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 2018-03-11.

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%
16806
19%
49154
11%
16759
46%
16759
27%
31396

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%
975
15%
2658
6%
970
39%
970
25%
1796
January16th to endNight
26%
1040
17%
2704
6%
1040
34%
1040
22%
1939
February1st to 15thNight
25%
955
12%
2483
4%
951
30%
951
20%
1830
February16th to endNight
29%
799
20%
2165
7%
799
38%
799
27%
1432
March1st to 15thNight
35%
576
21%
2104
14%
576
45%
576
24%
1255
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%
540
18%
1707
11%
540
43%
540
21%
1159
May1st to 15thNight
37%
540
17%
1581
10%
540
44%
540
26%
1025
May16th to endNight
44%
563
18%
1498
8%
561
50%
561
29%
990
June1st to 15thNight
55%
540
15%
1440
6%
540
58%
540
33%
921
June16th to endNight
51%
540
19%
1440
9%
540
55%
540
42%
848
July1st to 15thNight
68%
510
17%
1360
9%
510
70%
510
48%
761
July16th to endNight
73%
564
24%
1540
18%
531
76%
531
47%
812
August1st to 15thNight
68%
539
21%
1610
21%
536
71%
536
38%
912
August16th to endNight
63%
573
22%
1815
24%
573
68%
573
34%
1035
September1st to 15thNight
60%
540
27%
1800
26%
540
67%
540
37%
962
September16th to endNight
51%
570
27%
1992
21%
570
61%
570
34%
1061
October1st to 15thNight
37%
720
24%
2160
14%
720
46%
720
31%
1300
October16th to endNight
35%
768
24%
2304
12%
768
45%
768
28%
1405
November1st to 15thNight
36%
849
23%
2506
13%
849
45%
849
31%
1497
November16th to endNight
30%
975
19%
2730
8%
975
39%
975
28%
1738
December1st to 15thNight
24%
975
13%
2730
4%
975
32%
975
19%
1959
December16th to endNight
25%
1040
16%
2912
6%
1040
34%
1040
17%
2151

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%
49476
Night
11%7%35%424446%44%
49334
Cloud CoverDay
13%7%36%5%3445%7%38%
49485
Night
11%7%35%424446%44%
49338
TransparencyDay
43%6%14%22%12%1
49174
Night
39%5%13%24%14%2
49154
SeeingDay
14%7%28%29%15%3
6557
Night
15%8%31%31%12%
16806

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%11%46%8%46%5%5%6%32%
1607
16th to endDay
11%10%6%10%7%35%5%5%7%27%
1872
February1st to 15thDay
11%12%5%8%5%35%446%31%
1710
16th to endDay
14%8%38%5%35%445%36%
1604
March1st to 15thDay
13%9%37%6%35%447%33%
2084
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%
2251
May1st to 15thDay
18%7%345%35%46%7%32%
2370
16th to endDay
16%5%35%5%35%45%7%36%
2617
June1st to 15thDay
13%6%25%5%25%46%7%40%
2520
16th to endDay
7%425%5%35%5%7%9%43%
2520
July1st to 15thDay
6%4245%2346%10%48%
2520
16th to endDay
6%424435%5%6%10%47%
2520
August1st to 15thDay
7%4246%45%5%6%8%43%
2340
16th to endDay
11%5%246%2445%7%43%
2387
September1st to 15thDay
10%42342345%6%51%
2160
16th to endDay
11%4245%2445%6%47%
1953
October1st to 15thDay
16%5%35%423235%46%
1800
16th to endDay
15%7%35%5%24446%42%
1920
November1st to 15thDay
10%5%345%2345%6%47%
1680
16th to endDay
15%7%34335%447%40%
1560
December1st to 15thDay
15%10%48%5%35%447%30%
1560
16th to endDay
16%12%5%9%7%35%346%24%
1664
January1st to 15thNight
10%8%35%7%35%35%7%39%
2658
16th to endNight
11%11%5%7%5%24446%36%
2704
February1st to 15thNight
11%11%49%5%34446%32%
2480
16th to endNight
11%7%45%434446%43%
2165
March1st to 15thNight
13%7%35%423346%46%
2092
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%
1707
May1st to 15thNight
15%5%2432446%8%41%
1581
16th to endNight
11%5%35%5%3445%7%43%
1496
June1st to 15thNight
8%4245%35%45%9%46%
1440
16th to endNight
5%41442446%9%52%
1440
July1st to 15thNight
4212315%5%6%9%58%
1440
16th to endNight
3113335%47%9%55%
1647
August1st to 15thNight
5%42342445%8%54%
1620
16th to endNight
8%425%434345%54%
1815
September1st to 15thNight
9%414323345%57%
1800
16th to endNight
9%41342335%6%55%
1992
October1st to 15thNight
13%5%24422435%50%
2160
16th to endNight
13%7%13323336%49%
2304
November1st to 15thNight
11%6%24323347%49%
2506
16th to endNight
13%7%244135%45%45%
2730
December1st to 15thNight
13%11%47%5%3445%6%33%
2730
16th to endNight
16%10%5%8%6%2335%5%31%
2912

