ROYAL ASTRONOMICAL SOCIETY OF CANADA
Standing Committee on Observational Activities
Programme for Solar Eclispe of July 20, 1963
Bulletin No. 5 Basic Observation Programme May 4, 1963
Section C. Visual Observations
This section of the basic observation programme covers visual observations made
during the total phase either with the naked eye or with telescopic aid and with the
emphasis on drawings or sketches, supplemented by verbal descriptions of detail seen.
Dark Adaptation. It is common knowledge that our ability to see dim light is pro-
portional to the length of tame that the "rod" cells of the eye's retina remain
unstimulated. To see fine detail during the brief period of totality, the eye must
first become dark adapted, a process that takes at least twenty minutes. The gradual
darkening of the sky during the partial phase is not sufficient to produce the des-
ired effect, and the following methods of dark adaptation are suggested,
(1) The observer is blindfolded during the approach of totality. This rather drastic
measure deprives him of the thrill of seeing the sudden transition front partial
to total phase when the corona shines forth in all its beauty True, he can
watch the end of totality and the subsequent partial phase but it is not as
spectacular as the approach.
(2) The observer can wear dark red goggles during the approach of totality, for it
has been told that the rods are practically unstimulated by the red end of
the spectrum. This method shows activity during the period of adaptation.
Care must still be taken to provide adequate protection for the eyes when
looking directly at the sun.
(3) The observer can wear a black patch over his "observing" eye, watching the
approach of totality with the other and removing the patch only after the
beginning of totality. This method is particularly, suitable for those making
telescopic observations for most observer invariably use the same eye at the
Regardless of the number of photographs taken, visual observations of the solar
corona will be useful, for the human eye, if properly dark adapted, can see fine
detail that is difficult to photograph without over-exposing other areas. The
problem, of course, in making visual observations is to record faithfully the detail
that one sees - the shape and extent of the corona, the variations in intensity
and to do this in a very limited period of time. The observer should not trust to
memory but should complete his drawing from actual observation during the period of
totality. This is a tall order and it is suggested that the observer practise before-
hand, making drawings from projected Slides of the solar corona. For the sake of
uniformity it is suggested that a two inch circle represent the sun's disk. A verbal
description, recorded immediately after totality, should supplement the drawing.
As mentioned in Bulletin No. 4, at sun-spot minimum it is expected that the corona
will have long equatorial streamers and short polar plumes. Observations can be
made with the naked eye or with a telescope. The report form should give details of
equipment used. The telescopic observer has the disadvantage that, since no filters
are used during totality, he must be ready to stop a few seconds before the end of
totality to avoid the possibility of injury to his eyes.
2. SOLAR PROMINENCES
Drawings of solar. prominences are made in the same manner as those of the
corona except that telescopic aid is definitely required. The same care must be
taken in recording accurately all detail seen and there is the same problem in
getting this done in a limited time. In fact, if there are numerous prominences, it
may be impossible to record them all. The report should then indicate which areas
of the drawing are incomplete. For solar prominences, it is especially important
that the drawing be properly oriented.
It is suspected that daytime aurora might be visible during a total eclipse but
one has not yet been observed. In the search for aurora only naked eye observations
are required. Since this is a minimum eclipse the likelihood of auroral activity is
small but nevertheless possible. It is suggested that this observation be assigned
to an experienced aurora observer who would complete a regular aurora report form.
He must, of course, be dark adapted before totality.
4. STARS VISIBLE DURING TOTALITY
The purpose of this observation is to determine the extent to which the sky is
darkened by the eclipse and here again the need for dark adaptation is obvious.
The observer is provided with a chart showing stars dots to third magnitude in the
vicinity of the sun. Those visible during totality are noted by the observer. He
also plots the position of any fainter stars he can see. No optical aid should be
used and it is preferable to have more than one observer since some have keener
eyesight than others. For the July 20th eclipse, Venus and Mercury will be in the
vicinity of the sun. If the observer is fortunate enough to spot a comet, then he
should, concentrate on it!
5. EFFECTS ON BIRDS AND ANIMAL LIFE
As the sky darkens, the observer notes the effect this has on birds and animals
who mistake the eclipse tor nightfall. The ability to recognize various species
will, of course, be helpful. The observer should record any unusual happenings,
noting the time of each, such as the first cock crow after totality.
* * * * * * *
Eclipse Photography In Bulletin No. 4, we said that the Kodak booklet on "Solar
Eclipse Photography for the Amateur" was out of print. We have now been advised by
Eastman Kodak that they' are preparing a revised edition which should be available
by the end of this month as there may be some delay in getting our supply, it
might be quicker for you to get a copy from your nearest Kodak dealer.
Isabel K. Williamson
National Co-ordinator 1963 Eclipse
5162 Belmore Avenue
Montreal 29, Que.
Wednesday, August 5, 2015 - 6:11am
Bulletin 5: Dark Adaptation, Corona, etc.