The observation of every total solar eclipse offers it's own unique set of challenges and rewards, and the eclipse of 30 June 1992 proved to be no different. The path of totality for this eclipse traversed portions of eastern Uruguay and the Southern coast of Brazil. However, this was at, and just after, sunrise with the Sun attaining an elevation of no more than 3° before the path of totality left land and headed out over the South Atlantic Ocean. The prospects for seeing the eclipse from the limited areas of land where it was to occur were poor at best. While many total solar eclipses have been observed from ship board, the most recent in July of 1991 (Sky & Telescope, 1991), the climatological prognostication for the eclipse path at over the Ocean (at sea level), within the realm of a logistically feasible voyage, was equally pessimistic. For years, it had been obvious to a number of us that the only viable way to do this eclipse, with any degree of assured success, was to observe it from the air.
Given the geometrical and dynamical circumstances of this eclipse, a duration of totality approaching 10 minutes could have been obtained by observing from a jet aircraft intercepting the moon's shadow at the point of maximum eclipse. That point, however fell in the middle of the South Atlantic Ocean, and would have required a long and economically unfeasible flight. However, a jet aircraft could still provide both a long duration of totality (albeit, not so exceptionally long as nearly 10 minutes) and an almost guaranteed chance of clear skies by intercepting the path of totality at a point closer to landfall requiring a much shorter flying distance. This is what was proposed, and achieved by the eclipse flight organized by the Amateur Astronomers, Incorporated (AAI) of Cranford, New Jersey. This report, along with the enclosed supportive material, describes that sojourn from the perspective of three of it's participants; Glenn Schneider, who computed the intercept flight profiles and served as the navigator for the eclipse flight; Craig Small who, working with Rodger Tuthill, assisted in organizing and leading the AAI expedition; and Joel Moscowitz, a recent eclipse aficionado bitten by the totality bug after the July 11, 1991 eclipse. The commentary and remembrances which are described in the following report are derived from inputs from the three of us.
The AAI eclipse flight eventually evolved into an international expedition with 48 participants from the United States, Canada, Brazil, Germany, Japan, and Great Britain, and would use a VASP airline DC-10 to rendezvous with the moon's shadow at 11:25 U.T. on 30 June 1992 to enjoy 6 minutes and 15 seconds of glorious totality from 41,000 feet. The course of events leading to that moment had it's ups and downs, as does any endeavor worth pursuing. The concept for this adventure began nearly a year before the July 11, 1991 eclipse, when Schneider and veteran eclipse chaser John Beattie began looking in detail at the possibility of observing this eclipse from the air. As noted in a technical report issued by the former, while a solid, stable observing platform would be preferable to many, the chances of good weather for this eclipse from the ground would likely set many umbraphiles (including ourselves) looking to loftier heights.
Enter Roger Tuthill and AAI, who have sponsored and organized many other successful eclipse expeditions in the past. Tuthill recognized the need to observe this eclipse from the air managed to secure the use of a Boeing 737 from VASP Airlines, which would depart from Rio de Janerio to chase this eclipse. Schneider was then contacted and asked to compute the specific possible flight intercept profiles, given the operating envelope of that aircraft and come up with some potential nominal flight plans. The Boeing 737, while an excellent aircraft with an equally well suited navigation system had one major draw back. Since this is a twin-engine jet, safety regulation precluded it from flying more than 1000 km over the ocean. This set a constraint on the intercept time for mid-totality of 11:15 U.T., early on in the eclipse track. With typical winds aloft at 34,000 feet (the nominal flying altitude), the anticipated duration of totality would be 5 minutes and 20 seconds. The 737, also, has 35 usable passenger windows (on the "sun side" of the aircraft). This would then limit the number of potential eclipse viewers.
VASP had an available Douglass DC-10 which, given unlimited financial resources, would have been a better choice. The DC-10 had more windows (53), three engines (so the limitation on range due to safety constraints did not apply), and a range which would allow it to reach maximum eclipse. VASP agreed to keep that airplane available as an option should additional resources become available. For months plans were forged to use the 737 as this was commensurate with the size of our expedition. During those ensuing months Moshe Bain, a Brazilian amateur astronomer and member of the Astronomical Society of Sao Paulo, joined the expedition. Mr. Bain proved to be an invaluable asset in assisting with all of the multitude of details which needed tending to in preparation for this expedition.
