Pense
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pense clear sky chart from 2005-11-06 to 2024-03-18.

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
39%
24649
13%
80862
8%
24572
44%
24572
21%
53423

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
32%
936
11%
4684
5%
926
39%
926
11%
3261
January11th to 20thNight
29%
943
8%
4474
5%
930
34%
930
9%
3382
January21st to endNight
25%
1032
8%
4811
4%
1023
31%
1023
10%
3020
February1st to 10thNight
29%
908
11%
2618
6%
908
35%
908
15%
1969
February11th to 20thNight
32%
740
13%
2403
8%
740
39%
740
17%
1723
February21st to endNight
45%
628
16%
1928
12%
628
50%
628
22%
1339
March1st to 10thNight
33%
760
11%
2280
7%
760
37%
760
18%
1679
March11th to 20thNight
37%
752
17%
2154
10%
752
44%
752
24%
1475
March21st to endNight
38%
634
12%
2020
10%
634
43%
634
18%
1430
April1st to 10thNight
42%
540
17%
1800
13%
540
51%
540
27%
1084
April11th to 20thNight
33%
533
13%
1764
9%
533
39%
533
18%
1218
April21st to endNight
36%
540
14%
1460
9%
540
40%
540
23%
1046
May1st to 10thNight
47%
540
15%
1440
8%
540
50%
540
31%
935
May11th to 20thNight
45%
531
14%
1418
8%
531
47%
531
31%
921
May21st to endNight
42%
584
8%
1517
4%
582
45%
582
25%
1054
June1st to 10thNight
44%
425
7%
1145
4%
425
48%
425
33%
708
June11th to 20thNight
43%
360
4%
1080
4%
360
45%
360
25%
700
June21st to endNight
53%
360
4%
1080
5%
360
55%
360
30%
659
July1st to 10thNight
62%
350
6%
1153
7%
350
64%
350
38%
604
July11th to 20thNight
58%
410
10%
1280
7%
410
62%
410
41%
686
July21st to endNight
63%
591
17%
1488
9%
558
66%
558
49%
799
August1st to 10thNight
61%
537
18%
1424
10%
534
65%
534
43%
818
August11th to 20thNight
64%
534
21%
1432
14%
534
68%
534
44%
820
August21st to endNight
58%
594
25%
1925
21%
594
66%
594
40%
1009
September1st to 10thNight
53%
540
21%
1800
18%
540
61%
540
32%
999
September11th to 20thNight
51%
540
21%
1804
19%
540
58%
540
31%
1031
September21st to endNight
45%
576
23%
2016
18%
576
55%
576
28%
1137
October1st to 10thNight
42%
720
18%
2160
12%
720
46%
720
26%
1393
October11th to 20thNight
42%
764
21%
2204
12%
764
49%
764
30%
1371
October21st to endNight
31%
990
16%
2574
6%
990
38%
990
21%
1861
November1st to 10thNight
30%
925
14%
2526
6%
925
35%
925
18%
1884
November11th to 20thNight
31%
950
13%
2660
6%
950
36%
950
18%
1982
November21st to endNight
27%
950
11%
2786
5%
950
34%
950
18%
1995
December1st to 10thNight
30%
950
10%
2850
5%
950
35%
950
15%
2163
December11th to 20thNight
25%
950
11%
3561
4%
949
32%
949
10%
2689
December21st to endNight
31%
1032
9%
5143
6%
1026
38%
1026
13%
2579

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
10%8%47%7%45%5%6%8%37%
78162
Night
8%9%48%7%45%5%6%7%37%
81557
TransparencyDay
44%7%15%23%9%1
77877
Night
45%6%15%23%10%1
81422
SeeingDay
12%8%29%30%17%4
14987
Night
12%7%31%35%13%1
24700

