Danville Conservation Area
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Danville Conservation Area clear sky chart from 2005-11-05 to 2017-04-26.

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
34%
15432
21%
45625
11%
15384
43%
15384
25%
28957

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
18%
900
20%
2443
6%
895
29%
895
21%
1654
January16th to endNight
19%
960
20%
2496
6%
960
30%
960
21%
1713
February1st to 15thNight
18%
877
14%
2285
3%
873
25%
873
16%
1657
February16th to endNight
17%
631
21%
1893
5%
631
30%
631
21%
1216
March1st to 15thNight
19%
605
17%
2045
7%
605
30%
605
18%
1350
March16th to endNight
19%
576
13%
2067
7%
576
28%
576
13%
1448
April1st to 15thNight
26%
539
20%
1797
10%
539
41%
539
22%
1097
April16th to endNight
30%
528
22%
1760
13%
528
45%
528
25%
1072
May1st to 15thNight
36%
495
18%
1508
12%
494
43%
494
24%
993
May16th to endNight
40%
515
17%
1369
10%
513
46%
513
29%
917
June1st to 15thNight
53%
495
20%
1320
13%
495
57%
495
38%
802
June16th to endNight
55%
495
20%
1320
11%
495
60%
495
40%
785
July1st to 15thNight
62%
465
20%
1240
14%
465
65%
465
38%
755
July16th to endNight
68%
522
20%
1422
19%
489
70%
489
41%
791
August1st to 15thNight
71%
494
25%
1491
28%
491
74%
491
40%
819
August16th to endNight
68%
525
22%
1750
25%
525
71%
525
37%
955
September1st to 15thNight
57%
495
27%
1650
27%
495
62%
495
31%
950
September16th to endNight
55%
574
30%
1784
21%
574
64%
574
34%
1017
October1st to 15thNight
43%
660
29%
1980
19%
660
51%
660
33%
1137
October16th to endNight
29%
704
25%
2112
12%
704
41%
704
29%
1258
November1st to 15thNight
34%
700
28%
2248
14%
700
50%
700
29%
1256
November16th to endNight
25%
817
21%
2437
11%
817
36%
817
23%
1544
December1st to 15thNight
20%
900
16%
2520
5%
900
30%
900
18%
1801
December16th to endNight
17%
960
16%
2688
5%
960
27%
960
16%
1970

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
13%6%25%5%2445%7%41%
46031
Night
13%6%34424446%45%
45811
TransparencyDay
41%6%12%23%14%2
45720
Night
39%5%11%24%16%2
45627
SeeingDay
16%10%27%26%14%4
5228
Night
18%12%30%25%11%1
15432

By Month

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%8%38%5%34435%39%
1492
16th to endDay
12%11%45%5%2445%6%37%
1728
February1st to 15thDay
15%9%46%5%24346%38%
1576
16th to endDay
12%11%37%5%24436%38%
1580
March1st to 15thDay
15%10%46%5%3434437%
1926
16th to endDay
18%10%46%5%245%45%31%
2153
April1st to 15thDay
16%7%25%5%3434442%
2151
16th to endDay
20%6%35%433446%36%
2111
May1st to 15thDay
18%6%35%5%3445%7%34%
2108
16th to endDay
14%5%35%5%35%45%6%38%
2393
June1st to 15thDay
10%425%5%245%7%10%41%
2310
16th to endDay
8%313435%6%6%12%44%
2310
July1st to 15thDay
10%214435%5%6%10%44%
2310
16th to endDay
6%3145%25%6%7%12%44%
2328
August1st to 15thDay
7%415%5%36%6%6%9%43%
2128
16th to endDay
9%425%5%2446%9%44%
2100
September1st to 15thDay
13%5%15%425%45%7%45%
1980
16th to endDay
10%4245%2445%8%48%
1830
October1st to 15thDay
14%5%24413345%50%
1650
16th to endDay
15%42432223453%
1760
November1st to 15thDay
15%5%22313346%50%
1610
16th to endDay
17%7%33423346%42%
1521
December1st to 15thDay
16%10%36%424347%37%
1440
16th to endDay
17%11%46%423435%36%
1536
January1st to 15thNight
13%8%36%434445%42%
2443
16th to endNight
12%9%37%424346%41%
2496
February1st to 15thNight
14%10%5%6%5%35%35%435%
2275
16th to endNight
14%9%36%322335%45%
1893
March1st to 15thNight
19%8%2443333440%
2045
16th to endNight
20%8%35%5%3445%6%31%
2067
April1st to 15thNight
12%7%25%334345%46%
1797
16th to endNight
17%5%24313347%45%
1760
May1st to 15thNight
15%5%34434449%41%
1508
16th to endNight
13%4245%34448%42%
1368
June1st to 15thNight
7%324425%46%7%50%
1320
16th to endNight
6%324325%5%410%51%
1320
July1st to 15thNight
10%2233235%5%9%51%
1320
16th to endNight
5%222425%47%10%52%
1529
August1st to 15thNight
42144245%5%10%53%
1501
16th to endNight
6%31442445%8%53%
1750
September1st to 15thNight
14%32332345%6%50%
1650
16th to endNight
8%41332345%7%54%
1784
October1st to 15thNight
11%323324436%54%
1980
16th to endNight
16%42332323452%
2112
November1st to 15thNight
11%5%23312346%54%
2248
16th to endNight
15%8%2331343447%
2437
December1st to 15thNight
18%11%35%424345%34%
2520
16th to endNight
19%11%5%6%42434432%
2688