Only weeks before our scheduled departure for Brazil, after we had reconciled ourselves to using the smaller 737, Tuthill began receiving many last minute queries about our flight. The 737 was at it's capacity, and Rodger began asking about the willingness for some people to share windows. Within days, this avalanche of late-comers swelled to the point where the Douglass DC-10 could be leased from VASP. While the addition of more people provided the means to secure the larger plane we would still be bound to a nominal 4-hour round-trip flight based on the contractual agreement with VASP. The fiscal realities of renting a DC-10 precluded taking it out to maximum eclipse. The DC-10 would provide a higher maximum service ceiling (41,000 feet), more windows for more eclipse observers, and more margin if it became necessary to alter the flight than the 737.
On June 25, the Tuthill's, Small and Schneider arrived in Sao Paulo and were met by a very hospitable Moshe and Valaria Bain. After settling in Sao Paulo we were invited to dinner with members of the Astronomical Society of Sao Paulo (ASSP) in the home of Helga Szmuck. Szmuck, who has been a recent regular attended of the Texas Star Party, has received their award for the participant who has traveled the longest distance. Helga has vowed to, next year, show up at Stellafane. Dinner consisted of a multi-hour exchange of ideas and thoughts about eclipses, astronomy, and telescope making. This was followed by a slide presentation where we were shown a variety of telescopes fabricated by ASSP members and delighted by the optical and mechanical skills of our new found Brazilian friends.
The following day, June 26, it was down to business. A technical meeting at VASP headquarters in Sao Paulo was held. We (Schneider, Tuthill, Small and Bain) would meet, collectively, for the first time with VASP's principle parties. The pilot for our flight was Captain Jorge Gabrial Isaac Filho, who became known to us as Gabriel. Gabrial was VASPs chief pilot for the DC-10 fleet, and intrigued by our proposition, had earlier arranged to command our flight and pick his flight crew.
Ours was not to be the only eclipse flight. VASP was providing a 737 to the Rio Planetarium. Members of the Planetarium staff, of their astronomy club, local dignitaries, politicians and celebrities were being invited to participate in this promotional flight. That aircraft, as it was to turn out, would have 99 eclipse viewers on board (sharing 35 windows - and the sun-side seats were not removed as in our aircraft).
At that meeting, following a technical presentation by us to the VASP representatives, describing the requirements for this particular flight, many specific items were addressed. Among those were the need to assure that all seats on the "sun-side" of the aircraft would be removed and the floor unobstructed. The windows were to be cleaned prior to the flight. The use of appropriate cleaning solvents, to prevent the formation of frost, and cleaning techniques (to prevent the addition of additional scratches) were discussed. 110V, 400Hz power would be needed from the aircraft power bus by Charles Cooper who would be using a gyro-stabilized platform and experimental photographic emulsions. Most importantly we discussed the primary and alternate flight plans, and our ability to alter those plans in real-time.
The Rio Planetarium flight would follow an unalterable flight plan, and would intercept mid-eclipse at 34,000 feet at 11:15 U.T. Our nominal intercept had been defined by the airline operations also for 11:15, but at 41,000 feet. We had noted that in the event of cloud cover, or clear-air turbulence the aircraft might be forced to the same altitude, and hence an intercept at the same time could force us to the same position which would be unacceptable. VASP informed us that a third plane would be in the vicinity, as they were dispatching a small chase plane to photograph their 737 with the eclipsed sun in the background. We, not wanting to risk any possibility of interference which would require last minute maneuvering offered that we must intercept further down track than the 737.
The two principle flight objectives were predicated on the desire to have the Sun directly out the aircraft's port side windows at mid-eclipse, and to arrive at local mid-eclipse in the geometrical center of the moon's shadow. To accomplish this, the aircraft would fly on a heading so that it's velocity vector would be orthogonal to the azimuth of the sun at mid-eclipse. This heading would depend upon the wind speed and direction. In addition it was desired to turn the aircraft onto that heading 8 minutes before second contact to allow time for final alignment, focus, and calibration of equipment which would be used to record the eclipse. To accomplish this Schneider had built a special software package for an Apple Powerbook 170 computer, which was used as the principle navigational aide in computing the aircraft's course from Rio to mid-eclipse. The aircraft's course, speed, and resulting ground speed and heading would be dynamically recomputed as needed to meet the constraints of an ephemeris model for the eclipse. The DC-10, at a cruising altitude of 41,000 ft normally flies at Mach 0.82. While some margin is possible to adjust the speed that margin is small and any significant change in windage would require computation of a new series of waypoints before and during the "totality run". This was reviewed with the pilot and the interface protocol discussed to assure that there would be no unexpected "gotchas" one the program had to be used for the real event. Following that meeting Tuthill traveled to Rio in preparation for meeting the majority of the expedition members which were still to arrive.
