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Incorrect Double Star Positions (Answer: The Washington Double Star Catalog Has Errors)

Hi. A couple nights ago I was using Sky Safari to star hop to NGC4490 in Canes Venatici. Your chart showed a bright star near by, WDS 12290+4144 mag 8.6 (see screenshot below). However, when I pointed my finder scope to that location, the star wasn't there. I think you have the incorrect information for this star. You list 12h 29m 41.45s by 41 37 47.8. WDS database lists 12 29 02.9000 +41 43 49.700. I believe that the star you have plotted is actually GJ 3729, a 13.8 mag star.


I ran into a similar issue the same night observing Nu Scorpii although I don't remember which star it was. Both events were quite unusual as Sky Safari has never let me down before. I just thought I would let you know in case some the position info for some of the stars in your database got mixed up.

 

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5 comments

  • 1
    Avatar
    Bill Tschumy

    We don't enter all the data manually, so there is little chance of an error on our part.  This star appears in the Washington Double Star catalog and the AB pair has listed magnitudes of 8.69 & 9.30 at those coordinates.  If there is an error, it is in the WDS.  We don't try to correct errors in the published catalogs.

    When you are comparing coordinates from different sources, you have to make sure you are using the same precessional epoch and also make sure both are using proper motion (or not proper motion) the same way.

  • 0
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    Choppstar

    Hi Bill,

    Thank you for your response.  I guess I will just chalk it up to bad catalog entries then.  I've used Sky Safari to star hop to several hundred objects and couldn't remember encountering this before so it seemed odd that I would notice two nonexistent stars while hopping to maybe 10 objects in a couple nights.  I assumed that you did not manually enter millions of objects but that doesn't mean that a developer couldn't write a bad update statement to a database.

    Thanks again, Brian

  • 0
    Avatar
    Bill Tschumy

    As I mentioned, I did check the raw WDS data and that double star is listed with those magnitudes.  It is not an error importing the catalog.

    You would be surprised how many errors we find in the "professional" catalogs we use in SkySafari.  Data like this is just inherently messy. 

  • 0
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    Choppstar

    Hi, I can't imagine how messy it is to manage all of the data that is coming in these days.  Thanks a lot.  I've used Sky Safari for years and love it.

    Brian

  • 0
    Avatar
    Growflavor

    One power of a community is to discover such errors....

    Having a thread like this one where all observed errors get reported with catalog ID would make it easier to cut & paste entries into a public observing list or database...

    so we could easily toggle such errors into view while planning an observing session...for example, I added a bunch of these user databases back to my SkyData folder for SNpp8 since I find being able to toggle such lists to be very useful:

    https://support.simulationcurriculum.com/hc/en-us/articles/231534407

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