20-21 MAY 2012 UT

35° 03' 07.42" N,  Longitude: 110° 41' 53.05" W
Southern limit "Graze Zone" Near Winslow, Arizona


The annular solar eclipse of 20-21 May 2012 UT (ASE 2012) was visible (clouds permitting) from parts of southeast China (including Macau and Hong Kong soon after sunrise May 21 local time), Taiwan (Taipei near southern limit), Japan (Kagoshima, Osaka, and Tokyo on centerline), across the north Pacific, and the southwest United States (May 20 local time).

From sunrise (China) to sunset (Texas) with maximum eclipse in the northern Pacific.

In the SW USA, the centerline of the path of annularity (blue line below) made landfall over northern California, then traversed Nevada, southern Utah, northern Arizona, the southwest corner of Colorado, New Mexico, and (at sunset) western Texas. 

The ASE2012 path of annularity in the United States

This, for me, was quite fortuitous.  Normally, "I don't do annulars", and with totals more often than not find the need to trek to the most distant parts of the globe to locate in the Moon's shadow.  But, here was an annular, visible right from my home state (Arizona) that, by chance, was also at that time of year, in the most favorable location (in the NE part of Arizona) by far with a dearth of cloudy weather (see below).  Indeed, the drive to the small town of Winslow, Arizona (of  "Standin' on the Corner" fame) - bifurcated by the southern limit of the path - was only 5-1/2 hours from my house in Tucson.  ROAD TRIP!


In the SW USA, the expectations for lack of cloud cover are most favorable for northern Arizona, and in particular for the region in and around Winslow - a town which is itself located on the southern limit of the path of annularity.  See below monthly average cloud cover statistics across the path of annularity for May as compiled by Jay Anderson.  See Jay's web site for more information. 

May monthly cloud cover percentage  along the path of annularity - compiled by Jay Anderson.  Note a local minimum at Winslow Municipal Airport @ 5% (!)


Eclipse observers traveling into the path of annularity will usually elect to position themselves either (a) on "centerline" (blue line on maps above), (b) just inside the annular path limits (orange lines on maps above), or (c) some locations in between of particular geographical interest.  From centerline (a), the Moon traverses centrally across the annularity larger solar disk, leaving a concentric annulus of photospheric light surrounding the moon at mid-eclipse.  From (b), just inside (~ 1-2 km) the northern or southern limits, the moon's silhouette in front to the Sun at mid-eclipse has one limb of the Moon internally tangent to the solar limb at mid-eclipse.  From there an extreme "solar crescent" forms - with the jagged edge of the moon (from its mountains and valleys seen in silhouette) - and  causes a continually changing pattern beads of sunlight near the point of tangency for up to ~ 2 minutes centered on mid-eclipse. (E.g., click and HERE and  HERE to see videos of of near-limit Baily's beads from the May 10, 1994 annular solar eclipse).

(a) Mid-eclipse on Centerline
(near Page, AZ)
(b) Mid-eclipse 2 km inside southern limit
(near Winslow, Arizona)
Limb profile detail at C2 near Winslow, Arizona
(solar North up in this display)
Above graphics generated with Xavier Jubier's "Solar Eclipse Maestro" S/W for MacOS X

Click HERE to see an animation of the progression of the Moon across the Sun for +/- 5 minutes centered on mid-eclipse as will be seen from just north of Winslow, Arizona (as discussed below).

For ASE 2012 the plan is to observe from just inside southern limit to see extended Balily's bead phenomenena with a prolonged C2-to-C3 internaly-tangent transit of the Moon's limb -- not from a centerline location.

For TSE2012, a group of about a dozen of us decided to opt for opportunity (b) to observe the dynamic event of a lunar limb "graze" along the edge of the solar photosphere with a curvi-linear dance of beaded sunlight around the lunar limb from contact 2 to contact 3.

