Heilwood
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Heilwood clear sky chart from 2005-11-06 to 2024-01-14.

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
28%
23274
14%
74848
9%
23221
35%
23221
16%
54068

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
9%
757
11%
2559
4%
757
18%
757
6%
2074
January11th to 20thNight
9%
736
6%
2391
2%
736
13%
736
6%
2001
January21st to endNight
10%
792
10%
2574
3%
792
17%
792
8%
2094
February1st to 10thNight
10%
720
10%
2340
4%
720
18%
720
8%
1865
February11th to 20thNight
7%
703
9%
2275
2%
700
16%
700
7%
1820
February21st to endNight
10%
592
14%
1788
3%
592
22%
592
9%
1408
March1st to 10thNight
15%
720
15%
1980
7%
720
25%
720
14%
1488
March11th to 20thNight
19%
720
16%
1980
8%
720
27%
720
14%
1459
March21st to endNight
17%
792
16%
2178
6%
792
26%
792
17%
1592
April1st to 10thNight
19%
720
12%
1833
4%
720
24%
720
17%
1380
April11th to 20thNight
25%
711
15%
1775
5%
711
31%
711
23%
1278
April21st to endNight
26%
600
17%
1680
7%
600
32%
600
19%
1209
May1st to 10thNight
32%
540
14%
1620
7%
540
38%
540
18%
1154
May11th to 20thNight
33%
474
15%
1536
9%
474
39%
474
17%
1073
May21st to endNight
47%
388
18%
1551
17%
388
55%
388
23%
901
June1st to 10thNight
45%
360
17%
1440
15%
360
55%
360
22%
869
June11th to 20thNight
45%
360
15%
1440
16%
360
51%
360
20%
900
June21st to endNight
47%
360
17%
1440
17%
360
55%
360
23%
839
July1st to 10thNight
55%
350
14%
1400
16%
350
59%
350
22%
859
July11th to 20thNight
58%
469
18%
1513
17%
469
61%
469
31%
880
July21st to endNight
54%
591
16%
1672
13%
558
57%
558
27%
1074
August1st to 10thNight
58%
537
17%
1600
13%
534
61%
534
29%
1018
August11th to 20thNight
58%
534
19%
1598
14%
534
61%
534
29%
1008
August21st to endNight
57%
746
19%
1934
11%
746
59%
746
33%
1262
September1st to 10thNight
50%
720
22%
1800
11%
720
55%
720
32%
1206
September11th to 20thNight
57%
720
27%
1885
18%
720
61%
720
38%
1142
September21st to endNight
42%
720
20%
2029
15%
720
46%
720
26%
1347
October1st to 10thNight
40%
720
16%
2160
14%
720
45%
720
24%
1424
October11th to 20thNight
26%
720
16%
2160
9%
720
37%
720
20%
1477
October21st to endNight
22%
792
18%
2376
10%
792
33%
792
15%
1734
November1st to 10thNight
32%
740
22%
2255
13%
740
42%
740
23%
1473
November11th to 20thNight
20%
760
15%
2660
9%
760
29%
760
12%
1936
November21st to endNight
16%
760
13%
2660
6%
760
26%
760
11%
1990
December1st to 10thNight
13%
760
7%
2660
4%
760
17%
760
6%
2204
December11th to 20thNight
11%
760
8%
3246
3%
759
18%
759
5%
2588
December21st to endNight
12%
830
6%
4860
3%
817
19%
817
4%
4042

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%11%5%8%6%35%5%5%7%29%
74652
Night
16%12%5%8%6%3445%6%31%
75107
TransparencyDay
54%6%11%18%9%1
74365
Night
54%5%11%19%10%1
74914
SeeingDay
26%16%26%19%9%3
13604
Night
25%16%26%23%9%1
23284

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
16%15%10%16%8%33425%18%
1602
11th to 20thDay
17%19%9%15%8%4433415%
1647
