Big Level Warden Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Big Level Warden Observatory clear sky chart from 2005-11-05 to 2017-09-20.

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%
15036
23%
47025
17%
14991
59%
14991
29%
28502

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
33%
720
26%
2148
12%
716
46%
716
27%
1312
January16th to endNight
29%
768
25%
2304
12%
768
41%
768
24%
1481
February1st to 15thNight
33%
704
26%
2110
11%
700
45%
700
28%
1276
February16th to endNight
29%
631
22%
1893
10%
631
38%
631
23%
1234
March1st to 15thNight
34%
696
22%
2136
12%
696
42%
696
24%
1385
March16th to endNight
46%
576
25%
1996
18%
576
56%
576
30%
1123
April1st to 15thNight
44%
539
24%
1797
19%
539
53%
539
27%
1078
April16th to endNight
52%
540
27%
1800
23%
540
62%
540
38%
942
May1st to 15thNight
58%
539
21%
1799
17%
539
66%
539
32%
1024
May16th to endNight
68%
562
21%
1753
19%
561
72%
561
34%
1018
June1st to 15thNight
72%
540
12%
1620
13%
540
73%
540
30%
1023
June16th to endNight
75%
540
16%
1595
15%
540
76%
540
30%
1012
July1st to 15thNight
79%
510
12%
1642
15%
510
80%
510
29%
1030
July16th to endNight
79%
564
13%
1772
16%
531
79%
531
25%
1146
August1st to 15thNight
81%
539
10%
1788
13%
536
81%
536
27%
1112
August16th to endNight
70%
573
14%
1910
17%
573
71%
573
20%
1300
September1st to 15thNight
69%
546
19%
1806
21%
546
71%
546
27%
1133
September16th to endNight
66%
677
25%
1870
21%
677
67%
677
33%
1162
October1st to 15thNight
63%
660
33%
1840
25%
660
68%
660
45%
1007
October16th to endNight
55%
704
35%
2112
29%
704
62%
704
42%
1120
November1st to 15thNight
54%
700
31%
2197
25%
700
63%
700
36%
1207
November16th to endNight
48%
720
30%
2340
23%
720
58%
720
33%
1294
December1st to 15thNight
39%
720
25%
2340
17%
720
48%
720
25%
1416
December16th to endNight
33%
768
20%
2457
13%
768
41%
768
19%
1667

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
12%5%35%6%35%5%5%7%38%
47711
Night
11%42442445%8%46%
47249
TransparencyDay
42%7%10%15%16%6%
47436
Night
34%7%13%18%17%8%
47029
SeeingDay
13%5%16%23%24%15%
4997
Night
13%6%20%29%24%6%
15038

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
15%5%25%323347%45%
1790
16th to endDay
19%5%2332423447%
1920
February1st to 15thDay
14%425%5%14447%45%
1750
16th to endDay
16%7%25%424446%41%
1580
March1st to 15thDay
17%5%34434336%42%
1833
16th to endDay
12%5%345%35%447%43%
2224
April1st to 15thDay
13%5%246%3446%7%40%
2151
16th to endDay
11%5%245%35%45%7%43%
2160
May1st to 15thDay
11%5%26%5%35%5%5%8%40%
2151
16th to endDay
9%6%26%6%36%5%6%8%37%
2358
June1st to 15thDay
8%5%37%7%5%7%7%8%9%29%
2340
16th to endDay
7%5%37%9%5%8%7%7%9%27%
2340
July1st to 15thDay
8%7%37%9%6%9%7%7%8%23%
2176
16th to endDay
10%6%47%9%5%9%8%7%9%22%
2276
August1st to 15thDay
9%5%37%8%6%8%7%8%10%25%
2160
16th to endDay
12%6%37%8%5%7%7%6%8%25%
2292
September1st to 15thDay
11%6%36%6%46%5%6%7%34%
2141
16th to endDay
10%5%25%6%45%447%42%
1859
October1st to 15thDay
8%4245%33346%55%
1788
16th to endDay
7%324323447%55%
1760
November1st to 15thDay
10%424323436%55%
1659
16th to endDay
10%42441233455%
1620
December1st to 15thDay
15%6%35%5%23336%44%
1620
16th to endDay
22%7%35%423446%35%
1763
January1st to 15thNight
15%5%24313446%48%
2148
16th to endNight
19%6%24323335%44%
2304
February1st to 15thNight
14%5%24323346%49%
2103
16th to endNight
17%7%24323345%43%
1893
March1st to 15thNight
16%6%24424446%41%
2136
16th to endNight
13%423323446%52%
1996
April1st to 15thNight
12%5%24324447%47%
1797
16th to endNight
10%313313349%55%
1800
May1st to 15thNight
8%32332446%9%49%
1799
16th to endNight
6%314435%5%6%10%48%
1752
June1st to 15thNight
6%315%426%8%9%11%40%
1620
16th to endNight
6%3245%346%8%11%43%
1595
July1st to 15thNight
44245%25%6%8%11%41%
1742
16th to endNight
5%325%5%46%6%9%14%35%
1892
August1st to 15thNight
33145%35%8%9%14%39%
1800
16th to endNight
8%416%6%36%6%8%11%35%
1910
September1st to 15thNight
8%435%5%35%5%8%9%40%
1806
16th to endNight
8%425%6%3345%7%46%
1870
October1st to 15thNight
6%323313347%59%
1840
16th to endNight
12%313312335%61%
2112
November1st to 15thNight
9%41431335%6%55%
2197
16th to endNight
10%423323335%56%
2340
December1st to 15thNight
13%6%24424347%46%
2340
16th to endNight
19%7%36%423345%37%
2457

