pointer there is a viewing lens 25 vertically oriented to the reference line as shown in fig1 and 2 the other end of the pointer carries the declination slider assembly 26 oriented parallel to the viewing lens also shown in fig1 and 2 the declination slider assembly 26 has an angular scale 28 calibrated in 0 5 degree increments the scale has a central slot 30 bisecting the markings and aligned with the reference line 27 fig4 shows the slider 31 which is movably mounted in the slot 30 the slider is connected to set screws 32 and 33 the loosened screws may move throughout the length of the slot 30 and may temporarily fix the slider in place by tightening the screws while screws are shown and described other fastening devices providing releasable fixation may be used in the slider assembly such as studs having rotatable oblong shafts for frictional engagement of the walls of the slot or slidable clips slidably movable to engage and release the lateral edges of the slider assembly fig5 shows the face 34 of the transparent slider as it appears when viewed against the viewing lens 25 the center point 35 is positioned on any of the interrupted markings of the scale 28 and temporarily locked in place by the set screws 32 and 33 the viewing lens 25 in fig6 is shown with cross hairs 36 in place the intersection of the cross hairs designates the center of the viewing lens to properly align the declination slider with the viewing lens 31 this intersection must be placed in line with the center of the viewing lens cross hairs the lens has markings.