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%
1607
16th to endDay
11%10%6%10%7%35%5%5%7%26%
1872
February1st to 15thDay
11%11%5%8%5%35%446%31%
1710
16th to endDay
13%8%37%5%35%5%45%36%
1604
March1st to 15thDay
13%9%37%6%35%447%33%
2095
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%
2251
May1st to 15thDay
18%7%345%25%46%7%32%
2370
16th to endDay
16%5%36%5%35%45%7%36%
2617
June1st to 15thDay
13%6%25%5%25%46%7%40%
2520
16th to endDay
7%425%5%35%5%7%9%43%
2520
July1st to 15thDay
6%42442346%10%48%
2520
16th to endDay
6%314435%6%6%10%47%
2520
August1st to 15thDay
7%425%6%345%6%9%43%
2340
16th to endDay
11%5%245%3445%7%43%
2387
September1st to 15thDay
10%41433345%6%51%
2160
16th to endDay
11%4245%2446%6%47%
1953
October1st to 15thDay
16%5%35%423235%46%
1800
16th to endDay
15%7%25%5%23446%42%
1920
November1st to 15thDay
10%5%345%1445%6%47%
1680
16th to endDay
15%7%34335%447%39%
1560
December1st to 15thDay
15%10%49%5%35%447%31%
1560
16th to endDay
16%12%5%8%8%35%346%24%
1664
January1st to 15thNight
10%8%35%6%35%36%7%38%
2658
16th to endNight
11%11%5%8%5%34446%36%
2704
February1st to 15thNight
11%11%49%5%34446%33%
2473
16th to endNight
11%7%45%5%24346%43%
2165
March1st to 15thNight
13%7%25%423346%46%
2104
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%15%5%2333440%
1707
May1st to 15thNight
15%5%24335%46%8%41%
1580
16th to endNight
11%435%5%3445%7%43%
1496
June1st to 15thNight
8%4245%35%449%46%
1440
16th to endNight
5%31442446%9%52%
1440
July1st to 15thNight
32123145%6%9%57%
1440
16th to endNight
3113325%47%9%55%
1647
August1st to 15thNight
5%423424448%54%
1620
16th to endNight
8%425%434345%54%
1815
September1st to 15thNight
9%413323345%57%
1800
16th to endNight
9%41342335%6%55%
1992
October1st to 15thNight
13%5%24413435%50%
2160
16th to endNight
13%7%24323336%49%
2304
November1st to 15thNight
11%6%24323447%49%
2506
16th to endNight
13%7%25%423445%45%
2730
December1st to 15thNight
13%11%47%5%3445%6%33%
2730
16th to endNight
16%10%5%8%6%2435%5%31%
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
48%6%14%19%10%
1608
16th to endDay
55%6%14%16%6%
1872
February1st to 15thDay
53%414%20%6%
1711
16th to endDay
49%5%14%17%10%2
1604
March1st to 15thDay
50%415%19%8%1
2095
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%
2251
May1st to 15thDay
49%6%14%21%8%
2370
16th to endDay
46%6%13%18%12%1
2621
June1st to 15thDay
40%6%15%20%15%
2520
16th to endDay
33%7%14%26%15%1
2520
July1st to 15thDay
31%7%16%28%13%3
2371
16th to endDay
29%7%16%27%16%1
2364
August1st to 15thDay
34%7%16%25%14%
2326
16th to endDay
38%5%12%24%15%2
2387
September1st to 15thDay
31%6%13%27%19%2
2160
16th to endDay
35%5%12%30%15%
1953
October1st to 15thDay
41%49%24%19%1
1800
16th to endDay
42%5%11%24%14%1
1920
November1st to 15thDay
35%5%13%24%19%1
1680
16th to endDay
44%416%24%10%
1560
December1st to 15thDay
52%5%16%16%7%1
1560
16th to endDay
60%412%14%6%
