You unless you are a quick study, you should work through the
tutorials on Stargazing and Space Travel before you do this one. I
will assume that you are familiar with the concepts introduced in
those tutorials and if something on the control panel does the same
thing as something we covered in those tutorials, I will just say so
and maybe show it, but I won't do much explaining.
I suggest that you open the Planetarium in another browser window and
follow the tutorial there.
The basic principle about the Control Panel is that you can
control everything using the Control Panel. (The position of
the point at the center of the screen, top right in the on-screen
controls, is not on the control panel, but then, it is not something
that we control.)
There are some important things that you can do using the Control
Panel but not using only the mouse and on-screen controls. Special
abilities of the Control Panel are important in the adventure videos
about the Total Solar Eclipse.
1. The Basics of using the Control Panel
We open or close the Control Panel by right-clicking the
mouse. We can also close it by pressing the Dismiss button at
the bottom of the Control Panel.
You can drag the Control Panel by holding down the left
mouse button on its title bar. This may not work with touch
We open or close a section of the Control Panel by
clicking the left mouse button on ts heading.
In this tutorial we will go through the Control Panel
section by section and look at its capabilities in both
modes, Stargazing and Space Travel.
To start, I suggest that you set defaults by pressing the
"All Defaults" button at the bottom of the Control Panel.
Or at least set Stargazing mode since we will start each
section in that mode.
Before continuing with the tutorial, go through the
whole control panel, in both Stargazing and Space Travel modes.
Try all the settings and see if you can understand what they do.
2. Viewer location – stargazing mode
Open Viewer Location by left-clicking on it.
In Stargazing mode, using this section is the only way to
change your location.
You can set latitude or longitude by using the
sliders, by clicking or pressing and holding the adjustment
arrows in the boxes, or by typing into the boxes.
If you type something wrong into the boxes and get an
undefined position, you can rescue yourself by using the
If you have access to a geolocation service and you gave
the Planetarium permission to access your location, you can
set your position by pressing Set From Geolocation. If not,
then nothing will happen when you press that button. The
first time you use geolocation, it may take a little while.
Your browser will probably cache the results of
geolocation, so if you move to a new place, you may need to
restart your browser for geolocation to set your new
3. Viewer location – space travel mode
Switch to Space Travel mode.
Home Planet is which planet we are on, same as the "H:"
button at lower right.
When our home planet is Earth, Set
From Geolocation is still available, but if we change to
any other home planet, the button disappears.
There is a new setting, Position Type. It selects either
Fixed or Floating style of position, the same as the button
at lower left. The two controls always have the same value.
The other new setting is Altitude. It indicates our
distance from the center of the planet, measured in radii of
the planet. The minimum altitude is 1, meaning that we are
on, or actually just above, the surface of the planet.
We can control altitude either here or by using the mouse
wheel, as we did in the space travel tutorial.
"Turning over" our planet by left-dragging on it is
another way to change our latitude and longitude, though it
is not as accurate as using the Control Panel.
Close Viewer Location.
4. View in Stargazing Mode
Change back to Stargazing mode and open View.
Elevation is looking up or down –
the same as left-dragging the mouse vertically.
Rotation is turning around on the spot, like left-dragging
Zoom tells us how many times the view is magnified.
Elevation and rotation form alt-azimuth coorinates. That
means that rotation (azimuth) 0° is North and the
angle of rotation increases as we turn clockwise.
View Planet is a menu that selects a planet to look at,
the same as the "V:" button at lower right.
Most settings will be preserved when you reload the
planetarium page, or leave it and revisit it later, but the zoom
will be reduced to at most 5 if you do that. The reasons
for this will be given in the section on Date and Time.
5. View in Space Travel Mode
Switch to Space Travel mode.
We can control Roll precisely. Roll 0° is Earth
level beneath our feet.
In Space Travel mode, View Planet still does the same
thing as the "V:" menu at lower right. In particular, it
orients the planet so north pole is at the top.
The Tracking menu does the same thing as the "Tr:" menu as
Restore View Defaults also sets Roll to 0° and
turns Tracking off.
6. Date and Time
Close View and open Date and Time.
The Data and Time settings are the same in Space Travel
and Stargazing mode.
We see some things that are the same as the onscreen
controls at upper left. Let's look at the things
that are new.
There is an extra time field, for seconds. It is only
updated when planetary positions are updated. At zoom 1,
that is once every 5 clock seconds. We update planet positions
proportionally more often as zoom increases, up to at most
10 times a second. That keeps movement of the sky and planets
reasonably smooth. But, of course, the seconds field will
never be updated more than once per clock second.
