Port Hilford
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Port Hilford 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
26%
24011
7%
74775
4%
23954
29%
23954
8%
62472

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
14%
850
5%
2649
0%
847
19%
847
4%
2300
January11th to 20thNight
14%
818
5%
2569
1%
818
19%
818
5%
2223
January21st to endNight
15%
820
7%
2640
2%
820
21%
820
7%
2175
February1st to 10thNight
15%
720
6%
2340
2%
720
19%
720
6%
1955
February11th to 20thNight
12%
703
6%
2276
2%
700
17%
700
6%
1908
February21st to endNight
19%
592
9%
1812
5%
592
24%
592
8%
1513
March1st to 10thNight
17%
718
7%
2102
2%
718
21%
718
6%
1836
March11th to 20thNight
27%
720
9%
1980
5%
720
31%
720
10%
1644
March21st to endNight
24%
716
10%
2102
4%
716
30%
716
9%
1734
April1st to 10thNight
21%
540
8%
1800
6%
540
24%
540
8%
1505
April11th to 20thNight
31%
534
10%
1776
8%
534
35%
534
10%
1423
April21st to endNight
30%
540
9%
1670
5%
540
34%
540
10%
1377
May1st to 10thNight
27%
540
8%
1450
4%
540
30%
540
9%
1248
May11th to 20thNight
36%
532
10%
1417
6%
532
38%
532
11%
1197
May21st to endNight
29%
583
6%
1551
3%
582
31%
582
10%
1317
June1st to 10thNight
28%
540
4%
1440
2%
540
30%
540
8%
1272
June11th to 20thNight
35%
540
7%
1440
4%
540
35%
540
10%
1219
June21st to endNight
28%
540
2%
1440
1%
540
28%
540
5%
1324
July1st to 10thNight
40%
526
3%
1401
2%
526
41%
526
9%
1219
July11th to 20thNight
34%
522
4%
1392
2%
522
35%
522
8%
1217
July21st to endNight
34%
590
4%
1486
4%
558
34%
558
9%
1280
August1st to 10thNight
42%
538
5%
1529
4%
534
43%
534
9%
1299
August11th to 20thNight
42%
532
9%
1596
8%
532
44%
532
9%
1325
August21st to endNight
46%
594
10%
1965
7%
594
50%
594
12%
1522
September1st to 10thNight
43%
540
8%
1800
7%
540
46%
540
11%
1421
September11th to 20thNight
38%
540
12%
1800
10%
540
43%
540
11%
1387
September21st to endNight
33%
656
10%
2055
6%
656
37%
656
10%
1670
October1st to 10thNight
37%
720
12%
2160
5%
720
43%
720
14%
1660
October11th to 20thNight
32%
720
11%
2160
5%
720
37%
720
11%
1724
October21st to endNight
22%
837
7%
2466
3%
837
25%
837
7%
2074
November1st to 10thNight
25%
830
8%
2446
4%
830
28%
830
9%
2040
November11th to 20thNight
21%
850
9%
2660
4%
850
26%
850
8%
2201
November21st to endNight
18%
850
6%
2660
2%
850
21%
850
7%
2229
December1st to 10thNight
15%
850
7%
2660
2%
850
21%
850
5%
2265
December11th to 20thNight
11%
850
6%
3242
1%
849
17%
849
4%
2828
December21st to endNight
14%
920
2%
4843
1%
907
17%
907
2%
3941

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
23%10%46%5%3445%7%28%
74733
Night
24%10%46%5%3445%7%29%
75037
TransparencyDay
37%39%8%11%5%
74436
Night
38%38%8%11%5%
74869
SeeingDay
27%11%26%26%9%1
16356
Night
28%11%28%24%8%1
24028

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
19%12%5%9%5%35%45%8%25%
1516
11th to 20thDay
23%14%48%5%35%446%23%
1464
21st to endDay
16%10%37%6%45%5%7%10%29%
1714
