Port Hilford
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Port Hilford clear sky chart from 2005-11-05 to 2019-06-19.

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
23%
17718
11%
53983
5%
17674
29%
17674
13%
40483

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
14%
899
10%
2926
2%
896
23%
896
10%
2216
January16th to endNight
12%
930
10%
3034
2%
930
23%
930
10%
2272
February1st to 15thNight
11%
824
9%
2676
2%
821
19%
821
7%
2047
February16th to endNight
12%
735
9%
2302
3%
735
19%
735
10%
1766
March1st to 15thNight
17%
840
13%
2405
5%
840
25%
840
12%
1865
March16th to endNight
21%
837
13%
2405
6%
837
28%
837
14%
1802
April1st to 15thNight
21%
629
13%
2096
7%
629
30%
629
11%
1546
April16th to endNight
27%
623
11%
1974
6%
623
32%
623
13%
1488
May1st to 15thNight
24%
630
13%
1688
6%
630
30%
630
14%
1320
May16th to endNight
26%
657
10%
1752
4%
656
30%
656
15%
1353
June1st to 15thNight
26%
630
6%
1680
3%
630
27%
630
13%
1362
June16th to endNight
30%
597
5%
1592
4%
597
31%
597
13%
1265
July1st to 15thNight
38%
555
6%
1480
4%
555
39%
555
15%
1132
July16th to endNight
26%
613
6%
1547
5%
580
29%
580
10%
1285
August1st to 15thNight
39%
574
10%
1662
8%
570
41%
570
14%
1265
August16th to endNight
43%
621
14%
1996
9%
621
49%
621
19%
1353
September1st to 15thNight
40%
585
15%
1950
12%
585
45%
585
19%
1317
September16th to endNight
34%
667
18%
2135
12%
667
41%
667
20%
1419
October1st to 15thNight
30%
780
17%
2340
7%
780
38%
780
21%
1576
October16th to endNight
20%
852
13%
2561
5%
852
26%
852
14%
1882
November1st to 15thNight
23%
880
13%
2766
5%
880
31%
880
14%
2034
November16th to endNight
17%
900
10%
2940
3%
900
24%
900
11%
2183
December1st to 15thNight
13%
900
10%
2940
2%
900
23%
900
8%
2279
December16th to endNight
10%
960
8%
3136
1%
960
18%
960
8%
2456

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%9%36%5%3445%7%27%
54746
Night
23%9%35%424446%29%
54155
TransparencyDay
55%7%12%16%7%
54436
Night
55%6%12%16%7%
53983
SeeingDay
27%15%24%23%7%1
10020
Night
26%20%24%20%7%
17719

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 15thDay
18%11%46%435%45%8%26%
1672
16th to endDay
18%10%35%5%35%46%8%26%
1893
February1st to 15thDay
20%10%46%6%25%446%27%
1845
16th to endDay
15%11%46%6%25%45%6%28%
1742
March1st to 15thDay
20%9%5%8%6%25%447%26%
2201
16th to endDay
17%11%47%6%3445%5%28%
2523
April1st to 15thDay
25%9%35%424446%28%
2513
16th to endDay
29%10%34423345%27%
2590
May1st to 15thDay
27%10%46%434345%25%
2924
16th to endDay
26%10%45%5%23347%25%
3066
June1st to 15thDay
31%9%35%5%23446%23%
2940
16th to endDay
29%9%35%5%34445%23%
2777
July1st to 15thDay
24%7%344345%5%10%26%
2730
16th to endDay
29%8%36%435%448%19%
2877
August1st to 15thDay
22%8%35%5%2445%8%28%
2538
16th to endDay
18%7%3442445%9%35%
2558
September1st to 15thDay
21%6%35%42245%7%35%
2340
16th to endDay
19%5%2443445%8%36%
2151
October1st to 15thDay
20%7%36%44445%6%32%
1950
16th to endDay
21%7%25%6%45%45%6%29%
2013
November1st to 15thDay
25%7%35%424445%30%
1751
16th to endDay
21%9%36%6%245%5%7%28%
1680
December1st to 15thDay
22%12%47%4245%47%24%
1680
16th to endDay
23%11%46%5%3445%6%24%
1792
January1st to 15thNight
19%10%35%5%25%5%5%7%29%
2926
16th to endNight
20%10%36%5%2445%7%28%
3034
February1st to 15thNight
19%11%47%5%44445%27%
2675
16th to endNight
15%11%5%8%6%35%446%27%
2302
March1st to 15thNight
20%10%37%5%35%347%27%
2393
16th to endNight
21%9%5%5%6%34436%30%
2405
April1st to 15thNight
26%10%35%423346%28%
2096
16th to endNight
29%9%25%424445%27%
1974
May1st to 15thNight
32%8%35%424335%26%
1688
16th to endNight
25%9%36%324447%27%
1750
June1st to 15thNight
32%10%36%423336%22%
1680
16th to endNight
31%9%36%32335%6%24%
1592
July1st to 15thNight
23%9%36%4245%6%9%26%
1560
16th to endNight
30%11%46%4245%5%6%19%
1643
August1st to 15thNight
23%9%25%5%2445%6%29%
1673
16th to endNight
20%6%25%32435%8%37%
1996
September1st to 15thNight
21%5%24434447%37%
1950
16th to endNight
21%7%24423345%40%
2135
October1st to 15thNight
21%5%24424446%38%
2340
16th to endNight
24%6%2443445%6%31%
2561
November1st to 15thNight
24%8%25%434347%31%
2766
16th to endNight
23%8%36%424446%31%
2940
December1st to 15thNight
24%10%45%424446%26%
2940
16th to endNight
24%10%35%5%24447%26%
3136

