AEROGRAPHER'S MATE 3 & 2 



the height of the cloud above the observer. 

 This height must then be corrected by an 

 amount equal to the difference in elevation 

 of the point of observation and the field elevation 

 or ground. For convenience, a table of heights 

 plotted against observed elevation angles should 

 be made up for use of the observer. 



Maintenance 



When the clinometer is not in use, keep 

 it in its case to protect the instrument from 

 dust and dirt. Keep the pendant clamped to 

 prevent it from being damaged by sudden 

 movements or jolts. The clinometer is dusted, 

 when necessary, with a clean soft cloth. 



Check the clinometer monthly for accuracy 

 in the following manner: 



With the sighting tube in a horizontal position, 

 rest the front edge of the quadrant scale 

 plate on a level surface. The pendant should 

 indicate 0°. If the instrument does not register 

 accurately, return it for repair in accordance 

 with current instructions. 



CLINOMETER ML-591/U 

 (SHIPBOARD TYPE) 



This clinometer is designed for shipboard 

 use only. It is used for measuring the elevation 

 angle of a spot of light thrown on the base 

 of a cloud by a ceiling light projector or 

 searchlight in the same manner as the ML-119 

 previously mentioned, with minor exceptions. 

 This instrument will usually be permanently 

 mounted and will require periodic orientation. 



Description 



Clinometer ML-591/U is composed of a 

 sighting tube attached to a quadrant plate, 

 an angle scale, a pendant, a pendant lock stud 

 assembly, a pendant clutch assembly, a mount- 

 ing bracket, and a mounting bracket base. 

 (See fig. 5-6.) 



The entire surface of the sighting tube 

 and quadrant plate is dull black anodized. 

 The sighting tube is bottle-shaped with 

 a l/4-inch diameter peep sight in the small 

 end and cross wires in the large (3-inch 

 diameter) end. The angle scale and pendant are 

 engraved, dull black anodized and white filled. 

 The quadrant plate and pendant are attached 

 to the mounting bracket with the pendant lock 



SIGHTING TUBE 



209.112 

 Figure 5-6. — Clinometer ML-591/U (shipboard 

 type) with cover. 



stud assembly. The pendant is secured in the 

 desired position with the pendant clutch as- 

 sembly. The mounting bracket fits into the 

 mounting bracket base and is held at the desired 

 height and heading with a phenolic resin 

 laminated insert in the knurled hand knob. 

 The mounting bracket base is secured to the 

 ship by a pipe welded to the deck. The location 

 of the clinometer should be out of the glare 

 of lights when making a sight. When not in 

 use, the clinometer is covered with a coated 

 nylon bag (fig. 5-6) which is drawn tight around 

 the bottom with a nylon drawstring. 



Orientation 



With the clinometer ML-591/U mounted 

 on the support described above and tightened 

 handtight, in a vertical fixed position (plus 

 or minus 2 degrees), 4 feet above the deck, 



84 



