Bowie
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bowie clear sky chart from 2005-11-05 to 2017-08-12.

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
36%
15090
21%
46524
10%
15050
47%
15050
24%
29202

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
22%
717
22%
2437
8%
716
39%
716
19%
1505
January16th to endNight
19%
768
23%
2496
6%
768
39%
768
20%
1553
February1st to 15thNight
21%
704
20%
2287
6%
701
38%
701
20%
1403
February16th to endNight
17%
631
25%
1901
6%
631
39%
631
22%
1169
March1st to 15thNight
26%
720
22%
2022
9%
720
40%
720
25%
1291
March16th to endNight
22%
768
20%
2076
7%
768
33%
768
25%
1399
April1st to 15thNight
24%
718
20%
1796
4%
718
34%
718
27%
1190
April16th to endNight
38%
720
20%
1800
7%
720
44%
720
30%
1198
May1st to 15thNight
33%
562
17%
1642
7%
562
40%
562
22%
1111
May16th to endNight
52%
374
17%
1497
15%
374
59%
374
23%
876
June1st to 15thNight
54%
360
19%
1440
20%
360
62%
360
24%
837
June16th to endNight
56%
360
16%
1440
17%
360
62%
360
24%
837
July1st to 15thNight
53%
340
13%
1360
15%
340
56%
340
19%
849
July16th to endNight
67%
524
16%
1555
13%
491
73%
491
33%
900
August1st to 15thNight
63%
535
17%
1583
13%
532
64%
532
31%
999
August16th to endNight
60%
700
17%
1750
10%
700
61%
700
32%
1193
September1st to 15thNight
58%
660
25%
1650
14%
660
62%
660
32%
1109
September16th to endNight
50%
657
20%
1801
16%
657
54%
657
28%
1198
October1st to 15thNight
43%
660
24%
1980
19%
660
51%
660
26%
1266
October16th to endNight
35%
704
28%
2112
16%
704
51%
704
30%
1238
November1st to 15thNight
34%
700
24%
2241
12%
700
50%
700
26%
1339
November16th to endNight
31%
720
21%
2450
11%
720
45%
720
22%
1462
December1st to 15thNight
26%
720
18%
2520
6%
720
42%
720
18%
1586
December16th to endNight
20%
768
22%
2688
8%
768
38%
768
17%
1694

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%2442445%7%42%
47444
Night
14%5%2442445%7%43%
46706
Cloud CoverDay
14%5%2443445%7%42%
47454
Night
14%5%2442445%7%43%
46710
TransparencyDay
39%6%12%22%15%2
47144
Night
38%5%11%22%17%3
46524
SeeingDay
17%9%26%25%15%5%
5562
Night
17%11%29%27%12%1
15094

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
16%5%35%42435%6%42%
1498
16th to endDay
14%6%25%5%24347%42%
1728
February1st to 15thDay
14%7%235%35%36%5%42%
1575
16th to endDay
14%8%36%425%345%42%
1572
March1st to 15thDay
15%6%35%424346%45%
1924
16th to endDay
17%6%25%424435%42%
2148
April1st to 15thDay
13%5%34424446%46%
2152
16th to endDay
16%5%24424435%45%
2160
May1st to 15thDay
17%425%4345%5%8%37%
2319
16th to endDay
14%4145%35%6%6%8%38%
2618
June1st to 15thDay
11%424426%6%6%9%41%
2520
16th to endDay
10%3245%36%5%6%10%41%
2520
July1st to 15thDay
9%425%5%36%6%7%10%39%
2520
16th to endDay
6%3236%46%6%9%12%37%
2503
August1st to 15thDay
9%5%26%5%45%6%7%9%36%
2269
16th to endDay
11%4246%25%6%6%9%41%
2100
September1st to 15thDay
12%4245%3445%8%45%
1980
16th to endDay
15%6%245%25%447%39%
1826
October1st to 15thDay
18%41332246%5%46%
1650
16th to endDay
15%5%24422345%49%
1760
November1st to 15thDay
15%5%2332345%6%47%
1617
16th to endDay
15%5%25%423436%45%
1509
December1st to 15thDay
16%41442445%6%44%
1440
16th to endDay
19%5%25%424435%41%
1536
January1st to 15thNight
17%5%25%324446%42%
2437
16th to endNight
17%6%2342435%5%44%
2496
February1st to 15thNight
15%6%2342345%6%44%
2285
16th to endNight
14%7%24323346%46%
1901
March1st to 15thNight
16%5%15%323447%45%
2010
16th to endNight
15%6%35%5%23346%41%
2076
April1st to 15thNight
13%5%344245%5%7%43%
1796
16th to endNight
17%42432445%7%44%
1800
May1st to 15thNight
18%6%25%42445%8%38%
1642
16th to endNight
13%42332447%11%41%
1495
June1st to 15thNight
11%3144245%6%10%44%
1440
16th to endNight
8%325%5%35%5%6%10%42%
1440
July1st to 15thNight
7%5%36%7%45%5%7%10%37%
1440
16th to endNight
6%223336%7%7%12%44%
1662
August1st to 15thNight
8%3245%345%7%9%44%
1594
16th to endNight
10%5%26%435%5%48%43%
1750
September1st to 15thNight
12%4245%25%45%6%46%
1650
16th to endNight
13%6%2443445%8%41%
1801
October1st to 15thNight
18%6%24323346%44%
1980
16th to endNight
14%313324347%51%
2112
November1st to 15thNight
14%5%25%32333451%
2241
16th to endNight
15%42343346%7%44%
2450
December1st to 15thNight
17%5%25%43445%7%39%
2520
16th to endNight
17%5%35%42445%6%41%
2688