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
39%47%14%22%12%
1791
16th to endDay
43%3415%23%9%
1920
February1st to 15thDay
38%49%14%22%10%
1752
16th to endDay
42%5%6%15%22%8%
1580
March1st to 15thDay
43%46%17%19%7%
1833
16th to endDay
40%5%9%15%21%7%
2226
April1st to 15thDay
40%5%9%16%19%8%
2151
16th to endDay
37%6%11%18%19%6%
2160
May1st to 15thDay
40%7%10%17%16%7%
2151
16th to endDay
42%8%12%18%16%2
2362
June1st to 15thDay
45%12%14%18%8%1
2340
16th to endDay
47%11%17%15%7%
2340
July1st to 15thDay
53%12%15%11%5%1
2047
16th to endDay
52%13%15%13%3
2133
August1st to 15thDay
50%14%17%11%6%
2148
16th to endDay
51%13%14%11%7%1
2292
September1st to 15thDay
46%8%13%16%9%4
2141
16th to endDay
40%7%11%15%16%7%
1859
October1st to 15thDay
30%5%9%14%23%16%
1788
16th to endDay
28%48%11%27%19%
1760
November1st to 15thDay
31%46%16%31%10%
1659
16th to endDay
31%35%16%24%17%
1620
December1st to 15thDay
42%39%18%19%6%
1620
16th to endDay
50%47%16%16%4
1763
January1st to 15thNight
37%48%15%24%9%
2148
16th to endNight
42%35%14%23%10%
2304
February1st to 15thNight
36%47%17%22%12%
2112
16th to endNight
42%45%15%19%11%
1893
March1st to 15thNight
42%5%9%14%21%6%
2136
16th to endNight
32%5%11%19%22%8%
1996
April1st to 15thNight
36%6%9%19%18%10%
1797
16th to endNight
27%413%23%22%8%
1800
May1st to 15thNight
30%7%13%21%21%6%
1800
16th to endNight
29%9%17%23%19%2
1754
June1st to 15thNight
31%12%22%22%10%
1620
16th to endNight
32%11%21%24%9%1
1595
July1st to 15thNight
30%13%29%19%6%
1642
16th to endNight
32%16%27%21%2
1772
August1st to 15thNight
27%17%30%17%5%1
1788
16th to endNight
38%15%21%13%7%3
1910
September1st to 15thNight
36%9%19%16%12%6%
1806
16th to endNight
35%6%16%17%15%8%
1870
October1st to 15thNight
24%410%19%23%17%
1840
16th to endNight
26%26%15%26%22%
2112
November1st to 15thNight
29%37%16%28%13%
2197
16th to endNight
30%46%17%21%19%
2340
December1st to 15thNight
38%49%21%18%6%
2340
16th to endNight
47%5%7%18%15%5%
2457

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%15%32%18%10%1
90
16th to endDay
27%25%35%8%4
96
February1st to 15thDay
17%13%41%21%6%
90
16th to endDay
14%22%39%18%4
81
March1st to 15thDay
26%21%38%12%1
90
16th to endDay
20%8%26%27%17%
210
April1st to 15thDay
20%11%24%25%17%1
270
16th to endDay
14%6%25%31%17%4
270
May1st to 15thDay
9%7%25%26%25%5%
288
16th to endDay
12%219%29%20%14%
331
June1st to 15thDay
12%29%26%29%20%
315
16th to endDay
9%7%25%29%26%
315
July1st to 15thDay
9%219%36%32%
305
16th to endDay
7%6%16%37%30%
326
August1st to 15thDay
8%7%19%35%28%
313
16th to endDay
11%16%20%31%29%
332
September1st to 15thDay
9%310%24%30%21%
315
16th to endDay
13%15%31%34%13%
270
October1st to 15thDay
5%416%33%29%10%
228
16th to endDay
14%321%31%19%9%
96
November1st to 15thDay
23%234%26%11%2
90
16th to endDay
13%16%32%23%13%1
90
December1st to 15thDay
21%17%40%14%42
90
16th to endDay
42%9%22%16%8%
96
January1st to 15thNight
19%12%31%27%8%
720
16th to endNight
22%13%29%29%5%
768
February1st to 15thNight
16%12%33%28%8%
704
16th to endNight
21%14%32%27%4
631
March1st to 15thNight
21%10%30%30%7%
696
16th to endNight
13%8%28%33%14%1
576
April1st to 15thNight
15%7%29%30%16%
539
16th to endNight
12%5%26%36%18%1
540
May1st to 15thNight
9%421%40%21%2
540
16th to endNight
6%116%37%32%6%
563
June1st to 15thNight
7%7%31%42%10%
540
16th to endNight
7%6%25%45%15%
540
July1st to 15thNight
5%218%50%23%
510
16th to endNight
4317%46%26%
564
August1st to 15thNight
4216%48%27%
539
16th to endNight
8%1417%46%21%
573
September1st to 15thNight
8%18%22%41%18%
546
16th to endNight
10%8%33%38%8%
677
October1st to 15thNight
8%120%33%33%2
660
16th to endNight
13%5%21%28%27%3
704
November1st to 15thNight
11%6%22%35%20%3
700
16th to endNight
11%9%26%35%15%1
720
December1st to 15thNight
17%10%28%29%13%
720
16th to endNight
23%9%29%27%10%
768
Page generated at 2017-09-21 06:18:13. Version ac04

Copyright 2017 A. Danko


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