Hebron Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hebron Observatory clear sky chart from 2005-11-06 to 2024-01-11.

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
24%
23041
13%
74753
7%
22988
31%
22988
14%
54457

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
6%
758
10%
2649
2%
757
15%
757
5%
2159
January11th to 20thNight
10%
724
7%
2388
3%
724
16%
724
7%
1928
January21st to endNight
9%
792
10%
2574
3%
792
18%
792
7%
2118
February1st to 10thNight
7%
720
9%
2340
2%
720
17%
720
7%
1881
February11th to 20thNight
6%
703
9%
2275
2%
700
16%
700
7%
1792
February21st to endNight
9%
592
11%
1817
2%
592
19%
592
8%
1425
March1st to 10thNight
10%
720
14%
1996
4%
720
21%
720
11%
1522
March11th to 20thNight
16%
720
15%
1980
6%
720
24%
720
12%
1502
March21st to endNight
15%
792
16%
2167
5%
792
24%
792
15%
1616
April1st to 10thNight
16%
720
12%
1800
3%
720
23%
720
16%
1384
April11th to 20thNight
21%
711
14%
1775
4%
711
26%
711
21%
1285
April21st to endNight
23%
623
16%
1703
5%
623
30%
623
19%
1202
May1st to 10thNight
30%
540
14%
1620
8%
540
35%
540
18%
1151
May11th to 20thNight
30%
359
18%
1421
12%
359
41%
359
15%
948
May21st to endNight
40%
388
16%
1551
15%
388
47%
388
20%
935
June1st to 10thNight
38%
360
16%
1440
15%
360
49%
360
20%
881
June11th to 20thNight
42%
360
14%
1440
13%
360
50%
360
19%
871
June21st to endNight
43%
360
16%
1440
17%
360
52%
360
22%
876
July1st to 10thNight
50%
350
15%
1400
19%
350
55%
350
24%
831
July11th to 20thNight
51%
348
19%
1392
24%
348
57%
348
29%
765
July21st to endNight
50%
563
16%
1646
12%
532
55%
532
28%
1035
August1st to 10thNight
53%
537
15%
1600
11%
534
56%
534
31%
1000
August11th to 20thNight
49%
534
17%
1598
11%
534
52%
534
25%
1051
August21st to endNight
50%
764
19%
1952
10%
764
53%
764
31%
1290
September1st to 10thNight
42%
720
20%
1800
9%
720
46%
720
30%
1203
September11th to 20thNight
48%
720
25%
1818
14%
720
54%
720
34%
1181
September21st to endNight
39%
720
19%
2069
14%
720
43%
720
23%
1416
October1st to 10thNight
33%
720
15%
2160
11%
720
40%
720
21%
1457
October11th to 20thNight
22%
720
13%
2160
7%
720
31%
720
17%
1520
October21st to endNight
15%
792
15%
2376
6%
792
27%
792
13%
1811
November1st to 10thNight
25%
740
19%
2353
12%
740
35%
740
19%
1588
November11th to 20thNight
16%
760
14%
2655
7%
760
25%
760
11%
1941
November21st to endNight
14%
760
11%
2660
6%
760
23%
760
9%
2040
December1st to 10thNight
9%
760
6%
2660
3%
760
13%
760
5%
2220
December11th to 20thNight
11%
760
7%
3233
2%
759
17%
759
5%
2604
December21st to endNight
7%
831
5%
4845
2%
817
16%
817
3%
4028

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
16%12%5%8%6%35%5%5%6%28%
74662
Night
16%13%6%9%6%3445%6%28%
75028
TransparencyDay
56%310%19%10%1
74377
Night
57%310%19%10%1
74847
SeeingDay
27%18%28%17%8%3
13524
Night
26%17%28%20%8%1
23049

