This is the first of two adventures about the total solar
eclipse of July 2, 2019. In this one, we will be watching the
eclipse in the conventional way, from the Earth.
The adventure will start with a series of short videos in
tutorial format, in which we set everything up to watch the
eclipse. You don't have to watch these, but I you want
to learn about how to use the Planetarium, they will be the
most important part. I suggest that you work through the
Stargazing Tutorial before you watch them, at least its first
segment about entering the planetarium for the first time. As
usual for tutorials, I suggest that you open the planetarium
in another window and follow along.
In the last video, we will
just watch the eclipse,
from just before the Moon first overlaps the Sun until just
after totality. That video is intended as standalone, so if
you just want to see what the Planetarium can do, start with
that and just enjoy it.
So enter the planetarium and let us begin!
1. Initial Setup and Location.
Right click to open the Control Panel. I suggest that you
click the "All Defaults" button at the bottom to start from
the default configuration (as I am doing). At least get into
Stargazing mode by setting that in the Mode drop menu at the
Left-click on Viewer Location to open that section. Set
your location to 34.4 degrees S (-34.4) and 141 degrees west
(-141). We can do that by typing in the boxes. Now
left-click on Viewer Location again to close it.
Leave the Control Panel open.
2. Initial Date and Time Setup.
Open Date and Time and left-click Stop Clock. We will
start the clock again When we have everything ready.
Set the timezone offset to 0 so we are all using GMT,
which is UTC + 0 hours.
Set the date to July 2, 2019 (2019-7-2) at about 16:15 hours.
How did I come up with this place and time? First, I want
totality to occur when the Sun is low in the sky, so I can
include the eclipse and the ground in one view. To make
that happen, I want to be far to the west so that the
eclipse will start soon after sunrise. As long as the sun
rises after the moon, before it is eclipsed, there will be
some latitude on which the eclipse will be total. We can
find that latitude by feeling around for it in a systematic
way – adjusting the latitude and the time until we
If you try this yourself, maybe for other eclipses, be
warned that, in the planetarium, positions of objects in the
sky are only accurate to about 1/10 of a degree. If
you compare our positions and times for the eclipse to those
actually observed, they will not be quite right. They may
be off by several degrees and as much as half an hour.
3. Set Sun and Moon to have their real size.
16:15 hours is a good time to start watching the eclipse,
but to continue setup, let's move forward in time to just
after sunrise and move the Sun to where we can see it. It
looks like the Sun is already almost totally eclipsed! But
that's not right.
To see what the problem is, left-click on Planets to open
that section. Sun/Moon magnification is 5, which means that
Sun and Moon appear 5 times larger in diameter than they
should, given where we are and where they are. For a
realistic eclipse, we need to turn Sun/Moon Magnification
down to 1 – no magnification – so that they are
their real size. Otherwise, the eclipse will start much
earlier and last much longer than it really should.
Left-click on Planets to close it again.
Since Sun and moon now look rather small on screen,
let's turn star size down, too, so the brighter stars don't
look as big as the Sun and Moon. We do that by opening the
Star settings and turning Brightness Boost down. Brightness
boost primarily controls how bright stars are, but for
brighter stars, the planetarium replaces brightness by size,
so reducing brightness boost gives the brighter stars a
smaller, more realistic size. Close Stars by left-clicking
on that heading again.
Our tutorial about the Control Panel goes into Planet and
Star settings in more detail.
Now, the Sun and Moon look quite tiny, so let's open
View on the Control Panel and zoom in until Sun and Moon are
a reasonable size. A zoom of 5 would make them
the same size as when we started, but we will use 3.5,
because we want the Sun and Earth both to be onscreen when
the eclipse reaches totality. 3.5 is a number that will
accomplish that. Close View again.
Note that we can see the Moon against the black sky. That
is because the near side of the Moon is enjoying a full
Earth and the light reflected by the Earth faintly
illuminates the Moon.
It also helps that, in the Planetarium, the Sun is not
nearly as bright as it is in the sky, so its light does not
dazzle us when we look at the moon.
Adjust the view so the sun will rise a bit to the right
side of the screen, because it will ascend diagonally across
the middle, more or less parallel to this line of latitude.
Also make sure that the Earth is clearly visible at the
4. Final Setup.
Now let's finish setting up.
Put the time back to 16:15 GMT.
Set the time rate to 60. That way each hour of the
eclipse will go by in just a minute in the planetatium, so
it won't take very long to watch the eclipse.
Finally, I suggest that you open Screen Decorations by
left clicking on that heading. Turn off the Lines, the
Labels, the Direction Markings and possibly the Onscreen
Controls, so that fewer things are cluttering the view. If
you want, keep the Onscreen Controls on so you can see the
time. I will turn them off. Close Screen Decorations by
left clicking on the heading again.
5. Watch the Eclipse.
This section is written to be watched as a stand-alone video,
independent of the preceding sections, so there will be some
repetition of their material.
This video may look better full screen.
We are somewhere in the South Pacific, southwest of
Pitcairn Island. It is just before sunrise on 2 July, 2019
and we are set up to watch a total eclipse of the Sun from
when it first starts to the end of totality.
The clock is stopped. When we start it, the Sun will
rise and the eclipse will begin just after that. The clock
is set to run at 60 times its normal rate – so that
each hour of the eclipse will go by in just one minute.
We start the clock and Dismiss the control panel.
In Planetarium World, we do not model the Earth's
atmosphere, so the sky is always dark, the stars are always
visible, and sunrises are not red, though they can still be
The eclipse is starting.
Note that we can see the moon, faintly illuminated by the
full Earth that is shining on its near side.
What we see on the horizon is some combination of cloud and sea.
As we approach totality, the horizon will gradually get darker.
At totality, it briefly gets very dark -
nighttime dark - until totality ends.
As the Sun and Moon sail off the screen, the eclipse is
ending, so I'll end the video here. Thanks for watching.
Find a place even further southwest where the sun comes up
totally eclipsed. Most total eclipses start when the Sun
comes up somewhere totally eclipsed and end when it goes
down somewhere totally eclipsed.
Look up a recent annular eclipse and try watching that.