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Byron: Class Notes for Seamen’s Church Institute of Newport RI.
The Placement of the SUN on the 2 minute STAR FINDER may be
from many sources GHA, DECLINATION, NEWSPAPER ect.
This example I will use the DEC.for AUG.30. DEC is 9 Degrees North (from HO.71)
you can draw (degrees above the EQUATOR, or subtract (from 90 for 81 CO-DEC.
Swing an ARC that represents the AUG 30 SUN path across your SKY (on the 45 LATITUDE DISK.)
You first placed the LAT DISK on the BASE DISK to represent SKY. Swing an ARC that represents the AUG 30 SUN path across your SKY (on the 45 LATITUDE DISK.)
You again have a choice; you may use Local time if you put the LAT DISK at the Greenwich
zero plus your difference in LONG. Or use GMT if you place the LAT DISK on your known LONG.
With the DEC ARC in place, you can (closely) find SUNRISE/SUNSET or any time ZN/ALT between.
Draw any line from the POLE to the RIM GMT to read off GMT/ZN/or ALT.
EXAMPLE: SUNRISE for 45N/75W AUG 30 off the outer RIM, 10:28 ZN080(HO 71=05:24 ZN77
2- 12:26 099/20 3- 1408 ZN120/39 4-16:177/55 5- 19:44 262/ 43 6 21:40 262/19 7 23:24 281/ Set
True the readings off the 2 MINUTE are approximant, but close and are used for planning and visual training.
Try you self. Print the 2 Minute, draw a new line and see how close you can be to compute GMT, ZN&ALT.
I use the central Zone for example, but you use the actual Longitude the Star Finder can also be set for other than even 10 LAT such as 41N.

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