The enclosed slide, labeled #1 (in red), shows the VASP/AAI eclipse flight "team" after our technical meeting. Left-to-right are Craig Small, Captain Amerigo (the 737 pilot), Captain Gabrial, Moshe Bain, Rodger Tuthill, The VASP tour manager and operations manager (Marco Cesar Bonon) and Glenn Schneider.
That same evening, Small and Schneider were invited to visit the millimeter-wave radio telescope facility near Sao Paulo (Sky&Telescope, 1974). Members of the ASSP have constructed a small optical observatory at this site, housing a 20-cm. Cassegrain/Newtonian telescope which is used in the daytime to correlate Solar radio flare events with optical features. We took this opportunity to enjoy the Southern Sky.
On June 27, those of us who had remained in Sao Paulo flew to Rio to join the rest of the expedition members. Following a day of settling in, sightseeing, preliminary assembly of equipment and more computations, the next day we had our first formal meeting as a group at the Rio planetarium. Here the two eclipse-flight groups met for the first time. A special exhibition on the solar eclipse was set up at the planetarium, and much excitement ensued as the thong began to mill. Stories of eclipses passed were exchanged, and advise to eclipse novices offered. The director of the planetarium, Alexandre Cobbett, welcomed both groups and provided a lecture and demonstration in the planetarium. Tuthill amused the group at large with astronomical anecdotes (some of which, unfortunately lost something in the translation to Portuguese). Craig Small provided a slide presentation on the last eclipse chase he participated in by air. In attendance were some high school students who had been selected by VASP and O Globo (the Brazilian newspaper) to be on the Rio Planetarium's 737. Members of both the AAI and Rio planetarium groups can be seen in attendance during Cobbettin's lecture in Slide #2.
The delineation between days and hours as marked on calendars and clocks then lost meaning as E-hour began to approach. Many of us did not sleep again (and at least one even forgot to eat!) until after the eclipse still-to-come. On June 29 at 3PM local time, the group met for a pre-eclipse briefing. The nominal flight plan was discussed, and shown on a simulator running on the same computer which would be used to navigate the aircraft. Window assignments were made, photographic questions answered, and the best of luck wished to all. The group would not meet again until 3:30AM local time when two busses would pick up the assembled masses for transport to the International Airport and our awaiting DC-10.
After the meeting, Schneider, Small, Beattie, Tuthill, Bain and Moskowitz went to the Airport to inspect the DC-10 which was to have been flown up from Sao Paulo. Unfortunately, the airplane had not been delivered on schedule, and no-one seemed to know where it was. While waiting for the aircraft to appear Schneider went to the operations area to obtain a meteorological update. Nothing unusual had been anticipated, so the prognostication offered by the meteorologist on duty was staggering.
Normally, one does not worry about the effects of weather at these latitudes when flying at 41,000 feet. But Murphey's Law, being the powerful universal force that it is was about to strike. The high altitude jet stream, which had been held in check over central South America for months, by the modifying effects of El Nino, was being deflected over the Atlantic by strong cold front. The movement of the front had brought cumulonimbus clouds topping off at 39,000 feet along with it. The location of the front itself, along with the accompanying clouds and projected severe turbulence was projected to be right at the location of the 11:15 U.T. intercept at eclipse time! Even though our aircraft would be at 41,000 ft., the mere 2000 foot projected margin to the tops of the anticipated thunderheads was anything but reassuring. The on-duty meteorologist indicated that he would classify the anticipated turbulence as only "heavy" rather then "severe", so our flight would not be denied authorization to target for that location. (See the enclosed weather charts #1-3).
After this negative revelation from Met Ops, the DC-10 had arrived from Sao Paulo and the waiting group went to inspect the aircraft. The seats on the port-side had been removed as requested, and that side cleared of movable obstructions. A perfunctory cleaning of the windows had been done in Sao Paulo, but it was apparent that a thorough cleaning, inside and out, was needed for most of them. A member of VASP's ground support crew was present and understood our needs. He and others would work through the night cleaning the windows.
