Roscommon
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Roscommon clear sky chart from 2005-11-05 to 2017-03-24.

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
29%
15211
12%
45344
7%
15169
34%
15169
17%
33256

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%
900
6%
2506
2%
895
16%
895
7%
2170
January16th to endNight
14%
960
6%
2688
2%
960
18%
960
9%
2270
February1st to 15thNight
13%
713
7%
2267
3%
713
18%
713
7%
1856
February16th to endNight
19%
631
9%
1893
4%
631
24%
631
9%
1539
March1st to 15thNight
23%
720
15%
2112
7%
720
30%
720
17%
1516
March16th to endNight
27%
734
18%
2029
9%
734
35%
734
23%
1386
April1st to 15thNight
25%
494
15%
1625
8%
494
33%
494
16%
1148
April16th to endNight
32%
495
18%
1485
7%
495
41%
495
24%
985
May1st to 15thNight
32%
495
14%
1485
7%
495
40%
495
20%
1031
May16th to endNight
42%
514
14%
1416
6%
513
49%
513
28%
926
June1st to 15thNight
39%
344
15%
1169
11%
344
46%
344
23%
738
June16th to endNight
47%
353
12%
1178
9%
353
52%
353
26%
725
July1st to 15thNight
58%
465
16%
1240
11%
465
61%
465
40%
731
July16th to endNight
53%
522
14%
1305
9%
489
56%
489
36%
808
August1st to 15thNight
58%
494
19%
1462
14%
491
64%
491
36%
847
August16th to endNight
57%
525
19%
1611
15%
525
60%
525
32%
956
September1st to 15thNight
49%
575
19%
1730
15%
575
54%
575
30%
1062
September16th to endNight
47%
657
17%
1815
12%
657
50%
657
29%
1192
October1st to 15thNight
35%
660
18%
1881
11%
660
42%
660
22%
1308
October16th to endNight
21%
704
10%
2266
7%
704
27%
704
13%
1715
November1st to 15thNight
26%
700
15%
2276
11%
700
33%
700
16%
1628
November16th to endNight
16%
720
8%
2424
4%
720
21%
720
8%
1970
December1st to 15thNight
11%
876
4%
2676
1%
876
15%
876
6%
2319
December16th to endNight
12%
960
5%
2805
1%
960
15%
960
6%
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%6%30%
45588
Night
14%10%47%6%3445%6%30%
45512
Cloud CoverDay
15%10%47%6%3445%6%30%
45597
Night
14%10%47%6%3445%6%30%
45517
TransparencyDay
53%6%12%17%9%
45274
Night
52%6%12%18%8%
45344
SeeingDay
18%13%31%21%10%4
5191
Night
19%12%32%25%9%1
15215

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
16%16%8%13%9%45%44313%
1432
16th to endDay
12%16%11%14%9%5%5%44311%
1536
February1st to 15thDay
12%15%8%12%12%4443316%
1595
16th to endDay
11%17%9%12%10%4344417%
1580
March1st to 15thDay
14%11%49%7%35%445%27%
1837
16th to endDay
14%11%5%8%5%3445%5%30%
2050
April1st to 15thDay
20%12%45%433345%30%
1992
16th to endDay
17%10%345%24446%35%
2145
May1st to 15thDay
19%7%36%5%3445%6%31%
2136
16th to endDay
12%5%25%5%35%45%7%42%
2345
June1st to 15thDay
15%6%25%5%346%6%8%35%
2457
16th to endDay
13%436%5%35%5%6%9%37%
2448
July1st to 15thDay
10%5%245%46%5%6%9%39%
2310
16th to endDay
10%5%35%5%35%5%7%10%37%
2459
August1st to 15thDay
9%5%25%5%35%6%6%10%39%
2159
16th to endDay
14%6%25%5%3445%7%40%
2239
September1st to 15thDay
16%5%2443445%8%39%
1889
16th to endDay
14%6%25%5%345%6%8%36%
1815
October1st to 15thDay
22%9%36%5%24345%33%
1749
16th to endDay
23%14%38%7%35%35%6%17%
1603
November1st to 15thDay
17%12%46%5%35%45%7%28%
1582
16th to endDay
20%20%7%10%6%23336%17%
1533
December1st to 15thDay
18%17%8%12%8%4434413%
1281
16th to endDay
21%19%10%12%7%2333311%
1416
January1st to 15thNight
18%14%7%12%9%5%443314%
2506
16th to endNight
12%15%7%13%8%46%45%6%15%
2688
February1st to 15thNight
12%14%8%11%10%45%5%4418%
2265
16th to endNight
14%15%5%12%8%35%5%3419%
1893
March1st to 15thNight
14%9%5%8%5%25%345%34%
2099
16th to endNight
12%10%45%42445%6%38%
2029
April1st to 15thNight
20%10%46%32445%5%31%
1625
16th to endNight
15%9%25%423446%40%
1485
May1st to 15thNight
14%7%25%6%45%6%5%7%34%
1485
16th to endNight
12%5%244346%6%7%41%
1414
June1st to 15thNight
13%5%25%425%46%7%41%
1169
16th to endNight
8%5%25%5%35%46%9%44%
1178
July1st to 15thNight
7%4143245%7%8%50%
1320
16th to endNight
6%4244235%5%9%48%
1401
August1st to 15thNight
6%4144345%5%8%51%
1471
16th to endNight
10%42442345%7%50%
1611
September1st to 15thNight
13%425%323445%49%
1730
16th to endNight
12%6%25%5%2445%7%42%
1815
October1st to 15thNight
19%9%25%423346%37%
1881
16th to endNight
23%11%37%5%2345%6%26%
2266
November1st to 15thNight
13%11%37%5%35%5%48%30%
2276
16th to endNight
19%19%6%8%5%3444419%
2424
December1st to 15thNight
18%15%7%10%7%45%45%413%
2676
16th to endNight
20%17%9%11%6%35%34413%
2805

