2016 ANNULAR SOLAR ECLIPSE EXPEDITION IN TANZANIA RESULTS

by Paul D. Maley, NASA Johnson Space Center Astronomical Society

Eclipse path through Africa. Courtesy X. Jubier.

Eclipse circumstances at our site. Courtesy X. Jubier.

Figure 1.  Baobob tree at sunset in Ruaha National Park. P. Maley photo. Photos without credits are those made by the author.

Figure 2. Our center line group on September 1, 2016 at Iayai village, Tanzania. Left (second row) Lynn Palmer, Front left Elaine Williams, Second row from right John Addison, Byron Braswell, Paul Lobert, Bob Hammarberg, Chris Faser, Debbie Lobert, Dee Holisky. Front row right Paul Maley.  Others in the photo who are not identified are  people who live in the house and neighbors.

The 45th Ring of Fire Expeditions solar eclipse expedition concluded with a successful viewing of the annular eclipse of the Sun from Tanzania on September 1, 2016.  There were two sites set up, one at the north edge and one near the centerline.  Although clear skies had prevailed every day prior to eclipse day, the morning dawned with overcast skies. It took several hours to travel from our base at Mufindi Highland Lodge first to the north edge site where two observers were dropped off along with a Masai guard. Then the rest of the group continued on a 3 hour drive to Wanging’ombe (means: a lot of cows) where I had planned to position ourselves as a center line site.  But cloud moved close to the town and after some period of agonizing I decided to move the team westward about 15 miles or so to the village of Iyai where we found a house beside the main road.  Permission was obtained to observe from behind the house and in spite of winds creating blowing dust we were able to get the group behind the main building where wind was blocked.  In the image above, the tree on the right produced some beautiful solar crescent images during the partial phases while the tin roof behind generated equally interesting crescent projections.

Figure 3. Main group site at Iyai courtesy of X. Jubier.

Figure 4. Overall layout showing our base at Mufindi, the north edge site and center line site.

THE ECLIPSE

Figure  5. Central annularity. P. Maley photo with 360mm Takahashi FS60C, Nikon

Figure 5A. Partial phase 1. Bob Hammarberg photo. 

Figure 5B. Partial phase 2. Bob Hammarberg photo. 

Figure 5C. Annularity. Bob Hammarberg photo. 

Figure  6. Baily’s Beads composite at 3rd contact recorded in a burst of images over about 2 seconds. P.Maley photo sequence using Takahashi FS60C.

Figure 7. Some of the best solar crescents I have seen were projected through the tin roof onto the concrete floor (and the wall) of the house at our center line site.

Figure 8. Dozens of solar crescents projected through tree leaves. Lynn Palmer photo.

Figure  9. Roger Venable (right) transports some gear including a boxed lunch from the range rover into the bush at the north edge site. Note chairs we brought with us strapped to the top of the vehicle. Each car carried 7 passengers and a driver. Although it was clear at the edge site when we dropped them off, it clouded over at the critical central eclipse time. Both vehicles had to carry the remaining team members to the center line site.

Figure  10. One of the sturdy concrete cattle pens in which we first deployed at Waging’ombe. This pen was assigned to Chris Faser with Dee Holisky and John Addison checking the partial phase progression. Note the bright shadows on the ground indicating clear sky overhead; but extensive cloud in the background moving from the east eventually forced me to move everyone farther west.

Figure  11. Cows, goats and locals keep an eye on us during the partial phases at Wanging’ombe. 

Figure  12. Local woman views through eclipse glasses at the Iyai site. 

Figure  13. A series of Eumetsat images showing the shadow of the Moon moving left to right over Africa. Central eclipse was at 08:53:33 GMT where we were.  Second contact at Iyai occurred at 08:52:01, altitude 69 azimuth 36.5; third contact at 08:55:06, altitude 69.5 azimuth 34.8.  Annularity should have lasted 3 minutes 5 seconds.  Even though the Sun was 97.6% blocked, a noticeable lunar shadow was cast onto the Earth as seen in the above images.