Following this gloomy prognostication for a very bumpy ride through totality, we had a subsequent discussion with Bonon, the VASP operations manager, about the possibility of flying further to get out of the region of anticipated turbulence. The winds aloft were being projected to produce a strong tail wind, on the order of 90 knots, which would allow us to fly faster on the way out and reach further down the path in less time. Of course, that would imply that we would have to fight this as a head wind on the return to Rio. Based on the latest set of weather parameters, and aircraft constraints, it was mutually agreed that we could fly out to intercept the shadow at 11:21 U.T. Note that a one minute difference in intercept time requires 8 to 10 minutes more of total flying time (depending upon where within our window we would intercept), since the moon's shadow is moving much faster than the aircraft. An 11:21 U.T. intercept would put us, based upon the E-18 hour weather prognostication, just barely ahead of the region of severe turbulence. Throughout the night Schneider was computing new baseline flight plans given the possible variations in the weather which might arise.
Since total solar eclipses are rare and precious events, a number of the more die-hard eclipse chasers in our band, lead by Mr. John Beattie, began to prepare for unthinkable contingencies. Beattie arranged for not one, but two small twin-engine jets to be standing by at the airport on eclipse morning to be available just-in-case something went wrong with the DC-10. Fortunately, those contingencies never had to be used.
At 3:30AM local time the busses arrived on time (a rare event in Brazil) to transport the anxious group to the International airport. Arriving at the airport there were no VASP people in sight, though we had indicated that we would arrive at 4:30AM local time. While waiting Schneider returned to Met Ops to get the latest forecast and returned with very encouraging news. The prognostication for the frontal movement had backed down from the previous forecast (see enclosed weather chart #4 and #5). The anticipation was that if we were to try for the 11:21 U.T mid-eclipse intercept that we would have turbulence, but it would be a moderately rather than severely bumpy flight - and that we would be well ahead of the "wall" of towering cumulonimbus which would be near the 11:15 U.T. intercept (see the enclosed charts and figures showing the circumstances for various mid-eclipse intercepts). Based on this the group as a whole decided to "go for broke" and the backup aircraft arranged by Beattie were both released.
To reach a mid-eclipse intercept at 11:21 U.T., assuming a mean wind speed of 95 knots at 41000 feet from 240°, would necessitate a take-off at 09:44 U.T. (including initial rate of climb, flight over the Marica VOR, etc.). A take-off any later than that and reaching the 11:21 U.T. intercept could not be assured.
We began boarding the aircraft shortly before 09:00 U.T. Schneider, assuming the role of flight navigator, joined the flight crew in the cockpit. By 09:23 U.T. the flight crew completed the aircraft pre-flight and began to push back at 09:24 U.T. There then was a knock at the cabin door. The operations manager (who was remaining on the flight, and who would see the eclipse with us), came to inform Gabrial that it was too soon to push back, since we did not need to take off until 09:44 U.T. Gabrial then informed him that "this is Rio" and he intended to take off as soon as possible. It seems, in Rio, ground control often holds planes on the ground for no apparent reason. Even though we had arranged for priority take-off, Gabrial would take no chances. He knew what it would mean if we got off late, and was using his digression to buy us the margin we might need in the air. Mr. Bonon returned to the passenger cabin for the early take-off.
As we began to taxi toward the runway there was a second knock on the cabin door. It seemed that one of the ground support personnel, caught off-guard by our early push-back time was still on the aircraft. She came to tell Gabriel that she needed to radio the gate to have the stairs rolled back out so she could exit the plane. Gabriel informed her that it was too late and that she would be coming with us. She was not happy about this, as she was expected to be working to support another flight and her supervisor would be upset (all this time we kept rolling toward the end of the runway for takeoff). Gabrial then radioed to have her supervisor advised that she would not be returning to work that morning and that we would have an unintended passenger. Initially disgruntled, she was about to be the luckiest woman in Rio, and the only person in the world to our knowledge, who would see this total eclipse by accident!
Clearance was obtained and we took off at 09:33 U.T.
