<p>I am searching for an year which satisfies the following criteria.</p>
<p>Dates are in <strong>Gregorian</strong> calendar.</p>
<hr />
<p><strong>Criteria</strong></p>
<ol>
<li>Year range 3800 BC to 500 BC</li>
<li>Solar Eclipse of any kind between October 14 and October 22 inclusive.</li>
<li>Lunar Eclipse of any kind between September 29 and October 9 inclusive.</li>
<li>Eclipses visible from New Delhi, India, UTC/GMT +5:30 hours.</li>
</ol>
<hr />
<p><strong>Optional Criteria</strong><br />
The gap between the two eclipses must be less than 14 days.</p>
<hr />
<p><strong>Challenge</strong></p>
<p>The challenge mainly is because the dates are in Gregorian and not Julian which the online eclipse searchers(eg: <a href="https://moonblink.info/Eclipse/search" rel="nofollow noreferrer">moonblink</a>) use. I could not find an eclipse searching tool which uses Gregorian calendar. The problem with converting Gregorian to Julian and then searching is that the date changes as the year changes and we end up with varying dates over thousands of years making it difficult to search. How to solve this?</p>
<p><strong>Feasibility</strong></p>
<p>If we solve that problem, each day of the year has approximately 20 eclipses between 3800 BC and 500 BC. So the eight days from Oct 14 to 22 would approximately have 160 eclipses. Then back to back eclipses with Lunar eclipse followed by Solar eclipse are rare, so approximately 10 to 15 eclipses will fit the back to back eclipse criteria. From which using the 'visible from New Delhi, India UTC/GMT +5:30' criteria can be used to narrow down to couple of eclipses. The optional criteria can also be used if applicable.</p>
<p>Edit: It seems I have wrongly estimated the number of eclipses fitting the criteria. The number of years satisfying the first three criteria seem to be around 120 to 140.</p>
<hr />
<p><strong>Context</strong></p>
<p>This is an independent effort to date the Mahabharata War using Archeastronomy.</p>
<p>In Mahabharata war, Bhishma is said to have left his mortal body on Winter Solistice which is Dec 21 or Dec 22 Gregorian. Which was also the first quarter of  waxing Moon of <a href="https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcSpmmU99b_mUyiDxMXu4Z9b8eOqMBKVnmL_Dw&amp;usqp=CAU" rel="nofollow noreferrer">Hindu lunar month</a> Magha. But this Winter solistice observation was observed through naked eye, so researchers like Dr. Manish Pandit have opined that it was 4 or 5 days after Solistice. So it could be from Dec 21 to Dec 27. We also know that there was a Lunar eclipse on Karthika Full Moon and a Solar eclipse on Karthika New Moon. Which is approximately 83 days and 68 days from observed winter solistice. This gives us Solar Eclipse of any kind between October 14 and October 22 and a Lunar Eclipse of any kind between September 29 and October 9. They had to be visible from New Delhi, India.</p>
<hr />
<p>Edit 1: Conversion of date range from Gregorian to Julian</p>
<p><a href="https://i.sstatic.net/75ANM.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/75ANM.png" alt="enter image description here" /></a></p>