You can set the clock's timezone offset from UTC. You would
usually do that if you want to view some astronomical event,
like an eclipse, and the time you have for it is in GMT (=
UTC + 0) or some other timezone. Offsets of all existing
timezones are supported. The granularity is a quarter hour.
Note that 9.25 means 9 hours and 15 minutes, not 9 hours and
When you want to go back to local time, press Use Local
Time, don't just set the timezone offset. When you press
Use Local Time, the Planetarium will know that it is on
local time, and it can automatically change to or from
Daylight Saving Time, or whatever summer time is called
where you are, at the correct moment.
You can set the time rate to make the clock run faster.
Pressing "Set Rate To 1" sets the time rate back to normal,
which means that one second of real time equals one second
of Planetarium time.
If you have some time-consuming setup to do, but don't
want planetarium time to change while you are doing it,
press Stop Clock. When you restart the clock, it will start
running again with whatever rate you have set.
Besides setting the current time, Use Real Time sets the
time rate to 1 and starts the clock. It does not set
local time. The Real Time button onscreen does the same
things as Use Real Time.
One last thing: Suppose you reload the planetarium page or
leave it in any way – close your browser, close the
tab, or navigate to another page – and revisit the
planetarium later. Then:
If you are in Real Time when you close the
Planetarium, you will be in Real Time when you open it
Otherwise you will have the same time on the clock,
and the same clock state (stopped or started) as when
you closed the Planetarium.
In either case, the Timezone Offset will not change.
If the clock rate is more than 1 when the planetarium
page loads, it will be reduced to 1. Otherwise it will
stay the same. If you still want a higher clock rate,
you will need to set it again.
Likewise, when we load the planetarium page, if
zoom is more than 5, we set it to 5. Otherwise it stays
We treat clock rate and zoom like this for the following reason:
At clock rate 1 and zoom 1, if nothing else is
happening, the planetarium refreshes the screen once
every five seconds. As clock rate or zoom increase,
the planetarium increases the refresh rate
proportional to rate times zoom, up to 10 times per
On some devices, refreshing 10 times per second
may eat up most of the cycles. The planetarium
doesn't have a good way to detect that problem, but
if you react in the most reasonable way, by leaving
the page, then when you come back, the planetarium
will be refreshing at most once per second and the
problem should be gone. If it is not gone, you
should probably use a different device to run the
7. Planet Settings – Stargazing
Get into Stargazing mode and Open Planets.
We have three settings: How much planets are magnified,
how much Sun and Moon are magnified, and how bright the Sun
is. Why do we need them?
There are two problems with representing
the sky on a computer screen.
The sky is big and the screen is not very big.
Stars and planets appear very small in the sky but are
often very bright. A computer screen is not very bright
– only about as bright as a white sheet of paper.
To understand the first problem, let's view the Sun. It
looks a reasonable size onscreen. But according to the
second line under Planets, it has been magnified 5 times.
Let's turn its magnification down to 1 – no
magnification. Yes, that is really how big the Sun is in
the sky – about half a degree across. We could zoom
in to bring the Sun back up to a reasonable size, but then
we wouldn't see much else. Try that for yourself.
Press Restore Planet Defaults.
We don't have really have any issue about how bright the
Sun and Moon look onscreen. They don't look nearly as
bright as they really are, but they look bright enough.
For stars and planets, we can't make them bright enough to
see at their true size, so we have to make up for it by making
The first line under Planets says that planets in general
are magnified 40 times. Not the Sun and Moon, which are
only magnified 5 times, and not the Earth, which is not
magnified at all, because it does not need it. All the
If we try this with a prominent planet, like Venus, we
will see how it works. With no magnification, we can't even
The last setting, Sun Brightness, does not control how
bright the Sun looks, but how brightly it shines on the
planets. If we view a prominent planet, like Jupiter, and
turn Sun brightness down and up, we see how it works. You
made want to adjust Sun Brightness depending on what you are
Press restore planet defaults and let's go on.
View the Sun. (If necessary, change the time or your
location so it is in the sky.) Turn Sun/Moon Magnification
down to 1 and zoom up to 5. Sun and Moon will be the right
size, but how many constellations can you see?
Set zoom to 1. View Jupiter. Turn Planet Magnification
down to 1, then to 10, 20, and back to 40. Which do you
like best for "normal" viewing?
View Jupiter and zoom in so you can see its bands. Now
turn Sun Brightness down to its lowest value, 0.5, then up
to its highest value, 10, then back down to the default, 3.
Sun Brightness setting do you like best? Turn zoom back
down to 1.
