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How Does SkySafari Determine Whether An Eclipse Is Visible From A Location? (Answer: Read On!)

Sorry to bother you guys, but I was checking your Sky Safari Pro 6 about this year's solar eclipses. I clicked on the Sun>Selection>Object info and under VISIBILITY, the app lists only the annular eclipse in December under Next Solar Eclipse. I am not seeing anything for the July 2nd total solar eclipse that will occur in South America.

As for the December 26th annular eclipse, the Sky Safari app shows December 25th near midnight (which is set for me in the states...I guess). Of course this is not visible from my location, but visible in the eastern hemisphere. I thought I would mention it (for what it's worth).

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10 comments

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    Bill Tschumy

    We display eclipses as they appear at your location.  If you set your location to the spot in South America where it will be total, does it not show it in the Object Info then?

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    Larry Koehn

    Good to know, but why is it showing me the December 26th annular eclipse, since the eclipse is a eastern hemisphere event, and I am in Clarksville, Tennessee?

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    Bill Tschumy

    I believe we still show it even though it is below the horizon.  The clips *is* happening from your location even if it is not visible due to the time.  This is different from a total eclipse that does not happen at your location due to the path of totality.

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    Larry Koehn

    I like SkySafari, Bill, which is why I bring this up. In your first statement, you say "We display eclipses as they appear at your location." In your second statement - "The clips *is* happening from your location even if it is not visible due to the time." Neither eclipse is happening at my location this year. If you look at the maps below, there are no eclipses in the United States. I think people would be more interested in knowing about a total eclipse, happening this year, than being notified about an annular eclipse (see the screenshot from my iPhone below)!.

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    Bill Tschumy

    Well, that is not the way SkySafari works.  We do not show eclipses that are happening anywhere in the world.  We only show eclipses that happen from your location.

    I agree it is debatable whether we should show an eclipse that "happens" at your location but is below the horizon at the time.  However, there are lots of sticky questions of what the definition of "visible" is.  Should we show an eclipse that is 98% total right as the Sun sets.  Technically the total eclipse is not visible from your location but I bet people would like to know about it.

    I believe the charts you attached are only showing the eclipse path while above the horizon.  If the Earth were transparent you would see the eclipse from your location.  To see the location of the Sun when an eclipse happens, you can click the time icon next to the even to set the chart's time to the event time and center on the object.

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    Larry Koehn

    " We only show eclipses that happen from your location." Nothing is happening in the way of eclipses this year, for me. Very confusing in what you just wrote, Bill. "I believe the charts you attached are only showing the eclipse path while above the horizon." Of course the charts show what is happening above the horizon in regards to the shadow and Sun in THAT part of the world. What else is it showing? Why would I need to know what is going on a half a world away!

    Both eclipses from my location are below the horizon, so why is the December 26 annular eclipse listed and not the July 2nd total eclipse? This is wrong, Bill. Debatable...among who?

     

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    Bill Tschumy

    The two cases are not comparable.  The July 2nd total solar eclipse in South America doesn't happen at all from you location (the Moon is never in front of the Sun).  The December eclipse does happen but it happens while below the horizon.

    This is unlikely to change.  SkySafari  has worked this way for 10 years.

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    Larry Koehn

    Is there an astronomer at Simulation Curriculum? 10 years does not make it right! What is the owner's name and phone number?

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    Bill Tschumy

    https://simulationcurriculum.com/contact/contact.html

    I still contend that what we are doing is perfectly reasonable.

     

     

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    Larry Koehn

    I spoke to Michael, and left the matter in his hands. Thank you!

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