Monkton Observing Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Monkton Observing Site clear sky chart from 2005-11-05 to 2017-12-20.

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
33%
15423
14%
47876
9%
15385
38%
15385
18%
34302

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
14%
828
8%
2511
3%
826
18%
826
7%
2100
January16th to endNight
13%
768
8%
2496
3%
768
18%
768
7%
2093
February1st to 15thNight
15%
701
6%
2287
2%
701
20%
701
8%
1891
February16th to endNight
20%
631
10%
1967
5%
631
27%
631
12%
1516
March1st to 15thNight
22%
720
13%
2011
7%
720
28%
720
16%
1519
March16th to endNight
31%
768
20%
2112
10%
768
39%
768
22%
1480
April1st to 15thNight
27%
681
15%
1825
6%
681
33%
681
20%
1334
April16th to endNight
36%
540
20%
1620
9%
540
44%
540
24%
1063
May1st to 15thNight
40%
540
17%
1620
11%
540
46%
540
24%
1081
May16th to endNight
45%
398
17%
1521
13%
398
56%
398
26%
854
June1st to 15thNight
47%
360
14%
1368
16%
360
54%
360
26%
799
June16th to endNight
52%
360
16%
1260
16%
360
58%
360
30%
723
July1st to 15thNight
62%
350
20%
1209
23%
350
67%
350
39%
624
July16th to endNight
61%
564
16%
1595
13%
531
64%
531
34%
940
August1st to 15thNight
66%
539
18%
1609
15%
536
68%
536
35%
946
August16th to endNight
60%
582
23%
1728
16%
582
64%
582
33%
1039
September1st to 15thNight
55%
720
20%
1878
13%
720
57%
720
34%
1197
September16th to endNight
55%
717
22%
1980
16%
717
58%
717
33%
1226
October1st to 15thNight
41%
720
17%
2142
14%
720
47%
720
22%
1471
October16th to endNight
23%
768
13%
2325
8%
768
31%
768
15%
1757
November1st to 15thNight
32%
760
17%
2537
15%
760
38%
760
17%
1778
November16th to endNight
21%
780
9%
2730
7%
780
25%
780
11%
2111
December1st to 15thNight
13%
780
5%
2730
3%
780
17%
780
6%
2330
December16th to endNight
11%
848
6%
2815
1%
848
16%
848
5%
2430

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
15%10%47%6%3445%7%29%
48948
Night
15%10%5%8%6%3445%6%30%
48049
Cloud CoverDay
15%10%47%6%35%45%7%29%
48958
Night
15%10%5%8%6%34446%30%
48053
TransparencyDay
53%411%19%9%
48641
Night
53%310%19%10%1
47876
SeeingDay
20%7%25%24%15%6%
5970
Night
20%9%28%28%11%1
15430

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
18%16%6%14%8%4444412%
1418
16th to endDay
12%17%10%14%10%5%5%345%10%
1728
February1st to 15thDay
14%17%8%14%10%5%443412%
1575
16th to endDay
14%15%8%11%8%35%5%5%5%16%
1503
March1st to 15thDay
14%13%6%10%8%35%435%23%
1937
16th to endDay
14%10%6%8%6%35%445%29%
2112
April1st to 15thDay
20%12%5%5%43345%6%28%
2134
16th to endDay
18%9%35%42335%7%36%
2340
May1st to 15thDay
18%8%34434447%35%
2331
16th to endDay
14%6%25%5%345%5%8%38%
2593
June1st to 15thDay
14%6%25%6%35%46%8%36%
2589
16th to endDay
14%6%25%5%35%5%6%8%36%
2700
July1st to 15thDay
10%434435%6%7%7%41%
2675
16th to endDay
10%6%25%5%36%5%6%10%37%
2465
August1st to 15thDay
10%5%25%7%46%6%7%9%33%
2340
16th to endDay
12%6%25%5%45%5%6%9%36%
2461
September1st to 15thDay
14%6%36%5%35%5%5%8%35%
2082
16th to endDay
16%6%15%5%2345%7%39%
1980
October1st to 15thDay
22%8%26%5%3445%5%31%
1818
16th to endDay
26%12%37%6%35%35%5%20%
1896
November1st to 15thDay
15%12%38%7%3445%6%28%
1649
16th to endDay
17%17%7%9%8%4446%5%15%
1560
December1st to 15thDay
16%18%12%14%8%3433310%
1560
16th to endDay
18%21%10%13%7%333349%
1502
January1st to 15thNight
20%15%6%10%8%5%445%413%
2511
16th to endNight
14%15%10%14%9%45%43413%
2496
February1st to 15thNight
14%16%8%11%9%45%43416%
2285
16th to endNight
16%11%6%11%8%35%5%5%6%19%
1967
March1st to 15thNight
16%10%5%10%6%3446%6%26%
1999
16th to endNight
13%10%5%6%5%34345%37%
2112
April1st to 15thNight
19%10%35%5%35%35%6%31%
1825
16th to endNight
13%7%46%5%34447%39%
1620
May1st to 15thNight
16%7%25%5%25%45%8%36%
1620
16th to endNight
10%5%15%43446%7%45%
1519
June1st to 15thNight
12%5%24425%46%9%41%
1368
16th to endNight
10%5%14434449%45%
1260
July1st to 15thNight
5%41431435%8%55%
1279
16th to endNight
8%3245%245%6%8%47%
1703
August1st to 15thNight
7%415%5%345%7%8%45%
1620
16th to endNight
9%6%25%424246%50%
1728
September1st to 15thNight
13%424423447%46%
1878
16th to endNight
12%5%245%245%5%6%46%
1980
October1st to 15thNight
16%7%36%6%34446%35%
2142
16th to endNight
23%10%36%7%3345%5%25%
2325
November1st to 15thNight
15%10%37%6%35%45%7%29%
2537
16th to endNight
19%14%6%8%6%34347%19%
2730
December1st to 15thNight
17%20%9%12%6%3444412%
2730
16th to endNight
20%16%10%13%7%35%4349%
2815

