • USNO A2.0 provides R and B-like magnitudes, which are not all that great to start with. (In particular, Dave Monet, head honcho for A2.0, notes that "Southern photometry is hosed".) It can be converted to V without much trouble. Guide doesn't even attempt to extend these to U or I.
  • Similarly, GSC-2.2 provides V-like, I-like, and B-like photometry. In some chunks of the sky, one or more of these bands may not exist. If you select that band, GSC-2.2 simply won't be shown.
  • Only two other user-added datasets are set up for color data: Brian Skiff's LONEOS.PHOT file of photometric calibration stars, and Arne Henden's "miscellaneous photometry" files. For the latter, you'll have to re-download the HENDEN.TDF file.
  • (24 Apr 2002) More 'Go To' functions revised: The response to the recent changes in the "Go To Comet" function was quite positive, causing me to revise a few other "go to" functions to provide similar lists. So far, the "Go To Planet", "Go To Planet Feature", and "Go To Constellation" options have all been revised in this manner. (I made one small change for the planet feature list, though: instead of using the red/yellow/green colors to indicate "below", "near", or "above horizon", I used them to indicate "on dark side of planet", "lit near terminator", and "in full sunlight". This should be helpful to lunar observers in figuring out which objects can be reasonably seen.)

    (24 Apr 2002) Orbital binaries shown: For a long time, Guide has shown some orbital binaries (such as 61 Cyg and Alpha Centauri) as two separate stars that don't orbit one another, and sometimes fly apart when you set distant dates. Others, such as Gamma Persei, were shown as single stars. Perhaps the most embarrassing case was that of Epsilon2 Lyrae; it was shown as two stars, but they overlapped (one of the few cases where Tycho-2 data is actually worse than the Tycho-1 data.)

    Almost all such cases are corrected now. The first sign of this appears when you click for "more info" on such a star. Comments are given from the USNO's "Fifth Catalog of Orbits of Visual Binary Stars", along with an ephemeris showing the position angle and separation of the binary over the near future. This helps to give an idea as to whether the pair is drawing closer together or drifting apart.

    Zoom in far enough on such stars, and both components appear, at the proper separation and position angle.

    A few miscellaneous comments... nothing you absolutely need to know, but you may be interested:

  • If you animate these objects, it's best to set a step size that is an integer number of years. I tried one with an animation step size of 180 days; at each step, the "viewpoint" was from the other side of the sun, and the target star (Sirius) appeared to jump back and forth. (Of course, if you want to demonstrate how parallax works to somebody, this might be a Good Thing.)
  • Only binaries for which at least one component has an Hipparcos number are included. This is almost, but not quite, all known orbital binaries.
  • The amount the objects move should depend on the ratio of their masses; if one is, say, three times heavier than the other, then the lighter guy should move three times as much as the heavier. But I don't have mass ratios catalogued for these guys. There is a "mass-luminosity law" that states that the luminosity of a star on the main sequence is roughly proportional to the 3.5th or fourth power of its mass. I used that. Stars of equal magnitude, therefore, are assumed to be of equal mass.
  • The one place where this falls down is for white-dwarf companions, such as those for Sirius and Procyon. These are shown as moving a lot while their primaries sit almost still. In reality, the companion stars are really quite massive, and their primaries ought to be wobbling a little.
  • (24 Apr 2002) Improvements to the DOS software: This one will probably come as a shock to most Guide users, since DOS is widely perceived as dead. In truth, I've expended maybe a hour's worth of work on the DOS version over the last few years; all improvements have been made to the Windows version, though many "trickled down" to DOS. But there are a few holdouts out there, mostly users of Mel Bartels' AltAz telescope control system. Mel's system basically requires DOS or a similar near-real-time OS.

    It's still hard for me to justify spending much time on the DOS version, though, so I simply went through and got a few dialog boxes (such as the Legend one) to work as their Windows counterparts do, and rigged up clicks in the legend area to work as they do in Windows (that is, you can left-click on the time shown to get the time setting dialog, or right-click to simply reset to the current time, and so forth.) I wasn't able to rig up a full selection of colors, since the program runs in only 16 or 256 colors, but I did revise it to offer more colors than it used to. Also, the pictures of DSOs now pop up in the background when you zoom in far enough, much as in the Windows version.

    (25 Mar 2002) Settable colors for Help/Table/More Info data: Some people were quite happy with the recent change in display of "help" and table data. In particular, it was mentioned that the black background was somewhat easier on night vision. As expected, though, some people expressed an interest in returning to the previous white background.

    With the current update, there is a "colors" option in the menu bar at the top of the Help/Tables/More Info box. Click on this, and you can set your choice of colors for background, "normal text", glossary-link text, and objects above, below, and near the horizon. (I've found that a white background with black "normal text" does work reasonably well, if the yellow "near horizon" text is revised to be a slightly darker shade for better readability. This maintains the easy-to-remember pattern of "red=below horizon, yellow=near horizon, green=easily viewable".)

