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Standing Stone Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Standing Stone Observatory clear sky chart from 2005-11-05 to 2020-06-03.

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
41%
19380
17%
57815
11%
19341
47%
19341
20%
39782

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
19%
898
14%
2912
6%
896
28%
896
9%
2202
January16th to endNight
16%
960
15%
3120
6%
960
28%
960
12%
2276
February1st to 15thNight
19%
882
12%
2872
6%
881
29%
881
12%
2079
February16th to endNight
17%
791
15%
2358
7%
791
26%
791
11%
1790
March1st to 15thNight
23%
900
16%
2475
7%
900
31%
900
15%
1788
March16th to endNight
27%
960
14%
2640
7%
960
33%
960
16%
1925
April1st to 15thNight
30%
898
15%
2362
6%
898
37%
898
21%
1653
April16th to endNight
39%
752
18%
2088
8%
752
46%
752
22%
1419
May1st to 15thNight
41%
675
14%
2025
8%
675
46%
675
20%
1398
May16th to endNight
53%
705
13%
2116
10%
705
56%
705
22%
1473
June1st to 15thNight
61%
637
14%
1913
12%
637
64%
637
27%
1233
June16th to endNight
67%
630
16%
1890
13%
630
69%
630
30%
1153
July1st to 15thNight
64%
600
12%
1800
12%
600
65%
600
25%
1215
July16th to endNight
73%
660
15%
1883
12%
627
75%
627
30%
1168
August1st to 15thNight
66%
620
19%
1850
16%
617
66%
617
27%
1219
August16th to endNight
70%
759
20%
2097
16%
759
71%
759
32%
1345
September1st to 15thNight
63%
840
22%
2229
17%
840
65%
840
30%
1454
September16th to endNight
58%
837
19%
2310
17%
837
60%
837
28%
1514
October1st to 15thNight
53%
840
23%
2489
21%
840
58%
840
27%
1578
October16th to endNight
38%
896
24%
2688
18%
896
48%
896
23%
1749
November1st to 15thNight
43%
880
23%
2728
18%
880
52%
880
24%
1726
November16th to endNight
34%
900
21%
2925
14%
900
44%
900
18%
1938
December1st to 15thNight
22%
900
13%
2925
8%
900
30%
900
11%
2188
December16th to endNight
24%
960
16%
3120
7%
960
34%
960
12%
2299

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
14%7%36%5%35%5%5%7%34%
58587
Night
13%7%36%5%3445%7%37%
58008
Cloud CoverDay
14%7%36%5%35%5%5%7%34%
58597
Night
12%7%36%5%3445%7%37%
58012
TransparencyDay
48%7%11%18%11%1
58298
Night
45%7%12%20%12%2
57815
SeeingDay
23%13%22%19%14%6%
9175
Night
19%12%20%27%17%1
19386

By Month

Percentage Cloud Cover NE (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%9%411%8%35%436%27%
2016
16th to endDay
15%12%47%5%33345%32%
2160
February1st to 15thDay
15%9%5%8%7%435%47%29%
1980
16th to endDay
16%11%5%10%5%35%346%28%
1992
March1st to 15thDay
17%8%5%7%42445%6%35%
2464
16th to endDay
17%9%37%5%24346%33%
2640
April1st to 15thDay
13%8%36%5%33347%41%
2576
16th to endDay
17%7%25%5%25%45%7%36%
2819
May1st to 15thDay
19%7%35%5%445%6%6%30%
2916
16th to endDay
14%6%26%6%36%6%6%8%32%
3055
June1st to 15thDay
12%5%25%6%46%6%5%8%36%
2756
16th to endDay
9%5%27%6%47%6%7%8%35%
2730
July1st to 15thDay
11%6%36%6%46%5%5%9%33%
2730
16th to endDay
10%5%27%7%5%7%6%8%9%29%
2881
August1st to 15thDay
14%7%25%7%46%7%7%9%27%
2682
16th to endDay
11%5%26%7%46%5%7%9%33%
2795
September1st to 15thDay
12%6%35%5%345%6%6%39%
2389
16th to endDay
16%6%36%6%345%45%36%
2310
October1st to 15thDay
17%6%15%423447%41%
2129
16th to endDay
16%8%35%323335%44%
2240
November1st to 15thDay
13%7%3443445%6%43%
2117
16th to endDay
13%8%46%434445%39%
2025
December1st to 15thDay
18%12%36%42445%6%31%
2025
16th to endDay
18%10%47%5%34446%30%
2160
January1st to 15thNight
16%9%410%8%35%45%5%26%
2912
16th to endNight
15%12%5%7%6%34345%30%
3120
February1st to 15thNight
15%10%5%7%5%34447%29%
2870
16th to endNight
15%9%5%8%7%45%5%45%27%
2358
March1st to 15thNight
15%9%47%5%3445%6%34%
2463
16th to endNight
16%8%35%5%25%5%5%6%34%
2640
April1st to 15thNight
11%7%36%5%3445%8%38%
2362
16th to endNight
14%5%34435%5%5%8%39%
2088
May1st to 15thNight
14%6%35%6%25%5%5%7%38%
2025
16th to endNight
10%6%36%5%35%5%6%9%37%
2114
June1st to 15thNight
8%5%24425%5%7%10%43%
1913
16th to endNight
7%3144346%7%11%45%
1890
July1st to 15thNight
8%425%5%35%5%7%8%41%
1890
16th to endNight
6%3245%36%6%8%10%43%
1991
August1st to 15thNight
9%5%26%435%5%5%7%44%
1861
16th to endNight
8%425%425%47%9%45%
2097
September1st to 15thNight
10%5%245%2346%6%47%
2229
16th to endNight
12%5%25%425%5%5%7%42%
2310
October1st to 15thNight
13%5%24424446%45%
2489
16th to endNight
13%7%25%5%24345%43%
2688
November1st to 15thNight
13%7%25%334445%45%
2728
16th to endNight
12%9%36%5%24446%39%
2925
December1st to 15thNight
17%10%48%6%35%5%5%6%26%
2925
16th to endNight
15%10%5%7%6%35%45%6%28%
3120

