Field of Dreams Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Field of Dreams Observatory clear sky chart from 2005-11-06 to 2024-01-16.

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
34%
23383
15%
74929
10%
23332
40%
23332
18%
53085

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 10thNight
12%
757
11%
2459
3%
757
20%
757
8%
1978
January11th to 20thNight
14%
744
8%
2417
3%
744
19%
744
8%
1985
January21st to endNight
17%
792
9%
2574
5%
792
22%
792
8%
2087
February1st to 10thNight
15%
720
9%
2340
4%
720
22%
720
10%
1867
February11th to 20thNight
14%
702
10%
2253
4%
700
22%
700
10%
1756
February21st to endNight
15%
592
12%
1776
3%
592
24%
592
11%
1390
March1st to 10thNight
21%
720
16%
1998
8%
720
28%
720
17%
1471
March11th to 20thNight
27%
720
18%
1980
10%
720
34%
720
20%
1409
March21st to endNight
25%
792
17%
2178
9%
792
32%
792
19%
1611
April1st to 10thNight
26%
720
14%
1920
5%
720
32%
720
20%
1373
April11th to 20thNight
30%
626
17%
1690
7%
626
36%
626
23%
1195
April21st to endNight
30%
540
18%
1620
7%
540
38%
540
23%
1091
May1st to 10thNight
37%
540
13%
1620
7%
540
42%
540
19%
1167
May11th to 20thNight
43%
531
16%
1592
11%
531
48%
531
23%
1085
May21st to endNight
56%
497
17%
1660
15%
497
61%
497
30%
1001
June1st to 10thNight
50%
360
16%
1440
19%
360
56%
360
23%
861
June11th to 20thNight
52%
360
18%
1440
21%
360
59%
360
23%
838
June21st to endNight
52%
360
18%
1440
20%
360
60%
360
24%
825
July1st to 10thNight
63%
477
15%
1527
15%
477
66%
477
29%
938
July11th to 20thNight
63%
522
18%
1566
16%
522
66%
522
37%
899
July21st to endNight
62%
591
17%
1672
14%
558
63%
558
28%
1071
August1st to 10thNight
65%
537
20%
1600
17%
534
66%
534
32%
958
August11th to 20thNight
64%
534
20%
1598
16%
534
66%
534
31%
985
August21st to endNight
59%
648
22%
1836
15%
648
62%
648
33%
1123
September1st to 10thNight
57%
720
24%
1850
15%
720
60%
720
34%
1186
September11th to 20thNight
65%
720
28%
1980
21%
720
68%
720
38%
1169
September21st to endNight
46%
720
22%
1980
16%
720
51%
720
28%
1282
October1st to 10thNight
46%
720
19%
2124
17%
720
50%
720
28%
1334
October11th to 20thNight
31%
720
16%
2160
10%
720
40%
720
20%
1498
October21st to endNight
28%
792
19%
2376
13%
792
36%
792
18%
1709
November1st to 10thNight
36%
740
22%
2360
15%
740
46%
740
25%
1506
November11th to 20thNight
23%
760
16%
2536
9%
760
32%
760
15%
1810
November21st to endNight
21%
760
13%
2660
8%
760
29%
760
12%
1968
December1st to 10thNight
16%
760
7%
2660
5%
760
20%
760
8%
2133
December11th to 20thNight
17%
759
8%
3259
4%
759
24%
759
7%
2536
December21st to endNight
14%
830
4%
4788
3%
817
20%
817
4%
3990

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
16%10%47%6%35%5%5%7%30%
74624
Night
16%11%47%6%35%45%6%32%
75179
TransparencyDay
53%5%11%19%10%1
74345
Night
52%5%11%19%11%2
74977
SeeingDay
21%13%28%21%12%5%
13520
Night
21%11%27%27%12%2
23396

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 10thDay
17%17%9%11%9%35%435%17%
1706
