Belleview
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Belleview clear sky chart from 2005-11-05 to 2017-04-30.

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
57%
15434
21%
45632
16%
15395
63%
15395
30%
28348

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
43%
718
21%
2327
15%
716
52%
716
26%
1426
January16th to endNight
40%
768
24%
2445
16%
768
50%
768
27%
1472
February1st to 15thNight
42%
701
25%
2106
16%
700
52%
700
32%
1252
February16th to endNight
40%
631
24%
1853
13%
631
51%
631
30%
1142
March1st to 15thNight
47%
720
29%
1980
16%
720
58%
720
40%
1130
March16th to endNight
53%
768
26%
2112
18%
768
59%
768
40%
1208
April1st to 15thNight
52%
718
25%
1976
17%
718
59%
718
42%
1131
April16th to endNight
58%
705
27%
1831
17%
705
64%
705
43%
1065
May1st to 15thNight
70%
494
26%
1484
20%
494
75%
494
42%
816
May16th to endNight
74%
513
22%
1538
18%
513
76%
513
37%
912
June1st to 15thNight
70%
495
14%
1485
12%
495
71%
495
26%
999
June16th to endNight
73%
495
8%
1485
8%
495
73%
495
24%
1032
July1st to 15thNight
71%
465
9%
1395
9%
465
71%
465
21%
999
July16th to endNight
78%
522
7%
1469
7%
489
79%
489
22%
1040
August1st to 15thNight
77%
494
7%
1474
7%
491
77%
491
24%
1035
August16th to endNight
67%
638
11%
1861
11%
638
67%
638
20%
1333
September1st to 15thNight
68%
660
9%
1815
8%
660
68%
660
21%
1288
September16th to endNight
59%
657
13%
1815
12%
657
60%
657
19%
1339
October1st to 15thNight
66%
660
26%
1867
25%
660
68%
660
33%
1134
October16th to endNight
60%
704
28%
2112
26%
704
66%
704
33%
1245
November1st to 15thNight
58%
700
29%
2101
24%
700
65%
700
39%
1163
November16th to endNight
48%
720
28%
2265
20%
720
58%
720
32%
1308
December1st to 15thNight
49%
720
28%
2340
25%
720
57%
720
30%
1388
December16th to endNight
52%
768
23%
2496
21%
768
58%
768
29%
1491

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
8%5%26%6%46%6%6%8%38%
46084
Night
8%425%5%35%5%6%9%45%
45838
TransparencyDay
40%8%13%16%13%6%
45785
Night
34%8%15%19%15%6%
45641
SeeingDay
9%314%21%25%24%
5182
Night
10%319%32%26%7%
15442

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
12%6%345%335%5%7%41%
1611
16th to endDay
10%5%35%4245%5%7%45%
1779
February1st to 15thDay
13%5%34425%35%6%45%
1750
16th to endDay
10%5%34434446%48%
1619
March1st to 15thDay
7%3144335%5%7%51%
1980
16th to endDay
7%5%25%5%3445%6%49%
2111
April1st to 15thDay
6%3145%4445%9%48%
1972
16th to endDay
6%3135%35%5%6%9%49%
2117
May1st to 15thDay
6%2145%36%6%5%9%48%
2136
16th to endDay
7%325%6%5%6%6%7%10%38%
2223
June1st to 15thDay
8%426%8%6%9%7%8%8%29%
2145
16th to endDay
8%5%37%9%48%9%8%9%25%
2145
July1st to 15thDay
10%7%47%9%5%9%8%7%8%22%
2145
16th to endDay
7%7%49%10%5%9%7%8%9%20%
2283
August1st to 15thDay
8%6%38%10%6%9%8%8%12%18%
2144
16th to endDay
10%7%38%8%6%7%7%8%10%21%
1974
September1st to 15thDay
8%5%38%9%5%8%7%7%10%25%
1815
16th to endDay
11%8%47%9%5%7%6%7%6%24%
1815
October1st to 15thDay
9%5%27%6%45%5%48%39%
1761
16th to endDay
9%5%145%34447%48%
1760
November1st to 15thDay
7%5%233245%5%7%52%
1757
16th to endDay
8%426%434446%49%
1694
December1st to 15thDay
10%7%35%42446%8%43%
1620
16th to endDay
8%426%425%5%6%9%44%
1728
January1st to 15thNight
11%6%35%42445%9%41%
2327
16th to endNight
14%425%32446%8%44%
2445
February1st to 15thNight
11%5%24423345%51%
2103
16th to endNight
9%5%25%43446%7%46%
1853
March1st to 15thNight
6%32432445%6%55%
1980
16th to endNight
7%31442435%7%55%
2112
April1st to 15thNight
7%41232335%9%55%
1976
16th to endNight
5%413424348%56%
1831
May1st to 15thNight
5%212325%45%9%55%
1484
16th to endNight
5%314425%5%6%8%51%
1538
June1st to 15thNight
8%425%5%37%6%8%10%38%
1485
16th to endNight
6%5%35%5%46%6%9%12%33%
1485
July1st to 15thNight
7%427%7%46%6%8%12%32%
1485
16th to endNight
4326%6%49%8%8%11%33%
1577
August1st to 15thNight
5%317%6%5%7%7%9%13%31%
1485
16th to endNight
9%435%7%45%6%8%11%33%
1861
September1st to 15thNight
7%6%246%46%6%8%12%33%
1815
16th to endNight
9%7%37%6%47%6%7%10%28%
1815
October1st to 15thNight
6%5%25%5%245%5%7%49%
1867
16th to endNight
8%5%25%434346%51%
2112
November1st to 15thNight
5%42432445%7%53%
2101
16th to endNight
7%4245%345%5%7%49%
2265
December1st to 15thNight
10%43442435%8%47%
2340
16th to endNight
8%5%35%435%5%5%8%44%
2496

