Dayville School
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dayville School clear sky chart from 2005-11-05 to 2018-01-20.

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
53%
15208
17%
48488
17%
15184
56%
15184
26%
30583

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
38%
776
9%
2716
9%
776
40%
776
14%
1984
January16th to endNight
47%
788
15%
2743
16%
788
50%
788
20%
1842
February1st to 15thNight
39%
698
8%
2288
8%
698
41%
698
14%
1672
February16th to endNight
37%
632
14%
1900
12%
632
41%
632
16%
1392
March1st to 15thNight
40%
720
9%
2154
7%
720
43%
720
17%
1578
March16th to endNight
39%
768
11%
2001
7%
768
41%
768
20%
1479
April1st to 15thNight
43%
719
12%
1799
7%
719
44%
719
22%
1327
April16th to endNight
47%
660
16%
1740
10%
660
49%
660
27%
1170
May1st to 15thNight
57%
385
18%
1465
21%
385
60%
385
28%
797
May16th to endNight
58%
374
12%
1496
17%
374
59%
374
21%
920
June1st to 15thNight
60%
360
13%
1440
20%
360
65%
360
26%
808
June16th to endNight
68%
360
20%
1440
31%
360
73%
360
38%
657
July1st to 15thNight
83%
340
21%
1360
34%
340
87%
340
53%
516
July16th to endNight
82%
376
34%
1416
48%
354
87%
354
64%
485
August1st to 15thNight
83%
414
33%
1486
36%
412
86%
412
54%
613
August16th to endNight
81%
762
38%
1908
25%
762
83%
762
71%
904
September1st to 15thNight
83%
720
38%
1800
23%
720
84%
720
70%
867
September16th to endNight
68%
716
31%
1941
26%
716
70%
716
44%
1111
October1st to 15thNight
58%
720
21%
2148
20%
720
62%
720
33%
1292
October16th to endNight
58%
768
21%
2418
22%
768
61%
768
26%
1507
November1st to 15thNight
45%
760
15%
2470
15%
760
49%
760
19%
1720
November16th to endNight
41%
780
10%
2717
10%
780
43%
780
16%
1870
December1st to 15thNight
44%
780
11%
2730
10%
780
46%
780
16%
1908
December16th to endNight
35%
832
11%
2912
10%
832
38%
832
13%
2164

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
7%8%36%5%3445%6%43%
49064
Night
7%8%36%5%3445%6%43%
48656
Cloud CoverDay
9%8%36%5%24446%44%
49064
Night
9%9%35%5%2445%6%42%
48660
TransparencyDay
41%310%20%16%6%
48735
Night
41%413%21%14%4
48489
SeeingDay
15%16%29%24%11%3
5851
Night
14%7%16%34%23%3
15220

By Month

Percentage Cloud Cover NW (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
9%9%48%8%47%5%6%7%28%
1552
16th to endDay
8%12%48%6%345%48%32%
1581
February1st to 15thDay
8%11%6%8%6%46%5%6%7%28%
1576
16th to endDay
7%11%5%8%7%47%6%6%5%26%
1574
March1st to 15thDay
8%12%7%9%8%47%7%5%6%22%
1804
16th to endDay
8%15%7%10%7%46%5%6%5%23%
2223
April1st to 15thDay
10%13%6%8%8%46%5%46%25%
2149
16th to endDay
10%11%47%6%33446%37%
2219
May1st to 15thDay
7%8%35%6%3445%7%42%
2484
16th to endDay
14%9%47%6%25%446%32%
2615
June1st to 15thDay
13%7%35%5%245%47%39%
2520
16th to endDay
7%5%23313446%57%
2520
July1st to 15thDay
1112324346%67%
2520
16th to endDay
11221223476%
2657
August1st to 15thDay
1212313346%68%
2465
16th to endDay
111121234474%
2295
September1st to 15thDay
212212335%73%
2160
16th to endDay
7%7%2443335%6%51%
2019
October1st to 15thDay
11%8%35%5%2345%6%43%
1812
16th to endDay
10%7%37%5%35%45%5%41%
1806
November1st to 15thDay
12%13%37%6%345%47%30%
1719
16th to endDay
7%12%5%6%6%45%8%6%8%28%
1570
December1st to 15thDay
7%11%6%8%6%46%6%46%31%
1560
16th to endDay
9%16%6%8%8%46%5%5%6%22%
1664
January1st to 15thNight
8%11%6%8%7%46%5%5%6%28%
2716
16th to endNight
7%11%47%6%35%6%5%7%33%
2743
February1st to 15thNight
8%11%5%8%7%46%5%5%7%28%
2276
16th to endNight
6%12%5%9%8%36%5%5%7%30%
1900
March1st to 15thNight
8%10%48%7%47%6%6%8%28%
2154
16th to endNight
6%8%5%8%7%5%6%6%8%9%27%
1997
April1st to 15thNight
10%12%5%7%6%35%5%5%6%32%
1799
16th to endNight
7%10%37%424347%42%
1740
May1st to 15thNight
7%7%2442435%6%51%
1465
16th to endNight
10%8%35%5%245%5%7%39%
1496
June1st to 15thNight
9%5%25%5%2335%7%48%
1440
16th to endNight
4414323446%61%
1440
July1st to 15thNight
111223447%71%
1440
16th to endNight
1121123480%
1512
August1st to 15thNight
22232225%6%69%
1494
16th to endNight
11121223379%
1908
September1st to 15thNight
111211345%76%
1800
16th to endNight
44135%24446%57%
1941
October1st to 15thNight
8%7%25%43335%6%50%
2148
16th to endNight
7%7%27%5%35%45%5%44%
2418
November1st to 15thNight
12%10%36%5%35%6%6%7%30%
2470
16th to endNight
10%9%47%6%45%6%6%6%32%
2717
December1st to 15thNight
8%10%48%6%35%5%5%7%33%
2730
16th to endNight
9%12%6%8%8%445%5%8%25%
2912

