Ames
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Ames clear sky chart from 2005-11-05 to 2017-04-30.

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
38%
15602
19%
45692
10%
15555
46%
15555
27%
29337

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
31%
900
15%
2453
6%
895
38%
895
25%
1658
January16th to endNight
25%
960
16%
2496
6%
960
33%
960
21%
1806
February1st to 15thNight
25%
880
12%
2288
4%
876
30%
876
20%
1684
February16th to endNight
29%
738
20%
2000
7%
738
39%
738
27%
1324
March1st to 15thNight
35%
543
21%
1983
14%
543
46%
543
24%
1181
March16th to endNight
25%
576
12%
2112
6%
576
34%
576
16%
1450
April1st to 15thNight
30%
539
17%
1803
13%
539
39%
539
22%
1158
April16th to endNight
32%
537
18%
1698
11%
537
43%
537
22%
1150
May1st to 15thNight
35%
495
17%
1449
10%
495
42%
495
24%
963
May16th to endNight
44%
515
17%
1370
8%
513
51%
513
29%
904
June1st to 15thNight
53%
495
15%
1320
7%
495
56%
495
31%
864
June16th to endNight
52%
495
18%
1320
9%
495
55%
495
42%
775
July1st to 15thNight
67%
465
18%
1240
10%
465
69%
465
47%
700
July16th to endNight
72%
522
23%
1418
17%
489
75%
489
47%
754
August1st to 15thNight
67%
494
22%
1475
22%
491
70%
491
37%
842
August16th to endNight
63%
525
21%
1663
22%
525
67%
525
34%
952
September1st to 15thNight
60%
495
27%
1650
26%
495
67%
495
35%
897
September16th to endNight
51%
522
25%
1826
19%
522
61%
522
34%
977
October1st to 15thNight
39%
660
26%
1980
15%
660
47%
660
32%
1178
October16th to endNight
35%
704
21%
2112
10%
704
44%
704
27%
1305
November1st to 15thNight
37%
782
24%
2308
13%
782
47%
782
33%
1349
November16th to endNight
30%
900
17%
2520
8%
900
38%
900
27%
1637
December1st to 15thNight
23%
900
13%
2520
4%
900
32%
900
18%
1833
December16th to endNight
25%
960
15%
2688
5%
960
34%
960
17%
1996

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
13%7%36%5%3445%7%38%
46039
Night
12%7%35%424446%44%
45872
Cloud CoverDay
13%7%36%5%3445%7%38%
46048
Night
12%7%35%424446%43%
45876
TransparencyDay
44%6%14%22%11%1
45737
Night
40%5%13%24%14%2
45692
SeeingDay
15%7%27%29%16%3
5366
Night
15%8%31%31%12%
15602

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
8%10%36%7%46%5%5%6%32%
1483
16th to endDay
11%11%6%9%7%35%5%5%6%26%
1728
February1st to 15thDay
11%12%5%8%6%35%446%31%
1575
16th to endDay
13%8%38%5%35%445%36%
1482
March1st to 15thDay
13%9%37%6%35%447%33%
1969
16th to endDay
18%11%47%5%33445%30%
2112
April1st to 15thDay
18%8%35%434446%35%
2145
16th to endDay
23%8%36%5%24446%30%
2239
May1st to 15thDay
18%8%35%5%35%5%6%7%30%
2172
16th to endDay
16%5%45%5%35%45%7%36%
2393
June1st to 15thDay
14%6%26%5%25%46%7%37%
2310
16th to endDay
7%425%5%345%7%9%43%
2310
July1st to 15thDay
6%5%25%5%2346%10%46%
2310
16th to endDay
6%424435%6%6%10%45%
2334
August1st to 15thDay
7%4246%345%6%8%42%
2145
16th to endDay
11%5%245%2445%7%44%
2187
September1st to 15thDay
11%42443345%6%49%
1980
16th to endDay
11%4245%1446%6%48%
1791
October1st to 15thDay
15%435%423235%48%
1650
16th to endDay
16%7%25%5%24446%41%
1760
November1st to 15thDay
10%5%2442345%7%48%
1548
16th to endDay
16%8%34325%447%38%
1440
December1st to 15thDay
16%10%49%5%35%446%29%
1440
16th to endDay
16%13%5%9%7%35%346%24%
1536
January1st to 15thNight
11%8%35%6%35%35%7%39%
2453
16th to endNight
11%11%5%7%5%24446%35%
2496
February1st to 15thNight
11%11%49%6%34446%32%
2285
16th to endNight
11%7%45%434446%43%
2000
March1st to 15thNight
13%7%35%423347%46%
1971
16th to endNight
17%9%46%6%2435%7%32%
2112
April1st to 15thNight
14%7%25%6%23446%41%
1803
16th to endNight
19%7%25%5%2433440%
1698
May1st to 15thNight
16%5%24435%46%8%38%
1449
16th to endNight
11%435%5%345%5%7%43%
1368
June1st to 15thNight
9%5%25%5%35%45%9%43%
1320
16th to endNight
6%41442445%9%53%
1320
July1st to 15thNight
42123145%6%9%57%
1320
16th to endNight
3113325%48%9%55%
1525
August1st to 15thNight
6%42342445%7%54%
1485
16th to endNight
8%5%25%424345%53%
1663
September1st to 15thNight
10%414323346%56%
1650
16th to endNight
9%41342335%7%54%
1826
October1st to 15thNight
12%5%2441343452%
1980
16th to endNight
14%8%23332336%48%
2112
November1st to 15thNight
10%6%23323347%50%
2308
16th to endNight
14%7%35%4135%45%44%
2520
December1st to 15thNight
14%11%5%7%5%3445%6%31%
2520
16th to endNight
17%10%48%6%2335%5%31%
2688

