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The solar analemma

The installation used by Steve irvine to picture the analemma. Detail on http://www.steveirvine.com/

Text and pictures by Anthony AYIOMAMITIS

Photographic Notes (II)

With the critical "theoretical" issues now out of the way, it was time to address the type of film to use in conjunction with my solar filter material and camera lens. Since the Baader solar filter material is rated at ND-5, software calculations suggested an exposure of 1/500th sec when stopped at f/11 using an ISO 200 color film emulsion (e.g. Fuji Super HQ 200).

In order to compensate for days with potential haze or cloud cover or during the winter when the sun is lower and not as bright due to atmospheric effects, I decided to purposely overexpose by three stops and image at 1/60th sec. A 60 mm x 60 mm square of the Baader solar material was cut and inserted between the filter threads of the wide angle lens and its 52 mm UV filter; the filter was then threaded into the lens carefully so as not to tear the filter material. A test roll was shot to confirm the absence of any light leaks due to tearing or shearing as well as the suitability of the selected f/stop and exposure.

To download : Exposure Calculator

A software from Michael A. Covington

The final consideration is, of course, the stability of the camera and its mount. Rather than risk the accidental bumping of a tripod over the next twelve months (at least 43 such opportunities for an accidental bump), I constructed a two-part mount for my Canon A-1. The first was made of laminate material and permanently held firmly in place using carpenter's clamps (everything was covered with very durable material - used for 20 kg bags of dry dog food - for protection from rain which could soak and expand my laminate material and, consequently, destroy my permanent and fixed direction) (see Figure 2).

The second mount was permanently attached to my camera - using silicon between the back of the camera and the vertical support behind it as well as the camera base plate and mount - with the camera and its permanent support sliding very tightly into the permanent laminate base (potential cold weather and rain during the winter season did not permit for the camera to be permanently left outside) (see also Figure 2). Also, a one-inch diameter whole was drilled into the permanent camera support for the Canon AE-1 camera bodies below the film rewind button so that the unorthodox method described below for taking multi-exposures with these cameras could be realized. Every four months, additional silicone material was applied to reinforce the bond between camera body and mount.

Here are the reflex cameras used and their wood support constitued of two parts :

The tripping of the shutter release cable at precisely 06:00:00 UT was preceded by my pinging to a time server operated by the US National Institute of Standards and Technology (NIST) using the free software "Atomic Clock Sync V2.0" ten minutes prior to the proposed imaging for the calibration of my cellular phone to the atomic time-scale operated by NIST so as to be accurate to within +0.5 seconds (even a deviation of a few seconds, especially around the late summer, will show up as a significant "outlier" in the final analemma). the time can also be check listening to dedicated shortwaves frequencies.

Connect you to Time Servers:

BIPM (France) - NIST (USA) - Time in any city - ClockLink

First Marathon Attempt

With a shutter release cable hooked up and a fresh battery inserted into my Canon A-1, the first of eleven analemmas with imaging at 06:00:00 UT was under way starting at the summer solstice (Jun 21/01) and scheduled for completion in early June, 2002.

In corresponding with Dennis di Cicco a couple of weeks following the start of the first analemma, I was delighted to learn that a perfectly vertical analemma on the meridian, corresponding to imaging at 10:28:16UT, had yet to be produced. As I was already slightly past the summer solstice, I had to determine the time that Mars one evening would be at precisely 180 azimuth so as to calibrate the perfect placement of the camera and its mount with respect to azimuth and, thereby, avoid any possible distortion effects from my wide-angle lens and to also ensure that the introduction of a composite image upon completion would be an easy task. Once this was completed, yet another analemma was immediately initiated using my second Canon A-1 camera. Of course, greed and determination got the better part of me and a further four analemmas (07:00:00 to 10:00:00 UT) were started very shortly thereafter as well since my ultimate objective was to produce a complete set of analemmas (one-hour intervals between 06:00:00 and 15:00:00 UT and at 10:28:16 UT for the special meridian case).

The analemma of 6h UT over Tholos, Ancient Delphi.

With six analemmas in progress by late summer of 2001 and, regrettably, another five remaining as outstanding items literally made for some sleepless nights. The acquisition of yet additional Canon camera gear during the days and weeks that were to follow had set me in motion towards a very special and productive 2002 as I was under way in producing eleven analemmas representing the complete gamut from sunrise to sunset.  

