Big Sable Point
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Big Sable Point clear sky chart from 2005-11-05 to 2018-01-12.

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
29%
16564
12%
48333
7%
16522
33%
16522
15%
36202

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
7%
956
3%
2662
1%
951
9%
951
4%
2406
January16th to endNight
11%
960
3%
2688
2%
960
12%
960
4%
2437
February1st to 15thNight
15%
778
5%
2258
2%
778
18%
778
7%
1946
February16th to endNight
18%
631
6%
1893
4%
631
20%
631
7%
1597
March1st to 15thNight
26%
720
12%
2160
7%
720
31%
720
15%
1590
March16th to endNight
32%
687
17%
2034
11%
687
38%
687
17%
1426
April1st to 15thNight
25%
539
14%
1797
8%
539
34%
539
15%
1256
April16th to endNight
31%
540
19%
1656
9%
540
40%
540
18%
1111
May1st to 15thNight
33%
540
15%
1602
9%
540
39%
540
18%
1116
May16th to endNight
39%
562
16%
1498
7%
561
47%
561
27%
963
June1st to 15thNight
39%
540
13%
1440
6%
540
44%
540
25%
928
June16th to endNight
49%
540
13%
1440
7%
540
53%
540
28%
922
July1st to 15thNight
60%
510
16%
1360
11%
510
63%
510
37%
805
July16th to endNight
52%
564
16%
1417
10%
531
59%
531
33%
878
August1st to 15thNight
60%
539
22%
1534
18%
536
64%
536
36%
879
August16th to endNight
55%
573
20%
1845
17%
573
61%
573
28%
1096
September1st to 15thNight
53%
579
20%
1839
19%
579
56%
579
28%
1117
September16th to endNight
55%
717
21%
1980
16%
717
58%
717
30%
1248
October1st to 15thNight
37%
720
17%
2040
12%
720
41%
720
22%
1428
October16th to endNight
23%
768
10%
2496
6%
768
29%
768
11%
1909
November1st to 15thNight
23%
760
14%
2471
10%
760
29%
760
12%
1856
November16th to endNight
17%
826
6%
2581
3%
826
20%
826
7%
2152
December1st to 15thNight
8%
975
2%
2730
1%
975
10%
975
4%
2495
December16th to endNight
8%
1040
4%
2912
1%
1040
11%
1040
4%
2641

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
14%9%47%5%34446%34%
49010
Night
16%11%5%8%6%34345%30%
48501
Cloud CoverDay
14%9%47%6%34446%34%
49019
Night
15%12%5%8%6%34345%29%
48506
TransparencyDay
50%5%12%20%9%
48696
Night
56%5%10%17%8%1
48333
SeeingDay
18%14%25%24%13%4
6416
Night
19%21%22%24%11%1
16568

