Doran Planetarium
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Doran Planetarium clear sky chart from 2005-11-05 to 2019-06-02.

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
30%
17444
13%
53766
8%
17405
36%
17405
17%
38564

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
20%
1049
9%
3132
4%
1045
25%
1045
11%
2502
January16th to endNight
25%
1016
11%
3032
5%
1016
30%
1016
12%
2371
February1st to 15thNight
21%
823
12%
2677
5%
821
28%
821
11%
2015
February16th to endNight
23%
735
11%
2333
4%
735
31%
735
12%
1768
March1st to 15thNight
22%
840
12%
2366
6%
840
28%
840
17%
1726
March16th to endNight
30%
896
19%
2464
9%
896
40%
896
25%
1651
April1st to 15thNight
27%
759
15%
2073
7%
759
32%
759
19%
1507
April16th to endNight
32%
624
16%
1870
8%
624
39%
624
21%
1294
May1st to 15thNight
34%
555
14%
1815
9%
555
42%
555
19%
1236
May16th to endNight
34%
439
13%
1697
10%
438
46%
438
21%
1034
June1st to 15thNight
36%
392
11%
1372
10%
392
42%
392
20%
890
June16th to endNight
42%
390
10%
1365
8%
390
47%
390
23%
843
July1st to 15thNight
47%
370
17%
1295
15%
370
54%
370
33%
715
July16th to endNight
52%
498
14%
1507
12%
469
55%
469
29%
917
August1st to 15thNight
49%
575
14%
1715
11%
572
53%
572
28%
1118
August16th to endNight
50%
621
18%
1863
11%
621
55%
621
28%
1182
September1st to 15thNight
45%
767
19%
1995
11%
767
48%
767
32%
1286
September16th to endNight
43%
777
20%
2145
13%
777
47%
777
28%
1434
October1st to 15thNight
31%
780
16%
2333
11%
780
38%
780
19%
1658
October16th to endNight
23%
832
13%
2571
6%
832
31%
832
12%
1972
November1st to 15thNight
26%
820
13%
2820
9%
820
33%
820
14%
2049
November16th to endNight
23%
840
10%
2940
7%
840
29%
840
10%
2286
December1st to 15thNight
19%
926
9%
3026
3%
926
26%
926
9%
2386
December16th to endNight
21%
1120
9%
3360
5%
1120
25%
1120
9%
2724

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
17%9%36%6%3445%6%31%
54579
Night
16%10%46%6%3445%6%32%
53928
Cloud CoverDay
17%9%36%6%34446%31%
54589
Night
16%10%46%6%34446%31%
53932
TransparencyDay
52%5%11%20%9%
54259
Night
52%5%11%19%9%1
53766
SeeingDay
21%11%29%23%10%3
8008
Night
22%9%29%27%9%
17446

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
19%16%6%7%5%34336%23%
1463
16th to endDay
16%15%5%9%7%4445%5%21%
1893
February1st to 15thDay
11%16%48%8%35%45%6%24%
1845
16th to endDay
14%17%5%10%7%345%3425%
1712
March1st to 15thDay
16%11%37%5%34336%33%
2243
16th to endDay
12%7%46%5%23445%42%
2464
April1st to 15thDay
20%9%46%5%24445%30%
2546
16th to endDay
21%7%24423436%39%
2695
May1st to 15thDay
18%8%36%6%23447%34%
2794
16th to endDay
17%6%25%5%35%5%5%7%36%
3118
June1st to 15thDay
14%7%47%6%345%6%7%32%
2941
16th to endDay
15%6%36%6%35%5%5%7%32%
2925
July1st to 15thDay
12%5%36%435%45%9%40%
2925
16th to endDay
12%6%26%6%46%5%6%7%35%
2914
August1st to 15thDay
14%7%26%5%35%5%5%8%33%
2487
16th to endDay
14%6%26%5%345%5%8%36%
2691
September1st to 15thDay
13%7%26%6%2435%7%39%
2278
16th to endDay
20%5%26%43345%6%38%
2145
October1st to 15thDay
20%9%26%6%25%446%31%
1957
16th to endDay
27%11%48%5%3344421%
2004
November1st to 15thDay
20%12%48%6%34346%26%
1698
16th to endDay
22%18%48%7%3433420%
1680
December1st to 15thDay
16%19%5%8%7%34445%18%
1593
16th to endDay
19%16%6%9%7%26%34417%
1568
January1st to 15thNight
19%15%5%8%6%35%345%22%
3132
16th to endNight
14%14%6%8%7%35%45%6%21%
3032
February1st to 15thNight
12%13%5%9%9%35%5%5%5%25%
2675
16th to endNight
15%14%5%8%6%4435%5%25%
2333
March1st to 15thNight
15%10%48%6%3445%6%31%
2354
16th to endNight
12%7%36%5%2435%5%41%
2464
April1st to 15thNight
18%10%47%5%24346%32%
2073
16th to endNight
19%7%25%5%34445%36%
1870
May1st to 15thNight
15%7%36%6%35%45%6%34%
1815
16th to endNight
13%5%35%5%3445%8%40%
1695
June1st to 15thNight
13%6%45%436%5%5%7%37%
1372
16th to endNight
11%435%43446%8%41%
1365
July1st to 15thNight
9%42342446%9%48%
1365
16th to endNight
8%5%244345%6%9%44%
1604
August1st to 15thNight
12%6%36%42445%5%44%
1726
16th to endNight
11%5%25%425%5%47%44%
1863
September1st to 15thNight
12%5%1433445%6%46%
1995
16th to endNight
14%5%35%5%35%347%43%
2145
October1st to 15thNight
22%8%35%5%23445%34%
2333
16th to endNight
25%11%36%5%34435%25%
2571
November1st to 15thNight
18%11%37%6%3445%6%28%
2820
16th to endNight
23%13%46%6%3345%5%23%
2940
December1st to 15thNight
18%16%5%8%7%34445%22%
3026
16th to endNight
21%14%6%8%6%35%445%18%
3360

