Perryville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Perryville clear sky chart from 2005-11-05 to 2018-02-13.

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
38%
16670
17%
48785
10%
16627
44%
16627
24%
32637

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
23%
975
14%
2716
5%
970
31%
970
19%
1978
January16th to endNight
23%
1040
12%
2850
4%
1040
29%
1040
16%
2136
February1st to 15thNight
23%
896
14%
2403
4%
896
30%
896
19%
1744
February16th to endNight
27%
631
18%
1893
8%
631
36%
631
18%
1322
March1st to 15thNight
30%
720
14%
2160
8%
720
36%
720
20%
1472
March16th to endNight
31%
588
15%
2001
11%
588
38%
588
18%
1387
April1st to 15thNight
29%
539
15%
1797
9%
539
39%
539
19%
1220
April16th to endNight
32%
540
19%
1758
11%
540
44%
540
22%
1173
May1st to 15thNight
36%
540
15%
1547
8%
540
42%
540
22%
1086
May16th to endNight
46%
563
17%
1498
9%
561
52%
561
31%
977
June1st to 15thNight
53%
540
16%
1440
10%
540
55%
540
35%
893
June16th to endNight
51%
540
16%
1440
9%
540
55%
540
30%
955
July1st to 15thNight
64%
510
17%
1360
10%
510
67%
510
41%
809
July16th to endNight
68%
564
20%
1417
16%
531
71%
531
42%
831
August1st to 15thNight
76%
539
22%
1566
21%
536
77%
536
42%
861
August16th to endNight
66%
573
21%
1910
22%
573
70%
573
34%
1065
September1st to 15thNight
63%
540
28%
1800
28%
540
69%
540
36%
965
September16th to endNight
57%
696
27%
1959
19%
696
62%
696
35%
1164
October1st to 15thNight
43%
720
23%
2111
16%
720
49%
720
29%
1316
October16th to endNight
31%
768
19%
2418
10%
768
41%
768
22%
1572
November1st to 15thNight
33%
760
22%
2471
16%
760
43%
760
24%
1540
November16th to endNight
26%
873
18%
2628
8%
873
37%
873
20%
1781
December1st to 15thNight
22%
975
12%
2730
4%
975
30%
975
17%
2050
December16th to endNight
19%
1040
11%
2912
3%
1040
26%
1040
12%
2340

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%8%36%5%3445%7%36%
49266
Night
14%7%35%434446%40%
48953
Cloud CoverDay
14%8%36%5%3445%7%36%
49274
Night
14%7%35%5%24446%40%
48958
TransparencyDay
45%6%13%21%11%1
48952
Night
44%5%12%22%14%1
48785
SeeingDay
16%7%27%26%16%6%
6468
Night
17%7%30%30%12%1
16673