21st to endDay
17%18%9%14%10%3433416%
1782
February1st to 10thDay
18%18%7%12%9%45%33417%
1620
11th to 20thDay
16%14%10%13%7%35%446%18%
1573
21st to endDay
18%17%6%12%6%43335%22%
1463
March1st to 10thDay
14%13%9%10%5%34445%30%
1980
11th to 20thDay
18%16%5%9%6%3445%6%26%
1980
21st to endDay
19%13%5%8%6%3446%7%26%
2178
April1st to 10thDay
15%13%5%8%6%3445%6%30%
2126
11th to 20thDay
16%13%46%6%35%346%33%
2134
21st to endDay
21%11%46%5%35%5%47%30%
2294
May1st to 10thDay
20%11%37%6%35%5%6%7%27%
2340
11th to 20thDay
24%8%36%5%45%45%8%28%
2354
21st to endDay
14%6%36%5%46%5%7%9%36%
2725
June1st to 10thDay
17%7%35%7%45%5%7%8%32%
2520
11th to 20thDay
17%6%36%6%35%5%6%9%32%
2520
21st to endDay
15%6%36%6%45%5%7%10%33%
2520
July1st to 10thDay
14%6%37%6%36%6%5%8%36%
2520
11th to 20thDay
13%7%35%5%45%6%7%9%36%
2393
21st to endDay
14%7%37%6%46%6%6%8%33%
2547
August1st to 10thDay
12%6%26%7%5%7%7%8%10%30%
2327
11th to 20thDay
14%8%36%6%46%6%6%8%32%
2303
21st to endDay
15%6%35%6%36%6%7%10%33%
2404
September1st to 10thDay
18%6%345%35%5%5%7%39%
2160
11th to 20thDay
15%5%35%5%345%5%8%43%
2070
21st to endDay
19%8%45%5%35%45%7%35%
1930
October1st to 10thDay
18%8%27%6%35%5%5%7%35%
1800
11th to 20thDay
20%12%36%6%3445%5%32%
1800
21st to endDay
23%14%35%5%33445%29%
1980
November1st to 10thDay
13%12%45%6%25%446%39%
1818
11th to 20thDay
16%15%5%7%5%35%5%6%6%27%
1520
21st to endDay
19%16%8%8%6%34445%23%
1520
December1st to 10thDay
19%18%12%12%6%2433416%
1520
11th to 20thDay
17%20%8%11%6%23346%19%
1910
21st to endDay
23%23%9%10%6%2323415%
2772
January1st to 10thNight
15%18%8%11%8%45%44419%
2559
11th to 20thNight
18%16%8%14%9%4444416%
2391
21st to endNight
14%18%9%12%10%3434419%
2574
February1st to 10thNight
17%14%7%12%9%4444422%
2340
11th to 20thNight
16%15%6%12%10%45%446%20%
2273
21st to endNight
18%15%7%12%8%3334425%
1788
March1st to 10thNight
16%11%6%9%5%345%5%6%29%
1980
11th to 20thNight
17%12%6%7%5%25%446%33%
1980
21st to endNight
17%14%6%8%5%23436%32%
2178
April1st to 10thNight
16%14%5%7%5%3445%6%31%
1833
11th to 20thNight
16%11%35%5%26%46%7%36%
1775
21st to endNight
16%11%37%6%36%347%34%
1680
May1st to 10thNight
19%9%36%5%45%45%6%33%
1620
11th to 20thNight
18%8%46%5%445%5%7%35%
1535
21st to endNight
10%7%25%5%45%46%10%42%
1550
June1st to 10thNight
13%5%25%5%35%5%6%8%42%
1440
11th to 20thNight
13%7%25%6%35%5%6%10%37%
1440
21st to endNight
14%5%25%4345%5%11%42%
1440
July1st to 10thNight
12%6%25%5%35%6%5%6%44%
1440
11th to 20thNight
10%5%245%345%6%10%47%
1563
21st to endNight
12%6%26%5%45%5%7%8%39%
1771
August1st to 10thNight
9%6%35%5%35%6%7%9%42%
1611
11th to 20thNight
11%7%35%5%345%6%8%43%
1598
21st to endNight
11%6%25%435%6%7%9%42%
1934
September1st to 10thNight
15%5%26%4345%5%6%45%
1800
11th to 20thNight
11%42442446%8%51%
1885
21st to endNight
16%7%36%5%345%5%7%40%
2029
October1st to 10thNight
16%8%25%5%3445%7%42%
2160
11th to 20thNight
19%10%25%435%446%38%
2160
21st to endNight
25%13%35%433345%31%
2376
November1st to 10thNight
