py View on Github def reverse_terra ( xyz_au, gast, iterations= 3 ): """Convert a geocentric (x,y,z) at time `t` to latitude and longitude. timescale() t = ts. （matplotlibでアニメーションを描く方法は今回の範囲を超えてしまうので省略しますが、興味のある方は FunctionAnimation などで調べてみてください）。. \nIts results should agree\nwith the positions generated by the United States Naval Observatory\nand their Astronomical Almanac\nto within 0. framelib module provides a number of standard reference frames, whose use is described in Coordinates in other reference frames. Is there a way to move the Python-loop over the coordinates into NumPy? The Skyfield docs say that Skyfield uses NumPy, but as far as I can tell wgs84. 2; WOW64) AppleWebKit/537. load. output velocity. bsp') earth = eph['earth'] # vector from solar system barycenter to geocenter sun = eph['sun'] # vector from solar system barycenter to sun geocentric_sun = sun - earth # vector from geocenter to sun ts = load. If there’s a particular kind of object you’re interested in, you might want to read its documentation first, then return here when you’re ready Astrometric positions are usually generated in Skyfield by calling the Barycentric method observe(), which performs the light-time correction. It depends on various data files to accurately compute moon phases, planet positions, etc. positionlib import ICRF. parser from calendar import monthrange ts = api. As with the equatorial system, the angles associated with horizontal coordinates are so popular that Skyfield provides a built-in method altaz() to retrieve them, while ( x,y,z) coordinates require a call to frame_xyz() with the geographic location itself passed as the reference frame: x = -1. bsp') earth = planets['earth'] moon = planets['moon'] position = (moon - earth). bsp') # יצירת מילון לאחסון תוצאות #Creating a dictionary to store results results_dict = {} # לולאה על כל שנה מ-1 עד 2999 # Loop over each year from 1 to 2999 for year Jun 19, 2021 · However, this does not meet your stated desire, since it knows nothing of skyfield, astropy, or any other module outside the basic Python distribution, because that's the way my employer wanted it. In Skyfield, a topocentric location object like topos is also a reference frame oriented to the location’s horizon and zenith. altaz() with the position of the ground station defined as: ground_station_position = wgs84. Is there a way to return a vector, which contains all position? Oct 24, 2016 · I have solved it by add some code. Instant dev environments. Kepler Orbits. I've created a simple python method to do this, an Aug 20, 2020 · The Python program attached to this note in file Appendix_C_example. position and . degrees. py. mpc print( "Skyfield:", skyfield. Progman. Jun 20, 2020 · 初の天文ネタ。興味が分散しすぎだけど、それが自分。。 環境を構築する 先日から少し調査していたのだが、天文に使えそうなPythonモジュールがあった。とりあえず、この2つが良さそう。知らんけど。。 ・Skyfield ・Astropy この2つの違いは全く分かっていないが、これらが使えるような環境を Feb 21, 2023 · python; scipy-optimize; skyfield; Share. Take a look at Stellarium's cultural sky database for different ways to draw the constellation lines. moon, earth = eph['moon'], eph['earth'] e = earth. ecliptic_latlon() return x. Topos` whose ``longitude`` and ``latitude`` are those of the point on the Earth's surface directly beneath this position (according to the center of the earth), and whose ``elevation`` is the height of this position above the Earth's center. Unlike the fixed reference frames J2000 and the ICRS, this ‘TETE’ frame rotates slowly as the Earth’s precession and nutation shift the equinox point. But be warned that it has some rough edges! The Skyfield astronomy library should be preferred over PyEphem for new projects. Package Health Score 76 / 100. It accomplishes many of the same tasks using the official US Space Force libraries for coordinate conversion, precession & nutation modeling, time Aug 18, 2022 · The _observe_from_bcrs() routine exists because star positions are computed very differently from positions of objects in the Solar System; and _at() lets the loop that does light-travel-time computation for Solar System objects be more efficient, since otherwise Skyfield would have to build a whole Position object each time through the light Apr 20, 2016 · from skyfield. 