East Point -- Saturna Island
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the East Point -- Saturna Island 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
38%
14526
9%
46782
7%
14497
41%
14497
14%
34701

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
26%
750
8%
2686
6%
746
29%
746
7%
2223
January16th to endNight
28%
777
7%
2715
5%
777
32%
777
7%
2199
February1st to 15thNight
26%
700
6%
2288
4%
700
29%
700
7%
1872
February16th to endNight
30%
632
10%
2041
8%
632
35%
632
11%
1577
March1st to 15thNight
23%
720
5%
2055
3%
720
24%
720
8%
1738
March16th to endNight
27%
768
6%
2078
3%
768
29%
768
8%
1758
April1st to 15thNight
36%
719
8%
1799
4%
719
38%
719
15%
1436
April16th to endNight
38%
513
10%
1593
7%
513
41%
513
12%
1223
May1st to 15thNight
49%
359
13%
1439
18%
359
53%
359
17%
886
May16th to endNight
52%
375
7%
1478
11%
374
54%
374
14%
982
June1st to 15thNight
47%
360
3%
1260
2%
360
48%
360
17%
862
June16th to endNight
49%
360
6%
1260
3%
360
50%
360
17%
828
July1st to 15thNight
67%
340
11%
1190
10%
340
70%
340
32%
625
July16th to endNight
71%
376
16%
1340
21%
354
79%
354
38%
614
August1st to 15thNight
71%
443
17%
1516
21%
441
72%
441
36%
747
August16th to endNight
66%
613
21%
1759
16%
613
69%
613
37%
990
September1st to 15thNight
69%
720
22%
1800
13%
720
71%
720
45%
1026
September16th to endNight
47%
688
17%
1896
11%
688
50%
688
21%
1351
October1st to 15thNight
42%
660
11%
1980
10%
660
44%
660
19%
1385
October16th to endNight
33%
704
7%
2188
4%
704
37%
704
10%
1728
November1st to 15thNight
23%
700
5%
2450
4%
700
26%
700
7%
2046
November16th to endNight
26%
720
6%
2520
4%
720
29%
720
7%
2048
December1st to 15thNight
22%
729
6%
2571
3%
729
26%
729
7%
2141
December16th to endNight
15%
800
6%
2880
2%
800
20%
800
6%
2416

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
18%8%36%5%34446%33%
48157
Night
22%8%36%5%34446%32%
46937
Cloud CoverDay
19%8%35%5%34446%33%
48157
Night
23%8%35%5%34445%31%
46940
TransparencyDay
50%9%16%16%6%1
47815
Night
54%8%13%15%6%1
46783
SeeingDay
18%11%11%23%25%10%
6154
Night
23%17%13%20%19%6%
14531

By Month

Percentage Cloud Cover NW (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
34%10%47%6%25%33415%
1253
16th to endDay
28%12%5%9%8%46%44412%
1507
February1st to 15thDay
28%12%38%7%3445%5%16%
1576
16th to endDay
21%11%5%7%6%45%5%5%7%20%
1433
March1st to 15thDay
28%12%5%9%6%34445%14%
1905
16th to endDay
23%12%48%8%45%5%4420%
2145
April1st to 15thDay
19%9%47%6%35%6%5%8%23%
2149
16th to endDay
18%9%36%5%45%6%5%7%25%
2364
May1st to 15thDay
13%6%26%6%345%5%7%37%
2511
16th to endDay
14%8%36%5%35%5%5%7%33%
2632
June1st to 15thDay
15%5%26%6%35%5%6%7%36%
2700
16th to endDay
14%5%36%5%245%5%7%40%
2700
July1st to 15thDay
6%3143235%46%57%
2700
16th to endDay
6%312213336%64%
2736
August1st to 15thDay
8%313313436%59%
2433
16th to endDay
8%414324448%51%
2442
September1st to 15thDay
7%5%25%424347%51%
2160
16th to endDay
19%7%36%6%33446%34%
1898
October1st to 15thDay
22%8%37%5%35%5%6%6%25%
1650
16th to endDay
26%12%37%5%3446%7%19%
1682
November1st to 15thDay
37%9%35%5%2443419%
1408
16th to endDay
30%9%5%7%6%25%445%17%
1440
December1st to 15thDay
27%14%5%7%7%245%2419%
1389
16th to endDay
29%13%47%5%35%45%6%14%
1344
January1st to 15thNight
34%9%37%5%3343420%
2686
16th to endNight
29%9%36%6%25%446%20%
2715
February1st to 15thNight
28%10%37%5%34445%22%
2276
16th to endNight
22%9%46%5%3445%7%26%
2041
March1st to 15thNight
29%11%36%5%35%44419%
2055
16th to endNight
26%10%5%6%6%35%5%45%19%
2074
April1st to 15thNight
19%9%36%6%445%6%6%26%
1799
16th to endNight
20%8%36%5%35%5%5%7%27%
1593
May1st to 15thNight
13%5%36%5%25%45%5%43%
1439
16th to endNight
12%7%36%6%4446%8%35%
1478
June1st to 15thNight
14%7%36%6%35%45%6%37%
1260
16th to endNight
11%6%26%5%3447%8%39%
1260
July1st to 15thNight
5%213224345%63%
1260
16th to endNight
5%112312345%67%
1433
August1st to 15thNight
421431345%7%61%
1524
16th to endNight
7%313323347%58%
1759
September1st to 15thNight
7%212313335%65%
1800
16th to endNight
16%5%26%7%33447%38%
1896
October1st to 15thNight
19%7%25%425%435%39%
1980
16th to endNight
28%8%25%5%345%5%6%24%
2188
November1st to 15thNight
35%8%36%5%34345%18%
2450
16th to endNight
27%11%5%7%5%34445%21%
2520
December1st to 15thNight
27%13%5%7%5%34445%19%
2571
16th to endNight
32%13%47%5%2433320%
2880

