The
solar analemma
|
The
analemma of 10h UT over Zeus' temple, Athens. |
Text
and pictures by Anthony AYIOMAMITIS
Problems
and Issues (IV)
My
initial expectations with respect to potential problems and issues
centered on the weather. I have always felt that skies in Greece are
sufficiently clear and stable to challenge the infamous clear skies
of Arizona and this was something that I would formally reconfirm
during the course of this project which lasted nearly two years (see Table 3).
However, I soon discovered that my only real challenge was the
accidental tripping of the film advance lever as it repeatedly did
ruin a number of analemmas (fortunately early during the shooting
schedule of the first run causing restarts up to nearly three months
later than the original start date).
As
a key consideration and objective of this twelve-month exercise was to
generate Figure 14 using actual analemmas - in lieu of the theoretical
figure in the di Cicco article (S&T, Mar/2000, pg 136) - I sought to
not only use the same physical lens (Canon FD 24 mm f/2.8) for all 473
images (11 analemmas with 43 images per analemma) but also the same camera
bodies that were fully compatible with this lens. My two personal Canon
A-1 series cameras have a specific switch for multi-exposures that make
this exercise a no-brainer.
However, the Canon AE-1 series camera which is also
fully compatible with the FD series of lenses does not have such a
feature and the interested photographer must resort to the
unorthodox technique of tripping the rewind button at the camera
base plate and then advancing the film lever.
For
some bodies of the Canon AE-1, there is enough extra friction in the
mechanism to move the film a bit even though the rewind button has
been pushed - once the film moves, however slightly, the rewind
button will pop back out and re-engage the advance and, as a result,
render this backdoor method useless.
|
The
analemma of 10:28:16 UT over
Parthenon, Athens. |
Regrettably, it is this
unfortunate scenario that repeatedly ruined a number of my analemmas
during the first two to three months of this project. For the three
"problem" Canon AE-1's, I would soon discover that I would
have to trip and hold in place firmly the rewind button at the
camera base plate using a small flat screwdriver while simultaneously advancing the film lever. With a fourth Canon AE-1
body (09:00:00-10:00:00 UT analemmas), I would simply totally
forget the above modus operandi on one occasion (Sep 26/01) and ruin
yet another double analemma in progress losing four weeks worth of
imaging.
The most problematic Canon AE-1 body was later purposely
reassigned to a single analemma (15:00:00 UT) so as to minimize the
number of desired multi-exposures from 86 (double analemma) to 43
(single analemma).
Nevertheless, imaging with this camera was
restarted on five different occasions and, on the fifth and final
restart, I did consider prematurely retiring this camera body by
personally "launching" it into satellite orbit and
pursuing a replacement immediately thereafter,
thus finally terminating this chronic and incessant
"Greek tragedy".
After frequent aborted starts, all involving my newly
acquired Canon AE-1 camera bodies and with sufficient lost
multi-exposures to assemble the equivalent of nearly three
analemmas, I prepared a checklist (Table
4) so as to eliminate,
where possible, any future and further additional delays or
accidents wherever possible.
Readers interested in pursuing
analemmas of their own using the Canon A series cameras should
certainly select the Canon A-1 as its built-in multi-exposure mode
is ideally suited for this project.
In contrast, each of the five
Canon AE-1 bodies led to at least two restarts due to a failure in
the unorthodox method for taking multi-exposures mentioned above and
which painfully reminded me of the classic ancient Greek story about
the punishment Hades handed out to Sisyphus to roll a block of stone
up against a very steep hill which would eventually roll back down
as he reached the top; Sisyphus would have to restart all over again
and would keep doing so for eternity!
|
The
analemma of 11h UT over Athens. |
Nevertheless, my heart would stop each and every time I would
engage the film advance lever on my various Canon A-1 and AE-1
cameras as one accidental true film advance and the complete
analemma to-date (or two analemmas if imaging a multiple analemma
which I eventually did successfully accomplish using four of the
cameras) is rendered incomplete and, therefore, meaningless ! Of
course, this cardiac arrhythmia would be something that would
progressively get worse and worse with each analemma that would
progress further and further between accidental film advances.
On a related note, the field of view of my Canon FD
24mm f/2.8
lens (53° x 74° arc coverage in landscape mode) is such that it was
possible to attempt a double analemma photo. Very careful placement
of the permanent mount with respect to azimuth and even greater care
in the determination of the altitude for the camera mount was
exercised due to the extremely little room left for error.
Using the
figures in Table 1 for example, the range in altitude for the
09:00:00-10:00:00 UT double analemma (48.8°) is such that an error
less than 10% is available or, practically, less than 5% in either
direction. The tolerance for error was even less for the
11:00:00-12:00:00 UT analemma where the range in altitude was 49.3°.
A blessing in disguise is the fact that if an error does occur in
the proper placement of the camera and/or its permanent mount with
respect to altitude and azimuth respectively, one complete analemma
should still be produced once the exercise has been completed.
|
The
analemma of 12h UT over the Temple of Aphaia (490-480 BC),
Athens. |
Aside from a camera with the ability to properly take
multiple exposures, an appropriate wide-angle lens and a shutter
release cable, it is also advisable that a right angle finder (such
as the Canon Angle Finder B) be used to assist in properly framing
the analemma (vis a vis the lack of available tolerance for error,
for example, if imaging a double analemma) and for monitoring the
progress of the imaging, for five of the eleven analemmas in this
exercise had a maximum altitude in excess of 65°.
Something that was overlooked but became obvious after the
fact is the camera straps which hang freely while one is carrying
the camera with mount in his/her hand. These straps have a tendency
to lock onto objects which protrude and, hence, destroy the
permanent and fixed position on their mount using silicon. This is
something that occurred not once but twice during the first marathon
attempt and was resolved during the second marathon attempt by their
complete removal from the strap lugs.
On one occasion, the
accidental locking between camera strap and protruding object was so
vigorous that the camera was completely dislodged from the
constructed mount (another restart!).
A
subtle consideration also worthy of mention is the change in time
each spring and fall where clocks are adjusted backward or forward
by one hour. I have (almost) consistently worked in UT format during
the 21-months duration of this exercise so as to avoid any confusion
and, more importantly, yet another set of restarts.
This did not
prevent me, however, during late April/2002 from shooting an hour
early the analemmas at 06:00:00 UT and 07:00:00 UT when my mind
was working with the local time in effect prior to the time change a
few weeks earlier. This is something that would occur once again in
mid-October/2002 when the analemma at 09:00:00 UT was taken with
the camera for the 08:00:00 UT analemma due to a similar confusion.
These three images of the sun have been removed digitally and,
fortunately, did not adversely affect the final images for these
analemmas as a result of overlapping solar disks. The analemma
of 07:00:00 UT and 08:00:00 UT were however restarted in 2003 and these are these last images that are reproduced
on this page.
Last
chapter
The
weather factor
|