Dulaney Springs Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dulaney Springs Park clear sky chart from 2005-11-05 to 2018-02-14.

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
34%
15779
21%
48826
10%
15739
46%
15739
24%
30429

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%
778
21%
2667
8%
776
38%
776
17%
1633
January16th to endNight
17%
832
24%
2704
7%
832
37%
832
20%
1668
February1st to 15thNight
16%
760
18%
2468
4%
757
34%
757
18%
1565
February16th to endNight
18%
631
24%
1902
5%
631
40%
631
19%
1183
March1st to 15thNight
23%
720
21%
2034
8%
720
37%
720
22%
1296
March16th to endNight
21%
768
21%
2070
8%
768
33%
768
23%
1374
April1st to 15thNight
22%
718
20%
1796
4%
718
30%
718
26%
1190
April16th to endNight
32%
720
19%
1800
4%
720
39%
720
28%
1208
May1st to 15thNight
34%
535
17%
1615
9%
535
42%
535
22%
1079
May16th to endNight
48%
374
16%
1497
13%
374
55%
374
21%
898
June1st to 15thNight
51%
360
18%
1440
17%
360
60%
360
24%
819
June16th to endNight
53%
360
17%
1440
17%
360
61%
360
26%
823
July1st to 15thNight
54%
340
12%
1360
13%
340
56%
340
19%
863
July16th to endNight
67%
497
16%
1529
13%
465
72%
465
33%
865
August1st to 15thNight
60%
545
19%
1615
13%
542
62%
542
30%
1002
August16th to endNight
59%
764
20%
1910
11%
764
61%
764
35%
1234
September1st to 15thNight
52%
720
25%
1800
13%
720
58%
720
34%
1164
September16th to endNight
54%
717
26%
1962
20%
717
59%
717
33%
1252
October1st to 15thNight
41%
720
22%
2160
17%
720
51%
720
25%
1380
October16th to endNight
34%
768
29%
2304
16%
768
52%
768
30%
1321
November1st to 15thNight
34%
760
24%
2449
12%
760
49%
760
24%
1480
November16th to endNight
28%
780
24%
2662
12%
780
45%
780
21%
1570
December1st to 15thNight
24%
780
17%
2730
5%
780
38%
780
16%
1750
December16th to endNight
19%
832
21%
2912
5%
832
37%
832
18%
1812

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%5%25%5%3445%7%40%
49244
Night
14%5%2442445%7%44%
49007
Cloud CoverDay
14%5%25%5%345%5%7%40%
49254
Night
14%5%2442445%7%43%
49011
TransparencyDay
40%5%12%23%15%2
48943
Night
39%411%23%17%3
48826
SeeingDay
18%12%26%23%13%4
6132
Night
18%12%28%26%12%1
15782

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
15%6%244345%47%39%
1600
16th to endDay
13%8%345%2445%6%41%
1872
February1st to 15thDay
14%7%25%5%2446%6%38%
1695
16th to endDay
13%7%35%5%34447%40%
1569
March1st to 15thDay
15%6%25%423436%43%
1914
16th to endDay
17%6%35%5%34345%40%
2154
April1st to 15thDay
16%4245%3335%7%41%
2152
16th to endDay
17%325%42445%6%43%
2160
May1st to 15thDay
18%5%345%3446%7%36%
2346
16th to endDay
15%415%5%35%5%5%9%37%
2618
June1st to 15thDay
12%425%6%345%6%10%38%
2520
16th to endDay
11%4245%35%5%6%9%42%
2520
July1st to 15thDay
9%425%5%35%6%7%9%38%
2520
16th to endDay
6%425%6%37%7%9%10%36%
2531
August1st to 15thDay
11%415%6%47%6%6%7%38%
2322
16th to endDay
11%4245%35%6%7%8%40%
2292
September1st to 15thDay
14%4245%14448%44%
2160
16th to endDay
15%5%25%43445%7%41%
1993
October1st to 15thDay
18%5%1343345%5%43%
1800
16th to endDay
15%5%15%423445%47%
1920
November1st to 15thDay
15%5%24424446%45%
1737
16th to endDay
17%5%23433345%45%
1625
December1st to 15thDay
16%6%25%42445%6%40%
1560
16th to endDay
16%6%25%5%3445%6%38%
1664
January1st to 15thNight
16%6%25%42445%6%41%
2667
16th to endNight
16%6%24424345%44%
2704
February1st to 15thNight
14%8%25%424346%42%
2466
16th to endNight
13%5%35%5%33437%44%
1902
March1st to 15thNight
16%5%13425%446%44%
2022
16th to endNight
14%5%345%34346%43%
2070
April1st to 15thNight
14%6%3432445%7%42%
1796
16th to endNight
16%5%3342435%6%44%
1800
May1st to 15thNight
21%6%23424346%39%
1615
16th to endNight
14%5%2443345%8%43%
1495
June1st to 15thNight
11%4244335%6%9%45%
1440
16th to endNight
9%424435%6%7%10%42%
1440
July1st to 15thNight
8%5%37%6%47%6%6%9%35%
1440
16th to endNight
5%314436%6%5%11%48%
1635
August1st to 15thNight
10%4245%35%46%8%44%
1626
16th to endNight
12%425%32346%8%46%
1910
September1st to 15thNight
12%5%25%32435%7%47%
1800
16th to endNight
12%6%24434346%46%
1962
October1st to 15thNight
19%424423346%44%
2160
16th to endNight
15%312323336%52%
2304
November1st to 15thNight
13%6%24423345%49%
2449
16th to endNight
15%424324346%45%
2662
December1st to 15thNight
17%5%25%5%35%45%6%38%
2730
16th to endNight
17%5%245%2345%7%40%
2912