    (25 Mar 2002) 'Go To Comet' dialog heavily revised: Click on this function, and you get a list of comets resembling that of the "Tables... Current Comets" function. You therefore get not just the comet name, but its position, magnitude, and current constellation shown, with color coding indicating whether it's near the horizon. I'll probably make similar revisions for 'Go To Planet', 'Go To Planet Feature', 'Go To Constellation', and 'Go To Common Star'. It would, in my opinion, be very nice if each list brought up the objects color-coded according to current visibility, with 'Go To Planet' showing the sort of data that appears in the first dozen lines or so of 'Quick Info'.

    (19 Mar 2002) Change in display of "help", table data: I've made some changes here that I'm not entirely sure people will actually like... still, they seem good to me, and I can reverse them if need be. So here goes:

    Page 57 of the April 2002 issue of Sky & Telescope has a review of the program C88. The reviewer mentions that all objects are color-coded to indicate their current visibility, and suggests changing this to a "stoplight" pattern: red=below the horizon, yellow=low altitude, green=easily visible.

    Previously, in Guide's help system and tables, links to glossary terms were in blue, and links to "go to" objects/set certain times were in red. The former is still true. But now, if the event takes place below the horizon, the link is in red; below altitude 10 degrees, yellow; above 10 degrees altitude, in green.

    This isn't true for absolutely everything, but it is true for lists of asteroids and comets, lunar eclipses, planets in "Quick Info", Galilean satellite events, and some others. Lists of planetary (usually lunar) features are instead colored by their exposure to sunlight, with objects on the terminator listed in yellow.

    This really strikes me as a very useful feature. It's wonderful to bring up a list of lunar eclipses and be able to tell, right away, that a given event starts below the horizon, is at low altitude when the umbral phase begins, but the rest of the eclipse is readily visible.

    The only real problem with all this was that yellow didn't show up on the white background. I had to switch the background to black. (It is this decision to which I expect objections to be raised.)

    (19 Mar 2002) Lots of bug fixes: The new changes to settings for colors and line styles in the 12 March update were reasonably simple to program, but involved changing a lot of code in Guide (which is the only reason I didn't do it two or three years ago.) Whenever you change a lot of code, a storm of bugs ensues, and this was no exception. As has been discussed on the Guide user mailing list, all sorts of problems ensued, mostly involving objects not being shown or printed in the correct color and/or line style. These are now fixed.

    (12 Mar 2002) Ability to reset hotkeys: It has long been possible for sufficiently devoted people to reset the hotkeys in Guide by editing a text file (click here for details). This is user-abusive enough that I doubt many people have done it.

    In the current version, there is a new "Choose Hotkey" button in the Settings... Toolbar dialog. By default, it is grayed out. Click on a function in the list in that dialog, and the button shows the hotkey currently associated with that function (or a non-grayed-out "Choose Hotkey" if none is associated with it.) Click on the button, and Guide brings up a list of possible hotkeys (and their current functions). Choose one of those hotkeys, and Guide will thenceforth perform that action when that hotkey is pressed.

    (12 Mar 2002) Full-color and line style selections: Previously, many objects in Guide could only be set to one of thirteen colors. This was a legacy of the bad old DOS days, when full-color video cards were an unimaginable luxury.

    In the new version, the 13-color restriction has been removed for all objects. Click on the color selection button, and you get a full choice of colors from the standard Windows color selection dialog.

    For certain features, "line styles" can now also be chosen. For example, if you right-click on the horizon, ecliptic, galactic equator, constellation boundaries or lines, or planet trails, and then on "Display", you will see a "Styles..." button. Click on this, and you get a choice of a solid line (the default), dotted, dashed, dash-dot, and so forth. This is mildly pleasant on-screen, but extremely helpful on black and white printouts.

    (26 Feb 2002) Creation of animation (.AVI) files: You can now create animation files from Guide with reasonable ease. To do so, set up Guide to show the first frame of the animation. You'll probably want to resize the screen to make it smaller, since a full-screen animation results in tremendously large files. When you've got things set up, use the "Animation... Make an .AVI" function.

    Guide will ask for the name of the .AVI file to create, and for the compression method to be used. Once you've done this, each screen redraw will result in a frame being added to the .AVI file. So you can bring up the Animation dialog box and start animating as you normally might do, perhaps following the motion of a particular object. While the animation is proceeding, you can stop, switch to different objects, change the animation step size, and so forth.

    When you've completed the animation, go back into "Animation" and toggle off "Make an .AVI". Guide will close the current animation file, and you can view it with Windows Media Player or any similar .AVI-aware utility.

