Graphing Declination vs Time for the Moon - oddness!

[Simon Banton]

For reasons I won't go into, I'm still using Stellarium 0.22.2 on OS X 10.13.

I'm attempting to identify the Major Lunar Standstill around 3000 BCE, and am graphing the Moon's declination vs time (and also Phase Angle versus time) in the Astronomical Calculations tool.

Attached screenshot illustrates.

When I hover over the declination curve at its maximum value, an infobox appears for the data point showing the date/time and the declination as expected.

However, the X axis of the graph corresponding to this position indicates an entirely different date.

What's more, when I click above this max declination point on the green line to set the main window to the same date/time (which it does, as expected), then the main window's information for the Moon shows an entirely different value for the declination compared to that in the data point infobox.

I am very confused by this - clearly there's some offset between where the graph thinks I clicked and where the infobox thinks I've pointed my mouse.

Is this a known problem with 0.22.2, in which case I'll have to abandon using it for this purpose or something that I'm misinterpreting as to the way to operate this tool?

Appreciate any insights.

Cheers

Simon

Annotated screenshot:

[Georg Zotti]

Dear Simon,

the graphs unfortunately are bound to using Gregorian calendar dates. This will lead to errors you will certainly know. I have so far not used the tool for prehistoric studies, but I am afraid any solution may be far from trivial. Sorry for the inconvenience. You can use the Calendars plugin and show Julian and Gregorian dates for easier manipulation. The main window always uses Julian before 1582-10-15, just not some 3rd-party modules.

[Alexandros Kosiaris]

Hi Georg,

While not the OP, I have a follow up question

>  main window always uses Julian before 1582-10-15

Does this apply before 45-01-01 too; 

Thanks,

Στις Σάβ 14 Σεπ 2024, 15:44 ο χρήστης Georg Zotti <georg...@univie.ac.at> έγραψε:

Dear Simon,

the graphs unfortunately are bound to using Gregorian calendar dates. This will lead to errors you will certainly know. I have so far not used the tool for prehistoric studies, but I am afraid any solution may be far from trivial. Sorry for the inconvenience. You can use the Calendars plugin and show Julian and Gregorian dates for easier manipulation. The,  just not some 3rd-party modules.

novac...@googlemail.com schrieb am Samstag, 14. September 2024 um 14:29:25 UTC+2:

For reasons I won't go into, I'm still using Stellarium 0.22.2 on OS X 10.13.

I'm attempting to identify the Major Lunar Standstill around 3000 BCE, and am graphing the Moon's declination vs time (and also Phase Angle versus time) in the Astronomical Calculations tool.

Attached screenshot illustrates.

When I hover over the declination curve at its maximum value, an infobox appears for the data point showing the date/time and the declination as expected.

However, the X axis of the graph corresponding to this position indicates an entirely different date.

What's more, when I click above this max declination point on the green line to set the main window to the same date/time (which it does, as expected), then the main window's information for the Moon shows an entirely different value for the declination compared to that in the data point infobox.

I am very confused by this - clearly there's some offset between where the graph thinks I clicked and where the infobox thinks I've pointed my mouse.

Is this a known problem with 0.22.2, in which case I'll have to abandon using it for this purpose or something that I'm misinterpreting as to the way to operate this tool?

Appreciate any insights.

Cheers

Simon

Annotated screenshot:

--
You received this message because you are subscribed to the Google Groups "Stellarium" group.
To unsubscribe from this group and stop receiving emails from it, send an email to stellarium+...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/stellarium/a55a92be-af65-412e-b763-b5a855476115n%40googlegroups.com.

[Simon Banton]

Ah - OK, so noted.

I shall resort to using "Next Rising of Selected Object" + Archaeolines + a 50% transparent DTM horizon of the Stonehenge landscape and have a happy afternoon watching the Moon bounce backwards and forwards between its extremes and spotting where it gets as close as possible to maximum northerly rising :-)

Regards

Simon

[Georg Zotti]

Any number lower than 1582 is lower than 1582, be it 45 or -44. (Presumably you want to ask whether we use Julian Calendar before Julius Caesar.) Yes. Using this date to separate Julian from Gregorian is common for probably all relevant astronomy programs, or at least those based on Meeus's books. Appendix F in the User Guide is essential reading for anyone who wants to use Stellarium for historical simulation. Note that the pontifices after Julius managed to misapply his 4-year leap rule every 3 years until Augustus fixed that again, making dates before 8AD "unhistoric" if you want.

[Georg Zotti]

I am afraid yes. However, when the AstroCalc graphic shows something in mid-3rd millennium, you are just a month or so off. When the graph provides a Gregorian date, use the Calendar plugin to display Greg and Jul dates, and just move date until the Greg date computed earlier shows up. This provides Jul date and hopefully the computed phenomenon. I hope this works, I have no current application or reference data for it.

[Alexandros Kosiaris]

Cool, thanks for the answer and the extra info! 

To view this discussion on the web visit https://groups.google.com/d/msgid/stellarium/5b779473-8f49-4e4f-b559-f32b2b02d7e0n%40googlegroups.com.