Bass Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bass Lake clear sky chart from 2005-11-05 to

2017-09-12
.

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
31%
16020
12%
46771
8%
15978
35%
15978
15%
34897

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
10%
900
3%
2506
1%
895
12%
895
4%
2270
January16th to endNight
12%
960
3%
2688
1%
960
14%
960
4%
2434
February1st to 15thNight
16%
770
5%
2250
2%
770
19%
770
6%
1938
February16th to endNight
20%
631
6%
1893
4%
631
23%
631
8%
1597
March1st to 15thNight
27%
720
13%
2160
7%
720
32%
720
15%
1587
March16th to endNight
34%
692
16%
2036
11%
692
39%
692
18%
1430
April1st to 15thNight
26%
539
14%
1797
9%
539
34%
539
16%
1259
April16th to endNight
33%
540
20%
1656
10%
540
43%
540
19%
1099
May1st to 15thNight
37%
540
14%
1614
10%
540
42%
540
18%
1133
May16th to endNight
38%
562
16%
1498
8%
561
45%
561
27%
979
June1st to 15thNight
45%
540
13%
1440
7%
540
49%
540
27%
933
June16th to endNight
50%
540
13%
1440
7%
540
55%
540
30%
905
July1st to 15thNight
61%
510
16%
1360
11%
510
64%
510
38%
788
July16th to endNight
53%
564
16%
1417
10%
531
60%
531
34%
884
August1st to 15thNight
62%
539
23%
1543
18%
536
65%
536
36%
875
August16th to endNight
59%
573
20%
1845
17%
573
64%
573
28%
1101
September1st to 15thNight
54%
569
20%
1806
20%
569
57%
569
28%
1097
September16th to endNight
54%
657
19%
1815
14%
657
58%
657
30%
1159
October1st to 15thNight
40%
660
18%
1865
13%
660
44%
660
23%
1287
October16th to endNight
23%
704
9%
2288
5%
704
29%
704
11%
1754
November1st to 15thNight
25%
700
14%
2276
11%
700
31%
700
13%
1672
November16th to endNight
17%
750
6%
2370
4%
750
19%
750
6%
1992
December1st to 15thNight
9%
900
3%
2520
1%
900
10%
900
4%
2302
December16th to endNight
10%
960
5%
2688
1%
960
14%
960
5%
2422

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%3445%6%35%
47898
Night
15%11%5%7%6%34446%31%
46939
Cloud CoverDay
14%9%46%5%34446%35%
47907
Night
15%11%5%7%6%34345%31%
46944
TransparencyDay
49%6%12%20%9%
47584
Night
54%6%11%17%9%1
46771
SeeingDay
16%14%24%26%14%4
6008
Night
17%21%22%25%11%1
16024