By Month

Percentage Cloud Cover NW (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
8%12%410%9%5%7%8%7%6%23%
2219
11th to 20thDay
5%6%410%11%8%11%10%8%7%20%
2425
21st to endDay
5%11%5%11%7%47%5%5%7%33%
2794
February1st to 10thDay
9%11%6%12%10%5%7%6%5%6%22%
1577
11th to 20thDay
8%13%5%8%8%5%9%8%6%6%25%
1665
21st to endDay
5%9%7%11%11%6%7%7%7%6%23%
1525
March1st to 10thDay
9%13%7%12%10%46%5%6%7%21%
1900
11th to 20thDay
7%11%5%8%7%46%5%6%9%33%
1967
21st to endDay
9%11%5%9%8%45%6%6%8%29%
2335
April1st to 10thDay
7%8%36%7%36%7%7%9%37%
2160
11th to 20thDay
14%12%49%8%45%5%7%6%28%
2147
21st to endDay
14%10%36%6%45%45%7%35%
2497
May1st to 10thDay
11%7%36%5%46%45%7%40%
2520
11th to 20thDay
8%7%36%7%46%5%6%7%41%
2478
21st to endDay
19%7%36%6%45%5%6%9%31%
2755
June1st to 10thDay
15%6%26%5%35%5%6%8%38%
2812
11th to 20thDay
19%7%36%6%45%5%6%8%32%
2880
21st to endDay
9%6%25%5%35%5%7%9%42%
2880
July1st to 10thDay
7%4245%345%7%9%51%
2768
11th to 20thDay
8%424445%5%6%8%50%
2634
21st to endDay
5%323425%5%5%9%57%
2742
August1st to 10thDay
7%5%15%435%5%6%8%51%
2507
11th to 20thDay
9%4245%3445%9%51%
2466
21st to endDay
9%5%245%24448%52%
2430
September1st to 10thDay
11%5%25%4345%5%8%48%
2160
11th to 20thDay
12%7%25%5%34447%45%
2156
21st to endDay
12%5%25%42346%9%47%
1943
October1st to 10thDay
16%10%36%6%3435%6%40%
1800
11th to 20thDay
9%9%48%5%245%5%7%41%
1737
21st to endDay
10%12%6%10%7%3445%7%33%
1782
November1st to 10thDay
12%13%6%9%7%35%446%31%
1552
11th to 20thDay
6%10%5%13%9%5%6%5%5%7%30%
1520
21st to endDay
10%11%6%8%8%46%6%6%6%29%
1392
December1st to 10thDay
8%12%5%12%11%5%6%6%6%6%23%
1330
11th to 20thDay
6%13%9%11%10%46%6%5%7%22%
1571
21st to endDay
5%7%47%7%35%446%46%
2136
January1st to 10thNight
411%6%12%10%46%6%6%6%28%
4726
11th to 20thNight
47%5%12%12%8%10%8%6%5%22%
4476
21st to endNight
6%12%48%6%47%5%5%7%34%
4873
February1st to 10thNight
7%11%6%10%10%5%7%6%6%7%25%
2618
11th to 20thNight
7%11%5%9%9%47%7%6%7%28%
2402
21st to endNight
46%412%9%5%7%6%7%8%32%
1928
March1st to 10thNight
8%10%5%11%9%46%6%7%7%29%
2280
11th to 20thNight
7%10%5%8%6%46%5%7%8%36%
2154
21st to endNight
10%10%5%9%6%47%5%6%7%30%
2020
April1st to 10thNight
7%8%36%5%445%6%8%43%
1800
11th to 20thNight
12%11%47%5%36%5%6%8%32%
1764
21st to endNight
13%9%5%6%6%36%6%5%8%32%
1460
May1st to 10thNight
12%8%34435%5%6%9%40%
1440
11th to 20thNight
10%7%35%5%35%5%6%9%43%
1418
21st to endNight
17%6%35%6%345%8%8%36%
1517
June1st to 10thNight
12%425%4245%7%9%45%
1145
11th to 20thNight
15%6%35%435%45%10%41%
1080
21st to endNight
9%424426%6%7%9%47%
1080
July1st to 10thNight
6%413425%46%8%56%
1188
11th to 20thNight
7%32432445%9%55%
1322
21st to endNight
5%22332345%9%62%
1576
August1st to 10thNight
7%3134335%6%8%56%
1432
11th to 20thNight
5%3243345%7%10%54%
1432
21st to endNight
8%423324448%58%
1925
September1st to 10thNight
9%5%244345%5%7%52%
1800
11th to 20thNight
10%5%244345%5%8%49%
1804
21st to endNight
11%6%245%3446%7%49%
2016
October1st to 10thNight
14%9%35%43445%8%41%
2160
11th to 20thNight
8%8%36%43445%6%47%
2204
21st to endNight
9%12%5%8%7%445%5%7%34%
2574
November1st to 10thNight
15%13%5%7%6%34447%32%
2526
11th to 20thNight
8%11%410%9%47%5%6%7%29%
2660
21st to endNight
9%11%5%10%6%35%46%7%32%
2786
December1st to 10thNight
8%11%5%10%10%6%6%6%47%26%
2850
11th to 20thNight
8%12%6%12%9%46%6%5%7%24%
3618
21st to endNight
5%7%36%6%345%5%7%49%
5503

