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 2017-04-26.

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
74%
14984
30%
45585
28%
14950
76%
14950
45%
23449

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%
704
23%
1760
13%
704
71%
704
47%
1012
May1st to 15thNight
74%
555
29%
1545
21%
555
76%
555
52%
774
May16th to endNight
77%
401
26%
1429
27%
401
79%
401
49%
632
June1st to 15thNight
83%
330
32%
1320
41%
330
85%
330
53%
514
June16th to endNight
95%
330
37%
1320
49%
330
95%
330
75%
403
July1st to 15thNight
93%
310
37%
1240
49%
310
93%
310
68%
410
July16th to endNight
89%
415
35%
1365
37%
387
89%
387
57%
560
August1st to 15thNight
92%
629
40%
1613
28%
626
92%
626
80%
712
August16th to endNight
92%
700
42%
1750
28%
700
92%
700
77%
807
September1st to 15thNight
92%
660
46%
1650
34%
660
92%
660
79%
748
September16th to endNight
90%
656
44%
1798
41%
656
91%
656
72%
795
October1st to 15thNight
78%
660
32%
1917
35%
660
80%
660
54%
943
October16th to endNight
80%
704
38%
2132
41%
704
83%
704
54%
1012
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%61%
46076
Night
8%412212335%63%
45773
TransparencyDay
25%47%21%26%15%
45754
Night
23%39%23%26%13%
45595
SeeingDay
13%9%31%32%9%4
5263
Night
10%27%31%35%13%
14995

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%
2111
May1st to 15thDay
8%412212245%63%
2073
16th to endDay
11%413322346%55%
2330
June1st to 15thDay
4213313346%65%
2310
16th to endDay
11111111383%
2310
July1st to 15thDay
11121222479%
2310
16th to endDay
211211223476%
2393
August1st to 15thDay
11112287%
2008
16th to endDay
11121122382%
2100
September1st to 15thDay
2111111383%
1980
16th to endDay
32111132477%
1832
October1st to 15thDay
6%41221334464%
1711
16th to endDay
7%212312435%64%
1738
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%413322335%62%
1760
May1st to 15thNight
5%112323235%68%
1545
16th to endNight
7%21112335%68%
1428
June1st to 15thNight
4112112135%72%
1320
16th to endNight
121288%
1320
July1st to 15thNight
1112122482%
1320
16th to endNight
211221232375%
1467
August1st to 15thNight
111111286%
1622
16th to endNight
1112111285%
1750
September1st to 15thNight
1111112286%
1650
16th to endNight
11111222282%
1798
October1st to 15thNight
6%311122235%68%
1917
16th to endNight
6%1221232471%
2132
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%1
2111
May1st to 15thDay
23%39%30%28%4
2073
16th to endDay
28%5%10%33%18%2
2334
June1st to 15thDay
19%5%10%22%27%14%
2310
16th to endDay
9%1214%46%24%
2310
July1st to 15thDay
10%3210%29%43%
2161
16th to endDay
12%3414%27%38%
2232
August1st to 15thDay
5%2213%37%39%
1992
16th to endDay
9%2113%44%28%
2100
September1st to 15thDay
9%2312%39%32%
1980
16th to endDay
11%3323%37%19%
1832
October1st to 15thDay
22%45%23%30%13%
1711
16th to endDay
20%5%5%23%30%15%
1738
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%5%15%32%18%3
1760
May1st to 15thNight
18%411%32%27%5%
1546
16th to endNight
17%5%12%35%26%3
1429
June1st to 15thNight
15%212%24%30%13%
1320
16th to endNight
5%1314%48%26%
1320
July1st to 15thNight
7%2212%32%41%
1240
16th to endNight
14%2412%27%37%
1365
August1st to 15thNight
7%1215%34%39%
1613
16th to endNight
8%114%44%29%
1750
September1st to 15thNight
7%2214%39%34%
1650
16th to endNight
9%3326%39%18%
1798
October1st to 15thNight
18%48%26%32%10%
1917
16th to endNight
17%35%28%29%15%
2132
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
19%12%41%20%31
254
May1st to 15thDay
15%14%38%24%43
228
16th to endDay
20%11%26%29%6%5%
266
June1st to 15thDay
5%16%34%31%7%3
255
16th to endDay
19%35%38%8%7%
255
July1st to 15thDay
2232%47%8%6%
245
16th to endDay
3426%52%5%8%
271
August1st to 15thDay
27%38%40%5%7%
255
16th to endDay
1231%49%8%6%
268
September1st to 15thDay
3334%44%10%2
255
16th to endDay
7%7%34%39%9%2
255
October1st to 15thDay
5%16%35%34%7%1
255
16th to endDay
10%6%29%39%12%
250
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%
704
May1st to 15thNight
5%38%37%34%9%
556
16th to endNight
8%8%29%39%13%
402
June1st to 15thNight
41432%49%8%
330
16th to endNight
32%55%9%
330
July1st to 15thNight
212%73%10%
310
16th to endNight
2113%59%22%
415
August1st to 15thNight
1220%59%15%
629
16th to endNight
21117%60%17%
700
September1st to 15thNight
2121%51%22%
660
16th to endNight
2426%43%21%
656
October1st to 15thNight
8%16%32%33%16%
660
16th to endNight
7%15%29%34%21%
704
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 2017-04-27 14:48:54. Version ac04

Copyright 2017 A. Danko


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