Cape Jellison
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cape Jellison clear sky chart from 2005-11-05 to 2017-09-23.

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%
14853
16%
46892
7%
14819
38%
14819
18%
31715

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
19%
720
18%
2506
7%
716
35%
716
15%
1614
January16th to endNight
13%
768
17%
2667
3%
768
31%
768
13%
1770
February1st to 15thNight
16%
703
15%
2275
4%
701
29%
701
13%
1589
February16th to endNight
18%
631
18%
1893
4%
631
35%
631
17%
1293
March1st to 15thNight
17%
720
17%
2094
4%
720
31%
720
17%
1496
March16th to endNight
26%
768
19%
2112
7%
768
36%
768
21%
1447
April1st to 15thNight
19%
676
17%
1764
4%
676
28%
676
18%
1290
April16th to endNight
28%
540
14%
1620
5%
540
35%
540
19%
1132
May1st to 15thNight
27%
540
12%
1620
7%
540
34%
540
18%
1177
May16th to endNight
29%
459
11%
1539
8%
458
36%
458
14%
1120
June1st to 15thNight
33%
360
9%
1260
7%
360
39%
360
13%
920
June16th to endNight
45%
360
9%
1260
10%
360
48%
360
18%
876
July1st to 15thNight
47%
340
10%
1322
13%
340
52%
340
19%
860
July16th to endNight
46%
391
11%
1432
12%
368
50%
368
17%
968
August1st to 15thNight
46%
539
11%
1608
8%
535
48%
535
22%
1089
August16th to endNight
47%
579
20%
1725
12%
579
52%
579
29%
1074
September1st to 15thNight
40%
720
17%
1920
8%
720
46%
720
32%
1232
September16th to endNight
43%
689
26%
1902
14%
689
52%
689
33%
1147
October1st to 15thNight
32%
660
20%
1897
9%
660
43%
660
23%
1257
October16th to endNight
23%
704
17%
2238
7%
704
35%
704
19%
1489
November1st to 15thNight
31%
700
19%
2277
11%
700
43%
700
20%
1499
November16th to endNight
24%
741
19%
2469
7%
741
39%
741
16%
1627
December1st to 15thNight
17%
750
16%
2640
4%
750
32%
750
14%
1814
December16th to endNight
14%
795
16%
2852
2%
795
31%
795
12%
1935

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
19%6%25%42445%7%37%
48005
Night
19%8%25%424446%37%
47065
TransparencyDay
46%5%11%21%13%1
47696
Night
48%410%21%13%1
46892
SeeingDay
24%12%29%21%9%2
6411
Night
24%11%29%24%8%
14854

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
17%7%35%324448%37%
1432
16th to endDay
17%9%26%32345%7%38%
1557
February1st to 15thDay
16%9%26%5%25%347%35%
1583
16th to endDay
13%10%37%436%5%5%6%33%
1580
March1st to 15thDay
20%8%35%5%34347%34%
1856
16th to endDay
17%8%245%3435%6%39%
2112
April1st to 15thDay
21%6%35%5%33346%36%
2182
16th to endDay
20%6%26%5%24346%37%
2340
May1st to 15thDay
24%7%25%43445%6%31%
2332
16th to endDay
23%6%35%42445%8%32%
2581
June1st to 15thDay
25%6%35%5%35%447%28%
2700
16th to endDay
22%6%25%5%35%45%7%32%
2700
July1st to 15thDay
15%5%245%245%6%9%38%
2554
16th to endDay
15%6%25%5%35%5%6%9%33%
2626
August1st to 15thDay
15%5%245%25%5%7%8%37%
2340
16th to endDay
12%5%1442445%8%45%
2474
September1st to 15thDay
12%4145%2335%7%48%
2040
16th to endDay
15%5%1331235%7%49%
1895
October1st to 15thDay
19%6%25%423336%41%
1733
16th to endDay
21%6%24423445%39%
1631
November1st to 15thDay
21%6%14225%346%39%
1581
16th to endDay
21%6%34323335%40%
1488
December1st to 15thDay
24%8%34313345%36%
1317
16th to endDay
22%11%35%323335%34%
1371
January1st to 15thNight
16%8%2442345%7%39%
2506
16th to endNight
14%10%36%5%34447%35%
2667
February1st to 15thNight
14%8%46%6%45%5%45%33%
2274
16th to endNight
16%9%35%5%34436%38%
1893
March1st to 15thNight
19%11%35%425%345%34%
2081
16th to endNight
17%6%25%5%2435%6%40%
2112
April1st to 15thNight
20%9%46%424446%33%
1764
16th to endNight
22%7%35%424345%35%
1620
May1st to 15thNight
23%8%25%5%24446%31%
1620
16th to endNight
23%9%35%5%35%446%28%
1537
June1st to 15thNight
26%9%25%5%33448%26%
1260
16th to endNight
20%7%35%5%33447%34%
1260
July1st to 15thNight
18%7%25%4245%5%8%34%
1402
16th to endNight
17%7%35%436%5%47%33%
1529
August1st to 15thNight
15%7%25%5%35%5%5%8%36%
1620
16th to endNight
13%5%2443345%8%44%
1725
September1st to 15thNight
16%5%13323445%48%
1920
16th to endNight
14%412423447%50%
1902
October1st to 15thNight
21%7%24314336%41%
1897
16th to endNight
21%6%25%424245%40%
2238
November1st to 15thNight
20%6%24424346%40%
2277
16th to endNight
19%6%34424446%39%
2469
December1st to 15thNight
23%9%34424245%36%
2640
16th to endNight
23%9%34323345%35%
2852

