chore(deps): bump skyfield from 1.21 to 1.31

[dependabot-preview]

Bumps skyfield from 1.21 to 1.31.

Changelog

Sourced from skyfield's changelog.

1.31 — 2020 October 24

• Skyfield now uses the International Earth Rotation Service (IERS) file finals2000A.all for updated ∆T and leap seconds. The USNO is no longer updating the files deltat.data and deltat.preds that previous versions of Skyfield used, and the cddis.nasa.gov server from which they were fetched will discontinue anonymous FTP on 2020 October 31. See downloading-timescale-files. #452 #464
• The comets dataframe built from the MPC file CometEls.txt now includes the reference column, so users can tell which orbit is most recent if there are several orbits for a single comet. (For example, the file currently lists two C/2020 F3 (NEOWISE) orbits.) The comet examples in the documentation now build a dataframe that only includes the most recent orbit for each comet. #463
• Two new methods ~skyfield.iokit.Loader.days_old() and ~skyfield.iokit.Loader.download() make it simple to download a fresh copy of a file if the copy on disk is older than you would like.

1.30 — 2020 October 11

• The various strftime() Skyfield methods now support the %j day-of-year format code.
• Fix: the new Julian calendar support broke support for out-of-range month numbers, wrapping them into the current year instead of letting them overflow into subsequent years. #461
• Fix: a stray debugging print() statement was stranded in t.dut1. #455
• The ~skyfield.timelib.Time object, if manually instantiated without a Julian date fraction, now provides a fraction array with dimensions that match the Julian date argument. #458

1.29 — 2020 September 25

• Fix: the new Julian calendar feature was raising an exception in the calendar methods like ~skyfield.timelib.Time.tt_calendar() if the time object was in fact an array of times. #450
• Fix: trying to iterate over a time object would raise an exception if the time was created through ~skyfield.timelib.Timescale.ut1().

1.28 — 2020 September 24

• Broken URL: Because the VizieR archive apparently decided to uncompress their copy of the hip_main.dat.gz Hipparcos catalog file, the old URL now returns a 404 error. As an emergency fix, this version of Skyfield switches to their uncompressed hip_main.dat. Hopefully they don’t compress it again and break the new URL! A more permanent solution is discussed at: #454
• To unblock this release, removed a few deprecated pre-1.0 experiments from April 2015 in skyfield.hipparcos and skyfield.named_stars that broke because the Hipparcos catalog is no longer compressed; hopefully no one was using them.
• In a sweeping internal change, the ~skyfield.timelib.Timescale and ~skyfield.timelib.Time objects now offer support for the Julian calendar that’s used by historians for dates preceding the adoption of the Gregorian calendar in 1582. See choice of calendars if you want to turn on Julian dates in your application. #450

1.27 — 2020 September 15

• The printed appearance of both vectors and of vector functions like Earth locations and Earth satellites have been rewritten to be more informative and consistent.
• Added ~skyfield.timelib.compute_calendar_date() which lets the caller choose the Julian calendar for ancient dates instead of always using the proleptic Gregorian calendar. This should be particularly useful for historians.
• Added ~skyfield.timelib.Timescale.J() that builds a time array from an array of floating point years. #436
• Added four new strftime methods for the non-UTC timescales [(#443).](skyfielders/python-skyfield#443) All four of them support %f for microseconds, and provide a reasonable default format string for callers who don’t wish to concoct their own:
  • ~skyfield.timelib.Time.tai_strftime()
  • ~skyfield.timelib.Time.tt_strftime()
  • ~skyfield.timelib.Time.tdb_strftime()
  • ~skyfield.timelib.Time.ut1_strftime()
• Thanks to several fixes, comets and asteroids with parabolic and hyperbolic orbits should now raise fewer errors.
• The prototype ~skyfield.magnitudelib.planetary_magnitude() can now return magnitudes for Uranus without raising an exception. The routine does not yet take into account whether the observer is facing the equator or poles of Uranus, so the magnitude predicted for the planet will only be accurate to within about 0.1 magnitudes.

1.26 — 2020 August 1

• The official ∆T files on NASA’s FTP server have stopped receiving updates — they have no new data beyond February, the start of the global pandemic. Unless they are updated by next February, older versions of Skyfield will unfortunately download the files all over again every time ~skyfield.iokit.Loader.timescale() is called (unless the builtin=True parameter is provided). To make Skyfield less fragile going forward:
  1. The loader’s ~skyfield.iokit.Loader.timescale() method now defaults to builtin=True, telling it to use the ∆T and leap second files that ship with Skyfield internally. To download new ∆T files from NASA and the leap second file from the International Earth Rotation Service, specify builtin=False.
  2. The concept of an “expired” file has been removed from load(). Skyfield is now much simpler: if a file with the correct name exists, Skyfield uses it. See downloading-timescale-files if you still want your application to check the age of your timescale files and automatically download new ones.
• The ICRF.separation_from() method now officially supports the combination of an array of positions with a single reference position! Its previous support for that combination was, alas, accidental, and was broken with the 1.23 release. #414 #424
• A prototype ~skyfield.magnitudelib.planetary_magnitude() routine has been added with support for several planets. #210

Commits

• 36e3b7b Bump version to 1.31
• 1b9f867 Fix a test data file path for CI
• 7a25202 Final tweaks and CHANGELOG for 1.31
• 6b5728c For #463, properly handle duplicate comets in file
• d43b64d For #463, avoid platform-specific %-m strftime
• 21f10b5 Measure whether ∆T should use both TT floats
• 0cca705 Add new 2016 long-term ∆T parabola
• e5026db Let Time.ut1_fraction also reify Time.delta_t
• c3d3c10 More experimentation with delta_t approaches
• de97e8f Add timing from old delta_t tables for comparison
• Additional commits viewable in compare view

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[coveralls]

Coverage remained the same at 78.42% when pulling c03cd1c on dependabot/pip/master/skyfield-1.31 into 41d529f on master.