Bowser Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bowser Observatory clear sky chart from 2005-11-05 to 2019-06-24.

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
50%
17717
25%
54046
18%
17674
57%
17674
32%
31868

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
41%
1046
26%
2717
13%
1045
49%
1045
32%
1734
January16th to endNight
39%
1011
27%
2803
14%
1011
47%
1011
30%
1759
February1st to 15thNight
34%
824
25%
2468
13%
819
44%
819
27%
1525
February16th to endNight
25%
736
25%
2206
8%
736
38%
736
26%
1359
March1st to 15thNight
31%
652
26%
2332
14%
652
46%
652
24%
1405
March16th to endNight
32%
672
21%
2464
14%
672
43%
672
24%
1442
April1st to 15thNight
31%
629
23%
2307
14%
629
45%
629
26%
1312
April16th to endNight
32%
624
24%
2053
15%
624
46%
624
26%
1269
May1st to 15thNight
37%
629
23%
1890
17%
629
45%
629
28%
1189
May16th to endNight
46%
658
24%
1972
18%
657
58%
657
34%
1141
June1st to 15thNight
65%
630
24%
1890
23%
630
72%
630
48%
961
June16th to endNight
66%
609
20%
1827
20%
609
70%
609
36%
1061
July1st to 15thNight
77%
555
19%
1665
21%
555
80%
555
42%
924
July16th to endNight
80%
612
24%
1738
26%
579
85%
579
44%
928
August1st to 15thNight
87%
575
27%
1802
32%
572
88%
572
52%
859
August16th to endNight
78%
621
19%
2139
23%
621
79%
621
34%
1192
September1st to 15thNight
73%
585
19%
2145
23%
585
74%
585
29%
1247
September16th to endNight
65%
582
22%
2145
24%
582
67%
582
26%
1266
October1st to 15thNight
70%
585
32%
2145
33%
585
73%
585
38%
1100
October16th to endNight
61%
831
34%
2495
25%
831
65%
831
43%
1317
November1st to 15thNight
53%
831
27%
2471
18%
831
58%
831
32%
1486
November16th to endNight
50%
1050
30%
2730
15%
1050
56%
1050
39%
1635
December1st to 15thNight
41%
1050
28%
2730
16%
1050
47%
1050
30%
1793
December16th to endNight
37%
1120
22%
2912
11%
1120
43%
1120
27%
1964

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%5%245%3445%7%43%
54764
Night
13%423323347%50%
54246
Cloud CoverDay
14%5%245%3445%7%43%
54762
Night
13%413323347%50%
54246
TransparencyDay
39%5%10%19%17%8%
54462
Night
33%5%11%20%17%10%
54051
SeeingDay
15%5%19%29%24%6%
7608
Night
15%5%23%35%18%1
17723

