Shaver Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Shaver Lake clear sky chart from 2005-11-05 to 2017-10-31.

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
75%
15578
30%
47367
29%
15544
77%
15544
46%
24179

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
67%
716
23%
2506
24%
716
71%
716
36%
1314
January16th to endNight
61%
768
27%
2496
26%
768
67%
768
31%
1455
February1st to 15thNight
63%
699
27%
2150
26%
696
67%
696
33%
1257
February16th to endNight
61%
632
24%
1895
25%
632
64%
632
30%
1176
March1st to 15thNight
65%
720
20%
2142
23%
720
66%
720
34%
1268
March16th to endNight
67%
768
21%
2001
17%
768
69%
768
39%
1197
April1st to 15thNight
67%
719
22%
1799
14%
719
68%
719
39%
1119
April16th to endNight
70%
720
24%
1800
13%
720
71%
720
48%
1028
May1st to 15thNight
74%
605
28%
1685
20%
605
76%
605
52%
848
May16th to endNight
76%
439
29%
1563
29%
439
78%
439
49%
690
June1st to 15thNight
83%
360
31%
1440
39%
360
85%
360
54%
554
June16th to endNight
95%
360
39%
1440
53%
360
96%
360
76%
434
July1st to 15thNight
94%
340
35%
1360
46%
340
94%
340
68%
448
July16th to endNight
89%
449
38%
1483
40%
421
90%
421
59%
598
August1st to 15thNight
91%
687
37%
1761
26%
684
91%
684
78%
787
August16th to endNight
92%
764
44%
1910
29%
764
92%
764
77%
880
September1st to 15thNight
92%
720
43%
1800
32%
720
92%
720
78%
820
September16th to endNight
89%
716
45%
1962
42%
716
91%
716
73%
863
October1st to 15thNight
80%
720
32%
2091
34%
720
81%
720
56%
1004
October16th to endNight
81%
768
40%
2326
44%
768
83%
768
55%
1098
November1st to 15thNight
76%
700
31%
2275
34%
700
78%
700
45%
1123
November16th to endNight
70%
720
30%
2340
33%
720
73%
720
39%
1240
December1st to 15thNight
65%
720
24%
2454
24%
720
69%
720
30%
1404
December16th to endNight
53%
768
24%
2688
22%
768
61%
768
27%
1574

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%12212335%62%
48382
Night
8%412212235%64%
47555
TransparencyDay
25%47%21%26%16%
48060
Night
23%39%23%26%14%
47377
SeeingDay
12%9%30%32%11%4
6005
Night
10%17%31%35%13%
15589