With wheels up, 48 eclipse chasers, eight flight attendants, a flight crew
of three and an accidental tourist were headed for the moon's shadow.
|The early take-off meant that the way-points already computed for the 11:21 U.T. intercept would not work - we would arrive at the start of the totality run too early. After getting an initial navigation fix, a new set of way-points was computed for a slightly different run-start position, but even then it was apparent that we would still be there too soon. Once we reached cruising altitude, a new course was computed for an 11:22 U.T. intercept. The winds aloft were even stronger than predicted and the tail wind was pushing us down track too quickly. To compensate Gabrial slowed the aircraft to, what the manual said, was just a few knots above stall speed. We still were out of spec for an 11:22 U.T. intercept. A recomputation was done to compute a new course to shorten the pre-second contact portion of the totality run, which might marginally have worked if the wind did not change and the plane could be slowed a few more knots...|
Gabriel looked at Schneider , said "don't worry", and eked the DC-10 throttle down by half a hair at a time several times. After a few seconds the plane bumped and shuttered three times in rapid succession "Bump!, Bump!, Bump!". On the last bump Gabriel tweaked the throttle, barely, and said "OK, were back above stall speed". We stayed flying at barely above the aircraft's stall speed for some time. The wind however was shifting between 60 and 115 knots from 190° to 280°. Trying to maintain an early mid-eclipse intercept, by using up all of our in-flight margin resulting from our early take-off was simply cutting it too close. Biting the bullet a new final course (except for wind corrections) was computed, and at 10:05 U.T. an intercept for 11:25 U.T. was locked in. The anticipated duration of totality was 6 minutes and 15 seconds.
While all of the action in the cockpit was transpiring, the rest of the band of eclipse chasers in the passenger cabin began to set up photographic equipment of every sort. First contact was noted by many shortly after 09:55 U.T. During the next 20 minutes of flight a number of the passenger windows had begun to show signs of interior condensation. This was anticipated and the flight engineer was asked to crank up the cabin heat. At the pre-flight meeting the day before, members of the AAI group were advised of this possibility and told to dress lightly should we have to heat up the cabin. Fortunately most of the gang-of-48 took heed of this warning. Over the next 40 minutes, as the cabin heat increased the condensation disappeared.
The flight out, as the waning sun diminished, was smooth until 10:50 U.T., when the first effects of the frontal turbulence we were passing near began to be felt. Concern was rising about the level of turbulence we could expect during totality. From this point on the flight would remain bumpy, to varying degrees until our return to Rio.
As planned at 11:14 U.T. the DC-10 executed a turn to
put us on the totality run (see enclosed sheet for geographic coordinates
and other information related to the actual totality run). For the
next 40 seconds as the aircraft turned through a heading alignment circle
of approximately 30°, the sun which had previously been viewed askew
out the windows was put abeam the aircraft. Once on this heading,
flying the final course laid-in to the flight computer after the last windage
corrections, the adrenaline level really began to flow.
|As the last few minutes ticked by a watch was kept out the windows opposite the sun. As the brightness level outside the aircraft continued to fall cries of "There's the shadow" reverberated in the aircraft cabin. And it was so. The broad sweep of the leading edge of the projected umbral cone was easily discernible from our vantage point at 41,000 feet. Not a dusky pallor, but a definitive arced line of darkness to the south-west of the plane was speeding to over take us.|
|Three effects were obvious. The umbra/out-of-eclipse interface in the atmosphere was definitive. A curved arc of darkness was slicing through the sky. The projection of this diminution of light on the ground and cloud tops was stunning, and at the boundary between dimmed daylight and lunar induced twilight the reddish glow of chromospheral light was unmistakable. Many were torn between watching the last moments of the partial eclipse out the port-side windows, or the enveloping inrush of the lunar shadow out the starboard side.|
Slides #3 and #4, showing the sky, horizon, and ground
coloration due to the oncoming shadow were taken at approximately 2 minutes,
and 30 seconds, before second contact. The view in both of these
pictures is toward the oncoming shadow. Both slides were taken with
a 24mm lens. Number 3, by Moskowitz was on Ektachrome-400X, and #4
by Schneider on Kodachrome 64.