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
16%16%7%13%9%4444413%
1432
16th to endDay
11%17%11%14%9%46%43411%
1536
February1st to 15thDay
12%16%8%12%12%45%44316%
1595
16th to endDay
11%16%9%11%9%5%444418%
1580
March1st to 15thDay
15%10%48%8%36%5%45%27%
1847
16th to endDay
14%11%5%8%6%3445%5%30%
2049
April1st to 15thDay
20%12%45%433345%30%
1992
16th to endDay
17%10%25%5%24447%35%
2145
May1st to 15thDay
19%8%36%5%3436%6%32%
2136
16th to endDay
12%5%25%5%25%45%7%42%
2345
June1st to 15thDay
15%6%25%5%35%6%6%8%34%
2457
16th to endDay
12%5%36%435%5%6%8%37%
2448
July1st to 15thDay
9%5%246%45%5%6%9%39%
2310
16th to endDay
10%5%35%5%35%5%7%9%37%
2459
August1st to 15thDay
8%5%35%6%35%5%6%10%38%
2159
16th to endDay
13%7%26%5%245%5%7%39%
2239
September1st to 15thDay
15%6%245%35%448%39%
1889
16th to endDay
14%6%35%5%35%5%5%8%36%
1815
October1st to 15thDay
20%9%36%5%24345%33%
1749
16th to endDay
24%13%39%7%3445%6%17%
1603
November1st to 15thDay
17%13%36%5%3345%7%28%
1582
16th to endDay
20%20%6%8%6%24335%17%
1533
December1st to 15thDay
18%16%8%12%7%4444413%
1281
16th to endDay
21%19%10%12%7%2332410%
1416
January1st to 15thNight
19%14%7%12%8%5%5%44414%
2506
16th to endNight
12%15%8%12%8%46%45%7%15%
2688
February1st to 15thNight
12%14%8%10%9%45%5%4418%
2258
16th to endNight
14%15%5%12%8%45%44420%
1893
March1st to 15thNight
14%10%5%7%6%25%345%34%
2112
16th to endNight
12%10%45%43445%6%39%
2029
April1st to 15thNight
19%10%47%41446%5%31%
1625
16th to endNight
15%9%25%324346%40%
1485
May1st to 15thNight
13%6%26%6%45%5%5%8%33%
1484
16th to endNight
11%5%24435%6%6%8%41%
1414
June1st to 15thNight
13%5%36%42445%8%41%
1169
16th to endNight
8%5%245%35%5%6%8%45%
1178
July1st to 15thNight
6%4243245%6%9%50%
1320
16th to endNight
5%435%4245%6%9%48%
1401
August1st to 15thNight
6%4144245%47%52%
1471
16th to endNight
9%42442345%7%50%
1611
September1st to 15thNight
13%5%25%32335%5%49%
1730
16th to endNight
12%6%25%5%3435%8%42%
1815
October1st to 15thNight
18%8%26%5%23246%37%
1881
16th to endNight
23%10%37%5%3345%6%25%
2266
November1st to 15thNight
13%11%37%5%35%45%8%30%
2276
16th to endNight
19%18%6%8%5%33445%19%
2424
December1st to 15thNight
18%15%8%10%8%35%45%5%14%
2676
16th to endNight
19%17%9%10%6%45%44413%
2805