11%12%45%5%34346%42%
2255
11th to 20thNight
17%14%5%7%6%35%45%5%29%
2660
21st to endNight
18%15%7%8%5%35%35%5%27%
2660
December1st to 10thNight
20%19%9%12%5%3444416%
2660
11th to 20thNight
18%18%8%13%7%3433420%
3285
21st to endNight
19%21%9%10%7%4444413%
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
71%5%8%11%41
1603
11th to 20thDay
74%39%10%3
1647
21st to endDay
74%38%9%5%1
1782
February1st to 10thDay
73%48%10%5%
1620
11th to 20thDay
68%6%8%13%5%
1582
21st to endDay
66%49%13%6%2
1463
March1st to 10thDay
56%5%11%20%7%
1980
11th to 20thDay
60%5%9%16%8%2
1980
21st to endDay
59%49%18%10%2
2178
April1st to 10thDay
54%5%11%17%10%2
2126
11th to 20thDay
52%5%10%16%15%2
2134
21st to endDay
54%49%20%11%1
2294
May1st to 10thDay
54%6%11%18%10%2
2340
11th to 20thDay
54%7%11%15%11%2
2358
21st to endDay
43%8%18%21%8%2
2725
June1st to 10thDay
48%7%12%23%10%
2520
11th to 20thDay
47%7%15%19%11%1
2520
21st to endDay
45%7%12%25%11%
2520
July1st to 10thDay
46%8%10%21%12%3
2450
11th to 20thDay
42%7%14%24%13%1
2321
21st to endDay
46%7%11%22%13%1
2405
August1st to 10thDay
45%9%15%24%7%
2314
11th to 20thDay
48%6%13%23%10%1
2303
21st to endDay
44%6%14%22%12%3
2404
September1st to 10thDay
44%7%9%22%15%3
2160
11th to 20thDay
39%6%11%27%15%1
2070
21st to endDay
49%413%20%13%1
1930
October1st to 10thDay
47%7%13%20%12%1
1800
11th to 20thDay
52%5%10%23%9%
1800
21st to endDay
57%410%17%11%1
1980
November1st to 10thDay
46%5%11%19%16%3
1818
11th to 20thDay
57%411%16%9%2
1520
21st to endDay
64%311%15%6%1
1520
December1st to 10thDay
73%49%10%4
1520
11th to 20thDay
68%38%17%3
1906
21st to endDay
76%37%11%2
2772
January1st to 10thNight
69%47%14%5%1
2559
11th to 20thNight
73%49%11%21
2391
21st to endNight
70%39%12%6%1
2574
February1st to 10thNight
66%48%15%6%
2340
11th to 20thNight
67%48%14%7%
2275
21st to endNight
63%47%15%9%1
1788
March1st to 10thNight
54%6%8%20%11%1
1980
11th to 20thNight
54%5%11%18%10%1
1980
21st to endNight
54%49%17%14%2
2178
April1st to 10thNight
55%5%10%17%12%1
1833
11th to 20thNight
46%7%12%18%14%3
1775
21st to endNight
50%5%9%21%12%3
1680
May1st to 10thNight
51%5%10%18%12%3
1620
11th to 20thNight
48%9%10%18%14%2
1536
21st to endNight
37%7%16%26%13%2
1551
June1st to 10thNight
39%7%12%27%13%1
1440
11th to 20thNight
41%9%14%23%12%2
1440
21st to endNight
38%7%15%26%15%
1440
July1st to 10thNight
40%8%13%22%14%4
1400
11th to 20thNight
32%7%14%26%19%2
1513
21st to endNight
39%8%15%22%14%2
1672
August1st to 10thNight
36%8%16%27%13%
1600
11th to 20thNight
38%7%15%25%13%2
1598
21st to endNight
36%8%15%25%13%3
1934
September1st to 10thNight
39%6%11%24%17%3
1800
11th to 20thNight
31%6%13%29%20%1
1885
21st to endNight
44%413%22%16%1
2029
October1st to 10thNight
42%7%13%23%13%2
2160
11th to 20thNight
47%5%12%23%12%1
2160
21st to endNight
55%49%20%10%2
2376
November1st to 10thNight
44%5%11%20%16%4
2255
11th to 20thNight
57%48%18%10%2
2660
21st to endNight
60%410%18%6%1
2660
December1st to 10thNight