TAKE IT EASY (click):

Given then the statistically best likelihood for clear skies and the serendipitous (for me) proximity to Tucson, the "plan" (modulo near-term weather forecast modification) was to observe ASE 2012 from just north of Winslow, Arizona, 2 km (+/- 0.5 km) north ("inside") of Southern limit.   From Winslow, eclipse first contact (partial ingress phase) began at 5:27 PM MST on the evening of Sunday, May 20, 2012.  Mid-annularity is at 6:36 PM MST, and the sun set at 7:23 PM in 25% partial eclipse.

The annotated (north "up") satellite photo below shows the town of Winslow, Arizona.  The southern limit of the path of annularity (red line) runs parallel to Interstate-40 and bifurcates the town.  Those south of the line saw a VERY deep partial eclipse, but not a complete annulus.  The red "X" marks our eclipse-observation spot, ~ 2 km north of that limit. From that location the lunar limb profile causes continual "beading" effects when the Moon's limb is at and nearly tangent to the Sun's for about a minute.

Winslow, southern limit, and observing location ("X" marks the spot).  North is up.
Click HERE for a larger, higher-resolution photo.

This observing site was ideal from both an eclipse viewing and logistical standpoint.  Being just beyond the northern periphery of the town the site was fairly isolated on an infrequently used, but very good condition, road - just off the main interstate (see map below with north to the right)  and also provided nearly unobscured views to the astronomical horizon.  Additionally, the location was VERY close to lodging (just a couple of minutes drive to the ECONOLODGE where we stayed the night prior) and ample places to fill our stomachs (no need for take-along peanut butter sandwiches).

Close-up view of the observing area and local infrastructure.  North is to the right.
Click HERE for a larger, high-resolution photo.

Click HERE for the original pre-eclipse logistics planning page.


Latitude: 35° 03' 07.42" N (+35.05206°),
Longitude: 110° 41' 53.05" W (-110.69807°)
Obscuration at Maximum Eclipse: 87.10%
Magnitude at Maximum Eclipse: 0.93326
Mean-Limb Annular Duration: 44.5 s

ECLIPSE EVENT  MST       Altitude Azimuth  PA    VA  
Contact I:     17:27:11  +21.8°    280.0°   274°  4.8°
Contact II:    18:36:19   +8.2°    289.0°   353°  2.0°
Max-Eclipse:   18:36:41   +8.1°    289.1°     2°  1.8°
Contact III:   18:47:02   +8.0°    289.1°    12°  1.5°
Sunset:        19:24:03   +0.0°    295.0°    N/A  N/A
Contact IV:    Not Visible Below Horizon


During the time +/- a few minutes inclusive centered on "mid-eclipse", in anticipation of, and during, the lunar-edge graze, my eyes were glued to the eyepiece of a 6-inch catadioptic telescope with a full aperture solar filter.  This was something I needed to see with my own eyes!  But, the event, of course, was dutifully recorded with time-resolved imaging.  The image sequence below shows the passage of the lunar limb grazing the edge of the solar photosphere in time increments of 1 second, from left to right, starting at 18:36:16 MST.  The fine structure changing over time due to selenographic features along the lunar limb.  Images were acquired by Joel Moskowitz with a Takahashi Sky 90 (90 mm diameter refracting telescope) with a Baader full-aperture solar filter, and an AP 2X  Barlow lens to increase the image scale at the focal plane with a  Sony NEX-VG20 camera at the image plane.  The raw frames were post-processed by Glenn Schneider into the image sequence below.  Post-processing included: time-constrained image selection, video de-interlacing, unsharp (2 pixel Gaussian kernel) masking, contrast/brightness re-normalization with additional non-linear dynamic range re-stretch across all images before multi-image compositing.  The image sequence captures the morphology of the light profile at the limb, but not the remarkable dynamic favor of it as experienced visually.

ASE2012 Lunar Limb Graze with 1 sec time resolution.  Click on the image or HERE to see at 2x scale and spatial resolution.


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