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
8%10%46%7%5%6%5%5%6%32%
1483
16th to endDay
11%11%6%10%7%345%5%7%26%
1728
February1st to 15thDay
11%12%5%8%6%34446%31%
1575
16th to endDay
12%8%38%5%35%445%36%
1482
March1st to 15thDay
13%9%37%6%35%447%33%
1980
16th to endDay
18%11%48%5%2445%5%30%
2110
April1st to 15thDay
18%8%35%5%3445%6%35%
2145
16th to endDay
23%9%36%5%24446%30%
2239
May1st to 15thDay
18%8%35%5%25%46%8%30%
2172
16th to endDay
16%5%46%5%35%45%7%36%
2393
June1st to 15thDay
14%6%26%6%25%46%7%37%
2310
16th to endDay
7%425%5%345%6%9%43%
2310
July1st to 15thDay
6%5%25%5%2346%10%46%
2310
16th to endDay
6%424435%6%6%10%45%
2334
August1st to 15thDay
7%5%25%7%345%6%9%42%
2145
16th to endDay
11%5%245%2445%7%44%
2187
September1st to 15thDay
11%4243335%47%49%
1980
16th to endDay
11%4245%1446%6%48%
1791
October1st to 15thDay
14%435%423235%47%
1650
16th to endDay
16%7%25%5%23446%41%
1760
November1st to 15thDay
10%5%245%2445%7%48%
1548
16th to endDay
16%8%34334447%38%
1440
December1st to 15thDay
16%11%49%5%35%446%29%
1440
16th to endDay
16%13%6%9%8%35%346%23%
1536
January1st to 15thNight
11%8%35%6%35%35%7%39%
2453
16th to endNight
11%11%5%7%5%34446%35%
2496
February1st to 15thNight
11%11%49%6%34447%32%
2278
16th to endNight
11%7%45%5%34346%43%
2000
March1st to 15thNight
13%7%25%423347%46%
1983
16th to endNight
17%9%36%5%2435%6%33%
2112
April1st to 15thNight
14%7%25%5%23447%41%
1803
16th to endNight
19%8%26%5%2443440%
1698
May1st to 15thNight
16%5%24435%46%8%38%
1448
16th to endNight
11%435%5%345%5%7%43%
1368
June1st to 15thNight
9%5%25%5%35%449%43%
1320
16th to endNight
6%32432445%9%53%
1320
July1st to 15thNight
42123145%6%9%57%
1320
16th to endNight
4113425%47%9%55%
1525
August1st to 15thNight
6%423424448%54%
1485
16th to endNight
8%5%25%433345%53%
1663
September1st to 15thNight
10%424323345%56%
1650
16th to endNight
9%41342335%7%54%
1826
October1st to 15thNight
12%5%2441343452%
1980
16th to endNight
14%7%24322336%48%
2112
November1st to 15thNight
10%6%24323447%50%
2308
16th to endNight
14%7%25%4145%45%44%
2520
December1st to 15thNight
14%12%5%7%5%3445%6%31%
2520
16th to endNight
17%10%48%6%2435%5%31%
2688