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 10thDay
13%16%10%14%8%34345%18%
1517
11th to 20thDay
14%18%8%14%9%43345%17%
1580
21st to endDay
11%18%9%15%11%44445%15%
1782
February1st to 10thDay
15%17%9%12%10%45%44417%
1620
11th to 20thDay
12%15%9%14%8%45%445%20%
1573
21st to endDay
18%15%5%11%9%3434425%
1438
March1st to 10thDay
15%14%7%10%7%44446%27%
1959
11th to 20thDay
14%15%8%10%6%34445%27%
1980
21st to endDay
19%13%6%8%6%2345%5%28%
2188
April1st to 10thDay
15%16%6%8%5%345%46%30%
2160
11th to 20thDay
18%13%47%435%5%5%5%31%
2134
21st to endDay
21%12%36%5%345%4432%
2272
May1st to 10thDay
20%11%47%7%35%45%6%27%
2340
11th to 20thDay
21%10%36%6%45%5%5%6%30%
2473
21st to endDay
15%6%36%6%36%6%5%8%37%
2725
June1st to 10thDay
17%7%36%6%45%5%6%7%33%
2520
11th to 20thDay
17%7%36%6%46%5%6%8%32%
2520
21st to endDay
15%7%36%6%46%6%6%7%35%
2520
July1st to 10thDay
11%6%37%6%47%6%6%8%37%
2520
11th to 20thDay
12%7%36%6%37%6%8%10%33%
2520
21st to endDay
12%7%37%6%46%7%7%7%34%
2572
August1st to 10thDay
11%7%37%7%45%7%7%10%33%
2327
11th to 20thDay
14%7%37%8%47%6%6%8%29%
2303
21st to endDay
15%7%36%7%46%6%7%8%31%
2385
September1st to 10thDay
19%8%25%5%245%5%7%37%
2160
11th to 20thDay
15%7%36%5%3445%6%41%
2138
21st to endDay
19%8%46%6%35%5%5%6%33%
1890
October1st to 10thDay
19%10%36%6%25%5%5%7%32%
1800
11th to 20thDay
22%11%38%5%3445%6%29%
1800
21st to endDay
24%16%46%6%34445%24%
1980
November1st to 10thDay
14%13%47%5%44446%35%
1724
11th to 20thDay
16%18%7%8%5%345%6%6%23%
1524
21st to endDay
18%21%6%8%6%34446%20%
1520
December1st to 10thDay
17%21%10%14%6%33445%13%
1520
11th to 20thDay
16%19%7%14%6%335%45%17%
1906
21st to endDay
20%25%9%9%6%3333414%
2772
January1st to 10thNight
15%15%10%14%8%46%44416%
2649
11th to 20thNight
16%16%9%12%8%35%445%17%
2388
21st to endNight
12%16%10%14%10%5%6%44415%
2574
February1st to 10thNight
15%16%9%10%11%45%345%18%
2340
11th to 20thNight
14%14%8%12%9%5%6%5%45%19%
2273
21st to endNight
16%14%7%13%9%35%34422%
1817
March1st to 10thNight
13%13%7%13%7%45%446%25%
1986
11th to 20thNight
16%14%6%11%7%24336%28%
1979
21st to endNight
14%16%6%8%6%34446%30%
2167
April1st to 10thNight
18%13%6%8%6%35%5%46%28%
1800
11th to 20thNight
18%13%46%5%2345%6%35%
1775
21st to endNight
17%12%36%5%35%45%7%33%
1703
May1st to 10thNight
18%11%47%5%35%436%33%
1620
11th to 20thNight
15%10%37%6%45%45%6%35%
1420
21st to endNight
13%7%26%6%345%5%8%42%
1550
June1st to 10thNight
14%8%45%5%345%5%10%36%
1440
11th to 20thNight
12%7%37%5%346%6%10%37%
1440
21st to endNight
13%6%25%5%345%6%6%44%
1440
July1st to 10thNight
10%6%26%6%35%5%5%8%43%
1440
11th to 20thNight
10%5%35%5%3445%9%48%
1440
21st to endNight
12%5%25%5%36%5%5%9%40%
1743
August1st to 10thNight
9%7%26%5%45%5%7%8%43%
1611
11th to 20thNight
14%7%45%6%3447%7%38%
1598
21st to endNight
12%6%26%5%35%5%7%8%40%
1952
September1st to 10thNight
15%8%35%6%24347%44%
1800
11th to 20thNight
14%7%25%42445%7%46%
1818
21st to endNight
18%9%36%5%3445%6%37%
2069
October1st to 10thNight
17%9%36%5%335%47%38%
2160
11th to 20thNight
19%13%36%5%4345%7%31%
2160
21st to endNight
25%16%36%5%24346%26%
2376
November1st to 10thNight
12%13%47%6%3445%5%38%
2353
11th to 20thNight
16%18%5%8%5%35%45%6%26%
2655
21st to endNight
16%18%7%10%7%35%446%21%
2660
December1st to 10thNight
18%19%10%12%7%44335%14%
2660
11th to 20thNight
18%17%8%15%8%3434417%
3288
21st to endNight
20%19%11%10%7%44445%12%
4884

