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Hi
I have just downloaded version 0.9.9.386R. Everything seems to work perfectly.
When implemented, graphical Terminal 6 will be great.
Regards
Hi,
the graphical representation on a map of the Totality Path of a Solar Eclipse is one of the most complex problems of Spherical Astronomy. I started writing the code from scratch, studying the classical work of Chauvenet (hard to understand because based on “19th century human computing”, with legacy formulas) and the Explanatory Supplement of the A.E. 1961, the only one freely published so far. Comets have priority though, also because we could have a nice surprise before the end of the year.
regards
Alberto
Hi
Just released today : it is possible now to compute solar eclipses between -4000 to 2100 on the IMCCE web page :
https://ssp.imcce.fr/forms/solar-eclipses
https://ssp.imcce.fr/forms/solar-eclipses/doc
Interesting to check Uruk_One ?
Regards
Hi,
What a bit confusing is that ancient eclipses are reported with Gregorian Date instead of Julian Date. For example the TSE occurred on 1223 BCE Mar 05, is reported as happened on -1222 Feb 22. The year is correct because it’s the Astronomical Year, but Month and Day are referred to a Gregorian Date, rarely used in this case.
This eclipse was almost certainly visibile from Ugarit for several reasons but the IMCCE prediction places the totality path further north of Ugarit, like old NASA maps based on a simple parabolic function for deltaT do.
Hi
I agree : IMCCE uses the gregorian proleptic calendar. This is confusing because if you don’t read the documentation, you might think there is a date error.
The ephemeris used for computing solar eclipses is INPOP19a, their most recent ephemeris. Regarding delta t : the value computed by IMCCE for the year -1222 is UT1 − TT = -29562.533 s / 3600 = 8.211 h. The value is not far from the value given on the Nautical Almanac web site https://astro.ukho.gov.uk/nao/lvm/. Do you think the path computed by IMCCE could be the right one ? To be continued…
All the best.
Hi
I am rather surprised by the use of the ephemeris INPOP19a so far into the past. Because the guaranteed precision, like the previous INPOP17a ephemerides, is about -1000 and +1000 years from the present date. Even the versions that IMCCE offers for download are within this range.
Regards.
Hi
This is absolutely correct : it is possible to download INPOP19a files only for 1000 years before and after J2000. As IMCCE does not usually provide inaccurate results, they have probably extended their ephemeris for a much longer period. Unfortunately IMCCE will publish a new book about astronomical calculations but not until September 2021. Maybe there is more information regarding the values of delta T, the computation of lunar and solar eclipses.
If I have the opportunity to attend a lecture by a member of IMCCE, I will ask him about these issues.
Regards.
Hi
I didn’t know that and thank you very much for clarifying. Anyway, I tried entering the time of maximum eclipse for that position and delta T into Uruk_One. It came up with a difference in times of about 6m 48s, which seems quite a lot to me.
Regards
Hi
I check the time and location of maximum eclipse according to various sources :
Xavier Jubier : http://xjubier.free.fr/site_pages/solar_eclipses/5MCSE/xSE_Five_Millennium_Canon.html
Total Eclipse, Maximum Eclipse = 10:38:00 UT, Date = 5 Mar -1222, Maximum Eclipse Lat = 27,2N, Lng = 13,5E, Duration = 03m56s, Alt. Sun = 50°, Azi. Sun = 162°, Mag. 1,04441, ∆T = 29457,5 s
IMCCE :
Total Eclipse, Maximum Eclipse = 10:34:39 UT, Date = 5 Mar -1222 (22 Feb -1222), Maximum Eclipse Lat = 27,17N, Lng = 14,37E, Duration = 03m56s, Alt. Sun = -°, Azi. Sun = -°, Mag. 1.04574, ∆T = -29562.533 s
Emapwin : DE431
Total Eclipse, Maximum Eclipse = 10:35:15 UT, Date = 5 Mar -1222, Maximum Eclipse Lat = 27,18N, Lng = 14,21E, Duration = 03m56s, Alt. Sun = -°, Azi. Sun = -°, Mag. 1.0444, ∆T = -29588 s
Regards
Hi
Thanks and for comparison.