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
15%6%12213346%51%
1432
16th to endDay
16%9%13423335%45%
1725
February1st to 15thDay
14%9%23323336%47%
1703
16th to endDay
18%12%3332333441%
1579
March1st to 15thDay
14%11%23423447%41%
1815
16th to endDay
15%9%243245%36%42%
2223
April1st to 15thDay
12%11%34323335%46%
2149
16th to endDay
11%6%23323346%51%
2160
May1st to 15thDay
8%412212246%62%
2262
16th to endDay
10%413322346%56%
2548
June1st to 15thDay
4213313346%65%
2520
16th to endDay
1111111284%
2520
July1st to 15thDay
11121222379%
2520
16th to endDay
21211223477%
2582
August1st to 15thDay
1111112285%
2190
16th to endDay
11121122382%
2292
September1st to 15thDay
21121122381%
2160
16th to endDay
32111132478%
1998
October1st to 15thDay
5%31121334467%
1866
16th to endDay
7%212312435%65%
1894
November1st to 15thDay
9%6%2331344456%
1584
16th to endDay
8%5%23323246%57%
1620
December1st to 15thDay
15%6%23423336%48%
1504
16th to endDay
15%9%35%313336%44%
1536
January1st to 15thNight
13%41222335%6%55%
2506
16th to endNight
14%7%12223336%51%
2496
February1st to 15thNight
13%7%12224349%47%
2148
16th to endNight
16%8%23223345%47%
1895
March1st to 15thNight
12%6%23324346%51%
2142
16th to endNight
11%6%12223338%53%
2001
April1st to 15thNight
11%7%1232335%6%51%
1799
16th to endNight
8%412322335%63%
1800
May1st to 15thNight
4212224235%68%
1685
16th to endNight
7%22112335%69%
1562
June1st to 15thNight
4212112135%73%
1440
16th to endNight
111289%
1440
July1st to 15thNight
1112122482%
1440
16th to endNight
211221222376%
1585
August1st to 15thNight
211111285%
1770
16th to endNight
112111285%
1910
September1st to 15thNight
111112285%
1800
16th to endNight
11111122282%
1962
October1st to 15thNight
5%21111223471%
2091
16th to endNight
6%1221232471%
2326
November1st to 15thNight
8%412212236%64%
2275
16th to endNight
8%5%23323346%57%
2340
December1st to 15thNight
14%5%13224347%50%
2454
16th to endNight
19%5%22323336%47%
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
33%5%8%22%21%9%
1432
16th to endDay
40%48%18%15%12%
1725
February1st to 15thDay
38%47%25%17%6%
1703
16th to endDay
46%47%24%14%1
1579
March1st to 15thDay
41%5%12%17%17%5%
1815
16th to endDay
41%6%14%22%13%2
2223
April1st to 15thDay
39%410%25%17%1
2149
16th to endDay
33%412%29%18%2
2160
May1st to 15thDay
23%39%32%27%3
2262
16th to endDay
28%5%10%33%20%2
2552
June1st to 15thDay
19%410%22%28%13%
2520
16th to endDay
8%1214%44%27%
2520
July1st to 15thDay
10%319%29%44%
2371
16th to endDay
12%2313%26%41%
2421
August1st to 15thDay
7%1213%35%39%
2174
16th to endDay
9%2113%44%28%
2292
September1st to 15thDay
10%2314%38%31%
2160
16th to endDay
11%3326%37%18%
1998
October1st to 15thDay
20%35%21%29%18%
1866
16th to endDay
20%45%22%28%18%
1894
November1st to 15thDay
29%5%9%22%22%11%
1584
16th to endDay
28%38%21%30%6%
1620
December1st to 15thDay
37%5%8%21%21%5%
1504
16th to endDay
41%310%19%15%9%
1536
January1st to 15thNight
29%310%26%22%7%
2506
16th to endNight
33%5%8%19%20%12%
2496
February1st to 15thNight
34%38%28%16%7%
2159
16th to endNight
37%410%27%16%2
1895
March1st to 15thNight
33%414%22%19%5%
2142
16th to endNight
30%5%18%26%16%3
2001
April1st to 15thNight
32%5%15%29%14%3
1799
16th to endNight
24%416%32%18%3
1800
May1st to 15thNight
19%311%34%26%4
1686
16th to endNight
17%411%35%26%3
1563
June1st to 15thNight
14%212%24%31%13%
1440
16th to endNight
5%1315%46%28%
1440
July1st to 15thNight
7%2211%33%41%
1360
16th to endNight
14%2412%27%40%
1483
August1st to 15thNight
8%1215%32%40%
1761
16th to endNight
8%1114%44%28%
1910
September1st to 15thNight
7%2217%37%33%
1800
16th to endNight
8%2328%39%17%
1962
October1st to 15thNight
16%37%24%31%16%
2091
16th to endNight
17%3427%28%18%
2326
November1st to 15thNight
22%310%25%24%13%
2275
16th to endNight
28%38%22%28%7%
2340
December1st to 15thNight
33%5%11%21%20%6%
2454
16th to endNight
38%311%18%17%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
55%320%10%6%5%
60
16th to endDay
25%6%23%25%14%4
253
February1st to 15thDay
24%7%22%24%14%5%
258
16th to endDay
25%14%27%22%8%
238
March1st to 15thDay
20%13%31%16%13%4
270
16th to endDay
23%11%32%22%7%1
288
April1st to 15thDay
23%15%30%22%5%1
269
16th to endDay
18%14%40%21%41
270
May1st to 15thDay
15%12%35%26%5%4
288
16th to endDay
18%10%26%28%10%6%
330
June1st to 15thDay
6%14%32%31%11%4
315
16th to endDay
7%31%39%13%7%
315
July1st to 15thDay
2128%46%12%8%
305
16th to endDay
3325%50%7%8%
327
August1st to 15thDay
26%37%38%7%7%
315
16th to endDay
1229%47%12%6%
332
September1st to 15thDay
35%36%41%11%2
315
16th to endDay
6%8%35%37%10%1
315
October1st to 15thDay
5%15%34%33%9%1
315
16th to endDay
9%6%25%38%17%2
312
November1st to 15thDay
12%6%8%20%40%12%
90
16th to endDay
10%16%26%30%14%2
90
December1st to 15thDay
19%233%25%15%2
71
16th to endDay
18%423%28%15%9%
64
January1st to 15thNight
15%10%32%25%15%
720
16th to endNight
19%211%34%21%10%
768
February1st to 15thNight
17%19%35%23%12%
704
16th to endNight
21%27%36%23%8%
632
March1st to 15thNight
14%47%38%25%10%
720
16th to endNight
14%29%35%30%8%
768
April1st to 15thNight
16%27%40%26%7%
719
16th to endNight
9%311%35%28%11%
720
May1st to 15thNight
5%38%37%34%8%
606
16th to endNight
8%9%30%38%12%
440
June1st to 15thNight
41333%48%9%
360
16th to endNight
33%54%10%
360
July1st to 15thNight
213%71%11%
340
16th to endNight
2114%59%22%
449
August1st to 15thNight
2220%59%14%
687
16th to endNight
2117%60%18%
764
September1st to 15thNight
2123%51%20%
720
16th to endNight
25%28%41%20%
716
October1st to 15thNight
7%16%34%33%16%
720
16th to endNight
7%1428%35%23%
768
November1st to 15thNight
10%16%32%33%16%
700
16th to endNight
11%29%35%26%13%
720
December1st to 15thNight
16%38%40%21%10%
720
16th to endNight
21%414%33%20%5%
768
Page generated at 2017-11-01 14:23:33. Version ac04

Copyright 2017 A. Danko


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