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 2005-11-06 to 2024-01-13.

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
47%
24315
21%
74364
14%
24267
55%
24267
27%
46849

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
28%
758
24%
2459
10%
757
46%
757
26%
1468
January11th to 20thNight
30%
732
23%
2378
12%
732
45%
732
22%
1527
January21st to endNight
28%
792
27%
2574
13%
792
46%
792
28%
1544
February1st to 10thNight
33%
720
19%
2340
11%
720
45%
720
24%
1455
February11th to 20thNight
22%
700
22%
2179
9%
699
38%
699
23%
1395
February21st to endNight
27%
592
26%
1705
11%
592
41%
592
25%
1104
March1st to 10thNight
35%
720
28%
1980
14%
720
47%
720
32%
1208
March11th to 20thNight
31%
720
20%
1980
10%
720
40%
720
24%
1336
March21st to endNight
35%
792
19%
2178
10%
792
42%
792
25%
1475
April1st to 10thNight
36%
720
23%
1944
10%
720
45%
720
31%
1226
April11th to 20thNight
41%
711
24%
1775
10%
711
49%
711
35%
1133
April21st to endNight
44%
626
25%
1706
13%
626
51%
626
32%
1079
May1st to 10thNight
47%
540
18%
1620
9%
540
54%
540
29%
1013
May11th to 20thNight
50%
531
14%
1593
8%
531
53%
531
23%
1090
May21st to endNight
64%
582
16%
1745
14%
582
65%
582
26%
1149
June1st to 10thNight
64%
540
16%
1620
14%
540
66%
540
27%
1060
June11th to 20thNight
66%
540
15%
1620
13%
540
68%
540
28%
1048
June21st to endNight
67%
540
16%
1620
14%
540
69%
540
27%
1044
July1st to 10thNight
70%
525
12%
1575
12%
525
70%
525
24%
1068
July11th to 20thNight
74%
522
13%
1566
12%
522
75%
522
25%
1048
July21st to endNight
71%
591
15%
1672
14%
558
72%
558
27%
1089
August1st to 10thNight
64%
537
13%
1600
11%
534
64%
534
22%
1144
August11th to 20thNight
64%
534
15%
1598
14%
534
65%
534
21%
1133
August21st to endNight
68%
753
16%
1941
13%
753
69%
753
30%
1328
September1st to 10thNight
68%
720
21%
1877
17%
720
69%
720
32%
1216
September11th to 20thNight
60%
720
20%
1980
18%
720
61%
720
26%
1336
September21st to endNight
52%
720
19%
1980
15%
720
56%
720
25%
1368
October1st to 10thNight
57%
720
24%
2124
23%
720
61%
720
31%
1305
October11th to 20thNight
51%
720
30%
2160
24%
720
61%
720
33%
1266
October21st to endNight
50%
792
31%
2376
22%
792
63%
792
36%
1359
November1st to 10thNight
49%
740
28%
2221
23%
740
58%
740
32%
1303
November11th to 20thNight
44%
760
28%
2403
20%
760
55%
760
31%
1390
November21st to endNight
45%
760
28%
2470
20%
760
56%
760
32%
1416
December1st to 10thNight
33%
760
23%
2470
13%
760
46%
760
22%
1592
December11th to 20thNight
38%
760
26%
2931
17%
758
50%
758
24%
1695
December21st to endNight
35%
825
16%
4404
13%
817
47%
817
15%
2439

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%25%5%35%5%6%8%44%
74945
Night
14%5%25%5%3445%7%45%
74810
TransparencyDay
38%7%12%21%17%4
74667
Night
38%7%11%20%19%5%
74607
SeeingDay
16%7%21%25%20%11%
14184
Night
16%6%24%32%20%2
24333

