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卷二十六 志第十六 曆二

Volume 26 Treatises 17: Calendar 2

Chapter 26 of 新唐書 · New Book of Tang
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1
Under Emperor Gaozong the Wuyin calendar grew increasingly inaccurate; Li Chunfeng composed the Jiazi Origin calendar and presented it. An edict ordered the Grand Astrologer to implement it from Lindé year 2; it was called the Lindé Calendar. Ancient calendars used rules, obscurations, origins, eras, day parts, and degree parts in inconsistent units; Chunfeng unified them with a single general factor of 1,340. He revised the gnomon midday method to determine solstice arrival, built a wooden armillary to measure the ecliptic, and otherwise adapted Liu Chuo's Huangji calendar with suitable adjustments. It was then regarded as precise and was used concurrently with the Jingwei calendar that Grand Astrologer Qu Tanluo had submitted.
2
In Hongdao year 1 the twelfth month began on jiayin and ended on renchen. In the eighth month an edict fixed New Year's Day of year 2 on jiashen, so the prior month-end was advanced to guwei.
3
In Yongchang year 1, eleventh month, the era became Zaichu; the court adopted the Zhou calendar, making the twelfth month La month and the yin month the first month. In Shenggong year 2 the calendar office intercalated La month, but the moon appeared in the east on the prior year's last day; the Empress Dowager decreed that the first month become intercalary tenth month. That year, at jiazi winter solstice, the era name was changed to Shenglü. Qu Tanluo was ordered to compose the Guangzhai calendar for imminent use. In year 3 work on the Guangzhai calendar was halted and the Xia calendar restored, continuing through Kaiyuan year 16.
4
For the Lindé Calendar, Lindé year 1 jiazi stood 269,880 counts from the high origin.
5
General factor: 1,340.
6
Sequence constant: 489,428.
7
Mean new-moon constant: 39,571. Add 362 for the waxing new-moon constant; subtract 351 for the waning new-moon constant.
8
Double-hour rate: 335.
9
Multiply the accumulated count by the sequence constant to obtain the sequence total. Divide by the general factor; each quotient is one day. Cast out multiples of 60, count from beyond jiazi, and obtain winter solstice. Add cumulatively 15 days, 292 minor remainder, and 5/6 of a minor part to obtain the next qi. Multiply the minor remainder by 6, divide by the double-hour rate, and count from beyond mid-zi for each add-time.
10
滿
Cast the mean new-moon constant out of the sequence total; what remains is the intercalation remainder. Subtract the intercalation remainder from the sequence total for total proper; divide by the general factor for days. Subtract from winter solstice to obtain the mean astronomical new moon. Also add the mean new-moon minor remainder to the intercalation remainder and subtract from the sequence total for total proper. From the mean new moon add 29 days and 711 minor remainder to obtain the next new moon. From new moon add 7 days and 512 3/4 minor remainder for first quarter. Add again for full moon and last quarter.
11
Advance cord: 16. After autumn equinox.
12
退
Retreat era: 17. After spring equinox.
13
Solar terms
14
Lodging difference rate
15
Discharge-recovery total
16
Advance-retard rate
17
Wax-wane accumulation
18
Winter Solstice
19
Increase 722
20
Discharge initial
21
Advance 54
22
Wax initial
23
Lesser Cold
24
Increase 618
25
Discharge 722
26
Advance 46
27
Wax 54
28
Greater Cold
29
Increase 514
30
Discharge 1,340
31
Advance 38
32
Wax 100
33
Start of Spring
34
Increase 514
35
Discharge 1,854
36
Advance 38
37
Wax 138
38
Awakening of Insects
39
Increase 618
40
Discharge 2,368
41
Advance 46
42
Wax 176
43
Rain Water
44
Increase 722
45
Discharge 2,986
46
Advance 54
47
Wax 222
48
Spring Equinox
49
Increase 722
50
Discharge 3,708
51
Retard 54
52
Wax 276
53
Clear and Bright
54
Decrease 618
55
Discharge 2,986
56
Retard 46
57
Wax 222
58
Grain Rain
59
Decrease 514
60
Discharge 2,368
61
Retard 38
62
Wax 176
63
Start of Summer
64
Decrease 514
65
Discharge 1,854
66
Retard 38
67
Wax 138
68
滿
Lesser Full Grain
69
Decrease 618
70
Discharge 1,340
71
Retard 46
72
Wax 100
73
Grain in Ear
74
Decrease 722
75
Discharge 722
76
Retard 54
77
Wax 54
78
Summer Solstice
79
Increase 722
80
Reduction initial
81
Advance 54
82
Wane initial
83
Lesser Heat
84
Increase 618
85
Reduction 722
86
Advance 46
87
Wane 54
88
Greater Heat
89
Increase 514
90
Reduction 1,340
91
Advance 38
92
Wane 100
93
Start of Autumn
94
Increase 514
95
Reduction 1,854
96
Advance 38
97
Wane 138
98
End of Heat
99
Increase 618
100
Reduction 2,368
101
Advance 46
102
Wane 176
103
White Dew
104
Increase 722
105
Reduction 2,986
106
Advance 54
107
Wane 222
108
Autumn Equinox
109
Increase 722
110
Reduction 3,708
111
Retard 54
112
Wane 276
113
Cold Dew
114
Decrease 618
115
Reduction 2,986
116
Retard 46
117
Wane 222
118
Frost Descent
119
Decrease 514
120
Reduction 2,368
121
Retard 38
122
Wane 176
123
Start of Winter
124
Decrease 514
125
Reduction 1,854
126
Retard 38
127
Wane 138
128
Lesser Snow
129
Decrease 618
130
Reduction 1,340
131
Retard 46
132
Wane 100
133
Greater Snow
134
Decrease 722
135
Reduction 722
136
Retard 54
137
Wane 54
138
For each solar term, add its rate and the next term's rate, halve the sum, multiply by 12, and divide by cord and era to obtain the final rate. Subtract the two rates, multiply the remainder by 12, and divide by cord and era for the total difference. Multiply the total difference by 12 again and divide by cord and era for the separate difference. If the prior term is deficient, subtract the total difference from the final rate; if excessive, add it—to obtain the initial rate. Accumulate the separate difference: add to the initial rate when the prior term is deficient, subtract when excessive—to obtain the daily lodging difference and advance-retard rate. Then adjust cumulatively to obtain each day's fixed qi discharge-recovery and wax-wane accumulation. When later terms have no matching rate, take the prior final rate as the initial rate; if the prior term is deficient add the total difference; if excessive subtract the total difference—for the final rate. Apply the remaining steps according to the method.