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
70%37%14%6%1
1518
11th to 20thDay
72%29%10%7%1
1580
21st to endDay
72%27%11%7%1
1782
February1st to 10thDay
73%210%10%5%1
1620
11th to 20thDay
67%36%16%8%
1582
21st to endDay
64%26%18%7%2
1438
March1st to 10thDay
59%29%19%9%1
1962
11th to 20thDay
60%28%18%9%3
1980
21st to endDay
59%36%18%12%3
2188
April1st to 10thDay
56%310%19%12%1
2160
11th to 20thDay
55%49%18%14%1
2134
21st to endDay
56%27%20%13%2
2272
May1st to 10thDay
59%29%18%9%2
2340
11th to 20thDay
56%39%18%12%1
2477
21st to endDay
45%416%22%12%1
2725
June1st to 10thDay
49%412%21%13%1
2520
11th to 20thDay
50%413%21%12%1
2520
21st to endDay
47%5%11%26%11%
2520
July1st to 10thDay
46%5%9%25%13%1
2450
11th to 20thDay
44%414%24%13%
2445
21st to endDay
46%5%12%25%12%1
2428
August1st to 10thDay
46%5%12%27%10%1
2314
11th to 20thDay
50%5%14%21%9%1
2303
21st to endDay
49%5%10%22%13%2
2385
September1st to 10thDay
48%39%24%14%2
2160
11th to 20thDay
44%310%25%16%2
2138
21st to endDay
52%39%22%14%1
1890
October1st to 10thDay
52%310%20%13%2
1800
11th to 20thDay
56%311%20%10%1
1800
21st to endDay
63%38%15%8%2
1980
November1st to 10thDay
50%310%20%13%3
1724
11th to 20thDay
62%39%17%7%2
1524
21st to endDay
67%29%16%5%1
1520
December1st to 10thDay
74%28%9%6%
1520
11th to 20thDay
69%310%13%5%
1906
21st to endDay
76%29%11%2
2772
January1st to 10thNight
71%36%13%6%1
2649
11th to 20thNight
70%311%11%41
2388
21st to endNight
71%36%11%8%1
2574
February1st to 10thNight
69%29%12%7%
2340
11th to 20thNight
67%38%15%7%1
2275
21st to endNight
66%29%13%9%1
1817
March1st to 10thNight
60%39%20%6%2
1996
11th to 20thNight
59%38%19%9%1
1980
21st to endNight
57%38%16%14%3
2167
April1st to 10thNight
58%48%17%12%1
1800
11th to 20thNight
52%310%20%13%2
1775
21st to endNight
52%39%21%13%2
1703
May1st to 10thNight
54%29%21%11%2
1620
11th to 20thNight
51%49%22%14%1
1421
21st to endNight
43%413%24%13%3
1551
June1st to 10thNight
45%412%25%14%1
1440
11th to 20thNight
43%415%25%12%2
1440
21st to endNight
41%6%12%27%13%1
1440
July1st to 10thNight
40%5%12%26%17%1
1400
11th to 20thNight
35%416%26%18%1
1392
21st to endNight
40%415%23%16%1
1646
August1st to 10thNight
38%5%15%31%10%1
1600
11th to 20thNight
43%5%14%28%10%
1598
21st to endNight
40%413%27%13%2
1952
September1st to 10thNight
43%212%27%13%3
1800
11th to 20thNight
39%312%27%18%2
1818
21st to endNight
48%312%22%13%1
2069
October1st to 10thNight
48%412%21%15%1
2160
11th to 20thNight
52%413%19%10%1
2160
21st to endNight
62%210%17%8%1
2376
November1st to 10thNight
48%411%20%14%3
2353
11th to 20thNight
60%39%17%9%3
2655
21st to endNight
64%310%17%5%1
2660
December1st to 10thNight
74%38%11%4
2660
11th to 20thNight
71%27%15%4
3288
21st to endNight
76%28%11%3
4884

