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 2017-09-16.

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%
15249
28%
46843
20%
15214
63%
15214
37%
25378

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%
717
20%
2506
15%
716
53%
716
27%
1418
January16th to endNight
39%
768
25%
2502
15%
768
53%
768
24%
1512
February1st to 15thNight
42%
700
24%
2212
16%
696
54%
696
26%
1354
February16th to endNight
42%
632
24%
1895
17%
632
52%
632
26%
1192
March1st to 15thNight
40%
720
17%
2112
12%
720
48%
720
26%
1366
March16th to endNight
39%
768
19%
2022
10%
768
46%
768
27%
1338
April1st to 15thNight
42%
719
19%
1799
8%
719
48%
719
27%
1230
April16th to endNight
46%
720
22%
1800
9%
720
52%
720
36%
1104
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
71%
656
42%
1775
32%
656
78%
656
64%
831
October1st to 15thNight
56%
660
31%
1961
24%
660
67%
660
43%
1013
October16th to endNight
61%
704
34%
2125
29%
704
70%
704
45%
1056
November1st to 15thNight
60%
700
30%
2275
27%
700
68%
700
38%
1187
November16th to endNight
44%
720
29%
2358
21%
720
56%
720
32%
1293
December1st to 15thNight
42%
720
22%
2520
13%
720
55%
720
23%
1525
December16th to endNight
36%
768
23%
2688
14%
768
49%
768
18%
1708

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%
47898
Night
6%7%23213346%58%
47032
TransparencyDay
27%49%19%23%15%
47576
Night
27%48%20%24%14%
46854
SeeingDay
16%20%36%18%6%2
5803
Night
12%8%19%31%22%4
15258

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%23313347%49%
1432
16th to endDay
9%15%5%4223237%44%
1721
February1st to 15thDay
9%12%34323346%46%
1640
16th to endDay
10%15%6%5%323245%40%
1579
March1st to 15thDay
8%16%6%4334447%36%
1847
16th to endDay
8%15%4442445%6%38%
2202
April1st to 15thDay
9%14%5%432335%6%41%
2149
16th to endDay
10%9%22212346%53%
2160
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
42221223472%
1856
October1st to 15thDay
7%5%12213346%60%
1667
16th to endDay
7%5%2223235%62%
1746
November1st to 15thDay
6%6%12324446%56%
1584
16th to endDay
7%8%33324345%53%
1599
December1st to 15thDay
12%8%35%314447%44%
1440
16th to endDay
11%12%45%32335%6%41%
1536
January1st to 15thNight
7%9%23323447%49%
2506
16th to endNight
7%12%3432335%6%47%
2502
February1st to 15thNight
9%11%2433335%8%43%
2211
16th to endNight
7%14%45%31345%6%44%
1895
March1st to 15thNight
7%13%5%5%213346%44%
2112
16th to endNight
7%13%33413447%45%
2022
April1st to 15thNight
7%12%4432435%8%42%
1799
16th to endNight
6%8%23312346%56%
1800
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
211311135%76%
1775
October1st to 15thNight
5%43312235%65%
1961
16th to endNight
6%412213337%64%
2125
November1st to 15thNight
6%5%12213448%58%
2275
16th to endNight
6%8%23313337%55%
2358
December1st to 15thNight
12%9%233245%5%6%45%
2520
16th to endNight
11%13%45%322447%40%
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
34%5%11%20%20%7%
1432
16th to endDay
42%47%16%16%11%
1721
February1st to 15thDay
38%310%20%18%8%
1640
16th to endDay
47%47%22%15%2
1579
March1st to 15thDay
47%5%9%14%14%6%
1847
16th to endDay
45%6%14%18%12%2
2202
April1st to 15thDay
43%5%12%19%15%3
2149
16th to endDay
33%5%14%24%17%4
2160
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%26%32%16%
1856
October1st to 15thDay
23%48%23%26%13%
1667
16th to endDay
25%38%23%28%11%
1746
November1st to 15thDay
28%5%12%24%21%8%
1584
16th to endDay
33%39%19%28%5%
1599
December1st to 15thDay
40%5%9%21%18%5%
1440
16th to endDay
44%5%9%14%17%8%
1536
January1st to 15thNight
33%5%10%20%20%9%
2506
16th to endNight
37%47%15%18%15%
2502
February1st to 15thNight
37%5%9%22%15%10%
2222
16th to endNight
38%5%10%22%18%4
1895
March1st to 15thNight
40%5%10%16%18%7%
2112
16th to endNight
37%7%12%20%16%4
2022
April1st to 15thNight
39%7%12%22%14%3
1799
16th to endNight
29%6%13%27%19%3
1800
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%25%28%33%17%
1775
October1st to 15thNight
22%46%27%28%11%
1961
16th to endNight
20%49%21%32%11%
2125
November1st to 15thNight
24%5%9%25%23%11%
2275
16th to endNight
29%47%22%27%8%
2358
December1st to 15thNight
37%7%9%18%19%6%
2520
16th to endNight
44%48%13%19%9%
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
46%11%28%5%5%3
60
16th to endDay
26%19%25%18%8%2
249
February1st to 15thDay
24%21%25%17%10%
247
16th to endDay
27%23%27%18%3
238
March1st to 15thDay
28%27%20%15%7%1
270
16th to endDay
25%28%30%11%4
288
April1st to 15thDay
30%24%28%11%5%
269
16th to endDay
25%29%26%15%2
270
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
10%14%37%30%5%1
256
October1st to 15thDay
11%22%36%22%32
255
16th to endDay
19%19%30%24%5%
258
November1st to 15thDay
11%13%16%24%27%6%
90
16th to endDay
16%28%25%20%9%
87
December1st to 15thDay
30%25%28%10%5%1
60
16th to endDay
23%9%28%20%15%3
64
January1st to 15thNight
16%11%24%25%16%6%
720
16th to endNight
16%14%25%24%14%3
768
February1st to 15thNight
18%11%22%27%16%3
704
16th to endNight
21%12%20%25%16%3
632
March1st to 15thNight
20%10%24%25%16%2
720
16th to endNight
17%14%25%25%15%1
768
April1st to 15thNight
15%12%23%31%13%2
719
16th to endNight
13%11%24%27%19%3
720
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
3318%34%31%8%
656
October1st to 15thNight
9%9%20%29%25%5%
660
16th to endNight
11%8%15%31%24%8%
704
November1st to 15thNight
9%8%19%35%22%5%
700
16th to endNight
13%13%24%25%18%4
720
December1st to 15thNight
20%8%24%28%12%5%
720
16th to endNight
24%15%19%27%9%2
768
Page generated at 2017-09-16 14:07:01. Version ac04

Copyright 2017 A. Danko


Bear Valley Clear Sky Chart | Charts Home