CC BY-SA 4.0
2022-01-27T22:04:26.060Z
Moonblink says it's main source is https://eclipse.gsfc.nasa.gov/LEcat5/LEcatalog.html .  The eclipses are listed there in Gregorian date format.  Note NASA's comments on delta T (how the Earth's rotation varies), so you'll probably want to loosen you're "Visible from New Delhi" criteria.
Greg Miller
CC BY-SA 4.0
2022-01-28T01:30:07.010Z
@GregMiller thanks, but Gregorian is only used for modern dates, not for BC dates. It says 'The Gregorian calendar is used for all dates from 1582 Oct 15 onwards. Before that date, the Julian calendar is used' 1582 is AD.
Profile name
CC BY-SA 4.0
2022-01-28T01:45:14.047Z
That Gregorian / Julian convention is what Horizons uses. And the Fred Espenak eclipse catalogs "only" go back to 2000 BC. I suggest you use Julian day numbers and do your own proleptic Gregorian date conversion.
PM 2Ring
CC BY-SA 4.0
2022-01-28T02:04:00.360Z
Dealing with Delta T will be a major issue for those early dates. The uncertainty in Delta T is large in 3800 BC. https://eclipse.gsfc.nasa.gov/LEcat5/uncertainty.html says that in year -4000, the uncertainty in Delta T is 16291 seconds (>4.5 hours) and the longitude uncertainty is 67.9°.
PM 2Ring
CC BY-SA 4.0
2022-01-28T13:01:14.900Z
@PM2Ring Knowing that a given solar eclipse was visible at some specific place on earth might help to reduce the Delta T uncertainty. So, first search for plausible years with a larger geo area, then decide whether New Delhi could have been in that area when considering Delta T, resulting in a new fixed point for Delta T.
Ralf Kleberhoff
CC BY-SA 4.0
2022-01-28T13:15:49.800Z
@Ralf Sure. But I get the impression that we simply don't have records that old, which is why the uncertainty is so high. And why the Fred Espanak catalog only goes back to 2000 BC. OTOH, Horizons is happy to give Sun & Moon positions back to 9999 BC, so we can certainly search for suitable eclipses. FWIW, the delta T value that Horizons reports for BC 3800-Jan-1 (Julian) is ~99578 seconds, around 1 day, 3 hours, 40 minutes.
PM 2Ring
CC BY-SA 4.0
2022-01-28T13:17:48.473Z
@RealfKleberhoff thanks. But coverting Gregorian to Julian and then searching will take around many manual searches, which I'm trying to avoid. Is there any way we can search for Eclipses with Sun in certain ecliptic longitude?
Profile name
CC BY-SA 4.0
2022-01-28T22:11:28.870Z
@PM2Ring The Espanak/Meeus catalog were produced using VSOP87 and ELP82, JPL Horizons uses the JPL Development Ephemeris, which are much more accurate.  They cut off the catalog at those dates because those are the limits of accuracy of VSOP87.  The delta T information was computed separately and published as a separate parameter.
Greg Miller
CC BY-SA 4.0
2022-01-29T02:23:02.527Z
@Greg [I love Horizons](https://space.stackexchange.com/a/57832/38535), although I'm certainly not an expert on everything it can do, or what all its data means. I don't know how to properly calculate eclipses using Horizons, although I guess I could use trial & error and similar techniques to what I used [here](https://space.stackexchange.com/a/56140/38535). I expect JPL DE calculations for earlier eclipses to be superior to VSOP87 + ELP82 solutions. But that doesn't solve the uncertainty in Delta T issue. Maybe IERS now has better data for that...
PM 2Ring
CC BY-SA 4.0
2022-01-29T02:25:36.840Z
I found some Espenak / Meuss pages with earlier eclipses: [TEN MILLENNIUM CATALOG OF LONG SOLAR ECLIPSES](https://eclipse.gsfc.nasa.gov/SEcatmax/SEcatmax.html) & [Solar Eclipses of Saros 0 to 180](https://eclipse.gsfc.nasa.gov/SEsaros/SEsaros0-180.html). Of course, they use Julian calendar dates, but converting those dates to Gregorian is a *lot* easier than calculating eclipses. ;)
PM 2Ring
CC BY-SA 4.0
2022-01-29T02:52:53.700Z
I just checked the Horizons manual. They use the same parabolic estimate of Delta T for 9999 BC to 700 BC: DeltaT = -10 + 31.4 * T^2, where T is UT1 cent. since JD1825. And I was reminded they do have data relevant to eclipses in [Observer Table Quantities](https://ssd.jpl.nasa.gov/horizons/manual.html#obsquan), particularly 12. Angular separation/visibility, but also 13, 23, 24, & 43.
PM 2Ring
CC BY-SA 4.0
2022-01-29T06:30:08.087Z
@PM2Ring thanks for the 10 millenium catalog link, I have searched till 2000 BC, and have added it into the answer
Profile name
<data-analysis><solar-eclipse><lunar-eclipse><archaeoastronomy>
Is it possible to narrow down possible dates for the following eclipse pattern?
Profile name
# Is it possible to narrow down possible dates for the following eclipse pattern?

(Asked by: username_0 on 2022-01-27)

I am searching for an year which satisfies the following criteria.

Dates are in **Gregorian** calendar.

---

**Criteria**

1. Year range 3800 BC to 500 BC
2. Solar Eclipse of any kind between October 14 and October 22 inclusive.
3. Lunar Eclipse of any kind between September 29 and October 9 inclusive.
4. Eclipses visible from New Delhi, India, UTC/GMT +5:30 hours.

---

**Optional Criteria**  
The gap between the two eclipses must be less than 14 days.

---

**Challenge**

The challenge mainly is because the dates are in Gregorian and not Julian which the online eclipse searchers(eg: [moonblink](https://moonblink.info/Eclipse/search)) use. I could not find an eclipse searching tool which uses Gregorian calendar. The problem with converting Gregorian to Julian and then searching is that the date changes as the year changes and we end up with varying dates over thousands of years making it difficult to search. How to solve this?

**Feasibility**

If we solve that problem, each day of the year has approximately 20 eclipses between 3800 BC and 500 BC. So the eight days from Oct 14 to 22 would approximately have 160 eclipses. Then back to back eclipses with Lunar eclipse followed by Solar eclipse are rare, so approximately 10 to 15 eclipses will fit the back to back eclipse criteria. From which using the 'visible from New Delhi, India UTC/GMT +5:30' criteria can be used to narrow down to couple of eclipses. The optional criteria can also be used if applicable.

Edit: It seems I have wrongly estimated the number of eclipses fitting the criteria. The number of years satisfying the first three criteria seem to be around 120 to 140.

---

**Context**

This is an independent effort to date the Mahabharata War using Archeastronomy.