11th to 20thDay
18%20%8%11%9%33345%15%
1671
21st to endDay
17%19%9%12%8%4444414%
1782
February1st to 10thDay
20%17%6%11%9%4424420%
1620
11th to 20thDay
17%13%8%12%8%36%45%6%19%
1591
21st to endDay
20%14%5%9%7%35%35%6%23%
1480
March1st to 10thDay
18%12%6%8%6%3345%6%28%
1962
11th to 20thDay
18%13%5%8%6%33446%29%
1980
21st to endDay
22%11%6%8%6%34446%27%
2178
April1st to 10thDay
15%12%5%7%7%3445%8%32%
2039
11th to 20thDay
18%12%46%5%35%5%5%6%32%
2234
21st to endDay
22%10%36%6%33446%33%
2340
May1st to 10thDay
17%10%47%6%46%6%5%7%29%
2340
11th to 20thDay
20%7%37%6%35%5%6%7%31%
2301
21st to endDay
11%5%27%6%45%7%7%9%37%
2611
June1st to 10thDay
15%6%36%6%45%5%6%9%34%
2520
11th to 20thDay
14%7%36%7%45%5%6%9%35%
2520
21st to endDay
12%5%25%6%45%6%7%10%38%
2520
July1st to 10thDay
11%5%46%5%35%5%6%10%40%
2382
11th to 20thDay
12%6%36%6%35%6%6%9%38%
2340
21st to endDay
12%5%37%6%46%5%7%9%36%
2547
August1st to 10thDay
10%6%26%7%5%6%6%7%9%36%
2327
11th to 20thDay
11%6%36%7%46%7%7%10%33%
2303
21st to endDay
11%5%36%6%46%5%7%8%38%
2502
September1st to 10thDay
15%7%25%5%345%5%6%43%
2106
11th to 20thDay
12%6%35%5%35%5%6%9%41%
1980
21st to endDay
18%7%36%5%45%45%7%37%
1980
October1st to 10thDay
16%7%27%6%345%6%7%37%
1835
11th to 20thDay
19%10%36%6%35%5%5%6%33%
1800
21st to endDay
24%11%36%5%44446%28%
1980
November1st to 10thDay
11%8%47%6%45%45%6%39%
1713
11th to 20thDay
17%15%47%6%35%446%30%
1639
21st to endDay
17%16%6%9%6%35%45%5%23%
1520
December1st to 10thDay
21%17%8%10%7%3444417%
1520
11th to 20thDay
18%17%8%13%5%345%5%6%17%
1910
21st to endDay
25%24%8%11%6%3333411%
2845
January1st to 10thNight
18%17%7%11%7%445%4420%
2459
11th to 20thNight
19%17%6%12%8%35%44418%
2417
21st to endNight
17%17%9%11%8%45%44419%
2574
February1st to 10thNight
22%13%6%10%8%44446%20%
2340
11th to 20thNight
18%12%7%10%7%46%446%21%
2251
21st to endNight
20%14%6%9%6%35%45%424%
1776
March1st to 10thNight
17%11%5%8%6%3445%5%32%
1998
11th to 20thNight
19%11%5%5%5%25%45%7%34%
1980
21st to endNight
18%11%48%6%2444433%
2178
April1st to 10thNight
16%12%46%5%34446%34%
1920
11th to 20thNight
15%9%47%5%45%45%8%34%
1690
21st to endNight
16%8%46%435%5%6%8%35%
1620
May1st to 10thNight
19%9%36%6%46%5%5%6%32%
1620
11th to 20thNight
15%7%37%6%25%5%6%8%36%
1592
21st to endNight
9%5%25%5%35%5%6%12%43%
1659
June1st to 10thNight
9%6%36%7%36%5%5%7%44%
1440
11th to 20thNight
10%6%26%6%35%5%6%9%42%
1440
21st to endNight
10%5%36%5%347%7%9%43%
1440
July1st to 10thNight
8%435%6%35%5%6%8%46%
1572
11th to 20thNight
8%5%245%25%6%7%10%48%
1620
21st to endNight
10%426%5%46%6%7%9%40%
1771
August1st to 10thNight
8%5%35%5%35%6%6%9%46%
1611
11th to 20thNight
10%6%36%5%3446%8%46%
1598
21st to endNight
10%425%6%45%5%6%7%47%
1836
September1st to 10thNight
13%5%25%434447%48%
1850
11th to 20thNight
11%5%2443445%7%52%
1980
21st to endNight
15%6%45%5%3445%8%41%
1980
October1st to 10thNight
15%425%5%3445%8%44%
2124
11th to 20thNight
18%7%37%6%45%5%5%7%34%
2160
21st to endNight
