Otterholt
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Otterholt clear sky chart from 2005-11-06 to 2024-01-15.

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
35%
24872
15%
74690
9%
24811
42%
24811
22%
51146

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%
950
12%
2648
4%
946
32%
946
18%
1951
January11th to 20thNight
23%
921
10%
2577
5%
921
26%
921
14%
2017
January21st to endNight
24%
990
12%
2651
4%
990
29%
990
15%
2087
February1st to 10thNight
25%
900
13%
2340
4%
900
32%
900
20%
1720
February11th to 20thNight
26%
879
18%
2273
5%
874
34%
874
23%
1581
February21st to endNight
28%
625
16%
1809
6%
625
38%
625
18%
1302
March1st to 10thNight
29%
688
15%
2128
10%
688
34%
688
20%
1457
March11th to 20thNight
33%
540
20%
1980
14%
540
43%
540
20%
1243
March21st to endNight
34%
594
18%
2096
14%
594
41%
594
18%
1419
April1st to 10thNight
28%
540
15%
1800
10%
540
36%
540
18%
1233
April11th to 20thNight
31%
533
15%
1775
11%
533
40%
533
17%
1252
April21st to endNight
32%
540
15%
1683
10%
540
40%
540
21%
1157
May1st to 10thNight
32%
540
14%
1440
7%
540
37%
540
23%
1039
May11th to 20thNight
38%
531
18%
1417
10%
531
43%
531
27%
974
May21st to endNight
47%
584
13%
1551
6%
582
51%
582
28%
1032
June1st to 10thNight
49%
540
14%
1440
6%
540
53%
540
34%
910
June11th to 20thNight
45%
540
15%
1440
7%
540
49%
540
33%
921
June21st to endNight
58%
540
15%
1440
8%
540
60%
540
35%
900
July1st to 10thNight
63%
525
17%
1400
9%
525
65%
525
46%
793
July11th to 20thNight
57%
522
19%
1392
9%
522
60%
522
38%
847
July21st to endNight
66%
591
21%
1487
12%
558
69%
558
48%
831
August1st to 10thNight
65%
537
22%
1514
18%
534
68%
534
36%
910
August11th to 20thNight
58%
534
21%
1600
18%
534
63%
534
31%
982
August21st to endNight
53%
594
21%
1948
20%
594
59%
594
30%
1140
September1st to 10thNight
53%
540
22%
1800
21%
540
60%
540
31%
1029
September11th to 20thNight
53%
540
25%
1800
23%
540
61%
540
33%
1023
September21st to endNight
40%
666
19%
2038
11%
666
46%
666
28%
1260
October1st to 10thNight
42%
720
20%
2160
13%
720
48%
720
29%
1344
October11th to 20thNight
31%
720
17%
2160
9%
720
38%
720
22%
1450
October21st to endNight
32%
792
15%
2479
9%
792
39%
792
18%
1707
November1st to 10thNight
33%
778
21%
2444
12%
778
42%
778
22%
1584
November11th to 20thNight
26%
950
14%
2660
6%
950
34%
950
19%
1917
November21st to endNight
26%
950
15%
2660
7%
950
33%
950
19%
1896
December1st to 10thNight
24%
950
10%
2660
4%
950
30%
950
16%
2001
December11th to 20thNight
20%
948
11%
3206
3%
948
27%
948
11%
2444
December21st to endNight
17%
1040
6%
4794
3%
1026
24%
1026
7%
3793

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%5%7%35%
74765
Night
14%9%47%6%3445%7%37%
75037
TransparencyDay
47%7%13%22%10%1
74465
Night
46%6%13%22%12%1
74857
SeeingDay
17%10%29%26%14%4
14859
Night
17%9%31%31%11%1
24879

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
11%11%7%9%7%45%6%6%6%28%
1517
11th to 20thDay
11%14%8%12%8%46%46%7%19%
