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 2018-01-12.

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
35%
16368
21%
48379
12%
16320
44%
16320
26%
30568

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%
956
19%
2598
6%
951
29%
951
21%
1763
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
29%
540
22%
1800
12%
540
44%
540
24%
1112
May1st to 15thNight
37%
540
17%
1645
11%
539
44%
539
24%
1073
May16th to endNight
40%
563
20%
1497
11%
561
47%
561
30%
986
June1st to 15thNight
54%
540
20%
1440
12%
540
58%
540
40%
857
June16th to endNight
54%
540
22%
1440
11%
540
61%
540
41%
849
July1st to 15thNight
62%
510
19%
1360
13%
510
65%
510
39%
823
July16th to endNight
68%
564
23%
1544
21%
531
71%
531
42%
852
August1st to 15thNight
71%
539
24%
1628
26%
536
73%
536
40%
894
August16th to endNight
68%
573
24%
1910
27%
573
72%
573
37%
1030
September1st to 15thNight
58%
540
26%
1800
26%
540
63%
540
32%
1022
September16th to endNight
56%
627
31%
1947
23%
627
65%
627
35%
1101
October1st to 15thNight
42%
720
27%
2160
18%
720
50%
720
32%
1263
October16th to endNight
30%
768
27%
2304
13%
768
42%
768
29%
1360
November1st to 15thNight
33%
760
26%
2441
14%
760
47%
760
28%
1400
November16th to endNight
25%
885
23%
2640
11%
885
38%
885
24%
1652
December1st to 15thNight
22%
975
16%
2730
5%
975
32%
975
19%
1911
December16th to endNight
16%
1040
17%
2912
5%
1040
27%
1040
15%
2139

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%42445%7%42%
48955
Night
13%6%24424446%45%
48565
TransparencyDay
40%6%12%23%14%2
48644
Night
39%5%11%24%16%2
48381
SeeingDay
16%10%27%26%14%3
6249
Night
18%12%30%25%12%1
16368

