The original Merlin navigation computer, sold from 1984 to 1988, was a Sharp EL-512 calculator. It was (is) a tiny computer: just 128 steps. I programmed it with a sun almanac and an Aries almanac along with the sight reduction. To save space, instead of putting in the month and year, you have to store two special numbers: the YM number into memory (9) and the (8) number into memory (8). Click on the Word file at the bottom of this page for the numbers until the year 2030.
For stars you also need the coordinates of the star observed. They don't change much and I gave the coordinates for 59 stars in Annex B of the instruction manual every six months till the year 2000 - which seemed in those days to be in the distant future.
You could update the star coordinates of Annex B by extrapolating for the star required. Strictly speaking, it should be done on an annual basis, rather than six-monthly. For example if you require the SHA for July 2008 look back over three or four years' July figures for that star to see the annual change and project it forward. Easier would be to photocopy any near-current page from the current Nautical Almanac and convert the dec and SHA to decimal degrees with the DEG key when you enter them into the memories.
2020 Update: The declinations and SHAs for 2020 are listed below. I got them from "The Nautical Almanac." I will see if I can get some long-term numbers.
| JF00 | -10.0 | JF04 | -9.2 | JF08 | -8.4 | JF12 | -7.6 | JF16 | -6.8 | JF20 | -6.0 |
| 2000 | +14.0 | 2004 | +14.8 | 2008 | +15.6 | 2012 | +16.4 | 2016 | +17.2 | 2020 | +18.0 |
| 01 | +8.2 | 05 | +9.0 | 09 | +9.8 | 13 | +10.6 | 17 | +11.4 | 21 | +12.2 |
| 02 | +2.4 | 06 | +3.2 | 10 | +4.0 | 14 | +4.8 | 18 | +5.6 | 22 | +6.4 |
| 03 | -3.4 | 07 | -2.6 | 11 | -1.8 | 15 | -1.0 | 19 | -0.2 | 23 | +0.6 |
That perpetual almanac is actually a 1990 almanac and the year adjustment brings it up to date. Random checks in 2015 and 2020 show this adjustment still working: worst error found was 1'.8 and most were under 1'.
It is, of course, superfluous if you have the genuine Merlin sun program (i.e., program [2:]) in the Sharp EL-512.
Here are declinations and SHAs for 2020 in decimal degrees. I have taken these from The Nautical Almanacwhere ther almanac information may be found.
|
|
Decl | Decl | Decl |
|
|
SHA | SHA | SHA |
|
|
Jan 1 20 | July 1 20 | Jan 1 21 |
|
|
Jan 1 20 | July 1 20 | Jan 1 21 |
| acamar | -40.23 | -40.222 | -40.226 |
|
acamar | 315.244 | 315.248 | 315.234 |
| achernar | -57.142 | -57.13 | -57.137 |
|
achernar | 335.387 | 335.388 | 335.377 |
| acrux | -63.203 | -63.215 | -63.209 |
|
acrux | 173.072 | 173.067 | 173.059 |
| adhara | -29 | -29.001 | -29.001 |
|
adhara | 255.144 | 255.152 | 255.134 |
| albireo | 28.003 | 28.003 | 28.004 |
|
albireo | 67.127 | 67.11 | 67.117 |
| aldebaran | 16.547 | 16.548 | 16.55 |
|
aldebaran | 290.732 | 290.735 | 290.718 |
| alioth | 55.849 | 55.856 | 55.843 |
|
alioth | 166.28 | 166.272 | 166.268 |
| alkaid | 49.212 | 49.218 | 49.206 |
|
alkaid | 152.924 | 152.914 | 152.914 |
| almak | 42.426 | 42.422 | 42.431 |
|
almak | 328.718 | 328.717 | 328.703 |
| al nair | -46.868 | -46.859 | -46.864 |
|
al nair | 27.64 | 27.622 | 27.623 |
| alnilam | -1.192 | -1.19 | -1.19 |
|
alnilam | 275.691 | 275.696 | 275.679 |
| alphard | -8.745 | -8.747 | -8.749 |
|
alphard | 217.857 | 217.86 | 217.845 |
| alphecca | 26.648 | 26.65 | 26.644 |
|
alphecca | 126.124 | 126.11 | 126.113 |
| alpheratz | 29.201 | 29.199 | 29.207 |
|
alpheratz | 357.648 | 357.641 | 357.636 |
| altair | 8.922 | 8.923 | 8.924 |
|
altair | 62.07 | 62.053 | 62.057 |
| ankaa | -42.204 | -42.193 | -42.198 |
|
ankaa | 353.188 | 353.181 | 353.175 |
| antares | -26.473 | -26.476 | -26.475 |
|
antares | 112.351 | 112.333 | 112.336 |
