Project Blue Book File on Tremonton Film, Utah, 1952

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Photogramnetric
-5-
Serial 00
Ana.lysia ot HUtah" Film
Certain soaring insects - notably "ballooning spiders" (reference (5)
and (6)) produce bright moving points of' light. The author has witnessed
such a phenomenon. It is produced by sun reflections ott tbe streamers of
silken threads spun by many types ot spiders. Caught by the wind, these
streamers serve as a means ot lecanotion floating the spider high into the
air. They oocaeionally have the appearance of vast numbers of silken tlakes
which till the air and 1n some recorded instances extend over many square
miles and to a height of several hundred feet. The reflection, being off
silk threads, is not as bright as ditruse reflection h-om a flat white
board. Thus no :t'laring ot the images could be expected. The author noted
that the sections at the "web" that reflected measured f'ran 1/411 to 1/211
tor the largest specimenS. Thus the images might be ttributed_to balloon­
iIJg spiders at distances ot 50 to 100 feet. However, these web ref'lections
ordinar1]3 show up~ against a rather dark background and it is doubted
U their intensity would be great enough to produce the intense UFO images
against a bright sq.
No quantitative densitaneter examination at image brightness could be
made, as the
film was
available.
is understood
Al
original
not
It
from
Chop
that the gOYermnent analysts did make measurements ot this kind on the
original films and touud the Utah images to be very intense*•
Besides the above remarks, pertinent to the actual. images, several
tacts can be gleaned trcm the motion of objects. The observations are not
apt to support the supposition that the objects were cOIIVentional a1rcra1"t
as the maneUTers are too erratic, the relative accelerations probably rul­
ing out aircraft at distances ot aver five miles. Several observers familiar
with the appearance of chatt have seen the
and concluded that the per­
film
sistence of the nontwinkHng oonstellationa, their small quantity, and the
reported absence ot aircratt overhead makes chatt unl.ikely. Furthermore,
the single object passing across the tield. or view would be most d.1.tticult
to explain on the basis or chatt. These same remarks would apply also to
bits of paper swept up in thermal updrafts.
The relative angular velocity might be canpatible with soaring bird
speeds at distances at less than one mile, the angular velocity ot the
single objeot coul.d be attributed to a bird within about one thousand feet.
There is a tendency to pan With a movillg object - not against it - so the
Telocities in the table probably represent a lower bound.
The motion of
the obJects is not exact~ what one would eJr:pect tran a f'latlt of soaring
birds (not the slightest indieation of a decrease in brightness due to
periodic turning with the Wind or f'lapping) and no cumulus clouds are present
which might betray the presence of a strong thermal updratt.
On the other
hand the s1Dgle object might represent a single soaring bird Which broke away
in search of a new thermal -- quite a ccmnon oocrurrence among gulls -­
see reference (7).
*
In tact, "burned right down to the cellu1oid baokiDg".
See also
ref'erence (l).
DECLASSIFIED Authority NND 923007