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
13%12%5%6%6%45%5%5%7%26%
1552
16th to endDay
13%13%7%10%7%24445%26%
1723
February1st to 15thDay
13%13%5%7%436%445%29%
1724
16th to endDay
13%11%47%6%34346%33%
1580
March1st to 15thDay
15%9%5%6%5%235%47%34%
1790
16th to endDay
18%9%37%5%35%45%7%29%
2232
April1st to 15thDay
18%10%47%5%3445%6%29%
2151
16th to endDay
20%8%35%5%2445%6%33%
2202
May1st to 15thDay
20%8%37%6%35%447%28%
2403
16th to endDay
14%6%25%5%35%6%6%7%37%
2617
June1st to 15thDay
12%5%144345%6%7%41%
2520
16th to endDay
10%435%5%35%6%6%10%38%
2520
July1st to 15thDay
7%4245%35%6%7%9%44%
2520
16th to endDay
7%5%25%6%35%5%6%9%41%
2655
August1st to 15thDay
7%415%6%35%5%6%10%42%
2382
16th to endDay
12%4345%245%5%8%44%
2292
September1st to 15thDay
13%413323447%50%
2160
16th to endDay
9%6%25%5%3445%6%46%
1989
October1st to 15thDay
18%6%25%423335%43%
1848
16th to endDay
19%8%345%24345%37%
1804
November1st to 15thDay
15%9%35%43445%6%39%
1717
16th to endDay
18%9%45%422236%39%
1661
December1st to 15thDay
17%13%47%5%34345%29%
1560
16th to endDay
19%15%5%8%6%3434423%
1664
January1st to 15thNight
15%10%5%7%6%2334434%
2716
16th to endNight
12%11%6%9%6%34446%29%
2850
February1st to 15thNight
14%12%5%6%43333435%
2401
16th to endNight
15%11%47%5%24346%34%
1893
March1st to 15thNight
16%9%345%33445%38%
2147
16th to endNight
17%8%45%43445%7%33%
2001
April1st to 15thNight
20%7%444245%45%36%
1797
16th to endNight
19%7%36%313345%40%
1758
May1st to 15thNight
18%5%25%5%345%6%8%34%
1547
16th to endNight
10%4235%345%6%9%42%
1496
June1st to 15thNight
11%41442445%7%49%
1440
16th to endNight
7%5%25%6%35%6%6%7%43%
1440
July1st to 15thNight
6%3133245%5%10%52%
1440
16th to endNight
7%323425%5%6%10%49%
1513
August1st to 15thNight
321343346%10%54%
1575
16th to endNight
9%31443335%8%50%
1910
September1st to 15thNight
8%414424345%57%
1800
16th to endNight
9%4135%34447%51%
1959
October1st to 15thNight
13%6%24323345%48%
2111
16th to endNight
19%7%24323345%42%
2418
November1st to 15thNight
14%7%25%323335%46%
2471
16th to endNight
17%8%35%5%23345%39%
2628
December1st to 15thNight
19%9%48%5%34445%30%
2730
16th to endNight
22%12%5%8%6%3444422%
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
13%13%5%6%5%45%6%47%26%
1552
16th to endDay
13%13%7%10%6%33435%26%
1723
February1st to 15thDay
13%13%5%8%446%445%28%
1724
16th to endDay
13%11%47%6%3435%6%32%
1580
March1st to 15thDay
16%9%46%5%235%47%33%
1800
16th to endDay
17%9%37%5%35%45%6%29%
2230
April1st to 15thDay
18%9%47%6%3445%6%29%
2151
16th to endDay
20%8%26%5%2345%6%33%
2202
May1st to 15thDay
19%8%47%5%35%45%6%28%
2403
16th to endDay
13%6%35%5%35%6%5%7%37%
2617
June1st to 15thDay
12%5%245%245%6%8%41%
2520
16th to endDay
10%435%5%25%6%7%10%38%
2520
July1st to 15thDay
7%3245%35%6%6%9%44%
2520
16th to endDay
7%5%25%5%36%5%7%9%41%
2655
August1st to 15thDay
7%4146%35%5%6%10%43%
2382
16th to endDay
12%5%25%5%335%5%7%43%
2292
September1st to 15thDay
12%31332345%7%50%
2160
16th to endDay
8%5%35%5%2446%6%47%
1989
October1st to 15thDay
17%6%25%423345%43%
1848
16th to endDay
18%8%35%5%34445%37%
1804
November1st to 15thDay
15%9%345%2445%6%39%
1717
16th to endDay
17%9%46%422227%38%
1661
December1st to 15thDay
16%13%47%5%3435%5%29%
1560
16th to endDay
18%15%6%8%6%3444423%
1664
January1st to 15thNight
15%10%5%7%6%2344434%
2716
16th to endNight
12%11%6%9%7%34446%29%
2850
February1st to 15thNight
14%12%5%6%433435%35%
2394
16th to endNight
15%11%47%424346%34%
1893
March1st to 15thNight
16%9%345%3345%5%38%
2160
16th to endNight
17%8%35%5%35%45%7%32%
2001
April1st to 15thNight
20%7%444245%45%37%
1797
16th to endNight
18%8%36%314336%40%
1758
May1st to 15thNight
18%5%245%345%6%7%34%
1546
16th to endNight
10%4335%25%5%6%9%42%
1496
June1st to 15thNight
11%4145%25%447%49%
1440
16th to endNight
7%5%25%6%36%6%6%7%43%
1440
July1st to 15thNight
6%3133245%5%10%51%
1440
16th to endNight
6%3224245%7%10%49%
1513
August1st to 15thNight
321343445%11%54%
1575
16th to endNight
9%31443435%9%50%
1910
September1st to 15thNight
8%413423336%57%
1800
16th to endNight
9%4135%24447%51%
1959
October1st to 15thNight
13%5%34333346%48%
2111
