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  {
   "cell_type": "markdown",
   "source": [
    "Computing the true position of the Sun\n",
    "======================================"
   ],
   "metadata": {}
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "source": [
    "# Imports\n",
    "\n",
    "from kanon.calendars import Calendar, Date\n",
    "from kanon.tables import HTable\n",
    "from kanon.units import Sexagesimal\n",
    "from kanon.units.precision import set_precision, TruncatureMode\n",
    "import astropy.units as u"
   ],
   "outputs": [],
   "metadata": {}
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "source": [
    "# 3rd of July 1327\n",
    "\n",
    "year = 1327\n",
    "month = 7\n",
    "day = 3"
   ],
   "outputs": [],
   "metadata": {
    "tags": [
     "parameters"
    ]
   }
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "source": [
    "# Day computation\n",
    "\n",
    "# We're using the Julian A.D. calendar\n",
    "\n",
    "calendar = Calendar.registry[\"Julian A.D.\"]\n",
    "date = Date(calendar, (year, month, day))\n",
    "\n",
    "# We need to express the numbers of days from the start of the calendar\n",
    "# in Sexagesimal representation.\n",
    "\n",
    "days = Sexagesimal.from_int(int(date.days_from_epoch()))\n",
    "\n",
    "days"
   ],
   "outputs": [],
   "metadata": {}
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "source": [
    "# Defining a function resolving a position from a mean motion table\n",
    "\n",
    "def position_from_table(tab, radix, zodiac_offset=4):\n",
    "    # Starting with the radix\n",
    "\n",
    "    result = radix * u.degree\n",
    "\n",
    "    # Adding days\n",
    "    for i, v in enumerate(days[:]):\n",
    "        result += tab.get(v) >> i + zodiac_offset\n",
    "\n",
    "    # Conversion in degrees modulo 6 zodiacal signs\n",
    "\n",
    "    result %= Sexagesimal(6, 0) * u.degree\n",
    "    return result"
   ],
   "outputs": [],
   "metadata": {}
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "source": [
    "# Sun mean position\n",
    "\n",
    "# Reading the table from DISHAS\n",
    "tab_mean_motion = HTable.read(193)\n",
    "tab_mean_motion"
   ],
   "outputs": [],
   "metadata": {}
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "source": [
    "# Mean position from days, table, and radix\n",
    "\n",
    "mean_sun_pos = position_from_table(tab_mean_motion, Sexagesimal(\"4,38;21,0,30,28\"))\n",
    "mean_sun_pos"
   ],
   "outputs": [],
   "metadata": {}
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "source": [
    "# Fixed stars\n",
    "\n",
    "tab_fixed_stars = HTable.read(236)\n",
    "\n",
    "mean_fixed_star_pos = position_from_table(tab_fixed_stars, Sexagesimal(0))\n",
    "mean_fixed_star_pos"
   ],
   "outputs": [],
   "metadata": {}
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "source": [
    "# Access and recess position\n",
    "\n",
    "tab_access_recess = HTable.read(237)\n",
    "\n",
    "access_recess_pos = position_from_table(\n",
    "    tab_access_recess, Sexagesimal(\"5,59;12,34\"), zodiac_offset=2\n",
    ")\n",
    "access_recess_pos"
   ],
   "outputs": [],
   "metadata": {}
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "source": [
    "# Access and recess equation\n",
    "\n",
    "tab_eq_access_recess = HTable.read(238)\n",
    "\n",
    "with set_precision(tmode=TruncatureMode.ROUND):\n",
    "    eq_access_recess = tab_eq_access_recess.get(access_recess_pos)\n",
    "eq_access_recess"
   ],
   "outputs": [],
   "metadata": {}
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "source": [
    "# Sun apogee\n",
    "\n",
    "with set_precision(tmode=TruncatureMode.ROUND):\n",
    "    solar_apogee_pos = (\n",
    "        mean_fixed_star_pos + eq_access_recess + Sexagesimal(\"1,11;25,23\") * u.degree\n",
    "    )\n",
    "solar_apogee_pos"
   ],
   "outputs": [],
   "metadata": {}
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "source": [
    "# Sun mean argument\n",
    "\n",
    "with set_precision(tmode=TruncatureMode.ROUND):\n",
    "    mean_arg_sun = mean_sun_pos - solar_apogee_pos\n",
    "    if mean_arg_sun < 0:\n",
    "        mean_arg_sun += 360\n",
    "mean_arg_sun"
   ],
   "outputs": [],
   "metadata": {}
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "source": [
    "# Sun equation\n",
    "\n",
    "tab_eq_sun = HTable.read(19)\n",
    "with set_precision(tmode=TruncatureMode.ROUND):\n",
    "    eq_sun = tab_eq_sun.get(mean_arg_sun)\n",
    "eq_sun"
   ],
   "outputs": [],
   "metadata": {}
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "source": [
    "# Sun true position\n",
    "\n",
    "with set_precision(pmode=2, tmode=TruncatureMode.ROUND):\n",
    "    true_pos_sun = mean_sun_pos - eq_sun\n",
    "    if true_pos_sun < 0:\n",
    "        true_pos_sun += 360\n",
    "true_pos_sun"
   ],
   "outputs": [],
   "metadata": {}
  }
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