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
15%9%411%8%35%445%27%
2016
16th to endDay
16%11%5%7%6%33345%32%
2160
February1st to 15thDay
15%9%48%7%335%5%7%29%
1980
16th to endDay
16%11%5%9%5%34346%28%
1992
March1st to 15thDay
17%7%5%7%42345%6%35%
2475
16th to endDay
18%9%36%5%34446%33%
2639
April1st to 15thDay
13%8%36%5%33447%41%
2576
16th to endDay
17%7%25%5%25%45%7%36%
2819
May1st to 15thDay
19%7%35%6%345%6%7%30%
2916
16th to endDay
14%6%25%5%36%6%6%8%32%
3055
June1st to 15thDay
12%5%346%46%6%5%8%36%
2756
16th to endDay
9%5%27%6%46%6%8%8%34%
2730
July1st to 15thDay
11%6%36%7%45%5%6%8%33%
2730
16th to endDay
10%5%36%6%5%7%6%8%9%29%
2881
August1st to 15thDay
14%7%25%6%46%7%7%9%27%
2682
16th to endDay
11%6%26%7%45%5%7%9%34%
2795
September1st to 15thDay
12%6%35%5%3446%6%39%
2389
16th to endDay
17%6%36%6%35%5%46%35%
2310
October1st to 15thDay
17%6%2442245%6%41%
2129
16th to endDay
16%8%35%323325%44%
2240
November1st to 15thDay
13%7%3442445%6%43%
2117
16th to endDay
13%8%36%435%445%39%
2025
December1st to 15thDay
18%11%37%424446%31%
2025
16th to endDay
18%11%46%5%34446%29%
2160
January1st to 15thNight
16%9%411%7%35%445%26%
2912
16th to endNight
15%12%5%7%6%2434430%
3120
February1st to 15thNight
16%9%5%7%5%34447%29%
2863
16th to endNight
15%9%5%8%7%45%5%45%27%
2358
March1st to 15thNight
15%9%47%5%2445%6%34%
2475
16th to endNight
16%8%35%5%25%5%5%6%34%
2640
April1st to 15thNight
11%7%35%5%3445%8%38%
2362
16th to endNight
14%5%35%435%5%5%7%39%
2088
May1st to 15thNight
14%6%35%6%2445%7%38%
2024
16th to endNight
10%6%36%5%35%5%6%9%38%
2114
June1st to 15thNight
8%5%25%425%5%6%10%43%
1913
16th to endNight
7%4134346%6%11%45%
1890
July1st to 15thNight
8%425%5%35%5%7%8%41%
1890
16th to endNight
6%3245%36%6%8%10%43%
1991
August1st to 15thNight
9%5%26%5%25%45%8%43%
1861
16th to endNight
8%4245%2447%9%45%
2097
September1st to 15thNight
9%5%245%235%6%6%47%
2229
16th to endNight
12%5%25%435%5%5%7%42%
2310
October1st to 15thNight
13%5%24424446%45%
2489
16th to endNight
13%7%25%5%2444443%
2688
November1st to 15thNight
13%7%25%424445%45%
2728
16th to endNight
12%9%36%5%24446%40%
2925
December1st to 15thNight
17%11%48%6%3445%6%26%
2925
16th to endNight
15%11%5%7%5%35%5%5%6%28%
3120

