Bear Valley
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bear Valley clear sky chart from 2005-11-05 to 2018-04-23.

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
55%
16121
28%
49520
21%
16086
63%
16086
37%
26846

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%
777
21%
2716
16%
776
53%
776
26%
1553
January16th to endNight
40%
832
24%
2710
15%
832
53%
832
24%
1640
February1st to 15thNight
44%
760
26%
2401
17%
756
57%
756
27%
1433
February16th to endNight
43%
684
24%
2051
18%
684
53%
684
27%
1280
March1st to 15thNight
39%
780
17%
2288
12%
780
47%
780
25%
1502
March16th to endNight
38%
832
19%
2191
9%
832
46%
832
26%
1452
April1st to 15thNight
42%
779
20%
1949
8%
779
48%
779
28%
1329
April16th to endNight
46%
744
23%
1860
9%
744
52%
744
37%
1137
May1st to 15thNight
55%
590
26%
1670
15%
590
61%
590
45%
856
May16th to endNight
60%
374
24%
1496
24%
374
65%
374
35%
717
June1st to 15thNight
64%
360
27%
1440
27%
360
74%
360
40%
631
June16th to endNight
77%
360
36%
1440
42%
360
85%
360
63%
492
July1st to 15thNight
87%
340
33%
1360
43%
340
90%
340
65%
457
July16th to endNight
84%
445
37%
1480
38%
418
86%
418
59%
585
August1st to 15thNight
81%
624
35%
1697
24%
621
82%
621
68%
783
August16th to endNight
81%
764
43%
1910
26%
764
83%
764
75%
888
September1st to 15thNight
80%
720
41%
1800
26%
720
85%
720
75%
842
September16th to endNight
69%
716
44%
1937
32%
716
78%
716
64%
910
October1st to 15thNight
57%
720
30%
2139
24%
720
68%
720
45%
1075
October16th to endNight
63%
768
37%
2318
33%
768
72%
768
47%
1132
November1st to 15thNight
58%
760
29%
2470
26%
760
67%
760
37%
1308
November16th to endNight
45%
780
29%
2555
21%
780
57%
780
31%
1411
December1st to 15thNight
43%
780
23%
2730
15%
780
56%
780
25%
1596
December16th to endNight
37%
832
24%
2912
15%
832
50%
832
18%
1837

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
6%7%23213345%58%
49996
Night
6%7%23213346%58%
49709
TransparencyDay
28%49%19%23%15%
49674
Night
27%48%20%24%14%
49531
SeeingDay
16%20%35%18%7%2
6518
Night
12%8%19%32%22%4
16130