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
73%5%9%9%2
1433
16th to endDay
76%5%7%7%2
1536
February1st to 15thDay
72%6%8%10%3
1597
16th to endDay
69%49%12%3
1580
March1st to 15thDay
56%6%12%16%6%
1847
16th to endDay
54%5%12%18%7%1
2050
April1st to 15thDay
55%410%18%10%
1992
16th to endDay
48%5%13%14%15%2
2145
May1st to 15thDay
51%6%11%20%8%1
2136
16th to endDay
40%7%12%25%13%1
2349
June1st to 15thDay
45%7%12%21%11%
2457
16th to endDay
41%8%16%20%12%
2448
July1st to 15thDay
38%7%11%24%16%1
2161
16th to endDay
40%8%15%20%13%1
2292
August1st to 15thDay
38%8%15%23%12%
2144
16th to endDay
41%6%14%22%12%2
2239
September1st to 15thDay
42%7%12%24%11%1
1889
16th to endDay
42%7%17%22%9%
1815
October1st to 15thDay
53%5%10%21%8%
1749
16th to endDay
66%6%13%9%3
1603
November1st to 15thDay
54%6%13%18%6%
1582
16th to endDay
70%6%9%9%3
1533
December1st to 15thDay
74%5%9%7%1
1281
16th to endDay
78%5%8%6%1
1416
January1st to 15thNight
72%6%7%9%4
2506
16th to endNight
67%8%12%8%2
2688
February1st to 15thNight
66%7%9%13%3
2267
16th to endNight
65%6%10%11%4
1893
March1st to 15thNight
51%5%12%18%10%
2112
16th to endNight
44%6%13%23%11%1
2029
April1st to 15thNight
53%49%19%12%
1625
16th to endNight
43%5%12%20%16%2
1485
May1st to 15thNight
46%7%12%21%10%1
1485
16th to endNight
38%7%14%23%13%2
1416
June1st to 15thNight
40%6%12%23%16%
1169
16th to endNight
35%8%14%25%15%
1178
July1st to 15thNight
26%8%13%29%20%1
1240
16th to endNight
30%8%17%29%13%1
1305
August1st to 15thNight
29%7%18%29%15%
1462
16th to endNight
32%7%15%28%15%1
1611
September1st to 15thNight
35%6%13%30%13%
1730
16th to endNight
39%6%16%28%8%
1815
October1st to 15thNight
48%410%24%11%
1881
16th to endNight
56%7%14%16%5%
2266
November1st to 15thNight
51%6%14%17%8%
2276
16th to endNight
66%6%12%10%2
2424
December1st to 15thNight
70%9%9%8%2
2676
16th to endNight
74%5%10%7%2
2805

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
22%17%52%5%2
90
16th to endDay
35%12%37%11%3
96
February1st to 15thDay
23%30%38%6%1
90
16th to endDay
24%23%40%7%3
81
March1st to 15thDay
28%18%35%13%4
137
16th to endDay
22%12%30%21%10%2
260
April1st to 15thDay
23%18%26%21%9%
210
16th to endDay
20%13%30%19%10%5%
210
May1st to 15thDay
25%14%31%15%9%3
228
16th to endDay
16%14%30%24%9%3
389
June1st to 15thDay
19%17%27%25%8%2
420
16th to endDay
13%11%37%22%10%4
420
July1st to 15thDay
11%10%33%25%14%4
400
16th to endDay
11%8%32%28%11%6%
445
August1st to 15thDay
10%328%27%16%13%
267
16th to endDay
20%5%25%19%22%8%
268
September1st to 15thDay
16%6%21%25%18%10%
255
16th to endDay
16%9%24%25%16%7%
254
October1st to 15thDay
25%10%28%23%10%1
255
16th to endDay
26%26%33%10%3
115
November1st to 15thDay
15%18%38%16%7%2
90
16th to endDay
28%22%34%10%4
75
December1st to 15thDay
28%33%30%5%11
60
16th to endDay
35%38%23%2
76
January1st to 15thNight
24%18%34%18%3
900
16th to endNight
19%14%39%20%5%
960
February1st to 15thNight
21%19%36%18%3
716
16th to endNight
24%17%30%23%3
631
March1st to 15thNight
19%17%34%21%6%
720
16th to endNight
17%13%36%24%6%1
734
April1st to 15thNight
20%15%34%23%5%
494
16th to endNight
18%11%34%26%7%1
495
May1st to 15thNight
16%9%36%28%7%
495
16th to endNight
14%8%28%32%14%
515
June1st to 15thNight
16%7%33%32%9%
344
16th to endNight
9%433%37%14%1
353
July1st to 15thNight
8%324%43%19%1
465
16th to endNight
8%428%36%21%1
522
August1st to 15thNight
8%123%40%22%2
494
16th to endNight
11%421%37%22%1
525
September1st to 15thNight
15%5%24%30%19%4
575
16th to endNight
15%7%25%29%16%5%
657
October1st to 15thNight
23%7%28%28%11%
660
16th to endNight
28%13%29%22%5%
704
November1st to 15thNight
20%15%33%21%8%1
700
16th to endNight
27%16%35%17%3
720
December1st to 15thNight
26%17%36%16%2
876
16th to endNight
26%17%36%15%3
960
Page generated at 2017-03-25 12:39:48. Version ac04

Copyright 2017 A. Danko


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