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
19%5%35%433437%46%
1706
11th to 20thDay
16%7%36%42445%6%44%
1644
21st to endDay
16%5%34334436%49%
1782
February1st to 10thDay
16%5%35%5%3446%7%42%
1620
11th to 20thDay
20%7%24333445%45%
1665
21st to endDay
19%7%35%5%34347%40%
1549
March1st to 10thDay
15%42333345%7%51%
1980
11th to 20thDay
17%5%25%425%46%8%40%
1980
21st to endDay
17%6%26%43445%6%42%
2178
April1st to 10thDay
11%31332445%8%54%
2016
11th to 20thDay
14%5%235%25%45%7%48%
2134
21st to endDay
14%435%435%5%5%7%46%
2268
May1st to 10thDay
11%5%245%45%6%6%8%43%
2340
11th to 20thDay
14%5%26%6%35%6%7%8%39%
2301
21st to endDay
12%5%25%6%45%5%6%9%41%
2531
June1st to 10thDay
9%5%25%6%35%6%6%10%42%
2340
11th to 20thDay
9%6%25%5%36%6%9%11%40%
2340
21st to endDay
7%426%5%37%7%8%12%40%
2340
July1st to 10thDay
9%5%27%7%47%6%7%11%36%
2340
11th to 20thDay
7%436%6%5%7%7%9%12%33%
2340
21st to endDay
8%5%36%7%47%7%7%11%36%
2547
August1st to 10thDay
11%5%26%6%46%7%9%12%33%
2327
11th to 20thDay
10%6%37%7%47%8%8%10%31%
2303
21st to endDay
10%5%35%5%36%6%7%10%40%
2394
September1st to 10thDay
11%5%25%43447%9%47%
2079
11th to 20thDay
12%6%244345%6%9%44%
1980
21st to endDay
19%6%35%5%3445%7%39%
1980
October1st to 10thDay
13%5%24423446%53%
1835
11th to 20thDay
12%5%24433445%55%
1800
21st to endDay
14%5%25%323345%55%
1980
November1st to 10thDay
13%5%13423335%57%
1857
11th to 20thDay
12%5%24323346%55%
1772
21st to endDay
15%5%2443435%6%50%
1710
December1st to 10thDay
19%7%33434447%41%
1710
11th to 20thDay
16%5%13322347%54%
2153
21st to endDay
19%6%25%4245%5%7%41%
3124
January1st to 10thNight
17%6%24433446%49%
2459
11th to 20thNight
17%6%35%5%2444445%
2378
21st to endNight
16%5%25%334445%49%
2574
February1st to 10thNight
17%5%34435%45%6%44%
2340
11th to 20thNight
20%7%24324445%45%
2179
21st to endNight
18%6%35%5%2345%6%44%
1705
March1st to 10thNight
14%5%14334446%52%
1980
11th to 20thNight
17%6%25%5%35%447%42%
1980
21st to endNight
17%6%25%5%3445%7%42%
2178
April1st to 10thNight
14%425%433447%49%
1944
11th to 20thNight
13%5%35%33435%8%49%
1775
21st to endNight
14%5%245%2445%7%48%
1706
May1st to 10thNight
10%425%5%45%5%5%8%46%
1620
11th to 20thNight
12%7%37%5%35%6%7%8%37%
1592
21st to endNight
11%7%25%5%45%5%8%10%39%
1744
June1st to 10thNight
9%425%7%45%6%8%13%36%
1620
11th to 20thNight
11%5%24445%5%7%11%41%
1620
21st to endNight
8%426%5%5%5%7%8%11%39%
1620
July1st to 10thNight
8%5%37%6%46%7%8%10%35%
1620
11th to 20thNight
7%5%26%6%5%7%7%9%11%36%
1620
21st to endNight
8%425%6%46%7%9%13%36%
1771
August1st to 10thNight
12%5%36%6%5%6%6%7%11%33%
1611
11th to 20thNight
11%7%47%5%46%7%8%9%33%
1598
21st to endNight
9%5%36%6%45%6%7%10%39%
1941
September1st to 10thNight
9%5%245%35%6%7%8%46%
1877
11th to 20thNight
13%6%26%6%35%5%6%7%41%
1980
21st to endNight
16%7%35%6%25%5%6%7%38%
1980
October1st to 10thNight
13%6%245%25%346%49%
2124
11th to 20thNight
14%424423345%54%
2160
21st to endNight
13%5%24423335%56%
2376
November1st to 10thNight
15%5%2432333455%
2221
11th to 20thNight
14%4245%24345%53%
2403
21st to endNight
14%5%1332445%7%51%
2470
December1st to 10thNight
20%7%25%433445%43%
2470
11th to 20thNight
17%5%24423446%49%
3042
21st to endNight
21%42442345%7%42%
4532