139
For each solar term, apply the discharge-recovery accumulation below it: subtract discharge and add reduction from the mean qi to obtain fixed qi. Subtract the nearest new-moon or full-moon large and minor remainders from each fixed qi's remainders; multiply days by 12, reduce the remainder by the double-hour rate, and combine for the double-hour total. If the qi is prior-excessive multiply by the final rate; if prior-deficient multiply by the initial rate; divide by 12 for the total rate. If prior-excessive: subtract the double-hour total from cord and era, multiply by 12, divide by cord and era, and add to the total rate; multiply by the double-hour total and divide by 24; if prior-deficient: multiply the double-hour total twice by the separate difference and divide by 288—in both cases add to the total rate. Then advance-add and retard-subtract the qi wax-wane accumulation to obtain the fixed value. Apply the fixed accumulation to wax-add and wane-subtract the mean new, first-quarter, full, and last-quarter moons, obtaining wax-wane large and minor remainders.
140
Change cycle: 443,077.
141
Change days: 27, remainder 743, change odd: 1.
142
Change-odd factor: 12.
143
Lunar circuit factor: 67.
144
滿 滿 滿
Multiply total proper by the odd factor; cast out full change cycles; what remains, divide by the odd factor, for change parts. Carry excess general factor into days to obtain mean astronomical new moon at midnight entry into change. Add the mean new-moon minor remainder for the circuit double-hour entry. From new moon add 7 days, remainder 512, and odd 9 for first quarter. Continue adding for full moon, last quarter, and the next new moon. When the sum fills change days and remainder, cast it out. Again apply the wax-wane fixed accumulation at entry—wax-add and wane-subtract—to obtain wax-wane circuit double-hour entry for new moon and quarters.
145
Change days
146
Departure circuit
147
Increase-decrease rate
148
Slow-fast accumulation
149
Day 1
150
985
151
Increase 134
152
Speed initial
153
Day 2
154
974
155
Increase 117
156
Speed 134
157
Day 3
158
962
159
Increase 99
160
Speed 251
161
Day 4
162
948
163
Increase 78
164
Speed 350
165
Day 5
166
933
167
Increase 56
168
Speed 428
169
Day 6
170
918
171
Increase 33
172
Speed 484
173
Day 7
174
902
175
Increase of 9 at start and end, with hidden decrease
176
Speed 517
177
Day 8
178
886
179
Decrease 14
180
Speed 526
181
Day 9
182
870
183
Decrease 38
184
Speed 512
185
Day 10
186
854
187
Decrease 64
188
fast (moon ahead of mean motion) accumulation 474
189
variable-calendar day 11
190
separation progression 839
191
decrease rate 85
192
fast accumulation 412
193
variable-calendar day 12
194
separation progression 826
195
decrease rate 104
196
fast accumulation 327
197
variable-calendar day 13
198
separation progression 815
199
decrease rate 121
200
fast accumulation 223
201
variable-calendar day 14
202
separation progression 808
203
decrease rate 120 at day-start, increase 29 at day-end
204
fast accumulation 102
205
variable-calendar day 15
206
separation progression 810
207
increase rate 128
208
slow accumulation 29
209
variable-calendar day 16
210
separation progression 819
211
increase rate 115
212
slow accumulation 157
213
variable-calendar day 17
214
separation progression 832
215
increase rate 95
216
slow accumulation 272
217
variable-calendar day 18
218
separation progression 846
219
increase rate 74
220
slow accumulation 367
221
variable-calendar day 19
222
separation progression 861
223
increase rate 52
224
slow accumulation 441
225
variable-calendar day 20
226
separation progression 877
227
increase rate 28
228
slow accumulation 493
229
variable-calendar day 21
230
separation progression 893
231
increase rate 4; +4 at day-start, negligible decrease at day-end
232
slow accumulation 521
233
variable-calendar day 22
234
separation progression 909
235
decrease rate 20
236
slow accumulation 525
237
variable-calendar day 23
238
separation progression 925
239
decrease rate 44
240
slow accumulation 505
241
variable-calendar day 24
242
separation progression 941
243
decrease rate 68
244
slow accumulation 461
245
variable-calendar day 25
246
separation progression 955
247
decrease rate 89
248
slow accumulation 393
249
variable-calendar day 26
250
separation progression 968
251
decrease rate 108
252
slow accumulation 304
253
variable-calendar day 27
254
separation progression 979
255
decrease rate 125
256
slow accumulation 196
257
variable-calendar day 28
258
separation progression 985
259
decrease rate 144; −71 at day-start, carry increase into next day
260
slow accumulation 71
261
退 退 退
Subtract the next day's separation progression from the current one to obtain the advance-retreat difference. If the next value is larger, the motion is advancing; if smaller, retreating; if equal, level. For each syzygy and quarter-moon excess-deficit canonical-time entry, list the day's increase-decrease rate, average it with the next day's rate, and take the result as the common rate. Subtract the two rates to obtain the rate difference. For increasing rates: subtract the variable-calendar day remainder from the total divisor, multiply the remainder by the rate difference and divide by the total divisor, then add half the rate difference; For decreasing rates: halve the entry remainder, multiply by the rate difference and divide by the total divisor; in both cases add the common rate. Multiply by the entry remainder and divide by the total divisor to obtain the canonical-time variable rate. Halve it, subtract the fast component and add the slow component to the entry remainder, yielding the transfer remainder. For increasing cases subtract from the total divisor; for decreasing cases use the remainder directly; multiply by the rate difference and divide by the total divisor; Add to the common rate, multiply the variable rate thereby and divide by the total divisor; subtract fast and add slow to the variable rate to fix the rate. Then apply the fixed rate to increase or decrease the slow-fast accumulation and obtain the fixed value. Where no matching rate follows, derive from the preceding rate likewise. When increase applies, take the common rate as the initial value and subtract half the rate difference; When decrease applies, the common rate itself is used. When a calendar rate's increase-decrease pushes the entry remainder across a day boundary, split the day in two; compute separately for the beginning and end portions, then combine and adjust the variable rate accordingly.
262
Day 7: initial value 1,191; final value 149. Day 14: initial value 1,042; final value 298. Day 21: initial value 892; final value 448. Day 28: initial value 743; final value 597. For each case, compare the entry remainder with the initial threshold: at or below is the initial portion; above, subtract the threshold and treat the remainder as the final portion.