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%9%37%5%34446%39%
1581
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
21%6%35%433446%35%
2160
May1st to 15thDay
18%6%35%5%3445%7%35%
2301
16th to endDay
13%5%35%5%35%45%6%39%
2617
June1st to 15thDay
9%425%5%245%7%9%43%
2520
16th to endDay
7%313435%6%6%12%45%
2520
July1st to 15thDay
9%214435%5%6%10%45%
2520
16th to endDay
6%3134246%7%11%45%
2514
August1st to 15thDay
8%4145%35%5%6%9%43%
2321
16th to endDay
9%425%5%345%6%9%44%
2292
September1st to 15thDay
12%5%15%42445%7%47%
2160
16th to endDay
10%42442445%8%48%
1996
October1st to 15thDay
15%5%25%413345%48%
1800
16th to endDay
14%5%24322235%53%
1920
November1st to 15thDay
15%6%22313346%49%
1747
16th to endDay
16%7%34423346%44%
1648
December1st to 15thDay
15%9%35%424346%39%
1560
16th to endDay
17%11%46%423446%35%
1664
January1st to 15thNight
13%8%36%433445%41%
2598
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
18%5%24313347%44%
1800
May1st to 15thNight
15%434434448%43%
1645
16th to endNight
13%4245%34448%44%
1496
June1st to 15thNight
7%22442446%7%52%
1440
16th to endNight
6%314325%5%410%51%
1440
July1st to 15thNight
9%2233235%5%9%52%
1440
16th to endNight
5%21342446%9%53%
1651
August1st to 15thNight
5%2144245%5%10%53%
1638
16th to endNight
5%31432445%9%54%
1910
September1st to 15thNight
13%31332345%6%52%
1800
16th to endNight
7%41432345%7%54%
1947
October1st to 15thNight
12%323324436%53%
2160
16th to endNight
15%423322335%52%
2304
November1st to 15thNight
11%6%24312346%52%
2441
16th to endNight
14%7%2332343447%
2640
December1st to 15thNight
17%10%35%434345%36%
2730
16th to endNight
18%12%5%6%42434432%
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
46%5%8%23%13%2
1582
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
49%5%11%20%12%1
2160
May1st to 15thDay
47%6%12%22%10%
2301
16th to endDay
42%8%13%18%14%2
2621
June1st to 15thDay
35%8%12%25%15%1
2520
16th to endDay
30%8%17%25%15%3
2520
July1st to 15thDay
33%8%14%27%12%3
2371
16th to endDay
29%9%16%29%14%1
2358
August1st to 15thDay
34%8%13%26%15%1
2307
16th to endDay
35%6%13%20%18%5%
2292
September1st to 15thDay
36%6%9%23%20%4
2160
16th to endDay
32%5%9%29%18%2
1996
October1st to 15thDay
38%48%24%19%5%
1800
16th to endDay
35%39%27%20%3
1920
November1st to 15thDay
35%411%21%21%5%
1747
16th to endDay
41%49%28%14%
1648
December1st to 15thDay
45%414%25%10%
1560
16th to endDay
51%410%20%10%2
1664
January1st to 15thNight
44%410%24%14%1
2598
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
40%49%27%15%2
1800
May1st to 15thNight
38%8%14%21%15%
1646
16th to endNight
38%7%15%19%16%3
1498
June1st to 15thNight
28%6%14%28%20%1
1440
16th to endNight
26%7%13%28%19%4
1440
July1st to 15thNight
29%7%11%31%17%3
1360
16th to endNight
25%6%15%32%18%1
1544
August1st to 15thNight
25%7%13%31%20%2
1628
16th to endNight
26%6%12%24%23%5%
1910
September1st to 15thNight
32%5%9%24%23%5%
1800
16th to endNight
29%5%9%27%24%3
1947
October1st to 15thNight
32%5%9%25%21%6%
2160
16th to endNight
35%38%26%21%4
2304
November1st to 15thNight
33%411%24%19%7%
2441
16th to endNight
39%39%27%17%1
2640
December1st to 15thNight
48%412%21%12%
2730
16th to endNight
54%310%17%10%2
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
25%28%37%7%1
123
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
28%11%31%20%7%
270
May1st to 15thDay
20%17%28%22%8%2
390
16th to endDay
18%12%34%23%7%3
517
June1st to 15thDay
10%6%29%35%13%5%
495
16th to endDay
10%6%35%31%13%3
495
July1st to 15thDay
15%222%34%20%5%
475
16th to endDay
7%220%32%31%5%
515
August1st to 15thDay
10%216%38%27%4
474
16th to endDay
8%421%31%27%7%
332
September1st to 15thDay
12%5%15%32%25%9%
315
16th to endDay
9%7%24%31%20%7%
254
October1st to 15thDay
21%11%31%25%8%1
135
16th to endDay
20%10%41%22%4
144
November1st to 15thDay
17%9%35%21%11%4
135
16th to endDay
32%17%25%21%2
135
December1st to 15thDay
24%23%33%11%42
135
16th to endDay
29%25%36%8%
144
January1st to 15thNight
22%19%35%16%4
956
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
19%10%37%26%6%
540
May1st to 15thNight
17%8%32%30%10%
540
16th to endNight
14%5%34%29%13%1
563
June1st to 15thNight
7%427%37%20%1
540
16th to endNight
7%428%39%19%1
540
July1st to 15thNight
10%116%41%24%3
510
16th to endNight
6%18%35%37%2
564
August1st to 15thNight
5%112%41%36%2
539
16th to endNight
7%115%38%32%4
573
September1st to 15thNight
14%416%31%26%6%
540
16th to endNight
9%7%21%30%25%5%
627
October1st to 15thNight
13%7%32%24%17%3
720
16th to endNight
18%15%33%22%8%
768
November1st to 15thNight
17%15%32%24%10%
760
16th to endNight
22%17%33%20%6%
885
December1st to 15thNight
26%18%30%19%4
975
16th to endNight
28%16%33%18%2
1040
Page generated at 2018-01-12 21:01:26. Version ac04

Copyright 2018 A. Danko


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