SHADOW - a utility to help map Asteroid and Lunar Graze Paths
Asteroids orbiting within our solar system occasionaly move in
front of stars casting a shadow on the earth. If this event is
accurately timed, it can reveal much about the size and orbit of
the asteroid. This is one aspect of astronomy where a "mobile"
person can contribute worthwhile science, with often modest
This webpage offers a freeware utility that allows quick and easy mapping of
the predicted path of an asteroid shadow (or lunar graze).
Shadow path of asteroid "Brita on Jul 12 2005" passing over Christchurch (New Zealand)
- home of Kiwi Geoff. The above map was ccreated in a few seconds by downloading data
from Steve Preston's great
Asteroid Occultation Update service. "SHADOW.EXE" read
Steve's "Detailed info" text file, and created a number of files
for various mapping programs. You can see how the path crosses New Zealand and heads over the horizon towards Tasmania.
Another view of Christchurch, showing how you can get many viewpoints using the wonderful new freeware
Google Earth software.
We can see the middle of Christchurch is halfway between the center of the path (GREEN) and the edge of the Asteroid shadow (BLUE).
A more conventional view of the South Island of N.Z. showing the asteroid path.
SHADOW allows "blink of an eye" creation of waypoints and tracks
for mapping programs or GPS. By prior connection to the
Internet, the latest predictions from Steve (that use the most
recent astrometry) can be obtained. The color code in the above maps is:
GREEN = path center, BLUE = Asteroid shadow limits, RED = 1 sigma error lines.
SHADOW creates the following file formats:
Waypoint Files created: (dots on map)
POINTS.GPX (for EasyGPS etc)
POINTS.WPT (for OziExplorer)
POINTS.DBF (for Precision Mapping Streets, dBASE, Excel, etc)
Track Files created: (lines on map)
TRACK.GPX (for EasyGPS etc)
TRACK.GEN (precursor file for making ESRI shapefiles)
TRACK.PLT (overlay for OziExplorer)
TRACK.CMX (overlay for Precision Mapping Streets)
SA.TXT (overlay for Delorme Street Atlas)
TRACK.MIF (overlay for MS MAPPOINT)
TRACK.GOO (overlay for Google Maps API)
TRACK.KML (overlay for Google EARTH)
WPT and PLT are native formats for
, a popular Moving Map program. The files can also be read by
The DBF and CMX files can be read by
Precision Mapping Streets
- a street-level mapping program of the United States.
The DBF (dBASE format) file can also be read by Excel, dBASE etc.
The file TRACK.GOO is used for
Google Maps API - to allow Interactive Maps on web pages.
The file TRACK.KML is the overlay for the wonderful
Google Earth freeware, as exampled on this page.
Rather than using Moving Map software, if you have a Garmin,
Magellan or Lowrance GPS receiver, you can use the freeware
to transfer the GPX file (created by SHADOW) to the GPS receiver
without manual entry. EasyGPS also allows you to edit the
waypoints. For example you can quickly create a subset of
co-ordinates that are within a defined radius of your location -
so that fewer waypoints are loaded into the GPS.
EasyGPS also connects you to mapping and information sites on
the Internet, giving you one-click access (from a waypoint) to
street and topo maps, aerial photos, weather forecasts, and
If GPX is not your preferred format, you can use
GPSBABEL to convert the GPX file to many
other common formats for your mapping OR GPS device.
If you have Microsoft Streets and Trips or AutoRoute. Tony George has written a
set of instructions to convert the GPX (from SHADOW) to
a file that can be used by Streets and Trips.
After you have downloaded
SHADOW.ZIP (right mouse click, save Target
As) file. Unzip it to a new directory, perhaps called SHADOW.
2. Choose an asteroid event that is near your location.
3. This brings up a new webpage, that contains a link to "Detailed Info".
Right Mouse click on "Detailed Info" and 'Save Target As' PATH.TXT
into the directory on your PC you have used for SHADOW.EXE
4. Run SHADOW.EXE - will automatically detect the lunar or
asteroidal file format and generate data in a form that can be
used with your moving map software, or loaded into your GPS.
For Lunar Graze Path files:
Use WinOccult to generate a lunar graze, the output text format
must be in "DD MM SS" format and the name must be "PATH.TXT" for
SHADOW to auto detect and convert the file. You can also use the
output of "GrazeReg" (2006 version) to make maps. Copy and paste
all the contents from Grazereg to Notepad, and save as 'PATH.TXT'.
Google Earth (using KML created by SHADOW) example graze (green line) over Baja Peninsula (on 22 March 2006)
Screen dump from my Garmin Vista C, after uploading TRACK.GPX to GPS (Graze line in green).
Zooming in (with Vista) near San Jose Del Cabo, where the airport is 10,808 km NEE (65 degrees) of my location in NZ (Graze line in green).
This screens shows how the GPS can be used to measure from any point on the map.
We can see the (green) graze line is 8.6Km south west (214 degrees) from the airport.
Of course the normal use would be to show ones own position (real-time), relative to the graze line.
SHADOW was compiled as a 16bit DOS application, which will also
run in Windows. It does not affect the registry or any system
files, it only reads "path.txt" and creates the above files, in
the directory you run the program from.
I have added (March 2007) various files to the ZIP file to allow a person to make
their own Interactive Google Maps, for their website.
Details can be found in the ZIP archive on how to do this.
Google Earth to create the above maps (except for Garmin screens).
Many thanks to the following:
(Blue Mountains, Australia) who happened to mention to me in
passing that he was trying to get Steve's predictions into his
software - thus I came to write SHADOW.