By Month

Percentage Cloud Cover SW (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
9%10%2331335%7%48%
1552
16th to endDay
9%15%5%3223237%44%
1865
February1st to 15thDay
8%11%33313346%48%
1781
16th to endDay
9%15%6%5%323235%41%
1709
March1st to 15thDay
8%17%6%5%334447%35%
2001
16th to endDay
8%15%4442345%6%38%
2385
April1st to 15thDay
9%13%4432345%6%41%
2329
16th to endDay
10%9%32212346%53%
2214
May1st to 15thDay
7%7%13212348%58%
2274
16th to endDay
10%9%2431345%6%48%
2615
June1st to 15thDay
7%5%13223345%60%
2520
16th to endDay
31111222478%
2520
July1st to 15thDay
11111224478%
2520
16th to endDay
221211222377%
2586
August1st to 15thDay
11121223377%
2253
16th to endDay
11221222280%
2292
September1st to 15thDay
31111222476%
2160
16th to endDay
43221223472%
2022
October1st to 15thDay
7%5%12213345%62%
1818
16th to endDay
7%42223235%63%
1905
November1st to 15thDay
7%6%12324446%55%
1719
16th to endDay
8%7%33324346%52%
1732
December1st to 15thDay
11%7%34314347%47%
1560
16th to endDay
10%12%3432445%6%41%
1664
January1st to 15thNight
8%9%2332345%7%48%
2716
16th to endNight
7%11%3432335%6%46%
2710
February1st to 15thNight
8%10%2432335%8%46%
2400
16th to endNight
6%13%45%31345%6%45%
2051
March1st to 15thNight
8%14%5%5%213446%42%
2288
16th to endNight
7%13%33413447%45%
2191
April1st to 15thNight
7%11%4432435%8%42%
1949
16th to endNight
6%8%23312346%56%
1860
May1st to 15thNight
4412213347%63%
1670
16th to endNight
48%3232235%7%57%
1496
June1st to 15thNight
4412212435%67%
1440
16th to endNight
21111111481%
1440
July1st to 15thNight
11121112282%
1440
16th to endNight
221221222377%
1581
August1st to 15thNight
211221223377%
1706
16th to endNight
1112112482%
1910
September1st to 15thNight
1111112482%
1800
16th to endNight
22121112476%
1937
October1st to 15thNight
5%43212235%67%
2139
16th to endNight
5%42212336%66%
2318
November1st to 15thNight
7%6%12213448%57%
2470
16th to endNight
7%7%22314337%54%
2555
December1st to 15thNight
11%8%23314446%47%
2730
16th to endNight
10%12%45%323447%41%
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
36%5%11%20%19%6%
1552
16th to endDay
42%48%16%16%11%
1865
February1st to 15thDay
36%310%20%18%8%
1781
16th to endDay
46%47%21%16%2
1709
March1st to 15thDay
49%5%9%15%14%6%
2001
16th to endDay
45%6%14%19%11%2
2385
April1st to 15thDay
43%5%12%19%15%2
2329
16th to endDay
32%5%14%24%17%4
2214
May1st to 15thDay
24%414%30%21%2
2274
16th to endDay
35%6%10%25%17%4
2619
June1st to 15thDay
26%5%10%22%22%12%
2520
16th to endDay
11%2417%39%23%
2520
July1st to 15thDay
9%3411%28%42%
2371
16th to endDay
12%36%12%23%41%
2425
August1st to 15thDay
11%16%12%29%38%
2237
16th to endDay
11%1412%41%28%
2292
September1st to 15thDay
12%26%14%36%26%
2160
16th to endDay
16%26%27%32%14%
2022
October1st to 15thDay
22%37%21%26%17%
1818
16th to endDay
23%38%22%28%14%
1905
November1st to 15thDay
29%5%11%23%21%8%
1719
16th to endDay
33%310%19%26%5%
1732
December1st to 15thDay
37%5%8%20%18%9%
1560
16th to endDay
43%5%9%14%17%9%
1664
January1st to 15thNight
34%410%21%19%8%
2716
16th to endNight
38%5%8%15%18%14%
2710
February1st to 15thNight
35%5%8%22%17%10%
2411
16th to endNight
38%5%10%22%18%3
2051
March1st to 15thNight
42%5%10%16%18%7%
2288
16th to endNight
38%7%11%21%16%4
2191
April1st to 15thNight
39%7%11%22%15%3
1949
16th to endNight
29%6%13%27%19%3
1860
May1st to 15thNight
19%412%31%25%5%
1671
16th to endNight
25%414%28%20%5%
1496
June1st to 15thNight
19%6%10%21%28%13%
1440
16th to endNight
10%1221%35%27%
1440
July1st to 15thNight
9%2410%30%43%
1360
16th to endNight
13%1412%25%42%
1480
August1st to 15thNight
12%1414%28%37%
1697
16th to endNight
8%1215%40%30%
1910
September1st to 15thNight
8%26%13%41%28%
1800
16th to endNight
12%2428%34%16%
1937
October1st to 15thNight
20%46%25%27%16%
2139
16th to endNight
19%48%20%32%15%
2318
November1st to 15thNight
26%5%8%24%24%11%
2470
16th to endNight
30%47%22%26%8%
2555
December1st to 15thNight
35%6%8%18%19%11%
2730
16th to endNight
43%47%13%20%9%
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
38%11%26%13%6%3
90
16th to endDay
24%18%25%20%9%1
297
February1st to 15thDay
21%20%26%18%11%1
298
16th to endDay
25%24%28%17%3
290
March1st to 15thDay
28%26%20%16%6%1
330
16th to endDay
25%26%30%13%4
352
April1st to 15thDay
28%23%30%11%5%
329
16th to endDay
23%28%26%16%3
288
May1st to 15thDay
18%25%34%14%7%
288
16th to endDay
22%20%26%20%6%3
330
June1st to 15thDay
16%23%39%14%41
315
16th to endDay
6%15%47%19%6%4
315
July1st to 15thDay
315%52%17%8%2
305
16th to endDay
215%51%19%7%3
327
August1st to 15thDay
222%47%16%6%3
315
16th to endDay
310%53%16%10%5%
332
September1st to 15thDay
5%15%45%24%7%2
315
16th to endDay
11%15%37%28%5%1
315
October1st to 15thDay
9%22%36%23%5%2
315
16th to endDay
15%17%26%25%11%2
321
November1st to 15thDay
19%11%21%21%20%5%
135
16th to endDay
16%22%23%23%11%1
130
December1st to 15thDay
21%21%31%8%10%7%
90
16th to endDay
17%14%22%23%18%2
96
January1st to 15thNight
17%10%23%26%16%6%
780
16th to endNight
16%13%25%26%14%3
832
February1st to 15thNight
16%11%22%28%17%3
764
16th to endNight
19%12%20%27%16%3
684
March1st to 15thNight
21%10%23%26%16%2
780
16th to endNight
17%14%25%25%15%1
832
April1st to 15thNight
16%11%24%32%12%2
779
16th to endNight
13%11%24%27%19%3
744
May1st to 15thNight
8%10%21%35%20%3
591
16th to endNight
9%6%17%30%33%3
375
June1st to 15thNight
8%419%35%30%1
360
16th to endNight
2115%49%28%2
360
July1st to 15thNight
15%46%42%2
340
16th to endNight
37%33%47%6%
445
August1st to 15thNight
211%45%35%3
624
16th to endNight
1112%42%37%4
764
September1st to 15thNight
2113%39%36%6%
720
16th to endNight
3418%34%31%7%
716
October1st to 15thNight
8%8%20%31%24%5%
720
16th to endNight
10%8%14%30%26%8%
768
November1st to 15thNight
11%8%18%34%20%5%
760
16th to endNight
14%12%23%27%17%4
780
December1st to 15thNight
19%9%23%28%14%4
780
16th to endNight
23%15%19%28%10%2
832
Page generated at 2018-04-24 07:03:00. Version ac04

Copyright 2018 A. Danko


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