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
48%6%14%19%10%
1484
16th to endDay
56%6%14%16%5%
1728
February1st to 15thDay
53%413%21%6%
1576
16th to endDay
48%5%15%17%10%1
1482
March1st to 15thDay
50%5%16%19%8%
1980
16th to endDay
54%414%18%6%1
2112
April1st to 15thDay
49%5%11%25%8%
2145
16th to endDay
54%5%11%19%8%
2239
May1st to 15thDay
51%6%14%19%7%
2172
16th to endDay
46%6%13%19%12%1
2397
June1st to 15thDay
43%7%16%19%12%
2310
16th to endDay
33%7%14%27%15%1
2310
July1st to 15thDay
33%7%16%26%12%3
2161
16th to endDay
31%8%16%26%15%1
2178
August1st to 15thDay
35%7%16%25%14%1
2131
16th to endDay
37%5%12%24%16%3
2187
September1st to 15thDay
34%6%12%25%19%2
1980
16th to endDay
34%5%12%30%15%
1791
October1st to 15thDay
39%49%24%20%1
1650
16th to endDay
43%5%12%24%13%
1760
November1st to 15thDay
34%413%25%20%1
1548
16th to endDay
46%416%23%8%
1440
December1st to 15thDay
55%5%15%16%6%
1440
16th to endDay
61%412%13%6%
1536
January1st to 15thNight
44%417%19%14%
2453
16th to endNight
49%5%15%20%8%
2496
February1st to 15thNight
51%413%20%8%
2288
16th to endNight
40%5%13%24%14%1
2000
March1st to 15thNight
38%5%13%27%13%1
1983
16th to endNight
51%415%19%7%1
2112
April1st to 15thNight
43%410%26%13%1
1803
16th to endNight
47%412%20%12%2
1698
May1st to 15thNight
41%7%16%21%11%1
1449
16th to endNight
38%7%12%24%14%2
1370
June1st to 15thNight
36%7%17%23%13%2
1320
16th to endNight
27%5%14%26%21%3
1320
July1st to 15thNight
22%7%18%32%14%4
1240
16th to endNight
21%6%17%31%20%1
1418
August1st to 15thNight
29%5%14%29%17%2
1475
16th to endNight
32%5%11%24%19%6%
1663
September1st to 15thNight
31%310%27%23%4
1650
16th to endNight
29%411%31%20%2
1826
October1st to 15thNight
35%39%25%22%3
1980
16th to endNight
37%5%13%24%16%2
2112
November1st to 15thNight
33%313%26%19%3
2308
16th to endNight
41%415%26%11%
2520
December1st to 15thNight
52%5%13%20%8%
2520
16th to endNight
54%413%16%9%
2688

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
22%8%41%23%22
90
16th to endDay
19%6%40%30%21
96
February1st to 15thDay
12%25%31%24%6%
90
16th to endDay
23%7%39%18%9%1
81
March1st to 15thDay
17%15%42%18%41
90
16th to endDay
32%9%34%20%3
96
April1st to 15thDay
24%9%33%22%10%
264
16th to endDay
29%10%25%22%8%2
357
May1st to 15thDay
23%11%35%17%9%2
393
16th to endDay
16%8%27%30%13%2
437
June1st to 15thDay
12%8%27%31%15%3
420
16th to endDay
7%429%38%15%5%
420
July1st to 15thDay
8%424%33%21%9%
400
16th to endDay
6%220%40%26%4
445
August1st to 15thDay
8%117%36%30%4
418
16th to endDay
14%316%32%28%5%
355
September1st to 15thDay
10%323%32%21%8%
255
16th to endDay
5%10%25%38%14%5%
107
October1st to 15thDay
7%8%36%28%12%5%
90
16th to endDay
16%8%35%30%9%
96
November1st to 15thDay
45%34%34%15%5%
90
16th to endDay
34%14%34%14%2
90
December1st to 15thDay
21%18%32%17%10%
90
16th to endDay
30%15%36%13%4
96
January1st to 15thNight
15%11%35%28%8%1
900
16th to endNight
16%11%36%29%5%
960
February1st to 15thNight
17%10%36%28%6%
880
16th to endNight
13%10%40%26%6%1
738
March1st to 15thNight
17%9%33%26%12%
543
16th to endNight
20%11%36%22%8%
576
April1st to 15thNight
17%10%35%31%4
539
16th to endNight
21%9%32%27%8%1
537
May1st to 15thNight
17%9%31%31%8%
495
16th to endNight
13%5%30%36%14%
515
June1st to 15thNight
12%425%44%12%
495
16th to endNight
7%230%43%15%
495
July1st to 15thNight
5%20%44%27%1
465
16th to endNight
3115%50%27%1
522
August1st to 15thNight
6%213%47%27%2
494
16th to endNight
9%216%41%26%2
525
September1st to 15thNight
13%218%36%24%4
495
16th to endNight
11%5%28%32%19%2
522
October1st to 15thNight
15%6%34%27%14%
660
16th to endNight
18%9%33%28%10%
704
November1st to 15thNight
13%10%36%29%10%
782
16th to endNight
17%12%36%23%9%
900
December1st to 15thNight
20%11%36%26%5%
900
16th to endNight
21%9%33%27%6%
960
Page generated at 2017-04-30 19:40:05. Version ac04

Copyright 2017 A. Danko


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