Percentage Cloud Cover SW (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
35%11%36%6%35%43416%
1253
16th to endDay
30%11%48%6%46%5%25%13%
1507
February1st to 15thDay
30%11%47%6%34445%16%
1576
16th to endDay
22%11%47%6%35%448%21%
1433
March1st to 15thDay
30%12%5%8%6%3443416%
1905
16th to endDay
24%11%48%7%345%45%20%
2145
April1st to 15thDay
19%10%46%5%46%5%6%7%24%
2149
16th to endDay
18%9%36%7%3446%7%26%
2364
May1st to 15thDay
14%7%25%5%35%5%5%7%37%
2511
16th to endDay
15%8%36%5%35%5%5%7%33%
2632
June1st to 15thDay
15%5%36%6%25%5%5%7%36%
2700
16th to endDay
14%6%345%345%5%6%39%
2700
July1st to 15thDay
7%323424346%57%
2700
16th to endDay
7%312213346%63%
2736
August1st to 15thDay
8%312323346%59%
2433
16th to endDay
9%41342445%8%51%
2442
September1st to 15thDay
9%5%25%433247%50%
2160
16th to endDay
20%7%25%5%4445%6%33%
1898
October1st to 15thDay
23%8%35%5%345%5%6%26%
1650
16th to endDay
27%11%46%5%3445%7%19%
1682
November1st to 15thDay
39%8%25%5%2333420%
1408
16th to endDay
31%10%47%434435%18%
1440
December1st to 15thDay
27%14%47%6%3443319%
1389
16th to endDay
31%13%47%5%35%445%15%
1344
January1st to 15thNight
36%9%36%42343421%
2685
16th to endNight
30%9%37%424347%20%
2715
February1st to 15thNight
29%10%46%5%34346%21%
2276
16th to endNight
24%10%36%5%23447%26%
2041
March1st to 15thNight
32%10%36%5%34445%18%
2055
16th to endNight
27%11%47%6%445%45%19%
2078
April1st to 15thNight
20%9%36%6%46%45%6%25%
1799
16th to endNight
21%9%37%5%35%5%6%5%26%
1593
May1st to 15thNight
13%5%25%6%24446%43%
1439
16th to endNight
13%7%35%6%345%6%8%34%
1478
June1st to 15thNight
16%6%36%5%3446%5%36%
1260
16th to endNight
13%6%35%5%35%5%6%7%37%
1260
July1st to 15thNight
6%313232345%62%
1260
16th to endNight
5%212223345%66%
1433
August1st to 15thNight
5%21341345%6%61%
1524
16th to endNight
7%314323348%56%
1759
September1st to 15thNight
7%212313236%64%
1800
16th to endNight
18%5%25%6%33446%38%
1896
October1st to 15thNight
20%6%25%424435%39%
1980
16th to endNight
28%8%35%5%4445%6%23%
2188
November1st to 15thNight
37%8%26%43434419%
2450
16th to endNight
28%12%47%5%2433422%
2520
December1st to 15thNight
28%12%5%6%5%23445%20%
2571
16th to endNight
32%14%45%5%2333320%
2880