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%17%11%13%11%5%43339%
1432
16th to endDay
13%16%15%14%11%6%5%3327%
1536
February1st to 15thDay
12%15%8%13%13%5%5%335%13%
1610
16th to endDay
13%14%7%12%10%5%6%345%16%
1580
March1st to 15thDay
13%9%5%9%7%346%45%29%
1790
16th to endDay
15%8%46%5%3445%7%33%
2199
April1st to 15thDay
20%10%34423446%32%
2151
16th to endDay
17%8%25%6%245%46%36%
2304
May1st to 15thDay
16%6%25%42435%7%38%
2334
16th to endDay
9%5%2432447%8%46%
2617
June1st to 15thDay
13%5%2443445%8%43%
2520
16th to endDay
9%42442446%9%47%
2520
July1st to 15thDay
6%41432445%8%54%
2520
16th to endDay
8%32342445%8%50%
2655
August1st to 15thDay
6%3134245%6%9%49%
2406
16th to endDay
12%5%1433345%6%50%
2356
September1st to 15thDay
13%5%25%323447%47%
2061
16th to endDay
12%6%25%43445%9%40%
1815
October1st to 15thDay
18%8%35%42445%6%36%
1763
16th to endDay
25%10%37%5%34445%24%
1584
November1st to 15thDay
16%12%47%6%24346%31%
1582
16th to endDay
22%22%7%8%6%2334414%
1587
December1st to 15thDay
18%21%14%15%8%2212210%
1440
16th to endDay
19%23%9%13%9%324228%
1536
January1st to 15thNight
19%19%9%13%10%4222212%
2506
16th to endNight
12%17%11%13%11%5%433410%
2688
February1st to 15thNight
12%15%9%13%11%5%432316%
2248
16th to endNight
15%14%7%11%9%5%5%345%17%
1893
March1st to 15thNight
14%9%5%8%5%24437%33%
2147
16th to endNight
15%8%46%5%3445%7%35%
2036
April1st to 15thNight
20%8%46%43345%7%31%
1797
16th to endNight
18%6%35%424446%40%
1656
May1st to 15thNight
16%6%27%6%35%46%6%35%
1614
16th to endNight
9%5%35%5%3445%10%43%
1496
June1st to 15thNight
11%5%235%245%6%8%43%
1440
16th to endNight
8%5%15%4245%7%11%43%
1440
July1st to 15thNight
6%3134245%5%9%52%
1440
16th to endNight
7%4244245%48%50%
1513
August1st to 15thNight
6%3134235%5%9%53%
1552
16th to endNight
11%424324447%49%
1845
September1st to 15thNight
14%5%14323346%49%
1806
16th to endNight
13%41432445%6%47%
1815
October1st to 15thNight
19%7%24423247%39%
1865
16th to endNight
25%9%37%5%3344428%
2288
November1st to 15thNight
17%14%47%423435%31%
2276
16th to endNight
21%20%7%8%5%3333317%
2370
December1st to 15thNight
21%22%12%12%6%2223210%
2520
16th to endNight
20%23%8%12%6%2332311%
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%17%10%13%10%5%433310%
1432
16th to endDay
13%16%14%14%11%5%5%3237%
1536
February1st to 15thDay
12%15%9%12%13%45%33414%
1610
16th to endDay
13%15%7%12%10%5%7%345%16%
1580
March1st to 15thDay
13%9%5%9%7%35%5%46%29%
1800
16th to endDay
15%7%46%5%3445%7%33%
2198
April1st to 15thDay
21%10%34424445%33%
2151
16th to endDay
18%8%25%5%24446%36%
2304
May1st to 15thDay
17%5%25%42435%7%38%
2334
16th to endDay
10%42442446%9%47%
2617
June1st to 15thDay
13%5%25%42435%7%44%
2520
16th to endDay
10%324425%45%9%47%
2520
July1st to 15thDay
7%31432345%8%54%
2520
16th to endDay
8%32342345%8%51%
2655
August1st to 15thDay
7%3144245%6%9%49%
2406
16th to endDay
13%423422446%50%
2356
September1st to 15thDay
14%5%24333346%47%
2061
16th to endDay
13%6%25%42446%8%40%
1815
October1st to 15thDay
19%8%25%42345%6%36%
1763
16th to endDay
25%10%37%5%345%45%24%
1584
November1st to 15thDay
17%12%46%5%34346%31%
1582
16th to endDay
21%23%6%8%5%2334415%
1587
December1st to 15thDay
18%21%14%15%8%2212210%
1440
16th to endDay
20%23%9%13%8%233339%
1536
January1st to 15thNight
19%19%9%13%10%3322213%
2506
16th to endNight
12%18%11%13%11%5%5%23411%
2688
February1st to 15thNight
12%16%9%13%11%5%433317%
2241
16th to endNight
15%14%7%11%9%45%336%17%
1893
March1st to 15thNight
14%9%5%8%5%23447%33%
2160
16th to endNight
15%7%45%6%3445%6%35%
2036
April1st to 15thNight
20%8%45%42345%6%32%
1797
16th to endNight
18%6%35%424445%40%
1656
May1st to 15thNight
16%5%26%6%45%45%6%35%
1613
16th to endNight
10%5%35%43445%10%43%
1496
June1st to 15thNight
11%5%14425%5%6%7%44%
1440
16th to endNight
9%42442447%10%45%
1440
July1st to 15thNight
7%2134335%5%9%53%
1440
16th to endNight
7%4234245%5%8%51%
1513
August1st to 15thNight
7%31342446%8%53%
1552
16th to endNight
12%4233235%46%50%
1845
September1st to 15thNight
14%5%13323346%50%
1806
16th to endNight
14%413424446%48%
1815
October1st to 15thNight
20%7%24423237%39%