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
19%16%7%13%8%35%44413%
1418
16th to endDay
12%17%10%14%9%6%5%34410%
1728
February1st to 15thDay
14%18%8%13%10%5%5%43412%
1575
16th to endDay
14%15%8%11%7%35%45%5%16%
1503
March1st to 15thDay
15%13%6%10%8%44445%23%
1948
16th to endDay
14%9%7%8%6%35%445%29%
2111
April1st to 15thDay
19%12%5%6%43345%7%27%
2134
16th to endDay
19%9%35%42345%7%36%
2340
May1st to 15thDay
19%7%25%435%448%34%
2331
16th to endDay
14%6%25%4345%5%9%37%
2593
June1st to 15thDay
14%6%26%5%35%5%6%9%36%
2589
16th to endDay
14%7%25%5%25%5%6%9%36%
2700
July1st to 15thDay
10%5%25%436%5%7%8%40%
2675
16th to endDay
9%6%36%445%6%6%9%37%
2465
August1st to 15thDay
9%6%36%6%46%6%7%9%34%
2340
16th to endDay
13%6%25%5%45%5%7%8%36%
2461
September1st to 15thDay
14%6%36%5%35%5%5%8%34%
2082
16th to endDay
16%6%2442445%7%39%
1980
October1st to 15thDay
22%8%27%434445%31%
1818
16th to endDay
27%11%37%6%2445%5%21%
1896
November1st to 15thDay
16%13%37%7%34446%28%
1649
16th to endDay
18%17%6%9%7%4445%6%16%
1560
December1st to 15thDay
16%19%12%13%8%3443410%
1560
16th to endDay
18%22%10%13%7%2442310%
1502
January1st to 15thNight
20%15%6%10%8%45%44413%
2511
16th to endNight
14%15%10%14%8%45%44413%
2496
February1st to 15thNight
14%15%8%11%9%46%445%16%
2278
16th to endNight
16%11%6%11%8%345%5%7%19%
1967
March1st to 15thNight
17%10%5%9%6%3445%6%26%
2011
16th to endNight
14%9%5%6%5%34345%37%
2112
April1st to 15thNight
19%9%36%435%35%5%31%
1825
16th to endNight
13%8%26%5%34437%39%
1620
May1st to 15thNight
16%7%345%35%45%7%37%
1619
16th to endNight
10%4245%345%5%8%45%
1519
June1st to 15thNight
12%5%24425%5%5%9%41%
1368
16th to endNight
11%41443445%9%45%
1260
July1st to 15thNight
5%32432445%9%55%
1279
16th to endNight
8%325%435%46%8%47%
1703
August1st to 15thNight
7%4245%245%8%8%46%
1620
16th to endNight
10%5%24424336%50%
1728
September1st to 15thNight
13%42442345%6%47%
1878
16th to endNight
12%4244245%5%7%46%
1980
October1st to 15thNight
16%6%36%5%34446%36%
2142
16th to endNight
23%9%37%6%3445%6%24%
2325
November1st to 15thNight
16%10%36%6%25%45%7%29%
2537
16th to endNight
19%14%6%8%6%35%346%20%
2730
December1st to 15thNight
17%20%8%12%6%3444412%
2730
16th to endNight
19%17%9%13%7%44435%9%
2815

