Map of Eniwetok Showing Locations of Observing Ships The four observing chire of Joint Task Force SEVEN, the U.5.5, Albemarle, the U.o.c, Badroko, the 0.5.5, Curties, and the U.5.5. Ut. heKinley, were anchored in the same anchorages during the three tests, The difference in the resnective pocitions of the ehipa for ooch teat did not wary moh more than a ship's length, The bows of the ships cere headed into the easterly trode winds op that theodolites vere set up on the port cide, jJith the constant wind and etill eater of the lngean, the ahipa did not swing sore than a few degrees during any purtisular set of obeervetions and the deok wes elnoct as steady as firm groaed. Only one distanoe for each teat bas been used for #1] four ships. “han the distances of the test si were mecsured from each ship, it mas found that ff Practinal purnoses ubole miles, rather than miles «nd fractions of niles, would give mufficietly accurate results, Proper distance ie an isportant comeideration when waking seteorological obeervations of atomlo phencnena, On XMAT Dey, cith the test site at Bagebi, the island was below the horizon; and nothing could be seen below the topo of the cumdus alouds which vere in the vicioity of the taet alte. Qo TORE Day, dohon was just on the horteon but because of dorkmess ami the email cum- lua cloude 1¢ sae pot possible to repert surface phenop- one near the test site with assurance. On ZEBRA Iny, Runit sas easily sean when light wes evallable, The flood livhta near the baee of the tocer were in plain view before li-hour, At the distance of 9 miles the banus of the cumulus clouds acpenred well above the horizon eo thot it qua pot difficult to see beneath them, For observations of surface or low altitude phencsena the shorter distances cro wefernhle; however, for the checrvation of cloude after they reach maxime altitude the longer distances are preferred. If the cloud io pear, of mms the ZEBRA Tey cloud, it is not possible to sight on the top of the highest part. Theololites must be aimed tormmm the undernasth side of the cloud. Perhaps the optiaum dintence for general observiticn fron the surface ta near 12 ofiles, Tt should bw noted that all distances used Ln this report are nautical ailes. ue) o Nautical Miles ' 2 3 4 . Bairoko 5 So , Ibemarle . Curtiss . Mt. Mc Kinley 7 Eniwetok Is. Ath regurd to orlentation, the positions of the ahins were very favormbly locuted vith reapast to the vnrer cinda, The elou! material eoved off to tha east and weot frou the test sites so that it was in sight about threeree hour forroret hours, and there mas 6 sini of