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
59%49%15%9%1
2017
16th to endDay
54%49%18%11%1
2160
February1st to 15thDay
54%49%18%10%1
1982
16th to endDay
56%5%10%16%9%1
1992
March1st to 15thDay
49%5%11%20%11%2
2475
16th to endDay
52%6%9%19%11%1
2640
April1st to 15thDay
43%6%11%21%13%3
2576
16th to endDay
47%6%10%18%13%3
2819
May1st to 15thDay
52%8%12%16%8%1
2916
16th to endDay
47%11%14%17%7%1
3059
June1st to 15thDay
42%10%14%19%12%
2756
16th to endDay
44%10%13%17%12%1
2730
July1st to 15thDay
46%10%12%14%13%2
2591
16th to endDay
46%11%13%16%10%
2726
August1st to 15thDay
49%11%13%17%7%
2669
16th to endDay
43%11%15%17%10%1
2795
September1st to 15thDay
43%8%13%17%15%2
2389
16th to endDay
49%7%10%18%13%
2310
October1st to 15thDay
41%6%12%21%13%3
2129
16th to endDay
44%38%23%17%2
2240
November1st to 15thDay
41%49%20%19%4
2117
16th to endDay
45%5%9%22%15%
2025
December1st to 15thDay
53%5%10%16%11%2
2025
16th to endDay
56%410%18%9%1
2160
January1st to 15thNight
59%47%13%11%2
2912
16th to endNight
56%49%17%11%1
3120
February1st to 15thNight
53%5%11%16%10%1
2872
16th to endNight
57%5%9%16%8%2
2358
March1st to 15thNight
51%5%10%20%11%1
2475
16th to endNight
49%7%11%18%12%
2640
April1st to 15thNight
43%7%13%20%13%2
2362
16th to endNight
42%7%13%18%14%3
2088
May1st to 15thNight
44%9%15%18%11%1
2025
16th to endNight
41%11%17%21%6%1
2116
June1st to 15thNight
34%11%18%21%13%
1913
16th to endNight
30%11%18%24%13%1
1890
July1st to 15thNight
37%12%15%17%12%3
1800
16th to endNight
30%12%18%24%12%1
1883
August1st to 15thNight
37%10%15%24%12%
1850
16th to endNight
32%10%15%27%12%1
2097
September1st to 15thNight
35%9%15%20%16%2
2229
16th to endNight
38%7%12%24%15%
2310
October1st to 15thNight
37%6%11%25%15%3
2489
16th to endNight
43%47%24%16%3
2688
November1st to 15thNight
40%5%9%19%19%5%
2728
16th to endNight
45%5%9%20%16%2
2925
December1st to 15thNight
57%5%9%16%8%1
2925
16th to endNight
55%7%10%16%10%1
3120

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
36%27%24%8%2
225
16th to endDay
41%21%24%9%3
240
February1st to 15thDay
42%23%25%8%
225
16th to endDay
34%23%27%9%3
227
March1st to 15thDay
31%24%21%17%4
450
16th to endDay
28%21%26%14%7%1
480
April1st to 15thDay
22%22%25%18%10%
450
16th to endDay
29%16%22%14%12%3
439
May1st to 15thDay
27%17%21%16%11%5%
468
16th to endDay
17%8%27%19%17%9%
523
June1st to 15thDay
13%9%23%23%19%10%
443
16th to endDay
11%9%28%22%17%10%
435
July1st to 15thDay
12%421%26%20%14%
425
16th to endDay
13%214%28%23%17%
454
August1st to 15thDay
17%320%20%22%16%
418
16th to endDay
12%313%26%23%20%
460
September1st to 15thDay
14%5%16%22%26%14%
435
16th to endDay
19%6%15%27%22%8%
434
October1st to 15thDay
18%9%20%25%21%5%
435
16th to endDay
25%14%22%20%14%2
464
November1st to 15thDay
27%11%25%21%12%1
355
16th to endDay
28%17%24%22%5%
225
December1st to 15thDay
37%22%21%12%31
225
16th to endDay
37%16%25%13%5%
240
January1st to 15thNight
32%21%22%19%3
900
16th to endNight
30%21%27%18%1
960
February1st to 15thNight
31%18%25%22%1
884
16th to endNight
25%26%27%19%1
791
March1st to 15thNight
27%20%26%22%4
900
16th to endNight
23%17%26%22%9%
960
April1st to 15thNight
19%19%27%26%7%
898
16th to endNight
17%13%24%32%11%
752
May1st to 15thNight
16%11%22%30%16%1
675
16th to endNight
12%419%31%27%4
707
June1st to 15thNight
8%415%35%32%2
637
16th to endNight
8%213%37%34%3
630
July1st to 15thNight
9%112%37%34%4
600
16th to endNight
6%17%29%46%7%
660
August1st to 15thNight
12%11%36%35%4
620
16th to endNight
9%8%31%44%5%
759
September1st to 15thNight
10%5%12%30%35%6%
840
16th to endNight
15%5%14%29%32%2
837
October1st to 15thNight
13%9%17%29%26%2
840
16th to endNight
20%14%21%27%14%1
896
November1st to 15thNight
19%11%20%32%14%1
880
16th to endNight
21%17%21%28%9%
900
December1st to 15thNight
29%19%23%20%6%
900
16th to endNight
26%17%25%26%3
960
Page generated at 2020-06-04 03:18:52. Version ac04

Copyright 2020 A. Danko


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