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
58%8%15%14%5%
2219
11th to 20thDay
59%7%16%13%6%
2449
21st to endDay
51%6%15%24%4
2794
February1st to 10thDay
62%5%12%16%6%
1577
11th to 20thDay
57%8%11%13%10%1
1674
21st to endDay
57%8%13%14%8%
1525
March1st to 10thDay
61%7%12%16%4
1900
11th to 20thDay
47%7%18%20%7%
1968
21st to endDay
51%8%18%18%5%
2335
April1st to 10thDay
41%7%17%23%12%1
2160
11th to 20thDay
55%6%13%18%6%2
2147
21st to endDay
49%5%16%22%8%1
2497
May1st to 10thDay
42%5%12%28%12%1
2520
11th to 20thDay
39%8%12%28%13%
2482
21st to endDay
49%6%14%19%11%1
2755
June1st to 10thDay
42%7%14%27%9%1
2812
11th to 20thDay
49%7%14%19%10%1
2880
21st to endDay
36%9%17%28%9%1
2880
July1st to 10thDay
27%6%23%32%10%1
2694
11th to 20thDay
30%8%20%27%14%1
2553
21st to endDay
24%7%16%37%14%1
2590
August1st to 10thDay
29%7%22%28%12%1
2491
11th to 20thDay
30%6%19%31%11%1
2466
21st to endDay
31%6%12%33%16%2
2430
September1st to 10thDay
33%7%15%27%16%2
2160
11th to 20thDay
39%5%14%28%12%2
2156
21st to endDay
34%5%15%32%13%2
1943
October1st to 10thDay
45%5%15%24%10%1
1800
11th to 20thDay
42%413%30%10%1
1737
21st to endDay
52%5%17%19%7%
1782
November1st to 10thDay
57%5%13%18%7%
1552
11th to 20thDay
54%6%15%18%7%1
1520
21st to endDay
54%8%17%17%4
1392
December1st to 10thDay
60%6%13%15%5%1
1330
11th to 20thDay
60%7%19%10%4
1571
21st to endDay
40%412%24%13%7%
2136
January1st to 10thNight
53%7%17%19%4
4726
11th to 20thNight
61%6%16%13%4
4514
21st to endNight
49%6%18%22%4
4873
February1st to 10thNight
57%6%12%18%7%
2618
11th to 20thNight
52%7%13%18%9%1
2403
21st to endNight
48%5%16%22%9%
1928
March1st to 10thNight
53%7%16%18%6%
2280
11th to 20thNight
45%6%17%24%8%1
2154
21st to endNight
51%7%17%17%9%
2020
April1st to 10thNight
38%5%15%25%16%1
1800
11th to 20thNight
49%7%10%20%10%3
1764
21st to endNight
47%7%11%24%10%1
1460
May1st to 10thNight
39%5%12%25%18%2
1440
11th to 20thNight
37%7%11%27%16%2
1418
21st to endNight
43%8%14%21%14%1
1517
June1st to 10thNight
34%6%15%29%14%2
1145
11th to 20thNight
39%8%17%21%13%1
1080
21st to endNight
32%10%17%31%10%1
1080
July1st to 10thNight
25%7%21%34%13%1
1153
11th to 20thNight
25%7%18%33%16%3
1280
21st to endNight
20%7%14%39%18%3
1488
August1st to 10thNight
24%8%18%34%15%1
1424
11th to 20thNight
24%7%19%34%14%2
1432
21st to endNight
26%5%11%35%21%3
1925
September1st to 10thNight
31%6%11%29%22%2
1800
11th to 20thNight
33%6%15%28%16%2
1804
21st to endNight
34%5%13%31%15%2
2016
October1st to 10thNight
42%5%17%25%11%1
2160
11th to 20thNight
37%5%16%29%12%2
2204
21st to endNight
50%5%13%23%8%1
2574
November1st to 10thNight
54%6%13%18%7%2
2526
11th to 20thNight
54%7%17%16%6%
2660
21st to endNight
51%6%20%19%4
2786
December1st to 10thNight
59%5%15%16%6%
2850
11th to 20thNight
59%7%13%16%5%1
3617
21st to endNight
36%412%26%16%5%
5503

