Scopeville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Scopeville clear sky chart from 2005-11-05 to 2017-09-17.

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
43%
15851
24%
47073
15%
15805
51%
15805
33%
27676

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
30%
899
24%
2327
9%
895
41%
895
33%
1446
January16th to endNight
30%
960
28%
2496
10%
960
42%
960
35%
1518
February1st to 15thNight
25%
880
18%
2288
7%
876
32%
876
26%
1528
February16th to endNight
28%
649
26%
1911
10%
649
40%
649
30%
1154
March1st to 15thNight
33%
540
23%
1980
13%
540
45%
540
24%
1171
March16th to endNight
28%
576
17%
2112
11%
576
38%
576
21%
1347
April1st to 15thNight
35%
539
22%
1863
15%
539
48%
539
27%
1065
April16th to endNight
33%
540
22%
1715
15%
540
44%
540
25%
1075
May1st to 15thNight
38%
539
21%
1620
16%
539
47%
539
29%
1012
May16th to endNight
46%
563
20%
1685
16%
561
52%
561
31%
1013
June1st to 15thNight
61%
540
20%
1500
13%
540
65%
540
43%
842
June16th to endNight
62%
540
24%
1552
17%
540
67%
540
50%
803
July1st to 15thNight
70%
510
19%
1530
17%
510
72%
510
42%
831
July16th to endNight
74%
564
24%
1594
26%
531
77%
531
45%
837
August1st to 15thNight
76%
539
25%
1610
30%
536
77%
536
44%
850
August16th to endNight
73%
573
27%
1815
31%
573
76%
573
41%
960
September1st to 15thNight
64%
540
25%
1866
28%
540
67%
540
34%
1019
September16th to endNight
63%
498
30%
1837
27%
498
70%
498
35%
939
October1st to 15thNight
48%
647
30%
1967
22%
647
53%
647
35%
1112
October16th to endNight
37%
704
30%
2112
15%
704
50%
704
38%
1148
November1st to 15thNight
40%
751
31%
2151
15%
751
53%
751
38%
1191
November16th to endNight
32%
900
26%
2451
11%
900
43%
900
33%
1489
December1st to 15thNight
29%
900
20%
2520
8%
900
39%
900
29%
1607
December16th to endNight
29%
960
25%
2571
9%
960
41%
960
27%
1719

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%5%25%42445%7%45%
47677
Night
11%5%24423346%50%
47268
TransparencyDay
38%413%26%15%2
47377
Night
34%312%27%18%3
47073
SeeingDay
13%6%23%29%21%5%
5875
Night
13%7%29%33%14%1
15853

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
11%5%25%5%25%34450%
1611
16th to endDay
12%7%34422347%45%
1728
February1st to 15thDay
12%8%46%5%33336%42%
1575
16th to endDay
13%7%45%5%23347%42%
1572
March1st to 15thDay
13%7%36%5%35%45%6%37%
1980
16th to endDay
22%9%35%323335%36%
2110
April1st to 15thDay
15%7%245%24446%42%
2085
16th to endDay
20%6%36%6%24445%35%
2243
May1st to 15thDay
19%7%26%5%2435%6%35%
2331
16th to endDay
16%6%25%6%35%35%7%36%
2430
June1st to 15thDay
9%425%425%5%6%8%44%
2451
16th to endDay
6%2133245%6%10%52%
2399
July1st to 15thDay
8%325%425%5%6%9%46%
2340
16th to endDay
7%3245%35%47%10%45%
2466
August1st to 15thDay
7%4245%25%47%10%46%
2340
16th to endDay
7%314425%5%6%8%48%
2386
September1st to 15thDay
13%5%24333347%49%
2091
16th to endDay
9%42342445%6%52%
1828
October1st to 15thDay
13%6%23323435%52%
1650
16th to endDay
12%424423345%53%
1760
November1st to 15thDay
9%413323346%55%
1704
16th to endDay
16%423312236%51%
1507
December1st to 15thDay
15%6%45%423346%43%
1440
16th to endDay
15%7%46%324346%40%
1650
January1st to 15thNight
10%5%2442435%5%51%
2327
16th to endNight
7%6%25%424446%51%
2496
February1st to 15thNight
11%8%45%5%2445%6%42%
2278
16th to endNight
11%7%25%423345%48%
1911
March1st to 15thNight
12%7%345%24345%47%
1980
16th to endNight
18%7%35%324346%40%
2112
April1st to 15thNight
11%5%24424446%48%
1863
16th to endNight
16%426%5%23346%43%
1715
May1st to 15thNight
14%5%35%423346%46%
1619
16th to endNight
11%42442435%9%46%
1683
June1st to 15thNight
5%214425%6%6%10%51%
1500
16th to endNight
4223235%5%10%58%
1552
July1st to 15thNight
7%31333446%9%52%
1620
16th to endNight
5%2135%2446%8%53%
1702
August1st to 15thNight
42135%3345%9%55%
1620
16th to endNight
6%314423446%57%
1815
September1st to 15thNight
11%413424346%52%
1866
16th to endNight
7%31433445%7%54%
1837
October1st to 15thNight
14%413322235%54%
1967
16th to endNight
9%41342234459%
2112
November1st to 15thNight
10%323223236%58%
2151
16th to endNight
14%6%23312235%53%
2451
December1st to 15thNight
16%6%35%31235%7%44%
2520
16th to endNight
14%9%35%323346%42%
2571

