starmap-northern

To see animated version please go to starmap-northern-animation.

Overview and features

Star map of the northern hemisphere made with Python packages for astronomy: astropy, ephem, pyorbital. It uses matplotlib to render the graphics. Constellations (more accurately, asterisms) and their stars to plot are determined by a user and defined as Python dictionary object. Then, the dedicated script automatically download necessary data (stars coordinates) (SIMBAD database).

The main program puts all constellations forms on the plot and draws over the main plane the field of view: the circle showing the region that observer can see at this time in this geolocation. So, 2 coordinate systems are present: bigger outer circle corresponds to RA-dec (ICRS, equatorial coordinate system, J2000.0 equinox (default for astropy)) and smaller inner circle goes with alt-az (horizontal coordinate system). Additionally, Sun, Moon, Solar system planets and ISS are placed on the plot (if currently located under the northern hemisphere sky).

The small circle is a projection of the field-of-view (FOV) on the big ICRS circle and that's the cause why its form is not an ideal circle and why the altitude axis is curved. Only if an observation location is the North Pole point the FOV will have a round shape and also centers of two circles will fit each other. The more you move away from the North Pole the bigger a distortion of the FOV circle and constellations. The straight line is the celestial meridian. The intersection of two lines is a current zenith.

Note that around the horizon line sky objects are less observable due to the thicker atmosphere and the diffractions phenomena.

The app can be used for educational purposes and planning of astronomical observations.

Requirements

Requirements are listed in requirements.txt file so you can run

$ pip3 install -r requirements.txt

to install them.

• astropy: SIMBAD queries, main coordinates transformations, database file storage
• ephem (pyephem): TLE processing
• pyorbital: TLE querying and processing
• matplotlib: graphics
• geopy: retrieve geolocation by a string from the Internet
• BeautifulSoup4: HTML files handling (used internal by astropy)

Desired (the following packages were used while developing):

• PyQt5
• IPython and Jupyter
• Spyder IDE

Usage

Edit constellations dictionary in dl_constellations.py file to include/exclude desired stars/constellations. Form of the constellation (asterism) is set by the sequence of stars in which that constellation needs to be drawn to get its form. Think of it like about a task where you need to draw some figure, not taking away the pencil from the paper. So of course you can go through the same points and lines where you've already been. For example, let's see Ursa Major ('UMa' code) constellation. For telling the program to draw its Big Dipper (Plough) asterism we need to add following line at constellations OrderedDict:

'UMa': ['η','ζ','ε','δ','γ','β','α','δ']

We see that δ UMa star is included twice as it is point where "dipper" is closing itself.

To download stars' coordinates and form database files run

$ rm stars.html .constellations.html  # start from scratch
$ python3 dl_constellations.py

and wait for completing (it may take tens of minutes). In the end you will see a report that will indicate if some stars hadn't been downloaded. Currently, you must have all stars to be downloaded to successfully make the chart. After writing stars.html and .constellations.html files you can use them for plotting and there is no more needs to start dl_constellations.py.

Also, before starting the main script you can specify some settings e.g. online/local ISS TLE, geolocation, observation time, light/dark style, fonts and markers sizes and so on.

To run main script execute

$ python3 sky_map.py

but it's recommended to use IPython (in a browser or Spyder IDE) instead of pure Python.