Dixon
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dixon clear sky chart from 2005-11-05 to 2017-08-12.

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
39%
15872
18%
46498
11%
15829
46%
15829
26%
30292

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 15thNight
26%
900
14%
2506
5%
895
34%
895
21%
1761
January16th to endNight
24%
960
14%
2550
4%
960
31%
960
19%
1858
February1st to 15thNight
25%
876
15%
2288
3%
876
33%
876
22%
1645
February16th to endNight
28%
641
19%
1903
8%
641
39%
641
23%
1268
March1st to 15thNight
32%
654
17%
2094
11%
654
39%
654
22%
1340
March16th to endNight
28%
576
12%
2040
9%
576
35%
576
16%
1419
April1st to 15thNight
28%
539
17%
1797
11%
539
37%
539
22%
1173
April16th to endNight
37%
540
18%
1800
14%
540
46%
540
20%
1216
May1st to 15thNight
35%
540
17%
1509
8%
540
43%
540
24%
1039
May16th to endNight
47%
563
18%
1497
10%
561
53%
561
31%
980
June1st to 15thNight
54%
540
17%
1440
10%
540
57%
540
36%
894
June16th to endNight
51%
540
17%
1440
9%
540
56%
540
35%
903
July1st to 15thNight
68%
510
19%
1360
12%
510
71%
510
44%
784
July16th to endNight
71%
564
23%
1419
17%
531
73%
531
43%
812
August1st to 15thNight
72%
527
22%
1575
23%
524
74%
524
41%
854
August16th to endNight
66%
525
21%
1748
23%
525
70%
525
33%
978
September1st to 15thNight
64%
495
28%
1650
29%
495
68%
495
36%
894
September16th to endNight
56%
594
25%
1778
17%
594
65%
594
37%
1006
October1st to 15thNight
45%
660
26%
1980
18%
660
52%
660
32%
1164
October16th to endNight
32%
704
19%
2156
11%
704
41%
704
24%
1370
November1st to 15thNight
36%
700
25%
2276
16%
700
47%
700
28%
1334
November16th to endNight
28%
864
18%
2484
9%
864
36%
864
24%
1650
December1st to 15thNight
21%
900
14%
2520
5%
900
30%
900
18%
1861
December16th to endNight
23%
960
13%
2688
5%
960
30%
960
15%
2089

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%7%35%5%3445%7%38%
47481
Night
13%7%35%424446%42%
46667
Cloud CoverDay
13%7%36%5%3445%7%38%
47489
Night
13%7%35%424446%42%
46672
TransparencyDay
44%5%13%22%12%1
47167
Night
42%412%23%14%2
46499
SeeingDay
15%7%25%27%18%5%
5857
Night
17%7%29%31%12%1
15876

By Month

Percentage Cloud Cover NE (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 15thDay
12%10%5%7%7%45%45%7%29%
1432
16th to endDay
13%14%5%10%6%3435%6%26%
1671
February1st to 15thDay
13%12%5%7%434438%31%
1575
16th to endDay
14%8%37%6%4445%6%34%
1569
March1st to 15thDay
15%7%45%5%2445%6%36%
1865
16th to endDay
18%9%36%6%2446%6%30%
2184
April1st to 15thDay
16%10%5%6%434435%34%
2151
16th to endDay
22%9%26%5%23445%33%
2160
May1st to 15thDay
19%7%46%5%345%5%7%30%
2439
16th to endDay
14%6%35%5%36%6%6%7%35%
2617
June1st to 15thDay
11%5%25%5%25%6%6%8%40%
2520
16th to endDay
10%426%5%345%5%8%43%
2520
July1st to 15thDay
7%3245%35%5%7%9%45%
2520
16th to endDay
7%3145%35%5%7%11%43%
2652
August1st to 15thDay
7%3145%35%5%7%10%43%
2289
16th to endDay
12%424433448%47%
2100
September1st to 15thDay
14%313424347%50%
1980
16th to endDay
10%425%425%5%5%7%46%
1840
October1st to 15thDay
14%6%34423335%48%
1650
16th to endDay
18%5%25%433337%41%
1716
November1st to 15thDay
11%8%445%3445%6%41%
1582
16th to endDay
18%9%45%323336%38%
1473
December1st to 15thDay
20%12%47%425%336%28%
1440
16th to endDay
18%15%5%9%6%23335%25%
1536
January1st to 15thNight
13%8%46%6%34446%36%
2506
16th to endNight
11%10%6%8%6%34346%33%
2550
February1st to 15thNight
13%10%5%6%5%24445%37%
2285
16th to endNight
13%9%36%5%2444441%
1903
March1st to 15thNight
15%8%25%5%23346%41%
2081
16th to endNight
17%8%47%5%35%45%6%32%
2040
April1st to 15thNight
17%8%35%424346%39%
1797
16th to endNight
19%8%35%423445%38%
1800
May1st to 15thNight
16%5%35%5%3345%8%37%
1509
16th to endNight
10%325%5%35%5%6%8%43%
1496
June1st to 15thNight
11%5%2442345%7%48%
1440
16th to endNight
9%423335%5%6%9%46%
1440
July1st to 15thNight
7%2124235%6%8%55%
1440
16th to endNight
5%213436%5%6%10%49%
1515
August1st to 15thNight
432442445%8%55%
1585
16th to endNight
8%42342345%6%52%
1748
September1st to 15thNight
10%42232345%7%53%
1650
16th to endNight
6%32442446%8%50%
1778
October1st to 15thNight
11%5%245%23335%52%
1980
16th to endNight
17%6%25%433335%44%
2156
November1st to 15thNight
13%5%34323236%50%
2276
16th to endNight
18%7%35%323347%40%
2484
December1st to 15thNight
19%11%47%435%34432%
2520
16th to endNight
22%12%47%5%23345%26%
2688

