Icefog Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Icefog Observatory clear sky chart from 2005-11-05 to 2017-10-31.

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
53%
13495
7%
46843
7%
13481
54%
13481
15%
34048

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
52%
877
7%
3374
7%
877
54%
877
14%
2409
January16th to endNight
57%
823
10%
3336
10%
823
59%
823
14%
2368
February1st to 15thNight
58%
726
15%
2754
14%
726
60%
726
21%
1748
February16th to endNight
51%
659
12%
2212
12%
659
52%
659
16%
1585
March1st to 15thNight
55%
582
16%
2190
18%
582
58%
582
20%
1413
March16th to endNight
61%
582
13%
2013
14%
581
62%
581
24%
1251
April1st to 15thNight
55%
539
4%
1582
3%
539
55%
539
18%
1167
April16th to endNight
66%
508
0%
1286
0%
508
66%
508
31%
860
May1st to 15thNight
58%
260
0%
981
0%
260
58%
260
16%
669
May16th to endNight
59%
188
0%
679
0%
187
59%
187
19%
441
June1st to 15thNight
53%
180
0%
399
0%
180
53%
180
17%
328
June16th to endNight
61%
180
0%
360
0%
180
61%
180
24%
291
July1st to 15thNight
60%
170
0%
403
0%
170
60%
170
17%
323
July16th to endNight
43%
188
0%
719
0%
177
42%
177
9%
567
August1st to 15thNight
50%
343
0%
1060
0%
342
50%
342
10%
870
August16th to endNight
47%
559
0%
1457
0%
559
47%
559
15%
1166
September1st to 15thNight
54%
540
3%
1677
4%
540
54%
540
16%
1237
September16th to endNight
42%
541
4%
1958
5%
541
43%
541
10%
1546
October1st to 15thNight
45%
711
6%
2286
5%
711
46%
711
12%
1824
October16th to endNight
53%
816
7%
2771
7%
816
53%
816
14%
2072
November1st to 15thNight
50%
730
6%
2843
6%
730
50%
730
12%
2106
November16th to endNight
50%
809
10%
3201
11%
809
51%
809
12%
2331
December1st to 15thNight
48%
960
9%
3462
8%
960
49%
960
13%
2591
December16th to endNight
53%
1024
5%
3840
5%
1024
53%
1024
11%
2885

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
13%9%48%7%45%5%6%7%28%
49023
Night
9%11%5%8%7%45%5%5%6%29%
46909
TransparencyDay
52%9%17%15%4
48589
Night
52%8%16%16%5%
46848
SeeingDay
15%311%24%28%15%
9074
Night
13%210%30%32%10%
13509

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
6%12%5%12%10%46%335%28%
574
16th to endDay
410%6%8%6%38%6%8%9%27%
887
February1st to 15thDay
410%6%11%7%35%7%5%433%
1110
16th to endDay
313%7%10%7%25%6%6%8%29%
1262
March1st to 15thDay
410%5%6%7%46%5%5%6%36%
1768
16th to endDay
37%5%7%6%35%46%7%42%
2205
April1st to 15thDay
6%12%6%8%7%45%6%7%7%27%
2363
16th to endDay
45%36%8%46%5%6%8%38%
2672
May1st to 15thDay
6%9%49%8%46%6%6%6%30%
2970
16th to endDay
10%7%36%6%36%6%6%8%33%
3431
June1st to 15thDay
15%8%49%7%5%6%5%6%6%24%
3561
16th to endDay
15%6%26%6%35%5%7%9%31%
3600
July1st to 15thDay
16%6%36%7%46%6%8%7%26%
3532
16th to endDay
24%7%48%6%36%5%6%6%19%
3401
August1st to 15thDay
23%9%37%6%35%5%6%6%22%
2895
16th to endDay
20%9%47%6%345%5%6%25%
2744
September1st to 15thDay
17%9%36%6%36%5%5%7%27%
2283
16th to endDay
21%13%5%8%6%345%5%421%
2000
October1st to 15thDay
12%16%6%8%7%3445%5%24%
1674
16th to endDay
11%13%48%6%345%7%6%27%
1450
November1st to 15thDay
8%11%5%11%8%5%5%5%7%5%24%
1015
16th to endDay
13%10%46%8%435%45%31%
745
December1st to 15thDay
9%13%7%9%326%46%7%27%
497
16th to endDay
414%6%10%7%25%5%7%6%28%
384
January1st to 15thNight
6%13%6%9%7%35%5%5%6%30%
3374
16th to endNight
5%10%6%8%8%47%6%6%8%28%
3336
February1st to 15thNight
210%5%10%6%3445%8%37%
2742
16th to endNight
412%7%10%7%45%5%5%7%29%
2212
March1st to 15thNight
310%49%6%46%446%39%
2190
16th to endNight
5%9%46%435%5%5%5%44%
2013
April1st to 15thNight
7%11%48%8%47%6%6%6%29%
1582
16th to endNight
46%35%7%45%6%8%7%40%
1286
May1st to 15thNight
7%7%36%8%5%6%6%5%7%32%
980
16th to endNight
10%7%35%6%35%5%5%10%35%
679
June1st to 15thNight
10%10%36%10%48%5%6%9%24%
399
16th to endNight
13%6%27%6%25%7%8%11%28%
360
July1st to 15thNight
11%7%36%5%38%10%7%10%24%
428
16th to endNight
22%11%37%6%346%46%22%
768
August1st to 15thNight
22%7%38%6%5%7%6%7%7%17%
1065
16th to endNight
22%8%36%7%336%45%28%
1457
September1st to 15thNight
16%8%37%6%45%5%6%7%29%
1677
16th to endNight
18%11%48%7%45%5%5%5%23%
1958
October1st to 15thNight
13%14%410%6%45%5%5%5%23%
2286
16th to endNight
10%14%5%8%6%45%45%7%29%
2771
November1st to 15thNight
8%13%6%10%7%35%5%5%6%27%
2843
16th to endNight
10%12%5%9%7%3445%6%29%
3201
December1st to 15thNight
8%15%6%10%6%35%45%6%27%
3462
16th to endNight
5%12%6%10%8%5%6%6%6%7%23%
3840

