Stillwater
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Stillwater clear sky chart from 2005-11-05 to

2017-09-12
.

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
46%
15751
28%
46859
18%
15705
56%
15705
38%
25923

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
36%
899
32%
2327
13%
895
48%
895
41%
1309
January16th to endNight
36%
960
35%
2496
14%
960
49%
960
44%
1399
February1st to 15thNight
32%
815
24%
2223
9%
811
42%
811
33%
1344
February16th to endNight
31%
632
30%
1894
11%
632
46%
632
34%
1065
March1st to 15thNight
35%
556
26%
1996
15%
556
49%
556
28%
1110
March16th to endNight
31%
576
20%
2112
15%
576
41%
576
25%
1207
April1st to 15thNight
29%
539
24%
1950
14%
539
47%
539
29%
1052
April16th to endNight
33%
540
25%
1638
16%
540
48%
540
32%
959
May1st to 15thNight
36%
540
24%
1620
15%
540
50%
540
33%
961
May16th to endNight
49%
563
25%
1684
21%
561
58%
561
37%
968
June1st to 15thNight
57%
540
21%
1620
16%
540
64%
540
42%
865
June16th to endNight
61%
540
26%
1620
19%
540
68%
540
50%
802
July1st to 15thNight
70%
510
20%
1530
19%
510
73%
510
41%
841
July16th to endNight
83%
564
32%
1594
38%
531
84%
531
56%
751
August1st to 15thNight
78%
539
25%
1610
29%
536
80%
536
43%
868
August16th to endNight
76%
573
28%
1800
31%
573
79%
573
43%
926
September1st to 15thNight
61%
530
25%
1943
28%
530
66%
530
33%
1028
September16th to endNight
60%
492
34%
1815
31%
492
69%
492
37%
900
October1st to 15thNight
48%
577
31%
1897
24%
577
56%
577
35%
1026
October16th to endNight
46%
704
35%
2112
17%
704
60%
704
48%
1043
November1st to 15thNight
44%
802
31%
2202
14%
802
55%
802
45%
1192
November16th to endNight
37%
900
30%
2340
14%
900
47%
900
39%
1399
December1st to 15thNight
37%
900
28%
2340
12%
900
47%
900
36%
1396
December16th to endNight
36%
960
30%
2496
13%
960
48%
960
36%
1512

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
9%42442445%7%51%
47799
Night
8%413323347%56%
47055
Cloud CoverDay
10%424423446%51%
47797
Night
9%413323347%56%
47055
TransparencyDay
32%5%10%25%21%5%
47497
Night
28%410%25%23%7%
46860
SeeingDay
10%6%24%31%22%4
5750
Night
11%7%30%34%14%1
15752

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
9%5%13413345%56%
1611
16th to endDay
9%5%23222326%57%
1728
February1st to 15thDay
10%7%34423335%50%
1648
16th to endDay
10%6%24323345%53%
1580
March1st to 15thDay
13%5%33324446%48%
1962
16th to endDay
15%7%24323336%45%
2112
April1st to 15thDay
10%4234245%5%6%49%
1997
16th to endDay
13%6%25%413447%44%
2319
May1st to 15thDay
16%5%2442345%5%46%
2331
16th to endDay
11%4244445%6%7%43%
2430
June1st to 15thDay
6%3245%3446%9%49%
2340
16th to endDay
5%213325%5%6%8%54%
2340
July1st to 15thDay
7%3245%35%5%6%10%45%
2340
16th to endDay
43133246%7%9%52%
2466
August1st to 15thDay
43144345%7%9%49%
2340
16th to endDay
5%3145%35%6%6%8%49%
2399
September1st to 15thDay
13%414324448%47%
1936
16th to endDay
8%41332435%6%56%
1815
October1st to 15thDay
11%5%2331223458%
1722
16th to endDay
6%323322335%63%
1760
November1st to 15thDay
7%33213436%63%
1655
16th to endDay
11%4232223361%
1620
December1st to 15thDay
13%6%24313335%51%
1620
16th to endDay
13%6%36%32323449%
1728
January1st to 15thNight
9%313312346%59%
2327
16th to endNight
8%412313345%61%
2496
February1st to 15thNight
11%6%23323335%53%
2213
16th to endNight
9%5%24323246%55%
1894
March1st to 15thNight
9%5%35%42335%6%51%
1996
16th to endNight
14%5%23323346%50%
2112
April1st to 15thNight
11%423324347%53%
1950
16th to endNight
12%423422347%51%
1638
May1st to 15thNight
10%42441345%6%51%
1619
16th to endNight
8%32332435%10%51%
1683
June1st to 15thNight
5%31232445%7%58%
1620
16th to endNight
31123145%6%9%60%
1620
July1st to 15thNight
5%21342448%11%50%
1620
16th to endNight
41122133411%64%
1702
August1st to 15thNight
31135%35%6%7%8%54%
1620
16th to endNight
22134345%5%9%55%
1800
September1st to 15thNight
9%424323345%55%
1943
16th to endNight
7%413313446%58%
1815
October1st to 15thNight
10%413423335%57%
1897
16th to endNight
7%21321232468%
2112
November1st to 15thNight
5%413322235%63%
2202
16th to endNight
12%423312225%58%
2340
December1st to 15thNight
12%413313445%55%
2340
16th to endNight
12%6%24212336%53%
2496

