Coatesville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Coatesville clear sky chart from 2005-11-05 to 2018-10-08.

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
31%
16462
19%
51038
9%
16425
43%
16425
22%
32618

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
19%
780
20%
2716
7%
776
36%
776
15%
1721
January16th to endNight
15%
832
22%
2709
5%
832
36%
832
17%
1710
February1st to 15thNight
11%
764
17%
2471
3%
761
28%
761
15%
1606
February16th to endNight
13%
683
23%
2049
5%
683
34%
683
16%
1320
March1st to 15thNight
18%
780
21%
2245
6%
780
35%
780
19%
1455
March16th to endNight
21%
832
22%
2216
8%
832
33%
832
24%
1476
April1st to 15thNight
19%
778
18%
1946
5%
778
27%
778
23%
1308
April16th to endNight
29%
771
18%
1927
4%
771
36%
771
27%
1303
May1st to 15thNight
30%
556
16%
1726
8%
556
38%
556
19%
1164
May16th to endNight
45%
406
15%
1625
13%
406
50%
406
17%
1018
June1st to 15thNight
43%
390
17%
1560
14%
390
54%
390
20%
944
June16th to endNight
53%
390
15%
1560
18%
390
58%
390
25%
913
July1st to 15thNight
50%
370
13%
1480
14%
370
54%
370
19%
936
July16th to endNight
60%
472
14%
1605
14%
445
65%
445
27%
956
August1st to 15thNight
59%
601
17%
1741
12%
598
62%
598
29%
1122
August16th to endNight
57%
828
17%
2070
9%
828
58%
828
33%
1361
September1st to 15thNight
46%
780
23%
1950
11%
780
52%
780
31%
1298
September16th to endNight
50%
777
25%
2109
18%
777
56%
777
31%
1368
October1st to 15thNight
40%
752
20%
2255
15%
752
48%
752
25%
1440
October16th to endNight
31%
768
28%
2322
14%
768
48%
768
28%
1378
November1st to 15thNight
31%
760
22%
2472
11%
760
46%
760
23%
1526
November16th to endNight
25%
780
22%
2642
10%
780
40%
780
18%
1627
December1st to 15thNight
21%
780
16%
2730
5%
780
35%
780
14%
1817
December16th to endNight
17%
832
19%
2912
5%
832
35%
832
15%
1851

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
14%5%25%5%3445%7%40%
52101
Night
15%5%2442445%7%42%
51214
Cloud CoverDay
14%5%25%5%3445%7%39%
52111
Night
14%5%2442445%7%42%
51219
TransparencyDay
42%6%12%21%15%2
51795
Night
40%6%12%22%16%2
51038
SeeingDay
19%15%27%21%11%4
7072
Night
18%15%29%25%10%1
16463

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
15%6%35%6%2445%6%39%
1552
16th to endDay
14%8%25%5%3445%6%40%
1866
February1st to 15thDay
15%7%36%5%34447%38%
1721
16th to endDay
15%8%45%5%3435%6%37%
1710
March1st to 15thDay
15%6%26%6%35%447%40%
2033
16th to endDay
19%6%25%5%23346%39%
2359
April1st to 15thDay
15%7%25%434447%40%
2332
16th to endDay
16%42443435%7%43%
2308
May1st to 15thDay
17%6%25%5%25%45%7%37%
2566
16th to endDay
16%6%25%5%345%5%8%36%
2842
June1st to 15thDay
13%5%35%5%345%6%10%35%
2730
16th to endDay
11%4246%35%5%6%9%39%
2730
July1st to 15thDay
10%5%246%35%6%7%9%38%
2730
16th to endDay
8%435%7%36%7%6%9%37%
2811
August1st to 15thDay
12%5%25%6%36%46%8%38%
2445
16th to endDay
11%4245%345%6%9%41%
2484
September1st to 15thDay
17%4244335%5%6%43%
2340
16th to endDay
15%5%35%5%35%447%41%
2178
October1st to 15thDay
16%5%25%423346%44%
1875
16th to endDay
17%413323447%45%
1902
November1st to 15thDay
16%7%24323346%45%
1716
16th to endDay
16%5%24424446%44%
1647
December1st to 15thDay
16%6%25%5%34446%40%
1560
16th to endDay
17%5%25%6%24437%38%
1664
January1st to 15thNight
16%5%25%5%25%447%41%
2716
16th to endNight
15%7%25%424346%43%
2709
February1st to 15thNight
14%6%35%5%3445%5%40%
2469
16th to endNight
16%7%3442445%5%42%
2049
March1st to 15thNight
16%5%15%434346%43%
2233
16th to endNight
17%6%25%423335%45%
2216
April1st to 15thNight
15%5%245%1445%8%41%
1946
16th to endNight
16%5%2442445%7%43%
1927
May1st to 15thNight
16%6%25%5%35%45%7%38%
1726
16th to endNight
17%5%34334448%39%
1623
June1st to 15thNight
15%4245%24448%41%
1560
16th to endNight
10%4144346%6%11%42%
1560
July1st to 15thNight
9%5%15%6%36%6%6%8%39%
1560
16th to endNight
8%325%435%5%8%9%42%
1706
August1st to 15thNight
10%424435%5%7%8%43%
1752
16th to endNight
11%4245%245%5%6%46%
2070
September1st to 15thNight
15%6%24313447%46%
1950
16th to endNight
13%5%1442346%6%45%
2109
October1st to 15thNight
18%5%24323347%43%
2255
16th to endNight
17%413222246%51%
2322
November1st to 15thNight
13%6%25%424445%47%
2472
16th to endNight
16%424435%5%5%6%42%
2642
December1st to 15thNight
17%5%36%5%35%45%6%36%
2730
16th to endNight
16%6%25%5%2446%7%38%
2912