1865
16th to endNight
25%10%27%5%33445%28%
2288
November1st to 15thNight
17%14%36%424345%32%
2276
16th to endNight
21%21%7%8%43333417%
2370
December1st to 15thNight
21%22%13%11%6%2323210%
2520
16th to endNight
20%24%8%12%5%3323311%
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
82%5%46%1
1433
16th to endDay
84%5%5%31
1536
February1st to 15thDay
74%6%7%10%
1612
16th to endDay
72%6%9%8%3
1580
March1st to 15thDay
55%8%13%15%5%
1800
16th to endDay
48%7%14%21%6%1
2199
April1st to 15thDay
51%5%11%19%11%
2151
16th to endDay
48%6%12%17%13%2
2304
May1st to 15thDay
44%6%11%23%11%1
2334
16th to endDay
33%8%15%27%13%1
2621
June1st to 15thDay
38%7%13%25%15%
2520
16th to endDay
32%9%18%24%14%1
2520
July1st to 15thDay
28%6%14%30%18%1
2371
16th to endDay
30%8%14%28%16%2
2488
August1st to 15thDay
29%8%18%30%11%1
2391
16th to endDay
34%7%13%27%15%1
2356
September1st to 15thDay
38%5%14%27%13%1
2061
16th to endDay
41%7%15%25%10%
1815
October1st to 15thDay
47%7%11%23%9%
1763
16th to endDay
61%6%15%12%3
1584
November1st to 15thDay
54%6%11%19%8%
1582
16th to endDay
73%5%11%6%1
1587
December1st to 15thDay
83%35%5%1
1440
16th to endDay
81%5%7%31
1536
January1st to 15thNight
80%45%6%2
2506
16th to endNight
78%6%8%5%1
2688
February1st to 15thNight
73%6%6%11%2
2250
16th to endNight
70%5%9%9%4
1893
March1st to 15thNight
51%7%12%18%8%1
2160
16th to endNight
46%7%12%22%9%1
2036
April1st to 15thNight
51%5%9%20%12%1
1797
16th to endNight
44%5%9%21%14%3
1656
May1st to 15thNight
47%7%11%20%12%1
1614
16th to endNight
36%7%12%25%14%3
1498
June1st to 15thNight
36%7%13%24%16%
1440
16th to endNight
32%7%17%23%15%2
1440
July1st to 15thNight
25%7%13%29%20%3
1360
16th to endNight
30%8%14%27%16%2
1417
August1st to 15thNight
27%6%15%33%15%1
1543
16th to endNight
33%8%12%25%18%2
1845
September1st to 15thNight
35%6%11%26%17%1
1806
16th to endNight
35%7%14%30%10%
1815
October1st to 15thNight
46%5%10%25%11%
1865
16th to endNight
59%6%13%15%5%
2288
November1st to 15thNight
55%6%12%16%9%1
2276
16th to endNight
71%5%12%7%2
2370
December1st to 15thNight
81%5%6%5%1
2520
16th to endNight
78%5%8%5%1
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
18%16%38%23%2
90
16th to endDay
31%432%26%5%1
96
February1st to 15thDay
12%25%46%10%5%
90
16th to endDay
19%20%32%23%21
81
March1st to 15thDay
23%18%32%21%4
90
16th to endDay
23%17%22%26%7%2
288
April1st to 15thDay
26%17%27%21%5%1
270
16th to endDay
21%17%28%21%6%4
270
May1st to 15thDay
18%19%25%26%8%3
291
16th to endDay
13%17%28%26%12%2
517
June1st to 15thDay
14%14%25%30%12%1
495
16th to endDay
12%14%25%29%12%4
495
July1st to 15thDay
10%10%18%33%20%6%
475
16th to endDay
6%13%23%32%18%5%
515
August1st to 15thDay
8%8%17%31%26%8%
379
16th to endDay
19%9%12%27%24%6%
332
September1st to 15thDay
13%7%19%30%22%8%
299
16th to endDay
13%10%17%26%24%6%
254
October1st to 15thDay
18%14%17%27%17%3
219
16th to endDay
28%8%38%21%3
96
November1st to 15thDay
15%12%27%27%13%3
90
16th to endDay
35%16%31%12%4
90
December1st to 15thDay
28%30%26%12%2
90
16th to endDay
32%31%31%5%
96
January1st to 15thNight
22%28%28%16%5%
900
16th to endNight
17%26%31%21%3
960
February1st to 15thNight
16%28%26%23%5%
773
16th to endNight
19%24%26%24%5%
631
March1st to 15thNight
13%24%27%23%10%
720
16th to endNight
16%21%22%28%9%1
692
April1st to 15thNight
19%23%28%23%6%
539
16th to endNight
19%20%23%25%10%1
540
May1st to 15thNight
15%20%20%31%11%
540
16th to endNight
12%19%22%28%16%1
563
June1st to 15thNight
12%17%18%35%14%
540
16th to endNight
9%18%18%32%19%2
540
July1st to 15thNight
7%12%12%35%26%4
510
16th to endNight
7%17%16%31%23%3
564
August1st to 15thNight
8%9%12%38%27%3
539
16th to endNight
12%10%13%32%26%4
573
September1st to 15thNight
14%11%16%31%18%6%
569
16th to endNight
13%12%15%30%23%4
657
October1st to 15thNight
22%12%20%26%15%2
660
16th to endNight
27%18%25%20%7%
704
November1st to 15thNight
22%23%23%21%8%
700
16th to endNight
25%28%23%18%4
750
December1st to 15thNight
29%31%23%12%2
900
16th to endNight
25%28%26%16%2
960
Page generated at 2017-09-13 07:39:14. Version ac04

Copyright 2017 A. Danko


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