Pilot Mound
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pilot Mound clear sky chart from 2005-11-06 to 2024-09-29.

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
33%
25818
12%
94650
7%
25606
40%
25606
17%
63258

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
25%
936
9%
4704
6%
926
31%
926
8%
3467
January11th to 20thNight
19%
943
7%
4499
4%
930
24%
930
7%
3566
January21st to endNight
20%
1039
9%
4723
4%
1023
26%
1023
7%
3537
February1st to 10thNight
25%
950
11%
2613
3%
950
31%
950
16%
1975
February11th to 20thNight
31%
925
14%
2404
6%
924
36%
924
22%
1720
February21st to endNight
33%
635
17%
1891
7%
635
42%
635
20%
1338
March1st to 10thNight
28%
756
15%
3706
5%
744
35%
744
11%
2464
March11th to 20thNight
31%
580
17%
3457
12%
564
45%
564
13%
1998
March21st to endNight
33%
618
9%
3709
11%
605
40%
605
9%
2526
April1st to 10thNight
38%
570
19%
1867
15%
570
49%
570
25%
1149
April11th to 20thNight
34%
563
14%
1689
10%
563
40%
563
19%
1204
April21st to endNight
38%
570
12%
1710
9%
570
41%
570
21%
1168
May1st to 10thNight
37%
569
14%
2793
6%
559
41%
559
16%
1791
May11th to 20thNight
41%
553
12%
2221
6%
541
44%
541
19%
1374
May21st to endNight
37%
609
9%
2380
4%
593
42%
593
21%
1414
June1st to 10thNight
43%
570
7%
1330
3%
570
46%
570
34%
893
June11th to 20thNight
38%
570
7%
1330
3%
570
41%
570
32%
914
June21st to endNight
51%
570
8%
1330
4%
570
55%
570
37%
875
July1st to 10thNight
57%
540
6%
2095
6%
535
60%
535
32%
1153
July11th to 20thNight
54%
537
11%
1823
6%
533
57%
533
34%
1003
July21st to endNight
62%
610
11%
2408
8%
569
65%
569
32%
1236
August1st to 10thNight
58%
556
18%
2287
9%
545
62%
545
29%
1253
August11th to 20thNight
55%
551
16%
2574
13%
544
62%
544
25%
1344
August21st to endNight
49%
620
16%
2864
19%
605
58%
605
24%
1556
September1st to 10thNight
49%
570
21%
1862
18%
570
58%
570
36%
1018
September11th to 20thNight
44%
570
19%
2090
17%
570
52%
570
27%
1188
September21st to endNight
37%
567
21%
2079
17%
567
47%
567
23%
1249
October1st to 10thNight
32%
603
18%
2043
12%
603
39%
603
19%
1351
October11th to 20thNight
33%
818
19%
2258
9%
818
39%
818
24%
1533
October21st to endNight
26%
990
14%
2574
4%
990
32%
990
20%
1863
November1st to 10thNight
24%
925
15%
2462
4%
925
32%
925
19%
1794
November11th to 20thNight
23%
950
12%
2660
5%
950
29%
950
15%
2038
November21st to endNight
20%
950
11%
2831
4%
950
28%
950
14%
2117
December1st to 10thNight
24%
950
9%
2850
4%
950
30%
950
14%
2192
December11th to 20thNight
17%
950
8%
3483
2%
949
24%
949
9%
2676
December21st to endNight
20%
1035
8%
5051
5%
1026
28%
1026
8%
3321

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
11%9%38%6%5%5%46%8%35%
101478
Night
9%10%410%6%5%5%46%7%35%
96932
TransparencyDay
46%7%16%23%8%
101206
Night
46%7%14%23%9%1
96794
SeeingDay
15%10%33%27%12%3
16105
Night
14%9%34%31%11%1
25968

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 10thDay
5%17%6%12%8%7%7%6%6%6%19%
2218
11th to 20thDay
38%5%15%13%11%13%8%9%5%11%