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
17%18%11%13%11%4422310%
1520
16th to endDay
14%17%13%15%12%5%42226%
1536
February1st to 15thDay
13%16%7%12%15%7%423312%
1600
16th to endDay
14%15%9%12%10%36%42416%
1580
March1st to 15thDay
14%8%6%8%7%35%6%5%5%27%
1790
16th to endDay
15%8%46%5%3445%7%35%
2199
April1st to 15thDay
19%10%35%434345%34%
2151
16th to endDay
17%8%35%424446%36%
2304
May1st to 15thDay
17%6%25%5%245%5%6%38%
2346
16th to endDay
9%5%2442445%7%48%
2617
June1st to 15thDay
13%5%25%425%36%8%42%
2520
16th to endDay
9%41442446%8%48%
2520
July1st to 15thDay
7%31432445%8%53%
2520
16th to endDay
8%3243245%6%9%49%
2655
August1st to 15thDay
7%3134245%6%9%50%
2415
16th to endDay
13%5%1432435%6%50%
2355
September1st to 15thDay
14%5%15%423346%47%
2108
16th to endDay
13%6%25%5%345%5%7%42%
1980
October1st to 15thDay
19%8%36%433347%35%
1919
16th to endDay
25%9%39%6%24336%25%
1728
November1st to 15thDay
20%14%46%5%33346%28%
1717
16th to endDay
24%20%6%9%423335%15%
1706
December1st to 15thDay
20%22%14%15%8%122129%
1560
16th to endDay
20%23%10%13%8%333227%
1664
January1st to 15thNight
20%19%8%13%12%3221212%
2662
16th to endNight
15%16%10%14%13%5%42249%
2688
February1st to 15thNight
13%16%9%13%11%5%5%33315%
2256
16th to endNight
16%16%6%13%9%5%433416%
1893
March1st to 15thNight
14%9%5%9%5%35%446%30%
2147
16th to endNight
16%7%37%6%2445%7%33%
2034
April1st to 15thNight
20%10%36%42435%6%32%
1797
16th to endNight
18%7%34424345%40%
1656
May1st to 15thNight
17%6%25%6%345%5%7%34%
1602
16th to endNight
10%5%2433447%8%44%
1496
June1st to 15thNight
12%5%35%42345%9%43%
1440
16th to endNight
9%4244345%7%9%43%
1440
July1st to 15thNight
6%3134345%5%10%51%
1440
16th to endNight
6%5%2443445%7%50%
1513
August1st to 15thNight
5%3145%245%5%9%52%
1543
16th to endNight
12%424422447%48%
1845
September1st to 15thNight
15%5%24314246%48%
1839
16th to endNight
12%4244345%46%46%
1980
October1st to 15thNight
22%7%34422436%38%
2040
16th to endNight
26%11%46%5%2343427%
2496
November1st to 15thNight
19%15%5%6%5%23335%29%
2471
16th to endNight
20%20%5%9%5%23335%17%
2581
December1st to 15thNight
22%22%12%12%7%222229%
2730
16th to endNight
21%24%8%12%7%3322310%
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
16%19%12%13%11%5%42139%
1520
16th to endDay
14%18%13%15%12%5%5%2226%
1536
February1st to 15thDay
13%15%9%13%15%5%433311%
1600
16th to endDay
13%15%9%12%11%5%6%33315%
1580
March1st to 15thDay
13%10%5%9%7%45%5%46%26%
1800
16th to endDay
15%9%37%5%3445%6%33%
2198
April1st to 15thDay
19%10%46%324346%33%
2151
16th to endDay
17%9%36%5%34346%35%
2304
May1st to 15thDay
16%6%35%5%345%46%38%
2346
16th to endDay
9%4243345%5%9%47%
2617
June1st to 15thDay
12%6%25%43445%9%41%
2520
16th to endDay
9%324325%5%6%9%47%
2520
July1st to 15thDay
7%41342445%9%52%
2520
16th to endDay
8%324425%5%6%8%49%
2655
August1st to 15thDay
7%31343446%9%49%
2415
16th to endDay
13%5%24323346%48%
2355
September1st to 15thDay
14%4245%23447%46%
2108
16th to endDay
12%6%2443445%9%40%
1980
October1st to 15thDay
18%10%26%5%23347%34%
1919
16th to endDay
24%11%47%6%34236%24%
1728
November1st to 15thDay
19%13%5%6%5%33447%27%
1717
16th to endDay
22%22%6%10%5%2323415%
1706
December1st to 15thDay
18%22%15%15%7%221129%
1560
16th to endDay
19%22%11%14%8%333237%
1664
January1st to 15thNight
19%18%8%14%13%3221212%
2662
16th to endNight
13%17%9%14%13%5%5%3339%
2688
February1st to 15thNight
13%16%9%13%11%5%433315%
2249
16th to endNight
15%16%6%12%9%45%34416%
1893
March1st to 15thNight
14%9%5%8%6%3445%6%29%
2160
16th to endNight
15%8%37%5%25%45%7%33%
2034
April1st to 15thNight
19%10%5%5%5%23446%32%
1797
16th to endNight
18%7%25%5%33346%39%
1656
May1st to 15thNight
16%6%35%6%35%5%5%7%34%
1601
16th to endNight
10%5%2442447%9%44%
1496
June1st to 15thNight
11%6%35%42345%8%43%
1440
16th to endNight
9%415%4346%6%9%43%
1440
July1st to 15thNight
7%3233245%6%9%51%
1440
16th to endNight
6%5%24425%5%5%8%49%
1513
August1st to 15thNight
5%31443446%10%51%
1543
16th to endNight
12%42442335%7%48%
1845
September1st to 15thNight
14%5%24324336%48%
1839
16th to endNight
12%414435%5%5%6%47%
1980
October1st to 15thNight