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
9%5%13413345%56%
1611
16th to endDay
10%5%23322335%58%
1728
February1st to 15thDay
11%7%34413325%51%
1648
16th to endDay
11%6%33323235%53%
1580
March1st to 15thDay
13%5%33323446%48%
1962
16th to endDay
15%7%24413345%46%
2110
April1st to 15thDay
10%42442445%6%49%
1997
16th to endDay
14%6%25%413447%44%
2319
May1st to 15thDay
17%5%2342335%5%46%
2331
16th to endDay
11%5%244345%6%7%43%
2430
June1st to 15thDay
6%4245%3445%10%49%
2340
16th to endDay
6%2133346%6%8%54%
2340
July1st to 15thDay
7%3245%35%46%10%46%
2340
16th to endDay
5%3134245%6%10%53%
2466
August1st to 15thDay
43145%245%7%8%50%
2340
16th to endDay
6%3145%35%5%6%8%50%
2399
September1st to 15thDay
13%41433445%7%48%
1936
16th to endDay
8%41332335%6%56%
1815
October1st to 15thDay
11%423212235%58%
1722
16th to endDay
7%413323335%63%
1760
November1st to 15thDay
7%312212436%63%
1655
16th to endDay
11%5%132223461%
1620
December1st to 15thDay
13%5%25%322335%51%
1620
16th to endDay
13%7%25%42223449%
1728
January1st to 15thNight
9%313212346%59%
2327
16th to endNight
8%322213345%61%
2496
February1st to 15thNight
12%6%23323335%53%
2213
16th to endNight
9%5%24323346%55%
1894
March1st to 15thNight
10%5%35%32335%6%51%
1996
16th to endNight
14%5%24323346%50%
2112
April1st to 15thNight
12%323323346%53%
1950
16th to endNight
13%42432225%7%51%
1638
May1st to 15thNight
11%423323346%52%
1619
16th to endNight
9%31232445%9%52%
1683
June1st to 15thNight
5%212324448%58%
1620
16th to endNight
311231346%9%60%
1620
July1st to 15thNight
5%21333447%11%50%
1620
16th to endNight
41112122411%65%
1702
August1st to 15thNight
3113425%6%7%8%54%
1620
16th to endNight
32134345%5%9%56%
1800
September1st to 15thNight
9%424323336%55%
1943
16th to endNight
8%413313446%58%
1815
October1st to 15thNight
10%413323335%57%
1897
16th to endNight
7%3321132468%
2112
November1st to 15thNight
6%413322245%63%
2202
16th to endNight
13%413322225%58%
2340
December1st to 15thNight
12%5%12223345%55%
2340
16th to endNight
13%6%23212337%53%
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
29%39%28%25%3
1612
16th to endDay
29%38%30%23%4
1728
February1st to 15thDay
37%39%25%18%5%
1649
16th to endDay
34%26%30%20%5%
1580
March1st to 15thDay
37%48%22%19%7%
1962
16th to endDay
41%411%21%18%3
2112
April1st to 15thDay
34%6%11%25%17%4
1997
16th to endDay
39%5%9%22%19%3
2319
May1st to 15thDay
39%5%10%20%20%3
2331
16th to endDay
37%7%12%25%15%1
2434
June1st to 15thDay
30%6%15%26%17%4
2340
16th to endDay
25%7%13%22%25%5%
2340
July1st to 15thDay
32%6%13%28%16%2
2201
16th to endDay
23%7%12%30%22%2
2311
August1st to 15thDay
27%7%16%23%18%7%
2326
16th to endDay
28%7%12%27%18%5%
2399
September1st to 15thDay
33%6%10%23%17%8%
1936
16th to endDay
27%5%8%25%27%5%
1815
October1st to 15thDay
29%310%24%24%7%
1722
16th to endDay
24%39%25%29%8%
1760
November1st to 15thDay
22%310%26%27%9%
1655
16th to endDay
27%27%26%27%8%
1620
December1st to 15thDay
36%48%30%19%1
1620
16th to endDay
