SAPM à Hemmingford
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the SAPM à Hemmingford clear sky chart from 2005-11-06 to 2024-01-31.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.
Observation TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(no limit)Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
27%
22664
13%
74975
7%
22625
34%
22625
14%
54682

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 10thNight
13%
760
9%
2649
3%
757
19%
757
6%
2146
January11th to 20thNight
15%
760
8%
2660
3%
760
22%
760
7%
2156
January21st to endNight
18%
835
10%
2919
6%
835
26%
835
11%
2175
February1st to 10thNight
14%
720
9%
2370
2%
720
22%
720
8%
1924
February11th to 20thNight
16%
703
11%
2166
4%
700
26%
700
12%
1646
February21st to endNight
20%
592
15%
1776
5%
592
32%
592
13%
1335
March1st to 10thNight
21%
720
13%
2160
8%
720
29%
720
12%
1658
March11th to 20thNight
20%
720
14%
2098
6%
720
28%
720
14%
1574
March21st to endNight
25%
792
19%
1980
7%
792
33%
792
18%
1479
April1st to 10thNight
23%
720
15%
1800
4%
720
29%
720
17%
1378
April11th to 20thNight
24%
711
13%
1775
3%
711
29%
711
18%
1346
April21st to endNight
24%
577
16%
1657
7%
577
31%
577
16%
1222
May1st to 10thNight
29%
437
16%
1517
11%
437
38%
437
16%
1052
May11th to 20thNight
29%
354
19%
1416
16%
354
42%
354
17%
899
May21st to endNight
34%
388
14%
1551
11%
388
45%
388
18%
977
June1st to 10thNight
34%
360
10%
1440
10%
360
44%
360
14%
993
June11th to 20thNight
37%
360
11%
1440
12%
360
44%
360
18%
907
June21st to endNight
37%
360
10%
1440
11%
360
45%
360
16%
962
July1st to 10thNight
46%
350
14%
1400
15%
350
57%
350
23%
842
July11th to 20thNight
55%
348
14%
1392
19%
348
60%
348
23%
825
July21st to endNight
52%
394
14%
1486
16%
372
57%
372
20%
913
August1st to 10thNight
57%
358
17%
1422
20%
356
61%
356
23%
847
August11th to 20thNight
51%
556
17%
1620
11%
556
55%
556
27%
1064
August21st to endNight
47%
792
18%
1980
8%
792
50%
792
29%
1338
September1st to 10thNight
45%
720
15%
1800
6%
720
48%
720
30%
1229
September11th to 20thNight
49%
720
20%
1881
12%
720
52%
720
31%
1216
September21st to endNight
39%
720
20%
1980
14%
720
44%
720
27%
1326
October1st to 10thNight
33%
720
16%
2087
10%
720
40%
720
19%
1471
October11th to 20thNight
27%
720
15%
2196
9%
720
35%
720
17%
1590
October21st to endNight
21%
792
11%
2574
5%
792
30%
792
13%
1942
November1st to 10thNight
22%
740
15%
2407
8%
740
32%
740
14%
1719
November11th to 20thNight
21%
760
16%
2515
10%
760
30%
760
13%
1833
November21st to endNight
16%
760
10%
2660
4%
760
25%
760
9%
2046
December1st to 10thNight
14%
760
7%
2660
2%
760
20%
760
6%
2202
December11th to 20thNight
13%
759
9%
3253
3%
759
22%
759
6%
2566
December21st to endNight
12%
826
4%
4848
2%
817
17%
817
4%
3884

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

Occurrence of each ForecastData
Points
Cloud CoverDay
18%9%47%6%35%5%5%7%32%
74908
Night
19%10%47%6%35%45%6%31%
75217
TransparencyDay
51%7%11%19%10%1
74613
Night
54%7%11%18%10%1
75046
SeeingDay
23%15%29%21%9%2
13546
Night
24%14%29%25%9%1
22676