February1st to 10thDay
22%10%5%7%6%36%5%5%6%26%
1620
11th to 20thDay
19%12%48%6%36%45%5%28%
1573
21st to endDay
13%12%5%6%7%35%46%7%33%
1443
March1st to 10thDay
18%11%5%8%6%35%5%5%7%28%
1850
11th to 20thDay
18%8%5%8%7%46%5%6%6%28%
1980
21st to endDay
18%13%5%8%6%35%5%5%5%28%
2253
April1st to 10thDay
26%10%47%434446%28%
2160
11th to 20thDay
27%9%35%5%2345%7%31%
2134
21st to endDay
27%10%45%43445%5%29%
2289
May1st to 10thDay
29%9%5%6%5%3445%6%25%
2510
11th to 20thDay
25%11%46%6%35%346%28%
2478
21st to endDay
25%11%45%5%3446%7%27%
2724
June1st to 10thDay
32%8%36%5%345%5%7%22%
2520
11th to 20thDay
26%9%36%5%4445%6%29%
2520
21st to endDay
34%12%45%5%34446%20%
2520
July1st to 10thDay
24%9%35%4345%6%10%27%
2520
11th to 20thDay
25%11%46%5%35%5%5%8%23%
2520
21st to endDay
29%9%36%445%5%5%8%23%
2745
August1st to 10thDay
20%8%36%5%345%6%9%31%
2397
11th to 20thDay
21%8%45%5%35%5%6%9%30%
2304
21st to endDay
19%8%35%5%2445%9%36%
2390
September1st to 10thDay
20%7%35%5%3346%7%37%
2160
11th to 20thDay
21%8%36%42446%8%34%
2160
21st to endDay
22%6%25%5%445%47%35%
1902
October1st to 10thDay
19%8%36%5%45%46%7%34%
1800
11th to 20thDay
22%7%35%5%445%6%7%32%
1800
21st to endDay
22%8%36%6%45%5%6%6%29%
1888
November1st to 10thDay
24%8%37%5%35%5%46%30%
1630
11th to 20thDay
23%8%46%6%35%5%5%7%28%
1520
21st to endDay
18%10%36%5%35%6%6%8%30%
1520
December1st to 10thDay
23%14%48%5%3445%7%23%
1520
11th to 20thDay
30%11%47%5%36%45%5%21%
1906
21st to endDay
22%11%6%8%5%3445%6%26%
2783
January1st to 10thNight
21%13%47%5%35%46%7%27%
2649
11th to 20thNight
24%12%37%6%345%47%25%
2569
21st to endNight
17%10%5%7%6%25%47%7%30%
2640
February1st to 10thNight
22%10%5%8%5%445%5%6%27%
2340
11th to 20thNight
19%11%48%7%45%5%5%6%27%
2273
21st to endNight
12%12%6%8%6%35%5%5%6%31%
1812
March1st to 10thNight
17%12%5%10%6%36%447%26%
2093
11th to 20thNight
20%9%5%6%5%35%447%32%
1979
21st to endNight
22%10%5%6%7%34346%31%
2102
April1st to 10thNight
29%12%45%434346%27%
1800
11th to 20thNight
24%9%35%5%3446%6%31%
1776
21st to endNight
29%9%344345%5%5%28%
1670
May1st to 10thNight
32%8%36%434346%27%
1450
11th to 20thNight
27%8%35%5%245%46%32%
1416
21st to endNight
23%12%37%435%45%8%27%
1550
June1st to 10thNight
33%11%37%5%34446%22%
1440
11th to 20thNight
28%8%35%5%2335%6%30%
1440
21st to endNight
37%13%36%433235%20%
1440
July1st to 10thNight
25%10%37%425%5%5%9%25%
1440
11th to 20thNight
28%13%5%6%435%5%5%6%21%
1440
21st to endNight
28%15%46%425%45%6%21%
1573
August1st to 10thNight
21%11%36%5%345%5%6%30%
1540
11th to 20thNight
22%10%36%425%5%5%8%30%
1596
21st to endNight
22%6%25%32435%8%40%
1965
September1st to 10thNight
19%7%35%434447%38%
1800
11th to 20thNight
23%7%34323347%39%
1800
21st to endNight
22%9%35%5%3335%5%37%
2055
October1st to 10thNight
20%6%245%35%45%7%39%
2160
11th to 20thNight
23%6%244345%5%7%37%
2160
21st to endNight
25%9%35%5%35%45%6%30%
2466
November1st to 10thNight
23%10%35%5%2445%7%32%