1664
January1st to 15thNight
43%417%19%14%
2658
16th to endNight
48%5%15%21%8%
2704
February1st to 15thNight
51%413%19%8%1
2483
16th to endNight
41%413%24%14%1
2165
March1st to 15thNight
38%413%28%13%1
2104
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
1707
May1st to 15thNight
39%7%16%22%13%1
1581
16th to endNight
38%7%12%23%15%2
1498
June1st to 15thNight
34%7%16%24%14%2
1440
16th to endNight
27%6%13%26%22%4
1440
July1st to 15thNight
21%7%18%32%15%4
1360
16th to endNight
20%6%17%32%20%1
1540
August1st to 15thNight
28%6%14%30%17%2
1610
16th to endNight
31%5%11%25%19%6%
1815
September1st to 15thNight
30%310%29%22%3
1800
16th to endNight
29%411%32%19%2
1992
October1st to 15thNight
36%39%25%21%3
2160
16th to endNight
36%5%12%24%18%2
2304
November1st to 15thNight
35%413%26%18%3
2506
16th to endNight
39%415%28%11%1
2730
December1st to 15thNight
50%5%13%20%8%
2730
16th to endNight
54%413%16%9%
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
19%7%42%24%41
135
16th to endDay
17%6%40%30%31
144
February1st to 15thDay
14%21%36%22%5%
135
16th to endDay
25%9%40%17%7%
120
March1st to 15thDay
19%12%44%16%5%
121
16th to endDay
32%9%34%20%3
96
April1st to 15thDay
24%9%33%22%10%
264
16th to endDay
30%10%24%22%8%2
361
May1st to 15thDay
22%9%34%20%10%1
468
16th to endDay
17%9%28%27%13%2
517
June1st to 15thDay
11%6%26%32%19%4
495
16th to endDay
7%5%31%37%13%4
495
July1st to 15thDay
6%323%34%22%9%
475
16th to endDay
6%119%40%27%4
515
August1st to 15thDay
8%217%36%28%5%
493
16th to endDay
14%316%30%26%7%
427
September1st to 15thDay
9%322%33%22%9%
315
16th to endDay
8%8%24%42%12%3
153
October1st to 15thDay
17%6%39%22%10%3
135
16th to endDay
17%9%38%26%9%
144
November1st to 15thDay
7%8%38%30%10%4
135
16th to endDay
26%15%36%17%3
135
December1st to 15thDay
16%17%40%18%7%
135
16th to endDay
24%16%38%15%4
144
January1st to 15thNight
14%11%35%28%8%1
975
16th to endNight
15%10%36%30%5%
1040
February1st to 15thNight
17%10%36%29%5%
955
16th to endNight
14%10%40%26%6%1
799
March1st to 15thNight
17%9%33%26%11%
576
16th to endNight
20%11%36%22%8%
576
April1st to 15thNight
17%10%35%31%4
539
16th to endNight
22%9%32%26%8%1
540
May1st to 15thNight
16%9%31%31%10%
540
16th to endNight
13%5%30%35%13%
563
June1st to 15thNight
11%325%43%15%
540
16th to endNight
7%331%42%15%
540
July1st to 15thNight
5%20%44%27%1
510
16th to endNight
3114%50%27%1
564
August1st to 15thNight
6%214%47%27%2
539
16th to endNight
9%217%40%27%2
573
September1st to 15thNight
13%218%36%24%4
540
16th to endNight
11%428%33%18%2
570
October1st to 15thNight
16%7%33%26%13%
720
16th to endNight
17%9%33%29%9%
768
November1st to 15thNight
14%10%36%29%10%
849
16th to endNight
16%12%38%23%9%
975
December1st to 15thNight
19%12%36%26%5%
975
16th to endNight
21%9%34%27%6%
1040
Page generated at 2018-03-12 12:28:09. Version ac04

Copyright 2018 A. Danko


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