Pioneer Scout Reservation
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pioneer Scout Reservation clear sky chart from 2005-11-06 to 2024-01-12.

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
37%
24437
16%
74617
11%
24381
43%
24381
20%
51764

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
19%
950
13%
2648
5%
946
26%
946
14%
2039
January11th to 20thNight
17%
906
8%
2535
4%
906
21%
906
11%
2035
January21st to endNight
20%
885
9%
2667
4%
885
26%
885
11%
2137
February1st to 10thNight
18%
720
9%
2300
3%
720
24%
720
11%
1777
February11th to 20thNight
23%
700
15%
2099
7%
700
30%
700
14%
1562
February21st to endNight
16%
592
15%
1776
3%
592
28%
592
15%
1317
March1st to 10thNight
27%
720
15%
2160
10%
720
31%
720
17%
1543
March11th to 20thNight
29%
720
21%
1990
9%
720
38%
720
24%
1330
March21st to endNight
28%
792
17%
2178
9%
792
35%
792
20%
1563
April1st to 10thNight
31%
550
17%
1810
8%
550
41%
550
21%
1200
April11th to 20thNight
31%
533
20%
1697
10%
533
42%
533
21%
1134
April21st to endNight
32%
540
18%
1620
7%
540
41%
540
23%
1091
May1st to 10thNight
34%
540
12%
1620
6%
540
39%
540
18%
1172
May11th to 20thNight
39%
531
16%
1593
10%
531
45%
531
22%
1088
May21st to endNight
53%
583
15%
1697
10%
582
58%
582
30%
1054
June1st to 10thNight
55%
540
18%
1440
11%
540
61%
540
37%
889
June11th to 20thNight
55%
540
18%
1440
14%
540
58%
540
32%
931
June21st to endNight
57%
540
19%
1440
13%
540
62%
540
36%
899
July1st to 10thNight
66%
525
17%
1400
15%
525
68%
525
38%
834
July11th to 20thNight
66%
522
22%
1392
18%
522
69%
522
41%
831
July21st to endNight
67%
591
21%
1577
16%
558
71%
558
40%
911
August1st to 10thNight
69%
537
22%
1600
18%
534
72%
534
38%
899
August11th to 20thNight
67%
534
23%
1598
18%
534
71%
534
37%
929
August21st to endNight
65%
594
23%
1908
21%
594
68%
594
34%
1083
September1st to 10thNight
59%
600
23%
1860
20%
600
63%
600
31%
1097
September11th to 20thNight
64%
720
30%
1980
25%
720
67%
720
38%
1162
September21st to endNight
52%
720
24%
1980
19%
720
57%
720
31%
1274
October1st to 10thNight
48%
720
23%
1980
17%
720
54%
720
32%
1247
October11th to 20thNight
32%
720
18%
2150
10%
720
41%
720
20%
1480
October21st to endNight
27%
792
19%
2574
12%
792
37%
792
18%
1763
November1st to 10thNight
35%
740
21%
2406
16%
740
43%
740
23%
1518
November11th to 20thNight
27%
760
18%
2470
11%
760
37%
760
17%
1709
November21st to endNight
27%
760
14%
2470
10%
760
33%
760
15%
1809
December1st to 10thNight
20%
760
9%
2470
6%
760
25%
760
11%
1902
December11th to 20thNight
19%
920
9%
3222
4%
919
25%
919
11%
2471
December21st to endNight
16%
1040
5%
4870
3%
1026
21%
1026
5%
4084

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
14%9%47%6%35%5%6%8%33%
74872
Night
15%9%47%6%345%5%7%35%
74848
TransparencyDay
48%6%12%20%12%1
74580
Night
48%6%12%20%13%2
74661
SeeingDay
17%9%27%25%15%7%
14498
Night
19%8%29%30%13%1
24447

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
15%15%6%11%9%45%5%6%5%19%
1517
