Moss Rock Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Moss Rock Observatory clear sky chart from 2005-11-05 to 2019-06-02.

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
44%
18314
27%
53834
14%
18271
56%
18271
38%
28869

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
29%
1049
31%
2926
12%
1045
47%
1045
37%
1509
January16th to endNight
22%
935
33%
2951
11%
935
47%
935
35%
1451
February1st to 15thNight
20%
819
27%
2647
7%
818
43%
818
28%
1390
February16th to endNight
23%
736
30%
2206
6%
736
48%
736
33%
1186
March1st to 15thNight
34%
840
30%
2454
11%
840
50%
840
39%
1299
March16th to endNight
37%
802
26%
2370
10%
802
52%
802
36%
1319
April1st to 15thNight
33%
629
24%
2098
11%
629
50%
629
32%
1123
April16th to endNight
35%
624
21%
2079
12%
624
49%
624
29%
1200
May1st to 15thNight
46%
630
19%
1860
13%
630
53%
630
27%
1193
May16th to endNight
56%
659
17%
1754
12%
657
61%
657
37%
1059
June1st to 15thNight
67%
588
23%
1568
17%
588
71%
588
50%
828
June16th to endNight
75%
585
27%
1560
22%
585
78%
585
58%
784
July1st to 15thNight
75%
555
20%
1480
16%
555
77%
555
40%
866
July16th to endNight
81%
612
24%
1582
22%
579
81%
579
45%
870
August1st to 15thNight
79%
575
21%
1763
22%
572
80%
572
44%
909
August16th to endNight
75%
621
27%
2070
31%
621
77%
621
40%
1067
September1st to 15thNight
70%
585
29%
1950
28%
585
76%
585
40%
1002
September16th to endNight
67%
587
34%
2088
30%
587
76%
587
46%
945
October1st to 15thNight
46%
780
28%
2340
15%
780
57%
780
39%
1291
October16th to endNight
42%
858
32%
2522
15%
858
55%
858
40%
1340
November1st to 15thNight
38%
1025
33%
2665
13%
1025
51%
1025
45%
1433
November16th to endNight
32%
1050
33%
2825
10%
1050
49%
1050
47%
1443
December1st to 15thNight
25%
1050
26%
2940
7%
1050
43%
1050
35%
1590
December16th to endNight
27%
1120
26%
3136
7%
1120
43%
1120
32%
1772

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
5%5%244245%6%8%50%
54519
Night
342332345%8%58%
54010
TransparencyDay
29%6%13%24%19%6%
54197
Night
24%5%13%27%22%7%
53834
SeeingDay
10%9%34%28%13%4
8090
Night
9%9%32%30%15%2
18320

By Month

Percentage Cloud Cover SW (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
5%44324449%56%
1672
16th to endDay
1435%41335%7%59%
1988
February1st to 15thDay
436%32345%9%56%
1874
16th to endDay
6%35%32435%8%56%
1840
March1st to 15thDay
2426%4245%5%8%53%
2164
16th to endDay
49%3432446%11%45%
2558
April1st to 15thDay
6%7%2342446%9%48%
2510
16th to endDay
11%9%25%435%5%6%7%39%
2486
May1st to 15thDay
11%9%345%35%5%5%8%37%
2746
16th to endDay
12%6%24436%6%6%10%37%
3064
June1st to 15thDay
5%314426%6%7%9%48%
2746
16th to endDay
33135%26%5%8%8%51%
2730
July1st to 15thDay
8%424436%6%6%9%43%
2730
16th to endDay
5%4245%36%6%7%10%41%
2836
August1st to 15thDay
6%5%245%45%7%7%9%41%
2441
16th to endDay
6%4145%35%6%6%9%45%
2484
September1st to 15thDay
6%3144245%6%7%53%
2340
16th to endDay
6%413323335%61%
2199
October1st to 15thDay
6%6%13324447%54%
1950
16th to endDay
5%5%22213246%61%
2041
November1st to 15thDay
141331335%8%62%
1853
16th to endDay
243422235%8%60%
1795
December1st to 15thDay
1425%42346%8%56%
1680
16th to endDay
2425%32335%9%57%
1792
January1st to 15thNight
414323349%62%
2926
16th to endNight
15%24323337%62%
2951
February1st to 15thNight
5%2432445%7%59%
2637
16th to endNight
5%35%324346%59%
2206
March1st to 15thNight
141332245%9%59%
2454
16th to endNight
45%2332335%7%57%
2370
April1st to 15thNight
37%2322345%8%54%
2098
16th to endNight
10%8%24213446%50%
2079
May1st to 15thNight
12%7%243235%6%8%43%
1859
16th to endNight
8%5%2332445%8%51%
1753
June1st to 15thNight
3221145%5%8%62%
1568
16th to endNight
31111245%10%64%
1560
July1st to 15thNight
5%2134245%7%9%52%
1560
16th to endNight
4212335%46%9%54%
1681
August1st to 15thNight
42133235%5%9%57%
1772
16th to endNight
5%21443446%8%54%
2070
September1st to 15thNight
7%31332435%7%57%
1950
16th to endNight
5%212313445%65%
2088
October1st to 15thNight
6%5%23213436%59%
2340
16th to endNight
46%23313336%60%
2522
November1st to 15thNight
1413312347%64%
2665
16th to endNight
2313313347%65%
2825
December1st to 15thNight
15%2441335%8%59%
2940
16th to endNight
1435%32445%8%55%
3136