1472
21st to endDay
11%13%6%14%8%36%6%6%7%19%
1701
February1st to 10thDay
9%11%5%10%7%46%6%5%7%32%
1620
11th to 20thDay
9%10%6%9%8%35%46%8%33%
1574
21st to endDay
13%11%5%9%7%345%5%6%31%
1446
March1st to 10thDay
14%11%49%7%345%46%33%
1849
11th to 20thDay
13%10%46%6%45%447%36%
1980
21st to endDay
18%10%38%6%35%45%8%30%
2259
April1st to 10thDay
16%11%37%5%35%5%6%7%33%
2160
11th to 20thDay
21%10%47%6%35%446%30%
2134
21st to endDay
21%10%37%5%35%46%6%30%
2275
May1st to 10thDay
18%7%37%6%5%5%5%5%7%34%
2520
11th to 20thDay
16%8%36%5%35%5%5%7%35%
2479
21st to endDay
15%7%36%6%45%5%5%8%36%
2725
June1st to 10thDay
12%6%245%45%5%6%9%42%
2520
11th to 20thDay
12%7%37%7%45%5%6%8%37%
2520
21st to endDay
10%5%25%5%45%7%7%10%40%
2520
July1st to 10thDay
7%4135%36%6%7%10%48%
2520
11th to 20thDay
10%425%5%345%7%9%46%
2520
21st to endDay
8%424445%5%6%9%49%
2743
August1st to 10thDay
10%5%35%6%45%5%7%9%41%
2413
11th to 20thDay
13%5%35%5%45%5%6%7%43%
2301
21st to endDay
12%5%244345%6%9%47%
2406
September1st to 10thDay
11%5%25%5%35%5%6%8%45%
2160
11th to 20thDay
13%5%245%345%5%8%45%
2160
21st to endDay
16%7%26%4345%5%7%40%
1903
October1st to 10thDay
17%6%26%5%346%5%7%39%
1800
11th to 20thDay
17%13%36%6%445%5%6%32%
1800
21st to endDay
19%11%46%5%33445%35%
1877
November1st to 10thDay
13%11%5%6%6%3445%6%38%
1630
11th to 20thDay
14%12%7%10%7%445%5%6%26%
1520
21st to endDay
15%10%5%6%6%3446%7%35%
1520
December1st to 10thDay
11%13%6%13%9%47%5%5%5%22%
1520
11th to 20thDay
12%14%8%10%9%35%45%5%25%
1918
21st to endDay
23%17%6%12%7%3433418%
2783
January1st to 10thNight
10%10%5%10%8%36%5%6%6%31%
2648
11th to 20thNight
12%12%6%11%8%45%5%46%26%
2577
21st to endNight
11%15%7%11%7%35%5%6%6%23%
2651
February1st to 10thNight
7%10%6%10%7%5%5%5%5%6%33%
2340
11th to 20thNight
8%10%47%7%45%46%7%37%
2273
21st to endNight
13%12%46%6%45%5%5%7%33%
1809
March1st to 10thNight
12%9%47%6%35%5%5%6%38%
2128
11th to 20thNight
13%8%47%5%3445%6%42%
1980
21st to endNight
17%8%47%6%44446%36%
2096
April1st to 10thNight
20%8%37%44445%7%34%
1800
11th to 20thNight
24%9%45%5%3345%6%33%
1775
21st to endNight
19%9%36%5%3445%7%35%
1683
May1st to 10thNight
19%8%36%6%3446%6%35%
1440
11th to 20thNight
18%5%36%5%3435%6%41%
1416
21st to endNight
14%5%27%5%3447%7%42%
1551
June1st to 10thNight
10%5%25%4245%8%9%45%
1440
11th to 20thNight
10%5%25%5%45%45%8%46%
1440
21st to endNight
7%5%15%5%25%7%7%11%46%
1440
July1st to 10thNight
6%5%133235%6%9%56%
1440
11th to 20thNight
9%4244445%7%10%48%
1440
21st to endNight
5%324335%46%9%57%
1575
August1st to 10thNight
8%425%435%46%8%50%
1523
11th to 20thNight
13%6%2432346%8%48%
1600
21st to endNight
11%5%25%434446%52%
1948
September1st to 10thNight
10%435%5%25%45%7%51%
1800
11th to 20thNight
10%5%3443436%8%51%
1800
21st to endNight
15%6%24435%45%7%45%
2038
October1st to 10thNight
15%6%245%34447%47%
2160
11th to 20thNight
17%9%35%5%335%47%38%
2160
21st to endNight
18%9%45%6%35%5%45%36%
2479
November1st to 10thNight
14%9%46%43445%8%40%