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
11%9%5%9%7%46%5%5%7%27%
1552
16th to endDay
11%13%47%6%2445%8%31%
1581
February1st to 15thDay
9%14%6%8%6%35%5%5%7%27%
1576
16th to endDay
10%13%5%9%7%35%6%5%7%25%
1574
March1st to 15thDay
10%13%6%11%7%46%5%5%6%21%
1804
16th to endDay
11%16%6%9%7%35%5%46%23%
2223
April1st to 15thDay
11%15%5%8%8%35%45%6%25%
2149
16th to endDay
11%11%36%5%34346%36%
2219
May1st to 15thDay
9%8%35%5%24447%42%
2484
16th to endDay
16%9%46%5%35%446%33%
2615
June1st to 15thDay
14%7%36%5%2445%6%39%
2520
16th to endDay
8%414323346%58%
2520
July1st to 15thDay
2112324345%67%
2520
16th to endDay
11121223477%
2657
August1st to 15thDay
2212313245%69%
2465
16th to endDay
212212235%74%
2295
September1st to 15thDay
221221123474%
2160
16th to endDay
8%5%35%423345%51%
2019
October1st to 15thDay
12%8%25%42335%6%43%
1812
16th to endDay
13%7%35%6%3445%5%40%
1806
November1st to 15thDay
15%12%36%5%35%35%7%30%
1719
16th to endDay
10%13%46%6%35%5%6%7%28%
1570
December1st to 15thDay
11%13%47%7%36%446%29%
1560
16th to endDay
14%17%5%9%7%35%5%45%21%
1664
January1st to 15thNight
12%12%48%7%35%5%5%5%28%
2716
16th to endNight
10%13%46%5%245%5%6%34%
2743
February1st to 15thNight
11%13%5%8%6%35%45%6%27%
2276
16th to endNight
8%13%6%10%6%35%6%46%29%
1900
March1st to 15thNight
9%13%6%7%6%36%5%6%7%26%
2154
16th to endNight
8%12%5%8%6%45%6%6%8%27%
2001
April1st to 15thNight
12%12%46%6%3445%6%32%
1799
16th to endNight
10%12%25%42445%6%41%
1740
May1st to 15thNight
9%7%24423446%50%
1465
16th to endNight
12%8%35%5%2346%6%39%
1496
June1st to 15thNight
12%6%2432335%8%47%
1440
16th to endNight
6%413323335%62%
1440
July1st to 15thNight
111223446%71%
1440
16th to endNight
1121123380%
1512
August1st to 15thNight
221132235%6%69%
1494
16th to endNight
11111123478%
1908
September1st to 15thNight
211212345%75%
1800
16th to endNight
6%5%14423446%56%
1941
October1st to 15thNight
10%8%25%423346%49%
2148
16th to endNight
9%7%37%5%2445%5%44%
2418
November1st to 15thNight
16%11%25%6%35%5%7%7%29%
2470
16th to endNight
13%11%47%6%35%45%6%31%
2717
December1st to 15thNight
11%12%5%7%6%35%45%6%33%
2730
16th to endNight
13%14%6%7%6%36%45%6%25%
2912

