Hampton-Harmon Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hampton-Harmon Observatory clear sky chart from 2005-11-05 to 2019-06-10.

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
49%
18150
22%
53871
15%
18112
56%
18112
28%
34207

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
30%
838
24%
2717
11%
836
46%
836
25%
1640
January16th to endNight
31%
896
25%
2912
14%
896
46%
896
28%
1753
February1st to 15thNight
32%
821
21%
2674
11%
821
46%
821
25%
1632
February16th to endNight
28%
735
25%
2150
12%
735
43%
735
27%
1356
March1st to 15thNight
34%
840
26%
2310
13%
840
45%
840
29%
1474
March16th to endNight
39%
896
20%
2464
12%
896
45%
896
26%
1642
April1st to 15thNight
39%
838
22%
2208
10%
838
47%
838
33%
1403
April16th to endNight
45%
758
22%
2004
11%
758
51%
758
31%
1298
May1st to 15thNight
51%
630
17%
1890
9%
630
57%
630
27%
1240
May16th to endNight
63%
657
16%
1972
13%
657
64%
657
27%
1295
June1st to 15thNight
66%
612
16%
1836
14%
612
68%
612
27%
1212
June16th to endNight
71%
585
17%
1755
16%
585
72%
585
30%
1110
July1st to 15thNight
74%
555
14%
1665
14%
555
74%
555
27%
1092
July16th to endNight
73%
612
14%
1739
13%
579
74%
579
27%
1138
August1st to 15thNight
67%
575
14%
1715
14%
572
67%
572
23%
1208
August16th to endNight
71%
737
16%
1979
14%
737
72%
737
29%
1338
September1st to 15thNight
66%
780
20%
2072
16%
780
67%
780
29%
1369
September16th to endNight
54%
777
19%
2145
16%
777
57%
777
23%
1509
October1st to 15thNight
57%
780
27%
2314
26%
780
62%
780
31%
1422
October16th to endNight
50%
832
33%
2496
23%
832
65%
832
38%
1395
November1st to 15thNight
48%
820
27%
2482
21%
820
57%
820
31%
1486
November16th to endNight
46%
840
28%
2730
21%
840
57%
840
32%
1543
December1st to 15thNight
37%
840
23%
2730
14%
840
49%
840
23%
1746
December16th to endNight
36%
896
21%
2912
14%
896
46%
896
22%
1906

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
13%5%2443445%8%43%
54637
Night
14%42442445%7%44%
54068
TransparencyDay
38%7%12%21%16%3
54338
Night
38%6%11%20%18%4
53871
SeeingDay
16%419%23%21%14%
7937
Night
16%422%32%21%2
18157