By Month

Percentage Cloud Cover SW (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
18%5%34422245%45%
1881
16th to endDay
17%6%23223346%48%
2135
February1st to 15thDay
20%7%14313335%45%
2050
16th to endDay
21%5%23322346%42%
1840
March1st to 15thDay
21%6%24423345%41%
2288
16th to endDay
18%6%23423336%45%
2464
April1st to 15thDay
15%5%25%423346%44%
2301
16th to endDay
16%6%35%432435%42%
2507
May1st to 15thDay
15%6%36%6%345%46%36%
2721
16th to endDay
14%6%35%5%45%5%5%8%35%
2846
June1st to 15thDay
5%415%5%36%5%7%8%45%
2730
16th to endDay
11%6%36%6%46%5%7%9%33%
2640
July1st to 15thDay
9%435%7%45%6%5%8%39%
2535
16th to endDay
7%4135%36%6%7%10%42%
2674
August1st to 15thDay
3212435%5%6%11%54%
2397
16th to endDay
8%325%7%45%6%6%9%39%
2413
September1st to 15thDay
11%5%35%7%45%5%6%7%36%
2145
16th to endDay
13%5%25%5%35%45%7%40%
2145
October1st to 15thDay
10%424436%5%46%48%
2132
16th to endDay
11%413312235%59%
2080
November1st to 15thDay
15%7%25%5%2345%6%40%
2044
16th to endDay
14%5%1442233352%
1890
December1st to 15thDay
22%6%23423345%41%
1890
16th to endDay
18%8%24423445%40%
2016
January1st to 15thNight
18%413313345%48%
2717
16th to endNight
19%42432333448%
2803
February1st to 15thNight
20%5%23213345%47%
2462
16th to endNight
19%5%23323246%46%
2206
March1st to 15thNight
18%6%24323335%46%
2332
16th to endNight
16%6%23423347%45%
2464
April1st to 15thNight
14%5%2432335%8%48%
2307
16th to endNight
18%434413335%46%
2053
May1st to 15thNight
14%5%2443445%7%43%
1889
16th to endNight
10%42442335%10%48%
1971
June1st to 15thNight
4312323449%60%
1890
16th to endNight
6%3243245%6%9%51%
1827
July1st to 15thNight
5%31332346%11%54%
1755
16th to endNight
6%21223346%9%56%
1846
August1st to 15thNight
1123235%6%10%62%
1812
16th to endNight
7%3144145%6%12%49%
2139
September1st to 15thNight
9%5%25%425%5%5%8%46%
2145
16th to endNight
10%6%25%5%3445%9%43%
2145
October1st to 15thNight
9%312423446%57%
2145
16th to endNight
11%31321223463%
2495
November1st to 15thNight
12%5%14423345%50%
2471
16th to endNight
14%413322335%55%
2730
December1st to 15thNight
19%5%23323235%47%
2730
16th to endNight
20%7%24423335%44%
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
18%5%34413236%45%
1881
16th to endDay
17%5%23222346%48%
2135
February1st to 15thDay
20%6%15%31224445%
2050
16th to endDay
21%6%23323346%42%
1840
March1st to 15thDay
21%6%2432333442%
2288
16th to endDay
18%6%24423336%45%
2462
April1st to 15thDay
15%5%25%423346%44%
2301
16th to endDay
16%7%445%23335%43%
2507
May1st to 15thDay
16%6%36%6%34446%36%
2721
16th to endDay
15%6%345%445%5%8%35%
2846
June1st to 15thDay
5%4145%46%5%6%9%45%
2730
16th to endDay
11%6%26%6%46%5%7%9%33%
2640
July1st to 15thDay
9%435%7%46%5%5%8%39%
2535
16th to endDay
7%4245%46%6%7%11%41%
2674
August1st to 15thDay
3213425%5%6%11%54%
2397
16th to endDay
8%326%7%45%5%7%9%39%
2413
September1st to 15thDay
11%6%36%6%45%5%6%6%36%
2145
16th to endDay
13%5%25%5%345%5%7%40%
2145
October1st to 15thDay
9%414435%446%48%
2132
16th to endDay
11%31332233459%
2080
November1st to 15thDay
15%7%245%24346%40%
2044
16th to endDay
14%5%1442233452%
1890
December1st to 15thDay
22%5%23323335%42%
1890
16th to endDay
19%7%24423446%40%
2016
January1st to 15thNight
18%5%13313345%48%
2717
16th to endNight
18%5%23322435%48%
2803
February1st to 15thNight
21%5%13213335%47%
2462
16th to endNight
20%5%23323246%46%
2206
March1st to 15thNight
18%7%1432333446%
2332
16th to endNight
17%6%23413347%45%
2464
April1st to 15thNight
14%5%24423348%48%
2307
16th to endNight
18%434413335%46%
2053
May1st to 15thNight
14%5%2443345%7%43%
1889
16th to endNight
10%42442336%10%47%
1971
June1st to 15thNight
5%312323449%60%
1890
16th to endNight
6%4243245%6%8%50%
1827
July1st to 15thNight
5%31332346%11%53%
1755
16th to endNight
6%21233446%10%55%
1846
August1st to 15thNight
11113235%7%10%61%
1812
16th to endNight
7%2144245%7%11%49%
2139
September1st to 15thNight
9%5%25%425%45%7%46%
2145
16th to endNight
10%5%25%5%3345%8%44%
2145
October1st to 15thNight
9%313423446%56%
2145
16th to endNight
11%31321223463%
2495
November1st to 15thNight
