82 



UNITED STATES COAST GUARD 



The following 3 sextant altitudes of 

 the moon were obtained. The height of 

 eye was 61 feet and the sextant index 



error was 2'.5 on the arc in all observa- 

 tions. Given : 



Observation No. 1 



Moon sext. alt 6°-17'.8 



Bar. Pressure 29.2 in. 



Temperature 51° F. 



Hor. Parallax 55'.5 



Required: The observed altitudes. 



The following 3 sextant altitudes of 

 planets were obtained on 6 February 

 1958. The height of eye was 18 feet, the 



Saturn 

 Observation No. 



Planet sext. alt 7'-56'.7 



Bar. Pressure 29.0 in. 



Temperature (— ) 5° F. 



Required: The observed altitudes. 



sextant index error was 2'.5 off the arc 

 in all observations. Given : 



Jupiter 

 Observation No. 2 



15°-37'.9 

 1000 mb. 

 33° Celsius 

 (Centigrade) 



Ve^xus 

 Observation No. 3 



21°-17'.7 

 30.0 in. 

 52° F. 



5. CHART NAVIGATION. 



What chart would you use to locate 

 the earth's magnetic equator? 



A vessel at 60° South Latitude is 300 

 miles due West of a radio beacon. Deter- 

 mine graphically, by use of the con- 

 version angle f oi-mula : 



conversion angle = % difference 

 longitude X sine Middle Latitude or by 

 table, the bearing that would be ob- 

 tained by the use of a radio direction 

 finder. 



When a scale is given for a Mercator 

 chart, to what part of the chart is it 

 generally applicable? 



How is distance measured on a poly- 

 conic chart? 



Make a rough sketch sho^ving how 

 the charted island with contours in- 

 dicated would appear at positions "A" 

 and "B" in profile. 



(contour interval — 200 feet) 



^ ••»• 



The distance between two points on 

 a polyconic chart of the Great Lakes is 

 100 statute miles. How long would it 

 take a vessel making 15 knots to tra- 

 verse the distance? 



Describe how you use a gnomonic 

 chart to determine a composite Great 

 Circle Track with a limiting latitude. 



Name the type of Gnomonic Chart 

 sketched. 



* "A" 





