Scientific Study of Unidentified Flying Objects (the Condon Report, complete, three volumes)

(i\lenzel and Boyd, 1963), A valuable treatise on atmospheric effects on
seeing is Hiddleton t s ('/:sicm thl'OIA.gh the .4 tmosphere (1952). A survey
of the literature of atmospheric optics with emphasis on topics relevant
to und(~rstanding UFO reports was prepared for the Colorado project by
Or. Williwn Viezce of the Stanford Research Institute (Section VI,
Chapter 4).
Coming to the observer himself, ~,~en'!,0l stressed; n consulting
visi ts to the Colorado project that mol',· ought to be known about defects
of vision of the observer. lie urged careful interviews to determine
the observer'~ defects of vision, how well they are corrected, and
whether spectacles were being worn at the time the UFO sighting wa.-:
made. Besides the defects of vision that can De correctec by specta-·
cles, inquiry ought to be made wh:;'>Y'e relevant into the degree of color
blindness of th~ observer, since this visu.l defect is ~0re common
than is gr.::lerally appreciated.
Problems connected wi th thr psychology cf percerJtion were s tudi ed
for the Colorado project by Prof. Midlael Wertheimer of the Department
of Psychology 0f the University of Color'4do. lie prepared a'1 elemeT'tary
pre5entation of the main poiT'ts of interest fOT the use of the project
staff (Section VI, Chapter 1).
Perhaps the ·;ommonest difficulty is the lack of appreciat~')n of
size-distwce relation$ in the c.1escri}Jtion of an unknown object. When
we see an :Ii rpl ane in the ::;"Y, especially if it is one of a. parti cul ar
model with which we aT(' familiar, we know from prior experience approxi-
mately what its size really is. 1110n from its arrarent size as we 3ee
it, we have some basis for estimating its Llistance. CCJnversely, when
\\'C kno..... something about th,- distance of all unknown obje~t, we can say
50mething about its s i Zl.'. A] though not usual l)" cxprcss("ll thi~ way,
\\hat is rpally Its cen" is the s i.:e of the illla~l' im the t't'ti lIa rtf the
eye, whidl may be' proJuced by e~~pite this elementary fact,
many (J('ople persbt in saying that the full moon look~ the same size a.s
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