263
滿退
Apply the fixed slow-fast value for variable-calendar entry: subtract fast, add slow to the syzygy/quarter-moon excess-deficit minor remainder; If the result overflows or falls short, advance or retreat the day accordingly. Adding to the mean day yields excess (yíng); subtracting yields deficit (nò). Fix the major and minor remainders for each and name the day as before. Then cross-check successive new moons iteratively, taking actual excess-deficit results as the standard; Decreases must not violate deficit limits; increases must not exceed excess limits.
264
For the fixed new moon: same day-name as the next new moon means a major (30-day) month; different means a minor (29-day) month; no mid-term qi marks an intercalary month. When a crossing on the origin day should be visible at the computed hour, shift one or two months per the emission-absorption cycle to fix month length, placing deficiency on the last or second day; quarter and full moons follow the same cycle. Consecutive new-moon excess or deficit occurs at most three times in a row. If it exceeds this, adjust according to whether the fixed minor remainder falls near midnight.
265
觿 輿
Ecliptic: Southern Dipper (Nán Dǒu), width 24°328′. Ox (Niú), 7°. Maiden (Wǔ Nǚ), 11°. Emptiness (Xū), 10°. Rooftop (Wēi), 16°. Encampment (Yíng Shì), 18°. Eastern Wall (Dōng Bì), 10°. Legs (Kuí), 17°. Bond (Lóu), 13°. Stomach (Wèi), 15°. Hairy Head (Mǎo), 11°. Net (Bì), 16°. Turtle Beak (Zī Jī), 2°. Three Stars (Shēn), 9°. Eastern Well (Dōng Jǐng), 30°. Chariot Ghost (Yú Guǐ), 4°. Willow (Liǔ), 14°. Seven Stars (Qī Xīng), 7°. Extended Net (Zhāng), 17°. Wings (Yì), 19°. Chariot Crossboard (Zhěn), 18°. Horn (Jiǎo), 13°. Gullet (Kàng), 10°. Root (Dī), 16°. Chamber (Fáng), 5°. Heart (Xīn), 5°. Tail (Wěi), 18°. Winnowing Basket (Jī), 10°.
266
宿
At Winter Solstice, the daily solar longitude is fixed at 12° within the Dipper lodge. Add 15°292′5″ each time and reduce by lodge widths to obtain each fixed qi's hour-of-occurrence solar longitude.
267
退 退 退宿
Multiply the first-day station difference by the fixed-qi minor remainder, divide by the total divisor, and advance-add or retreat-subtract to obtain parts; Subtract from the hour-of-occurrence degree to obtain the qi-initial midnight solar longitude. Then add 1° per day, applying the station difference additively or subtractively, to obtain the next day. Set the fixed syzygy/quarter-moon minor remainder alongside; Multiply by the station difference, divide by the total divisor, advance-add or retreat-subtract the auxiliary value, and add to midnight solar longitude to obtain the hour-of-occurrence lodge position.
268
退退
The conjunction degree is the Moon's ecliptic longitude. First quarter: add 91°417′. Full moon: add 182°834′. Last quarter: add 273°1251′. Halve the parts, reduce one rank, and normalize by the progression divisor to obtain the hour-of-occurrence lunar longitude. From the canonical new-moon midnight variable-calendar day and remainder: if the fixed new moon advances or retreats a day, shift the midnight entry likewise. Accumulate by adding one day to obtain the next day.
269
退退 滿退
Multiply the midnight variable-entry remainder by the advance-retreat difference, divide by the total divisor, and advance-add or retreat-subtract the separation progression to fix the progression. Multiply by the fixed syzygy/quarter-moon minor remainder, divide by the total divisor, and subtract from the hour-of-occurrence lunar longitude to obtain midnight lunar longitude. For the next day, divide the fixed progression by the progression divisor and accumulate. Multiply the fixed progression by night quarters and divide by 200 to obtain the dawn portion. Subtract from the fixed progression to obtain the dusk portion. From midnight lunar longitude: after new moon add the dusk portion for dusk longitude; after full moon add the dawn portion for dawn longitude. For calendar annotation, multiply the quarter-moon minor remainder by 5 and divide by the progression divisor to obtain day-quarters. If less than the pre-dawn quarters, retreat one unit on the counting board.
270
Canonical time unit: 8 quarters, 24 parts.
271
Quarter-part divisor: 72.
272
Fixed solar term (dìng qì)
273
Day-quarters before dawn
274
Ecliptic departure from the celestial pole (declination proxy)
275
Daily day-length stretch/compression rate
276
Emission-absorption correction difference
277
Winter Solstice
278
30 day-quarters before dawn
279
115°3′ ecliptic departure from pole
280
daily stretch rate 1.3
281
emission correction +16
282
Lesser Cold
283
29 day-quarters 54/72 part before dawn
284
113°1′ ecliptic departure from pole
285
daily stretch rate 3.7
286
emission correction +16
287
Major Cold
288
29 day-quarters 18/72 part before dawn
289
110°7′ ecliptic departure from pole
290
daily stretch rate 6.1
291
emission correction +22
292
Start of Spring
293
28 day-quarters 33/72 part before dawn
294
107°9′ ecliptic departure from pole
295
daily stretch rate 9.4
296
emission correction +9
297
Awakening of Insects
298
27 day-quarters 30/72 part before dawn
299
102°9′ ecliptic departure from pole
300
daily stretch rate 17.5
301
emission correction +7
302
Rain Water
303
26 day-quarters 18/72 part before dawn
304
97°3′ ecliptic departure from pole
305
daily stretch rate 11.8
306
emission correction +3
307
Spring Equinox
308
25 day-quarters before dawn
309
91°3′ ecliptic departure from pole
310
daily stretch rate 12.25
311
absorption correction −3
312
Clear and Bright
313
23 day-quarters 54/72 part before dawn
314
85°3′ ecliptic departure from pole
315
daily stretch rate 11.8
316
absorption correction −7
317
Grain Rain
318
22 day-quarters 42/72 part before dawn
319
79°7′ ecliptic departure from pole
320
daily stretch rate 17.5
321
absorption correction −9
322
Start of Summer
323
21 day-quarters 39/72 part before dawn
324
74°7′ ecliptic departure from pole
325
daily stretch rate 9.4
326
absorption correction −22
327
滿
Lesser Fullness
328
20 day-quarters 54/72 part before dawn
329
70°9′ ecliptic departure from pole
330
daily stretch rate 6.1
331
absorption correction −16
332
Grain in Ear
333
20 day-quarters 18/72 part before dawn
334
68°5′ ecliptic departure from pole
335
daily stretch rate 3.7
336
absorption correction −16
337
Summer Solstice
338
20 day-quarters before dawn
339
67°3′ ecliptic departure from pole
340
daily compression rate 1.3
341
emission correction +16
342
Lesser Heat
343
20 ke 18 fen.