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
55%5%15%16%5%
1552
16th to endDay
50%416%16%7%3
1581
February1st to 15thDay
55%5%17%15%5%
1576
16th to endDay
57%5%13%18%4
1574
March1st to 15thDay
63%312%14%4
1804
16th to endDay
61%412%16%4
2223
April1st to 15thDay
60%310%18%6%
2149
16th to endDay
48%310%23%11%
2219
May1st to 15thDay
41%311%28%13%1
2484
16th to endDay
52%311%21%9%1
2619
June1st to 15thDay
44%48%26%14%2
2520
16th to endDay
27%19%30%24%6%
2520
July1st to 15thDay
18%25%21%30%21%
2371
16th to endDay
12%1313%37%31%
2490
August1st to 15thDay
17%2422%34%18%
2448
16th to endDay
13%1425%38%16%
2295
September1st to 15thDay
15%1326%34%17%
2160
16th to endDay
33%38%25%23%6%
2019
October1st to 15thDay
41%312%20%17%4
1812
16th to endDay
45%311%22%16%
1806
November1st to 15thDay
54%5%11%20%7%
1719
16th to endDay
52%5%16%16%8%
1570
December1st to 15thDay
54%5%16%17%6%
1560
16th to endDay
65%313%13%3
1664
January1st to 15thNight
56%5%14%16%6%
2716
16th to endNight
49%314%19%9%3
2743
February1st to 15thNight
55%5%17%13%7%
2288
16th to endNight
54%5%11%21%6%1
1900
March1st to 15thNight
54%5%15%18%41
2154
16th to endNight
51%5%17%21%3
2001
April1st to 15thNight
51%413%23%6%
1799
16th to endNight
42%5%16%24%9%
1740
May1st to 15thNight
34%315%31%14%
1466
16th to endNight
44%317%25%9%
1496
June1st to 15thNight
34%6%14%27%14%2
1440
16th to endNight
25%212%35%19%5%
1440
July1st to 15thNight
14%310%25%30%16%
1360
16th to endNight
10%1418%39%25%
1416
August1st to 15thNight
15%26%27%30%17%
1486
16th to endNight
10%15%26%38%16%
1908
September1st to 15thNight
12%1430%36%15%
1800
16th to endNight
28%29%25%22%10%
1941
October1st to 15thNight
35%310%26%19%4
2148
16th to endNight
41%313%21%16%3
2418
November1st to 15thNight
50%5%12%20%10%
2470
16th to endNight
51%414%15%12%
2717
December1st to 15thNight
51%5%17%17%7%
2730
16th to endNight
59%413%16%5%
2912

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
12%6%33%18%25%3
90
16th to endDay
21%11%30%27%8%
84
February1st to 15thDay
19%19%31%19%8%2
236
16th to endDay
18%29%30%15%5%
237
March1st to 15thDay
27%27%28%12%3
270
16th to endDay
27%25%29%14%2
288
April1st to 15thDay
20%23%28%16%7%4
269
16th to endDay
25%23%26%14%7%2
270
May1st to 15thDay
18%20%29%21%9%1
288
16th to endDay
22%12%21%26%11%5%
330
June1st to 15thDay
20%16%26%21%11%3
315
16th to endDay
8%15%32%25%13%4
315
July1st to 15thDay
5%9%34%29%16%4
305
16th to endDay
116%38%26%12%4
327
August1st to 15thDay
37%35%34%13%5%
315
16th to endDay
310%26%34%18%6%
332
September1st to 15thDay
5%7%29%32%20%5%
315
16th to endDay
11%10%25%31%19%1
315
October1st to 15thDay
19%14%22%28%12%2
315
16th to endDay
16%17%22%25%13%4
222
November1st to 15thDay
15%20%28%27%8%
135
16th to endDay
19%23%29%22%4
92
December1st to 15thDay
21%16%31%17%11%2
90
16th to endDay
14%16%38%21%8%
96
January1st to 15thNight
17%10%24%26%18%2
780
16th to endNight
16%7%19%36%17%2
788
February1st to 15thNight
17%10%18%34%15%2
704
16th to endNight
16%14%21%30%15%1
632
March1st to 15thNight
16%12%23%29%16%1
720
16th to endNight
15%15%23%30%14%1
768
April1st to 15thNight
18%13%18%27%20%1
719
16th to endNight
16%10%17%30%20%3
660
May1st to 15thNight
13%6%16%34%26%2
386
16th to endNight
14%5%9%34%30%4
375
June1st to 15thNight
14%313%41%25%1
360
16th to endNight
8%414%43%27%2
360
July1st to 15thNight
218%46%38%2
340
16th to endNight
1111%48%36%1
376
August1st to 15thNight
35%40%43%6%
414
16th to endNight
129%37%41%6%
762
September1st to 15thNight
218%37%41%8%
720
16th to endNight
9%311%36%30%9%
716
October1st to 15thNight
14%313%38%24%4
720
16th to endNight
14%5%12%37%22%7%
768
November1st to 15thNight
21%6%16%36%16%1
760
16th to endNight
19%13%19%26%15%5%
780
December1st to 15thNight
18%8%19%33%17%1
780
16th to endNight
21%11%24%30%11%
832
Page generated at 2018-01-21 09:19:25. Version ac04

Copyright 2018 A. Danko


Dayville School Clear Sky Chart |Charts Home