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
15%6%24435%46%6%40%
1600
16th to endDay
14%7%25%5%3445%6%41%
1872
February1st to 15thDay
15%7%25%43446%6%39%
1695
16th to endDay
14%7%36%434447%40%
1569
March1st to 15thDay
15%5%25%423446%43%
1925
16th to endDay
17%6%35%5%34345%40%
2153
April1st to 15thDay
15%4245%25%35%7%42%
2152
16th to endDay
17%424423446%43%
2160
May1st to 15thDay
18%5%345%245%5%7%36%
2346
16th to endDay
15%425%5%35%5%6%9%37%
2618
June1st to 15thDay
12%425%5%345%5%11%38%
2520
16th to endDay
11%424435%5%5%9%42%
2520
July1st to 15thDay
8%425%5%35%6%7%10%38%
2520
16th to endDay
5%4246%37%7%8%11%37%
2531
August1st to 15thDay
11%4246%46%6%6%8%37%
2322
16th to endDay
11%4145%35%7%6%8%40%
2292
September1st to 15thDay
14%425%5%2435%7%45%
2160
16th to endDay
15%5%25%434448%40%
1993
October1st to 15thDay
19%5%14423446%43%
1800
16th to endDay
15%4244125%45%47%
1920
November1st to 15thDay
14%5%25%32445%6%45%
1737
16th to endDay
16%5%24433345%46%
1625
December1st to 15thDay
17%5%25%42445%6%40%
1560
16th to endDay
17%6%25%444447%38%
1664
January1st to 15thNight
17%5%25%32445%7%41%
2667
16th to endNight
17%6%2442435%5%44%
2704
February1st to 15thNight
14%7%25%5%24346%42%
2459
16th to endNight
13%5%25%424446%45%
1902
March1st to 15thNight
16%5%13324447%44%
2034
16th to endNight
14%6%246%24345%43%
2070
April1st to 15thNight
14%6%2432445%7%42%
1796
16th to endNight
17%433324447%44%
1800
May1st to 15thNight
21%5%2442345%6%39%
1614
16th to endNight
15%5%2442345%8%42%
1495
June1st to 15thNight
11%4135%3446%8%45%
1440
16th to endNight
9%4245%246%7%9%42%
1440
July1st to 15thNight
8%6%36%7%45%6%7%8%35%
1440
16th to endNight
5%314436%6%5%11%47%
1635
August1st to 15thNight
10%4245%25%45%9%44%
1626
16th to endNight
12%42432346%7%45%
1910
September1st to 15thNight
12%6%2442335%6%47%
1800
16th to endNight
13%6%24433347%45%
1962
October1st to 15thNight
18%5%24413445%44%
2160
16th to endNight
15%313313336%52%
2304
November1st to 15thNight
13%6%24423345%49%
2449
16th to endNight
15%425%324347%45%
2662
December1st to 15thNight
17%6%25%435%45%6%38%
2730
16th to endNight
17%5%345%2345%7%40%
2912