In Mahabharata war, Bhishma is said to have left his mortal body on Winter Solistice which is Dec 21 or Dec 22 Gregorian. Which was also the first quarter of waxing Moon of [Hindu lunar month](https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcSpmmU99b_mUyiDxMXu4Z9b8eOqMBKVnmL_Dw&usqp=CAU) Magha. But this Winter solistice observation was observed through naked eye, so researchers like Dr. Manish Pandit have opined that it was 4 or 5 days after Solistice. So it could be from Dec 21 to Dec 27. We also know that there was a Lunar eclipse on Karthika Full Moon and a Solar eclipse on Karthika New Moon. Which is approximately 83 days and 68 days from observed winter solistice. This gives us Solar Eclipse of any kind between October 14 and October 22 and a Lunar Eclipse of any kind between September 29 and October 9. They had to be visible from New Delhi, India.

---

Edit 1: Conversion of date range from Gregorian to Julian

[![enter image description here](https://i.sstatic.net/75ANM.png)](https://i.sstatic.net/75ANM.png)

**Tags:** data-analysis, solar-eclipse, lunar-eclipse, archaeoastronomy
> **Comments:**
> **username_1**: Moonblink says it's main source is https://eclipse.gsfc.nasa.gov/LEcat5/LEcatalog.html .  The eclipses are listed there in Gregorian date format.  Note NASA's comments on delta T (how the Earth's rotation varies), so you'll probably want to loosen you're "Visible from New Delhi" criteria.  
> **username_0**: @GregMiller thanks, but Gregorian is only used for modern dates, not for BC dates. It says 'The Gregorian calendar is used for all dates from 1582 Oct 15 onwards. Before that date, the Julian calendar is used' 1582 is AD.  
> **username_2**: That Gregorian / Julian convention is what Horizons uses. And the Fred Espenak eclipse catalogs "only" go back to 2000 BC. I suggest you use Julian day numbers and do your own proleptic Gregorian date conversion.  
> **username_2**: Dealing with Delta T will be a major issue for those early dates. The uncertainty in Delta T is large in 3800 BC. https://eclipse.gsfc.nasa.gov/LEcat5/uncertainty.html says that in year -4000, the uncertainty in Delta T is 16291 seconds (>4.5 hours) and the longitude uncertainty is 67.9°.  
> **username_3**: @PM2Ring Knowing that a given solar eclipse was visible at some specific place on earth might help to reduce the Delta T uncertainty. So, first search for plausible years with a larger geo area, then decide whether New Delhi could have been in that area when considering Delta T, resulting in a new fixed point for Delta T.  
> **username_2**: @Ralf Sure. But I get the impression that we simply don't have records that old, which is why the uncertainty is so high. And why the Fred Espanak catalog only goes back to 2000 BC. OTOH, Horizons is happy to give Sun & Moon positions back to 9999 BC, so we can certainly search for suitable eclipses. FWIW, the delta T value that Horizons reports for BC 3800-Jan-1 (Julian) is ~99578 seconds, around 1 day, 3 hours, 40 minutes.  
> **username_0**: @RealfKleberhoff thanks. But coverting Gregorian to Julian and then searching will take around many manual searches, which I'm trying to avoid. Is there any way we can search for Eclipses with Sun in certain ecliptic longitude?  
> **username_1**: @PM2Ring The Espanak/Meeus catalog were produced using VSOP87 and ELP82, JPL Horizons uses the JPL Development Ephemeris, which are much more accurate.  They cut off the catalog at those dates because those are the limits of accuracy of VSOP87.  The delta T information was computed separately and published as a separate parameter.  
> **username_2**: @Greg [I love Horizons](https://space.stackexchange.com/a/57832/38535), although I'm certainly not an expert on everything it can do, or what all its data means. I don't know how to properly calculate eclipses using Horizons, although I guess I could use trial & error and similar techniques to what I used [here](https://space.stackexchange.com/a/56140/38535). I expect JPL DE calculations for earlier eclipses to be superior to VSOP87 + ELP82 solutions. But that doesn't solve the uncertainty in Delta T issue. Maybe IERS now has better data for that...  
> **username_2**: I found some Espenak / Meuss pages with earlier eclipses: [TEN MILLENNIUM CATALOG OF LONG SOLAR ECLIPSES](https://eclipse.gsfc.nasa.gov/SEcatmax/SEcatmax.html) & [Solar Eclipses of Saros 0 to 180](https://eclipse.gsfc.nasa.gov/SEsaros/SEsaros0-180.html). Of course, they use Julian calendar dates, but converting those dates to Gregorian is a *lot* easier than calculating eclipses. ;)  
> **username_2**: I just checked the Horizons manual. They use the same parabolic estimate of Delta T for 9999 BC to 700 BC: DeltaT = -10 + 31.4 * T^2, where T is UT1 cent. since JD1825. And I was reminded they do have data relevant to eclipses in [Observer Table Quantities](https://ssd.jpl.nasa.gov/horizons/manual.html#obsquan), particularly 12. Angular separation/visibility, but also 13, 23, 24, & 43.  
> **username_0**: @PM2Ring thanks for the 10 millenium catalog link, I have searched till 2000 BC, and have added it into the answer  

---

## 0 answers

