>Question 1.  If you apply the limb corrections for the topocentric
>lunar librations for the west coast of Panama for the 08 pril 2005 eclipse,
>what happens to the duration by the most conservative definition
>(i.e., last moment of internal tangency at 2nd and 3rd contact) as you would reckon it?

I calculate a duration of true (unbroken) annularity to last 1.2 seconds!

>Question 2. Back to the 03 Oct 1986 eclipse, I believe we were located VERY close to
>the predicted {very narrow} centerline - as I had computed the path with an
>attempt at doing a "proper" atmospheric refraction correction for our 44,000 ft.
>altitude above MSL.

Below are some calculations I made for Glenn Schneider's observations
of the total solar eclipse of 1986 Oct 03. I've calculated the center
line coordinates at 19:05:19 UT for an elevation of 13411.0 meters
(44,000 feet).

This calculation does not include refraction. In examining the
refraction algorithm I use, it is apparently valid only at sea-level
("ASTRONOMY WITH YOUR PERSONAL COMPUTER", DUFFETT-SMITH, P.88). If
Glenn or anyone else has a subroutine/algorithm for calculating
refraction for elevations above sea-level, I would appreciate
receiving a copy. Certainly, it would be most useful in evaluating
Glenn's 1986 observations.

In any case, Glenn's observations were at 44,000 feet with the Sun at
an altitude of 7 degrees, so refraction should be quite small.
Nevertheless it would be nice to calculate its approximate magnitude.

Here are the numbers for Glenn's position (no refraction):

------------------------------------------------------------
Hybrid Solar Eclipse - 1986 Oct 03

Delta T =    55.2 s
Elev.   = 13411.0 m
k=0.2722810

Maximum Eclipse = 19:05:19 UT

Center Line (no refraction):

lat=  59°34'29"'N   long=  039°24'54"W     duration= 00m01.5s

         Universal  Sun    Sun    Sun   --Position Angles--
Contact    Time     Alt  Azimuth   HA     P      V      Q
         h  m  s     °      °      h      °      °      °
   1    17:59:15.4  14.0  235.3   3.54  301.4  276.6   24.8
   2    19:05:18.2   6.6  250.3   4.64  117.5   88.7   28.7
  Max   19:05:19.0   6.6  250.3   4.64  210.4  181.6   28.7
   3    19:05:19.7   6.6  250.3   4.64  303.3  274.6   28.7
------------------------------------------------------------

When the lunar limb profile is applied, I find:
 

Contact     UT
    2   19:05:19.0
    3   19:05:18.8

Unofficially, this probably looked like a very short ~1 second total eclipse.

Quite a fascinating but BRIEF eclipse!

- Fred Espenak

=============== * EARLIER E-MAIL (EXTRACT) * ==================
 

Subject: [SE] Annular eclipses
Date:     Thu, 17 May 2001 14:07:17 -0500
From:    FRED ESPENAK <u32fe@lepvax.gsfc.nasa.gov>
 

>The first such eclipse I saw was the 1984 annular from North
>Carolina, where the duration of annularity was ~ 7 seconds.
>While NOT a total, it WAS an amazing event.  ....
{...snip...}

I too saw the amazing annular eclipse of 1984 May 30 and I have some
photos posted of it at the bottom of:
http://www.mreclipse.com/SEphoto/SEgallery1.html

As you look at this mosaic of nine images taken over a period of
about 45 seconds, you will see that the eclipse was never total, nor
was it ever a complete, unbroken annular ring. At mid eclipse (middle
image), the Sun's photosphere was broken up into a series of crescent
segments and Baily's beads. Prominences, Chromosphere and inner
corona were photographed. Really quite spectacular! Now I point out
that I could not see any of this directly because the Sun was much
too bright. Nevertheless, it was quite easy to photograph.

Dennis di Cicco shot a fabulous image of this eclipse by masking the
exposed crescent with a 4.0 neutral density filter. It shows the
inner corona and a large prominence. The image was published in Sky &
Telescope in 1984 and is included in the Sky & Telescope slide set
"Glorious Eclipses." It is also reproduced in the central color
section of "Totality - Eclipses of the Sun" (Littmann, Willcox &
Espenak - http://www.mreclipse.com/Totality/Totality.html).

This is such an unusual eclipse, that it really belongs to a
different category than annular. I call it a "beaded annular" or
"broken annular" eclipse.

Unfortunately, I missed the extremely short 1986 total eclipse
described by Glenn Schneider
(http://nicmosis.as.arizona.edu:8000/ECLIPSE_WEB/ECLIPSE_86/ECLIPSE_86 .html)

So how do the 1984, 1986 and 1999 eclipses compare? Using a mean
lunar limb (k=0.2722810), I calculate the following magnitudes and
durations:

Date          Magnitude     Duration     Location
-----------   ---------     ---------    ---------
1984 May 30   0.9988        00m11.8s     Greenboro, NC (Espenak)
1986 Oct 03   1.0000-total  00m00.2s     Center Line at 19:06 UT
1999 Feb 16   0.9906        00m36.4s     Greenough, Australia(Espenak)
2005 Apr 08   0.9981        00m16.1s     Panama

  - Fred Espenak