72%49%10%4
2660
11th to 20thNight
69%38%16%4
3288
21st to endNight
74%49%10%2
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
37%25%24%9%5%
220
11th to 20thDay
41%32%20%42
249
21st to endDay
33%30%28%8%1
264
February1st to 10thDay
33%31%32%41
240
11th to 20thDay
44%25%28%2
240
21st to endDay
37%29%28%6%
278
March1st to 10thDay
35%24%28%12%2
420
11th to 20thDay
34%23%27%11%41
420
21st to endDay
34%23%24%15%31
462
April1st to 10thDay
30%25%27%13%4
420
11th to 20thDay
25%23%29%12%8%4
412
21st to endDay
33%18%30%14%41
420
May1st to 10thDay
34%15%27%16%6%2
423
11th to 20thDay
27%15%31%19%7%2
447
21st to endDay
18%11%28%25%14%5%
485
June1st to 10thDay
21%14%27%25%11%2
450
11th to 20thDay
24%13%26%20%14%3
450
21st to endDay
19%11%30%26%12%2
450
July1st to 10thDay
16%9%24%24%19%9%
445
11th to 20thDay
13%9%27%33%12%6%
444
21st to endDay
17%7%27%29%14%6%
488
August1st to 10thDay
15%6%24%27%20%7%
446
11th to 20thDay
19%7%22%27%16%9%
439
21st to endDay
15%9%24%28%15%9%
495
September1st to 10thDay
21%8%20%26%18%8%
450
11th to 20thDay
16%422%33%18%8%
450
21st to endDay
25%12%23%23%12%5%
450
October1st to 10thDay
22%14%23%24%16%2
450
11th to 20thDay
27%16%28%21%7%1
450
21st to endDay
35%15%29%17%4
495
November1st to 10thDay
24%17%26%23%9%1
434
11th to 20thDay
32%21%31%12%31
180
21st to endDay
29%27%35%8%1
180
December1st to 10thDay
37%26%27%7%21
180
11th to 20thDay
38%21%31%8%2
180
21st to endDay
41%22%25%9%3
198
January1st to 10thNight
33%26%27%11%3
760
11th to 20thNight
33%25%28%13%2
736
21st to endNight
29%26%30%13%2
792
February1st to 10thNight
33%23%28%14%2
720
11th to 20thNight
31%29%31%8%1
703
21st to endNight
33%25%27%14%1
592
March1st to 10thNight
29%21%32%17%2
720
11th to 20thNight
29%24%26%15%6%
720
21st to endNight
26%20%32%17%41
792
April1st to 10thNight
28%19%31%18%4
720
11th to 20thNight
24%18%32%19%8%
711
21st to endNight
22%15%32%26%5%
600
May1st to 10thNight
24%12%26%30%7%1
540
11th to 20thNight
22%9%31%31%7%
474
21st to endNight
13%6%28%30%21%2
389
June1st to 10thNight
14%5%30%36%15%1
360
11th to 20thNight
16%7%26%36%15%1
360
21st to endNight
14%5%30%37%14%1
360
July1st to 10thNight
15%319%42%18%3
350
11th to 20thNight
12%5%19%39%22%3
469
21st to endNight
14%5%19%39%23%1
591
August1st to 10thNight
11%418%42%23%2
537
11th to 20thNight
14%5%15%36%27%3
534
21st to endNight
13%5%18%37%21%4
746
September1st to 10thNight
17%6%19%33%21%4
720
11th to 20thNight
13%5%20%35%23%4
720
21st to endNight
20%11%22%27%17%3
720
October1st to 10thNight
20%9%25%28%16%2
720
11th to 20thNight
26%15%30%21%7%1
720
21st to endNight
35%13%27%21%41
792
November1st to 10thNight
20%15%28%27%8%1
740
11th to 20thNight
30%19%27%18%5%1
760
21st to endNight
32%19%29%16%4
760
December1st to 10thNight
37%22%24%13%3
760
11th to 20thNight
34%25%25%14%3
760
21st to endNight
30%25%29%15%1
836
Page generated at 2024-01-11 13:32:02. Version ac07

Copyright 2024 Attilla Danko


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