One of the first things you will
need to learn as a new stargazer, is how to locate planets, stars and
constellations in the night sky. However, what you see in books, charts
and planetariums doesn't always translate to what you actually see.
Part of the problem is due to light pollution. .Thus, when you look
for the constellation Leo, you can not always find it because some of
the stars that form it are not very visible so it is hard to "connect
the dots." With a PDA, you can use the Alt-Az coordinate system
to help you locate it.
To use a PDA to find your celestial object of choice:
ONE - Install a planetarium software program onto your PDA and
set it for your location and time. It will have a data base of cities
you can choose with associated longitude and latitude. Some will also
permit you to enter the coordinates yourself. Be sure to adjust for
daylight savings time if it is in effect. (Chabot Space & Science
Center's location is about 37 degrees 49 :minutes North latitude, and
-122 degrees 11 minutes West longitude.)
TWO - Face North. If you are unable to see Polaris, the North
Star, use a compass. Be sure to adjust for the magnetic declination
for your locality as Magnetic North is different from true North. Not
all compasses will permit you to do this. Brunton has a model that allows
you to adjust the declination. It is the Brunton 9020G Classic that
sells for $11 at REI. The declination
for Oakland is about 12 degrees East.
THREE -. Once you face North, enter the celestial object of choice
on your PDA and request the Altitude-Azimuth (Alt-Az) coordinates. You
will get the azimuth coordinate first, then the altitude coordinate.
The azimuth is the compass position and the altitude is the angle position.
North is Az 0 degrees, East is 90 degrees, South, 180 degrees and of
course West, 270 degrees. The imaginary horizon is Alt 0 degrees and
the zenith (directly over head) is 90 degrees. So, for my current location
and time, the Alt-Az coordinates for Jupiter is Az: 344:51; Alt -32:41.
Thus, it is in the Northwestern (almost North) skies but below the horizon.
The Alt-AZ coordinates for the constellation Andromeda is Az: 070:24;
Alt 43:53. Thus, it is roughtly in the East-Northeastern skies.
Remember that the earth is rotating so the objects will move as time
passes. When the PDA gives you the Alt-Az coordinates for Jupiter, it
will only be for that period of time. Tap the software program's current
time panel an hour later and you will see the coordinates for it will
FOUR - PDAs run under either the Palm or Windows CE operating
system. There are planetariums for both OSs and are downloaded from
commercial web sites. For the Palm OS, two popular programs are "Planetarium
for Palm Pilot" and "2Sky." For the Win CE OS, two programs
you can try are "The Sky Pocket Edition" and "Pocket
Deepsky 2003." All four have the ability to add extensive data
bases to them. "Pocket Deepsky 2003" is a mini-program within
"Deepsky 2003." (An attractive scaled-down program for the
Win CE OS PDA is "Pocket Universe." It is visually attractive
and intuitive to use and learn. The developer provides a demo for you
to download.) Go to any of the developers' web site to look at a program's
screen shots and learn more about it's features.
To get to their web site, go to:
Scroll down half way until you see a hand holding a PDA. You will see
there are other PDA planetariums. Click on one of them and you'll be
taken to the developer's website. Be sure to check the minimum systems
requirements to determine if the program will run on your PDA.
OK, so go out, have fun and be amazed at the wonder of our beautiful