IMCCE : INPOP19a
Total Eclipse, Maximum Eclipse = 10:34:39 UT, Date = 5 Mar -1222 (22 Feb -1222), Maximum Eclipse Lat = 27.17N, Lng = 14.37E, Duration = 03m56s, Alt. Sun = -°, Az. Sun = -°, Mag. 1.04574, ∆T = +29562.533 s
Uruk_One: DE441
Total Eclipse, Maximum Eclipse = 10:41:27 UTC, Date = 5 Mar -1222 (22 Feb -1222), Maximum Eclipse Lat = 27.17N, Lng = 14.37E, Duration = -s, Alt. Sun = 51.39°, Az. Sun = 164.96°, (sd1/sd2) = 1.045148, Magnitude = 1.007815, Distance (Sun-Moon) = 28.198″, ∆T = +29562.533 s
Cartes du Ciel: DE441
Total Eclipse, Maximum Eclipse = 10:41:27 UT, Date = 5 Mar -1222 (22 Feb -1222), Maximum Eclipse Lat = 27.17N, Lng = 14.37E, Duration = -s, Alt. Sun = 51.386°, Az. Sun = 164.957°, Distance (Sun-Moon) = 28.2″, ∆T = +29562.533 sec.
Note that in all three cases I chose Delta T the same.
Regards
Translated with http://www.DeepL.com/Translator (free version)
If you switch Uruk1’s DeltaT computation for the date you are examining to NASA you will obtain 29457.5 seconds, that is the value computed using a simplified parabolic function not keeping in account non-tidal effects in variation of DeltaT. But a clay tablet named KTU 1.78 was discovered in Ugarit, an ancient Phoenician city. Most likely is referred to a total solar eclipse occurred there few years before Peoples of the Sea (Shardana) destroyed the city. The attribution is confirmed by a reference to Mars (Rsp), visible nearby the eclipsed Sun.
If we assume this eclipse total in Ugarit, the admitted values for DeltaT at the date are:
30650 to 31470 for Totality. (DE431)
30900 to 31700 for Totality. (DE441)
so a value of 29457s is unacceptable, the parabolic function (that still the sources you mentioned are using) does not compute a reliable value.
Again I want to remember to you all that comparisons between ephemerides must be done in TT. UT can be sometimes an opinion, TT surely not. 🙂
regards
Hi
About the Ugarit event, I agree with you of course, Mars could only be seen during the TSE. That’s why the Delta T value must be greater than 31000s. I was just puzzled by the difference of almost 7 minutes between INPOP19a and DE441 at the same Delta T value.
Regards.
This is a case where the use of DE441 shows the difference of Lunar Orbit (LE441) with respect to older ephemerides. As an example Espenak reports for the -1222 Mar 05 a Greatest Eclipse at 18:48:26.0 TDT, using the JPL DE431. Uruk1, using the same ephemeris, few versions ago, computed the GE at 18:48.4 TDT, basically the same value.
Now, with DE441, Uruk1 finds for GE 18:51:39 TDT, a remarkable difference due entirely to the ephemeris, in this case ΔT is not involved (that’s why I always recommend to use TDT).
Hi
So, unless I’m mistaken, according to IMCCE, UT1 − TT = -29562.533 s. = 08:12:24, Maximum eclipse : 10:34:39 UT, TT = 10:34:39 + 08:12:24 = 10.5775 + 8.2066 = 18:47:03
Regards
;
That’s correct.
It’s just that the ephemerides have a problem with the moon. The further into the past or the future, the more they diverge from each other.
Regards.
I would put it another way. Why do JPL or IMCCE publish a new long term ephemeris every, say, 7-8 years? Basically because they make available better models, not just for fun. Of course the difference in the calculation of the position of a body becomes more noticeable as we move away from the current era, and the most recent ephemeris is supposed to give the best results as possible. If you compute a solar eclipse occurred on 2000 BCE with VSOP87, VSOP2000, DE406, DE431, DE441 or INPOPxx you surely obtain different results, but being the DE441 the most recent one we should regard its results as the best possible, that’s it.