16th to endNight
18%7%25%323345%42%
2418
November1st to 15thNight
13%7%25%424335%46%
2471
16th to endNight
17%8%36%5%23345%39%
2628
December1st to 15thNight
19%9%38%5%24445%30%
2730
16th to endNight
21%13%5%8%6%35%43423%
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%13%15%9%
1553
16th to endDay
59%5%13%14%7%
1723
February1st to 15thDay
57%5%10%17%8%1
1726
16th to endDay
51%6%11%21%8%
1580
March1st to 15thDay
49%5%15%20%8%1
1800
16th to endDay
54%6%12%19%6%
2232
April1st to 15thDay
55%5%10%20%7%
2151
16th to endDay
50%5%12%18%11%1
2202
May1st to 15thDay
55%5%12%19%5%
2403
16th to endDay
44%7%12%20%12%1
2621
June1st to 15thDay
38%7%14%24%14%
2520
16th to endDay
37%8%14%22%15%1
2520
July1st to 15thDay
34%7%15%25%14%1
2371
16th to endDay
35%7%18%21%13%2
2488
August1st to 15thDay
33%8%14%28%13%1
2367
16th to endDay
37%6%12%25%15%2
2292
September1st to 15thDay
32%5%10%27%20%2
2160
16th to endDay
35%5%13%27%16%1
1989
October1st to 15thDay
42%410%25%15%
1848
16th to endDay
48%5%12%22%10%1
1804
November1st to 15thDay
45%412%23%12%1
1717
16th to endDay
48%415%24%6%
1661
December1st to 15thDay
57%414%16%7%
1560
16th to endDay
64%411%11%7%
1664
January1st to 15thNight
52%410%18%12%
2716
16th to endNight
55%5%14%15%8%
2850
February1st to 15thNight
52%311%19%11%
2403
16th to endNight
50%411%22%8%2
1893
March1st to 15thNight
47%5%14%18%11%1
2160
16th to endNight
50%5%12%20%9%
2001
April1st to 15thNight
48%49%21%14%1
1797
16th to endNight
46%49%24%11%4
1758
May1st to 15thNight
46%7%13%20%10%
1547
16th to endNight
36%8%14%22%16%2
1498
June1st to 15thNight
34%5%13%24%20%1
1440
16th to endNight
37%8%11%19%20%2
1440
July1st to 15thNight
27%7%12%30%19%2
1360
16th to endNight
26%7%17%26%17%4
1417
August1st to 15thNight
24%7%13%33%18%2
1566
16th to endNight
30%5%14%27%18%4
1910
September1st to 15thNight
28%49%26%27%2
1800
16th to endNight
31%6%10%31%18%1
1959
October1st to 15thNight
37%410%24%20%2
2111
16th to endNight
44%412%24%12%1
2418
November1st to 15thNight
41%410%23%17%3
2471
16th to endNight
46%413%23%10%
2628
December1st to 15thNight
56%410%20%7%
2730
16th to endNight
64%410%13%6%
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
21%8%34%28%5%
135
16th to endDay
20%7%37%26%42
144
February1st to 15thDay
22%11%43%17%4
126
16th to endDay
30%9%29%22%7%
81
March1st to 15thDay
28%15%32%18%4
90
16th to endDay
31%7%30%16%12%1
219
April1st to 15thDay
23%12%29%22%10%
270
16th to endDay
21%11%27%24%10%4
270
May1st to 15thDay
23%13%26%23%10%3
360
16th to endDay
18%9%29%24%13%4
517
June1st to 15thDay
11%432%28%17%4
495
16th to endDay
12%5%32%26%16%5%
495
July1st to 15thDay
7%425%30%22%10%
475
16th to endDay
8%220%34%22%10%
515
August1st to 15thDay
8%217%31%26%13%
439
16th to endDay
11%5%14%28%27%13%
332
September1st to 15thDay
11%215%30%30%9%
315
16th to endDay
8%6%21%26%27%8%
314
October1st to 15thDay
18%9%23%26%18%3
183
16th to endDay
27%9%24%31%6%
144
November1st to 15thDay
17%8%33%19%17%4
135
16th to endDay
27%11%37%14%9%
135
December1st to 15thDay
20%13%40%19%5%
135
16th to endDay
26%14%45%11%2
144
January1st to 15thNight
20%12%37%24%6%
975
16th to endNight
17%10%36%29%5%
1040
February1st to 15thNight
20%9%39%25%5%
899
16th to endNight
21%10%33%25%7%
631
March1st to 15thNight
20%9%33%29%7%
720
16th to endNight
21%7%33%27%9%
588
April1st to 15thNight
23%11%32%27%5%
539
16th to endNight
21%7%34%28%8%
540
May1st to 15thNight
21%5%31%30%10%
540
16th to endNight
13%330%36%15%
563
June1st to 15thNight
11%325%44%14%
540
16th to endNight
9%329%38%17%
540
July1st to 15thNight
8%120%41%26%1
510
16th to endNight
6%115%46%26%2
564
August1st to 15thNight
5%10%48%30%4
539
16th to endNight
10%115%38%30%4
573
September1st to 15thNight
9%318%34%28%5%
540
16th to endNight
11%420%32%26%3
696
October1st to 15thNight
16%7%28%30%17%
720
16th to endNight
23%9%32%23%10%
768
November1st to 15thNight
18%8%35%25%11%
760
16th to endNight
20%11%35%25%7%
873
December1st to 15thNight
24%10%35%24%5%
975
16th to endNight
28%8%34%24%3
1040
Page generated at 2018-02-13 19:45:57. Version ac04

Copyright 2018 A. Danko


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