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
55%9%12%15%5%
1673
16th to endDay
54%8%12%16%7%
1893
February1st to 15thDay
58%7%12%12%8%1
1848
16th to endDay
55%6%10%16%9%1
1742
March1st to 15thDay
56%6%11%16%7%1
2212
16th to endDay
54%6%11%17%8%1
2523
April1st to 15thDay
54%7%9%15%11%1
2513
16th to endDay
58%6%10%14%9%
2590
May1st to 15thDay
61%5%10%14%6%
2924
16th to endDay
60%5%9%16%7%
3070
June1st to 15thDay
63%7%9%13%5%
2940
16th to endDay
63%6%8%13%6%
2777
July1st to 15thDay
53%7%15%14%7%
2582
16th to endDay
64%7%11%11%4
2710
August1st to 15thDay
52%9%13%17%6%
2524
16th to endDay
43%8%16%21%8%
2558
September1st to 15thDay
46%7%13%22%10%
2340
16th to endDay
44%7%13%24%10%
2151
October1st to 15thDay
49%7%13%21%7%
1950
16th to endDay
54%7%14%17%6%
2013
November1st to 15thDay
54%6%12%17%7%
1751
16th to endDay
55%8%14%16%5%
1680
December1st to 15thDay
60%7%12%15%4
1680
16th to endDay
62%6%12%11%6%
1792
January1st to 15thNight
55%9%15%14%5%
2926
16th to endNight
55%8%14%16%5%
3034
February1st to 15thNight
59%7%12%12%7%
2676
16th to endNight
58%7%11%15%6%
2302
March1st to 15thNight
59%6%10%15%8%
2405
16th to endNight
56%5%9%18%9%1
2405
April1st to 15thNight
56%5%9%16%10%1
2096
16th to endNight
57%5%9%14%10%1
1974
May1st to 15thNight
61%37%18%6%1
1688
16th to endNight
57%5%10%18%6%
1752
June1st to 15thNight
64%5%8%14%6%
1680
16th to endNight
61%6%9%15%7%
1592
July1st to 15thNight
55%7%14%14%8%
1480
16th to endNight
66%6%11%10%4
1547
August1st to 15thNight
56%7%12%18%5%
1662
16th to endNight
45%7%15%23%7%
1996
September1st to 15thNight
46%6%13%22%10%
1950
16th to endNight
47%411%24%12%
2135
October1st to 15thNight
44%6%14%24%9%
2340
16th to endNight
53%7%12%19%7%
2561
November1st to 15thNight
53%7%14%16%8%
2766
16th to endNight
54%7%16%14%6%
2940
December1st to 15thNight
60%7%12%15%4
2940
16th to endNight
60%7%13%11%6%
3136

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
23%25%32%15%3
330
16th to endDay
25%23%33%14%3
352
February1st to 15thDay
26%27%29%16%
326
16th to endDay
23%20%32%18%4
290
March1st to 15thDay
20%19%37%17%5%
362
16th to endDay
23%18%32%20%5%
416
April1st to 15thDay
30%15%33%17%2
390
16th to endDay
30%11%26%23%7%1
379
May1st to 15thDay
33%12%24%21%5%3
610
16th to endDay
30%13%19%28%6%1
679
June1st to 15thDay
31%12%22%25%8%
645
16th to endDay
33%11%15%28%8%1
587
July1st to 15thDay
31%9%12%30%14%
550
16th to endDay
35%13%15%23%10%
594
August1st to 15thDay
27%7%20%27%12%4
408
16th to endDay
21%7%16%31%19%3
396
September1st to 15thDay
20%7%23%31%16%1
375
16th to endDay
25%8%23%29%11%2
343
October1st to 15thDay
21%11%29%24%11%2
315
16th to endDay
25%14%34%17%7%
336
November1st to 15thDay
19%23%27%20%7%2
325
16th to endDay
26%23%30%15%3
330
December1st to 15thDay
28%21%25%20%3
330
16th to endDay
26%25%29%15%2
352
January1st to 15thNight
21%28%31%16%2
900
16th to endNight
23%28%31%13%3
930
February1st to 15thNight
25%27%30%14%
824
16th to endNight
21%26%33%13%5%
735
March1st to 15thNight
23%24%28%16%6%
840
16th to endNight
22%24%25%21%6%
837
April1st to 15thNight
27%20%24%22%4
629
16th to endNight
27%18%23%23%7%
623
May1st to 15thNight
33%15%20%19%9%1
630
16th to endNight
27%17%21%24%7%1
657
June1st to 15thNight
33%16%16%26%6%
630
16th to endNight
31%17%13%27%8%1
597
July1st to 15thNight
28%12%11%31%14%
555
16th to endNight
35%16%12%22%13%
613
August1st to 15thNight
30%10%11%27%17%2
574
16th to endNight
21%9%17%32%17%1
621
September1st to 15thNight
22%10%20%29%15%1
585
16th to endNight
23%11%23%29%11%1
667
October1st to 15thNight
23%15%26%26%7%1
780
16th to endNight
27%18%30%17%5%
852
November1st to 15thNight
25%21%25%20%5%1
880
16th to endNight
25%27%26%16%4
900
December1st to 15thNight
28%26%28%12%4
900
16th to endNight
28%27%28%12%2
960
Page generated at 2019-06-20 09:02:30. Version ac04

Copyright 2019 A. Danko


Port Hilford Clear Sky Chart |Charts Home