1999, August 11. Cornwall, England
For the last total solar eclipse of the millennium, I decided to return to my native England. I have friends in Looe, Cornwall and so used this location as a base for observing the eclipse.
This was to be my second total solar eclipse, the first being the 1994, November 3rd eclipse viewed from Bolivia. Totality lasted over 4 minutes for that one, over twice the one-minute and forty-five seconds available at our chosen site in Cornwall. However, I left that first eclipse determined that the next one would be viewed in its entirety. In Bolivia, I photographed throughout totality, and while I left with some great memories, I was too wrapped up in the imaging to fully appreciate the event.
The challenge was to design a system that would allow me to photograph the event, and at the same time view the entire eclipse un-hindered. This meant automation.
The Automated System
My goal was to be able to sequence the various shots of the partial phases, and (most importantly) totality, without having to manually operate anything. After some research, I selected the Nikon N90s 35mm camera. This was the only system (apart from the more expensive F5) that offered a remote computer controlled interface, which would then allow me to automate the entire process.
The Nikon N90s has PC software called Photo-Secretary.
This allows all the functions of the camera to be controlled from the computer
keyboard. An interface cable allows computer commands to be actioned by
the camera. I wrote some code in Visual Basic 6.0 to send the various key
strokes to the Photo-Secretary software automatically. In particular, I
was able to select timings, shutter speed, number of exposures, bracketing
etc. as well as controlling the MF-26 Databack.
To ensure that the software triggered the camera at the correct times, I also added code which when provided with the geographical coordinates of our location, calculated first through forth contact times and also the duration of totality. I validated this code against the NASA predictions and in all cases the code agreed with their timings to less that one-second. The system accepted a pre-defined exposure timing sequence and aligned this with the all-important second contact event.
I then pre-programmed a sequence of exposures to cover the entire event, from before first contact until after forth contact. From our selected site we were to be blessed with one-minute and forty-five seconds of totality, I generated a sequence which would expose over 70 images of the event, with 30 shots centered around totality itself. All I needed to do was change the film in the camera a couple of times (before and after totality), and so the rest of the time I could dedicate all my time and thoughts to the eclipse itself.
A Polar Alignment option was added to calculate Sidereal time so that the orientation of the Equatorial mount could be verified during daylight. This process can be achieved by first setting the scope on the Meridian and adjusting the Setting Circles to the local Sidereal time. Then move the scope to point at the current coordinates of the Sun (the only object visible - hopefully), and then adjusting in azimuth until the Sun is again centered in the scope. By systematically repeating this process the total alignment error can be reduced to close to zero, much better than by just using a compass.
complete photographic setup consists of an AstroPhysics Traveler mounted
on a Losmandy GM-8. A Toshiba notebook computer controlling the Nikon N90s
completed the setup. The whole system is powered by batteries and so is
completely portable. A Thousand Oaks type-2 Solar filter is used for photography
of the partial phases.
On the big day, and just as expected, the British weather demonstrated its defiance and presented us with heavy cloud cover, thickening as time went on. A check of the satellite image confirmed our worst fears that this was likely to persist throughout the day, and so all we could do was stand and wait and hope for a miracle.
Sadly, a miracle did not occur. At one point the
clouds thinned enough for us to gain a glimpse of the partial phase just
after first contact, but again the Sun and Moon disappeared from view,
not to be seen until well after third contact. The good news is that the
automated system performed flawlessly, and I obtained an impressive sequence
of cloud images!! While disappointing, I now know that I can use this setup
for future eclipses as well as many other events that can be automated.
AP Traveler. 1/8000 sec f5.8. No Solar filter.
This eclipse was still very memorable. Even through the clouds the onset of totality was very evident, and the reaction of the confused seagulls circling all around will remain with me forever. My software performed a countdown to each contact event and so we were able to follow the progression of totality even though we could not see it directly. Observing the brightening sky signaling the end of totality rushing towards us from the West was amazing, something that I had just not appreciated when in Bolivia.
It's sad when I think that I hauled all that equipment 6000 miles and then did not get to see a thing, but I would not have missed this for anything. I am already planning for Africa in June 2001, and with well over four minutes of totality that one promises to be spectacular.
Disappointed, but still smiling.... the eclipse
(from left to right: Chris Cook & wife, Jennifer. David Churchill & girlfriend, Nina Mae. Jim Janusz & wife, Karen)
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Last Update 09/04/99
© copyright 1999 by David Churchill.