165, 30) #latitude, longitude We would like to show you a description here but the site won’t allow us. next_transit (at least, I can't find them), which is what I used with pyephem. try: print (url) #original try: connection = urlopen(url) except: import urllib2 user_agent ='"Mozilla/5. Unlike the :class:`~skyfield. More than 100 million people use GitHub to discover, fork, and contribute to over 420 million projects. We would like to show you a description here but the site won’t allow us. utc(2018, 9, 13, 4) What if I j May 21, 2023 · Apologies for what I think will turn out to be a silly question. Creation of 4 Nautical Almanac pages (that span 6 days data) takes 11. toposlib. py", line 328, in ts = init_sf(spad) # in alma_skyfield File "C:\Python37\lib\site-packages\sfalmanac\lib\alma_skyfield. """An Earth satellite loaded from a TLE file and propagated with SGP4. radians. +54deg 29' 04. find_discrete() function, which accounts for 80. txt was written in an attempt to reproduce both the TEME and J2000 state vectors. apparent(). Learn how to install Skyfield, a Python package for performing astronomical calculations, with pip or by hand. Codespaces. bsp' ) Jan 19, 2016 · Am I using the ephemeris file in the wrong way (wrong barycenter ?) or is this just a limitation of the de421. 1' ### This is the function I am aiming to implement. e. epoch moment for these satellite orbit parameters. It works great and now I'm trying to implement Earth=>comet distance (e. I would recommend you choose something that is used widely and well maintained, and not just any random code on the internet. to provide the two data lines from a TLE file as separate strings. output position. total = closest_approach < umbra_radius - moon_radius. positionlib import Geocentric eph = load('de421. The problem has been solved. sgp4lib. Beware that the internal routines supporting Kepler orbits are rudimentary and subject to change — only the interface documented here is guaranteed Aug 21, 2023 · To fix the problem with the path in Windows follow the steps given next. g. Dec 21, 2020 · Using Python-Skyfield to calculate the upcoming conjunction if Jupiter and Saturn. The code with the files for DE421 as it is in the documentation works, but when I use the files for D You signed in with another tab or window. 0. api as sf import numpy as np import pand I'm trying to run skyfield (installed via current pip package and from the repo) on Azure notebooks using Python 3. A coordinate or frame in the Altitude-Azimuth system (Horizontal coordinates) with respect to the WGS84 ellipsoid. api import load ts = load. Altitude is also known as elevation angle, so this frame is also in the Azimuth We read every piece of feedback, and take your input very seriously. Any suggestion of how to perform this simple calculation of Earth-Jupiter distance with Skyfield ? Thanks ! Attempts to import skyfield or skyfield. utcnow() mtime = now + datetime. 図の描き Jun 26, 2023 · Here is the solution I have: from skyfield. . ecliptic_latlon() return angle. Luckily @AllenKummer's answer explains why and gives a revised script. radec() print(ra) print(dec) Which outputs: 02h 43m 28. api import load or >> from skyfield import load for instance return "ImportError: No module named skyfield. Oct 27, 2013 · Use Astral (current version 1. Topos(latitude_degrees=latitude, longitude_degrees=longitude) x, y, z = sat. Jul 11, 2017 · sat = skyfield. AltAz(*args, **kwargs)[source] #. timescale() incurs the following error: ----- skyfielders / python-skyfield / design / satellite_passes. Note that these example scripts are written for fairly recent versions of matplotlib . ¶. GitHub. Using Ecliptic Longitude: Dec 21,2020 18:37:31 UTC - Wikipedia; Dec 21,2020 18:20:40 UTC - My Calculation. latlon(37. ProxyHandler({}) opener = urllib2. Apr 3, 2019 · from skyfield. api import wgs84, load. utc(2021, 5, 19, 12, 26) sun_subpoint = wgs84 Mar 20, 2016 · UPDATE: Skyfield has just had a significant revision, including expanded documentation and a method for angular separation - see the accepted answer. 0 (Windows NT 6. latlon(50, 50, elevation_m=50) However, I'm not sure how to build the position for the moving object. Azimuth is oriented East of North (i. You can rate examples to help us improve the quality of examples. timescale () t = ts. assembling these together with the new epoch to produce a new (SGP4 derived) state vector at that time. Nov 3, 2020 · I'd like to determine if a (lunar) eclipse occurred in a given day (ie past 24 hours) Considering the python snippet. 得られた座標をそのままPythonの matplotlib を使って3次元のアニメーションプロットにしてみます。. By using the skyfield library, we can obtain extremely accurate predictions of the sun’s position in the sky, and in contrast to many other libraries, we can use the same method to predict the position of other celestial bodies. MIT. Dec 21,2020 13:34:33 UTC - My Calculation. api " / "ImportError: No module named skyfield " respectively. 