Silver Linings Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Silver Linings Observatory clear sky chart from 2005-11-05 to 2017-09-10.

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%
15334
23%
46831
19%
15287
60%
15287
31%
27974

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
37%
899
23%
2327
11%
895
43%
895
28%
1554
January16th to endNight
38%
960
23%
2496
11%
960
44%
960
29%
1639
February1st to 15thNight
40%
758
23%
2162
12%
752
47%
752
27%
1402
February16th to endNight
34%
524
25%
1786
13%
524
46%
524
25%
1088
March1st to 15thNight
37%
540
25%
1980
17%
540
49%
540
22%
1220
March16th to endNight
42%
576
23%
2112
18%
576
50%
576
28%
1199
April1st to 15thNight
42%
539
21%
1953
17%
539
52%
539
24%
1162
April16th to endNight
39%
540
22%
1800
17%
540
47%
540
24%
1130
May1st to 15thNight
44%
539
20%
1707
16%
539
51%
539
29%
1019
May16th to endNight
61%
562
24%
1685
24%
561
65%
561
35%
982
June1st to 15thNight
79%
540
20%
1620
23%
540
81%
540
47%
832
June16th to endNight
77%
540
16%
1620
20%
540
78%
540
35%
961
July1st to 15thNight
79%
510
18%
1530
23%
510
79%
510
38%
865
July16th to endNight
83%
564
19%
1594
23%
531
84%
531
38%
902
August1st to 15thNight
90%
539
27%
1610
30%
536
90%
536
56%
762
August16th to endNight
78%
573
16%
1951
19%
573
78%
573
27%
1192
September1st to 15thNight
73%
525
16%
1925
18%
525
75%
525
28%
1109
September16th to endNight
72%
492
27%
1815
31%
492
73%
492
29%
1019
October1st to 15thNight
75%
597
33%
1917
30%
597
77%
597
45%
962
October16th to endNight
63%
704
35%
2112
26%
704
68%
704
44%
1109
November1st to 15thNight
60%
700
27%
2100
22%
700
62%
700
34%
1233
November16th to endNight
53%
753
32%
2193
21%
753
60%
753
37%
1271
December1st to 15thNight
41%
900
24%
2340
14%
900
46%
900
25%
1621
December16th to endNight
36%
960
20%
2496
9%
960
41%
960
24%
1741

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
12%6%36%6%35%5%6%7%37%
47781
Night
11%5%2442445%8%48%
47030
TransparencyDay
43%7%11%16%14%6%
47481
Night
34%6%13%20%16%8%
46835
SeeingDay
11%315%26%27%15%
5337
Night
13%5%20%33%25%3
15337

