Observatoire Huntingdon
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Observatoire Huntingdon clear sky chart from 2005-11-05 to 2017-10-31.

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
26%
14845
12%
47361
7%
14814
32%
14814
14%
34906

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 15thNight
12%
720
6%
2506
2%
716
17%
716
6%
2075
January16th to endNight
15%
768
8%
2688
3%
768
22%
768
8%
2088
February1st to 15thNight
13%
704
7%
2287
2%
701
19%
701
7%
1873
February16th to endNight
17%
631
11%
1897
4%
631
26%
631
10%
1487
March1st to 15thNight
17%
720
11%
2157
6%
720
23%
720
12%
1673
March16th to endNight
27%
768
18%
1992
8%
768
34%
768
19%
1448
April1st to 15thNight
22%
718
14%
1796
4%
718
28%
718
17%
1382
April16th to endNight
25%
642
15%
1722
6%
642
32%
642
20%
1250
May1st to 15thNight
29%
387
17%
1467
12%
387
41%
387
15%
996
May16th to endNight
32%
374
12%
1497
10%
374
42%
374
15%
991
June1st to 15thNight
29%
360
9%
1440
7%
360
38%
360
12%
1026
June16th to endNight
38%
360
10%
1440
11%
360
45%
360
19%
912
July1st to 15thNight
45%
340
14%
1360
17%
340
54%
340
24%
791
July16th to endNight
44%
376
13%
1418
13%
354
49%
354
23%
841
August1st to 15thNight
49%
383
15%
1454
13%
381
55%
381
22%
898
August16th to endNight
45%
761
19%
1907
9%
761
50%
761
33%
1261
September1st to 15thNight
44%
720
14%
1800
7%
720
45%
720
28%
1246
September16th to endNight
45%
717
22%
1960
15%
717
50%
717
30%
1262
October1st to 15thNight
29%
720
16%
2134
9%
720
37%
720
19%
1496
October16th to endNight
20%
768
9%
2443
5%
768
26%
768
11%
1899
November1st to 15thNight
23%
700
13%
2277
9%
700
30%
700
12%
1707
November16th to endNight
20%
720
10%
2511
7%
720
26%
720
8%
1934
December1st to 15thNight
12%
720
5%
2520
2%
720
17%
720
5%
2106
December16th to endNight
9%
768
7%
2688
2%
768
14%
768
5%
2264

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%36%5%3445%6%31%
48397
Night
18%10%47%5%34445%29%
47530
Cloud CoverDay
18%9%46%5%3445%6%30%
48406
Night
17%11%47%6%3445%6%29%
47536
TransparencyDay
52%6%11%19%9%
48084
Night
55%6%11%17%9%
47361
SeeingDay
23%13%29%20%10%3
5743
Night
23%14%29%23%8%
14846

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 15thDay
20%15%6%10%8%45%43317%
1432
16th to endDay
13%15%6%9%7%3445%7%19%
1536
February1st to 15thDay
14%14%6%12%8%45%5%45%17%
1572
16th to endDay
15%14%5%9%8%35%34424%
1575
March1st to 15thDay
17%14%6%8%7%25%35%426%
1790
16th to endDay
19%11%36%42334437%
2231
April1st to 15thDay
22%11%46%5%3324431%
2152
16th to endDay
20%8%245%23446%36%
2238
May1st to 15thDay
21%6%35%5%2445%5%33%
2493
16th to endDay
19%7%35%5%3445%7%34%
2618
June1st to 15thDay
25%6%25%5%2435%7%30%
2520
16th to endDay
19%5%25%5%46%45%8%31%
2520
July1st to 15thDay
13%6%25%5%25%46%8%38%
2520
16th to endDay
13%425%5%35%6%7%9%35%
2654
August1st to 15thDay
14%5%37%5%35%6%6%8%33%
2486
16th to endDay
11%425%4346%7%8%43%
2292
September1st to 15thDay
16%5%25%423347%43%
2160
16th to endDay
13%5%24423347%46%
1999
October1st to 15thDay
21%7%35%425%45%6%33%
1824
16th to endDay
26%12%36%5%3344425%
1779
November1st to 15thDay
17%10%46%5%25%45%7%29%
1581
16th to endDay
19%15%5%7%6%2443424%
1449
December1st to 15thDay
22%16%5%10%7%24445%15%
1440
16th to endDay
25%17%5%9%6%2434314%
1536
January1st to 15thNight
16%16%6%12%8%4435%316%
2506
16th to endNight
13%16%7%8%7%45%44422%
2688
February1st to 15thNight
14%13%7%14%9%45%34417%
2285
16th to endNight
15%15%6%9%7%35%435%23%
1897
March1st to 15thNight
19%13%46%6%35%33427%
2144
16th to endNight
19%10%46%5%2333436%
1992
April1st to 15thNight
25%9%26%6%34435%29%
1796
16th to endNight
21%7%26%434346%36%
1722
May1st to 15thNight
22%6%36%5%24346%33%
1467
16th to endNight
19%5%35%5%25%5%5%6%34%
1495
June1st to 15thNight
25%7%35%43445%7%28%
1440
16th to endNight
16%5%244345%6%9%37%
1440
July1st to 15thNight
10%425%425%6%7%9%41%
1440
16th to endNight
12%4143445%8%9%41%
1514
August1st to 15thNight
12%435%5%2437%9%40%
1464
16th to endNight
13%42432445%7%46%
1907
September1st to 15thNight
15%5%25%5%2345%6%42%
1800
16th to endNight
17%41332436%6%45%
1960
October1st to 15thNight
19%8%35%5%23446%35%
2134
16th to endNight
25%11%26%5%35%445%25%
2443
November1st to 15thNight
21%10%46%5%3445%5%27%
2277
16th to endNight
21%12%6%8%5%24435%24%
2511
December1st to 15thNight
21%19%6%8%6%25%43416%
2520
16th to endNight
22%18%6%8%7%35%43316%
2688