344
68 degrees 5 fen.
345
Contraction: 3.7 fen.
346
Increase: 16.
347
Major Heat.
348
20 ke 54 fen.
349
70 degrees 9 fen.
350
Contraction: 6.1 fen.
351
Increase: 22.
352
Start of Autumn.
353
21 ke 39 fen.
354
74 degrees 7 fen.
355
Contraction: 9.4 fen.
356
Increase: 9.
357
End Heat.
358
22 ke 42 fen.
359
79 degrees 7 fen.
360
Contraction: 17.5 fen.
361
Increase: 7.
362
White Dew.
363
23 ke 54 fen.
364
85 degrees 3 fen.
365
Contraction: 11.8 fen.
366
Increase: 3.
367
Autumn Equinox.
368
25 ke.
369
91 degrees 3 fen.
370
Contraction: 12.25 fen.
371
Decrease: 3.
372
Cold Dew.
373
26 ke 18 fen.
374
97 degrees 3 fen.
375
Contraction: 11.8 fen.
376
Decrease: 7.
377
Frost's Descent.
378
27 ke 30 fen.
379
102 degrees 9 fen.
380
Contraction: 17.5 fen.
381
Decrease: 9.
382
Start of Winter.
383
28 ke 33 fen.
384
107 degrees 9 fen.
385
Contraction: 9.4 fen.
386
Decrease: 22.
387
Minor Snow.
388
29 ke 18 fen.
389
110 degrees 7 fen.
390
Contraction: 6.1 fen.
391
Decrease: 16.
392
Major Snow.
393
29 ke 54 fen.
394
113 degrees 1 fen.
395
Contraction: 3.7 fen.
396
Decrease: 16.
397
滿 滿 滿
Set each solar term's flexion and extension rate, then apply the opening-closing difference to obtain the daily flexion and extension rate. When the difference reaches 10, carry to the fen; when fen reach 10, that becomes the rate. Accumulate each day's rate to obtain ke-fen. Multiply by 180 and divide by 11 times the cycle constant to obtain the ke-difference. Halve each; where extended subtract and where contracted add to the morning-before ke-fen to obtain the daily fixed morning-before ke. Double it to obtain night ke. Subtract from 100 to obtain day ke. Divide the ke-difference by 34 to obtain fen; when fen reach 10, that becomes degrees. Where extended subtract and where contracted add to the ecliptic departure from the pole at the start of the qi, to obtain each day's value. Multiply day ke by the period constant, multiply by 200, and divide by the general divisor to obtain dusk mid-degrees. Subtract from 365 degrees 328 fen; the remainder is dawn mid-degrees. Add each to the daily solar position to obtain dusk and dawn culminating stars, reckoned on the equator. Its equatorial coordinates match the Taichu star distances.
398
Nodal-travel completion rate: 10,939,313.
399
Odd rate: 300.
400
Reduced completion: 36,464; odd 113.
401
Node center: 18,232; odd 56.5.
402
Nodal period: 27 days; remainder 284; odd 113.
403
Mid-node day: 13 days; remainder 812; odd 56.5.
404
New-moon eclipse: 3,106; odd 187.
405
True full moon: 19,785; odd 150.
406
Posterior limit: 1,553; odd 93.5.
407
Prior limit: 16,678; odd 263.
408
滿 滿
Set the total constant, multiply by the odd rate, and discard full multiples of the completion rate; the remainder, reduced by the odd rate, gives the entry-into-node parts. Add the heaven-normal mean new-moon minor remainder to obtain the new-moon general node parts. To find the next new moon, add the new-moon eclipse parts. From new moon to find full moon, add the true full moon parts. For each, take the new-moon or full-moon entry-qi elongation fixed accumulation; add if elongating, subtract if contracting; also multiply the slow-fast fixed number by 60 and divide by 777 to obtain the limit number; subtract if slow and add if fast to obtain the fixed node parts. At new moon, if the moon is inside the solar path, subtract the limit number entered from the slow-fast fixed number; with the remainder, subtract if slow and add if fast to the fixed node parts. If it exits outside the solar path, that is the variable node parts. If it does not exit outside, use the fixed node parts. If the variable node parts fall within 3.5 double-hours, apply the waxing-waning procedure to determine whether an eclipse occurs. Below the mid-node, the moon is on the outer path; above it, subtract; the remainder is the moon on the inner path. If the parts are at or below the posterior limit, that is post-node parts; if at or above the prior limit, subtract inversely from the node center; the remainder is pre-node parts. At full moon there is a lunar eclipse; at new moon, if on the inner path, there is a solar eclipse. Divide pre- and post-node parts by 112 to obtain the distance-from-node in double-hours. Set the fixed new-moon minor remainder aside. Divide by the double-hour rate; in sequence gen, xun, kun, qian, count beyond the tally. Of the remainder, at or below half the divisor is initial; above that, subtract to obtain final. If initial, use the remainder; if final, subtract the divisor—each gives the difference-rate. If the moon is on the inner path, increase the distance-from-node in double-hours by three-tenths and divide. Multiply by the difference-rate and divide by 14 to obtain the difference. At new moon, if within one qi before or after either equinox, use the difference as fixed; near winter solstice use the distance from Cold Dew and Rain Water; near summer solstice use the distance from Clear and Bright and White Dew; multiply the qi count, and again increase by three-tenths of the distance-from-node; near winter solstice gen and xun add and kun and qian subtract; near summer solstice gen and xun subtract and kun and qian add to the difference, as the fixed difference. Gen and xun add to the aside; kun and qian subtract from the aside. If the moon is on the outer path, reduce the distance-from-node count by three-tenths, multiply by the difference-rate, and divide by 14 to obtain the difference. Gen and kun subtract from the aside; xun and qian add to the aside, as the eclipse fixed minor remainder. At full moon, follow the fixed full-moon minor remainder—that is the double-hour of occurrence; if near dawn or dusk, check within 12.5 ke before and after using sunrise and sunset ke.
