By Jim Melvin
CLEMSON, South Carolina – Clemson University scientist Donald Liebenberg has personally witnessed and researched 26 total solar eclipses over the past 60-plus years.
Liebenberg, who has been an adjunct professor in the College of Science’s department of physics and astronomy since 1996, has literally travelled all over the world to enter the path of totality of solar eclipses. He has studied them from the ground, on ships in the middle of oceans, and in airplanes. He even watched one eclipse from the cabin of a Concorde supersonic airliner, where he was able to remain within the window of totality for an astounding 74 minutes.
Liebenberg’s seventh and eighth eclipses, chronicled below, were in an Air Force NC-135 jet commissioned to the Los Alamos National Laboratory (LANL). These occurred on March 7, 1970 above Mexico and the Gulf of Mexico and on July 10, 1972 above Canada. His ninth eclipse was on the Concorde 001 on June 30, 1973 above Western Africa. However, equipment he helped design was used on the NC-135 in 1973, which flew in conjunction with the Concorde. Therefore, the 1973 description of the NC-135’s flight is chronicled below. Liebenberg’s experience aboard the Concorde will begin in our next installment.
Liebenberg’s last eclipse was March 9, 2016 aboard the cruise ship MS Vollendam off the coast of Indonesia.
All told, Liebenberg has spent almost three hours in totality, which surpasses anyone else in the world.
The upcoming Aug. 21, 2017 event over Clemson will mark Liebenberg’s 27th eclipse. He has also witnessed several other eclipses that were nearly – but not quite – in the path of totality.
Today is the seventh chronicle of all 26 of Liebenberg’s eclipse adventures on our Eclipse Over Clemson blog. During a few of the installments, such as this one, Liebenberg will describe more than one eclipse.
Please sit back and continue to enjoy this amazing adventure.
Eclipse No. 7: March 7, 1970 Totality: 5 minutes, 30 seconds
Where: Over Mexico and the Gulf of Mexico Weather conditions: clear
From the logistics standpoint, this eclipse was ideal. Our NC-135 aircraft, which was commissioned to LANL, had been fitted with a 16-inch diameter window to accommodate our hydraulically stabilized 10-inch objective telescope with photoelectric and gyros sensors.
However, the photoelectric data sensor seemed inadequate, and Dr. Marvin Hoffman and Mort Sanders of LANL suggested we use an image-intensified video system and tape recorder to record the full Fabry-Perot fringe system superimposed on the corona. This created a significant improvement from the equipment setup we had used onboard during our 1965 and 1966 eclipses – and turned out to be very useful during later eclipses, as well.
Dr. Jacques Beckers from the Sacramento Peak Solar Observatory came on board, and we added a polarization measurement to the coronal line data based on coronagraph observations by Dr. Charlie Hyder at HAO. A polarizer attached to the outside of the aircraft came off at takeoff, so that test was not continued. Later, we added a Biot-Savart plate and got good polarization data.
A BEAR OF AN ECLIPSE
Eclipse No. 8: July 10, 1972 . Totality: 3 minutes, 44 seconds
Where: Over Canada Weather conditions: clear
This eclipse path covered much of North America, but totality was at its maximum over Canada. We staged out of the Fairchild Air Force Base near Spokane, Washington. The aircraft would land at an airfield near Hudson Bay (Fort Albany or Churchill).
The NC-135 was reconfigured for our eclipse studies, and we headed to Spokane, though we did enjoy some sightseeing in Couer d’Alene. Before takeoff the next morning, a TV news crew interviewed Art Cox and me about the purpose of the mission. Media interest in our eclipse experiments was continuing to build.
The eclipse flight was flawless with clear skies and good data collected from the scanning FPI during the three minutes and 44 seconds we enjoyed in totality. This eclipse was special to me because I was in totality on my 40th birthday.
We landed in Canada near a village close to Hudson Bay. While we didn’t have clearance to be in Canada, a van and driver appeared and the Canadian authorities agreed that we could have a tour of the area if we stayed in the van. The van driver took us to see the Hudson Bay shoreline, where we saw a polar bear, and then he stopped at a souvenir shop. The driver said it was okay to go in and shop, and I bought a carved polar bear for my wife Norma. I think the shop owner was a brother of our driver. But in any case, we had a nice tour while the plane was refueling.
JOURNEY OVER AFRICA
Eclipse No. 9: June 30, 1973 Totality: about 12 minutes
Where: Over Western Africa Weather conditions: clear
Our NC-135 aircraft was fitted with the telescope, filters, FPI and the image intensifier video system that I had helped design. Dr. Marvin Hoffman was in charge. The plan was laid out to use FeXIV, FeX and CaXV filters to capture emission line fringes and a Biot-Savart plate to look for polarization in the emission line due to the magnetic fields threading the corona.
Biot-Savart fringes show evidence of polarization related to the magnetic field structure very close to the solar surface. The data taken by Hoffman and the rest of the team were excellent and the tracking very secure.
The CaXV emission was more extensive than expected, indicating a higher temperature in the same regions of the corona as the FeXIV emission. The instrument took samples along a line of sight normal to the disk in the sky so that various parts of the corona such as the ropes and ribbons that are seen now in satellite pictures could be at different temperatures. However, since the coronal line intensity varies approximately as the reciprocal of the radial distance to the sixth power, the information along the line of sight comes from a rather limited region of the corona. An interesting feature of this data is that by integrating over a scan from one Fabry-Perot fringe order to the next, a picture of the corona in the emission line light is obtained.
The NC-135 aircraft extended the totality to about 12 minutes, compared to the best location on the ground of less than eight minutes.
Meanwhile, during this same eclipse, I was flying about 20,000 feet higher in the Concorde 001. Of all the eclipses I have witnessed and researched, this one was by far the most spectacular and noteworthy. Therefore, my next two installments – parts 8-9 – will focus on my experience aboard the Concorde.
Up next: Part 8