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
46%5%8%24%14%1
1493
16th to endDay
46%415%23%9%1
1728
February1st to 15thDay
48%412%23%9%1
1577
16th to endDay
47%5%11%22%11%1
1580
March1st to 15thDay
49%410%22%11%1
1926
16th to endDay
54%5%12%18%9%
2155
April1st to 15thDay
45%49%22%16%1
2151
16th to endDay
48%5%11%20%12%1
2111
May1st to 15thDay
48%6%12%21%9%
2108
16th to endDay
43%8%13%18%13%2
2397
June1st to 15thDay
37%8%13%25%13%1
2310
16th to endDay
30%8%17%25%14%3
2310
July1st to 15thDay
34%8%14%27%11%3
2161
16th to endDay
30%9%17%28%12%1
2172
August1st to 15thDay
33%8%13%26%15%1
2114
16th to endDay
36%6%13%20%18%5%
2100
September1st to 15thDay
38%6%9%20%20%4
1980
16th to endDay
33%6%9%29%17%3
1830
October1st to 15thDay
36%48%25%19%5%
1650
16th to endDay
35%39%27%20%3
1760
November1st to 15thDay
34%411%21%22%5%
1610
16th to endDay
42%410%27%13%
1521
December1st to 15thDay
48%413%24%9%
1440
16th to endDay
51%410%21%10%2
1536
January1st to 15thNight
44%410%24%15%
2443
16th to endNight
44%5%13%23%13%
2496
February1st to 15thNight
50%5%10%19%12%1
2285
16th to endNight
42%312%24%15%1
1893
March1st to 15thNight
48%310%20%14%1
2045
16th to endNight
52%6%10%21%8%
2067
April1st to 15thNight
38%6%9%25%17%3
1797
16th to endNight
39%410%27%15%2
1760
May1st to 15thNight
39%9%16%21%13%
1509
16th to endNight
39%7%15%18%15%3
1370
June1st to 15thNight
30%6%15%28%17%1
1320
16th to endNight
27%7%14%27%18%4
1320
July1st to 15thNight
29%7%11%30%16%3
1240
16th to endNight
25%6%16%32%16%1
1422
August1st to 15thNight
24%7%12%30%20%2
1491
16th to endNight
27%6%12%24%23%5%
1750
September1st to 15thNight
33%5%8%24%22%5%
1650
16th to endNight
30%5%9%26%24%3
1784
October1st to 15thNight
31%5%9%25%22%5%
1980
16th to endNight
36%28%26%20%4
2112
November1st to 15thNight
31%411%24%20%7%
2248
16th to endNight
41%310%27%16%1
2437
December1st to 15thNight
50%412%20%11%
2520
16th to endNight
54%310%18%11%2
2688

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
27%32%32%6%1
90
16th to endDay
22%29%34%11%2
96
February1st to 15thDay
32%23%30%12%2
90
16th to endDay
28%22%33%14%1
81
March1st to 15thDay
35%17%38%6%1
90
16th to endDay
26%25%33%13%
139
April1st to 15thDay
23%15%31%22%7%
270
16th to endDay
24%12%32%21%8%
254
May1st to 15thDay
19%18%29%21%8%1
321
16th to endDay
19%11%32%23%8%4
437
June1st to 15thDay
11%7%30%32%12%5%
420
16th to endDay
10%432%33%15%3
420
July1st to 15thDay
15%222%33%19%7%
400
16th to endDay
7%220%33%30%6%
445
August1st to 15thDay
8%115%39%28%4
401
16th to endDay
9%5%19%27%29%8%
268
September1st to 15thDay
13%5%14%35%23%8%
255
16th to endDay
10%8%25%26%21%8%
199
October1st to 15thDay
13%14%32%25%12%2
90
16th to endDay
17%7%48%22%3
96
November1st to 15thDay
8%8%32%25%17%6%
90
16th to endDay
42%20%18%15%3
90
December1st to 15thDay
27%17%37%10%42
90
16th to endDay
31%26%32%9%1
96
January1st to 15thNight
22%19%36%16%5%
900
16th to endNight
21%20%35%20%1
960
February1st to 15thNight
23%19%33%20%2
877
16th to endNight
23%19%36%18%1
631
March1st to 15thNight
28%14%35%19%2
605
16th to endNight
24%13%37%19%4
576
April1st to 15thNight
17%21%33%21%5%
539
16th to endNight
17%10%37%27%6%
528
May1st to 15thNight
18%7%33%30%9%
495
16th to endNight
15%433%29%14%2
515
June1st to 15thNight
8%5%27%37%19%1
495
16th to endNight
7%327%39%20%1
495
July1st to 15thNight
10%216%42%23%3
465
16th to endNight
6%17%34%37%2
522
August1st to 15thNight
5%112%42%36%2
494
16th to endNight
7%114%39%32%5%
525
September1st to 15thNight
15%416%32%25%5%
495
16th to endNight
10%6%21%29%25%5%
574
October1st to 15thNight
11%8%32%25%18%3
660
16th to endNight
19%14%35%22%8%
704
November1st to 15thNight
15%16%31%25%11%
700
16th to endNight
23%17%32%20%5%
817
December1st to 15thNight
27%17%31%18%4
900
16th to endNight
29%16%33%18%2
960
Page generated at 2017-04-27 16:48:58. Version ac04

Copyright 2017 A. Danko


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