| arcturus | 19.079 | 19.08 | 19.073 |
|
arcturus | 145.863 | 145.852 | 145.851 |
| atria | -69.058 | -69.064 | -69.061 |
|
atria | 107.323 | 107.282 | 107.297 |
| avior | 59.572 | -59.577 | -59.574 |
|
avior | 234.26 | 234.278 | 234.256 |
| bellatrix | 6.365 | 6.366 | 6.367 |
|
bellatrix | 278.448 | 278.452 | 278.434 |
| betelgeu. | 7.408 | 7.409 | 7.409 |
|
betelgeu. | 270.935 | 270.94 | 270.921 |
| canopus | -52.708 | -52.707 | -52.708 |
|
canopus | 263.893 | 263.909 | 263.888 |
| capella | 46.017 | 46.015 | 46.018 |
|
capella | 280.456 | 280.462 | 280.437 |
| castor | 31.842 | 31.844 | 31.841 |
|
castor | 246.03 | 246.035 | 246.014 |
| cor caroli | 38.209 | 38.214 | 38.203 |
|
cor caroli | 165.764 | 165.757 | 165.752 |
| deneb | 45.354 | 45.351 | 45.357 |
|
deneb | 49.481 | 49.463 | 49.473 |
| denebola | 14.46 | 14.461 | 14.455 |
|
denebola | 182.483 | 182.479 | 182.47 |
| diphda | -17.881 | -17.874 | -17.875 |
|
diphda | 348.856 | 348.85 | 348.843 |
| dubhe | 61.639 | 61.646 | 61.634 |
|
dubhe | 193.764 | 193.765 | 193.747 |
| elnath | 28.622 | 28.622 | 28.624 |
|
elnath | 278.11 | 278.114 | 278.094 |
| eltanin | 51.487 | 51.488 | 51.486 |
|
eltanin | 90.743 | 90.722 | 90.737 |
| enif | 9.967 | 9.968 | 9.971 |
|
enif | 33.716 | 33.702 | 33.704 |
| fomalhaut | -29.52 | -29.512 | -29.515 |
|
fomalhaut | 15.32 | 15.307 | 15.306 |
| gacrux | -57.218 | -57.23 | -57.224 |
|
gacrux | 171.932 | 171.926 | 171.919 |
| gienah | -17.65 | -17.655 | -17.655 |
|
gienah | 175.794 | 175.789 | 175.782 |
| hadar | -60.462 | -60.474 | -60.467 |
|
hadar | 148.696 | 148.679 | 148.679 |
| hamal | 23.556 | 23.555 | 23.561 |
|
hamal | 327.926 | 327.924 | 327.912 |
| kaus aust. | -34.373 | -34.373 | -34.373 |
|
kaus aust. | 83.638 | 83.616 | 83.621 |
| kochab | 74.071 | 74.078 | 74.066 |
|
kochab | 137.345 | 137.321 | 137.344 |
| markab | 15.313 | 15.313 | 15.318 |
|
markab | 13.567 | 13.556 | 13.554 |
| menkar | 4.165 | 4.168 | 4.17 |
|
menkar | 314.169 | 314.169 | 314.156 |
| menkent | -36.463 | -36.471 | -36.468 |
|
menkent | 148.04 | 148.028 | 148.026 |
| merak | 56.272 | 56.278 | 56.267 |
|
merak | 194.243 | 194.243 | 194.227 |
| miaplacidus | -69.795 | -69.804 | -69.799 |
|
miaplacidus | 221.633 | 221.658 | 221.632 |
| mirfak | 49.932 | 49.928 | 49.936 |
|
mirfak | 308.559 | 308.563 | 308.542 |
| mizar | 54.818 | 54.825 | 54.813 |
|
mizar | 158.825 | 158.815 | 158.813 |
| nunki | -26.271 | -26.269 | -26.27 |
|
nunki | 75.885 | 75.865 | 75.87 |
| peacock | -56.672 | -56.666 | -56.67 |
|
peacock | 53.212 | 53.184 | 53.191 |
| phact | -34.066 | -34.064 | -34.065 |
|
phact | 274.903 | 274.912 | 274.894 |
| pollux | 27.976 | 27.977 | 27.974 |
|
pollux | 243.364 | 243.369 | 243.349 |
| procyon | 5.172 | 5.172 | 5.17 |
|
procyon | 244.912 | 244.916 | 244.899 |
| rasalhague | 12.547 | 12.547 | 12.545 |
|
rasalhague | 96.044 | 96.027 | 96.032 |
| regulus | 11.869 | 11.869 | 11.864 |
|
regulus | 207.642 | 207.643 | 207.629 |
| rigel | -8.181 | -8.179 | -8.18 |
|
rigel | 281.124 | 281.128 | 281.111 |
| saiph | -9.665 | -9.663 | -9.664 |
|
saiph | 272.822 | 272.827 | 272.81 |
| schedar | 56.649 | 56.643 | 56.655 |
|
schedar | 349.59 | 349.584 | 349.577 |
| scheddi | -16.038 | -16.033 | -16.034 |
|
scheddi | 32.973 | 32.958 | 32.959 |
| shaula | -37.115 | -37.117 | -37.117 |
|
shaula | 96.27 | 96.248 | 96.253 |
| sirius | -16.745 | -16.745 | -16.746 |
|
sirius | 258.49 | 258.497 | 258.479 |
| spica | -11.263 | -11.267 | -11.268 |
|
spica | 158.443 | 158.434 | 158.43 |
| suhail | -43.511 | -43.517 | -43.514 |
|
suhail | 222.813 | 222.821 | 222.805 |
| vega | 38.803 | 38.804 | 38.803 |
|
vega | 80.606 | 80.588 | 80.598 |
| polaris | 89.351 | 89.344 | 89.356 |
|
polaris | 315.546 | 315.974 | 315.235 |