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
14%6%35%6%245%5%5%40%
1552
16th to endDay
14%7%34435%45%6%40%
1866
February1st to 15thDay
14%7%36%5%2435%7%38%
1721
16th to endDay
15%8%35%5%3335%5%37%
1710
March1st to 15thDay
15%6%25%6%34446%40%
2044
16th to endDay
18%6%25%5%23346%39%
2358
April1st to 15thDay
15%6%35%5%2435%6%41%
2332
16th to endDay
15%4145%25%447%43%
2308
May1st to 15thDay
16%6%25%5%3445%7%37%
2566
16th to endDay
16%6%25%435%46%7%36%
2842
June1st to 15thDay
12%5%35%5%35%5%7%9%35%
2730
16th to endDay
11%425%5%35%5%6%9%39%
2730
July1st to 15thDay
9%425%6%45%6%6%10%37%
2730
16th to endDay
8%435%7%37%6%7%9%36%
2811
August1st to 15thDay
11%5%25%6%45%5%6%8%37%
2445
16th to endDay
10%5%25%5%246%6%9%41%
2484
September1st to 15thDay
16%5%234345%46%42%
2340
16th to endDay
14%5%25%5%43446%40%
2178
October1st to 15thDay
16%5%24423347%43%
1875
16th to endDay
16%5%2332435%6%45%
1902
November1st to 15thDay
15%6%33323346%44%
1716
16th to endDay
15%5%24423446%45%
1647
December1st to 15thDay
16%5%345%435%46%40%
1560
16th to endDay
17%6%346%33447%37%
1664
January1st to 15thNight
15%5%25%425%447%41%
2716
16th to endNight
15%7%24424346%43%
2709
February1st to 15thNight
14%7%35%5%3445%6%39%
2462
16th to endNight
16%6%25%32445%5%42%
2049
March1st to 15thNight
16%5%24424446%43%
2245
16th to endNight
17%6%25%423335%45%
2216
April1st to 15thNight
15%6%15%5%24448%41%
1946
16th to endNight
15%5%3432445%6%43%
1927
May1st to 15thNight
16%6%25%435%447%38%
1726
16th to endNight
17%5%35%424448%39%
1623
June1st to 15thNight
14%5%25%5%1446%8%41%
1560
16th to endNight
9%5%24425%5%7%10%41%
1560
July1st to 15thNight
8%5%26%5%47%6%6%9%38%
1560
16th to endNight
8%4235%36%6%7%9%42%
1706
August1st to 15thNight
9%5%145%346%6%9%42%
1752
16th to endNight
11%5%245%2446%7%45%
2070
September1st to 15thNight
14%6%24323347%46%
1950
16th to endNight
13%5%2443346%6%45%
2109
October1st to 15thNight
16%6%24422347%43%
2255
16th to endNight
16%413322346%51%
2322
November1st to 15thNight
13%6%25%42345%5%47%
2472
16th to endNight
16%5%234345%5%6%42%
2642
December1st to 15thNight
18%5%35%5%3445%6%36%
2730
16th to endNight
16%6%26%42446%7%38%
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
43%5%14%19%12%4
1553
16th to endDay
44%412%23%12%2
1866
February1st to 15thDay
45%412%22%11%2
1723
16th to endDay
46%411%23%11%1
1710
March1st to 15thDay
43%6%11%22%13%2
2044
16th to endDay
46%49%19%17%2
2359
April1st to 15thDay
42%5%10%22%14%4
2332
16th to endDay
40%5%9%18%20%4
2308
May1st to 15thDay
45%6%11%19%14%2
2566
16th to endDay
44%7%14%19%12%1
2846
June1st to 15thDay
42%8%13%22%11%
2730
16th to endDay
39%8%14%22%14%1
2730
July1st to 15thDay
39%8%12%20%15%3
2581
16th to endDay
39%8%14%23%12%2
2649
August1st to 15thDay
41%9%12%19%15%1
2432
16th to endDay
37%7%13%21%17%3
2484
September1st to 15thDay
40%6%10%20%19%2
2340
16th to endDay
42%5%8%19%21%2
2178
October1st to 15thDay
40%5%13%20%17%1
1875
16th to endDay
38%311%27%17%1
1902
November1st to 15thDay
40%413%20%17%3
1716
16th to endDay
39%411%27%15%1
1647
December1st to 15thDay