11th to 20thDay
17%17%7%12%7%45%5%46%16%
1448
21st to endDay
15%16%10%11%9%45%346%18%
1687
February1st to 10thDay
15%16%6%10%10%45%446%20%
1660
11th to 20thDay
16%10%5%11%9%45%5%6%6%23%
1748
21st to endDay
17%12%6%11%7%3446%7%24%
1480
March1st to 10thDay
15%10%5%8%8%46%5%5%7%27%
1800
11th to 20thDay
14%10%49%6%345%5%7%33%
1968
21st to endDay
22%12%5%7%6%35%447%26%
2182
April1st to 10thDay
17%10%5%6%6%45%6%6%7%29%
2160
11th to 20thDay
18%8%36%5%35%5%5%6%35%
2210
21st to endDay
18%9%37%5%35%45%8%33%
2340
May1st to 10thDay
17%8%46%7%36%6%5%7%31%
2340
11th to 20thDay
19%8%36%5%35%46%7%34%
2301
21st to endDay
10%6%36%5%46%5%6%10%39%
2575
June1st to 10thDay
10%6%26%5%46%6%6%8%41%
2520
11th to 20thDay
9%6%25%5%46%5%6%9%43%
2520
21st to endDay
11%426%6%36%7%7%10%38%
2520
July1st to 10thDay
7%5%25%5%346%7%10%45%
2520
11th to 20thDay
8%4345%45%6%7%10%44%
2520
21st to endDay
7%435%6%46%6%6%9%44%
2645
August1st to 10thDay
6%425%6%36%6%8%9%44%
2327
11th to 20thDay
10%5%25%5%46%6%6%10%40%
2303
21st to endDay
9%5%25%5%35%5%6%10%45%
2444
September1st to 10thDay
12%6%35%6%345%6%8%42%
2081
11th to 20thDay
11%424435%6%7%10%44%
1980
21st to endDay
12%7%25%5%35%46%8%42%
1980
October1st to 10thDay
13%6%36%6%345%5%7%43%
1980
11th to 20thDay
17%7%37%5%45%5%6%7%34%
1807
21st to endDay
19%11%37%6%35%46%7%28%
1782
November1st to 10thDay
12%8%36%5%2346%7%43%
1672
11th to 20thDay
16%13%47%7%34446%30%
1710
21st to endDay
20%14%5%8%6%35%45%5%25%
1710
December1st to 10thDay
15%15%7%12%8%3445%5%22%
1710
11th to 20thDay
15%14%6%11%7%36%5%5%6%22%
1942
21st to endDay
22%21%10%10%7%34445%11%
2783
January1st to 10thNight
17%12%5%10%7%446%5%7%23%
2648
11th to 20thNight
18%13%6%10%8%45%446%22%
2535
21st to endNight
15%14%6%11%8%45%5%5%6%20%
2667
February1st to 10thNight
18%14%5%8%8%45%45%6%23%
2300
11th to 20thNight
15%12%5%8%7%45%5%5%7%27%
2098
21st to endNight
21%11%47%6%35%445%30%
1776
March1st to 10thNight
15%9%48%7%45%45%6%33%
2160
11th to 20thNight
13%8%35%5%45%45%7%41%
1990
21st to endNight
21%8%47%5%3345%6%33%
2178
April1st to 10thNight
14%8%36%5%345%6%8%37%
1810
11th to 20thNight
19%7%35%6%3445%6%37%
1697
21st to endNight
18%8%35%5%245%5%7%37%
1620
May1st to 10thNight
17%8%47%7%45%5%6%8%30%
1620
11th to 20thNight
21%7%25%5%34447%38%
1592
21st to endNight
11%435%5%446%7%10%43%
1696
June1st to 10thNight
10%4245%345%6%9%48%
1440
11th to 20thNight
8%5%36%6%35%5%6%7%45%
1440
21st to endNight
8%425%6%345%7%9%46%
1440
July1st to 10thNight
6%5%2443446%8%53%
1440
11th to 20thNight
8%425%424448%55%
1440
21st to endNight
5%4245%35%5%7%10%50%
1670
August1st to 10thNight
6%3244346%6%10%51%
1611
11th to 20thNight
7%5%145%35%5%6%8%50%
1598
21st to endNight
9%3245%45%5%5%9%51%
1908
September1st to 10thNight
10%6%25%43445%6%50%
1860
11th to 20thNight
9%4235%2445%7%55%
1980
21st to endNight
13%6%26%4345%46%47%
1980
October1st to 10thNight
12%7%35%43345%8%47%
1980
11th to 20thNight
17%8%46%6%345%5%6%36%
2150
21st to endNight
20%9%36%5%3445%6%36%
2574