409
If the moon is on the outer path, at new moon there should be no eclipse. On the first day of summer solstice, use 248 as the initial limit. If pre- and post-node parts are at or below the initial limit and the add-time is within 7 ke before or after noon, there is an eclipse. Before and after new moon from summer solstice, diminish the initial limit by 2 fen each day, completing at 94 days, as the daily variable limit. If node parts are at or below the variable limit and the add-time is as above, there is also an eclipse. Also subtract the final limit of 60 from the initial and variable limits; divide the remainder by 18 to obtain the ke-limit. Combine with the count within 7 ke before and after noon, as the time-limit. If node parts are within the add-time limit and at or below the final limit, there is also an eclipse. Also set the final limit; add 18 for each ke, as the difference-limit. If the add-time ke from before or after noon is at or above the ke-limit and node parts are at or below the difference-limit, there is also an eclipse. From autumn equinox through spring equinox, if the distance from node is at or below the final limit and the add-time is si, wu, or wei, there is also an eclipse.
410
If the moon is on the inner path, at new moon there should be an eclipse. If at the first day of summer solstice, use 1,373 as the initial limit. If the distance from node is at or above the initial limit and the add-time is within 18 ke before or after noon, there may be no eclipse. Before and after summer solstice, increase the initial limit by 1.5 fen each day, completing at 94 days, as the daily variable limit. Subtract the variable limit from the initial limit; one-tenth of the remainder is the ke-limit. Subtract from 18 ke before and after noon; the remainder is the time-limit. If the distance from node is above the variable limit and the add-time is within the limit, there may be no eclipse.
411
Remove the fixed pre- and post-node parts: in winter subtract 224; in summer subtract 54; in spring, post-node subtract 100 and pre-node subtract 200; in autumn, post-node subtract 200 and pre-node subtract 100. If subtraction would go negative, the eclipse is total. If there is a remainder, subtract from the posterior limit; divide by 104 to obtain lunar eclipse parts.
412
滿
At new-moon node with the moon on the inner path, entering winter solstice through fixed Rain Water, and autumn equinox through Major Snow, all use 558 as the eclipse-difference. Entering spring equinox, diminish by 6 fen each day, completing at Grain in Ear. Subtract the eclipse-difference from the distance-from-node parts; if subtraction would go negative, reverse-subtract the eclipse-difference to obtain the non-eclipse threshold. For the non-eclipse threshold, from Lesser Full Grain through Minor Heat, if the add-time is outside 7 ke before or after noon, subtract 1 double-hour in all cases; if within 3 ke, add 1 double-hour. From Major Cold through Start of Spring, pre-node beyond 5 double-hours, and from Major Heat through Start of Winter, post-node beyond 5 double-hours, subtract 1 double-hour in all cases; if within 5 double-hours, add 1 double-hour. For all add-time eclipse-differences that call for subtraction, subtract at post-node and add at pre-node; those that call for addition, add at post-node and subtract at pre-node. If subtraction would go negative, the eclipse is total; if the adjustment enters the non-eclipse threshold, there may be no eclipse. If the moon is on the outer path, on the first day of winter solstice, there is no eclipse-difference. Thereafter increase by 6 fen each day, completing at Rain Water. Entering spring equinox through White Dew, all use 522 as the difference. After autumn equinox, diminish by 6 fen each day, completing at Major Snow. Add the difference to the distance-from-node parts to obtain eclipse parts. Subtract from the posterior limit; the remainder is the non-eclipse threshold. Divide the eclipse-difference by 15 and multiply by 104 to obtain the fixed divisor. For the non-eclipse threshold, if the fixed divisor yields 1, subtract from 15; the remainder is solar eclipse magnitude.
413
Jupiter total rate: 534,483; odd 45. Invisibility parts: 24,031; odd 72.5.
414
Total days: 398; remainder 1,163; odd 45.
415
滿
At mean appearance, entering winter solstice through Minor Cold, uniformly subtract 6 days. Entering Major Cold, diminish by 67 fen each day. Entering spring equinox, use the mean rate. Then add 89 fen each day. Entering Start of Summer through Lesser Full Grain, uniformly add 6 days. Entering Grain in Ear, diminish by 89 fen each day. Entering summer solstice through Start of Autumn, uniformly add 4 days. Entering End Heat, diminish by 178 fen each day. Entering White Dew, use the mean rate. Thereafter diminish by 52 fen each day. Entering Minor Snow through Major Snow, uniformly subtract 6 days.
416
退退 退退
Initial direct motion: 114 days covering 18 degrees 509 parts, slowing by 1 part each day. First station: 26 days. Then retrograde: 42 days, retreating 6 degrees 12 parts, speeding by 2 parts each day. Retrograde again: 42 days, retreating 6 degrees 12 parts, slowing by 2 parts each day. Second station: 25 days. Later direct motion: 114 days covering 18 degrees 509 parts, speeding by 1 part each day. When its days are exhausted it disappears at evening.
417
Mars total rate: 1,045,080; odd 60. Invisibility parts: 97,090; odd 30.
418
Total days: 779; remainder 1,220; odd 60.
419
At mean appearance, entering winter solstice, subtract 27 days. Thereafter diminish by 603 fen each day. Entering Major Cold, add 402 fen each day. Entering Rain Water through Grain Rain, uniformly add 27 days. Entering Start of Summer, diminish by 198 fen each day. Entering Start of Autumn, use the mean rate. Entering End Heat, diminish by 198 fen each day. Entering Minor Snow through Major Snow, uniformly subtract 27 days.
420
滿
Initial direct motion, entering winter solstice: rate 243 days for 165 degrees of travel. Then every 3 days diminish the day-rate and degree-rate by 2 each. On the first day of Minor Cold, rate 233 days for 155 degrees of travel. Then diminish by 1 every 2 days. Entering Grain Rain for 4 days, use the mean rate; through Lesser Full Grain for 9 days, rate 178 days for 100 degrees of travel. Then diminish by 1 every 3 days. On the first day of summer solstice, use the mean rate; through 6 days, rate 171 days for 93 degrees of travel. Then increase by 1 every 3 days. On the first day of Start of Autumn, 184 days for 106 degrees of travel. Then increase by 1 each day. On the first day of White Dew, rate 214 days for 136 degrees of travel. Then increase by 6 every 5 days. On the first day of autumn equinox, rate 232 days for 154 degrees of travel. Again increase by 1 each day. On the first day of Cold Dew, rate 247 days for 169 degrees of travel. Then increase by 3 every 5 days. Entering Frost's Descent for 5 days, use the mean rate; through Start of Winter for 13 days, rate 259 days for 181 degrees of travel. Then diminish the day-rate by 1 every 2 days. Entering winter solstice, return to the initial rate.
