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Antoine Couette wrote:
> Your "reworked" results are 
> probably the most accurate ones achievable given the Ephemeris sources 
> you are using. The only remaining significant improvement would be 
> taking in account the Limb irregular shape (see F.E.R.'s comments just 
> hereafter).

I can make one small improvement. The Astronomical Almanac eclipse
predictions have adjustments of +.5" in the Moon's longitude and -.25"
in latitude to correct for the difference between its center of mass and 
center of figure. My program has an option to apply that adjustment, but 
I normally disable it to make the output compatible with other programs. 
With the option enabled, the occultation is 1.7 seconds earlier. In 
Paris astronomical time, the results are:

10:53:17.3  Arago
10:52:59.3  Hirose (no corrections)
10:52:57.6  Hirose (with corrections)


> You are right, "les hauteurs varies" mean "Unrefracted altitudes", i.e. 
> as they would be observed from Earth Center and without any Atmosphere 
> (no refraction).

However, I thought "les hauteurs vraies" were the *topocentric*
unrefracted altitudes of the centers. With that assumption I got:
1901-05-22T22:20:33.83 UT1
1901-05-22T22:20:32.93 Terrestrial Time
-0.907 seconds delta T
+47°49'33.2" - 79°37'22.8" north lat, east lon

The new, correct solution is:
1901-05-22T22:20:13.81 UT1
1901-05-22T22:20:12.91 Terrestrial Time
-0.907 seconds delta T
+48°23'09.9" - 79°28'22.2" north lat, east lon

So Paris astronomical time = 10:29:35 by my computation. Arago's value
is 12 seconds later: 10:29:47. His estimated position is N48°23'
W079°25', only a little different from my second computation.
Unfortunately, the wrong time in my previous message spoiled your
chronometer rate computation. So I'll do it again.

March 2 occultation:
   6:57:28  M (hack watch)
  10:53:17  Tmp (my value)
---------
  -3:55:49  M-Tmp (hack watch error)

   1:17:58  A-M (Arago's value)
  -3:55:49  M-Tmp (from above)
---------
  -2:37:51  A-Tmp (chron. error)


May 22 lunar distance:
   6:34:42  M (hack watch)
  10:29:35  Tmp (my value)
---------
  -3:54:53  M-Tmp (hack watch error)

   1:17:14  A-M (Arago's value)
  -3:54:53  M-Tmp (from above)
---------
  -2:37:39  A-Tmp (chron. error)


clock rates:

  -3:55:49  M-Tmp (May 22)
  -3:54:53  M-Tmp (March 2)
---------
      -:56
Hack watch lost .69 s/day.

  -2:37:39  A-Tmp (May 22)
  -2:37:51  A-Tmp (March 2)
---------
      +:12
Chronometer gained .14 s/day.


> And a last comment: while earlier running this example on my own, I was 
> a bit surprised at the "inaccuracy" of Arago's results, mainly due to 
> his Lunar coordinates surprisingly and significantly inaccurate by 
> to-day standards.

It's interesting that the JPL ephemerides use no observations before the
20th century (I think the oldest are from 1911).

-- 

   

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