November1st to 10thNight
12%8%36%6%4445%7%42%
2406
11th to 20thNight
17%10%38%6%35%45%7%32%
2470
21st to endNight
18%12%6%7%6%445%46%29%
2470
December1st to 10thNight
18%12%6%11%7%45%5%6%6%21%
2470
11th to 20thNight
17%13%6%10%8%45%45%6%23%
3250
21st to endNight
26%17%7%10%6%34445%13%
4884

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
66%5%10%13%5%
1518
11th to 20thDay
69%5%13%8%4
1448
21st to endDay
67%6%9%12%5%1
1687
February1st to 10thDay
66%5%9%12%7%1
1660
11th to 20thDay
60%5%10%16%8%1
1758
21st to endDay
58%5%12%15%6%2
1480
March1st to 10thDay
57%6%10%19%7%
1800
11th to 20thDay
51%5%12%19%11%2
1968
21st to endDay
59%5%10%19%5%1
2182
April1st to 10thDay
53%6%11%19%11%
2160
11th to 20thDay
48%6%11%21%12%2
2210
21st to endDay
49%5%14%17%12%2
2340
May1st to 10thDay
51%7%13%19%10%
2340
11th to 20thDay
49%6%11%19%14%2
2305
21st to endDay
40%7%13%25%13%2
2575
June1st to 10thDay
39%7%11%26%15%2
2520
11th to 20thDay
36%7%13%24%18%2
2520
21st to endDay
40%8%13%22%15%3
2520
July1st to 10thDay
32%8%14%24%18%4
2451
11th to 20thDay
33%8%13%27%17%2
2445
21st to endDay
34%8%14%24%18%2
2498
August1st to 10thDay
33%9%16%26%15%1
2314
11th to 20thDay
37%10%12%26%14%1
2303
21st to endDay
35%6%11%26%17%4
2444
September1st to 10thDay
40%7%14%21%16%2
2081
11th to 20thDay
33%7%12%28%19%1
1980
21st to endDay
38%5%13%25%18%1
1980
October1st to 10thDay
41%5%12%25%16%2
1980
11th to 20thDay
47%6%10%22%14%
1807
21st to endDay
54%5%14%17%8%1
1782
November1st to 10thDay
40%5%13%26%16%1
1672
11th to 20thDay
55%5%11%18%10%1
1710
21st to endDay
60%412%16%7%
1710
December1st to 10thDay
66%5%11%12%5%
1710
11th to 20thDay
60%7%13%15%5%
1939
21st to endDay
77%5%7%6%5%
2783
January1st to 10thNight
59%5%11%17%7%
2648
11th to 20thNight
65%5%13%12%6%
2535
21st to endNight
64%6%10%13%6%1
2667
February1st to 10thNight
62%5%11%15%6%1
2300
11th to 20thNight
57%5%8%19%9%1
2099
21st to endNight
57%5%10%18%9%2
1776
March1st to 10thNight
52%5%9%21%11%1
2160
11th to 20thNight
43%5%13%20%16%3
1990
21st to endNight
52%410%23%10%1
2178
April1st to 10thNight
45%6%10%23%14%2
1810
11th to 20thNight
47%5%10%19%18%2
1697
21st to endNight
47%5%11%20%16%3
1620
May1st to 10thNight
51%7%11%18%10%2
1620
11th to 20thNight
46%6%9%20%17%2
1593
21st to endNight
37%6%16%26%13%2
1697
June1st to 10thNight
33%5%13%27%19%3
1440
11th to 20thNight
36%8%13%24%18%2
1440
21st to endNight
31%8%16%25%17%2
1440
July1st to 10thNight
30%7%14%23%23%4
1400
11th to 20thNight
29%6%16%25%21%3
1392
21st to endNight
27%7%15%25%20%5%
1577
August1st to 10thNight
27%7%15%31%18%2
1600
11th to 20thNight
30%7%16%27%17%3
1598
21st to endNight
31%6%12%25%23%4
1908
September1st to 10thNight
34%6%11%27%19%4
1860
11th to 20thNight
29%6%9%30%24%1
1980
21st to endNight
38%6%10%28%17%2
1980
October1st to 10thNight
36%6%10%28%19%1
1980
11th to 20thNight
47%6%10%20%16%1
2150
21st to endNight
49%5%10%23%12%1
2574
November1st to 10thNight
41%6%11%24%16%1
2406
11th to 20thNight
51%412%21%10%2
2470
21st to endNight