By Month

Percentage Cloud Cover SE (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
19%6%25%425%345%40%
1611
16th to endDay
19%7%25%323235%44%
1728
February1st to 15thDay
18%8%35%422335%42%
1705
16th to endDay
20%8%35%323335%39%
1685
March1st to 15thDay
21%7%35%424335%38%
1980
16th to endDay
15%5%36%5%2435%6%40%
2110
April1st to 15thDay
14%6%35%5%35%45%6%39%
1992
16th to endDay
13%7%36%5%34447%37%
2160
May1st to 15thDay
10%6%38%7%35%5%6%7%34%
2241
16th to endDay
9%5%37%6%46%6%7%9%32%
2430
June1st to 15thDay
4326%8%47%7%7%10%36%
2340
16th to endDay
7%5%37%8%5%9%9%7%9%25%
2340
July1st to 15thDay
9%5%36%6%48%7%7%10%27%
2340
16th to endDay
6%437%8%6%9%9%7%10%25%
2466
August1st to 15thDay
33146%5%8%8%8%11%36%
2340
16th to endDay
9%5%26%8%5%7%7%7%9%30%
2244
September1st to 15thDay
9%5%36%8%46%6%8%9%31%
1922
16th to endDay
11%6%26%6%46%6%5%7%35%
1815
October1st to 15thDay
9%415%33445%6%49%
1702
16th to endDay
8%424323345%57%
1760
November1st to 15thDay
9%6%35%5%25%46%9%40%
1758
16th to endDay
13%6%35%423335%47%
1764
December1st to 15thDay
16%8%36%7%34447%34%
1620
16th to endDay
18%7%36%5%24446%36%
1728
January1st to 15thNight
18%7%34423346%42%
2327
16th to endNight
19%5%24413345%45%
2496
February1st to 15thNight
17%5%34324335%46%
2156
16th to endNight
15%6%35%423336%45%
1786
March1st to 15thNight
19%6%2432345%5%42%
1980
16th to endNight
10%424424347%50%
2112
April1st to 15thNight
12%435%424447%44%
1953
16th to endNight
15%6%2443445%7%42%
1800
May1st to 15thNight
9%6%25%415%5%7%9%43%
1706
16th to endNight
5%423425%6%7%11%46%
1683
June1st to 15thNight
321341436%11%57%
1620
16th to endNight
4324425%5%8%12%46%
1620
July1st to 15thNight
5%32433445%13%50%
1620
16th to endNight
3313425%6%6%11%51%
1702
August1st to 15thNight
11231335%12%63%
1620
16th to endNight
5%315%5%35%6%7%11%44%
1951
September1st to 15thNight
6%425%5%3446%10%47%
1925
16th to endNight
7%5%15%4235%6%8%48%
1815
October1st to 15thNight
6%21222335%8%60%
1917
16th to endNight
8%31342323463%
2112
November1st to 15thNight
10%5%24423447%50%
2100
16th to endNight
13%32332334455%
2193
December1st to 15thNight
17%6%26%434446%39%
2340
16th to endNight
17%9%26%5%23446%39%
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
46%45%14%20%9%
1612
16th to endDay
44%25%16%17%13%
1728
February1st to 15thDay
45%35%16%15%12%
1706
16th to endDay
46%5%7%13%18%9%
1685
March1st to 15thDay
49%38%12%18%6%
1980
16th to endDay
43%5%7%14%21%6%
2112
April1st to 15thDay
44%5%8%17%16%8%
1992
16th to endDay
46%5%8%17%14%7%
2160
May1st to 15thDay
46%7%11%14%12%7%
2241
16th to endDay
42%8%12%18%13%2
2434
June1st to 15thDay
38%10%15%18%15%1
2340
16th to endDay
47%11%16%17%6%
2340
July1st to 15thDay
44%11%17%19%5%
2201
16th to endDay
45%12%19%19%2
2311
August1st to 15thDay
35%10%19%26%7%
2326
16th to endDay
46%12%17%16%7%1
2244
September1st to 15thDay
46%10%15%15%8%3
1922
16th to endDay
46%6%10%14%17%5%
1815
October1st to 15thDay
33%6%8%20%15%15%
1702
16th to endDay
30%36%14%28%16%
1760
November1st to 15thDay
39%6%10%17%18%8%
1758
16th to endDay
40%35%12%20%17%
1764
December1st to 15thDay
49%48%15%14%7%
1620
16th to endDay
48%5%8%15%15%7%
1728
January1st to 15thNight
42%36%15%20%12%
2327
16th to endNight
41%37%15%18%13%
2496
February1st to 15thNight
40%46%13%19%14%
2166
16th to endNight
41%36%16%20%12%
1786
March1st to 15thNight
42%49%15%17%10%
1980
16th to endNight
34%5%12%16%21%9%
2112
April1st to 15thNight
38%5%10%18%17%10%
1953
16th to endNight
41%5%11%17%14%9%
1800
May1st to 15thNight
35%6%14%20%13%9%
1707
16th to endNight
28%8%18%26%13%3
1685
June1st to 15thNight
20%6%20%28%21%1
1620
16th to endNight
27%10%23%27%10%
1620
July1st to 15thNight
26%7%28%30%6%
1530
16th to endNight
22%11%29%32%3
1594
August1st to 15thNight
14%6%29%40%9%
1610
16th to endNight
31%12%24%24%5%1
1951
September1st to 15thNight
31%9%22%21%11%3
1925
16th to endNight
31%7%13%21%18%6%
1815
October1st to 15thNight
21%6%11%26%19%14%
1917
16th to endNight
25%26%17%27%20%
2112
November1st to 15thNight
32%5%12%22%18%8%
2100
16th to endNight
32%38%15%22%17%
2193
December1st to 15thNight
45%49%17%14%7%
2340
16th to endNight
47%37%15%15%10%
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
28%127%32%10%
90
16th to endDay
21%7%39%22%8%
96
February1st to 15thDay
10%15%31%32%8%2
90
16th to endDay
13%9%41%27%7%
81
March1st to 15thDay
28%11%38%10%11%
90
16th to endDay
18%5%33%27%10%5%
96
April1st to 15thDay
12%17%19%29%18%2
111
16th to endDay
20%7%26%22%20%2
270
May1st to 15thDay
14%8%32%28%15%
378
16th to endDay
9%327%36%18%4
517
June1st to 15thDay
6%10%32%38%11%
495
16th to endDay
7%19%30%31%18%
495
July1st to 15thDay
8%6%28%32%24%
475
16th to endDay
5%1222%37%29%
515
August1st to 15thDay
4319%40%30%
493
16th to endDay
14%1412%34%32%
284
September1st to 15thDay
9%5%19%30%34%
119
16th to endDay
11%113%45%28%
90
October1st to 15thDay
4337%43%11%
90
16th to endDay
18%212%29%22%14%
96
November1st to 15thDay
18%226%27%16%7%
90
16th to endDay
21%5%28%24%12%7%
90
December1st to 15thDay
23%324%32%8%7%
90
16th to endDay
26%13%32%19%6%2
96
January1st to 15thNight
22%8%26%31%11%
900
16th to endNight
20%8%28%33%8%
960
February1st to 15thNight
19%8%26%35%9%
758
16th to endNight
19%7%35%30%7%
524
March1st to 15thNight
23%7%27%33%7%
540
16th to endNight
11%7%34%34%10%
576
April1st to 15thNight
12%7%30%39%9%
539
16th to endNight
17%7%32%28%14%
540
May1st to 15thNight
10%7%32%39%9%
540
16th to endNight
6%323%44%20%1
563
June1st to 15thNight
48%48%36%1
540
16th to endNight
5%7%36%45%5%
540
July1st to 15thNight
5%1430%50%7%
510
16th to endNight
21425%54%11%
564
August1st to 15thNight
1125%60%10%
539
16th to endNight
7%222%54%12%
573
September1st to 15thNight
8%5%21%52%11%
525
16th to endNight
10%7%27%44%9%
492
October1st to 15thNight
7%111%34%40%5%
597
16th to endNight
8%417%35%29%4
704
November1st to 15thNight
11%417%37%26%2
700
16th to endNight
14%6%23%34%19%1
753
December1st to 15thNight
19%6%25%32%14%1
900
16th to endNight
21%8%29%29%11%1
960
Page generated at 2017-09-11 18:35:26. Version ac04

Copyright 2017 A. Danko


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