21%8%25%413336%38%
2040
16th to endNight
26%11%47%433335%26%
2496
November1st to 15thNight
17%16%5%7%424325%29%
2471
16th to endNight
19%21%6%9%5%3333417%
2581
December1st to 15thNight
20%22%12%13%7%2222210%
2730
16th to endNight
20%24%9%11%8%333339%
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
83%35%5%1
1521
16th to endDay
85%3441
1536
February1st to 15thDay
77%46%10%1
1602
16th to endDay
74%48%8%2
1580
March1st to 15thDay
57%6%13%16%5%
1800
16th to endDay
49%5%15%21%6%1
2199
April1st to 15thDay
52%410%20%11%
2151
16th to endDay
48%5%11%17%13%2
2304
May1st to 15thDay
45%5%11%24%11%1
2346
16th to endDay
33%7%14%28%13%2
2621
June1st to 15thDay
38%6%12%26%14%
2520
16th to endDay
33%6%18%25%14%1
2520
July1st to 15thDay
29%5%13%31%18%1
2371
16th to endDay
31%6%14%28%16%2
2488
August1st to 15thDay
29%7%16%34%11%1
2400
16th to endDay
35%6%12%29%15%1
2355
September1st to 15thDay
38%412%29%13%
2108
16th to endDay
39%7%15%27%10%
1980
October1st to 15thDay
49%5%11%23%10%
1919
16th to endDay
62%5%13%14%3
1728
November1st to 15thDay
57%6%11%17%7%
1717
16th to endDay
73%412%7%2
1706
December1st to 15thDay
84%25%5%1
1560
16th to endDay
83%5%6%31
1664
January1st to 15thNight
81%36%6%2
2662
16th to endNight
79%6%7%5%1
2688
February1st to 15thNight
73%5%6%11%2
2258
16th to endNight
71%5%10%8%3
1893
March1st to 15thNight
53%7%12%17%8%1
2160
16th to endNight
48%6%12%22%8%1
2034
April1st to 15thNight
51%49%20%11%1
1797
16th to endNight
45%5%9%20%14%3
1656
May1st to 15thNight
47%6%11%21%11%1
1602
16th to endNight
35%6%12%26%14%3
1498
June1st to 15thNight
37%6%13%24%16%
1440
16th to endNight
35%7%15%22%16%2
1440
July1st to 15thNight
27%7%11%30%19%3
1360
16th to endNight
30%8%13%28%16%2
1417
August1st to 15thNight
27%6%14%34%15%1
1534
16th to endNight
35%5%11%27%17%1
1845
September1st to 15thNight
36%5%11%26%18%1
1839
16th to endNight
36%6%14%30%11%
1980
October1st to 15thNight
47%5%9%24%12%
2040
16th to endNight
60%5%13%15%4
2496
November1st to 15thNight
59%410%15%7%1
2471
16th to endNight
70%413%8%2
2581
December1st to 15thNight
81%45%5%2
2730
16th to endNight
79%5%8%5%1
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
20%14%34%25%4
123
16th to endDay
32%7%28%27%41
96
February1st to 15thDay
17%26%42%11%2
90
16th to endDay
19%19%38%19%11
81
March1st to 15thDay
28%14%31%20%5%
90
16th to endDay
26%15%23%23%8%2
285
April1st to 15thDay
24%17%28%22%5%1
270
16th to endDay
22%17%27%18%8%4
270
May1st to 15thDay
22%21%25%20%7%2
303
16th to endDay
12%18%31%21%13%3
517
June1st to 15thDay
16%16%28%25%12%2
495
16th to endDay
14%15%27%26%12%4
495
July1st to 15thDay
11%11%21%29%20%6%
475
16th to endDay
8%14%22%30%16%6%
515
August1st to 15thDay
10%7%21%29%24%7%
388
16th to endDay
21%8%13%28%19%6%
332
September1st to 15thDay
15%6%18%28%20%10%
315
16th to endDay
11%8%18%28%26%6%
314
October1st to 15thDay
23%10%27%23%14%2
269
16th to endDay
34%6%36%22%
144
November1st to 15thDay
30%11%26%20%8%2
135
16th to endDay
28%19%32%13%5%
135
December1st to 15thDay
28%22%34%10%3
135
16th to endDay
31%27%31%9%
144
January1st to 15thNight
22%28%27%16%4
956
16th to endNight
18%26%29%19%4
960
February1st to 15thNight
18%26%25%23%4
781
16th to endNight
20%24%24%24%4
631
March1st to 15thNight
15%24%26%23%10%
720
16th to endNight
17%21%21%28%9%1
687
April1st to 15thNight
20%23%25%23%5%
539
16th to endNight
19%21%23%25%9%1
540
May1st to 15thNight
16%21%21%28%11%
540
16th to endNight
11%20%23%26%17%1
563
June1st to 15thNight
12%18%21%34%12%
540
16th to endNight
10%19%15%34%18%2
540
July1st to 15thNight
8%13%13%36%25%3
510
16th to endNight
7%17%16%31%24%3
564
August1st to 15thNight
7%10%12%38%26%4
539
16th to endNight
13%9%14%33%24%4
573
September1st to 15thNight
15%11%16%29%19%8%
579
16th to endNight
11%12%15%29%26%4
717
October1st to 15thNight
24%12%20%26%14%2
720
16th to endNight
31%17%23%20%6%
768
November1st to 15thNight
25%21%23%20%8%
760
16th to endNight
24%27%24%18%4
826
December1st to 15thNight
29%30%23%13%2
975
16th to endNight
27%26%26%16%2
1040
Page generated at 2018-01-12 22:01:36. Version ac04

Copyright 2018 A. Danko


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