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
72%7%8%6%4
1253
16th to endDay
72%10%8%6%1
1507
February1st to 15thDay
69%9%7%8%41
1576
16th to endDay
61%9%12%11%4
1433
March1st to 15thDay
71%8%9%8%1
1905
16th to endDay
65%8%13%11%1
2145
April1st to 15thDay
57%10%15%13%2
2149
16th to endDay
54%10%15%13%5%
2364
May1st to 15thDay
45%9%18%17%8%1
2511
16th to endDay
48%11%20%16%3
2636
June1st to 15thDay
45%9%21%16%5%1
2700
16th to endDay
42%9%22%19%4
2700
July1st to 15thDay
28%8%20%26%12%3
2541
16th to endDay
21%7%23%33%12%1
2566
August1st to 15thDay
27%7%21%30%10%2
2416
16th to endDay
30%9%23%27%7%1
2442
September1st to 15thDay
33%8%18%20%16%2
2160
16th to endDay
50%10%12%17%7%
1898
October1st to 15thDay
54%11%15%12%5%
1650
16th to endDay
63%11%14%8%2
1682
November1st to 15thDay
68%8%10%8%21
1408
16th to endDay
68%8%9%9%2
1440
December1st to 15thDay
71%6%5%9%6%
1389
16th to endDay
70%9%7%8%21
1344
January1st to 15thNight
67%7%9%9%4
2686
16th to endNight
64%9%11%11%21
2715
February1st to 15thNight
65%8%11%9%31
2288
16th to endNight
57%8%12%15%5%
2041
March1st to 15thNight
68%7%10%10%2
2055
16th to endNight
65%10%10%11%2
2078
April1st to 15thNight
57%9%14%15%3
1799
16th to endNight
56%9%12%15%6%
1593
May1st to 15thNight
40%7%17%20%11%1
1440
16th to endNight
44%10%20%18%5%
1478
June1st to 15thNight
46%8%20%17%42
1260
16th to endNight
43%8%17%22%5%2
1260
July1st to 15thNight
25%7%15%30%16%4
1190
16th to endNight
19%7%18%31%19%3
1340
August1st to 15thNight
22%6%20%30%15%4
1516
16th to endNight
26%6%21%30%11%3
1759
September1st to 15thNight
23%5%18%26%20%5%
1800
16th to endNight
46%7%13%20%9%1
1896
October1st to 15thNight
47%7%15%19%9%
1980
16th to endNight
60%9%16%10%3
2188
November1st to 15thNight
68%7%11%7%12
2450
16th to endNight
65%8%10%9%5%
2520
December1st to 15thNight
67%8%9%8%5%
2571
16th to endNight
70%6%9%8%4
2880

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
13%5%21%20%33%6%
60
16th to endDay
46%9%16%18%6%2
91
February1st to 15thDay
36%17%12%13%20%
236
16th to endDay
24%17%16%20%15%4
213
March1st to 15thDay
36%18%18%15%8%2
270
16th to endDay
30%15%17%23%9%3
288
April1st to 15thDay
21%13%13%26%17%7%
269
16th to endDay
16%13%14%32%18%4
270
May1st to 15thDay
17%12%8%30%25%5%
288
16th to endDay
14%10%8%21%27%17%
347
June1st to 15thDay
10%13%9%27%29%9%
495
16th to endDay
12%12%10%25%30%8%
495
July1st to 15thDay
6%9%6%22%38%17%
475
16th to endDay
410%5%20%37%21%
405
August1st to 15thDay
9%6%318%37%25%
315
16th to endDay
8%5%6%22%38%18%
332
September1st to 15thDay
10%5%10%28%31%13%
315
16th to endDay
18%7%10%29%26%7%
284
October1st to 15thDay
29%8%14%24%19%3
255
16th to endDay
30%9%18%20%17%3
207
November1st to 15thDay
51%21%25%1
60
16th to endDay
28%8%16%18%16%11%
60
December1st to 15thDay
43%6%25%18%6%
60
16th to endDay
34%9%29%12%12%1
64
January1st to 15thNight
32%21%13%16%14%2
750
16th to endNight
29%19%14%16%16%2
777
February1st to 15thNight
28%22%13%17%14%3
704
16th to endNight
23%21%16%21%13%3
632
March1st to 15thNight
32%21%17%14%10%4
720
16th to endNight
26%20%18%20%10%4
768
April1st to 15thNight
20%19%14%23%17%5%
719
16th to endNight
20%18%14%28%14%3
513
May1st to 15thNight
15%16%10%23%24%8%
360
16th to endNight
14%17%5%21%30%9%
375
June1st to 15thNight
14%17%10%26%23%8%
360
16th to endNight
14%17%10%25%22%9%
360
July1st to 15thNight
6%12%7%22%39%11%
340
16th to endNight
317%322%39%13%
376
August1st to 15thNight
7%9%417%39%22%
443
16th to endNight
9%8%6%20%42%12%
613
September1st to 15thNight
9%8%5%23%32%19%
720
16th to endNight
19%10%10%23%27%9%
688
October1st to 15thNight
21%10%19%20%18%9%
660
16th to endNight
31%12%14%22%14%5%
704
November1st to 15thNight
34%18%18%18%8%1
700
16th to endNight
29%22%14%18%11%3
720
December1st to 15thNight
31%22%15%19%10%
729
16th to endNight
33%22%23%13%6%1
800
Page generated at 2017-09-24 06:15:53. Version ac04

Copyright 2017 A. Danko


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