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 15thDay
12%10%5%7%6%5%4447%30%
1432
16th to endDay
12%14%5%10%7%3345%6%26%
1671
February1st to 15thDay
13%12%5%7%434448%31%
1575
16th to endDay
13%8%37%6%3445%7%34%
1569
March1st to 15thDay
15%7%46%5%2445%7%35%
1875
16th to endDay
18%9%36%6%3445%7%30%
2182
April1st to 15thDay
16%10%6%5%5%33445%34%
2151
16th to endDay
22%9%26%5%23446%32%
2160
May1st to 15thDay
18%7%47%6%3445%7%29%
2439
16th to endDay
13%6%35%5%36%5%6%7%35%
2617
June1st to 15thDay
11%5%25%5%35%6%6%8%40%
2520
16th to endDay
9%426%5%35%5%5%8%43%
2520
July1st to 15thDay
7%3245%36%5%7%9%45%
2520
16th to endDay
7%3145%35%5%8%10%43%
2652
August1st to 15thDay
6%425%5%346%7%11%43%
2289
16th to endDay
11%424433448%48%
2100
September1st to 15thDay
14%413433347%49%
1980
16th to endDay
10%5%25%425%5%47%46%
1840
October1st to 15thDay
14%7%24423335%48%
1650
16th to endDay
18%5%25%433346%41%
1716
November1st to 15thDay
11%8%345%2445%6%41%
1582
16th to endDay
18%9%45%324336%38%
1473
December1st to 15thDay
20%12%47%425%336%27%
1440
16th to endDay
18%14%5%9%5%23335%25%
1536
January1st to 15thNight
13%8%46%6%35%445%36%
2506
16th to endNight
11%10%6%9%5%34346%33%
2550
February1st to 15thNight
13%10%5%6%5%33345%37%
2278
16th to endNight
13%9%36%5%34435%41%
1903
March1st to 15thNight
16%7%36%423436%41%
2094
16th to endNight
17%8%47%435%447%32%
2040
April1st to 15thNight
17%8%46%423346%39%
1797
16th to endNight
19%8%35%423345%38%
1800
May1st to 15thNight
16%6%25%5%3445%8%37%
1508
16th to endNight
10%325%6%345%5%9%42%
1496
June1st to 15thNight
10%6%1442335%7%48%
1440
16th to endNight
9%423435%5%6%9%45%
1440
July1st to 15thNight
6%2123245%6%8%54%
1440
16th to endNight
5%313436%5%6%11%48%
1515
August1st to 15thNight
432443345%8%55%
1585
16th to endNight
8%42442445%7%52%
1748
September1st to 15thNight
10%42332335%7%53%
1650
16th to endNight
6%4245%3446%7%50%
1778
October1st to 15thNight
11%5%245%23335%52%
1980
16th to endNight
16%6%25%423336%44%
2156
November1st to 15thNight
13%6%24323236%50%
2276
16th to endNight
18%7%35%423347%40%
2484
December1st to 15thNight
19%11%47%43434432%
2520
16th to endNight
21%12%48%5%24345%26%
2688