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
74%48%9%2
1419
16th to endDay
76%36%9%4
1728
February1st to 15thDay
75%36%11%2
1577
16th to endDay
67%39%13%5%
1503
March1st to 15thDay
63%311%14%7%
1948
16th to endDay
56%310%17%10%1
2112
April1st to 15thDay
54%410%20%9%
2134
16th to endDay
47%312%20%13%1
2340
May1st to 15thDay
48%310%25%11%
2331
16th to endDay
43%314%23%13%1
2597
June1st to 15thDay
44%413%25%11%
2589
16th to endDay
43%5%13%25%11%
2700
July1st to 15thDay
38%411%27%17%1
2518
16th to endDay
40%5%14%26%11%2
2310
August1st to 15thDay
43%415%22%11%1
2327
16th to endDay
42%415%24%11%1
2461
September1st to 15thDay
44%5%14%23%10%1
2082
16th to endDay
43%312%29%10%
1980
October1st to 15thDay
54%310%17%12%1
1818
16th to endDay
64%313%12%5%
1896
November1st to 15thDay
56%5%12%18%7%
1649
16th to endDay
68%410%11%4
1560
December1st to 15thDay
77%48%8%1
1560
16th to endDay
79%36%9%1
1502
January1st to 15thNight
72%38%10%4
2511
16th to endNight
73%38%10%3
2496
February1st to 15thNight
70%48%12%3
2287
16th to endNight
62%312%13%7%
1967
March1st to 15thNight
57%411%19%6%
2011
16th to endNight
50%38%22%13%2
2112
April1st to 15thNight
52%48%20%13%
1825
16th to endNight
45%38%20%18%3
1620
May1st to 15thNight
46%210%23%14%2
1620
16th to endNight
36%314%28%13%3
1521
June1st to 15thNight
38%411%28%16%1
1368
16th to endNight
35%415%27%16%1
1260
July1st to 15thNight
26%411%32%22%2
1209
16th to endNight
34%315%25%18%2
1595
August1st to 15thNight
32%5%16%30%13%1
1609
16th to endNight
35%410%31%17%1
1728
September1st to 15thNight
37%311%30%14%1
1878
16th to endNight
36%5%13%30%14%
1980
October1st to 15thNight
48%48%23%14%
2142
16th to endNight
58%413%16%7%
2325
November1st to 15thNight
52%411%20%8%1
2537
16th to endNight
64%312%14%4
2730
December1st to 15thNight
75%49%8%2
2730
16th to endNight
77%38%8%2
2815

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%16%46%9%6%
77
16th to endDay
29%17%30%22%
96
February1st to 15thDay
24%17%46%10%1
90
16th to endDay
23%18%40%14%2
81
March1st to 15thDay
25%9%35%20%8%
238
16th to endDay
23%7%30%24%11%3
288
April1st to 15thDay
25%9%30%21%10%2
270
16th to endDay
22%8%30%21%10%6%
270
May1st to 15thDay
26%6%26%21%12%6%
288
16th to endDay
18%5%28%24%17%6%
331
June1st to 15thDay
17%6%23%31%17%2
384
16th to endDay
17%7%25%30%13%4
495
July1st to 15thDay
15%421%27%22%8%
464
16th to endDay
11%122%31%22%11%
326
August1st to 15thDay
12%117%28%23%17%
313
16th to endDay
18%414%23%20%18%
332
September1st to 15thDay
11%416%26%27%14%
315
16th to endDay
16%419%22%22%14%
314
October1st to 15thDay
22%5%25%26%15%4
315
16th to endDay
30%10%30%22%5%
312
November1st to 15thDay
23%11%28%23%10%2
119
16th to endDay
26%20%36%8%6%1
90
December1st to 15thDay
26%26%25%18%2
90
16th to endDay
36%19%37%6%
72
January1st to 15thNight
26%16%33%17%41
831
16th to endNight
23%12%35%22%5%
768
February1st to 15thNight
22%13%36%22%4
704
16th to endNight
23%11%34%24%6%
631
March1st to 15thNight
22%13%34%22%6%
720
16th to endNight
20%8%33%26%11%
768
April1st to 15thNight
25%10%31%24%7%
681
16th to endNight
17%8%30%32%8%1
540
May1st to 15thNight
20%5%26%30%15%1
540
16th to endNight
14%328%36%16%
399
June1st to 15thNight
15%326%37%16%
360
16th to endNight
15%125%41%14%1
360
July1st to 15thNight
7%20%46%23%1
350
16th to endNight
9%117%46%21%1
564
August1st to 15thNight
9%212%43%28%3
539
16th to endNight
13%216%36%25%5%
582
September1st to 15thNight
15%419%33%21%6%
720
16th to endNight
14%418%32%23%6%
717
October1st to 15thNight
21%425%30%15%2
720
16th to endNight
28%10%30%23%5%
768
November1st to 15thNight
21%9%29%28%9%1
760
16th to endNight
26%15%28%23%6%
780
December1st to 15thNight
27%18%32%17%4
780
16th to endNight
28%14%34%17%3
848
Page generated at 2017-12-21 07:04:54. Version ac04

Copyright 2017 A. Danko


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