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
42%413%22%12%3
1601
16th to endDay
43%312%24%12%3
1872
February1st to 15thDay
44%411%26%11%2
1697
16th to endDay
43%212%27%12%2
1569
March1st to 15thDay
41%312%24%15%2
1925
16th to endDay
46%39%19%17%2
2154
April1st to 15thDay
41%311%21%17%3
2152
16th to endDay
39%49%19%21%5%
2160
May1st to 15thDay
45%6%11%20%14%1
2346
16th to endDay
42%7%14%21%12%1
2622
June1st to 15thDay
39%6%14%25%13%1
2520
16th to endDay
36%7%14%21%18%1
2520
July1st to 15thDay
37%7%14%22%14%3
2371
16th to endDay
35%9%15%24%13%1
2374
August1st to 15thDay
41%6%11%21%17%1
2309
16th to endDay
37%6%12%24%16%2
2292
September1st to 15thDay
38%411%21%21%2
2160
16th to endDay
41%47%23%20%2
1993
October1st to 15thDay
40%411%22%17%2
1800
16th to endDay
37%310%28%19%1
1920
November1st to 15thDay
39%412%22%18%4
1737
16th to endDay
40%210%28%15%2
1625
December1st to 15thDay
43%315%24%11%2
1560
16th to endDay
45%413%22%13%
1664
January1st to 15thNight
41%310%21%16%4
2667
16th to endNight
41%210%27%15%1
2704
February1st to 15thNight
43%312%23%14%2
2468
16th to endNight
40%211%24%19%2
1902
March1st to 15thNight
40%312%26%14%1
2034
16th to endNight
42%311%21%17%3
2070
April1st to 15thNight
40%311%21%19%3
1796
16th to endNight
39%5%9%19%19%6%
1800
May1st to 15thNight
45%411%21%14%2
1615
16th to endNight
38%7%16%18%14%3
1497
June1st to 15thNight
36%6%13%26%16%1
1440
16th to endNight
35%6%12%26%16%2
1440
July1st to 15thNight
43%7%14%18%11%4
1360
16th to endNight
28%8%18%23%18%2
1529
August1st to 15thNight
35%6%12%24%18%2
1615
16th to endNight
35%5%11%24%19%3
1910
September1st to 15thNight
36%410%23%21%3
1800
16th to endNight
38%38%22%23%3
1962
October1st to 15thNight
42%310%23%18%2
2160
16th to endNight
33%29%30%21%2
2304
November1st to 15thNight
38%38%24%18%6%
2449
16th to endNight
38%39%25%19%2
2662
December1st to 15thNight
46%312%23%12%1
2730
16th to endNight
43%315%23%12%1
2912

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
28%29%24%11%3
101
16th to endDay
22%29%35%10%2
144
February1st to 15thDay
32%27%36%3
130
16th to endDay
17%25%39%14%2
228
March1st to 15thDay
21%21%30%22%4
270
16th to endDay
23%18%36%14%5%2
288
April1st to 15thDay
20%16%35%19%6%2
270
16th to endDay
23%9%34%15%12%4
270
May1st to 15thDay
30%17%24%14%9%3
288
16th to endDay
22%5%25%26%16%2
331
June1st to 15thDay
16%9%26%26%17%3
315
16th to endDay
14%11%28%29%12%3
315
July1st to 15thDay
13%424%33%19%5%
305
16th to endDay
7%321%34%25%7%
326
August1st to 15thDay
13%420%31%20%9%
313
16th to endDay
10%20%32%20%14%
332
September1st to 15thDay
15%9%19%23%20%12%
315
16th to endDay
18%6%16%30%17%10%
314
October1st to 15thDay
26%5%20%23%18%5%
315
16th to endDay
14%17%28%22%14%2
336
November1st to 15thDay
16%14%30%21%15%2
285
16th to endDay
19%22%30%18%7%
155
December1st to 15thDay
21%27%22%21%5%2
90
16th to endDay
26%22%34%12%4
96
January1st to 15thNight
22%18%32%21%4
780
16th to endNight
22%19%36%18%2
832
February1st to 15thNight
22%18%36%20%2
760
16th to endNight
22%23%32%19%1
631
March1st to 15thNight
23%18%31%22%4
720
16th to endNight
18%18%37%19%5%1
768
April1st to 15thNight
18%20%36%19%4
718
16th to endNight
20%13%28%25%11%
720
May1st to 15thNight
24%9%26%28%9%1
535
16th to endNight
18%9%18%34%18%
375
June1st to 15thNight
11%425%36%20%1
360
16th to endNight
10%324%45%16%
360
July1st to 15thNight
10%5%17%39%25%
340
16th to endNight
6%216%42%27%4
497
August1st to 15thNight
13%214%41%25%2
545
16th to endNight
14%216%34%27%4
764
September1st to 15thNight
14%6%20%29%26%2
720
16th to endNight
16%319%30%26%4
717
October1st to 15thNight
22%8%20%27%17%4
720
16th to endNight
19%13%29%24%12%
768
November1st to 15thNight
17%13%28%27%10%2
760
16th to endNight
18%18%30%24%7%
780
December1st to 15thNight
21%16%32%19%8%
780
16th to endNight
21%17%37%21%2
832
Page generated at 2018-02-15 10:58:52. Version ac04

Copyright 2018 A. Danko


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