Silverwood Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Silverwood Lake clear sky chart from 2005-11-05 to 2017-12-01.

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
71%
16212
34%
47575
29%
16169
76%
16169
52%
23283

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
58%
717
29%
2327
25%
716
66%
716
39%
1200
January16th to endNight
55%
768
32%
2316
23%
768
66%
768
37%
1276
February1st to 15thNight
61%
699
32%
2107
28%
698
69%
698
42%
1106
February16th to endNight
56%
632
29%
1895
28%
632
61%
632
33%
1113
March1st to 15thNight
61%
720
29%
2160
26%
720
69%
720
42%
1149
March16th to endNight
66%
768
30%
2025
23%
768
71%
768
46%
1122
April1st to 15thNight
58%
719
28%
1799
16%
719
63%
719
46%
1029
April16th to endNight
64%
720
32%
1800
17%
720
69%
720
55%
963
May1st to 15thNight
72%
575
33%
1655
23%
575
75%
575
56%
798
May16th to endNight
70%
561
32%
1685
25%
561
73%
561
56%
788
June1st to 15thNight
80%
540
33%
1620
30%
540
81%
540
67%
690
June16th to endNight
94%
372
42%
1452
48%
372
95%
372
79%
438
July1st to 15thNight
94%
371
35%
1391
40%
371
94%
371
69%
475
July16th to endNight
86%
613
32%
1638
25%
576
87%
576
61%
769
August1st to 15thNight
92%
717
37%
1790
24%
713
93%
713
81%
802
August16th to endNight
93%
764
44%
1910
30%
764
94%
764
81%
857
September1st to 15thNight
90%
720
39%
1854
31%
720
91%
720
70%
883
September16th to endNight
88%
716
47%
1980
43%
716
91%
716
78%
828
October1st to 15thNight
75%
720
37%
1980
33%
720
80%
720
59%
969
October16th to endNight
74%
768
41%
2337
41%
768
79%
768
55%
1076
November1st to 15thNight
73%
760
33%
2470
33%
760
80%
760
52%
1120
November16th to endNight
70%
780
37%
2535
38%
780
75%
780
45%
1232
December1st to 15thNight
60%
724
31%
2353
28%
724
68%
724
37%
1246
December16th to endNight
50%
768
32%
2496
26%
768
60%
768
33%
1354

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
2212212336%69%
48835
Night
2313213335%68%
47772
TransparencyDay
17%26%15%27%30%
48528
Night
19%26%15%26%28%
47581
SeeingDay
412%35%32%10%3
6164
Night
4414%33%33%10%
16223

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
6%313323347%60%
1611
16th to endDay
6%423323345%57%
1906
February1st to 15thDay
35%23314246%61%
1751
16th to endDay
7%6%35%323347%52%
1579
March1st to 15thDay
5%31222326%7%61%
1800
16th to endDay
3213324447%61%
2196
April1st to 15thDay
4323223447%62%
2149
16th to endDay
2212212336%71%
2160
May1st to 15thDay
1212212347%70%
2295
16th to endDay
2212111336%74%
2429
June1st to 15thDay
112211336%76%
2340
16th to endDay
1111288%
2502
July1st to 15thDay
111212335%75%
2481
16th to endDay
1112213446%70%
2415
August1st to 15thDay
11133481%
2160
16th to endDay
1212235%79%
2292
September1st to 15thDay
11111235%79%
2105
16th to endDay
11121223282%
1980
October1st to 15thDay
221221323472%
1980
16th to endDay
12231233473%
1882
November1st to 15thDay
1212224436%67%
1719
16th to endDay
4312323437%63%
1755
December1st to 15thDay
42124145%5%9%56%
1620
16th to endDay
8%5%14323336%56%
1728
January1st to 15thNight
5%424423346%59%
2327
16th to endNight
7%424413445%57%
2316
February1st to 15thNight
46%14324345%60%
2101
16th to endNight
5%7%34324446%51%
1895
March1st to 15thNight
242441335%6%60%
2160
16th to endNight
15%23323448%60%
2025
April1st to 15thNight
3424422348%59%
1799
16th to endNight
2313213346%67%
1800
May1st to 15thNight
32312247%69%
1655
16th to endNight
1212222346%70%
1684
June1st to 15thNight
112112225%78%
1620
16th to endNight
1111289%
1452
July1st to 15thNight
1111232479%
1473
16th to endNight
2212213236%71%
1750
August1st to 15thNight
1111212483%
1800
16th to endNight
111122383%
1910
September1st to 15thNight
11211222479%
1854
16th to endNight
111122284%
1980
October1st to 15thNight
2312212235%71%
1980
16th to endNight
131321323472%
2337
November1st to 15thNight
2212323345%68%
2470
16th to endNight
341232335%6%63%
2535
December1st to 15thNight
6%5%23423347%56%
2353
16th to endNight
6%6%24314345%57%
2496