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
38%23%26%9%31
180
11th to 20thDay
35%31%28%5%2
222
21st to endDay
34%30%28%6%2
264
February1st to 10thDay
42%29%26%3
240
11th to 20thDay
40%30%28%1
240
21st to endDay
44%27%23%6%
304
March1st to 10thDay
37%24%28%9%2
420
11th to 20thDay
33%26%27%11%21
420
21st to endDay
37%21%27%12%31
462
April1st to 10thDay
33%24%27%11%31
420
11th to 20thDay
31%22%25%14%6%2
412
21st to endDay
32%20%31%13%4
420
May1st to 10thDay
31%22%26%12%8%2
423
11th to 20thDay
30%17%29%16%6%2
447
21st to endDay
20%14%29%21%12%4
485
June1st to 10thDay
22%15%31%22%8%2
450
11th to 20thDay
22%13%27%25%10%2
450
21st to endDay
20%12%35%23%8%2
450
July1st to 10thDay
14%10%29%26%15%6%
445
11th to 20thDay
13%11%27%30%14%5%
444
21st to endDay
15%11%34%27%9%4
488
August1st to 10thDay
13%10%24%29%17%7%
446
11th to 20thDay
18%7%29%26%13%7%
439
21st to endDay
17%12%28%24%13%7%
495
September1st to 10thDay
23%11%23%23%13%7%
450
11th to 20thDay
15%10%26%23%18%8%
450
21st to endDay
24%16%25%20%12%4
450
October1st to 10thDay
25%15%24%18%14%4
450
11th to 20thDay
32%19%30%14%6%
450
21st to endDay
39%17%26%15%2
495
November1st to 10thDay
29%18%28%16%7%2
391
11th to 20thDay
41%21%27%10%11
184
21st to endDay
38%25%30%6%11
180
December1st to 10thDay
44%24%22%5%31
180
11th to 20thDay
42%25%26%6%2
180
21st to endDay
39%28%29%31
198
January1st to 10thNight
31%27%30%10%2
760
11th to 20thNight
31%25%30%12%2
724
21st to endNight
29%28%29%12%1
792
February1st to 10thNight
32%26%32%11%
720
11th to 20thNight
31%29%31%8%1
703
21st to endNight
35%26%27%10%2
592
March1st to 10thNight
29%27%31%11%2
720
11th to 20thNight
33%22%26%15%4
720
21st to endNight
26%23%33%14%5%1
792
April1st to 10thNight
28%20%32%17%3
720
11th to 20thNight
30%17%29%17%6%1
711
21st to endNight
26%14%34%23%4
623
May1st to 10thNight
27%12%24%27%9%
540
11th to 20thNight
18%14%32%28%8%
359
21st to endNight
16%9%29%31%15%1
389
June1st to 10thNight
18%8%29%31%12%1
360
11th to 20thNight
16%11%26%36%11%
360
21st to endNight
12%8%33%34%12%
360
July1st to 10thNight
13%424%38%18%3
350
11th to 20thNight
11%426%37%21%1
348
21st to endNight
14%5%22%39%18%1
563
August1st to 10thNight
12%421%37%23%2
537
11th to 20thNight
18%5%19%32%25%2
534
21st to endNight
15%8%20%32%23%3
764
September1st to 10thNight
20%8%24%30%16%3
720
11th to 20thNight
18%7%22%27%23%4
720
21st to endNight
21%12%23%24%16%3
720
October1st to 10thNight
23%12%27%20%16%2
720
11th to 20thNight
28%15%31%19%5%1
720
21st to endNight
37%15%29%16%3
792
November1st to 10thNight
21%19%32%21%6%
740
11th to 20thNight
31%20%29%14%5%1
760
21st to endNight
31%22%30%14%31
760
December1st to 10thNight
34%26%27%9%3
760
11th to 20thNight
32%26%28%13%2
760
21st to endNight
33%24%31%10%1
836
Page generated at 2024-01-08 11:14:19. Version ac07

Copyright 2024 Attilla Danko


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