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
13%9%28%28%16%5%
180
11th to 20thDay
10%10%29%31%17%2
246
21st to endDay
13%9%31%34%11%1
297
February1st to 10thDay
14%8%34%31%11%1
270
11th to 20thDay
14%7%38%25%14%2
270
21st to endDay
7%5%31%38%16%3
225
March1st to 10thDay
13%8%36%27%13%3
270
11th to 20thDay
11%9%38%25%11%5%
359
21st to endDay
14%11%30%28%15%3
462
April1st to 10thDay
10%15%36%27%9%2
420
11th to 20thDay
18%14%30%26%11%2
425
21st to endDay
16%10%30%28%16%1
600
May1st to 10thDay
12%7%28%30%20%4
603
11th to 20thDay
12%6%27%30%18%8%
625
21st to endDay
17%8%23%27%18%6%
679
June1st to 10thDay
15%10%28%25%18%4
630
11th to 20thDay
19%12%28%25%13%3
630
21st to endDay
10%6%25%33%21%6%
630
July1st to 10thDay
7%5%23%35%24%6%
621
11th to 20thDay
7%6%29%32%20%5%
618
21st to endDay
6%7%26%31%22%9%
684
August1st to 10thDay
9%5%19%39%22%6%
626
11th to 20thDay
8%421%35%25%7%
604
21st to endDay
10%6%24%32%22%6%
495
September1st to 10thDay
11%13%30%30%12%4
450
11th to 20thDay
16%8%28%29%17%2
446
21st to endDay
14%9%28%31%15%3
270
October1st to 10thDay
18%7%27%27%20%2
270
11th to 20thDay
11%13%34%26%16%1
270
21st to endDay
14%12%36%26%10%2
297
November1st to 10thDay
22%10%26%28%11%3
270
11th to 20thDay
13%9%39%29%11%
270
21st to endDay
14%10%36%27%13%1
270
December1st to 10thDay
12%6%36%31%10%4
270
11th to 20thDay
10%10%50%23%6%1
237
21st to endDay
13%6%33%32%14%3
198
January1st to 10thNight
8%11%35%32%13%1
950
11th to 20thNight
12%11%34%34%8%1
950
21st to endNight
12%10%37%30%11%1
1045
February1st to 10thNight
11%8%33%33%14%1
908
11th to 20thNight
11%7%36%34%10%2
744
21st to endNight
5%5%25%41%20%4
628
March1st to 10thNight
10%8%34%34%13%2
760
11th to 20thNight
11%7%35%32%14%1
752
21st to endNight
15%7%29%35%14%1
634
April1st to 10thNight
9%7%35%37%11%1
540
11th to 20thNight
17%10%32%34%7%1
533
21st to endNight
18%8%31%37%6%1
540
May1st to 10thNight
14%5%26%37%17%1
540
11th to 20thNight
14%6%28%36%15%2
531
21st to endNight
20%5%26%32%15%2
584
June1st to 10thNight
13%5%28%35%16%1
425
11th to 20thNight
18%6%27%37%12%1
360
21st to endNight
10%7%24%42%17%1
360
July1st to 10thNight
9%420%48%18%1
350
11th to 20thNight
7%327%45%18%1
410
21st to endNight
5%325%43%22%2
591
August1st to 10thNight
7%324%42%22%2
537
11th to 20thNight
6%421%42%24%3
534
21st to endNight
8%426%41%20%1
594
September1st to 10thNight
10%6%27%39%16%3
540
11th to 20thNight
11%5%25%42%16%1
540
21st to endNight
13%5%30%40%11%1
576
October1st to 10thNight
19%5%27%33%15%1
720
11th to 20thNight
12%5%30%36%15%1
764
21st to endNight
17%10%31%32%10%1
990
November1st to 10thNight
20%8%32%31%8%
925
11th to 20thNight
14%10%33%31%9%2
950
21st to endNight
13%10%37%33%6%1
950
December1st to 10thNight
13%6%35%30%13%3
950
11th to 20thNight
13%11%34%29%13%1
950
21st to endNight
13%6%32%34%13%2
1045
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