Percentage Cloud Cover SE (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 15thDay
18%16%6%11%9%35%44316%
1432
16th to endDay
12%15%6%10%8%45%45%7%19%
1536
February1st to 15thDay
12%16%6%13%8%45%45%5%16%
1572
16th to endDay
14%15%6%10%8%35%345%23%
1575
March1st to 15thDay
16%15%6%8%6%3444425%
1800
16th to endDay
18%11%46%423335%35%
2230
April1st to 15thDay
21%12%5%6%433235%31%
2152
16th to endDay
20%9%25%423345%36%
2238
May1st to 15thDay
21%7%35%5%25%45%6%32%
2493
16th to endDay
19%6%35%43446%7%33%
2618
June1st to 15thDay
25%6%35%5%25%346%29%
2520
16th to endDay
19%6%26%5%25%5%6%8%30%
2520
July1st to 15thDay
13%6%35%5%35%5%6%8%37%
2520
16th to endDay
13%425%6%45%5%7%9%34%
2654
August1st to 15thDay
14%6%36%6%46%5%5%8%32%
2486
16th to endDay
11%425%435%6%7%8%41%
2292
September1st to 15thDay
17%5%25%42335%7%41%
2160
16th to endDay
13%5%2442335%7%45%
1999
October1st to 15thDay
20%8%35%6%25%446%32%
1824
16th to endDay
25%12%36%5%33345%25%
1779
November1st to 15thDay
17%10%5%6%5%35%45%7%29%
1581
16th to endDay
18%14%5%8%6%3444424%
1449
December1st to 15thDay
21%17%5%10%7%34445%15%
1440
16th to endDay
24%18%6%9%6%4434313%
1536
January1st to 15thNight
14%16%6%13%8%45%44416%
2506
16th to endNight
12%16%6%9%7%46%44421%
2688
February1st to 15thNight
12%13%7%14%10%45%44417%
2278
16th to endNight
14%15%6%10%7%44445%23%
1897
March1st to 15thNight
19%13%5%7%6%35%335%26%
2157
16th to endNight
18%12%36%43333435%
1992
April1st to 15thNight
24%9%37%5%4343428%
1796
16th to endNight
21%7%25%43335%6%35%
1722
May1st to 15thNight
22%7%26%5%24446%33%
1467
16th to endNight
19%6%35%5%35%5%5%7%33%
1495
June1st to 15thNight
25%7%35%43345%7%28%
1440
16th to endNight
15%5%245%25%5%7%9%36%
1440
July1st to 15thNight
9%425%435%5%8%10%40%
1440
16th to endNight
11%4244246%6%9%40%
1514
August1st to 15thNight
13%5%245%3446%10%39%
1464
16th to endNight
13%42433445%7%46%
1907
September1st to 15thNight
15%6%25%5%34247%42%
1800
16th to endNight
17%42332336%6%45%
1960
October1st to 15thNight
18%8%36%5%3345%6%34%
2134
16th to endNight
25%12%35%5%4345%5%24%
2443
November1st to 15thNight
20%11%46%6%3446%5%26%
2277
16th to endNight
19%13%6%8%5%25%435%24%
2511
December1st to 15thNight
20%19%6%8%7%3443416%
2520
16th to endNight
21%19%6%9%7%35%44315%
2688