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
24%5%16%31%17%5%
1673
16th to endDay
23%313%33%19%5%
1988
February1st to 15thDay
25%7%18%31%14%3
1875
16th to endDay
25%412%30%24%3
1840
March1st to 15thDay
27%414%28%20%4
2164
16th to endDay
30%7%13%28%16%3
2558
April1st to 15thDay
30%7%13%27%15%6%
2510
16th to endDay
40%7%14%21%13%2
2486
May1st to 15thDay
42%8%13%22%11%1
2746
16th to endDay
40%8%16%19%11%4
3068
June1st to 15thDay
27%9%14%18%18%10%
2746
16th to endDay
24%7%12%21%25%9%
2730
July1st to 15thDay
33%8%13%17%17%10%
2581
16th to endDay
30%10%15%24%13%5%
2672
August1st to 15thDay
34%10%14%18%14%7%
2426
16th to endDay
28%8%13%22%21%5%
2484
September1st to 15thDay
26%5%12%22%20%12%
2340
16th to endDay
24%48%25%32%5%
2199
October1st to 15thDay
28%6%11%19%27%6%
1950
16th to endDay
22%311%28%26%7%
2041
November1st to 15thDay
20%5%14%26%24%8%
1853
16th to endDay
20%310%29%28%7%
1795
December1st to 15thDay
24%5%17%29%19%3
1680
16th to endDay
24%6%15%28%21%3
1792
January1st to 15thNight
20%415%32%22%5%
2926
16th to endNight
22%312%31%23%6%
2951
February1st to 15thNight
24%6%16%31%18%3
2647
16th to endNight
25%49%29%23%7%
2206
March1st to 15thNight
21%6%10%31%25%4
2454
16th to endNight
26%5%12%30%20%3
2370
April1st to 15thNight
27%6%13%27%19%5%
2098
16th to endNight
33%5%12%27%17%3
2079
May1st to 15thNight
38%7%13%22%15%2
1860
16th to endNight
29%7%20%22%15%4
1754
June1st to 15thNight
20%5%17%25%17%14%
1568
16th to endNight
14%6%11%23%29%14%
1560
July1st to 15thNight
25%8%14%21%18%10%
1480
16th to endNight
22%7%17%29%15%8%
1582
August1st to 15thNight
21%7%19%24%18%8%
1763
16th to endNight
25%5%13%24%24%7%
2070
September1st to 15thNight
24%5%13%22%18%15%
1950
16th to endNight
19%311%25%31%8%
2088
October1st to 15thNight
25%5%12%19%27%8%
2340
16th to endNight
24%39%25%27%8%
2522
November1st to 15thNight
19%410%28%25%10%
2665
16th to endNight
18%412%28%29%7%
2825
December1st to 15thNight
23%416%29%19%6%
2940
16th to endNight
26%6%16%28%19%2
3136

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
9%6%37%32%10%4
180
16th to endDay
5%15%47%27%4
192
February1st to 15thDay
13%21%43%19%1
180
16th to endDay
6%13%51%25%3
159
March1st to 15thDay
10%16%46%22%4
244
16th to endDay
14%21%41%18%4
416
April1st to 15thDay
13%21%41%18%41
389
16th to endDay
18%14%38%20%6%1
378
May1st to 15thDay
17%7%35%27%10%2
554
16th to endDay
18%6%30%24%15%3
677
June1st to 15thDay
5%5%30%31%20%6%
576
16th to endDay
5%432%30%18%7%
570
July1st to 15thDay
9%220%32%24%9%
550
16th to endDay
6%219%34%27%9%
551
August1st to 15thDay
7%434%36%13%3
359
16th to endDay
6%430%39%15%3
396
September1st to 15thDay
7%434%34%13%5%
375
16th to endDay
7%6%34%35%14%2
240
October1st to 15thDay
14%7%33%27%11%4
180
16th to endDay
9%10%33%32%9%4
192
November1st to 15thDay
6%10%36%27%15%3
180
16th to endDay
10%16%42%26%22
180
December1st to 15thDay
8%20%44%21%5%
180
16th to endDay
6%13%46%26%6%
192
January1st to 15thNight
11%15%38%23%8%1
1050
16th to endNight
11%17%44%19%6%1
935
February1st to 15thNight
10%17%47%19%5%
824
16th to endNight
8%15%46%24%4
736
March1st to 15thNight
6%12%42%28%7%1
840
16th to endNight
9%11%39%32%6%1
802
April1st to 15thNight
10%9%41%30%7%
629
16th to endNight
14%9%34%28%12%1
624
May1st to 15thNight
16%327%35%13%2
630
16th to endNight
11%322%36%22%3
659
June1st to 15thNight
6%121%44%22%3
588
16th to endNight
316%43%33%2
585
July1st to 15thNight
6%9%31%43%7%
555
16th to endNight
5%433%47%8%
612
August1st to 15thNight
5%7%38%42%5%
575
16th to endNight
6%9%38%35%9%
621
September1st to 15thNight
8%113%35%31%9%
585
16th to endNight
5%317%43%21%7%
587
October1st to 15thNight
10%7%31%32%13%3
780
16th to endNight
9%10%32%30%12%4
858
November1st to 15thNight
7%12%38%31%9%1
1025
16th to endNight
7%12%44%27%6%
1050
December1st to 15thNight
11%14%42%25%4
1050
16th to endNight
8%16%41%25%7%1
1120
Page generated at 2019-06-02 17:43:11. Version ac04

Copyright 2019 A. Danko


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