2416
21st to endDay
7%12%5%15%8%6%6%35%6%25%
2794
February1st to 10thDay
9%13%5%13%8%7%6%5%7%6%20%
1566
11th to 20thDay
5%12%410%9%7%9%6%8%8%22%
1673
21st to endDay
5%12%7%12%7%6%8%5%6%8%25%
1570
March1st to 10thDay
10%13%49%8%7%5%5%6%7%27%
3130
11th to 20thDay
7%12%5%11%12%6%5%47%8%24%
3466
21st to endDay
9%12%7%13%9%5%5%36%7%25%
3838
April1st to 10thDay
9%13%5%8%5%5%5%46%8%33%
2313
11th to 20thDay
13%12%49%6%5%5%46%7%30%
2439
21st to endDay
16%9%48%6%5%446%6%34%
2470
May1st to 10thDay
19%11%37%44336%7%33%
4137
11th to 20thDay
18%8%37%5%5%5%45%7%32%
4641
21st to endDay
17%9%28%5%45%45%7%35%
5173
June1st to 10thDay
13%7%26%5%46%47%8%37%
2850
11th to 20thDay
15%6%27%5%5%5%46%8%36%
2850
21st to endDay
12%7%26%5%5%5%5%8%8%37%
2850
July1st to 10thDay
9%425%5%5%6%5%8%11%41%
4750
11th to 20thDay
7%425%445%46%9%50%
4750
21st to endDay
5%425%44447%10%51%
4868
August1st to 10thDay
9%6%26%5%4446%9%45%
4357
11th to 20thDay
12%5%25%33436%9%48%
4041
21st to endDay
10%6%26%43435%8%49%
4532
September1st to 10thDay
12%5%25%44335%6%52%
2314
11th to 20thDay
15%7%26%444447%43%
2090
21st to endDay
14%7%25%43446%7%43%
2068
October1st to 10thDay
16%13%45%43435%5%37%
1898
11th to 20thDay
13%13%37%44446%7%35%
1697
21st to endDay
15%14%49%5%45%45%8%28%
1782
November1st to 10thDay
14%15%411%5%4345%5%29%
1615
11th to 20thDay
7%14%7%15%8%45%445%26%
1520
21st to endDay
9%16%412%9%5%445%5%27%
1347
December1st to 10thDay
7%13%6%16%9%7%7%5%5%7%18%
1330
11th to 20thDay
10%13%8%15%7%7%6%5%6%6%17%
1683
21st to endDay
8%10%412%7%45%5%7%7%31%
2442
January1st to 10thNight
6%14%7%14%7%6%6%5%7%7%21%
4737
11th to 20thNight
5%10%5%15%10%9%10%7%7%6%16%
4554
21st to endNight
7%14%6%16%9%5%5%45%5%24%
4873
February1st to 10thNight
8%12%5%11%8%6%7%7%7%7%23%
2613
11th to 20thNight
6%9%310%7%6%7%6%8%8%30%
2403
21st to endNight
6%11%410%8%5%7%37%8%31%
1891
March1st to 10thNight
8%10%410%9%7%5%36%7%30%
3734
11th to 20thNight
6%11%49%6%45%36%7%38%
3494
21st to endNight
7%10%5%14%8%6%435%5%31%
3792
April1st to 10thNight
7%8%37%6%45%5%7%8%41%
1867
11th to 20thNight
13%12%48%5%46%5%5%7%33%
1689
21st to endNight
13%8%37%45%5%46%7%36%
1710
May1st to 10thNight
20%9%37%44445%6%35%
2829
11th to 20thNight
14%9%36%44435%6%41%
2249
21st to endNight
17%7%35%43335%6%43%
2414
June1st to 10thNight
10%5%26%5%45%45%9%45%
1330
11th to 20thNight
12%6%26%45%437%6%43%
1330
21st to endNight
10%425%34446%12%45%
1330
July1st to 10thNight
9%31433446%10%53%
2220
11th to 20thNight
6%31434345%8%59%
2220
21st to endNight
35%1435%5%5%8%10%51%
2691
August1st to 10thNight
6%426%44436%7%54%
2581
11th to 20thNight
7%415%44446%10%51%
2798
21st to endNight
10%5%26%334447%53%
3135
September1st to 10thNight
9%5%15%33435%8%54%
1862
11th to 20thNight
12%5%25%33346%7%49%
2090
21st to endNight
14%7%36%5%4435%6%45%
2079
October1st to 10thNight
14%10%38%45%325%7%39%
2043
11th to 20thNight
15%10%36%345%45%7%38%
2258
21st to endNight
11%12%410%6%5%445%7%34%
2574
November1st to 10thNight
