Where can I find the positions of the planets, stars, moons, artificial satellites, etc. and visualize them?
What resources are available to find the positions of planets, stars,
moons, artificial satellites, asteroids, and other heavenly bodies?
There are many resources online, so this is a community wiki
answer. Please feel free to add to it!
If you want to visualize the stars/planets/etc (as viewed from Earth
or another location), you are looking for planetarium software:
If you want accurate positions for stars/planets/etc, you are looking
If you want to compute star/planet positions yourself, you have
SPICE (http://naif.jpl.nasa.gov/naif/tutorials.html) will give you
results that match HORIZONS very closely. You can also use some of
SPICE's functionality online at
SPK (Spice kernel) files are available at https://naif.jpl.nasa.gov/pub/naif/generic_kernels/spk/ -- while these are primarily intended for use with CSPICE, the format is documented and you can use it directly. It's described at https://github.com/skyfielders/python-skyfield/issues/19 and implemented in Python at https://github.com/brandon-rhodes/python-jplephem/tree/master/jplephem
If you want to do the SPICE computations yourself (numerically solving the differential equations), see https://astronomy.stackexchange.com/a/13491/21
You might also want to use an n-body simulator to do the computations yourself: https://physics.stackexchange.com/questions/25241/what-open-source-n-body-codes-are-available-and-what-are-their-features
IAU SOFA (http://www.iausofa.org/) will give you the International
Astronomical Union's "official" libraries to compute positions.
VSOP theory (https://en.wikipedia.org/wiki/VSOP_%28planets%29) is
PyEphem (https://en.wikipedia.org/wiki/PyEphem), which derives
from MIT's libastro library
If you want to treat planetary orbits as simple ellipses and ignore perturbations, you can find orbital elements at https://ssd.jpl.nasa.gov/txt/p_elem_t1.txt but you'll probably want to visit https://ssd.jpl.nasa.gov/?bodies#elem first
Note that these computational libraries don't always agree with each
other or with planetarium software:
If you want a catalog of stars/etc, NOMAD
(http://www.usno.navy.mil/USNO/astrometry/optical-IR-prod/nomad) and GAIA (http://gea.esac.esa.int/archive/) are
the largest such catalogs (about 1 billion entries each, lots of overlap). The NOMAD link also provides references to smaller catalogs.
For high-resolution astrophotography try ALADIN (http://aladin.u-strasbg.fr/#AladinLite)
If you want to find artificial satellites and spacecraft, start at
Transits of Mercury and Venus across the Sun? http://eclipse.gsfc.nasa.gov/transit/transit.html
Occultations of stars by asteroids? The International Occultation
Timing Association (IOTA) at http://occultations.org/
Create your own Sun-Earth-Moon model by using a ~17 inches (~44 cm) beach ball or box as the Sun, 4-5 mm object like a pencil eraser as the Earth and a 1 mm sized drill bit or other object to represent the Moon. Then, find a 150-foot string or tape measure. The sun and earth are ~154 feet (~46m) apart. The earth and moon are ~4.7 inches (12 cm) apart.
I also use SIMBAD (http://simbad.u-strasbg.fr/simbad/sim-fid) if I want to do a quick search for a star or galaxy based on its identifier, and you can also do the reverse and searching for coordinates too.
I like this one for seeing what's overhead http://www.ucolick.org/~bolte/AY4_00/weblab/project/chart.html .
That appears to be a framed verison of http://www.fourmilab.ch/yoursky/ -- feel free to add the latter link above.
@uhoh This is a community wiki answer, so please feel free to add them yourself. But, if you run into trouble, let me know and I'll add them.
For Python, `astropy` might be useful here as well: https://docs.astropy.org/en/stable/coordinates/solarsystem.html
To add to the excellent answer by barrycarter, there are 2 planetarium-like codes, that I know of, that run on a mac and would make excellent tools for viewing certain astronomical objects. The codes are Stellarium and Celestia. Both turn your computer into your own planetarium where you can search and view objects in space.
It's actually a public wiki answer (not all my content), so you can add to it directly if you'd like. I had considered listing individual planetarium software (Stellarium is my favorite), but thought linking to the wikipedia list page may be more useful and neutral.