12%424324345%50%
2471
16th to endNight
14%414222235%55%
2730
December1st to 15thNight
19%5%23313335%47%
2730
16th to endNight
20%7%24422335%44%
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
41%35%15%19%13%
1882
16th to endDay
38%26%15%23%13%
2135
February1st to 15thDay
42%36%14%18%14%
2051
16th to endDay
43%36%14%19%12%
1840
March1st to 15thDay
45%47%12%17%12%
2288
16th to endDay
40%38%17%18%10%
2464
April1st to 15thDay
40%37%16%18%12%
2301
16th to endDay
43%37%18%16%10%
2507
May1st to 15thDay
47%5%8%15%17%5%
2721
16th to endDay
44%5%10%18%16%3
2850
June1st to 15thDay
32%7%13%23%19%4
2730
16th to endDay
44%6%11%21%12%2
2640
July1st to 15thDay
39%7%16%22%12%1
2396
16th to endDay
31%7%19%29%11%
2519
August1st to 15thDay
22%7%16%36%15%1
2383
16th to endDay
38%8%16%23%10%2
2413
September1st to 15thDay
45%8%9%17%15%4
2145
16th to endDay
40%7%10%17%15%8%
2145
October1st to 15thDay
34%5%11%18%18%11%
2132
16th to endDay
28%35%15%25%20%
2080
November1st to 15thDay
43%48%17%15%9%
2044
16th to endDay
36%36%13%21%17%
1890
December1st to 15thDay
46%36%16%18%9%
1890
16th to endDay
45%37%14%18%9%
2016
January1st to 15thNight
38%36%15%19%16%
2717
16th to endNight
38%35%15%21%16%
2803
February1st to 15thNight
39%36%14%18%18%
2472
16th to endNight
39%35%17%19%13%
2206
March1st to 15thNight
41%38%15%16%14%
2332
16th to endNight
38%410%15%18%11%
2464
April1st to 15thNight
35%5%9%17%17%14%
2307
16th to endNight
40%49%17%15%11%
2053
May1st to 15thNight
38%6%10%19%16%8%
1890
16th to endNight
32%414%29%14%3
1973
June1st to 15thNight
20%6%15%30%25%3
1890
16th to endNight
28%8%17%29%13%2
1827
July1st to 15thNight
22%8%23%30%12%1
1665
16th to endNight
20%9%25%34%9%
1738
August1st to 15thNight
15%7%25%37%13%
1802
16th to endNight
26%9%24%27%8%2
2139
September1st to 15thNight
34%6%18%21%14%5%
2145
16th to endNight
36%6%14%19%14%8%
2145
October1st to 15thNight
26%5%12%26%17%11%
2145
16th to endNight
26%35%17%26%20%
2495
November1st to 15thNight
35%411%19%17%12%
2471
16th to endNight
31%37%16%21%19%
2730
December1st to 15thNight
40%35%18%20%10%
2730
16th to endNight
44%35%13%21%12%
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
24%10%31%25%8%1
180
16th to endDay
18%14%29%24%11%1
192
February1st to 15thDay
32%13%27%16%10%
180
16th to endDay
29%16%33%17%1
159
March1st to 15thDay
26%15%36%18%3
180
16th to endDay
16%8%36%29%8%
192
April1st to 15thDay
16%13%35%28%7%
180
16th to endDay
17%8%37%28%7%
399
May1st to 15thDay
17%9%34%29%8%
618
16th to endDay
19%5%22%36%15%1
677
June1st to 15thDay
6%13%44%30%4
645
16th to endDay
12%111%35%30%8%
611
July1st to 15thDay
7%8%32%40%10%
550
16th to endDay
41425%50%14%
595
August1st to 15thDay
5%329%45%16%
461
16th to endDay
9%6%28%36%18%
325
September1st to 15thDay
16%16%17%43%15%
180
16th to endDay
16%7%19%40%17%
180
October1st to 15thDay
7%10%32%35%14%
180
16th to endDay
24%418%22%22%6%
192
November1st to 15thDay
28%10%17%27%13%2
180
16th to endDay
18%13%26%21%13%6%
180
December1st to 15thDay
25%11%27%22%8%5%
180
16th to endDay
31%8%32%19%6%1
192
January1st to 15thNight
21%7%24%33%11%
1050
16th to endNight
21%7%27%34%9%
1011
February1st to 15thNight
24%9%28%30%7%
824
16th to endNight
25%10%36%24%2
736
March1st to 15thNight
20%8%34%30%5%
652
16th to endNight
18%7%38%31%4
672
April1st to 15thNight
15%9%39%31%4
629
16th to endNight
18%5%39%28%7%
624
May1st to 15thNight
17%5%36%34%5%
630
16th to endNight
11%334%37%13%
659
June1st to 15thNight
5%22%50%20%
630
16th to endNight
6%118%48%23%1
609
July1st to 15thNight
5%9%47%32%3
555
16th to endNight
6%5%45%37%4
612
August1st to 15thNight
1448%39%5%
575
16th to endNight
8%441%42%4
621
September1st to 15thNight
11%434%43%5%
585
16th to endNight
12%10%29%42%4
582
October1st to 15thNight
9%111%39%33%4
585
16th to endNight
13%318%37%24%3
831
November1st to 15thNight
14%421%37%20%1
831
16th to endNight
16%6%20%35%18%2
1050
December1st to 15thNight
23%7%23%31%14%
1050
16th to endNight
25%6%24%32%10%
1120
Page generated at 2019-06-24 19:41:29. Version ac04

Copyright 2019 A. Danko


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