39%28%22%21%5%
1728
January1st to 15thNight
26%38%29%27%5%
2327
16th to endNight
25%38%29%25%8%
2496
February1st to 15thNight
34%38%27%19%6%
2223
16th to endNight
30%38%27%22%7%
1894
March1st to 15thNight
33%49%20%22%9%
1996
16th to endNight
35%5%11%25%18%3
2112
April1st to 15thNight
30%5%10%23%21%8%
1950
16th to endNight
33%410%24%20%7%
1638
May1st to 15thNight
32%5%11%20%22%6%
1620
16th to endNight
28%7%14%29%17%2
1685
June1st to 15thNight
23%6%14%32%18%5%
1620
16th to endNight
19%5%14%29%24%7%
1620
July1st to 15thNight
24%7%13%27%23%2
1530
16th to endNight
16%411%33%29%5%
1594
August1st to 15thNight
23%7%15%25%19%8%
1610
16th to endNight
23%6%13%27%22%7%
1800
September1st to 15thNight
30%49%23%19%11%
1943
16th to endNight
25%46%26%27%8%
1815
October1st to 15thNight
30%411%19%23%11%
1897
16th to endNight
20%36%26%31%10%
2112
November1st to 15thNight
23%38%22%29%11%
2202
16th to endNight
30%26%22%28%8%
2340
December1st to 15thNight
30%410%26%23%3
2340
16th to endNight
32%310%23%23%7%
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
17%11%35%30%5%
90
16th to endDay
10%17%43%22%41
96
February1st to 15thDay
6%16%50%23%3
90
16th to endDay
12%16%40%29%1
81
March1st to 15thDay
21%21%42%13%2
90
16th to endDay
12%17%35%23%9%1
96
April1st to 15thDay
12%16%35%30%6%
116
16th to endDay
20%13%35%20%8%
429
May1st to 15thDay
14%12%34%25%10%1
468
16th to endDay
17%7%33%25%13%2
517
June1st to 15thDay
7%426%40%17%3
495
16th to endDay
5%123%38%25%6%
495
July1st to 15thDay
7%115%40%30%4
475
16th to endDay
5%435%42%11%
515
August1st to 15thDay
6%9%38%38%6%
493
16th to endDay
7%111%32%40%7%
439
September1st to 15thDay
4310%33%41%7%
123
16th to endDay
6%121%28%26%15%
90
October1st to 15thDay
8%7%26%23%24%8%
90
16th to endDay
6%234%41%10%5%
96
November1st to 15thDay
12%330%26%22%5%
90
16th to endDay
25%20%31%15%5%2
90
December1st to 15thDay
13%5%53%21%5%1
90
16th to endDay
16%12%38%28%4
96
January1st to 15thNight
11%12%36%31%7%
900
16th to endNight
10%10%40%32%7%
960
February1st to 15thNight
14%12%36%31%5%
815
16th to endNight
12%13%39%29%4
632
March1st to 15thNight
11%10%38%35%4
556
16th to endNight
17%11%36%28%5%
576
April1st to 15thNight
14%13%39%26%5%
539
16th to endNight
12%11%39%27%8%
540
May1st to 15thNight
13%7%39%27%10%1
540
16th to endNight
10%432%33%16%2
563
June1st to 15thNight
7%326%42%19%
540
16th to endNight
2128%45%20%1
540
July1st to 15thNight
6%17%45%29%1
510
16th to endNight
46%46%38%2
564
August1st to 15thNight
37%50%35%2
539
16th to endNight
312%38%42%3
573
September1st to 15thNight
11%117%40%26%2
530
16th to endNight
10%221%38%21%6%
492
October1st to 15thNight
12%430%29%20%2
577
16th to endNight
9%6%34%33%14%1
704
November1st to 15thNight
8%8%34%33%13%1
802
16th to endNight
14%10%35%29%9%
900
December1st to 15thNight
15%11%33%31%7%
900
16th to endNight
16%10%33%32%7%
960
Page generated at 2017-09-13 06:39:09. Version ac04

Copyright 2017 A. Danko


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