.. note:: :class: sphx-glr-download-link-note Click :ref:`here ` to download the full example code .. rst-class:: sphx-glr-example-title .. _sphx_glr_generated_examples_coordinates_plot_obs-planning.py: =================================================================== Determining and plotting the altitude/azimuth of a celestial object =================================================================== This example demonstrates coordinate transformations and the creation of visibility curves to assist with observing run planning. In this example, we make a `~astropy.coordinates.SkyCoord` instance for M33. The altitude-azimuth coordinates are then found using `astropy.coordinates.EarthLocation` and `astropy.time.Time` objects. This example is meant to demonstrate the capabilities of the `astropy.coordinates` package. For more convenient and/or complex observation planning, consider the `astroplan `_ package. ------------------- *By: Erik Tollerud, Kelle Cruz* *License: BSD* ------------------- Let's suppose you are planning to visit picturesque Bear Mountain State Park in New York, USA. You're bringing your telescope with you (of course), and someone told you M33 is a great target to observe there. You happen to know you're free at 11:00 pm local time, and you want to know if it will be up. Astropy can answer that. Make print work the same in all versions of Python, set up numpy, matplotlib, and use a nicer set of plot parameters: .. code-block:: python import numpy as np import matplotlib.pyplot as plt from astropy.visualization import astropy_mpl_style plt.style.use(astropy_mpl_style) Import the packages necessary for finding coordinates and making coordinate transformations .. code-block:: python import astropy.units as u from astropy.time import Time from astropy.coordinates import SkyCoord, EarthLocation, AltAz `astropy.coordinates.SkyCoord.from_name` uses Simbad to resolve object names and retrieve coordinates. Get the coordinates of M33: .. code-block:: python m33 = SkyCoord.from_name('M33') Use `astropy.coordinates.EarthLocation` to provide the location of Bear Mountain and set the time to 11pm EDT on 2012 July 12: .. code-block:: python bear_mountain = EarthLocation(lat=41.3*u.deg, lon=-74*u.deg, height=390*u.m) utcoffset = -4*u.hour # Eastern Daylight Time time = Time('2012-7-12 23:00:00') - utcoffset `astropy.coordinates.EarthLocation.get_site_names` and `~astropy.coordinates.EarthLocation.get_site_names` can be used to get locations of major observatories. Use `astropy.coordinates` to find the Alt, Az coordinates of M33 at as observed from Bear Mountain at 11pm on 2012 July 12. .. code-block:: python m33altaz = m33.transform_to(AltAz(obstime=time,location=bear_mountain)) print("M33's Altitude = {0.alt:.2}".format(m33altaz)) .. rst-class:: sphx-glr-script-out Out: .. code-block:: none M33's Altitude = 0.13 deg This is helpful since it turns out M33 is barely above the horizon at this time. It's more informative to find M33's airmass over the course of the night. Find the alt,az coordinates of M33 at 100 times evenly spaced between 10pm and 7am EDT: .. code-block:: python midnight = Time('2012-7-13 00:00:00') - utcoffset delta_midnight = np.linspace(-2, 10, 100)*u.hour frame_July13night = AltAz(obstime=midnight+delta_midnight, location=bear_mountain) m33altazs_July13night = m33.transform_to(frame_July13night) convert alt, az to airmass with `~astropy.coordinates.AltAz.secz` attribute: .. code-block:: python m33airmasss_July13night = m33altazs_July13night.secz Plot the airmass as a function of time: .. code-block:: python plt.plot(delta_midnight, m33airmasss_July13night) plt.xlim(-2, 10) plt.ylim(1, 4) plt.xlabel('Hours from EDT Midnight') plt.ylabel('Airmass [Sec(z)]') plt.show() .. image:: /generated/examples/coordinates/images/sphx_glr_plot_obs-planning_001.png :class: sphx-glr-single-img Use `~astropy.coordinates.get_sun` to find the location of the Sun at 1000 evenly spaced times between noon on July 12 and noon on July 13: .. code-block:: python from astropy.coordinates import get_sun delta_midnight = np.linspace(-12, 12, 1000)*u.hour times_July12_to_13 = midnight + delta_midnight frame_July12_to_13 = AltAz(obstime=times_July12_to_13, location=bear_mountain) sunaltazs_July12_to_13 = get_sun(times_July12_to_13).transform_to(frame_July12_to_13) Do the same with `~astropy.coordinates.get_moon` to find when the moon is up. Be aware that this will need to download a 10MB file from the internet to get a precise location of the moon. .. code-block:: python from astropy.coordinates import get_moon moon_July12_to_13 = get_moon(times_July12_to_13) moonaltazs_July12_to_13 = moon_July12_to_13.transform_to(frame_July12_to_13) Find the alt,az coordinates of M33 at those same times: .. code-block:: python m33altazs_July12_to_13 = m33.transform_to(frame_July12_to_13) Make a beautiful figure illustrating nighttime and the altitudes of M33 and the Sun over that time: .. code-block:: python plt.plot(delta_midnight, sunaltazs_July12_to_13.alt, color='r', label='Sun') plt.plot(delta_midnight, moonaltazs_July12_to_13.alt, color=[0.75]*3, ls='--', label='Moon') plt.scatter(delta_midnight, m33altazs_July12_to_13.alt, c=m33altazs_July12_to_13.az, label='M33', lw=0, s=8, cmap='viridis') plt.fill_between(delta_midnight.to('hr').value, 0, 90, sunaltazs_July12_to_13.alt < -0*u.deg, color='0.5', zorder=0) plt.fill_between(delta_midnight.to('hr').value, 0, 90, sunaltazs_July12_to_13.alt < -18*u.deg, color='k', zorder=0) plt.colorbar().set_label('Azimuth [deg]') plt.legend(loc='upper left') plt.xlim(-12, 12) plt.xticks(np.arange(13)*2 -12) plt.ylim(0, 90) plt.xlabel('Hours from EDT Midnight') plt.ylabel('Altitude [deg]') plt.show() .. image:: /generated/examples/coordinates/images/sphx_glr_plot_obs-planning_002.png :class: sphx-glr-single-img **Total running time of the script:** ( 0 minutes 6.903 seconds) .. _sphx_glr_download_generated_examples_coordinates_plot_obs-planning.py: .. only :: html .. container:: sphx-glr-footer :class: sphx-glr-footer-example .. container:: sphx-glr-download :download:`Download Python source code: plot_obs-planning.py ` .. container:: sphx-glr-download :download:`Download Jupyter notebook: plot_obs-planning.ipynb ` .. only:: html .. rst-class:: sphx-glr-signature `Gallery generated by Sphinx-Gallery `_