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 15thDay
54%413%16%10%
1433
16th to endDay
58%313%16%7%
1671
February1st to 15thDay
52%414%22%6%
1576
16th to endDay
48%5%13%21%8%1
1569
March1st to 15thDay
47%5%16%21%8%
1875
16th to endDay
52%5%14%21%5%
2184
April1st to 15thDay
51%412%21%10%
2151
16th to endDay
52%410%19%11%1
2160
May1st to 15thDay
52%6%12%21%8%
2439
16th to endDay
44%8%13%19%13%1
2621
June1st to 15thDay
39%5%13%24%15%
2520
16th to endDay
37%6%12%23%18%1
2520
July1st to 15thDay
33%7%14%28%13%2
2371
16th to endDay
31%9%17%23%15%3
2485
August1st to 15thDay
32%8%15%26%15%1
2275
16th to endDay
34%6%12%27%15%2
2100
September1st to 15thDay
34%5%9%26%21%2
1980
16th to endDay
35%5%12%28%16%1
1840
October1st to 15thDay
39%39%26%19%1
1650
16th to endDay
43%413%25%11%1
1716
November1st to 15thDay
41%411%24%14%2
1582
16th to endDay
48%318%21%7%
1473
December1st to 15thDay
58%313%17%6%
1440
16th to endDay
62%313%12%7%
1536
January1st to 15thNight
49%414%18%13%
2506
16th to endNight
52%316%17%9%
2550
February1st to 15thNight
49%412%23%10%
2288
16th to endNight
45%313%24%10%1
1903
March1st to 15thNight
44%414%23%11%1
2094
16th to endNight
52%5%13%19%9%
2040
April1st to 15thNight
46%310%23%13%2
1797
16th to endNight
48%49%19%13%3
1800
May1st to 15thNight
44%6%13%22%12%
1509
16th to endNight
35%8%13%22%16%2
1498
June1st to 15thNight
35%312%26%19%3
1440
16th to endNight
33%7%13%22%18%4
1440
July1st to 15thNight
26%5%14%31%18%4
1360
16th to endNight
27%5%15%31%17%2
1419
August1st to 15thNight
26%5%15%31%18%3
1575
16th to endNight
31%5%9%28%19%5%
1748
September1st to 15thNight
30%410%26%25%3
1650
16th to endNight
30%412%30%19%2
1778
October1st to 15thNight
35%39%26%22%3
1980
16th to endNight
42%312%23%15%2
2156
November1st to 15thNight
36%311%24%19%4
2276
16th to endNight
44%312%27%10%
2484
December1st to 15thNight
55%311%21%7%
2520
16th to endNight
60%410%16%7%
2688

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 15thDay
27%10%37%18%41
90
16th to endDay
17%8%35%25%11%2
96
February1st to 15thDay
17%17%40%16%7%
90
16th to endDay
23%9%35%19%11%
81
March1st to 15thDay
24%15%37%17%22
90
16th to endDay
29%9%29%20%8%2
168
April1st to 15thDay
20%12%31%23%12%
270
16th to endDay
29%8%25%20%13%1
270
May1st to 15thDay
20%9%32%25%9%2
429
16th to endDay
17%9%29%25%12%5%
517
June1st to 15thDay
11%425%33%21%4
495
16th to endDay
10%8%31%27%15%6%
495
July1st to 15thDay
10%220%32%22%11%
475
16th to endDay
8%118%35%26%9%
515
August1st to 15thDay
7%119%33%29%8%
474
16th to endDay
11%312%32%30%8%
268
September1st to 15thDay
12%417%30%26%7%
255
16th to endDay
11%5%17%29%26%10%
227
October1st to 15thDay
11%8%26%26%17%8%
90
16th to endDay
21%6%35%27%9%
96
November1st to 15thDay
5%10%31%18%24%10%
90
16th to endDay
44%11%27%13%21
90
December1st to 15thDay
24%15%30%21%8%
90
16th to endDay
27%17%41%10%3
96
January1st to 15thNight
16%12%37%25%7%
900
16th to endNight
16%10%38%28%5%
960
February1st to 15thNight
18%11%37%26%6%
880
16th to endNight
19%9%37%27%5%
641
March1st to 15thNight
21%8%31%28%9%
654
16th to endNight
21%9%35%26%5%
576
April1st to 15thNight
21%10%35%26%6%
539
16th to endNight
22%8%27%32%8%
540
May1st to 15thNight
18%5%34%30%9%1
540
16th to endNight
10%430%36%17%
563
June1st to 15thNight
14%223%44%15%
540
16th to endNight
11%327%38%17%1
540
July1st to 15thNight
7%117%41%28%3
510
16th to endNight
7%12%45%31%2
564
August1st to 15thNight
5%12%43%33%4
527
16th to endNight
9%114%41%27%5%
525
September1st to 15thNight
12%215%37%27%5%
495
16th to endNight
9%422%35%25%3
594
October1st to 15thNight
13%6%29%30%19%1
660
16th to endNight
21%9%31%28%8%
704
November1st to 15thNight
16%10%32%29%10%
700
16th to endNight
21%11%33%25%7%
864
December1st to 15thNight
24%10%36%23%5%
900
16th to endNight
28%9%30%27%4
960
Page generated at 2017-08-13 13:16:31. Version ac04

Copyright 2017 A. Danko


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