94s. This is reproduced in the following script: import skyfield. Aug 27, 2017 · You just have to create a little function that takes a number and returns a number, by converting the number to a Skyfield time and then the angle back to a plain number: t = ts. It can convert between dozens of different units, wrap numeric vectors in its own array and table data types, translate between a number of timescales and coordinate frames, run image processing algorithms on astronomical images Instead of instantiating this class directly, Skyfield users usually give a reference geoid the longitude and latitude they are interested in: from skyfield. Depending on the archive you're requesting, some files might be very Using Skyfield with AstroPy¶. I believe the differences here are caused by the different timescales that are being used by SkyField vs NASA. To associate your repository with the skyfield topic, visit your repo's landing page and select "manage topics. I've spent a bit of time trying to find the answer, but cannot seem to resolve by myself: I'm trying to determine the position of an Jun 19, 2022 · In this example, we’ll show how to generate a sun path diagram for any given day for a preselected location. 2125. If this time is an array, then a list of datetimes is returned instead of a single value. Jul 26, 2019 · MEGA note: My answer is totally wrong and should be unaccepted by any means necessary. Step 1: Open the folder where you installed Python by opening the command prompt and typing where python. api. The Geoid, like WGS84 or IERS2010, that Automate any workflow. Improve this question. vec = ICRF([3141, 2718, 5820]) ra, dec, distance = vec. I searched the term Yallop in GitHub and found and in combination of I put this together: import matplotlib. Write better code with AI. GitHub Copilot. I am assuming one is able to determine if an eclipse occurred within 24hrs of a time t by. Both the . This section of the documentation will gradually accumulate example scripts for producing images from Skyfield computations. Skyfield computes positions for the stars, planets, and satellites in orbit around the Earth. These are the top rated real world Python examples of skyfield. If you graph the . api import wgs84 topos = wgs84. timedelta(minutes=min_range) sat = 'ASTROCAST 0. timescale() ephem = api. 122 Safari/537. I wanted to make a quick ground-track plot, so I used the Python package Skyfield to propagate a TLE and return Earth-Centered Inertial coordinates. Reload to refresh your session. Find out the limitations, precautions, and methods of loading and indexing satellite elements. Popular skyfield Nov 4, 2016 · I'm using skyfield to compute the relative distance of planets to Earth as a function of time (as described on the skyfield home page). Bases: BaseCoordinateFrame. It On running the test below: #!/usr/bin/env python3 import datetime, io, skyfield. Full package analysis. " GitHub is where people build software. Host and manage packages. utc(2018, 4, 22) planets = load('de421. If you try running them on a system with an older version of the library, you might see errors If you want to override Skyfield’s default notation to create either the string above, or any other notation, then give hstr() or dstr() a format= string of your own. A sort of 'The american ephemeridis' books Skyfield is a Python library for astronomical computations. Thanks to this method, a Time can often be used directly as a coordinate for a plot. You switched accounts on another tab or window. If not, then I'd recommend you release your Python version as a separate package. Trying to load timescale data: from skyfield. You can find SGP4 routines in many languages in many places. skyfield. utc_datetime ¶ Convert to a Python datetime in UTC. __version__ Feb 5, 2022 · elevation, azimuth, distance = (moving_object_position - ground_station_position). """An interface between Skyfield and the Python ``sgp4`` library. Skyfield is a pure-Python astronomy package that is compatible with both Python 2 and 3 and makes it easy to generate high precision research-grade positions for planets and Earth satellites. replace(tzinfo=utc)) mins = np. api import load planets = load ( 'de421. This even avoids having to import NumPy manually, because the ICRF class auto-detects if it has been passed a Python list and automatically converts it into a NumPy array for Welcome to the Skyfield Repository. Feb 28, 2021 · It seems right in principle though I'm a bit wary as I'm new to Skyfield: propagate a TLE to the new time. km. For that, I have to calculate the sgp4 repeatedly, adding 1 second each time. skyfielders / python-skyfield / skyfield / earthlib. Example Plots. Its modern design encourages better Python code, and uses NumPy to accelerate its calculations. Skyfield now offers basic support for computing the position of a comet or minor planet whose elliptical, parabolic, or hyperbolic orbit is provided as Kepler orbital elements. Skyfielders who wanted to use it would simply pip install your other package and tell Skyfield to use that as its precession algorithm. 