630406Eclipse4_p2

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Eclipse Bulletin No. 4 cont'd.

PHOTOGRAPHIC PROJECTS	

Still Photographs.

1. PARTIAL PHASES, BAILY'S BEADS, etc.

       For the partial phases a camera With a lens of long focal length should be
   used with fineÄgrain film and dense neutral filter. (See enclosed KODAK EXPOSURE
   TABLE). With the correct exposure,. the rest of the sky will remain dark on the
   film, If the camera to be used has a moderately wide field, say. 20 or 30 degrees,
   then it need not be moved for half the duration of the eclipse. If an exposure is
   made, say, every five minutes, then the motion of tie earth will carry the image
   of the sun to a new position on the film for tch exposure and when printed the
   photograph win show the progress of the eclipse as a row of images of the sun.
   Done in two lots, one photograph will shOw the progress of the moon onto the sun's
   disk and the second will show its egress. Note that the sun moves 15 degrees per
   hour across the sky.

   The surface of the moon being mountainous, its outline is in some places irreg-
   ular and hence it is possible for some light from the intensely bright edge of the
   sun to shine through a Lunar valley at the rim of the lunar disk, and this gives
   a flood of intense light at some point or points around the rim, causing the phen-
   omena of Baily' s Beads and the "diamond ring" effect immediately befote and after
   totality, Because of their short uration, the observer has to be alert to get
   still photographs of these effects.

   Note Do not attempt to record the diamond ring the corona, or both preceding
   following dianwnd ring effects, on one negative with a stationary camera.
   Totality is short and the images are …ertaih to overlap. Therefore., use separate
   cameras or wind the film just after the beginning of totality and re-aim the camera.

2. TOTALITY

   (a) Corona - shape. Direct photography of the corona, although one of the sinplest
   observations, is probably the mo-st interesting, aixt it has been pointed out to us
   that here is -a good opportunity -for the amateur to make a useful contribution.
   "The corona at every eclipse is different and it is important to have a record of.
   each one. Since the probability for cloudy weather along the 1963 eclipse path is
   high, it rqay be that amateurs distributed well along the path will be the only
   ones to record it In addition to long-term changes of tie corona, rapid changes
   in shape and position-of coronal streamers (most easily seen at minimal eclipses
   such as the 1963 one) have been detected at previous, eclipses. It is therefore
   interesting to. compare coronal ph2tographE of. the same eclipse taken at widely
   separated stations along the path."

   Photography of the corona requires that the camera have a clock-driven or
   guided mount. Because of the extreme range of brightness between inner and outer
   corona, the latter cannot be photographed well without ever-exposing the former.
   (See enclosed KODAK EXPOSURE TABLE.) A rotating sector shutter centred over the
   image in front of the film will help equalize the exposure. So will a small disk 
   placed part way between film. and lens, but placing this will take some experiment-
   ing ahead of time. With an ordinary camera it is best to use film for high con-
   trast subjects. Best records of detail will be secured by photographing through
   telescope or binoculars to obtain a very long focal length.

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