By Month

Percentage Cloud Cover NE (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
18%18%6%11%6%46%44419%
1517
11th to 20thDay
18%18%6%11%8%3445%421%
1520
21st to endDay
12%15%6%9%7%5%5%6%5%6%24%
1664
February1st to 10thDay
17%16%6%11%7%36%45%5%20%
1588
11th to 20thDay
13%14%5%11%8%35%5%45%26%
1682
21st to endDay
17%15%7%7%8%44446%23%
1480
March1st to 10thDay
17%13%49%7%37%5%45%26%
1797
11th to 20thDay
17%11%5%7%7%35%447%31%
1860
21st to endDay
20%11%37%6%24345%34%
2376
April1st to 10thDay
24%10%47%5%34445%31%
2160
11th to 20thDay
20%9%46%6%34445%35%
2134
21st to endDay
23%8%46%6%345%46%32%
2301
May1st to 10thDay
20%7%46%5%3445%7%34%
2456
11th to 20thDay
18%7%36%6%35%45%6%38%
2478
21st to endDay
17%6%46%5%35%5%6%9%34%
2725
June1st to 10thDay
23%6%36%6%35%5%6%7%30%
2520
11th to 20thDay
15%7%35%5%45%5%6%8%38%
2520
21st to endDay
21%6%36%5%446%5%8%31%
2520
July1st to 10thDay
13%5%36%5%36%5%6%8%40%
2520
11th to 20thDay
13%6%35%5%46%5%7%10%36%
2520
21st to endDay
13%5%36%6%35%6%7%9%37%
2744
August1st to 10thDay
13%5%36%6%46%6%6%8%37%
2506
11th to 20thDay
13%5%25%5%35%6%7%9%41%
2259
21st to endDay
13%6%25%6%45%5%5%8%42%
2376
September1st to 10thDay
13%6%346%345%5%9%43%
2160
11th to 20thDay
15%6%245%34447%47%
2078
21st to endDay
14%6%26%5%345%6%8%41%
1980
October1st to 10thDay
22%6%36%6%45%5%5%7%31%
1871
11th to 20thDay
18%7%36%7%46%6%6%6%30%
1762
21st to endDay
25%13%45%5%34446%27%
1782
November1st to 10thDay
17%11%47%6%4446%5%32%
1671
11th to 20thDay
17%13%5%6%5%446%5%6%28%
1663
21st to endDay
21%13%5%8%7%35%5%5%6%22%
1520
December1st to 10thDay
21%16%6%11%7%3445%6%18%
1520
11th to 20thDay
21%15%6%8%6%25%35%5%23%
1906
21st to endDay
26%15%410%7%4434319%
2772
January1st to 10thNight
17%17%6%10%8%46%445%19%
2649
11th to 20thNight
18%16%6%9%7%5%6%44421%
2660
21st to endNight
13%14%5%10%7%45%5%5%5%27%
2919
February1st to 10thNight
15%14%6%13%8%5%6%5%45%20%
2370
11th to 20thNight
16%10%49%7%5%6%5%5%5%27%
2164
21st to endNight
17%13%5%8%6%36%44430%
1776
March1st to 10thNight
17%14%5%8%7%45%345%28%
2150
11th to 20thNight
18%11%5%8%6%35%44431%
2097
21st to endNight
20%10%36%6%3434435%
1980
April1st to 10thNight
23%10%46%6%4446%430%
1800
11th to 20thNight
25%8%46%5%34445%33%
1775
21st to endNight
20%9%37%6%35%345%34%
1657
May1st to 10thNight
22%9%36%6%34347%34%
1517
11th to 20thNight
18%7%37%5%3446%7%37%
1415
21st to endNight
16%436%5%45%46%8%39%
1550
June1st to 10thNight
23%5%446%45%46%7%31%
1440
11th to 20thNight
18%5%35%5%35%5%7%8%37%
1440
21st to endNight
17%7%26%6%35%5%5%7%36%
1440
July1st to 10thNight
11%5%35%445%5%7%8%43%
1440
11th to 20thNight
10%5%25%5%36%5%8%9%42%
1440
21st to endNight
12%6%25%6%36%46%9%41%
1574
August1st to 10thNight
14%424435%5%6%9%45%
1432
11th to 20thNight
13%7%26%435%5%6%7%43%
1620
21st to endNight
14%5%25%5%4445%8%43%
1980
September1st to 10thNight
12%6%36%6%3446%7%44%
1800
11th to 20thNight
14%6%25%433446%48%
1881
21st to endNight
17%7%3443445%7%42%
1980
October1st to 10thNight
18%8%36%5%345%5%6%37%
2087
11th to 20thNight
20%9%36%6%35%5%6%6%32%
2196
21st to endNight
24%10%47%6%3445%5%28%
2574
November1st to 10thNight
19%9%46%6%345%5%6%32%
2407
11th to 20thNight
19%9%48%6%345%45%32%
2515
21st to endNight
20%13%5%8%6%45%5%5%6%24%
2660
December1st to 10thNight
22%16%7%8%8%35%45%6%17%
2660
11th to 20thNight
23%15%6%9%6%3444423%
3288
21st to endNight
28%14%5%11%6%34435%20%
4884