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
45%411%23%12%2
1433
16th to endDay
45%410%25%12%1
1557
February1st to 15thDay
49%412%19%12%
1586
16th to endDay
50%5%9%19%12%2
1580
March1st to 15thDay
51%410%18%13%2
1866
16th to endDay
45%49%17%17%4
2112
April1st to 15thDay
48%47%20%17%2
2182
16th to endDay
49%49%18%13%4
2340
May1st to 15thDay
53%5%7%18%13%2
2332
16th to endDay
51%5%11%20%10%1
2585
June1st to 15thDay
57%5%9%17%8%1
2700
16th to endDay
51%7%9%18%12%
2700
July1st to 15thDay
40%7%15%24%11%
2405
16th to endDay
44%7%14%22%9%
2461
August1st to 15thDay
41%8%13%26%9%
2327
16th to endDay
35%6%13%25%18%
2474
September1st to 15thDay
35%5%12%26%17%1
2040
16th to endDay
34%5%10%26%21%1
1895
October1st to 15thDay
44%5%9%25%14%1
1733
16th to endDay
46%411%24%12%
1631
November1st to 15thDay
46%5%11%22%13%
1581
16th to endDay
47%412%18%15%1
1488
December1st to 15thDay
50%412%22%9%
1317
16th to endDay
54%410%17%13%
1371
January1st to 15thNight
45%412%23%11%1
2506
16th to endNight
49%39%22%13%1
2667
February1st to 15thNight
51%411%20%11%
2275
16th to endNight
48%49%20%14%2
1893
March1st to 15thNight
53%37%20%12%2
2094
16th to endNight
45%39%18%18%3
2112
April1st to 15thNight
53%37%16%17%2
1764
16th to endNight
51%310%17%14%3
1620
May1st to 15thNight
53%5%9%15%14%1
1620
16th to endNight
56%49%19%8%1
1539
June1st to 15thNight
57%5%11%17%6%1
1260
16th to endNight
51%411%20%11%
1260
July1st to 15thNight
46%5%14%20%12%
1322
16th to endNight
51%413%21%7%1
1432
August1st to 15thNight
46%6%14%22%10%
1608
16th to endNight
37%6%13%26%16%
1725
September1st to 15thNight
37%412%28%15%1
1920
16th to endNight
34%48%31%20%
1902
October1st to 15thNight
45%39%24%15%1
1897
16th to endNight
47%310%24%13%
2238
November1st to 15thNight
45%412%21%14%1
2277
16th to endNight
47%411%20%15%1
2469
December1st to 15thNight
51%49%23%10%
2640
16th to endNight
51%310%20%12%
2852

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
16%26%31%23%1
60
16th to endDay
23%21%36%17%1
85
February1st to 15thDay
24%18%35%15%5%
237
16th to endDay
18%18%36%19%5%
239
March1st to 15thDay
27%18%33%17%2
270
16th to endDay
25%21%27%17%6%2
288
April1st to 15thDay
30%17%28%15%5%2
270
16th to endDay
24%17%34%15%6%2
270
May1st to 15thDay
31%14%30%15%5%2
288
16th to endDay
27%13%31%18%8%
370
June1st to 15thDay
29%7%26%24%10%
495
16th to endDay
28%427%28%10%1
495
July1st to 15thDay
20%7%30%27%11%2
339
16th to endDay
21%431%25%13%3
326
August1st to 15thDay
19%7%25%29%15%2
313
16th to endDay
17%6%24%30%16%4
332
September1st to 15thDay
18%8%29%25%14%4
315
16th to endDay
20%7%29%20%13%8%
283
October1st to 15thDay
22%12%22%19%17%5%
240
16th to endDay
28%14%30%20%41
240
November1st to 15thDay
24%13%27%23%8%2
235
16th to endDay
26%18%27%18%7%1
240
December1st to 15thDay
26%19%31%18%3
117
16th to endDay
32%29%29%6%1
64
January1st to 15thNight
22%22%31%18%4
720
16th to endNight
21%22%35%17%2
768
February1st to 15thNight
20%21%35%20%2
704
16th to endNight
20%19%35%20%3
631
March1st to 15thNight
27%15%33%19%3
720
16th to endNight
21%16%30%22%7%1
768
April1st to 15thNight
27%11%35%19%5%
676
16th to endNight
26%10%28%25%7%
540
May1st to 15thNight
27%433%25%7%1
540
16th to endNight
28%5%28%27%9%1
459
June1st to 15thNight
32%421%28%12%
360
16th to endNight
25%218%38%13%
360
July1st to 15thNight
23%20%37%16%1
340
16th to endNight
22%121%34%18%
391
August1st to 15thNight
20%220%38%16%
539
16th to endNight
17%125%32%20%1
579
September1st to 15thNight
20%329%28%15%2
720
16th to endNight
17%428%27%17%4
689
October1st to 15thNight
25%7%27%24%12%2
660
16th to endNight
24%13%34%20%6%
704
November1st to 15thNight
24%10%28%26%9%1
700
16th to endNight
23%17%28%20%9%
741
December1st to 15thNight
30%16%32%17%4
750
16th to endNight
30%18%30%16%2
795
Page generated at 2017-09-24 09:15:46. Version ac04

Copyright 2017 A. Danko


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