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%9%18%17%8%
1612
16th to endDay
36%5%8%17%21%10%
1779
February1st to 15thDay
38%5%6%13%21%14%
1752
16th to endDay
35%5%9%16%21%12%
1619
March1st to 15thDay
30%5%10%22%21%9%
1980
16th to endDay
35%5%11%19%18%9%
2112
April1st to 15thDay
30%6%13%18%22%8%
1972
16th to endDay
28%7%13%20%20%8%
2117
May1st to 15thDay
30%8%11%23%17%7%
2136
16th to endDay
37%9%16%19%14%2
2227
June1st to 15thDay
46%12%16%19%5%
2145
16th to endDay
48%12%20%14%3
2145
July1st to 15thDay
54%12%20%11%1
2006
16th to endDay
52%13%20%11%1
2128
August1st to 15thDay
52%14%22%8%1
2131
16th to endDay
52%14%17%13%1
1974
September1st to 15thDay
50%14%18%10%5%
1815
16th to endDay
53%10%13%12%6%3
1815
October1st to 15thDay
42%7%7%16%14%11%
1761
16th to endDay
35%47%14%24%12%
1760
November1st to 15thDay
30%410%21%20%11%
1757
16th to endDay
35%5%8%17%20%11%
1694
December1st to 15thDay
37%6%11%21%17%6%
1620
16th to endDay
34%6%13%21%14%9%
1728
January1st to 15thNight
39%410%20%16%8%
2327
16th to endNight
36%5%9%16%22%9%
2445
February1st to 15thNight
34%39%15%19%16%
2112
16th to endNight
35%5%11%15%21%9%
1853
March1st to 15thNight
27%5%12%25%20%9%
1980
16th to endNight
28%412%23%20%10%
2112
April1st to 15thNight
25%6%12%25%21%7%
1976
16th to endNight
27%5%12%25%21%7%
1831
May1st to 15thNight
24%6%19%26%16%6%
1485
16th to endNight
28%8%17%24%19%1
1540
June1st to 15thNight
36%13%21%23%5%
1485
16th to endNight
39%12%24%18%4
1485
July1st to 15thNight
41%14%26%13%2
1395
16th to endNight
37%17%29%12%3
1469
August1st to 15thNight
37%15%33%12%
1474
16th to endNight
40%15%23%17%2
1861
September1st to 15thNight
39%16%23%14%5%
1815
16th to endNight
46%12%16%16%6%1
1815
October1st to 15thNight
32%7%12%20%18%9%
1867
16th to endNight
32%5%9%14%26%11%
2112
November1st to 15thNight
28%410%24%21%9%
2101
16th to endNight
32%5%10%19%18%14%
2265
December1st to 15thNight
35%5%10%26%15%6%
2340
16th to endNight
35%5%13%21%13%9%
2496

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
14%8%34%23%11%7%
90
16th to endDay
12%19%35%18%11%2
96
February1st to 15thDay
7%23%25%20%18%4
90
16th to endDay
13%9%33%30%13%
120
March1st to 15thDay
8%6%32%33%17%1
270
16th to endDay
10%5%27%24%27%4
288
April1st to 15thDay
8%6%22%32%23%6%
270
16th to endDay
5%318%26%28%17%
266
May1st to 15thDay
6%211%27%28%23%
228
16th to endDay
7%420%35%31%
267
June1st to 15thDay
9%16%14%31%36%
255
16th to endDay
41411%25%53%
255
July1st to 15thDay
7%118%23%57%
245
16th to endDay
10%118%25%51%
270
August1st to 15thDay
10%1411%20%52%
253
16th to endDay
11%1410%21%50%
268
September1st to 15thDay
10%17%12%28%40%
255
16th to endDay
14%5%12%34%32%
254
October1st to 15thDay
12%19%32%31%12%
255
16th to endDay
10%220%28%29%8%
272
November1st to 15thDay
7%218%33%29%8%
265
16th to endDay
8%132%30%22%4
164
December1st to 15thDay
7%11%40%26%14%
90
16th to endDay
9%319%40%22%4
96
January1st to 15thNight
14%7%29%31%15%
720
16th to endNight
17%7%31%33%10%
768
February1st to 15thNight
13%6%31%36%10%1
704
16th to endNight
12%8%32%39%7%
631
March1st to 15thNight
8%7%32%38%11%
720
16th to endNight
9%5%29%38%15%1
768
April1st to 15thNight
8%329%41%15%1
718
16th to endNight
7%325%43%19%
705
May1st to 15thNight
7%115%48%24%2
495
16th to endNight
8%9%35%39%6%
515
June1st to 15thNight
10%7%29%39%12%
495
16th to endNight
9%1218%43%25%
495
July1st to 15thNight
8%1213%46%27%
465
16th to endNight
41213%56%22%
522
August1st to 15thNight
6%313%51%25%
494
16th to endNight
11%15%17%40%24%
638
September1st to 15thNight
11%16%23%39%17%
660
16th to endNight
13%29%26%38%9%
657
October1st to 15thNight
10%211%38%34%4
660
16th to endNight
10%318%36%28%3
704
November1st to 15thNight
8%322%39%23%3
700
16th to endNight
9%331%36%17%1
720
December1st to 15thNight
11%5%26%36%19%
720
16th to endNight
10%6%25%36%21%1
768
Page generated at 2017-04-30 20:40:12. Version ac04

Copyright 2017 A. Danko


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