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# Getting Started

## General Guidelines

`astroplan` is based on astropy and was built around the creation of Python objects that contain all the information needed to perform certain tasks. You, the user, will create and manipulate these objects to plan your observation. For instance, an `Target` object contains information associated with targets, such as right ascension, declination, etc.

Objects representing celestial bodies like stars (which, if we ignore proper motion, are fixed on the celestial sphere) are created (or “instantiated”) via an `FixedTarget` object:

    from astropy.coordinates import SkyCoord
    from astroplan import FixedTarget

    coordinates = SkyCoord('19h50m47.6s', '+08d52m12.0s', frame='icrs')
    altair = FixedTarget(name='Altair', coord=coordinates)

Alternatively, for objects known to the CDS name resolver, you can quickly retrieve their coordinates with `from_name`:

    altair = FixedTarget.from_name('Altair')

Similarly, an `Observer` object contains information about the observatory, telescope or place where you are observing, such as longitude, latitude, elevation and other optional parameters. You can initialize an `Observer` object via the `at_site` class method:

    from astroplan import Observer
    observer = Observer.at_site('subaru')

Or you can specify your own location parameters:

    import astropy.units as u
    from astropy.coordinates import EarthLocation
    from pytz import timezone
    from astroplan import Observer

    longitude = '-155d28m48.900s'
    latitude = '+19d49m42.600s'
    elevation = 4163 * u.m
    location = EarthLocation.from_geodetic(longitude, latitude, elevation)

    observer = Observer(name='Subaru Telescope',
                   location=location,
                   pressure=0.615 * u.bar,
                   relative_humidity=0.11,
                   temperature=0 * u.deg_C,
                   timezone=timezone('US/Hawaii'),
                   description="Subaru Telescope on Maunakea, Hawaii")

`astroplan` makes heavy use of certain astropy machinery, including the `coordinates` objects and transformations and `units`. Most importantly for basic use of `astroplan` is the representation of dates/times as `Time` objects (note that these are in the UTC timezone by default):

    from astropy.time import Time
    time = Time(['2015-06-16 06:00:00'])

## Doing More

Now that you know the basics of working with `astroplan`, check out our Tutorials page for high-level examples of using `astroplan`, as well as the Reference/API section for more exhaustive documentation and lower-level usage examples.