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
41%49%23%18%6%
1707
11th to 20thDay
42%5%7%21%22%4
1644
21st to endDay
37%47%23%21%7%
1782
February1st to 10thDay
41%5%11%20%18%5%
1620
11th to 20thDay
41%49%21%19%5%
1674
21st to endDay
45%5%10%15%17%7%
1549
March1st to 10thDay
34%5%8%23%24%6%
1980
11th to 20thDay
41%7%11%19%17%6%
1980
21st to endDay
43%6%10%20%17%3
2178
April1st to 10thDay
29%5%12%24%24%7%
2016
11th to 20thDay
35%6%10%21%20%9%
2134
21st to endDay
37%7%12%24%17%4
2268
May1st to 10thDay
36%8%17%19%14%4
2340
11th to 20thDay
41%11%15%20%11%3
2305
21st to endDay
38%10%14%25%12%1
2531
June1st to 10thDay
36%9%15%25%14%1
2340
11th to 20thDay
34%11%18%20%14%2
2340
21st to endDay
34%11%18%21%14%1
2340
July1st to 10thDay
40%13%15%16%13%3
2275
11th to 20thDay
38%13%22%17%9%1
2271
21st to endDay
39%11%19%21%9%1
2405
August1st to 10thDay
40%12%17%22%8%
2314
11th to 20thDay
43%14%15%18%10%1
2303
21st to endDay
37%10%18%21%10%3
2394
September1st to 10thDay
34%9%14%21%17%4
2079
11th to 20thDay
35%9%13%19%21%3
1980
21st to endDay
46%6%8%19%18%3
1980
October1st to 10thDay
33%5%10%23%25%5%
1835
11th to 20thDay
32%48%26%22%7%
1800
21st to endDay
33%47%23%24%9%
1980
November1st to 10thDay
32%47%21%28%8%
1857
11th to 20thDay
31%5%8%22%27%7%
1772
21st to endDay
35%49%22%25%5%
1710
December1st to 10thDay
44%6%8%20%18%4
1710
11th to 20thDay
32%39%23%25%9%
2150
21st to endDay
41%411%23%19%2
3124
January1st to 10thNight
38%410%19%23%7%
2459
11th to 20thNight
43%5%9%17%21%5%
2378
21st to endNight
38%46%23%24%6%
2574
February1st to 10thNight
41%411%20%19%5%
2340
11th to 20thNight
43%48%18%20%7%
2181
21st to endNight
42%411%18%19%6%
1705
March1st to 10thNight
34%5%8%20%24%9%
1980
11th to 20thNight
43%6%8%19%18%6%
1980
21st to endNight
43%6%9%20%18%4
2178
April1st to 10thNight
36%5%10%20%24%5%
1944
11th to 20thNight
34%5%10%21%22%9%
1775
21st to endNight
37%5%11%23%19%5%
1706
May1st to 10thNight
36%7%15%23%16%2
1620
11th to 20thNight
42%10%13%19%14%2
1593
21st to endNight
38%10%15%24%12%1
1745
June1st to 10thNight
37%10%15%23%13%2
1620
11th to 20thNight
36%10%17%21%14%2
1620
21st to endNight
37%10%18%19%13%4
1620
July1st to 10thNight
38%13%16%18%12%3
1575
11th to 20thNight
36%13%20%19%8%3
1566
21st to endNight
35%12%22%22%9%1
1672
August1st to 10thNight
43%12%18%18%9%1
1600
11th to 20thNight
42%14%16%18%9%2
1598
21st to endNight
38%10%19%22%9%3
1941
September1st to 10thNight
34%9%15%21%16%6%
1877
11th to 20thNight
41%8%12%18%20%2
1980
21st to endNight
45%7%12%16%17%3
1980
October1st to 10thNight
37%5%9%22%23%4
2124
11th to 20thNight
33%5%8%25%23%6%
2160
21st to endNight
33%37%21%26%11%
2376
November1st to 10thNight
35%47%19%25%10%
2221
11th to 20thNight
34%47%18%26%11%
2403
21st to endNight
34%47%23%26%6%
2470
December1st to 10thNight
44%5%9%19%19%5%
2470
11th to 20thNight
37%48%18%23%9%
3044
21st to endNight
40%5%11%21%21%2
4532