67P/ Tchouri). The first example in the documentation shows the calculation of sunrise and sunset for a given location. at(ts. It uses NumPy as its only dependency and can be installed with pip. So, Thank you. position. build_opener Jan 20, 2022 · I think there is an open issue somewhere involving this. I didn't find a method within the package, so I've "invented" a way by calculating the dot product between the Is there a way to calculate heliocentric planetary coordinates (longitude and latitude) with Brandon Rhodes' python program, Skyfield? If I only do: mercury(utc=(1980, 1, 1)). units import Distance. If there did turn out to be problems with permission to publish, you would simply take down the new package and destroy all Jun 12, 2019 · I'm using skyfield to try to map out where the ISS is as a function of time starting with a given TLE. 913 au north. utc Elegant astronomy for Python. datetime. timescale() Its methods are: Timescale. A script will typically start by building a single Skyfield Timescale to use for all date and time conversions: from skyfield import api ts = api. py 'function download() 335 line. load_file('de421. If there's no way to avoid the Python-loop, is there perhaps a way to treat some accuracy for speed? Nov 18, 2021 · I want to find planet position using skyfield in the form of Ecliptic longitude,latitude, speed and distance in geocentric Nov 11, 2023 · To run its unit tests, install Python 2, Python 3, and the tox testing tool. Security. at(t). utc(time)). Python 3. Example Plots ¶. It should use the syntax of Python’s str. It is unacceptable from a huge gov base company like JPL. Several issues are raised by these data files: If they're not found in the path of the Loader, they're downloaded at runtime. Iḿ really happy to have bumped into skyfield because as an amatorial programmer I found skyfield more intuitive than other python module. bsp') sun = ephem["Sun"] earth = ephem["Earth"] # Compute sunrise & sunset for random location near Munich location = api. velocity are ( x,y,z) vectors oriented along the axes of the ICRF, the modern replacement for the J2000 reference frame. In the iokit. previous_rising, . 6429) Once a geographic position has been created, here are its attributes and methods: model ¶. Then I created a Topos() object fixed to the Earth's surface at lat/lon = 0, 0 and used it to generate the rotation of the earth in order to "unwind" the ISS position on the surface. api import Topos, load ts = load. Feb 3, 2019 · However, skyfield doesn't have the functions . latlon( 51. Welcome to the Skyfield Repository. Looking at the position vector, I get agreement to within a couple of centimeters . Its results should agree with the positions generated by the United States Naval Observatory and their Astronomical Almanac to within 0. The data I have is a Cartesian position in meters computed from . positionlib import ITRF_to_GCRS, Geocentric. 3% time processing this function . Sep 13, 2019 · Skyfield is leveraging the models represented as numerical integrations by the JPL Development ephemeris while ELP is a more analytical approach. This seems rather a kludge if the capability Sep 23, 2023 · from skyfield. It seems that SkyField uses the proleptic Gregorian calendar for dates in the past. """. I will make position generation slower, because instead of a simple vector operation, Skyfield will have to build a True/False mask over each array of dates to determine which dates need to be computed using the first array and which need to use the second array. 0005 arcseconds (which equals half a “mas” or milliarcsecond). 36 (KHTML, like Gecko) Chrome/38. Skyfield stores the locations of celestial bodies as ( x,y,z) vectors that it calls positions. The TEME state vector agrees with the result cited in the paper. , N=0, E=90 degrees). The skyfield Almanach documentation uses this code to define the points in time between which to compute sunrise & sunset: t0 = ts. arange(1, min_range+5) trange = ts. 7k 6 6 gold badges 39 39 silver badges 53 53 bronze partial = closest_approach < umbra_radius + moon_radius. load. Jan 31, 2021 · はじめに 気象ネタが一段落したので、気象以外のことに注力する時間ができてきた。そろそろ天文計算ネタを再開する。 Skyfieldを使いながら、天文計算の基本である天球座標系について学んでみた。 