|As the last bit of photospheric light began to wane, all 120 eyes aboard our DC-10 were riveted on the Sun. And then it happened, within one second of the predicted time at 11:21:53 U.T. a single beacon of sunlight remained, and the corona, apparently, welled up in intensity. Surrounded by ruby baguettes of H-Alpha light a transitory diamond ring sparked and winked out accompanied by a multi-lingual wail of cries. Totality had come. For some again. For some for the first time. For all, to be remembered forever.|
Visually the first moments of totality were stunning beyond
words. Photographically the jitter induced by the turbulent atmosphere
was taking it's toll. It became apparent that really good photographs
of this eclipse would be rare, and that the best way to capture this eclipse
would not be on film or video but etched in our minds. Window scratches,
smudges, optical distortions and continual shaking degraded the quality
of most photographic images, but the brain's image processing capability
|Slides #5, 6 (by Schneider) , and 7 (by Moskowitz) show panoramic horizon views of the totally eclipsed eclipse (using a 24mm lens), and the unmistakable delineation between the umbra and the zone outsize of the path of totality. At the interface the golden/red color from scattered chromospheric light was unmistakable. The colors of the sky, and of the corona seemed to take on pastel hues; subdued a bit perhaps due to airborne dust and/or aerosols released from Mt. Pinotubo. While the sky at this altitude was remarkably clear and lacking in scintillation, the effect of these airborne particles on the coloration was apparent. In both slides 6 and 7, the planet Venus, at magnitude -3.9 can be seen approximately 5° from the Sun (on the "lower right" side of the sun").|
Slide #8, taken by Moskowitz, is a 1/1000th second exposure on Ektachrome-400X at f/8 using a 500mm catadioptric lens. This photograph shows the inner corona and one of the few prominences which were seen at this eclipse. The sun was quiet at this time and only a few small prominences were seen shortly after second contact (as exhibited in this photograph), and just prior to third contact, near the points of limb tangency.
Slide #9 and #10, taken by Schneider on Kodachrome-64 are 1/125th second exposures using a 400mm lens at f/6.3 and show the solar chromosphere shortly after second contact (As well as the most inner regions of the corona on the opposite side of the disk).
While this eclipse was lacking in the dramatic prominences,
of the sort which were seen in the eclipses of 1991, 1988 and 1979, this
was more than made up for by the extent and intricate structure of the
corona itself. Experienced eclipse chasers removed eye patches and
the true visual extent of the corona was unveiled. Easily seen, on
average, to 6 solar radii beyond the disk. Coronal streamers with
entwined and linear structures were seen on both the western and eastern
sides of the sun. Overall the shape and structure of the corona,
and morphology of the streamers, were similar to the 1991 eclipse, but
with a uniqueness in detail.
Of the three of us contributing to this report, none of us achieved undistorted images of the outer regions of the solar corona. Turbulence was the principle cause of the difficulty of obtaining longer exposures of reasonable quality. All hope is not lost, however. Schneider is applying some image deconvolution techniques, not unlike those used in restoring inherent spatial resolution in Hubble Space Telescope WF/PC images. An approximation of the image spread function convolved with the raw eclipse images may be determined. In the longer, blurry, images of the corona, the edge of the lunar disk represents a high contrast, steep gradient feature (which has been degraded by image motion). It is known, however, that the edge of the lunar disk should be, approximately, a circular feature. By applying a modified steepest-gradient edge-detection algorithm the 2-dimensional (X/Y) residuals from the gradient determined edge are used to produce an image spread function. A deconvolution technique such as simple Fourier inversion, or the Lucy method, can then be applied to recover the source function (i.e., the un-jittered image).
The application of these techniques to these images have several problems. First differential optical distortions in the aircraft windows cannot be completely removed (or in some cases not at all). In addition, since the solar altitude was close to 30°, the line-of-site to the sun through the windows was not orthogonal so chromatic aberration was introduced. The effect of this has been seen when the original transparencies were digitally scanned with a 3-color filter set. The "red" digital image, in particular was shifted considerably from the blue and the green.
The work to restore some of the long exposure images will be in progress over the next several months and a follow-up to Sky&Telescope will be sent. As a preliminary indication that there may be some hope, a partially restored image from a blurry 1/8 second exposure initially taken on Kodachrome-64 is enclosed. This gray-scale print is made from the blue-filter scan of that original frame, restored by simple iterative Fourier inversion using a multipass "Clean" algorithm. The intention of this image is to show the gradations in coronal intensity as a function of the radial distance from the edge of the disk.
Returning to the more esthetic side of the eclipse, Slide #11, by Moskowitz, shows totality out one of the passenger windows. This picture was captured near the end of totality. A portion of the elliptical edge of the shadow is also captured in this wide angle photograph.
Slide #12, by Small, is a 1/125th second, 35mm wide angle image taken on Kodachrome 400, and shows the receding shadow off toward the horizon and a reddish band of chromospheric light at the shadows edge.
