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 2017-12-04.

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
58%
16190
21%
47867
16%
16151
63%
16151
30%
29777

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%
708
27%
1839
17%
708
63%
708
43%
1071
May1st to 15thNight
70%
539
25%
1619
19%
539
74%
539
43%
883
May16th to endNight
74%
561
24%
1682
19%
561
75%
561
37%
992
June1st to 15thNight
68%
540
13%
1620
11%
540
68%
540
24%
1120
June16th to endNight
71%
540
8%
1620
8%
540
72%
540
23%
1144
July1st to 15thNight
73%
510
8%
1530
8%
510
73%
510
21%
1090
July16th to endNight
78%
564
6%
1595
6%
531
79%
531
22%
1139
August1st to 15thNight
77%
539
7%
1609
7%
536
77%
536
23%
1137
August16th to endNight
68%
696
11%
2031
11%
696
68%
696
21%
1450
September1st to 15thNight
66%
720
9%
1980
8%
720
66%
720
20%
1420
September16th to endNight
61%
717
14%
1980
14%
717
63%
717
20%
1429
October1st to 15thNight
65%
720
25%
2037
25%
720
67%
720
32%
1246
October16th to endNight
60%
768
30%
2304
28%
768
66%
768
34%
1349
November1st to 15thNight
60%
760
29%
2281
24%
760
67%
760
41%
1244
November16th to endNight
50%
780
29%
2454
21%
780
60%
780
34%
1401
December1st to 15thNight
50%
736
27%
2391
25%
736
57%
736
30%
1410
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%
48614
Night
8%425%5%35%5%6%9%45%
48073
TransparencyDay
40%8%13%16%13%6%
48315
Night
34%8%15%19%15%6%
47876
SeeingDay
9%314%22%25%24%
6035
Night
10%319%32%26%7%
16198

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%
2130
May1st to 15thDay
6%214436%6%5%9%49%
2331
16th to endDay
6%325%6%5%6%6%7%9%39%
2431
June1st to 15thDay
9%5%37%8%6%9%6%8%8%27%
2340
16th to endDay
8%5%37%9%5%8%9%8%9%24%
2340
July1st to 15thDay
9%6%46%9%5%9%8%7%9%22%
2340
16th to endDay
7%7%49%9%5%9%7%8%9%19%
2465
August1st to 15thDay
7%6%38%10%5%9%8%8%12%18%
2339
16th to endDay
9%7%38%8%7%7%7%8%9%21%
2154
September1st to 15thDay
9%5%38%9%5%7%7%7%10%24%
1980
16th to endDay
10%7%37%9%5%7%7%6%6%26%
1980
October1st to 15thDay
9%5%27%6%45%5%48%38%
1921
16th to endDay
9%5%145%34447%49%
1920
November1st to 15thDay
6%5%233245%5%7%53%
1907
16th to endDay
8%425%434446%50%
1835
December1st to 15thDay
9%7%35%42446%8%43%
1651
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%41342435%8%55%
1839
May1st to 15thNight
5%213425%46%9%56%
1619
16th to endNight
5%314425%5%5%8%51%
1682
June1st to 15thNight
9%5%25%6%37%6%8%10%35%
1620
16th to endNight
6%5%36%6%46%6%9%13%31%
1620
July1st to 15thNight
6%326%7%46%7%9%12%33%
1620
16th to endNight
4326%6%49%9%9%12%32%
1703
August1st to 15thNight
5%317%7%5%7%8%9%14%30%
1620
16th to endNight
9%425%6%45%6%8%11%33%
2031
September1st to 15thNight
8%6%247%46%6%8%11%32%
1980
16th to endNight
8%7%37%6%5%7%6%7%10%30%
1980
October1st to 15thNight
7%5%245%345%6%8%48%
2037
16th to endNight
7%5%25%423346%52%
2304
November1st to 15thNight
5%42432445%7%55%
2281
16th to endNight
7%4245%345%5%7%50%
2454
December1st to 15thNight
10%43442435%8%47%
2391
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
29%7%13%20%20%8%
2130
May1st to 15thDay
30%8%11%21%18%9%
2331
16th to endDay
36%9%16%19%14%3
2435
June1st to 15thDay
49%11%15%18%4
2340
16th to endDay
49%12%20%14%3
2340
July1st to 15thDay
52%13%21%11%1
2201
16th to endDay
52%14%20%10%1
2310
August1st to 15thDay
52%14%22%8%1
2326
16th to endDay
53%13%17%13%1
2154
September1st to 15thDay
51%14%18%10%5%
1980
16th to endDay
51%10%13%13%7%2
1980
October1st to 15thDay
43%7%7%16%13%10%
1921
16th to endDay
35%46%14%24%14%
1920
November1st to 15thDay
29%410%22%20%10%
1907
16th to endDay
35%5%8%18%20%11%
1835
December1st to 15thDay
37%6%12%21%16%5%
1651
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%
1839
May1st to 15thNight
24%6%17%25%18%7%
1620
16th to endNight
28%8%16%24%19%2
1684
June1st to 15thNight
39%13%19%22%5%
1620
16th to endNight
40%13%23%17%4
1620
July1st to 15thNight
40%15%27%13%2
1530
16th to endNight
36%18%29%11%3
1595
August1st to 15thNight
37%16%33%12%
1609
16th to endNight
40%15%24%17%2
2031
September1st to 15thNight
40%16%23%14%5%
1980
16th to endNight
44%12%17%17%6%1
1980
October1st to 15thNight
32%8%12%20%17%8%
2037
16th to endNight
32%5%8%15%25%12%
2304
November1st to 15thNight
27%411%25%22%8%
2281
16th to endNight
31%5%9%20%19%12%
2454
December1st to 15thNight
34%5%10%26%15%6%
2391
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%27%28%17%
270
May1st to 15thDay
5%313%29%27%20%
288
16th to endDay
6%16%20%36%28%
331
June1st to 15thDay
12%16%17%28%32%
315
16th to endDay
6%1411%25%50%
315
July1st to 15thDay
6%7%22%60%
305
16th to endDay
11%2211%24%48%
326
August1st to 15thDay
9%313%22%50%
313
16th to endDay
12%410%21%50%
332
September1st to 15thDay
12%17%14%28%35%
315
16th to endDay
13%414%36%31%
314
October1st to 15thDay
11%210%32%30%12%
315
16th to endDay
10%321%30%25%7%
336
November1st to 15thDay
7%118%35%30%7%
325
16th to endDay
8%127%33%23%4
215
December1st to 15thDay
7%10%36%25%19%3
100
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%
708
May1st to 15thNight
7%115%49%24%2
540
16th to endNight
7%10%35%38%7%
563
June1st to 15thNight
11%8%29%37%12%
540
16th to endNight
10%217%42%26%
540
July1st to 15thNight
7%1212%45%30%
510
16th to endNight
41213%54%23%
564
August1st to 15thNight
6%312%51%26%
539
16th to endNight
11%1417%40%24%
696
September1st to 15thNight
11%17%24%38%16%
720
16th to endNight
12%28%26%39%9%
717
October1st to 15thNight
10%211%38%34%4
720
16th to endNight
10%319%36%27%3
768
November1st to 15thNight
7%321%39%25%3
760
16th to endNight
9%330%36%18%1
780
December1st to 15thNight
11%5%26%36%20%
736
16th to endNight
10%6%25%36%21%1
768
Page generated at 2017-12-05 10:19:05. Version ac04

Copyright 2017 A. Danko


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