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
19%16%6%8%5%34345%23%
1463
16th to endDay
16%15%6%8%7%4435%5%21%
1893
February1st to 15thDay
11%16%5%8%8%35%446%24%
1845
16th to endDay
14%17%5%9%6%345%3425%
1712
March1st to 15thDay
16%11%37%5%33336%33%
2254
16th to endDay
12%8%37%5%23345%41%
2463
April1st to 15thDay
21%10%36%5%2445%6%30%
2546
16th to endDay
22%7%24323336%38%
2695
May1st to 15thDay
19%8%36%5%24446%34%
2794
16th to endDay
17%6%25%435%46%7%36%
3118
June1st to 15thDay
14%8%36%6%345%6%8%32%
2941
16th to endDay
15%7%36%6%35%5%5%7%32%
2925
July1st to 15thDay
12%5%26%425%45%8%40%
2925
16th to endDay
12%6%25%7%35%6%6%7%35%
2914
August1st to 15thDay
15%6%35%5%35%5%6%8%33%
2487
16th to endDay
14%6%36%5%345%5%8%36%
2691
September1st to 15thDay
14%6%36%6%24448%39%
2278
16th to endDay
20%5%25%434446%37%
2145
October1st to 15thDay
20%9%36%6%24437%30%
1957
16th to endDay
27%12%38%6%33435%21%
2004
November1st to 15thDay
21%11%48%6%23346%26%
1698
16th to endDay
22%17%5%7%7%3433320%
1680
December1st to 15thDay
17%18%6%9%6%34445%18%
1593
16th to endDay
19%16%7%8%7%25%446%17%
1568
January1st to 15thNight
19%15%5%8%6%34345%22%
3132
16th to endNight
14%14%7%8%7%35%36%6%21%
3032
February1st to 15thNight
12%13%5%8%9%345%5%5%24%
2668
16th to endNight
15%14%5%8%6%44445%25%
2333
March1st to 15thNight
16%10%5%7%6%2435%5%31%
2366
16th to endNight
13%7%36%5%2435%5%41%
2464
April1st to 15thNight
18%10%46%5%24336%32%
2073
16th to endNight
19%8%345%34445%36%
1870
May1st to 15thNight
15%7%35%6%36%45%5%35%
1814
16th to endNight
13%5%35%43445%7%41%
1695
June1st to 15thNight
13%6%36%446%5%5%7%37%
1372
16th to endNight
10%5%35%5%2446%9%41%
1365
July1st to 15thNight
9%42432445%9%48%
1365
16th to endNight
9%4243445%5%9%45%
1604
August1st to 15thNight
12%5%35%5%24446%43%
1726
16th to endNight
11%5%25%435%45%7%44%
1863
September1st to 15thNight
13%5%15%43345%7%46%
1995
16th to endNight
15%425%434338%42%
2145
October1st to 15thNight
22%9%35%433345%34%
2333
16th to endNight
26%10%36%5%34435%25%
2571
November1st to 15thNight
18%12%37%6%3445%6%28%
2820
16th to endNight
23%13%46%6%34445%23%
2940
December1st to 15thNight
19%16%48%7%34345%22%
3026
16th to endNight
20%14%6%8%6%35%445%18%
3360

