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AAVSO / VStar

VStar is a visualisation and analysis tool for variable star data brought to you by AAVSO
https://www.aavso.org/vstar
GNU Affero General Public License v3.0
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Epoch from VSX always shown as JD in phase plot dialog epoch field #89

Open dbenn opened 3 years ago

dbenn commented 3 years ago

When an epoch is available from VSX it's always shown as JD in the phase plot dialog epoch field and in the star info dialog. Actually, in the latter case it doesn't say whether it's JD or HJD etc at all. Does the web service provide us with this info?

Fulvio pointed this out in the May 2019 VStar CHOICE course: https://www.aavso.org/comment/64671#comment-64671

mpyat2 commented 3 years ago

Sebastian Otero wrote on Mar 21, 2021: Hi Maksym,

Sorry for bothering you with a probably silly question: Can we assume that the VSX epoch is ALWAYS Heliocentric JD?

No. That's what we aim for and what we request for all submissions but most epochs that we inherited from the GCVS when VSX was first populated were given as JD. With time revisions were made and HJD was always the standard dates used but it is impossible to know what is JD and what HJD at this point. Most objects will have HJD dates.

I ask about this because there was a question in one of the VStar CHOICE courses about it and there is the >>corresponding VStar development issue. If it is so (the epoch is always HJD), some changes to VStar could be made to make it clear (especially for the novice).

No..., it is likely going to be HJD but we can't be sure. If the epochs are relatively new (e.g. after 2006 or 2007), they are more likely to be HJD. '-------------------------------------------------------------------------------------------------------------------------

So there is no clear solution. Probably it simply could be mentioned in the documentation.