Skyfield

------------------------

* The position classes have gained methods
:func:`~skyfield.positionlib.ICRF.frame_xyz()`,
:func:`~skyfield.positionlib.ICRF.frame_xyz_and_velocity()`,
:func:`~skyfield.positionlib.ICRF.frame_latlon()`, and
:func:`~skyfield.positionlib.ICRF.from_time_and_frame_vectors()`
that work with a new library ``skyfield.framelib``
to offer a number of familiar reference frames.
These replace the existing ad-hoc position methods
for ecliptic and galactic coordinates,
which are now deprecated (but will continue to be supported).
See :ref:`reference_frames`.
`476 <https://github.com/skyfielders/python-skyfield/issues/476>`_

* Added an official :class:`~skyfield.framelib.itrs` reference frame.

* Added support for IERS :ref:`polar-motion` 𝑥 and 𝑦.

* Added a method :meth:`~skyfield.toposlib.GeographicPosition.lst_hours_at()`
that computes Local Sidereal Time.

* A new almanac routine :func:`~skyfield.almanac.moon_phase()` returns
the Moon phase as an angle where 0° is New Moon, 90° is First Quarter,
180° is Full, and 270° is Last Quarter.
`282 <https://github.com/skyfielders/python-skyfield/issues/282>`_

* Almanac search routines that previously returned a Boolean true/false
array now return an integer 0/1 array instead, to work around a new
deprecation warning in NumPy which, for example, would have outlawed
using the Boolean array from :func:`~skyfield.almanac.moon_nodes()` to
index into the ``MOON_NODES`` list that provides a name for each node.
`486 <https://github.com/skyfielders/python-skyfield/issues/486>`_

* The undocumented columns ``magnitude_H`` and ``magnitude_G`` in the
Minor Planet Center comets dataframe have been renamed ``magnitude_g``
and ``magnitude_k`` following further research on the file format
(which does not itself document which magnitude model is intended).
`416 <https://github.com/skyfielders/python-skyfield/issues/416>`_

------------------------

* Fix: running ``load.timescale(builtin=False)`` was raising an
exception ``FileNotFoundError`` if the ``finals2000A.all`` file was
not already on disk, instead of downloading the file automatically.
`477 <https://github.com/skyfielders/python-skyfield/issues/477>`_

------------------------

* A new :func:`~skyfield.eclipselib.lunar_eclipses()` routine finds
lunar eclipses and determines their degree of totality.
`445 <https://github.com/skyfielders/python-skyfield/issues/445>`_

* The almanac module’s new :func:`~skyfield.almanac.meridian_transits()`
routine can find the moments at which a body transits the meridian and
antimeridian.
`460 <https://github.com/skyfielders/python-skyfield/issues/460>`_

* Fix: the :func:`~skyfield.searchlib.find_minima()` function was
ignoring its ``epsilon`` and ``num`` arguments and always using the
default values instead.
`475 <https://github.com/skyfielders/python-skyfield/pull/475>`_

* Fix: the ``.epoch`` attribute of Earth satellite objects that were
built using :meth:`~skyfield.sgp4lib.EarthSatellite.from_satrec()`
was, alas, a half-day off.
`466 <https://github.com/skyfielders/python-skyfield/issues/466>`_

* Fix: the ``Topos`` constructor arguments ``x`` and ``y``,
which never worked properly anyway,
have been deprecated and are now ignored.

----------------------

* 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 <https://github.com/skyfielders/python-skyfield/issues/452>`_
`464 <https://github.com/skyfielders/python-skyfield/issues/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 <https://github.com/skyfielders/python-skyfield/issues/463>`_

* Two new methods :meth:`~skyfield.iokit.Loader.days_old()` and
:meth:`~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.

----------------------

* 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 <https://github.com/skyfielders/python-skyfield/issues/461>`_

* Fix: a stray debugging ``print()`` statement was stranded in ``t.dut1``.
`455 <https://github.com/skyfielders/python-skyfield/issues/455>`_

* The :class:`~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 <https://github.com/skyfielders/python-skyfield/issues/458>`_

------------------------

* Fix: the new Julian calendar feature was raising an exception in the
calendar methods like :meth:`~skyfield.timelib.Time.tt_calendar()` if
the time object was in fact an array of times.
`450 <https://github.com/skyfielders/python-skyfield/issues/450>`_

* Fix: trying to iterate over a time object would raise an exception if
the time was created through :meth:`~skyfield.timelib.Timescale.ut1()`.