Skyfieldで惑星の位置を計算する 今回は、Skyfieldのトップページにあるプログラムを修正して We would like to show you a description here but the site won’t allow us. at(t) x, y, _ = e. Mar 22, 2023 · Hi, I try to run the code from the skyfield documentation (Observing a Moon location) but with the tf, tpc and bpc files for the DE440. Sep 13, 2018 · Skyfield currently finds every one of the 3,642 lunar eclipses listed for the years AD 1000–2500 in NASA’s Five Millennium Canon of Lunar Eclipses by Espenak and Meeus. Apr 23, 2023 · Skyfield is a Python library for astronomical computations. I'm calculating the apparent angular separation between two objects using Skyfield. bsp' ) earth, mars = planets [ 'earth' ], planets [ 'mars' ] Learn how to use Skyfield to predict the positions of Earth satellites from TLE files. I need the position vector for 1 day time interval with 1 second periodicity. Skyfield computes positions for the stars, planets,\nand satellites in orbit around the Earth. Nov 28, 2022 · Skyfield does not include any constellation lines, since there is no international standard for how to draw them. format() method. At the moment I'm trying to create a script that can create sideral and sinodic table including moon phases etc. bsp' ) earth, mars = planets [ 'earth' ], planets [ 'mars' ] When using the find_events() function in EarthSatellite, it seems a rise may be reported as culmination if the visibility is very short. Hyde Park, London observer = earth + wgs84. The AstroPy Project is a sprawling community effort to bring together a complete toolkit for working astronomers and astrophysicists. coordinates. from_datetime (datetime) Return a Time for a Python datetime. tt(2023, 6, 1, 21, 30) # June 1st 2023 9:30pm # the location of the observer i. km But I am not sure exactly how your code will look, since I don't see anywhere in your code the distance-to-Earth that you spoke of, and your code references a sa variable that isn't otherwise used (maybe you meant sat Mar 8, 2023 · Skyfield doesn't care about the details of how, once you get out into the world, you establish geo-located stations and then measure your position relative to them; so, happily, Skyfield doesn't need to make any adjustments as you choose an implementation and measure your observation station's location. py", line 98, in init_sf Nov 7, 2022 · Skyfield has a find_minima() routine that might help you. The easiest to access SGP4 that I know is in the Python package Skyfield. 51, -0. Packages. pyplot as plt import math import numpy from skyfield. api import wgs84, load from math import degrees, cos, asin, floor ts = load. Contribute to skyfielders/python-skyfield development by creating an account on GitHub. Topos extracted from open source projects. For example, here’s the exact string you would use to format an angle in degrees, arcminutes, and arcseconds using Jun 19, 2022 · from skyfield import api from skyfield import almanac from datetime import datetime from datetime import timedelta import dateutil. km_per_s. api from inside python fail. The most basic data that I'm looking for is the true anomaly as a function of time. You signed out in another tab or window. api import load, wgs84 import numpy as np from skyfield. at(t) elements = osculating Python Topos - 31 examples found. bsp file ? I read the description of the ephemeris file on the Skyfield website but not sure I fully understood it. This is almost certainly a newbie python programmer issue but any guidance would be appreciated. A simpler example with custom latitude and longitude would be: PyEphem will continue to receive critical bugfixes and be ported to each new version of Python. Find and fix vulnerabilities. Jun 13, 2022 · skyfielders / python-skyfield Public. true_equator_and_equinox_of_date object>¶ The dynamical frame of Earth’s true equator and true equinox of date. Step 2: Once you have opened the Python folder, browse and open the Scripts folder and copy its location. But some slight disagreements are inevitable, because Skyfield uses a modern ephemeris for Earth and Moon positions, while the Supplement used the old VSOP87 theory. next_setting or . 35 seconds (on my PC, in Windows 10) of which 9. There are several kinds of celestial object for which Skyfield can produce a position. Mar 12, 2019 · Returns a :class:`~skyfield. — which are currently computed only at the height of the eclipse to classify it, would need to be supplied as functions of time so that folks could ask the almanac routines when the eclipse stepped from one state to the next. Find out the latest version, changelog, citation, and troubleshooting tips. py View on Github """ On my laptop, this script shows that simply computing the positions and the sunlit-ness of the ISS for each of the 381 seconds of this pass takes roughly the same amount of time as mounting a full search for the moment it passes into shadow. Wikipedia Great conjunction times (1800 to 2100) Using Right Ascension: Dec 21,2020 13:22:00 UTC - Wikipedia. utc ( 2022, 4, 30, 20, 27, 41) # timestamp of the map above planets = load ( 'de405. bsp') sun, earth, moon = eph['sun'], eph['earth'], eph['moon'] time = ts. ecliptic_latlon() I get a Barycentric object, and therefore the latitude and longitude don't match heliocentric values. 