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
21%16%35%21%6%
270
11th to 20thDay
21%15%36%21%7%
248
21st to endDay
19%17%38%20%5%
264
February1st to 10thDay
20%16%33%21%10%
240
11th to 20thDay
33%13%38%12%5%
240
21st to endDay
27%15%33%20%4
267
March1st to 10thDay
19%12%34%24%10%
420
11th to 20thDay
21%10%38%24%5%1
420
21st to endDay
20%13%33%24%10%
462
April1st to 10thDay
18%13%29%25%12%3
420
11th to 20thDay
14%12%27%24%18%5%
412
21st to endDay
16%10%27%23%19%4
420
May1st to 10thDay
14%11%27%27%16%5%
423
11th to 20thDay
15%5%18%28%21%14%
447
21st to endDay
19%213%22%28%17%
485
June1st to 10thDay
11%214%30%28%14%
450
11th to 20thDay
10%416%22%25%22%
450
21st to endDay
8%211%34%29%16%
450
July1st to 10thDay
11%27%23%31%26%
445
11th to 20thDay
5%16%24%34%30%
444
21st to endDay
7%29%24%33%25%
488
August1st to 10thDay
14%112%22%29%22%
446
11th to 20thDay
11%28%26%29%25%
439
21st to endDay
12%19%24%33%22%
495
September1st to 10thDay
12%29%20%33%24%
450
11th to 20thDay
16%211%21%30%20%
450
21st to endDay
23%417%26%23%7%
450
October1st to 10thDay
18%5%14%28%23%12%
450
11th to 20thDay
12%6%22%29%24%8%
450
21st to endDay
17%6%21%31%19%6%
495
November1st to 10thDay
19%5%25%29%16%6%
455
11th to 20thDay
15%8%36%23%14%4
332
21st to endDay
13%9%33%26%14%5%
270
December1st to 10thDay
23%9%30%28%8%1
270
11th to 20thDay
17%11%29%30%11%2
270
21st to endDay
24%13%26%26%8%2
297
January1st to 10thNight
19%10%36%28%7%
760
11th to 20thNight
21%9%35%31%5%
732
21st to endNight
18%8%41%29%3
792
February1st to 10thNight
19%9%34%33%4
720
11th to 20thNight
23%12%38%25%1
703
21st to endNight
19%11%38%29%3
592
March1st to 10thNight
17%10%35%33%5%
720
11th to 20thNight
20%9%35%27%8%
720
21st to endNight
18%8%33%34%6%
792
April1st to 10thNight
17%11%32%30%10%
720
11th to 20thNight
15%10%30%31%13%
711
21st to endNight
16%6%29%36%13%
626
May1st to 10thNight
9%7%29%37%17%1
540
11th to 20thNight
14%5%22%32%25%2
531
21st to endNight
14%211%36%33%4
584
June1st to 10thNight
10%214%38%33%4
540
11th to 20thNight
11%312%31%39%6%
540
21st to endNight
8%111%34%43%2
540
July1st to 10thNight
9%28%32%43%7%
525
11th to 20thNight
7%25%30%48%8%
522
21st to endNight
9%17%33%42%8%
591
August1st to 10thNight
14%28%28%40%8%
537
11th to 20thNight
12%27%31%40%7%
534
21st to endNight
11%18%28%44%7%
753
September1st to 10thNight
10%29%31%41%7%
720
11th to 20thNight
15%311%28%37%6%
720
21st to endNight
19%418%31%27%2
720
October1st to 10thNight
15%6%16%29%29%5%
720
11th to 20thNight
17%5%23%35%18%2
720
21st to endNight
15%6%24%36%17%2
792
November1st to 10thNight
16%6%22%37%16%2
740
11th to 20thNight
16%6%28%37%13%
760
21st to endNight
16%6%28%37%13%1
760
December1st to 10thNight
22%7%30%33%7%
760
11th to 20thNight
19%5%31%36%9%
760
21st to endNight
25%6%27%35%8%
836
Page generated at 2024-01-10 19:35:24. Version ac07

Copyright 2024 Attilla Danko


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