25%8%26%5%345%5%6%32%
2376
November1st to 10thNight
15%9%25%435%35%6%42%
2360
11th to 20thNight
17%12%5%8%6%35%45%6%31%
2536
21st to endNight
19%15%5%7%5%35%446%27%
2660
December1st to 10thNight
21%16%6%11%7%35%435%19%
2660
11th to 20thNight
18%18%7%10%7%33445%21%
3285
21st to endNight
25%20%8%8%6%3444413%
4806

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 10thDay
71%49%11%4
1707
11th to 20thDay
73%312%10%3
1671
21st to endDay
74%38%11%31
1782
February1st to 10thDay
70%29%13%6%1
1620
11th to 20thDay
67%5%8%13%7%
1600
21st to endDay
63%410%15%7%1
1480
March1st to 10thDay
57%5%12%20%7%
1962
11th to 20thDay
57%5%9%18%10%1
1980
21st to endDay
61%38%17%10%2
2178
April1st to 10thDay
52%411%19%12%1
2039
11th to 20thDay
52%5%11%17%13%3
2234
21st to endDay
54%410%20%10%2
2340
May1st to 10thDay
55%5%11%18%10%2
2340
11th to 20thDay
52%6%12%16%12%2
2305
21st to endDay
40%7%15%24%12%2
2611
June1st to 10thDay
46%5%13%23%12%1
2520
11th to 20thDay
46%5%13%22%13%1
2520
21st to endDay
40%6%14%25%13%1
2520
July1st to 10thDay
41%6%12%24%14%3
2317
11th to 20thDay
41%6%12%25%15%1
2271
21st to endDay
41%7%14%23%14%1
2405
August1st to 10thDay
42%8%14%26%11%
2314
11th to 20thDay
44%7%14%24%9%2
2303
21st to endDay
42%7%13%23%13%3
2502
September1st to 10thDay
42%5%11%22%16%4
2106
11th to 20thDay
39%6%13%25%16%1
1980
21st to endDay
47%5%11%25%13%1
1980
October1st to 10thDay
46%5%11%22%15%1
1835
11th to 20thDay
52%412%21%10%1
1800
21st to endDay
58%411%17%10%1
1980
November1st to 10thDay
45%411%22%16%2
1713
11th to 20thDay
56%411%19%8%3
1639
21st to endDay
62%5%10%16%6%1
1520
December1st to 10thDay
71%49%12%4
1520
11th to 20thDay
68%49%15%4
1906
21st to endDay
79%210%7%2
2845
January1st to 10thNight
67%48%14%5%
2459
11th to 20thNight
70%410%13%31
2417
21st to endNight
69%39%14%41
2574
February1st to 10thNight
67%410%14%5%
2340
11th to 20thNight
64%49%16%7%1
2253
21st to endNight
64%48%14%9%2
1776
March1st to 10thNight
55%49%22%10%1
1998
11th to 20thNight
50%412%21%10%2
1980
21st to endNight
55%47%19%13%2
2178
April1st to 10thNight
51%411%19%13%2
1920
11th to 20thNight
49%412%16%15%3
1690
21st to endNight
46%5%12%19%15%2
1620
May1st to 10thNight
52%5%8%19%13%3
1620
11th to 20thNight
45%6%11%18%16%3
1593
21st to endNight
35%7%16%26%15%2
1660
June1st to 10thNight
39%6%12%25%16%2
1440
11th to 20thNight
38%6%14%24%17%2
1440
21st to endNight
37%7%14%23%19%1
1440
July1st to 10thNight
36%7%12%24%18%3
1527
11th to 20thNight
30%6%16%27%19%2
1566
21st to endNight
37%9%14%22%15%3
1672
August1st to 10thNight
34%6%12%30%17%1
1600
11th to 20thNight
36%6%16%26%14%2
1598
21st to endNight
35%6%12%26%17%4
1836
September1st to 10thNight
36%5%10%26%18%5%
1850
11th to 20thNight
31%5%14%27%21%2
1980
21st to endNight
42%313%23%18%1
1980
October1st to 10thNight
39%5%13%24%17%1
2124
11th to 20thNight
50%5%11%22%12%1
2160
21st to endNight
53%5%10%20%11%2
2376
November1st to 10thNight
42%411%24%15%3
2360
11th to 20thNight
55%410%19%9%3
2536
21st to endNight