8. Planet Settings – Space Travel
Restore Planet Defaults, if you need to, and set Space Travel mode.
The basic ideas are the same as in Stargazing, but there
some differences about what magnification applies to what
planets, depending on what your home planet is.
Your home planet is never magnified.
Change Home Planet to the Moon. Now the Sun
and Earth are magnified 5 times, or whatever the
second line says.
If your Home Planet is some other planet, like Mars, only
the Sun is magnified according to the second line. Earth
and Moon are ordinary planets and are magnified according to
the Planet Magnification line, by default 40 times.
Change Home Planet to Sun. Because the Sun is our home
planet, it is not magnified, so the Sun/Moon Magnification
line disappears altogether. Nevertheless, if we press
Restore Planet Defaults, the second-line magnification will
be set to 5.
9. Star Settings
Set Stargazing mode. Leave
Planets open and open Stars. Close any other sections of
the Control Panel.
We treat stars like this:
All stars have the same base size.
Each star has a brightness derived from its magnitude.
We multiply this number by the Brightness
Boost to get an ideal brightness for the star.
If we cannot make the star that bright on a computer
screen (without changing its color), we make up the
difference by increasing the size of the star.
Therefore, if we increase Brightness Boost, dim stars will
get brighter. Stars that are already at the full brightness
will get bigger. The
reverse happens when we turn Brightness Boost down.
As an example, view the Sun. Turn Sun/Moon Magnification
down to 1, no magnification. The Sun does not look much
bigger than a fairly bright star, such as Fomalhaut. If you
find that embarrassing, as I sometimes do, turn Brightness
Boost down, too, say to about 10. That looks better, but then
you can hardly see most stars.
Restore Planet Defaults and Restore Star Defaults and
let's look at Color Level.
Stars have a color in the range
red-orange-yellow-white-blue. Color Level controls how
strong we make those colors.
At 0 stars are all white. At 10 there are some very
strong reds, oranges, yellows and blues.
Restore star defaults close Stars and Planets..
Set a date and time when the Sun and Sirius (α in
Canis Major) are both in the sky. (June 1 should be a good
date. Turn labels on to help you find the Sun and Sirius.)
Turn Sun/Moon magnification down to 1. Adjust
Brightness Boost so Sirius does not look much too large
compared to the Sun. How many other stars can you still see?
Restore planet defaults and star defaults.
Turn the Color Level (under Stars) up to 10 and have a
look around the sky. See which stars and star colors you
like best. Restore star defaults.
10. Screen Decorations
Open Screen Decorations.
The settings here are mostly self-explanatory. For most,
you will see what they do if you just try them. There are
some suggestions in the exercises.
The Label Colors setting will not change back to the
default if you press Restore Decoration Defaults. The
Planetarium assumes that that setting is a preference you
want to keep.
Direction Markings are the letters along the horizon,
which indicate the compass points. In Space Travel mode,
they disappear once you are off the surface of your home
You can turn off on-screen controls if you would rather
just use the Control Panel or if you want to take a
screenshot of the planetarium window and don't want them
cluttering it up.
Open the Control Panel and the Screen Decorations section.
Turn lines on and off using the Control Panel setting.
Turn on labels and try both Label Colors settings. Keep
whichever you like best. Turn labels off using the Control
In Stargazing mode, find the Direction Markings near the
horizon and turn them off and back on using the Control Panel
Set Space Travel mode, go to another planet, check that
Direction Markings are there, and then turn them off and on by
increasing and decreasing your altitude.
11. Changing Modes
In Space Travel mode, there are some settings that do not
appear on the Control Panel in Stargazing mode, but can be
thought of being there invisibly, with default values.
Home Planet (Earth).
Under Viewer Location: Position Type (Fixed), Altitude
Under View: Roll (0.0), Tracking (None).
When you change from Space Travel mode to Stargazing,
these settings implicitly get their default values. If you
change back again to Space Travel mode, they will have those
12. All Defaults
The All Defaults button at the bottom of the Control Panel, does the
Sets Stargazing mode, if not already set.
Viewer Location: Sets Latitude and Longitude using Set
From Geolocation. If Geolocation is not
available or not allowed, Latitude and Longitude will
View: Has the same effect of as
Restore View Defaults.
Date and Time: Has the combined effect of Use Real
Time and Use Local Time.
Combined effect of Restore Planet Defaults, Restore
Star Defaults, and Restore Decoration Defaults.
Exercise: Check this for yourself by changing various
settings and pressing All Defaults.
Here is a list of things you must use the Control Panel to do.