7". skyfield does have the function find_discrete, which will search between given times to find when a function changes, so I wrote the following to test: sgp4lib. api import wgs84, load from skyfield import almanac from datetime import datetime, timedelta, date #Ephemeris eph = load('de441. data. vectors. api, skyfield. data import mpc from I've implemented sgp4 algorithm using Skyfield in python. api import Topos, load, utc import datetime import numpy as np min_range = 15 now = datetime. TEME` frame, this frame doesn’t ignore nutation. latlon doesn't take a NumPy array as input. observe(moon). 36"' #cxh headers = { 'User-Agent' : user_agent } proxy = urllib2. rst-class:: motto\n\n *Elegant Astronomy for Python*\n\n \n. Oct 12, 2021 · This code works, but is too slow for my needs. 0005 arcseconds (half a “mas” or Sep 16, 2022 · Three thoughts: You might be interested in tweaking your script to use the pure sgp4 library that Skyfield uses, so that you can rule out whether Skyfield makes any difference here—your script would then be talking to the official SGP4 engine itself from Vallado et al. In the end I realize it's a nit-pick, I just wanted to better understand the tools I'm using. Latest version published 4 months ago. The tests runing in Python 2 will exercise the fallback pure-Python version of the routines, while Python 3 exercises the fast new C++ accelerated code: cd python-sgp4 tox Legacy API For example, here is how to find the osculating elements of the moon orbiting earth: from skyfield. import datetime import math import pytz import pandas as pd from skyfield import api from skyfield. api import load from skyfield. 6 upgraded the Standard Library datetime type so that the contortions of pytz are no longer necessary, and instead recommends dateutil for working with timezones. May 27, 2021 · from skyfield. Timescale. Nov 27, 2021 · Download and install python module "sfalmanac" Run command "python -m sfalmanac" Got the following error: File "C:\Python37\lib\site-packages\sfalmanac_main_. However, NASA used the Julian Calendar for dates before 1582, so for example, the eclipse on 0150-12-06 (Julian) falls on 0150-12-05 in Gregorian. Jun 23, 2021 · In switching from Ephem to Skyfield, creation of these pages was typically four times slower. derive orbital elements from the pos-vel. from skyfield. 11 seconds are spent in the almanac. utc(mtime. 3414, -121. true_equator_and_equinox_of_date = <skyfield. timescale() eph = load('de421. Follow edited Feb 23, 2023 at 21:19. Several issues are raised by these data files: Oct 18, 2022 · I was trying to see whether I can jump between ECEF and LLA and although I was able to; I feel like my solution is not very clean: I use the following script to do the conversion LLA --> ECEF --> LLA: from skyfield. def get_elevation_angle(pos): pass ts = load. elementslib import osculating_elements_of ts = load. 6). constants, skyfield. Feb 7, 2024 · Skyfield is a pure-Python module that generates high precision positions for planets and Earth satellites. The skyfield. So if you pass it to the frame_latlon_and_rates() method, Skyfield will compute the rates at which the altitude and azimuth are changing as the target moves across the sky: Every version of Python that Skyfield supports will work with the pytz package described in this section. separation_from() angle between the two satellite positions, how often do minima occur? If they were, say, every 90 minutes, you could probably set find_minima() searching by providing it with data points maybe 30 minutes or 20 minutes apart—which would let you avoid, say, having to compute each satelllite's position class astropy. built in ``Timescale`` object. Returns a tuple of latitude, longitude, and elevation whose units are radians and meters. This was posted at about 7 AM local time and must have been pre-coffee; the period shown here is only 40 minutes, seeing that it's wrong would have been a no-brainer, which is indeed the state I'm often in, pre-coffee. May 23, 2023 · You can mention in Skyfield documentation which people should rely on the data provided in NAIF System, not JPL Horizon itself. This method makes Skyfield Time objects compatible with Python datetime objects, which also provide a toordinal() method. My problem is with the state vector in J2000. skyfield Elegant astronomy for Python. This frame is used for measuring right ascension and declination. framelib. utc(2018, 9, 12, 4) t1 = ts. tt(jd=jd) angle, lon, distance = earth. 18. Positions. now () Return the current date and time as a Time object. jp iw fk ad uf ok tf ee le wt