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
63%310%15%6%
1464
16th to endDay
64%46%15%7%1
1893
February1st to 15thDay
59%5%12%16%5%
1847
16th to endDay
61%47%16%9%
1712
March1st to 15thDay
53%313%17%11%
2254
16th to endDay
44%39%26%12%3
2464
April1st to 15thDay
54%411%18%10%1
2546
16th to endDay
47%38%22%14%2
2695
May1st to 15thDay
49%410%21%12%2
2794
16th to endDay
45%5%13%21%13%
3122
June1st to 15thDay
48%6%11%20%12%
2941
16th to endDay
49%7%11%20%10%1
2925
July1st to 15thDay
38%7%11%27%15%1
2766
16th to endDay
45%7%12%24%10%
2748
August1st to 15thDay
45%7%16%19%9%
2474
16th to endDay
44%6%15%28%5%
2691
September1st to 15thDay
43%5%15%24%10%
2278
16th to endDay
46%6%15%24%6%
2145
October1st to 15thDay
53%6%11%18%10%
1957
16th to endDay
65%5%11%10%6%
2004
November1st to 15thDay
59%5%11%15%8%
1698
16th to endDay
69%48%12%4
1680
December1st to 15thDay
67%6%8%14%3
1593
16th to endDay
68%48%12%5%
1568
January1st to 15thNight
64%5%9%14%6%
3132
16th to endNight
62%5%8%15%7%
3032
February1st to 15thNight
59%5%12%16%5%
2677
16th to endNight
60%411%16%7%
2333
March1st to 15thNight
54%412%18%9%1
2366
16th to endNight
43%410%19%17%4
2464
April1st to 15thNight
53%38%19%13%1
2073
16th to endNight
49%39%18%17%2
1870
May1st to 15thNight
48%5%10%21%12%1
1815
16th to endNight
40%6%12%23%15%1
1697
June1st to 15thNight
43%7%12%22%12%2
1372
16th to endNight
38%7%15%21%14%2
1365
July1st to 15thNight
30%6%13%31%15%2
1295
16th to endNight
35%6%17%26%12%
1507
August1st to 15thNight
40%6%18%22%11%1
1715
16th to endNight
37%7%16%26%10%
1863
September1st to 15thNight
36%6%15%28%10%1
1995
16th to endNight
41%6%12%31%8%
2145
October1st to 15thNight
51%412%20%10%
2333
16th to endNight
60%5%10%17%6%
2571
November1st to 15thNight
54%6%13%18%7%
2820
16th to endNight
62%5%11%14%5%
2940
December1st to 15thNight
63%5%10%15%4
3026
16th to endNight
66%5%7%13%6%
3360

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
31%16%28%17%41
120
16th to endDay
29%7%30%21%8%1
192
February1st to 15thDay
28%17%33%18%2
180
16th to endDay
27%16%35%19%1
159
March1st to 15thDay
23%14%31%23%7%
334
16th to endDay
17%10%34%25%8%2
416
April1st to 15thDay
28%12%25%22%9%1
390
16th to endDay
29%10%25%18%10%4
379
May1st to 15thDay
24%8%28%22%12%3
408
16th to endDay
23%15%29%20%8%2
511
June1st to 15thDay
19%15%32%24%6%1
576
16th to endDay
17%14%32%23%10%2
570
July1st to 15thDay
10%12%32%27%12%3
550
16th to endDay
12%7%31%29%12%6%
517
August1st to 15thDay
15%5%23%29%17%9%
358
16th to endDay
19%5%25%21%17%10%
396
September1st to 15thDay
14%7%25%26%17%8%
375
16th to endDay
23%9%24%25%10%6%
374
October1st to 15thDay
23%15%29%20%9%1
375
16th to endDay
28%16%31%17%31
324
November1st to 15thDay
32%11%35%16%2
136
16th to endDay
28%15%35%15%6%
120
December1st to 15thDay
30%13%29%20%7%
120
16th to endDay
30%12%32%19%5%
128
January1st to 15thNight
26%12%28%23%7%
1050
16th to endNight
22%10%28%29%8%
1016
February1st to 15thNight
19%13%34%27%4
824
16th to endNight
23%13%29%27%5%
735
March1st to 15thNight
23%15%30%23%7%
840
16th to endNight
17%10%34%26%9%
896
April1st to 15thNight
23%13%30%27%5%
759
16th to endNight
24%9%28%27%9%
624
May1st to 15thNight
19%6%30%32%9%
555
16th to endNight
14%9%37%30%7%
439
June1st to 15thNight
18%6%31%33%9%
392
16th to endNight
12%5%32%35%14%
390
July1st to 15thNight
9%335%41%9%1
370
16th to endNight
11%227%40%17%1
498
August1st to 15thNight
13%423%35%21%2
575
16th to endNight
15%323%34%21%1
621
September1st to 15thNight
16%5%27%27%21%2
767
16th to endNight
18%5%27%29%15%3
777
October1st to 15thNight
27%7%27%26%10%
780
16th to endNight
32%11%26%23%4
832
November1st to 15thNight
24%11%29%25%7%
820
16th to endNight
31%11%25%22%8%
840
December1st to 15thNight
28%13%29%22%5%
926
16th to endNight
29%13%25%24%7%
1120
Page generated at 2019-06-02 19:43:06. Version ac04

Copyright 2019 A. Danko


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