Slide #13, also by Small, shows the edge of the shadow a short while later as it continued to move off to the north east.
Given the "boost" from the aircraft's speed the totality was seen for a duration of 6m15s. The third contact diamond ring was accompanied by the now almost-expected primal screams from umbraphiles assembled from around the globe. "AAArugghhh" sound much the same in German, Japanese, or Portuguese.
We had planned to watch the receding shadow for three minutes, and then execute a turn back to Rio after the last way-point previously entered into the DC-10's navigation computer had been reached. Nearly five minutes after third contact we were still on the last heading of the "totality run". Schneider returned to the cockpit to see what was wrong, only to find the pilot, co-pilot and flight engineer transfixed by the sight of the moon's shadow out the pilot's side of the aircraft. The DC-10 was flying itself (and probably would have gone all the way to Africa). Reluctantly, but with jubilant enthusiasm, the newest eclipse-addict in our midst, Captain Gabrial Isaac, Jr. turned his aircraft away from the moon's shadow. In all his years, the captain indicated, that this was the most unusual flight he ever commanded. His proclamation that this was "very exciting, much more so than say an engine fire", was an understatement belied only by his manic smile and coronal light still glowing in his eyes.
Jubilation and exhaustion abounded on the return flight. Even our initially disgruntled accidental passenger enjoyed it. Few, if any watched the waning partial eclipse as the big show was over. Small's eclipse flag flew in the cockpit of the DC-10 (the airline was reluctant to allow us to hang it off of the tail), after it's 15th time in totality and always under clear skies.
On the return flight there was much interest in what course
we had actually flown. Although everyone had been notified of the
final decision to intercept at 11:25 U.T., few aboard had seen what that
meant in terms of where we actually were. A graphic demonstration
of the path we had flown, and the movement of the moon's shadow, was shown
to the passengers on the same notebook computer which was used for the
real-time navigation of the flight (Slide #14). This time, not using
simulated data, or projections, but using the actual flight data.
(Though a commercial endorsement is probably not appropriate here, much
Kudos to Apple computer for their Powerbook 170. Though we may have
seen the eclipse without one, we probably would not have had such accurate
course corrections, and certainly not without much more difficulty).
The flight and cabin crews which accompanied us to our latest rendezvous with the moon's shadow are shown in celebration with the eclipse flag in slide #15. To obtain photographs of our band of eclipse chasers by our DC-10, once on the ground Captain Gabrial taxied the aircraft to the very end of the runway, to the furthest point on the tarmac. Slide #16 shows several post-climatic eclipse chasers and our trusty DC-10.
That night, at our victory celebration, toasting traditionally with Egg Creams (made from Fox's U-Bet chocolate syrup), we all vowed to meet again under the moon's shadow in the clear skies of the northern Chilean desert on November 3, 1994. Our pilot could not attend our celebration, as he had to return our airplane (we all felt it was ours by this time) to Sao Paulo. We still owe him a beer (or an Egg Cream), and have promised him both when he visits us here in the U.S.
At that celebration Mr. Bonon advised us of the success of the Rio Planetarium's 737 eclipse flight. Apparently, just minutes before second contact, Captain Americo had run up against the "Wall of clouds" associated with the cold front which we had managed to avoid. At the last minute their aircraft changed altitude and managed to get over the cloud tops at 38,000 ft, though we understand that the turbulence they experienced was far greater than what we had on our DC-10. The chase plane dispatched by VASP also saw the eclipse, but due to unexpected altitude change of the 737 (and the wall of clouds!) the two planes lost sight of each other and ended up 16 mile apart during the eclipse.
Finally, Roger Tuthill, exercising some real Chutzpah, had his roll of eclipse film developed in Rio - with some excellent results. Roger managed, it seems, on a few occasions to squeeze off some exposures between turbulent bumps of the aircraft. On the "morning after" Moshe and Valeria Bain, our new Brazilian friends and hosts are seen examining some of Rogers pictures over breakfast. Their smiles reflect not only their memories of the day before, but that fact that the next total solar eclipse will mark the third one in a row which will pass over their country. (We should be so lucky!).
This concludes our report on the Great Airborne Eclipse Chase of 1992. Unquestionably we would all do it over again in a minute, though the thought of good solid dirt to set up in for the eclipse of 1994 is most comforting. Until then, Clear skies and good seeing!
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