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
24%37%16%26%21%
1612
16th to endDay
29%37%15%22%22%
1906
February1st to 15thDay
24%35%17%25%23%
1751
16th to endDay
34%27%15%27%12%
1579
March1st to 15thDay
21%310%21%23%20%
1800
16th to endDay
24%39%22%24%15%
2196
April1st to 15thDay
24%38%22%28%13%
2149
16th to endDay
16%39%20%29%20%
2160
May1st to 15thDay
17%28%20%28%22%
2295
16th to endDay
15%27%22%36%15%
2432
June1st to 15thDay
12%16%12%33%33%
2340
16th to endDay
6%35%23%60%
2502
July1st to 15thDay
11%25%8%22%49%
2335
16th to endDay
14%47%17%23%32%
2264
August1st to 15thDay
7%149%25%50%
2146
16th to endDay
9%2410%32%40%
2292
September1st to 15thDay
9%25%10%28%42%
2105
16th to endDay
9%1310%32%43%
1980
October1st to 15thDay
17%2413%29%32%
1980
16th to endDay
15%2411%24%41%
1882
November1st to 15thDay
19%27%14%30%25%
1719
16th to endDay
23%26%14%24%29%
1755
December1st to 15thDay
23%5%10%19%20%20%
1620
16th to endDay
30%5%8%18%21%16%
1728
January1st to 15thNight
25%46%14%24%24%
2327
16th to endNight
29%39%12%19%25%
2316
February1st to 15thNight
25%38%16%22%23%
2112
16th to endNight
33%45%16%24%15%
1895
March1st to 15thNight
25%38%18%23%20%
2160
16th to endNight
23%48%23%25%14%
2025
April1st to 15thNight
25%39%23%23%14%
1799
16th to endNight
19%27%22%29%18%
1800
May1st to 15thNight
17%27%23%29%19%
1656
16th to endNight
16%39%22%33%14%
1685
June1st to 15thNight
12%1415%32%33%
1620
16th to endNight
5%36%24%58%
1452
July1st to 15thNight
8%15%9%19%54%
1391
16th to endNight
14%37%15%27%31%
1638
August1st to 15thNight
6%1410%31%45%
1790
16th to endNight
7%149%34%43%
1910
September1st to 15thNight
11%25%8%31%40%
1854
16th to endNight
7%1212%33%41%
1980
October1st to 15thNight
17%2414%33%29%
1980
16th to endNight
17%248%26%41%
2337
November1st to 15thNight
18%26%14%29%27%
2470
16th to endNight
22%35%15%23%29%
2535
December1st to 15thNight
28%47%15%22%21%
2353
16th to endNight
29%49%15%23%16%
2496

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
24%11%27%30%6%
90
16th to endDay
12%21%30%26%8%1
274
February1st to 15thDay
6%19%37%24%9%1
266
16th to endDay
14%24%30%22%7%
238
March1st to 15thDay
8%20%32%24%11%1
270
16th to endDay
5%18%44%21%8%1
288
April1st to 15thDay
7%24%40%14%8%2
269
16th to endDay
234%33%22%32
270
May1st to 15thDay
417%40%28%5%3
288
16th to endDay
412%46%26%6%3
330
June1st to 15thDay
114%40%31%9%3
315
16th to endDay
1334%42%9%7%
315
July1st to 15thDay
231%42%15%6%
305
16th to endDay
2124%49%14%8%
327
August1st to 15thDay
1239%38%9%9%
315
16th to endDay
225%46%13%10%
332
September1st to 15thDay
1142%39%12%2
315
16th to endDay
19%33%39%14%1
315
October1st to 15thDay
312%41%30%10%
315
16th to endDay
49%31%30%19%3
271
November1st to 15thDay
5%11%22%32%22%6%
135
16th to endDay
5%16%25%30%19%2
135
December1st to 15thDay
6%14%23%38%14%2
90
16th to endDay
14%10%30%32%12%
96
January1st to 15thNight
7%7%21%35%21%6%
720
16th to endNight
9%7%21%32%23%5%
768
February1st to 15thNight
6%6%19%37%23%6%
704
16th to endNight
11%7%20%33%20%6%
632
March1st to 15thNight
5%6%22%38%22%5%
720
16th to endNight
46%18%38%26%5%
768
April1st to 15thNight
49%22%35%21%6%
719
16th to endNight
35%22%33%27%7%
720
May1st to 15thNight
2318%38%29%7%
576
16th to endNight
2320%36%29%7%
563
June1st to 15thNight
1114%41%37%4
540
16th to endNight
435%52%7%
372
July1st to 15thNight
1120%63%13%
371
16th to endNight
15%27%52%12%
613
August1st to 15thNight
1225%53%17%
717
16th to endNight
1119%52%25%
764
September1st to 15thNight
1326%47%20%
720
16th to endNight
17%30%44%15%
716
October1st to 15thNight
3313%36%33%9%
720
16th to endNight
3311%32%31%16%
768
November1st to 15thNight
3215%36%32%10%
760
16th to endNight
5%5%13%36%28%10%
780
December1st to 15thNight
9%6%17%33%26%6%
724
16th to endNight
9%10%23%32%20%4
768
Page generated at 2017-12-02 06:14:27. Version ac04

Copyright 2017 A. Danko


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