Shuttleview Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Shuttleview Observatory clear sky chart from 2005-11-05 to 2019-07-16.

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
59%
17810
32%
54360
23%
17766
69%
17766
44%
27546

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
57%
840
32%
2717
28%
836
67%
836
42%
1364
January16th to endNight
54%
896
34%
2912
26%
896
67%
896
43%
1429
February1st to 15thNight
48%
820
32%
2670
23%
818
62%
818
47%
1258
February16th to endNight
42%
736
39%
2130
21%
736
61%
736
47%
1064
March1st to 15thNight
46%
840
38%
2310
20%
840
62%
840
50%
1180
March16th to endNight
52%
896
35%
2464
18%
896
66%
896
52%
1247
April1st to 15thNight
44%
661
37%
2130
19%
661
66%
661
48%
966
April16th to endNight
42%
624
35%
2079
19%
624
65%
624
44%
944
May1st to 15thNight
51%
629
32%
2015
22%
629
64%
629
45%
970
May16th to endNight
58%
659
32%
1972
22%
657
69%
657
56%
901
June1st to 15thNight
68%
630
30%
1890
26%
630
71%
630
53%
890
June16th to endNight
73%
630
24%
1890
21%
630
75%
630
49%
920
July1st to 15thNight
72%
600
17%
1800
17%
600
73%
600
28%
1111
July16th to endNight
71%
615
12%
1746
11%
582
73%
582
26%
1110
August1st to 15thNight
72%
575
16%
1751
16%
572
72%
572
26%
1092
August16th to endNight
73%
621
21%
2070
23%
621
74%
621
26%
1280
September1st to 15thNight
72%
585
26%
1950
28%
585
73%
585
28%
1181
September16th to endNight
72%
755
34%
2163
24%
755
78%
755
51%
1110
October1st to 15thNight
64%
780
36%
2340
24%
780
73%
780
57%
1087
October16th to endNight
68%
832
41%
2496
27%
832
78%
832
59%
1133
November1st to 15thNight
66%
820
44%
2460
29%
820
77%
820
64%
1043
November16th to endNight
61%
865
40%
2598
30%
865
70%
865
50%
1254
December1st to 15thNight
53%
1005
34%
2895
21%
1005
64%
1005
46%
1475
December16th to endNight
47%
896
32%
2912
23%
896
59%
896
36%
1537

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
442442445%6%56%
54929
Night
331332345%7%60%
54564
TransparencyDay
27%47%17%27%16%
54624
Night
22%48%20%28%15%
54370
SeeingDay
8%12%23%27%19%8%
7480
Night
47%22%35%25%4
17815

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
25%2432335%7%60%
1881
16th to endDay
25%23312335%64%
2016
February1st to 15thDay
16%24412336%62%
1845
16th to endDay
17%2331335%7%59%
1911
March1st to 15thDay
26%1332446%7%57%
2310
16th to endDay
231232435%8%62%
2464
April1st to 15thDay
242232335%7%61%
2478
16th to endDay
3413323335%65%
2486
May1st to 15thDay
4315%434445%59%
2591
16th to endDay
4213423335%65%
2845
June1st to 15thDay
3213323346%64%
2730
16th to endDay
3213424445%61%
2730
July1st to 15thDay
8%5%27%7%5%6%6%7%8%35%
2730
16th to endDay
9%5%37%7%6%7%8%7%10%27%
2678
August1st to 15thDay
9%436%7%5%7%6%6%8%32%
2453
16th to endDay
8%436%6%46%6%6%7%40%
2484
September1st to 15thDay
10%436%6%36%5%5%6%40%
2340
16th to endDay
421442434462%
2124
October1st to 15thDay
331441333465%
1950
16th to endDay
3313312325%69%
2080
November1st to 15thDay
121221235%7%68%
2059
16th to endDay
1313223335%68%
1999
December1st to 15thDay
35%23324336%61%
1729
16th to endDay
27%35%41335%6%56%
2016
January1st to 15thNight
242432335%7%60%
2717
16th to endNight
1423424345%62%
2912
February1st to 15thNight
2414322347%63%
2667
16th to endNight
142421245%8%61%
2130
March1st to 15thNight
2423212347%65%
2310
16th to endNight
2313312345%68%
2464
April1st to 15thNight
121222435%7%65%
2130
16th to endNight
3312213335%68%
2079
May1st to 15thNight
3423322346%64%
2015
16th to endNight
2212212236%71%
1972
June1st to 15thNight
2213213346%67%
1890
16th to endNight
2213323447%63%
1890
July1st to 15thNight
5%326%5%36%8%7%11%38%
1890
16th to endNight
5%325%7%37%8%10%13%33%
1854
August1st to 15thNight
4425%7%36%6%8%11%38%
1760
16th to endNight
6%425%5%36%7%8%10%38%
2070
September1st to 15thNight
7%325%6%45%5%6%9%43%
1950
16th to endNight
422313345%66%
2163
October1st to 15thNight
3112212246%70%
2340
16th to endNight
2212213245%72%
2496
November1st to 15thNight
111213346%74%
2460
16th to endNight
2423212236%68%
2598
December1st to 15thNight
25%23322347%63%
2895
16th to endNight
27%25%42246%7%55%
2912