2444
11th to 20thNight
14%9%410%6%3445%7%34%
2660
21st to endNight
14%10%48%6%345%5%6%35%
2660
December1st to 10thNight
11%12%6%10%8%45%45%7%29%
2660
11th to 20thNight
12%15%5%9%8%45%6%5%5%25%
3279
21st to endNight
25%16%6%9%6%3444420%
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
55%7%12%20%7%1
1518
11th to 20thDay
63%6%11%11%8%
1472
21st to endDay
62%6%12%13%7%
1701
February1st to 10thDay
52%6%13%20%8%1
1620
11th to 20thDay
49%5%13%22%9%1
1583
21st to endDay
54%6%10%19%10%1
1446
March1st to 10thDay
52%5%15%18%9%1
1849
11th to 20thDay
49%6%14%22%9%1
1980
21st to endDay
53%6%11%21%8%1
2259
April1st to 10thDay
50%6%11%20%12%1
2160
11th to 20thDay
56%6%10%17%11%1
2134
21st to endDay
54%6%14%16%9%1
2275
May1st to 10thDay
49%6%13%22%9%1
2520
11th to 20thDay
48%7%13%20%11%1
2483
21st to endDay
45%8%11%23%12%2
2725
June1st to 10thDay
37%7%15%28%11%1
2520
11th to 20thDay
43%9%13%22%13%1
2520
21st to endDay
36%9%18%26%9%1
2520
July1st to 10thDay
29%9%17%31%13%1
2451
11th to 20thDay
33%7%16%25%17%2
2445
21st to endDay
30%8%18%28%15%1
2591
August1st to 10thDay
37%9%16%28%9%2
2398
11th to 20thDay
39%8%15%27%11%
2301
21st to endDay
33%7%15%28%15%1
2406
September1st to 10thDay
36%8%14%29%13%
2160
11th to 20thDay
37%8%16%31%8%1
2160
21st to endDay
43%6%13%28%9%
1903
October1st to 10thDay
43%6%13%28%9%1
1800
11th to 20thDay
51%6%13%20%9%1
1800
21st to endDay
51%5%14%21%9%
1877
November1st to 10thDay
47%6%11%21%12%2
1630
11th to 20thDay
58%6%13%16%7%1
1520
21st to endDay
49%5%16%22%7%2
1520
December1st to 10thDay
63%6%13%14%4
1520
11th to 20thDay
62%414%14%5%1
1915
21st to endDay
72%5%7%11%6%
2783
January1st to 10thNight
52%7%12%19%9%1
2648
11th to 20thNight
59%7%12%14%7%
2577
21st to endNight
60%6%9%16%9%1
2651
February1st to 10thNight
50%6%11%21%9%2
2340
11th to 20thNight
46%5%14%24%10%2
2274
21st to endNight
51%6%11%20%11%1
1809
March1st to 10thNight
47%6%13%22%9%2
2128
11th to 20thNight
44%5%13%22%15%1
1980
21st to endNight
49%5%10%23%12%1
2096
April1st to 10thNight
50%5%9%18%17%1
1800
11th to 20thNight
52%6%8%18%14%2
1775
21st to endNight
48%6%11%21%14%1
1683
May1st to 10thNight
48%6%14%18%13%1
1440
11th to 20thNight
43%6%10%24%14%2
1417
21st to endNight
40%7%14%21%17%1
1552
June1st to 10thNight
31%10%15%28%15%1
1440
11th to 20thNight
35%7%14%24%19%1
1440
21st to endNight
30%10%16%30%13%3
1440
July1st to 10thNight
23%7%17%32%19%2
1400
11th to 20thNight
29%9%14%28%18%3
1392
21st to endNight
22%7%18%31%19%3
1487
August1st to 10thNight
31%7%14%31%14%4
1514
11th to 20thNight
34%8%15%26%16%2
1600
21st to endNight
34%6%12%29%16%3
1948
September1st to 10thNight
32%7%13%33%15%1
1800
11th to 20thNight
31%6%16%32%15%
1800
21st to endNight
37%6%14%31%11%1
2038
October1st to 10thNight
38%6%12%30%13%1
2160
11th to 20thNight
45%6%14%22%12%1
2160
21st to endNight
49%6%13%20%12%1
2479
November1st to 10thNight
43%5%13%24%13%1
2444
11th to 20thNight
51%5%15%17%12%1
2660
21st to endNight
49%6%15%22%6%1