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 15thDay
70%5%6%11%4
1433
16th to endDay
62%5%13%11%6%
1536
February1st to 15thDay
66%6%9%14%3
1574
16th to endDay
61%5%10%11%9%1
1575
March1st to 15thDay
61%5%12%12%7%1
1800
16th to endDay
50%49%17%15%3
2231
April1st to 15thDay
56%37%19%11%2
2152
16th to endDay
48%5%9%19%13%3
2238
May1st to 15thDay
50%5%9%17%14%1
2493
16th to endDay
47%7%11%20%12%1
2622
June1st to 15thDay
53%5%11%18%10%
2520
16th to endDay
49%7%12%20%9%
2520
July1st to 15thDay
40%7%14%27%10%
2371
16th to endDay
41%8%16%23%8%
2487
August1st to 15thDay
46%9%15%21%8%
2472
16th to endDay
34%8%18%26%11%
2292
September1st to 15thDay
41%6%11%27%13%
2160
16th to endDay
37%413%32%11%
1999
October1st to 15thDay
50%5%12%21%9%
1824
16th to endDay
61%5%13%14%5%
1779
November1st to 15thDay
53%6%13%17%8%
1581
16th to endDay
62%6%9%14%6%
1449
December1st to 15thDay
69%8%9%9%1
1440
16th to endDay
71%6%9%7%4
1536
January1st to 15thNight
70%5%9%9%4
2506
16th to endNight
62%6%10%13%6%
2688
February1st to 15thNight
68%5%9%12%4
2287
16th to endNight
62%49%13%9%
1897
March1st to 15thNight
60%5%9%15%7%
2157
16th to endNight
52%39%17%12%3
1992
April1st to 15thNight
57%39%16%12%
1796
16th to endNight
49%5%8%18%14%3
1722
May1st to 15thNight
52%46%15%17%3
1467
16th to endNight
47%7%11%19%11%1
1497
June1st to 15thNight
54%7%10%17%9%
1440
16th to endNight
42%8%15%21%12%
1440
July1st to 15thNight
33%9%14%28%14%
1360
16th to endNight
36%8%15%24%13%
1418
August1st to 15thNight
38%8%17%24%10%
1454
16th to endNight
35%7%14%28%13%
1907
September1st to 15thNight
42%7%11%26%12%
1800
16th to endNight
37%6%10%31%13%
1960
October1st to 15thNight
49%5%10%24%10%
2134
16th to endNight
60%7%11%15%4
2443
November1st to 15thNight
56%7%12%13%7%2
2277
16th to endNight
61%6%10%14%5%
2511
December1st to 15thNight
70%6%10%10%1
2520
16th to endNight
71%6%9%9%3
2688

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 15thDay
20%26%25%20%8%
60
16th to endDay
37%14%37%7%3
64
February1st to 15thDay
34%23%34%5%1
89
16th to endDay
27%18%32%17%2
234
March1st to 15thDay
21%22%32%17%5%
270
16th to endDay
29%14%26%18%9%1
288
April1st to 15thDay
28%20%29%14%7%
270
16th to endDay
23%15%28%18%11%2
270
May1st to 15thDay
28%13%29%17%8%2
288
16th to endDay
21%16%32%18%9%1
331
June1st to 15thDay
29%9%32%21%5%1
315
16th to endDay
20%10%34%24%8%1
315
July1st to 15thDay
17%6%33%28%10%4
305
16th to endDay
14%7%28%32%13%3
326
August1st to 15thDay
17%7%28%27%15%4
313
16th to endDay
13%7%29%24%15%9%
332
September1st to 15thDay
17%6%28%20%17%8%
315
16th to endDay
14%11%21%24%20%8%
314
October1st to 15thDay
23%15%22%15%19%2
315
16th to endDay
34%15%26%16%6%
301
November1st to 15thDay
26%16%27%16%12%1
235
16th to endDay
33%23%18%20%4
69
December1st to 15thDay
30%18%30%18%3
60
16th to endDay
45%17%32%4
64
January1st to 15thNight
22%23%35%16%3
720
16th to endNight
22%22%32%18%4
768
February1st to 15thNight
21%20%35%19%3
704
16th to endNight
23%17%34%20%3
631
March1st to 15thNight
27%19%31%18%3
720
16th to endNight
24%15%28%25%6%
768
April1st to 15thNight
28%15%29%23%3
718
16th to endNight
27%13%29%19%8%
642
May1st to 15thNight
23%11%29%24%10%
387
16th to endNight
21%9%30%28%10%
375
June1st to 15thNight
27%8%28%27%7%
360
16th to endNight
17%7%31%30%12%1
360
July1st to 15thNight
10%7%30%34%15%
340
16th to endNight
13%332%36%12%1
376
August1st to 15thNight
14%424%37%17%1
383
16th to endNight
14%6%26%31%19%
761
September1st to 15thNight
17%7%26%35%11%2
720
16th to endNight
18%8%23%26%20%2
717
October1st to 15thNight
24%13%26%21%12%1
720
16th to endNight
30%15%27%19%6%
768
November1st to 15thNight
25%16%28%20%8%
700
16th to endNight
26%21%23%17%10%
720
December1st to 15thNight
32%21%27%14%3
720
16th to endNight
31%21%29%12%31
768
Page generated at 2017-11-01 17:23:35. Version ac04

Copyright 2017 A. Danko


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