Copyright © Michael Richmond.
This work is licensed under a Creative Commons License.
In this exercise we will learn how to use a few of the numerous capabilities of a planetarium simulator. There is also one question which will require a bit of research....
Guided Tour of Some of the Software Features
A. Startup.
Launch the application in the normal way. Choose "File", "Open..", then locate and open the file named "RIT Startup". The geographic location and some basic aspects of the display have already been set. To find out the function of any button on any toolbar, press the "Help" (?) button on the top toolbar and then press the button of interest. Update to the current time, using the "Clock" button on the toolbar along the left side of the screen to set the time to "Now" (notice that any other date and time could be chosen at this point). When requested later to "re-initialize", repeat these steps. If at any time your display gets "messed up" because you tried too many things, or the wrong thing at the wrong time, just re-initialize.
B. Viewing the Sky.
The default field of view shows the northern horizon
as an arc along the bottom of the screen and the point directly overhead
(zenith) is at the top of the screen.
Using the toolbar on the left, move along the horizon, East > South
> West > North. Notice that the horizon is marked off in degrees for the
coordinate called azimuth ( 0° = N, 90° = E, 180° =
S, 270° = W). The additional lines on the sky are the
celestial
equator and the ecliptic. The horizon, celestial equator, and
the ecliptic are key great circles in the alt-azimuth, equatorial,
and ecliptic coordinate systems, respectively. The remaining grid
lines can be toggled on and off using the lower toolbar on the right. Experiment
with these, and then return to having only the original three lines displayed.
You can "move your eyes" up, down, right and left using the arrow buttons
on the lower part of the left toolbar.
C. Sky Changes During the Evening and from Night to Night.
The time for the display can be set forward or backward
by certain intervals using the ( < > ) buttons near the
center of the toolbar at the top of the screen. The time unit can be chosen
in the window and the number of units per step to be applied is shown to
the left of the window. Set the time step to be one hour. Facing north,
with the horizon visible, repeatedly advance the time forward and note
the motion of the stars. Return to the original time, and repeat the process
as you face east, then south, and then west. Note the motion of the stars
in each case.
Now set the time step to one day (not sidereal day),
and repeat to see the night to night changes. Now set the time step to
one sidereal day, and repeat. This process is good for showing the motion
of the sun, moon and planets against the star background.
D. The Sky as Viewed from Different Locations at the Same Time.
Face south and turn on the alt-azimuth grid. Note the constellations that are on the meridian (vertical line at 180 azimuth). Now let's look at the sky as seen from somewhere else in the Eastern Time Zone. Choose Bangor, ME from the list of cities obtained by clicking the globe button on the left toolbar. Notice the change of position of the constellations from where they are as viewed from Rochester, NY. Is the change what you expected? Try going to a city west of here, say Denver, CO or Los Angeles, CA, but remember to adjust the time also since the time of the display is local time. Now return to Rochester, NY and face north. Turn off the alt-azimuth grid (leave the horizon) and turn on the equatorial grid. Note the position of the north celestial pole above the horizon. Now travel to Miami, FL and note the change.
E. Changing the Field of View of the Display.
Open "RIT Startup" and set the display for the current time. To see your entire sky, click on "Z" (for zenith) in the left toolbar. The circle represents your horizon and anything within it is in your sky, just like a planisphere. Turn off all grids and lines except the horizon. Repeatedly advance in time and notice that the sky rotates counter-clockwise about the north celestial pole. Notice the rising and setting of constellations and the motions near the southern horizon.
Now re-initialize. At the left end of the top toolbar, there are "zoom-in", "zoom-out", and "lock" buttons. With the "lock" button activated, the settings for the display remain unchanged when zooming in or out. Try some zooming with the lock "on". With the lock "off", the display changes as you progress to different zoom "levels" to their default settings. Fainter stars and other objects are displayed, as well as constellation boundaries, coordinate grids, scale bars, etc., depending on the level. Try some zooming with the lock "off".
F. Searching for Objects.
To locate a named object, like the moon, and place
it at the center of the display, use the "Search.." menu. When you "goto"
the object, there will be a small square superimposed on the location of
the object. The object may be fainter than your display is presently set
to show. Remove the square by choosing "Remove Search Target" from the
"View" menu.
You can also center on specific equatorial coordinates
and specify the field of view to be displayed. This is achieved using the
button on the left toolbar below the clock button.
G. Coordinates, Angular Distances, and Directions on the Sky.
Coordinates for the cursor's position on the sky
are displayed at the bottom center of the screen. The coordinates are updated
as you move the cursor. The left-most box contains the altitude and azimuth
of the horizon coordinate system. The longer box to its right gives the
Right Ascension and Declination of the equatorial coordinate system. Turn
on one coordinate grid at a time and verify that the coordinates match.
The leftmost box at the bottom of
the screen gives the zoom level.
Click the left mouse button over any point in the sky. Move to a second
point and again click the left mouse button. The angular separation and
position angle are displayed in the box to the right of the one showing
the zoom level. The position angle is the angle, measured eastward, between
the north-south line and the line drawn from the first point to the second
point.
At low zoom levels, you may be able to tell which
direction would be east or north of your present position. In various other
display settings it is not so easy to tell. You can add a "compass" to
the display by choosing the "Compass" button on the right toolbar. It is
located below the coordinate grid buttons.
H. Object Data
Placing the cursor over an object and clicking the right mouse button brings up a page containing a wide variety of information about that object. Look at information given about a star, the moon, and a planet. This data can be copied to the clipboard and placed in a word processor of your choice for editing and printing.
I. Field of View Through a Telescope.
When using a telescope, the magnification and field of view depend on the telescope-eyepiece combination. You can choose a specific telescope and specific eyepiece using the "Telescope" icon on the top toolbar (not the "Telescope" menu item!), or by choosing the "Insert" menu item and then clicking on "Eyepiece". A circle, showing the field of view, will appear at the center of the screen. A square is superimposed over the circle. The field of view can be moved by placing the cursor inside the square and, holding down the left mouse button, dragging the circle to a new location. Clicking the mouse when the cursor is outside the square will leave the circle in place. The circle can no longer be moved. It may be removed by choosing "Clean Up Map" in the "View" menu.
J. Planetary Disks and Satellites.
The default setting displays planets based on brightness
(magnitude). As you go to high zoom levels (with the zoom lock off), the
display switches to show the correctly sized disk and abbreviations for
the satellite names. (To force the disks to be shown to scale at lower
zoom levels, choose the button on the right toolbar that looks like a crescent
moon. Choose "Correctly-sized outlines".) After "searching" for a planet
to bring it to the center of the display, begin to "zoom in" with the "lock"
off, until the view looks reasonable. Advance the time and note the motion
of the satellites.
Exercises to be done and turned in to the instructor.
Use only SkyMap Pro to answer these questions:
The previous question involves the planet Mars, which is probably the only planet that we'll have a chance to observe this quarter (alas). We'll spend more time on Mars later, but I would like you to do a little research in preparation. There have been a number of recent space missions to the Red Planet, and more still are planned. This is good news for people who want to learn more about our neighbor in space!
Copyright © Michael Richmond.
This work is licensed under a Creative Commons License.