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 15thDay
18%5%24423436%43%
1881
16th to endDay
14%5%24323336%49%
2016
February1st to 15thDay
16%6%2342345%6%44%
1847
16th to endDay
17%5%33423347%43%
1893
March1st to 15thDay
16%41332335%7%46%
2310
16th to endDay
16%5%25%423446%44%
2463
April1st to 15thDay
12%41332345%8%50%
2400
16th to endDay
14%324435%446%45%
2572
May1st to 15thDay
13%5%245%35%5%6%8%39%
2721
16th to endDay
12%4246%345%6%8%41%
2847
June1st to 15thDay
9%415%5%35%6%7%10%39%
2652
16th to endDay
6%415%436%6%7%11%40%
2535
July1st to 15thDay
9%426%6%47%6%7%10%34%
2535
16th to endDay
7%436%6%47%7%7%10%32%
2673
August1st to 15thDay
11%5%26%6%36%6%7%10%31%
2487
16th to endDay
10%426%5%35%6%7%10%36%
2561
September1st to 15thDay
12%41443447%9%43%
2216
16th to endDay
17%6%2443445%7%37%
2145
October1st to 15thDay
14%5%14322345%52%
1975
16th to endDay
13%31422323458%
2080
November1st to 15thDay
15%413322335%53%
2032
16th to endDay
13%423423346%51%
1890
December1st to 15thDay
18%6%22333447%43%
1890
16th to endDay
22%6%24313346%41%
2016
January1st to 15thNight
16%5%23423335%48%
2717
16th to endNight
16%424323335%49%
2912
February1st to 15thNight
16%424324446%46%
2665
16th to endNight
16%5%24424346%46%
2150
March1st to 15thNight
15%6%14324345%47%
2310
16th to endNight
17%414434446%44%
2464
April1st to 15thNight
13%414423348%47%
2208
16th to endNight
14%5%24424346%47%
2004
May1st to 15thNight
12%5%25%435%45%8%41%
1889
16th to endNight
10%5%25%4345%7%9%39%
1970
June1st to 15thNight
10%3245%35%5%8%12%37%
1836
16th to endNight
7%325%5%35%6%7%11%42%
1755
July1st to 15thNight
8%425%446%7%8%11%37%
1755
16th to endNight
7%415%6%46%6%9%12%35%
1847
August1st to 15thNight
11%5%25%6%45%6%7%10%33%
1726
16th to endNight
8%5%25%5%346%7%10%39%
1979
September1st to 15thNight
10%425%5%35%5%6%8%43%
2072
16th to endNight
16%6%25%5%35%46%6%36%
2145
October1st to 15thNight
13%5%24424346%49%
2314
16th to endNight
11%42332332459%
2496
November1st to 15thNight
16%5%1332323452%
2482
16th to endNight
13%413324346%52%
2730
December1st to 15thNight
18%6%25%423435%43%
2730
16th to endNight
22%5%24423446%39%
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
41%47%21%19%5%
1882
16th to endDay
36%47%23%20%7%
2016
February1st to 15thDay
39%5%9%20%19%4
1849
16th to endDay
40%5%11%21%16%4
1893
March1st to 15thDay
37%49%22%20%6%
2310
16th to endDay
40%7%10%20%18%3
2464
April1st to 15thDay
32%5%11%25%18%5%
2400
16th to endDay
38%6%11%19%17%7%
2572
May1st to 15thDay
40%8%16%20%11%3
2721
16th to endDay
38%9%14%23%11%2
2851
June1st to 15thDay
36%10%16%23%12%
2652
16th to endDay
34%10%17%20%14%2
2535
July1st to 15thDay
41%11%15%16%11%3
2396
16th to endDay
41%11%17%19%8%
2518
August1st to 15thDay
43%11%16%19%8%
2474
16th to endDay
39%12%16%19%10%1
2561
September1st to 15thDay
36%9%15%18%17%3
2216
16th to endDay
46%7%9%16%18%2
2145
October1st to 15thDay
34%5%10%24%20%5%
1975
16th to endDay
31%36%25%24%8%
2080
November1st to 15thDay
35%38%17%26%7%
2032
16th to endDay
33%48%22%25%4
1890
December1st to 15thDay
41%5%8%21%18%4
1890
16th to endDay
44%311%19%17%3
2016
January1st to 15thNight
38%49%16%23%7%
2717
16th to endNight
38%37%22%21%6%
2912
February1st to 15thNight
39%49%21%20%4
2674
16th to endNight
39%311%21%19%4
2150
March1st to 15thNight
38%47%20%21%7%
2310
16th to endNight
40%6%8%20%18%4
2464
April1st to 15thNight
35%5%10%23%20%4
2208
16th to endNight
38%411%18%18%8%
2004
May1st to 15thNight
39%8%14%21%15%1
1890
16th to endNight
37%10%14%24%11%1
1972
June1st to 15thNight
37%10%15%22%12%1
1836
16th to endNight
33%10%18%20%13%3
1755
July1st to 15thNight
35%12%16%20%12%3
1665
16th to endNight
35%12%21%19%8%2
1739
August1st to 15thNight
41%12%16%16%11%1
1715
16th to endNight
36%11%18%22%9%1
1979
September1st to 15thNight
36%9%14%19%15%4
2072
16th to endNight
46%7%10%15%17%2
2145
October1st to 15thNight
36%5%8%24%19%5%
2314
16th to endNight
30%36%23%27%9%
2496
November1st to 15thNight
36%37%18%23%10%
2482
16th to endNight
32%47%21%26%6%
2730
December1st to 15thNight
42%5%9%18%18%5%
2730
16th to endNight
45%49%18%18%3
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
21%11%36%22%8%
180
16th to endDay
18%15%34%21%9%1
192
February1st to 15thDay
21%9%38%21%10%
180
16th to endDay
26%7%35%23%7%
212
March1st to 15thDay
22%8%33%26%8%
390
16th to endDay
16%7%32%30%11%
416
April1st to 15thDay
18%9%25%25%17%2
390
16th to endDay
16%422%25%23%7%
379
May1st to 15thDay
15%421%26%20%11%
408
16th to endDay
19%111%18%29%20%
459
June1st to 15thDay
12%13%19%31%21%
411
16th to endDay
8%9%28%27%25%
375
July1st to 15thDay
10%6%21%29%31%
365
16th to endDay
8%16%20%33%30%
390
August1st to 15thDay
15%7%19%29%26%
358
16th to endDay
11%5%21%28%32%
396
September1st to 15thDay
15%18%15%28%30%
375
16th to endDay
24%111%21%26%14%
374
October1st to 15thDay
18%115%28%22%13%
375
16th to endDay
13%5%21%30%22%7%
400
November1st to 15thDay
24%422%26%16%6%
360
16th to endDay
8%6%30%22%22%9%
180
December1st to 15thDay
23%7%26%30%10%1
180
16th to endDay
29%8%29%26%6%
192
January1st to 15thNight
19%9%34%29%7%
840
16th to endNight
18%7%38%30%4
896
February1st to 15thNight
20%9%33%33%3
824
16th to endNight
19%11%36%29%3
735
March1st to 15thNight
19%7%35%32%5%
840
16th to endNight
18%6%29%35%8%
896
April1st to 15thNight
15%8%31%32%11%
838
16th to endNight
17%6%26%33%15%
758
May1st to 15thNight
12%423%35%22%1
630
16th to endNight
12%113%33%35%3
659
June1st to 15thNight
11%11%33%36%5%
612
16th to endNight
7%9%31%46%4
585
July1st to 15thNight
9%16%30%46%5%
555
16th to endNight
8%5%29%44%11%
612
August1st to 15thNight
13%17%28%42%7%
575
16th to endNight
10%6%27%45%9%
737
September1st to 15thNight
11%19%30%38%8%
780
16th to endNight
19%214%27%32%3
777
October1st to 15thNight
16%317%30%27%5%
780
16th to endNight
14%425%32%20%2
832
November1st to 15thNight
18%423%34%16%2
820
16th to endNight
15%6%26%34%16%
840
December1st to 15thNight
21%5%27%35%9%
840
16th to endNight
25%428%35%6%
896
Page generated at 2019-06-10 19:29:46. Version ac04

Copyright 2019 A. Danko


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