43%5%16%21%11%1
1560
16th to endDay
45%6%14%20%11%1
1664
January1st to 15thNight
42%5%11%20%15%3
2716
16th to endNight
41%411%26%14%1
2709
February1st to 15thNight
44%5%12%22%12%2
2471
16th to endNight
42%410%23%16%3
2049
March1st to 15thNight
40%5%11%23%16%2
2245
16th to endNight
41%411%21%16%3
2216
April1st to 15thNight
40%5%12%20%17%3
1946
16th to endNight
40%6%9%18%20%4
1927
May1st to 15thNight
45%7%10%16%16%3
1726
16th to endNight
42%7%14%15%16%2
1625
June1st to 15thNight
39%7%12%22%16%
1560
16th to endNight
34%9%12%26%15%1
1560
July1st to 15thNight
40%10%14%17%14%2
1480
16th to endNight
33%9%18%21%15%2
1605
August1st to 15thNight
35%9%14%22%17%1
1741
16th to endNight
35%7%12%21%19%2
2070
September1st to 15thNight
38%6%11%20%21%2
1950
16th to endNight
37%6%7%21%24%2
2109
October1st to 15thNight
41%413%23%15%2
2255
16th to endNight
34%49%30%18%2
2322
November1st to 15thNight
39%5%10%22%16%6%
2472
16th to endNight
40%5%10%24%17%2
2642
December1st to 15thNight
47%5%12%20%11%1
2730
16th to endNight
42%6%15%22%11%1
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
22%37%25%10%31
90
16th to endDay
20%32%35%10%
143
February1st to 15thDay
29%33%30%6%
147
16th to endDay
23%27%34%12%2
291
March1st to 15thDay
20%29%31%14%3
330
16th to endDay
24%24%32%12%32
352
April1st to 15thDay
22%24%34%11%5%1
330
16th to endDay
22%15%33%18%7%2
319
May1st to 15thDay
25%18%28%18%7%1
348
16th to endDay
24%7%23%26%16%1
395
June1st to 15thDay
17%10%30%24%14%2
375
16th to endDay
15%11%27%29%13%2
375
July1st to 15thDay
13%424%31%19%6%
365
16th to endDay
11%224%33%22%5%
390
August1st to 15thDay
15%5%21%28%20%8%
358
16th to endDay
11%221%33%17%13%
396
September1st to 15thDay
21%8%21%20%17%10%
375
16th to endDay
19%7%21%26%15%9%
374
October1st to 15thDay
20%6%24%26%15%5%
345
16th to endDay
14%19%32%19%11%2
331
November1st to 15thDay
19%13%28%23%11%2
280
16th to endDay
15%28%32%16%6%
177
December1st to 15thDay
20%33%26%10%10%
90
16th to endDay
27%36%28%6%2
96
January1st to 15thNight
19%25%33%18%3
780
16th to endNight
20%25%36%17%
832
February1st to 15thNight
19%25%37%16%
764
16th to endNight
21%28%33%14%1
683
March1st to 15thNight
21%24%32%17%3
780
16th to endNight
20%17%37%18%6%
832
April1st to 15thNight
18%23%35%18%3
778
16th to endNight
19%14%33%24%8%
771
May1st to 15thNight
21%11%32%27%7%
556
16th to endNight
19%7%21%38%12%
407
June1st to 15thNight
16%5%26%40%11%
390
16th to endNight
9%128%46%13%
390
July1st to 15thNight
11%324%37%21%1
370
16th to endNight
10%219%43%22%2
472
August1st to 15thNight
13%18%40%23%3
601
16th to endNight
13%317%37%25%2
828
September1st to 15thNight
17%6%22%31%19%2
780
16th to endNight
15%423%26%26%4
777
October1st to 15thNight
19%9%25%25%16%3
752
16th to endNight
20%15%29%24%9%
768
November1st to 15thNight
16%15%31%24%10%1
760
16th to endNight
19%22%29%20%8%
780
December1st to 15thNight
22%20%32%17%7%
780
16th to endNight
20%23%35%19%1
832
Page generated at 2018-10-09 10:39:17. Version ac04

Copyright 2018 A. Danko


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