421
退 滿
For each regular qi entered: if mean, follow the rate; otherwise calculate the daily increase or decrease to obtain the initial-rapid day-degree fixed rate. For initial slow motion and station-retreat, if the qi entered calls for day or degree adjustments, calculate daily increase and decrease—all follow this method. Rapid-travel day-rate: entering Major Cold, diminish by 1 every 6 days; entering spring equinox through Start of Summer, uniformly subtract 10 days; entering Lesser Full Grain, diminish the subtracted amount by 1 every 3 days; through Grain in Ear, use the mean rate; entering Start of Autumn, increase by 1 every 3 days; entering White Dew through autumn equinox, uniformly add 10 days; entering Cold Dew, diminish the added amount by 1 every 1.5 days; when the qi is exhausted, use the mean rate—this is the variable day-rate. Rapid-travel degree-rate: entering Major Cold through Awakening of Insects, Start of Summer through summer solstice, Major Heat through qi exhaustion, and Frost's Descent through Minor Snow, all add 4 degrees; Clear and Bright through Grain Rain, add 2 degrees—this is the variable degree-rate.
422
滿調
At initial travel entering End Heat, subtract 60 from the day-rate and 30 from the degree-rate; entering White Dew through autumn equinox, subtract 44 from the day-rate and 22 from the degree-rate—all as initial slow half-degree travel. When these days and degrees are exhausted, calculate the remaining day- and degree-rates subtracted and continue as rapid motion. Initial travel entering Major Cold through Major Heat uses differential motion, slowing by 1 part each day. For initial slow and later slow phases, since the day-rate already has increase and decrease, the increasingly slow and increasingly fast difference-parts are all checked against the initial-rapid last-day motion-parts to obtain the initial-slow first-day motion-parts. Subtract the initial-slow uniform-motion parts; the remainder is the initial-slow total difference. The later-rapid first-day motion-parts are the later-slow last-day motion-parts; subtract the later-slow first-day motion-parts; the remainder is the later-slow total difference. Subtract the two to obtain the before-and-after separate day-difference parts. Any remainder is adjusted as minor parts. At the slow-rapid transition, where motion-parts decay irregularly, follow this method.
423
滿
Initial slow motion, entering winter solstice: rate 60 days for 25 degrees of travel; Initially fast, slowing by 2 parts each day. Entering Lesser Cold, subtract 1 every 3 days. On the first day of Great Cold, the rate is 55 days for 20 degrees. Then increase by 1 every 3 days. From the first day of Start of Spring through Clear and Bright, use uniform motion at 25 degrees in 60 days. Entering Grain Rain, subtract 1 degree per solar term. From the first day of Start of Summer through Lesser Full Grain, use uniform motion at 22 degrees in 60 days. Entering Grain in Ear, add 1 degree per solar term. From the first day of summer solstice through End Heat, use uniform motion at 25 degrees in 60 days. Entering White Dew, subtract 1 every 3 days. On the first day of Autumn Equinox, the rate is 60 days for 25 degrees. Then add 1 to the day-count each day and 2 to the degree-count every 3 days. On the first day of Cold Dew, the rate is 75 days for 30 degrees. Then subtract 1 from the day-count each day and 1 from the degree-count every 3 days. On the first day of Frost's Descent, the rate is 60 days for 25 degrees. Then subtract 1 degree every 2 days. One day after entering Start of Winter through the end of the qi, use uniform motion at 17 degrees in 60 days. Entering Lesser Snow, add 1 degree every 5 days. On the first day of Great Snow, the rate is 60 days for 20 degrees. Then add 1 degree every 3 days. Entering winter solstice, return to the initial values.
424
退西 退 退 退 退 退 退 退 退 退
First stationary period: 13 days. If the initial rapid phase subtracted 1 from the day-rate, distribute that amount to increase this stationary and later slow day-rates. If the initial rapid phase added to the day-rate, distribute that amount to decrease this stationary and later slow day-rates. Then retrograde, moving westward. On the first day of winter solstice, the rate is 63 days retreating 21 degrees. Then add 1 degree every 4 days. One day into Lesser Cold, the rate is 63 days retreating 26 degrees. Then subtract 1 degree every 3.5 days. Three days into Start of Spring through Awakening of Insects, use uniform motion at 17 degrees retreated in 63 days. Then add 1 each to the day-count and degree-count every 2 days. Eight days into Rain Water through the end of the qi, use uniform motion at 21 degrees retreated in 67 days. Entering Spring Equinox, subtract 1 each from the day-count and degree-count per solar term. On the first day of Great Heat through the end of the qi, use uniform motion at 12 degrees retreated in 58 days. On the first day of Start of Autumn through the end of the qi, use uniform motion at 11 degrees retreated in 57 days. Then add 1 to the day-count every 2 days. Nine days into Cold Dew through the end of the qi, use uniform motion at 20 degrees retreated in 66 days. Then subtract 1 every 2 days. Six days into Frost's Descent through the end of the qi, use uniform motion at 17 degrees retreated in 63 days. Then add 1 every 3 days. Eleven days into Start of Winter through the end of the qi, use uniform motion at 21 degrees retreated in 67 days. Then subtract 1 every 2 days. Entering winter solstice, return to the initial values.
425
Later stationary period: at winter solstice, stationary for 13 days. Then add 1 every 2.5 days. On the first day of Great Cold through the end of the qi, stationary for 25 days. Then subtract 1 every 2.5 days. On the first day of Rain Water, stationary for 13 days. Then add 1 every 3 days. On the first day of Clear and Bright, stationary for 23 days. Then subtract 1 each day. Ten days into Clear and Bright through End Heat, use the mean rate; stationary for 13 days. Then subtract 1 every 2 days. Eleven days into Autumn Equinox, no stationary period. Then add 1 each day. On the first day of Frost's Descent, stationary for 19 days. Then subtract 1 every 3 days. From Start of Winter through Great Snow, stationary for 13 days.
426
Later slow phase: direct motion, 25 degrees in 60 days, accelerating by 2 parts each day. If the initial rapid phase added degrees, subtract that amount in this slow phase to get the fixed total. If the initial rapid phase added no degrees, subtract 3 degrees from this slow phase between Autumn Equinox and Start of Winter, and 5 degrees entering winter solstice. If the later stationary fixed days fall short by 13, add the shortfall in days to this slow day-rate.
427
Later rapid phase: on the first day of winter solstice, the rate is 210 days for 132 degrees. Then subtract 1 each day. Eight days into Great Cold, the rate is 172 days for 94 degrees. Then subtract 1 every 2 days. At Awakening of Insects through the end of the qi, use uniform motion at 83 degrees in 161 days. Then add 1 every 2 days. Fourteen days into Grain in Ear through summer solstice, use uniform motion at 155 degrees in 233 days. Then add 1 each day. On the first day of Great Heat through End Heat, use uniform motion at 185 degrees in 263 days. Then subtract 1 every 2 days. One day into Autumn Equinox, the rate is 255 days for 177 degrees. Then subtract 1 every 1.5 days. On the first day of Great Snow, the rate is 205 days for 127 degrees. Then add 1 every 3 days. Entering winter solstice, return to the initial values.