With the passage of time, potential obstacles seemed to be nothing but minor nuances. Two strong earthquakes (Jul 26/01: 5.7 Richter, Oct /01: 5.2 Richter) did not impact any of my permanent mounts or analemmas in progress. Uncharacteristic bad weather surfaced on a large and fatal scale in early Nov/2001 when between planned exposure dates severely adverse weather over four consecutive days led to loss of life and hundreds of flooded homes in the immediate area due to such heavy rainfall not seen for many decades. Being physically situated on the side of a mountain not only helped me bypass both personal and property damage but enabled me to keep focused on the eleven analemmas in progress. 

However, it is at this time that I realized that, in retrospect, I should have constructed my permanent mounts of metal and not laminated wood material since exposure to these heavy rains, in spite of the aggressive protection in place, did make the previously tight fit with the camera mounts now even more tighter and necessitated the forceful pushing of the camera mount into the permanent mount for two of the cameras involved. Also, analysis of the associated ephemeris during these four days suggested that the impact would have been negligible anyway even if I were to trip the shutter at +2 or +3 days later than planned since the daily movement of the sun across the sky in November is relatively "slow". Nevertheless, I would lose during this four-day storm my opportunity to take a multi-exposure of the partially obstructed solar disk for the latest analemma (15:00:00 UT) which was to serve as a partial replacement for the six exposures which would ultimately be forfeited around both sides of the winter apex due to a physical obstruction (a mountain again) that could not be circumvented.

 The weather conditions were potentially the greatest factor in causing grief and havoc as I explain in the last page.

The analemma of 7h UT over Apollo's temple, in the ancient Corinth.

To this end, I religiously checked the weather conditions a day prior to my proposed shooting and did so sufficiently early during the day so as to possibly advance my schedule by one day in the event rains and/or heavy clouds were predicted for the scheduled day as well as the day thereafter, for I was very determined not to deviate from my proposed shooting sequence by more than + 1 day due to the desired symmetry (vertically and horizontally) in the completed analemmas (sole exception is the crossover point where absolutely no deviation is possible).

With my first two analemmas (06:00:00 UT and 10:28:16 UT) about 50% completed, I would for the first time forcefully deviate from this sacred wish in early December, 2001 when my scheduled exposure was not only missed for that day but daily heavy cloud conditions and/or rain - the worst rainfall for December in over a decade and greatest snowfall in over 39 years - did not permit for any supplementary imaging for the two weeks that were to follow and, consequently, a much undesirable "gap" immediately before the winter apex was to be a common characteristic and trademark for all of these analemmas upon completion (they reflect the strong anger of the Greek gods!).

The more and more I thought about this missed multi-exposure, the more aggravating the whole situation became for the simple reason that I wanted a perfect set of analemmas from sunrise to sunset. With daily weather predictions for my next scheduled multi-exposure, the winter solstice on Dec 21/01, consistently showing heavily clouded skies, I began to entertain the unthinkable. Upon confirming the presence of overcast skies on the early morning of winter solstice, I formally executed the fateful and humbling decision to restart all analemmas and forego the well over 100 total multi-exposures taken to-date. To this end, in early Jan/2002 and with perfect overhead skies, I restarted all eleven analemmas so as to have a potential time series spanning a single calendar year, something that is not characteristic of any of the successful analemmas to-date (the analemma by HJP Arnold and described by di Cicco was the closest to have been taken during a single calendar year as it ran from Jan/88 to Jan/89). 

Although very disappointed at turning my back on so much work and time, delaying the appearance of completed analemmas by six months (assuming no similar future compromising events), risking the first appearance of a perfectly vertical analemma on the meridian by someone else and rolling the dice again for the next twelve months, this decision had the benefit of permitting all eleven analemmas to have a common start and end point as well as representing the sun's movement over the local skies precisely during one calendar year. I purposely refrained from continuing the existing multi-exposures and simply waiting for Dec 3/02 and Dec 21/02 where I could hopefully reshoot the missed exposures for those days as the multi-exposures would then not have been over twelve consecutive months. Similarly, purposely skipping the Jan 12/02 exposure so as to re-establish the horizontal symmetry but now with two less total exposures per analemma may seem like a suitable fix but is also not a viable option since the vertical symmetry had already been adversely impacted by the Dec 03/01 missed exposure and was beyond repair.

Next chapter

Second Marathon Attempt

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