NORTH EDGE EXPERIMENT FOR THE INTERNATIONAL OCCULTATION TIMING ASSOCIATION (IOTA)

The purpose of this activity conducted by Roger Venable was to develop a technique by which one can measure precisely where the edge of the Sun is — that is, a technique to measure the diameter of the Sun.  Timings of Bailey’s beads during solar eclipses are assumed to yield a measure of the solar diameter that is more precise than diameter measurements that scientists have obtained by other means.  This is part of a long term program that has been undertaken at various eclipses by IOTA in different forms.

As many eclipse-watchers have noticed, the edge of the Sun briefly shines between the mountains of the Moon during an eclipse. The Sun’s edge seen in this way appears as a brilliant series of disconnected lines and points, called Bailey’s beads. Immediately before they disappear or immediately after they reappear during an eclipse, Bailey’s beads are tiny, star-like points of light. They appear bright, but they are so small that the telescope cannot resolve their sizes — they are point-like. Their spectrum can be observed by placing a diffraction grating into the light path of the telescope, so as to split the light into it colors.  The opaque layer of the Sun that we think of as its “surface” is called the photosphere. Its spectrum has dark absorption lines, called Fraunhofer lines, at certain energy levels of light. We see these energy levels of light as colors. The absorption at certain colors is caused by a layer of gas overlying the photosphere that is called the chromosphere. This is the lower layer of the Sun’s atmosphere. The chromosphere absorbs light from the photosphere because it is cooler than the photosphere. So, if a Bailey’s bead consists of light that is mostly from the photosphere, the dark Fraunhofer lines, created by the overlying chromosphere, will be visible in the spectrum.  However, the chromosphere radiates the light it absorbs from the photosphere, and radiates much of it at wavelengths that are the same as those at which it absorbed it. Therefore, with the photosphere blocked from view by the Moon, a spectrum of the chromosphere shows bright lines of color, not dark lines. If a Bailey’s bead consists of light that is mostly from the chromosphere, its spectrum will consist of bright lines at the same colors in which the dark lines of the photosphere would be located.

As a disappearing bead fades, the source of most of its light changes from the photosphere to the chromosphere; and as a reappearing bead brightens, the source of most of its light changes from the chromosphere to the photosphere. The transition point between chromosphere and photosphere is the edge of the Sun, and it is the transition point between absorption lines and emission lines. To find the location of the edge of the Sun, the transition point is timed in a video of the spectra of Bailey’s beads.  Each frame of the video has a precise time stamp on it, placed there by electronics that obtain time from a GPS device, accurate to a microsecond. Since the shape of the mountains at the edge of the Moon have been accurately measured by the Lunar Reconnaissance Orbiter, comparison of the timings of the beads with the known shapes of the mountains yields a precise location of the edge of the Sun.  The technique is still under development.

Figure  14. Roger Venable’s setup for the eclipse. There are two telescopes, with solar filters, on a mounting that automatically tracks the Sun, and the video cameras feed their signal into the two laptop computers in the cabinet. (The cabinet is needed because the ambient light is too bright to allow clear views of the video screens.) The video system puts a very accurate timestamp on each video frame. One telescope recorded beads, while the other recorded spectra of the beads. Roger Venable photo. 

Figure 15.  A 30 frame stack of images combined by Roger Venable to show Baily’s Beads at his northern limit edge station. Second contact here should have occurred at 8:54:02; third contact at 8:54:54 UT with annularity lasting about 52 seconds.  Roger Venable photo.

Figure 16.  Byron Braswell, Chris Faser, and Paul Lobert in action at the centerline. During annularity the landscape was noticeably dimmer.  Lynn Palmer photo.

Figure 17. Paul Maley photographing annularity.  The 69 degree elevation made it difficult without having to elevate the tripod and sit on a chair.  Lynn Palmer photo.

SIGHTSEEING

 

Figure  18. Map of our one way air route from Dar to Selous to Ruaha on Coastal Air

Figure  19. After landing at Selous airport we saw a giraffe attempting to cross the runway.

Figure 20.  It is not uncommon to see a goat hitching a ride on a truck. This one was captured after the eclipse on the road to Makambako.

Figure  21. Question: of the 5 road marking photos abive, which ones authorize you to pass? Answer: all of them as our drivers demonstrated time and again.

Figure 22. Our amazing view to the east at Ruaha River Lodge where animals constantly came to drink.