428
退 退 退 退
Where the day- and degree-rates for entering regular qi have adjustments, calculate the daily increase or decrease to obtain the later rapid fixed day- and degree-rates. For the rapid-motion day-rate: if the earlier slow fixed days fall short by 60 or the retrograde fixed days fall short by 63, add the shortfall in days to the rapid-motion fixed day-rate; if the earlier slow fixed days exceed by 60, retrograde fixed days exceed by 63, or later stationary fixed days exceed by 13, subtract the surplus in days from this rapid fixed day-rate—each yields a variable day-rate. For the rapid-motion degree-rate: if the earlier slow fixed degrees fall short by 25, retrograde fixed degrees exceed by 17, or the later slow phase subtracts degrees between Autumn Equinox and winter solstice, add the surplus or shortfall in degrees to this rapid fixed rate; if the earlier slow fixed degrees exceed by 25 or retrograde fixed degrees fall short by 17, subtract the surplus or shortfall in degrees from this rapid fixed degree-rate—each yields a variable degree-rate.
429
If the initial motion falls between Spring Equinox and Grain Rain, use variable motion, accelerating by 1 part each day. If the initial motion falls between Start of Summer and summer solstice, travel half a degree per day, covering 33 degrees in 66 days. From Lesser Heat through Great Heat, 25 degrees in 50 days. From Start of Autumn through the end of the qi, 10 degrees in 20 days. Continue with the diminished rates as before. When the allotted days and degrees are used up, enter evening invisibility.
430
Saturn total cycle rate: 506,623; remainder 29.
431
Invisibility fraction: 22,831; remainder 64½.
432
Total days: 378; remainder 103; odd part 29.
433
For mean appearance at winter solstice, initially subtract 4 days. Then each day add 89 parts. Entering Great Cold through Spring Equinox, subtract an even 8 days. Entering Clear and Bright, reduce by 59 parts each day. On entering Lesser Heat, use the mean rate. Thereafter add 89 parts each day. On entering White Dew, add 8 days. Thereafter reduce by 178 parts each day. Entering Autumn Equinox, add an even 4 days. Entering Cold Dew, reduce by 59 parts each day. On the first day of Lesser Snow, use the mean rate. Then reduce by 89 parts each day.
434
退退 退退
At first direct motion, 7 degrees 290 parts in 83 days, slowing by half a part each day. First stationary period: 37 days. Then retrograde, retreating 2 degrees 491 parts in 51 days, accelerating by half a part less each day. Again retrograde, retreating 2 degrees 491 parts in 51 days, slowing by half a part less each day. Later stationary period: 37 days. Later direct motion, 7 degrees 290 parts in 83 days, accelerating by half a part each day. When the days are used up, enter evening invisibility.
435
Venus total cycle rate: 784,449; remainder 9. Invisibility fraction: 56,224; remainder 54½.
436
Total days: 583; remainder 1,229; odd part 9.
437
Evening visibility and invisibility: 256 days.
438
Morning visibility and invisibility: 327 days; remainder 1,229; odd part 9.
439
For evening mean appearance at winter solstice, initially use the mean rate, then reduce by 100 parts each day. Entering Awakening of Insects through Spring Equinox, subtract an even 9 days. Entering Clear and Bright, reduce by 100 parts each day. Entering Grain in Ear, use the mean rate. Entering summer solstice, add 100 parts each day. Entering End Heat through Autumn Equinox, add an even 9 days. Entering Cold Dew, reduce by 100 parts each day. Entering Great Snow, use the mean rate.
440
滿 退退
Evening direct motion from winter solstice through Start of Summer and from Start of Autumn through Great Snow: 206 degrees in 172 days. After Lesser Full Grain, add 1 degree every 10 days as the fixed total. Entering White Dew through Spring Equinox, use variable motion, slowing by an additional 2 parts. In all other seasons, use uniform motion. From summer solstice through Lesser Heat, 209 degrees in 172 days. Entering Great Heat, subtract 1 degree every 5 days through the end of the qi. Uniform motion from winter solstice and from Great Heat through the end of the qi: 13 degrees in 13 days. After winter solstice, subtract 1 every 10 days through Start of Spring. After Start of Autumn, add 1 every 10 days through Autumn Equinox. From Awakening of Insects through Grain in Ear, 7 degrees in 7 days. After summer solstice, add 1 every 5 days through Lesser Heat. On the first day of Cold Dew, 22 degrees in 23 days; then subtract 1 every 6 days through Lesser Snow. Direct slow motion, 30 degrees in 42 days, slowing by 8 parts each day. If the initial rapid phase added more than 206 degrees, subtract that amount from this phase. Evening stationary period: 7 days. Evening retrograde: 5 degrees in 10 days. When the days are used up, enter evening invisibility.
441
滿
For morning mean appearance at winter solstice, use the mean rate. Entering Lesser Cold, add 67 parts each day. Entering Start of Spring through Start of Summer, add an even 3 days. Entering Lesser Full Grain, reduce by 67 parts each day. Entering summer solstice, use the mean rate. Entering Lesser Heat, reduce by 67 parts each day. Entering Start of Autumn through Start of Winter, subtract an even 3 days. Entering Lesser Snow, reduce by 67 parts each day.
442
退退 滿 滿 滿
Morning retrograde: 5 degrees in 10 days. Morning stationary period: 7 days. Direct slow motion from winter solstice through Start of Summer and from Great Snow through the end of the qi: 30 degrees in 42 days, accelerating by 8 parts each day. After Lesser Full Grain, subtract 1 degree every 10 days through Grain in Ear. From summer solstice through Cold Dew, 27 degrees in 42 days. Entering Frost's Descent, add 1 degree per solar term through Lesser Snow. Uniform motion from winter solstice through the end of the qi and from Start of Summer through the end of the qi: 13 degrees in 13 days. After Lesser Cold, add 1 each to the day-count and degree-count every 6 days through Awakening of Insects. After Lesser Full Grain, subtract 1 each from the day-count and degree-count every 7 days through Start of Autumn. On the first day of Rain Water, 23 degrees in 23 days. Thereafter subtract 1 each from the day-count and degree-count every 6 days through Grain Rain. From End Heat through Cold Dew, there is no uniform-motion phase. After Frost's Descent, add 1 each to the day-count and degree-count every 5 days through Great Snow. Rapid motion: 206 degrees in 172 days. If the earlier slow phase subtracted fewer than 30 degrees, add that amount in this rapid phase. From End Heat through Cold Dew, use variable motion, accelerating by 1 part each day. In all other seasons, use uniform motion. When the days are used up, enter morning invisibility.