2660
December1st to 10thNight
56%6%13%20%5%
2660
11th to 20thNight
59%6%12%17%5%1
3281
21st to endNight
68%48%15%5%
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
17%11%32%26%10%3
270
11th to 20thDay
20%10%37%25%8%
252
21st to endDay
19%8%40%22%11%1
264
February1st to 10thDay
16%12%48%18%6%
240
11th to 20thDay
16%17%40%19%8%
240
21st to endDay
16%13%44%25%2
198
March1st to 10thDay
18%13%38%20%11%1
240
11th to 20thDay
21%9%36%24%8%3
240
21st to endDay
23%14%29%21%8%4
345
April1st to 10thDay
22%19%29%22%8%
420
11th to 20thDay
29%11%24%27%8%2
412
21st to endDay
26%14%28%21%9%2
531
May1st to 10thDay
20%14%29%27%8%2
603
11th to 20thDay
21%12%26%24%13%4
625
21st to endDay
19%10%25%24%19%4
679
June1st to 10thDay
12%7%27%31%18%5%
630
11th to 20thDay
13%9%32%30%13%3
630
21st to endDay
12%7%28%30%16%7%
630
July1st to 10thDay
7%421%29%27%12%
621
11th to 20thDay
10%5%27%31%19%8%
618
21st to endDay
8%424%33%22%8%
684
August1st to 10thDay
11%422%33%23%6%
626
11th to 20thDay
13%419%29%27%8%
615
21st to endDay
14%6%22%28%23%5%
525
September1st to 10thDay
13%7%25%30%20%5%
450
11th to 20thDay
12%7%27%32%20%2
450
21st to endDay
22%11%26%27%12%3
337
October1st to 10thDay
19%10%29%21%19%3
270
11th to 20thDay
21%19%30%23%7%
270
21st to endDay
25%14%38%16%5%1
297
November1st to 10thDay
20%11%36%23%9%1
270
11th to 20thDay
21%17%34%20%6%
270
21st to endDay
21%17%35%19%7%
270
December1st to 10thDay
15%14%39%21%10%1
270
11th to 20thDay
22%13%37%21%6%
270
21st to endDay
28%10%40%19%21
297
January1st to 10thNight
14%11%37%29%8%
950
11th to 20thNight
18%10%36%28%7%1
921
21st to endNight
18%9%34%31%7%1
990
February1st to 10thNight
12%12%40%29%7%1
900
11th to 20thNight
13%14%40%25%7%1
879
21st to endNight
18%13%33%30%7%
625
March1st to 10thNight
16%12%35%28%8%1
688
11th to 20thNight
16%10%36%29%8%1
540
21st to endNight
20%9%32%26%10%3
594
April1st to 10thNight
22%11%35%27%5%
540
11th to 20thNight
27%8%28%28%7%1
533
21st to endNight
23%8%32%29%8%1
540
May1st to 10thNight
20%9%32%32%6%1
540
11th to 20thNight
18%8%31%31%11%2
531
21st to endNight
15%8%22%39%15%1
584
June1st to 10thNight
11%430%42%12%1
540
11th to 20thNight
13%431%41%10%
540
21st to endNight
9%323%47%17%1
540
July1st to 10thNight
6%421%39%27%2
525
11th to 20thNight
11%424%40%19%2
522
21st to endNight
5%320%47%22%2
591
August1st to 10thNight
9%414%47%25%1
537
11th to 20thNight
15%319%33%27%3
534
21st to endNight
14%325%32%24%2
594
September1st to 10thNight
9%328%36%20%3
540
11th to 20thNight
11%427%37%18%2
540
21st to endNight
16%10%29%30%14%1
666
October1st to 10thNight
18%8%27%33%14%1
720
11th to 20thNight
20%13%31%29%8%
720
21st to endNight
23%10%30%29%8%
792
November1st to 10thNight
19%9%34%29%9%1
778
11th to 20thNight
19%12%35%26%8%
950
21st to endNight
20%14%34%26%6%
950
December1st to 10thNight
18%9%37%28%8%1
950
11th to 20thNight
21%10%36%24%8%2
950
21st to endNight
27%10%33%24%6%
1045
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