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
17%5%3442335%7%42%
1498
16th to endDay
14%6%35%5%24347%42%
1728
February1st to 15thDay
15%7%23435%36%5%42%
1575
16th to endDay
14%8%26%424346%41%
1572
March1st to 15thDay
15%5%35%423436%45%
1935
16th to endDay
17%6%25%424435%42%
2147
April1st to 15thDay
13%5%24424446%46%
2152
16th to endDay
16%5%2343444445%
2160
May1st to 15thDay
17%425%4345%6%7%38%
2319
16th to endDay
14%414435%5%7%8%38%
2618
June1st to 15thDay
11%424425%6%6%9%41%
2520
16th to endDay
10%324436%5%6%10%42%
2520
July1st to 15thDay
9%4245%36%5%8%9%39%
2520
16th to endDay
6%3236%46%6%9%11%38%
2503
August1st to 15thDay
9%6%26%5%35%6%7%8%37%
2269
16th to endDay
11%4245%25%6%7%7%41%
2100
September1st to 15thDay
12%325%5%2446%7%45%
1980
16th to endDay
16%6%15%434447%39%
1826
October1st to 15thDay
18%41332245%5%46%
1650
16th to endDay
15%5%24323345%49%
1760
November1st to 15thDay
15%5%2322345%6%48%
1617
16th to endDay
15%5%24433446%45%
1509
December1st to 15thDay
16%32442445%7%44%
1440
16th to endDay
19%5%25%425%436%41%
1536
January1st to 15thNight
17%5%25%323446%43%
2437
16th to endNight
17%6%2432345%5%44%
2496
February1st to 15thNight
14%6%335%3335%5%44%
2278
16th to endNight
14%7%24423345%46%
1901
March1st to 15thNight
16%5%15%323447%45%
2022
16th to endNight
16%6%35%43335%6%41%
2076
April1st to 15thNight
14%5%244245%47%44%
1796
16th to endNight
17%5%1431445%7%44%
1800
May1st to 15thNight
18%6%25%41445%8%38%
1641
16th to endNight
13%4143235%7%10%41%
1495
June1st to 15thNight
11%3244245%7%9%44%
1440
16th to endNight
9%425%6%35%5%6%10%41%
1440
July1st to 15thNight
7%5%26%6%5%5%5%7%9%37%
1440
16th to endNight
6%323336%7%7%12%43%
1662
August1st to 15thNight
8%325%5%345%6%9%44%
1594
16th to endNight
11%416%5%35%5%48%43%
1750
September1st to 15thNight
12%414435%45%7%45%
1650
16th to endNight
14%5%244245%48%41%
1801
October1st to 15thNight
18%5%24333336%44%
1980
16th to endNight
14%313324346%51%
2112
November1st to 15thNight
14%5%24313335%50%
2241
16th to endNight
15%42343446%6%45%
2450
December1st to 15thNight
17%5%25%43445%7%39%
2520
16th to endNight
17%5%34424446%41%
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
40%5%13%22%12%4
1499
16th to endDay
42%411%24%13%4
1728
February1st to 15thDay
42%5%10%25%13%2
1577
16th to endDay
43%311%24%13%1
1572
March1st to 15thDay
40%5%11%23%15%3
1935
16th to endDay
43%5%9%19%18%2
2148
April1st to 15thDay
38%410%23%17%3
2152
16th to endDay
40%5%9%17%20%6%
2160
May1st to 15thDay
41%8%13%20%14%1
2319
16th to endDay
40%8%14%21%12%1
2622
June1st to 15thDay
35%10%13%25%13%1
2520
16th to endDay
35%9%14%20%18%1
2520
July1st to 15thDay
36%9%15%21%14%2
2371
16th to endDay
33%9%17%22%14%1
2347
August1st to 15thDay
39%8%14%21%15%
2256
16th to endDay
36%8%12%23%15%3
2100
September1st to 15thDay
36%6%14%19%19%3
1980
16th to endDay
42%6%9%20%19%2
1826
October1st to 15thDay
37%5%10%26%16%3
1650
16th to endDay
36%38%27%20%2
1760
November1st to 15thDay
35%5%12%24%18%4
1617
16th to endDay
39%49%26%17%2
1509
December1st to 15thDay