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
67%7%11%12%3
1518
11th to 20thDay
67%6%9%10%8%
1520
21st to endDay
59%9%12%12%8%1
1664
February1st to 10thDay
67%5%8%14%42
1588
11th to 20thDay
60%7%11%15%7%1
1691
21st to endDay
62%5%11%13%8%1
1480
March1st to 10thDay
59%7%11%13%8%2
1800
11th to 20thDay
54%6%12%15%11%2
1860
21st to endDay
53%5%8%18%12%3
2376
April1st to 10thDay
56%5%8%19%11%2
2160
11th to 20thDay
50%5%8%20%15%2
2134
21st to endDay
54%6%9%16%11%3
2301
May1st to 10thDay
49%6%9%19%16%1
2456
11th to 20thDay
46%7%10%20%15%3
2482
21st to endDay
45%8%13%18%13%2
2725
June1st to 10thDay
52%8%10%18%11%1
2520
11th to 20thDay
43%7%10%23%14%2
2520
21st to endDay
51%8%11%20%9%1
2520
July1st to 10thDay
40%8%12%25%13%1
2450
11th to 20thDay
42%8%13%29%8%
2445
21st to endDay
42%10%14%24%9%1
2591
August1st to 10thDay
43%10%16%24%8%
2492
11th to 20thDay
36%11%17%25%10%
2259
21st to endDay
40%7%14%25%13%1
2376
September1st to 10thDay
38%8%13%27%14%1
2160
11th to 20thDay
38%5%11%33%13%1
2078
21st to endDay
41%8%15%26%9%1
1980
October1st to 10thDay
52%7%12%20%9%
1871
11th to 20thDay
51%9%15%17%8%
1762
21st to endDay
60%6%11%16%7%1
1782
November1st to 10thDay
52%7%13%20%7%1
1671
11th to 20thDay
56%8%12%14%10%1
1663
21st to endDay
61%9%12%13%4
1520
December1st to 10thDay
69%7%11%12%2
1520
11th to 20thDay
63%7%11%14%5%
1906
21st to endDay
69%6%11%10%4
2772
January1st to 10thNight
67%7%10%12%4
2649
11th to 20thNight
67%7%9%11%6%1
2660
21st to endNight
57%7%12%14%10%1
2919
February1st to 10thNight
66%7%8%12%6%1
2370
11th to 20thNight
57%7%10%17%8%
2166
21st to endNight
57%6%9%15%12%1
1776
March1st to 10thNight
59%6%10%15%10%1
2160
11th to 20thNight
57%5%9%16%10%2
2098
21st to endNight
53%5%7%19%12%4
1980
April1st to 10thNight
56%49%18%12%1
1800
11th to 20thNight
54%5%8%19%13%1
1775
21st to endNight
53%7%7%16%13%4
1657
May1st to 10thNight
52%46%17%16%4
1517
11th to 20thNight
45%6%9%18%19%3
1416
21st to endNight
41%10%11%21%15%3
1551
June1st to 10thNight
50%8%11%20%10%1
1440
11th to 20thNight
44%6%13%19%15%2
1440
21st to endNight
46%10%12%20%12%
1440
July1st to 10thNight
35%11%12%24%17%1
1400
11th to 20thNight
34%11%14%29%11%
1392
21st to endNight
39%9%15%24%11%1
1486
August1st to 10thNight
35%10%17%27%11%
1422
11th to 20thNight
39%9%15%23%13%
1620
21st to endNight
38%9%14%25%13%1
1980
September1st to 10thNight
38%9%12%27%14%1
1800
11th to 20thNight
36%7%13%32%11%1
1881
21st to endNight
41%7%12%25%14%1
1980
October1st to 10thNight
47%8%11%22%12%
2087
11th to 20thNight
50%8%11%22%8%
2196
21st to endNight
57%7%12%14%9%1
2574
November1st to 10thNight
52%7%12%18%9%1
2407
11th to 20thNight
54%7%11%18%9%1
2515
21st to endNight
60%8%12%15%5%
2660
December1st to 10thNight
70%7%10%12%2
2660
11th to 20thNight
66%6%9%13%6%
3288
21st to endNight
69%7%9%13%3
4884