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
23%38%22%30%11%
1882
16th to endDay
23%25%19%34%14%
2016
February1st to 15thDay
22%36%24%24%18%
1845
16th to endDay
24%2319%34%15%
1911
March1st to 15thDay
24%35%17%33%15%
2310
16th to endDay
20%35%19%36%15%
2464
April1st to 15thDay
21%3420%32%16%
2478
16th to endDay
22%2318%34%18%
2486
May1st to 15thDay
26%3415%31%18%
2591
16th to endDay
22%35%12%32%23%
2848
June1st to 15thDay
21%3411%26%33%
2730
16th to endDay
24%45%11%24%29%
2730
July1st to 15thDay
43%7%12%14%10%10%
2591
16th to endDay
47%9%20%16%5%
2523
August1st to 15thDay
46%8%14%14%12%3
2438
16th to endDay
41%8%12%16%15%5%
2484
September1st to 15thDay
42%6%10%15%17%8%
2340
16th to endDay
25%45%16%28%20%
2124
October1st to 15thDay
23%26%16%30%21%
1950
16th to endDay
18%25%17%35%19%
2080
November1st to 15thDay
14%25%23%35%17%
2059
16th to endDay
19%2315%35%22%
1999
December1st to 15thDay
24%35%26%26%12%
1729
16th to endDay
28%39%21%28%7%
2016
January1st to 15thNight
23%46%21%32%10%
2717
16th to endNight
22%37%20%34%11%
2912
February1st to 15thNight
19%39%26%23%17%
2678
16th to endNight
19%35%24%31%14%
2130
March1st to 15thNight
18%35%20%37%14%
2310
16th to endNight
18%35%23%36%13%
2464
April1st to 15thNight
16%3426%33%15%
2130
16th to endNight
18%3418%36%18%
2079
May1st to 15thNight
21%36%16%36%15%
2016
16th to endNight
16%27%16%33%23%
1973
June1st to 15thNight
18%3413%26%33%
1890
16th to endNight
20%37%16%19%32%
1890
July1st to 15thNight
34%10%15%15%13%11%
1800
16th to endNight
35%11%29%18%4
1746
August1st to 15thNight
33%12%20%16%13%3
1751
16th to endNight
35%10%17%17%13%6%
2070
September1st to 15thNight
36%6%16%15%15%8%
1950
16th to endNight
19%46%18%29%20%
2163
October1st to 15thNight
16%28%22%28%21%
2340
16th to endNight
14%25%21%35%20%
2496
November1st to 15thNight
11%25%29%33%17%
2460
16th to endNight
19%2318%33%21%
2598
December1st to 15thNight
22%38%25%28%12%
2895
16th to endNight
27%49%24%25%8%
2912

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
8%11%34%28%11%5%
180
16th to endDay
314%29%24%21%6%
192
February1st to 15thDay
7%12%24%34%16%4
180
16th to endDay
7%30%31%18%9%3
232
March1st to 15thDay
10%19%34%23%11%1
390
16th to endDay
7%24%31%21%13%1
416
April1st to 15thDay
10%20%32%20%12%3
389
16th to endDay
13%21%34%17%9%3
378
May1st to 15thDay
9%16%32%22%14%4
408
16th to endDay
7%16%34%29%9%2
458
June1st to 15thDay
5%7%27%31%20%7%
435
16th to endDay
6%315%34%29%10%
435
July1st to 15thDay
10%45%34%30%13%
425
16th to endDay
13%2421%29%29%
392
August1st to 15thDay
12%35%31%28%18%
359
16th to endDay
8%29%33%29%16%
396
September1st to 15thDay
14%5%9%29%31%9%
375
16th to endDay
8%7%19%35%24%5%
336
October1st to 15thDay
6%8%30%25%21%8%
180
16th to endDay
45%21%34%23%9%
192
November1st to 15thDay
315%26%37%12%5%
180
16th to endDay
5%15%26%28%20%3
180
December1st to 15thDay
312%27%33%20%3
180
16th to endDay
8%16%29%30%13%2
192
January1st to 15thNight
48%24%38%19%4
840
16th to endNight
311%26%32%22%3
896
February1st to 15thNight
310%33%32%17%3
824
16th to endNight
313%38%34%9%
736
March1st to 15thNight
412%33%31%16%1
840
16th to endNight
310%29%39%15%1
896
April1st to 15thNight
215%35%34%12%
661
16th to endNight
413%34%31%14%
624
May1st to 15thNight
5%6%31%39%15%1
630
16th to endNight
4427%43%17%1
659
June1st to 15thNight
2418%50%21%1
630
16th to endNight
3113%45%34%2
630
July1st to 15thNight
7%1336%43%7%
600
16th to endNight
6%5%21%53%12%
615
August1st to 15thNight
6%2123%52%13%
575
16th to endNight
6%1428%49%9%
621
September1st to 15thNight
7%1434%45%6%
585
16th to endNight
5%213%36%34%6%
755
October1st to 15thNight
3324%41%22%4
780
16th to endNight
2320%37%28%6%
832
November1st to 15thNight
1425%36%25%5%
820
16th to endNight
410%19%32%26%7%
865
December1st to 15thNight
6%9%25%36%19%3
1005
16th to endNight
6%10%30%34%14%3
896
Page generated at 2019-07-17 06:53:05. Version ac04

Copyright 2019 A. Danko


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