11%13%49%5%5%5%46%7%31%
2462
11th to 20thNight
9%15%6%13%6%5%445%6%27%
2660
21st to endNight
9%14%5%12%6%5%6%35%6%29%
2831
December1st to 10thNight
6%12%5%13%10%7%6%6%6%6%23%
2850
11th to 20thNight
9%14%6%15%9%6%5%45%7%20%
3514
21st to endNight
9%11%411%7%6%436%5%31%
5225

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
61%7%13%15%4
2219
11th to 20thDay
68%7%10%11%4
2416
21st to endDay
60%5%8%21%6%
2794
February1st to 10thDay
60%6%10%18%6%1
1566
11th to 20thDay
54%7%12%19%8%1
1682
21st to endDay
56%7%11%17%8%
1570
March1st to 10thDay
54%7%14%18%8%
3130
11th to 20thDay
54%9%14%17%5%
3466
21st to endDay
56%7%12%19%6%
3838
April1st to 10thDay
47%6%14%24%8%1
2313
11th to 20thDay
52%7%13%18%10%1
2442
21st to endDay
50%6%16%19%7%1
2470
May1st to 10thDay
48%5%15%21%9%1
4137
11th to 20thDay
49%7%12%23%8%1
4645
21st to endDay
47%7%12%24%8%
5173
June1st to 10thDay
41%9%18%22%10%1
2850
11th to 20thDay
45%9%14%22%9%1
2850
21st to endDay
41%9%20%24%6%1
2850
July1st to 10thDay
33%11%25%25%5%
4676
11th to 20thDay
28%8%21%36%7%
4669
21st to endDay
26%9%24%32%8%
4714
August1st to 10thDay
35%8%18%26%12%1
4342
11th to 20thDay
31%7%19%34%8%
4080
21st to endDay
33%6%20%32%9%
4531
September1st to 10thDay
32%6%18%31%12%1
2314
11th to 20thDay
41%6%18%25%10%1
2090
21st to endDay
39%7%15%30%8%1
2068
October1st to 10thDay
47%6%13%24%9%
1898
11th to 20thDay
47%5%15%24%9%
1697
21st to endDay
54%7%16%17%5%
1782
November1st to 10thDay
56%6%11%17%8%1
1615
11th to 20thDay
59%6%15%13%6%1
1520
21st to endDay
59%7%11%17%6%
1347
December1st to 10thDay
63%8%12%12%5%
1330
11th to 20thDay
64%6%10%14%5%1
1680
21st to endDay
49%5%12%18%15%
2442
January1st to 10thNight
58%8%12%17%6%
4737
11th to 20thNight
64%8%11%13%5%
4554
21st to endNight
62%48%20%5%
4873
February1st to 10thNight
56%6%12%16%9%1
2613
11th to 20thNight
48%7%14%19%12%1
2404
21st to endNight
49%6%13%21%10%1
1891
March1st to 10thNight
51%7%14%20%8%
3734
11th to 20thNight
43%6%17%23%11%1
3494
21st to endNight
53%7%11%21%8%
3792
April1st to 10thNight
39%6%13%24%16%2
1867
11th to 20thNight
50%7%11%18%13%1
1689
21st to endNight
45%8%14%21%11%1
1710
May1st to 10thNight
47%6%12%25%10%1
2829
11th to 20thNight
41%8%14%24%10%3
2250
21st to endNight
40%6%13%31%9%
2414
June1st to 10thNight
35%8%19%28%9%2
1330
11th to 20thNight
38%7%16%25%12%1
1330
21st to endNight
32%8%21%32%6%1
1330
July1st to 10thNight
25%10%28%28%7%1
2185
11th to 20thNight
23%7%18%41%11%1
2178
21st to endNight
24%7%24%33%10%1
2607
August1st to 10thNight
28%6%17%33%15%1
2573
11th to 20thNight
27%8%21%33%11%1
2825
21st to endNight
31%6%17%34%11%1
3135
September1st to 10thNight
28%6%15%35%15%2
1862
11th to 20thNight
33%7%18%29%13%1
2090
21st to endNight
40%5%12%30%11%2
2079
October1st to 10thNight
46%6%13%25%9%
2043
11th to 20thNight
45%5%13%27%11%
2258
21st to endNight
50%6%15%23%6%1
2574
November1st to 10thNight
50%7%14%19%8%2
2462
11th to 20thNight
57%7%13%15%7%1
2660
21st to endNight
55%7%14%17%6%
2831