2446
11th to 20thNight
23%9%36%5%35%45%7%30%
2660
21st to endNight
21%10%36%5%35%5%5%7%30%
2660
December1st to 10thNight
26%12%46%5%34446%25%
2660
11th to 20thNight
32%10%5%6%5%33345%25%
3293
21st to endNight
28%11%48%424446%24%
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
39%42%8%9%2
1517
11th to 20thDay
40%44%6%6%3
1464
21st to endDay
32%41%8%13%6%
1714
February1st to 10thDay
39%39%7%8%7%
1620
11th to 20thDay
38%39%9%10%41
1581
21st to endDay
35%39%8%11%5%2
1443
March1st to 10thDay
38%39%6%11%6%
1854
11th to 20thDay
34%40%8%12%41
1980
21st to endDay
37%38%8%11%5%1
2253
April1st to 10thDay
37%39%6%10%6%1
2160
11th to 20thDay
35%36%6%12%10%1
2134
21st to endDay
37%38%7%12%5%1
2289
May1st to 10thDay
41%38%8%8%5%1
2510
11th to 20thDay
39%39%6%12%4
2482
21st to endDay
36%39%8%11%5%
2724
June1st to 10thDay
44%39%8%7%2
2520
11th to 20thDay
38%38%7%11%5%
2520
21st to endDay
47%39%5%5%3
2520
July1st to 10thDay
35%41%12%8%4
2450
11th to 20thDay
38%40%9%10%3
2444
21st to endDay
37%41%10%9%3
2592
August1st to 10thDay
34%40%10%12%4
2383
11th to 20thDay
32%40%9%14%5%
2304
21st to endDay
29%39%10%16%6%
2390
September1st to 10thDay
31%38%8%15%7%1
2160
11th to 20thDay
30%39%8%14%7%1
2160
21st to endDay
33%39%6%14%8%
1902
October1st to 10thDay
30%39%9%16%6%1
1800
11th to 20thDay
34%40%10%14%3
1800
21st to endDay
38%40%8%10%4
1888
November1st to 10thDay
33%42%7%13%5%
1630
11th to 20thDay
32%42%9%12%5%
1520
21st to endDay
33%42%11%10%4
1520
December1st to 10thDay
40%41%8%9%2
1520
11th to 20thDay
48%34%8%7%2
1905
21st to endDay
47%27%18%7%1
2783
January1st to 10thNight
40%42%8%8%2
2649
11th to 20thNight
37%43%8%8%3
2569
21st to endNight
34%40%11%10%4
2640
February1st to 10thNight
38%38%9%9%5%1
2340
11th to 20thNight
38%39%9%9%41
2276
21st to endNight
37%38%8%12%41
1812
March1st to 10thNight
42%38%6%8%5%
2102
11th to 20thNight
35%38%9%12%41
1980
21st to endNight
36%37%6%12%6%2
2102
April1st to 10thNight
39%37%7%10%6%1
1800
11th to 20thNight
35%37%5%12%9%1
1776
21st to endNight
36%38%7%10%8%1
1670
May1st to 10thNight
41%36%6%13%4
1450
11th to 20thNight
37%38%6%13%6%
1417
21st to endNight
37%39%9%11%4
1551
June1st to 10thNight
43%38%5%11%3
1440
11th to 20thNight
38%37%7%9%8%
1440
21st to endNight
48%39%45%3
1440
July1st to 10thNight
39%40%9%8%3
1401
11th to 20thNight
41%39%6%9%5%
1392
21st to endNight
37%40%10%9%3
1486
August1st to 10thNight
38%38%8%12%3
1529
11th to 20thNight
37%37%8%13%4
1596
21st to endNight
28%40%10%17%6%
1965
September1st to 10thNight
31%39%9%14%7%
1800
11th to 20thNight
30%38%8%14%11%
1800
21st to endNight
36%36%5%14%8%1
2055
October1st to 10thNight
27%38%11%16%7%
2160
11th to 20thNight
31%38%10%17%3
2160
21st to endNight
38%39%8%10%6%
2466
November1st to 10thNight
32%43%8%11%6%
2446
11th to 20thNight
33%42%9%11%6%
2660
21st to endNight
35%42%11%10%2
2660
December1st to 10thNight
37%42%8%10%4
2660
11th to 20thNight
47%34%8%10%2
3295