Seeing (when cloud cover <= 80%)
Color Meanings:
Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 10thDay
28%23%21%21%7%1
180
11th to 20thDay
31%26%28%12%31
180
21st to endDay
26%19%34%15%6%1
196
February1st to 10thDay
37%23%34%5%
226
11th to 20thDay
27%22%37%12%2
350
21st to endDay
31%18%29%19%3
346
March1st to 10thDay
29%19%31%17%4
420
11th to 20thDay
26%22%31%14%5%1
420
21st to endDay
31%21%24%16%7%
462
April1st to 10thDay
35%16%25%15%7%
420
11th to 20thDay
30%19%26%14%8%3
412
21st to endDay
30%14%31%15%9%1
420
May1st to 10thDay
28%16%32%15%8%1
423
11th to 20thDay
20%17%31%22%8%1
447
21st to endDay
18%15%32%26%8%1
485
June1st to 10thDay
24%16%28%24%7%1
450
11th to 20thDay
17%13%31%26%11%2
450
21st to endDay
22%12%32%22%9%2
450
July1st to 10thDay
16%7%30%29%16%3
445
11th to 20thDay
14%7%35%30%12%3
444
21st to endDay
14%8%30%33%13%2
488
August1st to 10thDay
15%8%28%29%16%4
446
11th to 20thDay
14%7%28%28%17%6%
439
21st to endDay
17%10%28%23%15%6%
495
September1st to 10thDay
14%10%28%27%14%7%
450
11th to 20thDay
16%12%21%26%17%8%
450
21st to endDay
15%14%29%21%16%5%
450
October1st to 10thDay
23%16%23%20%14%5%
450
11th to 20thDay
22%20%28%20%7%2
430
21st to endDay
34%17%25%20%4
396
November1st to 10thDay
26%18%30%20%5%1
365
11th to 20thDay
28%24%28%14%6%1
323
21st to endDay
32%20%26%17%6%1
180
December1st to 10thDay
34%14%26%18%7%1
180
11th to 20thDay
28%23%33%13%3
180
21st to endDay
29%26%28%11%41
198
January1st to 10thNight
25%20%33%18%4
760
11th to 20thNight
25%19%33%19%5%
760
21st to endNight
22%15%35%24%41
835
February1st to 10thNight
23%17%33%22%4
720
11th to 20thNight
23%17%37%20%2
703
21st to endNight
26%16%32%23%4
592
March1st to 10thNight
27%16%30%23%3
720
11th to 20thNight
28%17%30%20%5%
720
21st to endNight
27%16%26%24%6%
792
April1st to 10thNight
28%17%27%24%5%
720
11th to 20thNight
29%16%27%22%6%
711
21st to endNight
24%19%28%21%8%
577
May1st to 10thNight
27%9%29%23%10%
437
11th to 20thNight
21%11%33%26%8%1
354
21st to endNight
17%12%30%30%10%
389
June1st to 10thNight
24%9%28%29%10%1
360
11th to 20thNight
19%9%27%31%13%1
360
21st to endNight
19%7%27%33%14%1
360
July1st to 10thNight
11%5%33%33%18%
350
11th to 20thNight
8%426%44%17%1
348
21st to endNight
13%423%42%16%1
394
August1st to 10thNight
15%418%44%18%1
358
11th to 20thNight
15%423%35%21%2
556
21st to endNight
16%7%22%36%17%2
792
September1st to 10thNight
15%7%26%36%15%1
720
11th to 20thNight
16%8%22%32%19%3
720
21st to endNight
19%8%29%25%17%2
720
October1st to 10thNight
22%12%27%25%14%1
720
11th to 20thNight
24%13%29%25%8%
720
21st to endNight
29%13%32%22%5%
792
November1st to 10thNight
25%19%29%20%7%1
740
11th to 20thNight
24%19%31%17%8%1
760
21st to endNight
29%18%30%17%7%
760
December1st to 10thNight
30%19%29%18%4
760
11th to 20thNight
31%17%30%16%5%1
760
21st to endNight
34%17%30%16%3
836
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