    Examples: Even before this function became available, some Guide users were creating animations, some of which may spark ideas. For example, Masaki Kouda posted the following on the Guide user mailing list:

    I... re-created animation GIF, and MPG file showing Big Dipper proper
    motion during -10000 to +100000. I put them on my site.
    I created 111 GIF files steping 1000-years during -10000 to +100000.
    Image size is 320x240 for MPG format.
    File size of GIF is 305kbyte, MPG file is 648kbyte.
    Please enjoy > All guiders...

    Masaki Kouda also mentioned that he had copied some animations made by Jari Suomela:


    ...which prompted Jari to mention that

    I was very happy with the moon animation because it not only showed
    the phases but also libration and the changing distance from the
    Helsinki-centric observer.
    The funny thing is that my old site still is online, even though my
    account has expired. There's a smaller version of the moon animation
    which can be used as decoration on web pages.

    (26 Feb 2002) Some new isophote controls: You can now right-click on a nebula or Milky Way isophote, much as you can right-click on other objects in Guide to get information about them and to control them. (My goal is to eventually have everything in Guide work in this manner; no matter what it is, you should be able to click on it to at least find out what it is.)

    The dialog box that comes up tells you if you have clicked on a nebula or Milky Way isophote, and offers the usual "next", "more info", "OK", and "Display" options. "More Info" does nothing spectacular: you get a blurb about what isophotes are. "Display" brings up a dialog in which you can choose if the isophotes are off, shown as filled shapes (previously the only option), or as outlined shapes (the new option). Whatever you choose will apply to both Milky Way and nebula isophotes.

    You can also, as with many other datasets, set the "show at" values to indicate the fields of view at which the isophotes can be shown. Note that the Milky Way and nebula isophotes are treated separately here, so you can have nebula isophotes shown at (say) fields of view from zero to 19 degrees, and Milky Way isophotes shown at fields of view of 19 to 181 degrees. (Those values happen to be the default.)

    (26 Feb 2002) Access to DSS-2 via Internet: Previously, you could download any sort of DSS image you wanted, as long as it came from DSS-1. This is the "classic" DSS, scanned mostly from older plates. The server Guide uses to download DSS has offered the newer DSS-2 data for some time, but until now, Guide has ignored these wonders. Both the red and blue DSS-2 survey data are now available in Guide. You can select the survey you want via radio buttons in the "DSS/RealSky Images" dialog.

    Be warned that DSS-2 was scanned at a higher resolution than the original DSS (1 arcsecond per pixel instead of 1.7 arcseconds per pixel). The result is that an image covering a given area from DSS-2 will be about 2.9 times larger than the DSS-1 image. The downloads tend to require some patience.

    Coming up next, of course, will be combining red and blue images to make "color" images. I've got that working, sort of, but it's not really ready for prime time yet.

    (26 Feb 2002) Suppression of spurious GSC stars: You've probably noticed that the GSC database used by Guide (and most astronomy software) is riddled with errors: some stars that really ought to appear do not, and there are plenty of "stars" that would be better omitted. The current version does something about the latter problem.

    I wrote a little piece of code to automatically pattern match the Principal Galaxy Catalogue (PGC) to the GSC. This turned up about 80,000 galaxies that GSC falsely catalogued as stars. If you download this file to your Guide directory (about 126 KBytes) and unZIP it, Guide will use the data to suppress those spurious "stars". This takes care of most, though admittedly not all, of the more annoying false stars: those placed at the center of deep-sky objects.

    If you come across a remaining spurious star that particularly annoys you, note its GSC identifier and edit ERRATA.TXT. This file gives a list of GSC stars that are, for one reason or another, not to be displayed. A few examples are given: nearby stars that weren't properly matched to Hipparcos entries, some more false "stars" from DSOs, some double stars that were recorded once in GSC and got two different entries in GSC, and more. You can add your own, along with a short note so that you can remember exactly why you felt that star was worthy of deletion. And (very important!) you should send your revised ERRATA.TXT back to me so I can combine it with those supplied by others and update it from time to time.

    (26 Feb 2002) Additional data about galaxies in "more info": If you click on a galaxy and ask for "more info", the section devoted to "comments from the PGC" will list some additional data about the distance to the galaxy and its luminosity. The data is available for most of the brighter galaxies, and a few of the more obscure ones.

    Of lesser interest, some color info may also be given for some galaxies.

    (26 Feb 2002) "Motion trails" for asteroids: If you click on an asteroid, then on "Display", and then on "Options", the resulting dialog box now has an edit control for "Trail length". By default, this is zero. Set it to, say, 10, and Guide will add a little "trail" to each asteroid, indicating its motion over the last ten days.

    Showing the apparent motion in this manner can be useful in giving a feel as to which asteroids are headed in which direction, and which are main-belt objects and which are "unusual" (distant or near-earth) objects.