39%5%15%24%12%3
1440
16th to endDay
45%410%24%13%1
1536
January1st to 15thNight
41%410%20%17%4
2437
16th to endNight
40%5%10%25%17%1
2496
February1st to 15thNight
39%411%24%16%3
2287
16th to endNight
39%29%26%18%2
1901
March1st to 15thNight
39%411%26%14%2
2022
16th to endNight
42%411%19%17%3
2076
April1st to 15thNight
38%5%10%20%21%3
1796
16th to endNight
38%6%9%20%18%6%
1800
May1st to 15thNight
44%6%11%21%13%3
1642
16th to endNight
35%9%17%20%14%2
1497
June1st to 15thNight
35%8%12%25%17%1
1440
16th to endNight
36%7%14%21%17%2
1440
July1st to 15thNight
41%8%15%18%11%3
1360
16th to endNight
28%10%16%26%16%1
1555
August1st to 15thNight
34%9%14%21%18%1
1583
16th to endNight
38%7%11%22%16%3
1750
September1st to 15thNight
37%7%10%21%19%4
1650
16th to endNight
39%7%10%18%19%3
1801
October1st to 15thNight
41%49%24%17%3
1980
16th to endNight
32%5%8%27%21%3
2112
November1st to 15thNight
37%39%22%19%7%
2241
16th to endNight
37%5%11%22%18%4
2450
December1st to 15thNight
43%412%22%14%2
2520
16th to endNight
42%5%12%23%13%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
25%22%40%9%1
71
16th to endDay
21%27%35%14%1
96
February1st to 15thDay
26%27%35%7%2
90
16th to endDay
19%19%40%17%1
231
March1st to 15thDay
19%19%31%24%5%
270
16th to endDay
21%14%39%18%33
288
April1st to 15thDay
17%15%34%22%8%1
270
16th to endDay
19%10%31%24%9%4
270
May1st to 15thDay
28%15%27%17%8%3
288
16th to endDay
21%323%27%19%4
331
June1st to 15thDay
13%6%26%28%19%6%
315
16th to endDay
13%5%27%33%16%4
315
July1st to 15thDay
11%121%39%21%3
305
16th to endDay
7%16%37%29%7%
326
August1st to 15thDay
13%117%32%26%8%
297
16th to endDay
10%111%33%27%16%
268
September1st to 15thDay
12%416%28%22%15%
255
16th to endDay
24%322%24%15%10%
254
October1st to 15thDay
23%7%21%23%19%4
255
16th to endDay
16%11%32%26%11%2
272
November1st to 15thDay
19%10%32%19%14%4
242
16th to endDay
20%16%28%21%10%3
129
December1st to 15thDay
16%31%20%18%11%1
60
16th to endDay
35%10%34%15%3
64
January1st to 15thNight
20%17%34%21%5%
720
16th to endNight
20%18%38%20%1
768
February1st to 15thNight
18%19%37%23%1
704
16th to endNight
19%22%36%19%1
631
March1st to 15thNight
19%16%35%25%3
720
16th to endNight
18%14%40%19%5%1
768
April1st to 15thNight
16%18%38%20%5%
718
16th to endNight
19%9%29%31%11%
720
May1st to 15thNight
21%8%31%26%10%
562
16th to endNight
14%5%23%34%21%1
375
June1st to 15thNight
11%325%40%18%1
360
16th to endNight
8%324%46%17%
360
July1st to 15thNight
8%23%39%26%
340
16th to endNight
6%117%40%28%4
524
August1st to 15thNight
11%14%44%26%2
535
16th to endNight
13%214%37%28%4
700
September1st to 15thNight
14%217%34%27%3
660
16th to endNight
17%320%31%24%3
657
October1st to 15thNight
20%8%22%26%19%3
660
16th to endNight
16%13%31%25%12%
704
November1st to 15thNight
16%13%30%24%13%1
700
16th to endNight
17%18%29%24%8%
720
December1st to 15thNight
20%15%33%21%9%
720
16th to endNight
20%17%37%22%3
768
Page generated at 2017-08-13 14:16:41. Version ac04

Copyright 2017 A. Danko


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