Starry Night FAQ
Frequently Asked Questions For Starry Night
Starry Night Pro FAQ
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Open the Planets Palette if it is not already open by choosing "Window | Planets".
Click on the moon's name in this list and then click on the little lock icon
to lock on the moon. If you get a message saying that the moon is beneath the
horizon, click the "Reset Time" button. Zoom in on the moon if you want a closer
look. Now change the timestep in the Time Palette to 1 day. Use the Single Step
Forward button to watch the moon's phase change day-by-day. You may have to
hide the horizon by choosing "Sky | Horizon" to keep the moon in view.
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The position of the eight major planets should be accurate to within 5 arcseconds
for times within 3000 years of the present. The theory used to predict Pluto’s
position is less accurate: between the years 1885 and 2099, its position is
accurate to within 1 arcsecond, but the accuracy will decline significantly
outside these dates. The position of our moon should be accurate to within 10
arcseconds for several thousand years in either direction. The theories used
to predict the positions of other moons are simpler and therefore potentially
less accurate.
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Starry Night Pro uses a file called "JupiterGRS.txt" located in the Starry
Night Pro Data folder to determine the mean longitude of the GRS. To change
the GRS's position you can open this file and enter a new mean longitude. The
GRS drifts non-algorithmically so the GRS mean longitude will need to be updated
from time to time. The latest
mean longitude is available from Sky & Telescope's excellent Great Red
Spot web page.
The mean longitude as stated in the "JupiterGRS.txt" file assumes that the
surface image of Jupiter that is being used by Starry Night Pro has the GRS
in a specific location. The surface image of Jupiter as shipped with Starry
Night Pro does NOT have the GRS in the right location. To update this picture,
download a new Jupiter
surface picture for Windows or a new Jupiter
surface picture for Macintosh, then replace "Starry Night Pro Data | Planet
Images | Jupiter.pct" with the newly downloaded "Jupiter.pct".
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The orbits of Pluto and Neptune do overlap. However, because the orbit of Pluto
is tilted at an angle to that of Neptune, it can appear from your perspective
that Pluto is always outside Neptune. A neat way to see this is as follows:
Choose "Go | Solar System" and rotate your view so that you are directly over
the north pole of the sun looking back down on the solar system. The orbit of
Pluto will appear to be completely outside the orbit of Neptune. Now blast off
using the rocketship button until you are about 3000 AU above the sun. Use the
zoom button to enlarge your view so you can clearly see the two orbits. Now
you can see that Pluto's orbit does come within that of Neptune. The "correct"
view of the orbits can only be seen when you are very far away, and the effect
of Pluto's tilt is small compared to this distance.
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Unfortunately, predicting comet positions on past trips around the sun is one
area of astronomy where simulation programs like Starry Night are not very effective.
When a comet is far from the sun, its orbit is altered by the gravitational
influence of thousands of other comets in ways that can't be predicted by Starry
Night (because these other comets are also far from the Sun and most are not
even known). The gravity of these other comets will cause the orbit of the comet
you are interested in to change. For example, the orbital period of Halley's
comet has varied from 76 years to 79 years over the last thousand years. The
bottom line is that the orbital elements for a comet in Starry Night are valid
only for its most recent trip around the sun and can't be used to predict its
appearance in the more distant past.
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With Starry Night, you can add Solar System objects such as asteroids, satellites
and newly discovered comets using the Orbit Editor. For more information, refer
to the Starry Night Pro User's Guide. You can also download the latest comet,
satellite
and asteroid
files which have updated orbital elements for the 100 or so most prominent of
each of these objects.
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See our Orbital Elements Page for this information.
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The orbital elements of artificial satellites (including the ISS) are constantly being adjusted slightly. You need to update satellite elements on a regular basis to keep the satellites in their proper position. You do this by choosing "File->Preferences->Startup" from the Starry Night menu and clicking the "Update Now" button, which will download new elements from our website. You need to close and reopen Starry Night before it will use the new elements.
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The file "Prefs.txt" in the "Starry Night Pro\Starry Night Pro Data\Prefs\Pro" folder has fields named "MaxNumOfAsteroids", "MaxNumOfComets", "MaxNumOfSatellites" and Starry Night will only read in a number of objects equal to the values in these fields. You can change the values of these fields to read in more objects (this may slow the program down if you read in too many objects).
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This feature will not work properly under certain conditions. If you are
connected to the Internet via a proxy server, you will be unable to use this
feature. We plan to add proxy support for a future version of Starry Night.
If you are on a Macintosh, you need to be using operating system 8.6 or
later for the auto-update feature to work. The auto-update feature uses a
new tool called the URL Access Manager, which is new in System 8.6.
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