THE ASTRO COMPASS
Here is a PDF file that on a couple of pages shows how to use the astro compass to determine true north, and examples are
given. Two methods are shown.

The          
 illustratingShadows.xls           spreadsheet (in the zip file to the left) supports the second method. The astro compass
                                                           can also be used to tell the time accurately, being a variation of the armillary dial.

A
quick stand alone spreadsheet for the Astro Compass is here, in Excel form, works in Open Office.  The best spreadsheet is my
main one however, see
Excel  page.  

CLICK
HERE for the astro compass notes.   [NOTE: the examples are set in New Mexico and AZ, USA as regards longitude]
I have had these things on and off since I was a late teen, as well as bubble and fixed horizon sextants, and almost anything that
came out of world war 2 ships and planes. They can be found on Ebay fairly easily for less than $100, and these notes tell you
how to use it, and tell how to make the mount out of a bit of PVC pipe. Without that mount, the levelling system will not work.    I
have Excel sheets for the PC as well as Documents To Go to facilitate astro compass usage.

Anyhow, after you have seen some of these articles on this web site, you may want to purchase the book itself, Illustrating Time's
Shadow  (printed, or online download)     
buy here!
Hour of day from 0600 to 1800 converted to degrees
STANDARD TIME (not summer time)
6   7   8   9   10  11  12  13  14  15  16  17
mins
0     270 285 300 315 330 345  0  15  30  45  60  75
4     271 286 301 316 331 346  1  16  31  46  61  76
8     272 287 302 317 332 347  2  17  32  47  62  77
12    273 288 303 318 333 348  3  18  33  48  63  78
16    274 289 304 319 334 349  4  19  34  49  64  79
20    275 290 305 320 335 350  5  20  35  50  65  80
24    276 291 306 321 336 351  6  21  36  51  66  81
28    277 292 307 322 337 352  7  22  37  52  67  82
32    278 293 308 323 338 353  8  23  38  53  68  83
36    279 294 309 324 339 354  9  24  39  54  69  84
40    280 295 310 325 340 355 10  25  40  55  70  85
44    281 296 311 326 341 356 11  26  41  56  71  86
48    282 297 312 327 342 357 12  27  42  57  72  87
52    283 298 313 328 343 358 13  28  43  58  73  88
56    284 299 314 329 344 359 14  29  44  59  74  89
60    285 300 315 330 345 360 15  30  45  60  75  90

This table comes from a spreadsheet which allows you to
adjust the astro compass hour angle for longitude and EOT.
The
master spreadsheet (Excel)has this and other valuable
sheets. There is also a version specifically for the Palm
Pilot.

Only two adjustments (which the main spreadsheet does for
you), one is to correct for longitude offset from the
standard time meridian, the other is the EOT.