56%5%12%20%7%
2470
December1st to 10thNight
61%6%11%15%7%
2470
11th to 20thNight
62%413%13%7%1
3252
21st to endNight
73%5%11%8%3
4884

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
24%17%30%21%6%1
270
11th to 20thDay
23%10%47%15%41
243
21st to endDay
24%14%33%21%7%1
264
February1st to 10thDay
26%15%33%25%2
240
11th to 20thDay
24%15%40%18%3
240
21st to endDay
24%17%40%16%3
198
March1st to 10thDay
20%19%40%18%4
240
11th to 20thDay
21%11%35%25%7%2
408
21st to endDay
32%11%30%19%7%1
462
April1st to 10thDay
20%14%31%22%12%
420
11th to 20thDay
25%13%29%19%9%4
412
21st to endDay
24%13%33%17%10%3
420
May1st to 10thDay
22%11%30%22%12%3
423
11th to 20thDay
22%8%28%20%15%7%
447
21st to endDay
11%6%25%26%20%11%
529
June1st to 10thDay
11%6%28%29%20%6%
630
11th to 20thDay
12%7%26%29%20%6%
630
21st to endDay
12%428%30%18%7%
630
July1st to 10thDay
9%318%30%24%16%
621
11th to 20thDay
11%320%30%22%13%
618
21st to endDay
8%321%28%30%11%
586
August1st to 10thDay
9%214%30%24%21%
446
11th to 20thDay
11%5%18%26%25%15%
439
21st to endDay
9%316%28%28%16%
495
September1st to 10thDay
15%416%28%23%14%
450
11th to 20thDay
10%416%22%32%16%
450
21st to endDay
16%8%20%24%22%10%
450
October1st to 10thDay
14%6%24%31%17%8%
450
11th to 20thDay
19%15%28%30%9%
443
21st to endDay
26%13%38%18%41
297
November1st to 10thDay
14%12%33%27%10%4
270
11th to 20thDay
21%21%30%20%8%1
270
21st to endDay
26%11%41%19%3
270
December1st to 10thDay
21%19%35%16%9%1
270
11th to 20thDay
22%16%38%20%4
270
21st to endDay
25%20%32%20%2
297
January1st to 10thNight
22%15%35%22%6%1
950
11th to 20thNight
24%12%35%23%5%1
906
21st to endNight
21%11%35%26%6%
885
February1st to 10thNight
24%11%38%23%4
720
11th to 20thNight
22%13%34%27%4
703
21st to endNight
28%11%38%20%3
592
March1st to 10thNight
20%11%34%27%7%1
720
11th to 20thNight
18%12%36%25%7%1
720
21st to endNight
25%9%33%25%7%1
792
April1st to 10thNight
18%11%37%28%6%
550
11th to 20thNight
22%7%35%27%9%1
533
21st to endNight
24%7%32%27%10%
540
May1st to 10thNight
22%7%31%32%9%1
540
11th to 20thNight
24%5%26%29%15%1
531
21st to endNight
13%324%38%20%3
584
June1st to 10thNight
12%224%47%16%
540
11th to 20thNight
9%423%43%19%1
540
21st to endNight
9%321%41%23%2
540
July1st to 10thNight
8%214%41%28%6%
525
11th to 20thNight
9%215%41%30%3
522
21st to endNight
5%216%45%30%1
591
August1st to 10thNight
7%115%41%31%4
537
11th to 20thNight
9%113%41%31%5%
534
21st to endNight
11%215%35%34%4
594
September1st to 10thNight
12%316%33%31%5%
600
11th to 20thNight
11%315%34%33%4
720
21st to endNight
15%5%20%32%22%4
720
October1st to 10thNight
14%6%25%33%21%2
720
11th to 20thNight
22%10%30%28%9%1
720
21st to endNight
23%12%33%24%7%
792
November1st to 10thNight
15%11%33%27%13%1
740
11th to 20thNight
22%12%31%28%6%1
760
21st to endNight
23%10%32%28%6%
760
December1st to 10thNight
24%14%34%22%6%
760
11th to 20thNight
24%12%35%24%41
921
21st to endNight
30%11%32%24%3
1045
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