443
Mercury total cycle rate: 155,278; remainder 66.
444
Invisibility fraction: 22,699; remainder 33.
445
Total days: 115; remainder 1,178; odd part 66.
446
Evening visibility and invisibility: 52 days.
447
Morning visibility and invisibility: 63 days; remainder 1,178; odd part 66.
448
For evening mean appearance from winter solstice through Clear and Bright, use the mean rate. Entering Grain Rain through Grain in Ear, subtract an even 2 days. Entering summer solstice through Great Heat, use the mean rate. Entering Start of Autumn through Frost's Descent, it should appear but does not. If within Start of Autumn or Frost's Descent, the evening distance from the sun is between 18 and 36 degrees and Jupiter, Mars, Saturn, or Venus is present, Mercury also appears.
449
Entering Start of Winter through Great Snow, use the mean rate.
450
Direct rapid motion: 21 degrees 6 parts in 12 days, at 1 degree 503 parts per day. From Great Heat through End Heat, 17 degrees 2 parts in 12 days, at 1 degree 280 parts per day. Uniform motion: 7 degrees in 7 days. After Great Heat, subtract 1 each from the day-count and degree-count every 2 days. Entering Start of Autumn, omit this uniform-motion phase. Direct slow motion: 2 degrees 4 parts in 6 days, at 224 parts per day. If the earlier rapid phase covered 17 degrees, omit this slow-motion phase. Evening stationary period: 5 days. When the days are used up, enter evening invisibility.
451
滿
For morning mean appearance at winter solstice, subtract an even 4 days. Entering Lesser Cold through Great Cold, use the mean rate. Entering Start of Spring through Awakening of Insects, subtract an even 3 days. If within Awakening of Insects, at the same solar distance as described above, and no Jupiter, Mars, Saturn, or Venus is visible in the morning, it does not appear. Entering Rain Water through Start of Summer, it should appear but does not. If within Start of Summer, at the same solar distance as described above, and Jupiter, Mars, Saturn, or Venus is visible in the morning, it also appears. Entering Lesser Full Grain through Cold Dew, use the mean rate. Entering Frost's Descent through Start of Winter, add an even 1 day. Entering Lesser Snow through Great Snow, use the mean rate.
452
Morning appearance: stationary for 5 days. Direct slow motion: 2 degrees 4 parts in 6 days, at 224 parts per day. Entering Great Cold through Awakening of Insects, omit this slow-motion phase. Uniform motion: 7 degrees in 7 days. After Great Cold, subtract 1 each from the day-count and degree-count every 2 days. Entering Start of Spring, omit this uniform-motion phase. Direct rapid motion: 21 degrees 6 parts in 12 days, at 1 degree 503 parts per day. If there was no slow phase earlier, 17 degrees 10 parts in 12 days, at 1 degree 280 parts per day. When the days are used up, enter morning invisibility.
453
退退
For each planet, subtract the invisibility fraction from the accumulated remainder and divide by the total cycle rate; take the remainder, subtract it from the rate, divide by the degree-factor to get days. If the celestial corrected new moon and mean new moon differ in advance or retreat, also subtract a day for advance and add a day for retreat. Then cast out full months according to their lengths, count the day beyond the starting count, and obtain the mean appearance date. Halve each planet's appearance remainder to match the half-total. For Venus and Mercury, add the evening visibility-and-invisibility days to get the morning mean appearance. For each planet, apply the daily increments or decrements according to the solar term entered and the scheduled daily adjustments; when complete, apply the remainder to adjust the mean appearance to get the regular appearance. Then take half the waxing-waning fixed number for the regular appearance day, subtract at waning and add at waxing, to get the fixed appearance day and parts.
454
退宿 滿
Set the fixed appearance midnight solar longitude, halve the parts, multiply the fixed appearance remainder by the solar-longitude difference and divide by the total factor, advance to add or retreat to subtract; then subtract (morning) or add (evening) the planet's solar distance—Jupiter 14°, Venus 11°, Mars, Saturn, and Mercury 17° each—to get the first-appearance fixed lodge and degree. Halve the first-appearance waxing-waning fixed number and use waning to add and waxing to diminish the planet's first-appearance motion and stationary day-rates. Jupiter and Saturn require no such adjustment. When the adjustment does not fill a day, combine it with the appearance date; if over half, count as a full day; then use the planet's day- and degree-rates to find the initial day's motion-parts.
455
宿
Set the fixed appearance remainder, subtract it from the half-total, multiply each by the initial day's motion-parts and divide by the half-total; add in direct motion or subtract in retrograde from the first-appearance fixed lodge and degree to get the midnight lodge and degree after appearance. Add or subtract the degrees and parts traveled, forward in direct motion and backward in retrograde. When motion varies between faster and slower phases, set aside the initial day's motion-parts and apply the daily differential—subtracting for deceleration, adding for acceleration; during stationary, continue from the prior value; during retrograde, subtract accordingly; reduce motion-parts to degrees and parts by the circuit method to find each day's position.
456
To find motion-parts, multiply the fixed degree-rate by the half-total, carrying any fractional parts. Divide by the day-rate to get the uniform-motion degrees and parts. Set the fixed day-rate, subtract 1, multiply by the differential parts, and halve the result to get the differential rate. Subtract for acceleration and add for deceleration to the uniform motion to get the initial day's degrees and parts.
457
When Zhongzong restored the throne, Chief Clerk of the Astrological Office Nangong Shuo held that the Lindé calendar's origin epoch, with its five-planet qi-entry adjustments, did not match the true alignment of combined disks and strung pearls; using Shenlong 1, year yi-si, he therefore compiled the Yisi Origin Calendar. Extrapolating upward, with an accumulated count of 414,360, he obtained eleventh-month jiazi new moon at midnight on winter solstice, with the seven luminaries beginning at the start of Ox. Its method used the ecliptic but not the equator; computing the five planets began with stepping out the fixed conjunction and adding invisibility days to obtain fixed appearance. The rest was the same as Li Chunfeng's method. What differed was only the add-subtract difference at mean conjunction. Once it was completed, Ruizong took the throne and it was abolished.
458
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Collation notes for this chapter.
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