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skyfielders / python-skyfield

Elegant astronomy for Python
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Problem finding the VizieR archives #301

Closed aendie closed 4 years ago

aendie commented 4 years ago

I performed a clean install of the latest version of Python 3. Then I placed a new Python 2 program that requires Skyfield in a new folder to prepare for manual migration to Python 3. I first hit this error:

Error1

It couldn't find the file hip_main.dat.gz. Then I tried going there manually:

Error2

I found the web site http://cdsarc.u-strasbg.fr/ftp/cats/ with the archives:

Screen3a

The Hipparcos data file is located here: http://cdsarc.u-strasbg.fr/ftp/cats/I/239/:

Screen4a

I'm not sure if their FTP site has simply gone down or if it's been moved to another server. I placed the file manually in the new folder.

(The good news is - my program works now with Python 3.)

aendie commented 4 years ago

What I forgot to mention is that the first error message above obviously came from the following section of code (when hip_main.dat.gz is missing in the current folder):

from skyfield.api import Star, load
from skyfield.data import hipparcos

with load.open(hipparcos.URL) as f:
    df = hipparcos.load_dataframe(f)
brandon-rhodes commented 4 years ago

I can confirm that I also show the FTP server as unreachable, but that the alternative HTTP URL you have found does work. I'll go release a new Skyfield right now with the fix!

brandon-rhodes commented 4 years ago

I have just released Skyfield 1.15. Thank you very much letting me know so quickly that the URL stopped working! Hopefully folks can upgrade and get moving again if this has stopped their work.

aendie commented 4 years ago

Much obliged! Thanks for your prompt fix.

Now, since there's no tab in github (that I know of) to share my success with Skyfield, please permit me to post here the charts I have created. They are IMHO a better version of the four charts you find here: https://en.wikipedia.org/wiki/List_of_selected_stars_for_navigation

A4chart0-180.pdf A4chart180-360.pdf A4chartNorth.pdf A4chartSouth.pdf

I use Python to create LaTeX with the tikz package for graphics (the tikz manual is only 1247 pages long LOL) and MiKTeX converts it to PDF (on a Windows 10 platform).

Without Skyfield this would have been nigh on impossible... as I include stars down to mag 5. And, what's more, I really like them... e.g. with the Galactic Plane. I have posted some "corrections" to Wikipedia in the past - maybe I'll try and find a polite way to get these in too ;-)

brandon-rhodes commented 4 years ago

Thank you for sharing these diagrams — it is always encouraging to see the projects that become possible when open source tools are put together to produce a result! I'm happy that Skyfield wound up being a useful part of your toolchain, and I like how your star charts came out. I hope that they enjoy wide distribution and see lots of use by folks locating those stars in the sky.