59%412%18%5%1
2660
December1st to 10thNight
68%410%12%5%
2660
11th to 20thNight
66%411%15%3
3288
21st to endNight
75%411%9%2
4806

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 10thDay
30%25%31%11%4
270
11th to 20thDay
30%25%35%8%2
257
21st to endDay
26%31%32%8%3
264
February1st to 10thDay
34%20%37%9%
240
11th to 20thDay
30%32%28%10%
240
21st to endDay
31%28%34%7%
198
March1st to 10thDay
24%22%34%16%4
402
11th to 20thDay
29%17%34%14%6%1
420
21st to endDay
34%17%27%16%41
462
April1st to 10thDay
23%20%29%17%8%2
420
11th to 20thDay
28%14%28%16%10%4
412
21st to endDay
27%15%33%16%7%2
420
May1st to 10thDay
26%17%27%17%8%3
423
11th to 20thDay
24%11%30%23%8%4
447
21st to endDay
13%8%28%25%20%5%
485
June1st to 10thDay
16%7%31%29%12%4
450
11th to 20thDay
18%8%24%28%16%5%
450
21st to endDay
14%8%30%27%15%5%
450
July1st to 10thDay
14%418%26%25%13%
445
11th to 20thDay
12%6%24%30%19%8%
444
21st to endDay
12%327%27%21%9%
488
August1st to 10thDay
12%7%19%28%23%11%
446
11th to 20thDay
15%8%21%24%22%10%
439
21st to endDay
11%5%22%28%23%11%
495
September1st to 10thDay
15%7%22%24%22%11%
450
11th to 20thDay
10%418%32%24%12%
450
21st to endDay
22%10%24%23%13%8%
450
October1st to 10thDay
15%10%26%26%18%5%
450
11th to 20thDay
21%14%37%19%8%1
450
21st to endDay
33%14%30%18%5%
495
November1st to 10thDay
19%19%32%18%9%3
311
11th to 20thDay
30%20%27%17%5%1
237
21st to endDay
22%23%39%15%1
180
December1st to 10thDay
31%27%29%8%42
180
11th to 20thDay
28%20%37%12%2
180
21st to endDay
34%25%28%12%2
220
January1st to 10thNight
26%21%34%15%4
760
11th to 20thNight
30%18%33%16%4
744
21st to endNight
25%19%31%21%4
792
February1st to 10thNight
30%15%33%19%2
720
11th to 20thNight
27%17%38%17%2
703
21st to endNight
30%17%34%18%2
592
March1st to 10thNight
24%16%34%23%3
720
11th to 20thNight
25%16%29%23%6%1
720
21st to endNight
24%14%31%24%6%1
792
April1st to 10thNight
21%17%30%25%6%
720
11th to 20thNight
22%12%33%24%9%1
626
21st to endNight
19%10%35%28%7%
540
May1st to 10thNight
22%8%27%32%10%1
540
11th to 20thNight
20%6%24%37%11%2
531
21st to endNight
11%324%35%24%3
499
June1st to 10thNight
9%5%27%43%15%1
360
11th to 20thNight
10%426%44%16%1
360
21st to endNight
10%426%39%21%1
360
July1st to 10thNight
7%315%40%28%6%
477
11th to 20thNight
10%319%38%26%4
522
21st to endNight
12%215%40%28%2
591
August1st to 10thNight
9%413%42%30%2
537
11th to 20thNight
14%311%40%28%5%
534
21st to endNight
13%219%32%29%6%
648
September1st to 10thNight
15%5%18%31%27%5%
720
11th to 20thNight
13%313%36%30%5%
720
21st to endNight
17%8%23%27%20%4
720
October1st to 10thNight
17%7%25%30%18%3
720
11th to 20thNight
21%11%31%27%9%1
720
21st to endNight
29%10%29%26%6%
792
November1st to 10thNight
19%12%28%28%12%1
740
11th to 20thNight
24%17%31%20%7%1
760
21st to endNight
28%15%31%20%6%
760
December1st to 10thNight
31%18%29%18%4
760
11th to 20thNight
25%21%31%20%4
760
21st to endNight
28%17%33%20%2
836
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