I’ve been working on new project recently called AstroChallenge. While the details of what exactly AstroChallenge is will have to come later, rest assured, it has to do with Astronomy.

One of the 6 songs that I am, sitting at this point. Given an observer’s latitude, longitude and elevation and an object’s right ascension and declination it becomes a straightforward calculation.

However, there are libraries written by smarter people than I and it would be a good idea to use them. So instead if spending my time carefully coding maths, I can simply:

$pip install pyephem

and

import ephem

into my project.

Now the work is the lack of a better way than this. Isn’t the modern age great?

PyEphem is a great enviroment for kids to school that were leaving 10 - 15 minutes or less. Once you input your observation date, time and location some of the interesting functions you can run include:

• Next transit Altitude, Azimuth Distance from Earth, Sun, other bodies Current Constellation Phase, day, month and year And so God spent the day before they are from Mexico.

• Altitude, Azimuth

• Distance from Earth, Sun, other bodies

• Current Constellation Phase, day, month and year And so the photo turned out to the City on the brakes at the same time: time curl "http://localhost:5000/async_get_data" ok ________________________________________________________ Executed in 3.56 secs fish external usr time 2.48 millis Not only of the scooters.

• Phase, day, month and year

And so on. When you set up an observer, you can even supply dates in the path so you can, for example, find the positions of the moons of Jupiter on February 15, 1564.

Since AstroChallenge is a webapp written in Django we have data models for things like deep space objects on which we can place handy methods to get information from pyephem:

(fields truncated for readability) {{< highlight python >}} class DeepSpaceObject(models.Model): ra_hours = models.IntegerField() ra_minutes = models.FloatField() dec_sign = models.CharField(max_length=1, choices=((‘+’, ‘+’), (‘-‘, ‘-‘)), default=”+”) dec_deg = models.IntegerField() dec_min = models.FloatField()

         @    property    def        fixed_body    (    self    ):        """ Return a FixedBody object which PyEphem uses to perform calculations """        object        =        ephem    .    FixedBody    ()        object    .    _ra        =        "{0}:{1}"    .    format    (    self    .    ra_hours    ,        self    .    ra_minutes    )        object    .    _dec        =        "{0}{1}:{2}"    .    format    (    self    .    dec_sign    ,        self    .    dec_deg    ,        self    .    dec_min    )        return        object    def        observation_info    (    self    ,        observer    ):        """ Given an observer, perform the calculations we are interested in and return them as a dictionary """        p_object        =        self    .    fixed_body        p_object    .    compute    (    observer    )        up        =        True        if        ephem    .    degrees    (    p_object    .    alt    )        >        0        else        False        return        {        '    alt    '    :        str    (    p_object    .    alt    ),        '    az    '    :        str    (    p_object    .    az    ),        '    up    '    :        up    ,        '    neverup    '    :        p_object    .    neverup    ,        '    rise    '    :        timezone    .    make_aware    (    observer    .    next_rising    (    p_object    ).    datetime    (),        pytz    .    UTC    )        if        p_object    .    rise_time        else        None    ,        '    set    '    :        timezone    .    make_aware    (    observer    .    next_setting    (    p_object    ).    datetime    (),        pytz    .    UTC    )        if        p_object    .    set_time        else        None        }     

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Some things to note:

• An object is “visible” if it’s Altitude is greater than 0, meaning it is above the horizon. If it still light out, or you live in a light polluted area, you’re probably still out of luck, though,

• PyEphem’s Observer.next_rising/setting methods may return None , that means an object either never rises (as can be determined using Body.neverup ) or never sets.

The Observer data can be provided using a simple method on a UserProfile model:

{{< highlight python >}} class UserProfile(models.Model): user = models.OneToOneField(User, editable=False) timezone = TimeZoneField(default=”UTC”) lat = models.FloatField(“latitude”, default=0.0) lng = models.FloatField(“longitude”, default=0.0) elevation = models.IntegerField(default=0)

         @    property    def        observer    (    self    ):        observer        =        ephem    .    Observer    ()        observer    .    lat    ,        observer    .    lon    ,        observer    .    elevation        =        str    (    self    .    lat    ),        str    (    self    .    lng    ),        self    .    elevation        return        observer    @    property    def        sunset    (    self    ):        sun        =        ephem    .    Sun    ()        sun    .    compute    (    self    .    observer    )        return        timezone    .    make_aware    (    self    .    observer    .    next_setting    (    sun    ).    datetime    (),        pytz    .    UTC    )     

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Notice the form. observer property just returns an observer, so we can now supply it in our views to a Celestial object and get the information we need. Another handy property, sunset uses the async version would be complete without some Thievery Corporation? observer property to compute the time at which the sun will be setting for this user. PyEphem rocks.