Figure  23. A happy Hyrax at Ruaha.

Figure   24. There are 18 mongoose pictured here in a group of about 30 that ran by our cabin at Ruaha one morning. They have spitting cobras here and the mongoose is the natural enemy.

Figure 25.  Charging elephant.

Figure  26. A saddle-billed stork at the river.  Byron Braswell photo.

Figure  27. Pair of lionesses in Ruaha. Byron Braswell photo. 

Figure 28.  Milky Way time exposure. Byron Braswell photo using 24mm lens at f/1.4 from Ruaha.  The reddish color appears due to the camera sensor and the fast lens used.

Figure  29. Compare with above. Photo by Chris Faser using a different camera and 24mm lens at a much slower f/4 from Ruaha.

Figure  30. Zebra gathering

Figure  31. Lilac breasted roller. Roger Venable photo.

Figure 32. Two impalas locking horns. Byron Braswell phoo.

Figure  33. Four giraffes in Ruaha.

Figure 34.  Hippo with mouth open at Ruaha. Lynn Palmer photo.

Figure  35. Leopard in Ruaha. Lynn Palmer photo.

Figure 36. The Moon 2 days ahead of the eclipse as seen before sunrise. Note reflection of the Moon in the river at Ruaha.

Figure  37. Splendid Starling.

Figure 38. Lunch at Ruaha.

Figure  39. Our cabin interior at Ruaha.

Figure 40.  Group of hippos in the Ruaha river after leaving the lodge.

Figure  41. Night viewing at Ruaha. Note Masai guard second from left.

Figure  42. Traffic jam representative of our 14.5 hour trip from Mufindi back to the Dar Es Salaam airport on September 3. We made our flight with 10 minutes to spare!

Figure  43. Our group at Mufindi Highland Lodge complete with all members and drivers. First row left to right: Lynn Palmer, Onesmo, Raymond, John Addison; second row left to right: Paul Maley, Olivia Harvey-Williams, Chris Faser, Elaine Williams, Roger Venable, Debbie Lobert, Paul Lobert, Jeff Pohlman, Byron Braswell, Dee Holisky, Bob Hammarberg.

One of the more innocuous astro phenomena is the Zodiacal light. This is a faint glow from sunlight illuminating interplanetary dust particles that occurs either after sunset or before sunrise depending on the time of year and hemisphere.  We were lucky enough at Ruaha and again at the higher altitude of Mufindi to spot the light after sunset. Visually the slightly tilted cone of light extended to 70 degrees altitude although it could have been even higher. In general the photos shot did not correspond to the visual appearance exactly.

Figure  44. Iridium flare photographed in Sagittarius at Ruaha. Magnitude -8 by C. Faser.

Figure 45. Zodiacal light after sunset at Ruaha, altitude 5027 ft /1562m. Byron Braswell photo with a 24mm f/1.4 lens.  The light is indistinct but does parallel the ecliptic and is tilted slightly to the left in the above image. With the eye we could easily see a cone extending upwards of 70 degrees from the western horizon after sunset. 

Figure  46. Zodiacal light photo by Chris Faser at Ruaha with 24mm lens at a slower f-stop of f/4.  Here the light is slightly more distinct and tilted along the ecliptic. The conical nature of the Zodiacal light is outlined by the two arrows.

ANIMAL VIEWING EXTENSION TRIP

Figure 47.  The crossing point with wildebeeste and zebras making the journey. Paul Lobert photo.

Figure  48. The vast herd. Paul Lobert photo. 

Figure 49. Crocodile closing in on wildebeeste.  Jeff Pohlman photo.

Figure 50.  Crocodile lunch!  Paul Lobert photo.

Figure 51. The smiling lion. Jeff Pohlman photo.

Figure 52. Cape Buffalo. Bob Hammarberg photo.

Figure 53. Fish eagle catch. Bob Hammarberg photo.

Figure 54. Mom and baby rhinoceros.  Bob Hammarberg photo.

Figure 55. Silver backed jackal. Bob Hammarberg photo.

Figure 56. Spotted hyena family. Bob Hammarberg photo.

 Figure 57. Warthog.  Bob Hammarberg photo.

Figure 58. Young leopard. Bob Hammarberg photo.