December1st to 10thNight
57%8%14%15%6%
2850
11th to 20thNight
62%6%15%12%41
3516
21st to endNight
52%6%10%18%13%1
5225

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
10%11%35%32%10%2
270
11th to 20thDay
11%12%43%23%10%1
270
21st to endDay
15%11%39%22%10%2
297
February1st to 10thDay
14%12%41%26%6%1
270
11th to 20thDay
9%15%38%31%7%
270
21st to endDay
7%10%42%31%9%1
225
March1st to 10thDay
14%15%34%30%5%1
270
11th to 20thDay
14%15%30%29%10%2
270
21st to endDay
16%10%33%26%12%3
309
April1st to 10thDay
14%17%34%25%9%1
493
11th to 20thDay
20%13%33%23%10%1
640
21st to endDay
18%12%36%22%11%1
650
May1st to 10thDay
16%14%29%27%12%2
653
11th to 20thDay
20%8%34%23%12%3
675
21st to endDay
19%10%26%30%13%2
734
June1st to 10thDay
15%11%31%24%13%5%
680
11th to 20thDay
14%13%36%24%11%3
680
21st to endDay
13%8%30%32%14%3
680
July1st to 10thDay
8%6%28%30%20%7%
671
11th to 20thDay
13%7%30%27%18%5%
668
21st to endDay
5%6%27%36%19%7%
739
August1st to 10thDay
9%7%26%33%19%7%
676
11th to 20thDay
14%5%24%30%19%8%
665
21st to endDay
14%6%27%31%19%3
748
September1st to 10thDay
13%8%37%26%13%3
524
11th to 20thDay
20%9%31%31%9%1
300
21st to endDay
20%11%34%24%10%1
294
October1st to 10thDay
21%15%27%24%11%1
270
11th to 20thDay
20%10%39%24%6%2
270
21st to endDay
25%12%38%18%6%2
297
November1st to 10thDay
24%12%35%22%7%
270
11th to 20thDay
13%18%39%25%6%
270
21st to endDay
16%18%41%22%3
270
December1st to 10thDay
13%12%39%26%9%2
270
11th to 20thDay
16%16%40%23%41
270
21st to endDay
13%9%41%26%7%3
297
January1st to 10thNight
11%11%38%29%9%1
950
11th to 20thNight
15%11%40%27%7%
950
21st to endNight
13%13%38%28%7%1
1045
February1st to 10thNight
12%11%37%30%9%1
950
11th to 20thNight
10%10%37%32%9%2
929
21st to endNight
11%8%36%32%11%2
635
March1st to 10thNight
14%10%33%27%12%3
760
11th to 20thNight
11%9%40%28%11%1
584
21st to endNight
15%9%31%30%12%2
627
April1st to 10thNight
10%9%36%34%9%2
570
11th to 20thNight
19%8%31%33%8%1
563
21st to endNight
15%9%30%32%11%1
570
May1st to 10thNight
17%8%31%31%12%1
570
11th to 20thNight
16%9%28%33%13%1
561
21st to endNight
18%7%30%33%12%
617
June1st to 10thNight
14%7%31%35%12%2
570
11th to 20thNight
14%7%35%30%14%1
570
21st to endNight
11%5%27%40%16%1
570
July1st to 10thNight
6%326%42%21%1
555
11th to 20thNight
7%5%28%41%18%1
552
21st to endNight
5%425%46%17%3
624
August1st to 10thNight
8%223%46%19%1
567
11th to 20thNight
9%6%23%39%20%3
564
21st to endNight
11%429%37%17%1
627
September1st to 10thNight
11%432%35%16%3
570
11th to 20thNight
14%7%30%37%11%
570
21st to endNight
17%8%33%30%11%1
567
October1st to 10thNight
19%10%32%29%9%
603
11th to 20thNight
20%11%29%30%9%
818
21st to endNight
17%12%37%25%8%1
990
November1st to 10thNight
17%12%38%25%8%1
925
11th to 20thNight
15%12%39%23%9%2
950
21st to endNight
16%15%39%24%5%1
950
December1st to 10thNight
11%11%38%30%8%2
950
11th to 20thNight
16%12%36%27%7%2
950
21st to endNight
19%7%36%28%9%1
1045
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