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
37%312%27%17%1
1612
16th to endDay
39%314%27%14%1
1728
February1st to 15thDay
44%314%26%9%1
1576
16th to endDay
43%311%25%13%2
1572
March1st to 15thDay
46%411%21%13%2
1980
16th to endDay
51%313%20%9%1
2112
April1st to 15thDay
43%311%24%15%
2085
16th to endDay
50%311%22%12%
2243
May1st to 15thDay
48%410%22%12%
2331
16th to endDay
46%415%22%10%
2434
June1st to 15thDay
34%6%14%26%16%1
2451
16th to endDay
25%5%16%32%18%2
2399
July1st to 15thDay
33%5%15%29%13%2
2201
16th to endDay
30%5%16%31%14%2
2311
August1st to 15thDay
31%5%16%26%18%1
2326
16th to endDay
30%6%13%25%17%6%
2386
September1st to 15thDay
35%311%25%17%5%
2091
16th to endDay
30%411%31%19%3
1828
October1st to 15thDay
35%310%25%20%5%
1650
16th to endDay
34%210%28%19%5%
1760
November1st to 15thDay
29%410%28%21%6%
1704
16th to endDay
36%19%29%21%
1507
December1st to 15thDay
42%312%29%12%
1440
16th to endDay
45%312%23%11%3
1650
January1st to 15thNight
35%312%27%19%1
2327
16th to endNight
33%213%30%16%3
2496
February1st to 15thNight
43%312%25%13%1
2288
16th to endNight
37%211%27%18%2
1911
March1st to 15thNight
39%310%23%16%5%
1980
16th to endNight
46%311%23%13%1
2112
April1st to 15thNight
36%39%25%21%3
1863
16th to endNight
42%210%25%17%1
1715
May1st to 15thNight
40%312%25%16%1
1620
16th to endNight
35%418%25%13%1
1685
June1st to 15thNight
26%5%18%31%15%2
1500
16th to endNight
20%415%33%22%2
1552
July1st to 15thNight
27%414%33%15%4
1530
16th to endNight
25%314%31%22%2
1594
August1st to 15thNight
24%415%33%17%3
1610
16th to endNight
26%410%27%24%6%
1815
September1st to 15thNight
32%311%26%19%7%
1866
16th to endNight
27%410%28%25%3
1837
October1st to 15thNight
33%28%24%24%7%
1967
16th to endNight
28%28%30%23%5%
2112
November1st to 15thNight
29%110%25%24%8%
2151
16th to endNight
35%27%29%21%3
2451
December1st to 15thNight
40%214%27%14%
2520
16th to endNight
43%311%24%12%4
2571

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
31%10%35%17%5%
90
16th to endDay
18%16%37%20%5%1
96
February1st to 15thDay
8%23%45%16%5%
90
16th to endDay
16%23%35%18%41
81
March1st to 15thDay
20%18%43%13%4
90
16th to endDay
25%17%27%21%8%
96
April1st to 15thDay
15%13%37%23%10%
204
16th to endDay
23%8%36%21%7%1
353
May1st to 15thDay
20%7%32%26%11%2
468
16th to endDay
17%8%28%28%13%3
517
June1st to 15thDay
9%322%34%23%6%
495
16th to endDay
8%227%35%22%3
495
July1st to 15thDay
11%214%37%27%5%
475
16th to endDay
7%18%30%44%8%
515
August1st to 15thDay
6%19%39%33%10%
493
16th to endDay
8%114%29%37%8%
426
September1st to 15thDay
12%212%32%32%8%
246
16th to endDay
7%221%37%19%11%
93
October1st to 15thDay
7%430%32%13%12%
90
16th to endDay
11%8%38%31%9%1
96
November1st to 15thDay
8%12%20%30%18%10%
90
16th to endDay
34%14%30%14%5%1
90
December1st to 15thDay
14%14%44%16%6%3
90
16th to endDay
22%20%33%19%3
96
January1st to 15thNight
13%14%37%28%6%
900
16th to endNight
11%12%40%29%5%
960
February1st to 15thNight
15%13%39%27%3
880
16th to endNight
15%10%40%29%3
649
March1st to 15thNight
16%8%35%32%5%
540
16th to endNight
19%9%38%27%4
576
April1st to 15thNight
15%12%32%31%7%
539
16th to endNight
19%7%33%30%8%
540
May1st to 15thNight
15%6%31%32%13%
540
16th to endNight
13%428%33%17%2
563
June1st to 15thNight
6%221%43%23%1
540
16th to endNight
5%125%46%20%1
540
July1st to 15thNight
7%14%45%29%2
510
16th to endNight
6%17%39%42%2
564
August1st to 15thNight
6%15%46%36%3
539
16th to endNight
7%19%41%36%3
573
September1st to 15thNight
12%313%39%26%5%
540
16th to endNight
8%217%36%29%5%
498
October1st to 15thNight
16%424%31%20%2
647
16th to endNight
13%7%37%29%11%1
704
November1st to 15thNight
12%10%32%31%12%1
751
16th to endNight
18%11%33%28%7%
900
December1st to 15thNight
20%11%35%27%5%
900
16th to endNight
19%9%35%28%5%
960
Page generated at 2017-09-18 07:38:28. Version ac04

Copyright 2017 A. Danko


Scopeville Clear Sky Chart | Charts Home