21st to endNight
50%28%11%10%1
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
25%19%32%18%4
370
11th to 20thDay
28%16%34%18%5%
349
21st to endDay
23%17%36%19%6%
374
February1st to 10thDay
26%19%33%20%1
340
11th to 20thDay
27%22%28%20%3
336
21st to endDay
19%17%37%23%5%
280
March1st to 10thDay
22%13%38%24%4
364
11th to 20thDay
18%16%36%24%6%
420
21st to endDay
22%16%35%19%7%
462
April1st to 10thDay
31%12%31%22%3
420
11th to 20thDay
29%10%33%22%6%1
412
21st to endDay
28%8%25%28%9%1
420
May1st to 10thDay
33%7%30%24%42
593
11th to 20thDay
27%5%24%33%10%2
624
21st to endDay
32%8%21%30%8%1
680
June1st to 10thDay
37%422%27%9%
630
11th to 20thDay
27%6%22%33%10%1
630
21st to endDay
42%6%13%28%10%1
630
July1st to 10thDay
32%5%15%35%12%
620
11th to 20thDay
33%6%15%32%14%
618
21st to endDay
33%5%17%31%13%1
685
August1st to 10thDay
22%420%37%14%3
516
11th to 20thDay
24%6%22%31%14%3
439
21st to endDay
20%7%21%30%21%2
495
September1st to 10thDay
18%8%26%30%16%2
450
11th to 20thDay
26%7%24%30%11%1
450
21st to endDay
25%6%26%27%12%4
381
October1st to 10thDay
20%8%26%30%13%3
360
11th to 20thDay
23%9%27%26%14%1
360
21st to endDay
25%12%35%20%7%1
396
November1st to 10thDay
20%14%32%25%7%2
365
11th to 20thDay
26%21%29%18%6%1
370
21st to endDay
23%18%36%18%5%1
370
December1st to 10thDay
33%15%28%20%4
370
11th to 20thDay
30%27%25%16%2
370
21st to endDay
24%18%35%17%6%1
407
January1st to 10thNight
27%19%34%17%3
850
11th to 20thNight
28%17%34%17%4
818
21st to endNight
22%17%40%16%5%
820
February1st to 10thNight
27%17%35%19%2
720
11th to 20thNight
25%19%38%16%2
703
21st to endNight
18%15%41%19%7%
592
March1st to 10thNight
23%14%38%20%4
720
11th to 20thNight
24%13%29%23%11%1
720
21st to endNight
25%12%29%27%6%
716
April1st to 10thNight
34%10%27%23%6%
540
11th to 20thNight
28%7%30%27%8%1
534
21st to endNight
32%5%27%27%8%1
540
May1st to 10thNight
36%425%26%9%1
540
11th to 20thNight
30%5%23%27%13%2
532
21st to endNight
30%6%26%30%7%1
583
June1st to 10thNight
40%418%29%9%
540
11th to 20thNight
32%5%18%34%10%1
540
21st to endNight
39%6%17%27%10%1
540
July1st to 10thNight
31%413%36%14%1
526
11th to 20thNight
34%416%31%16%
522
21st to endNight
36%5%15%30%14%1
590
August1st to 10thNight
26%5%14%36%16%2
538
11th to 20thNight
25%417%35%17%2
532
21st to endNight
23%319%31%22%2
594
September1st to 10thNight
23%424%31%16%2
540
11th to 20thNight
24%5%23%31%16%1
540
21st to endNight
27%6%26%29%9%2
656
October1st to 10thNight
23%7%27%31%10%2
720
11th to 20thNight
25%9%29%25%11%1
720
21st to endNight
30%13%30%21%5%
837
November1st to 10thNight
27%11%32%24%5%2
830
11th to 20thNight
27%17%29%20%6%
850
21st to endNight
26%17%33%19%4
850
December1st to 10thNight
33%16%31%16%4
850
11th to 20thNight
32%20%32%12%3
850
21st to endNight
29%17%33%17%3
935
Page generated at 2024-01-11 05:22:36. Version ac07

Copyright 2024 Attilla Danko


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