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
58%6%10%16%6%1
574
16th to endDay
50%8%17%15%6%1
887
February1st to 15thDay
50%7%9%20%10%1
1110
16th to endDay
50%7%13%17%10%
1262
March1st to 15thDay
46%6%13%20%10%2
1768
16th to endDay
38%8%18%20%12%1
2205
April1st to 15thDay
52%7%17%19%2
2363
16th to endDay
38%8%18%26%6%
2672
May1st to 15thDay
50%7%14%23%3
2970
16th to endDay
43%8%18%19%8%
3435
June1st to 15thDay
57%9%16%14%2
3561
16th to endDay
46%11%21%17%2
3600
July1st to 15thDay
52%12%20%12%1
3328
16th to endDay
62%12%17%7%
3187
August1st to 15thDay
60%11%21%6%
2875
16th to endDay
57%11%20%10%
2744
September1st to 15thDay
53%11%22%11%1
2283
16th to endDay
63%9%13%11%1
2000
October1st to 15thDay
59%10%16%9%3
1674
16th to endDay
53%10%20%13%1
1450
November1st to 15thDay
57%8%19%12%2
1015
16th to endDay
53%10%13%19%3
745
December1st to 15thDay
54%9%15%13%5%1
497
16th to endDay
49%12%21%13%2
384
January1st to 15thNight
52%8%14%16%5%2
3374
16th to endNight
52%8%15%16%6%
3336
February1st to 15thNight
44%5%12%22%12%1
2754
16th to endNight
52%7%13%16%9%
2212
March1st to 15thNight
45%5%11%22%10%3
2190
16th to endNight
39%7%15%20%15%1
2018
April1st to 15thNight
52%7%17%20%2
1582
16th to endNight
37%7%23%23%7%
1286
May1st to 15thNight
47%9%15%24%3
981
16th to endNight
43%8%16%21%9%
679
June1st to 15thNight
56%10%13%16%3
399
16th to endNight
48%13%18%17%2
360
July1st to 15thNight
51%14%19%11%2
403
16th to endNight
60%11%19%8%
719
August1st to 15thNight
62%11%16%9%
1060
16th to endNight
57%10%18%12%
1457
September1st to 15thNight
51%9%22%14%1
1677
16th to endNight
59%10%13%13%2
1958
October1st to 15thNight
58%10%17%9%2
2286
16th to endNight
53%10%20%12%2
2771
November1st to 15thNight
55%9%18%15%
2843
16th to endNight
54%8%12%18%5%
3201
December1st to 15thNight
55%9%15%13%5%
3462
16th to endNight
55%10%18%11%3
3840

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
6%36%43%26%13%
30
16th to endDay
5%17%34%30%21%
94
February1st to 15thDay
6%310%24%26%28%
210
16th to endDay
9%414%32%26%13%
211
March1st to 15thDay
7%412%30%28%17%
240
16th to endDay
7%11%27%34%20%
385
April1st to 15thDay
11%313%27%30%12%
443
16th to endDay
3412%29%36%13%
450
May1st to 15thDay
10%5%12%28%30%13%
468
16th to endDay
12%414%30%27%11%
771
June1st to 15thDay
15%316%28%26%9%
855
16th to endDay
14%29%20%33%19%
855
July1st to 15thDay
17%18%20%33%18%
801
16th to endDay
23%210%21%25%16%
691
August1st to 15thDay
23%112%21%26%13%
494
16th to endDay
26%310%20%25%13%
523
September1st to 15thDay
19%212%22%24%18%
475
16th to endDay
29%7%9%23%15%12%
307
October1st to 15thDay
22%413%18%22%19%
270
16th to endDay
16%29%20%28%22%
288
November1st to 15thDay
18%6%24%28%20%
121
16th to endDay
20%316%30%30%
30
December1st to 15thDay
10%6%23%33%26%
30
16th to endDay
9%6%18%21%31%12%
32
January1st to 15thNight
10%110%34%29%12%
882
16th to endNight
8%210%37%32%8%
823
February1st to 15thNight
6%210%34%33%12%
734
16th to endNight
9%313%39%29%4
659
March1st to 15thNight
10%214%37%30%4
582
16th to endNight
8%212%29%35%11%
582
April1st to 15thNight
10%312%33%33%6%
539
16th to endNight
6%110%32%42%5%
508
May1st to 15thNight
10%113%28%38%8%
261
16th to endNight
13%412%32%31%6%
188
June1st to 15thNight
15%311%32%32%4
180
16th to endNight
15%16%21%43%12%
180
July1st to 15thNight
13%210%24%41%8%
170
16th to endNight
25%27%23%31%9%
188
August1st to 15thNight
25%26%23%35%6%
343
16th to endNight
25%29%20%27%13%
559
September1st to 15thNight
20%28%26%31%11%
540
16th to endNight
22%413%23%29%5%
541
October1st to 15thNight
19%313%26%28%8%
711
16th to endNight
15%29%30%31%11%
816
November1st to 15thNight
15%19%31%30%11%
730
16th to endNight
14%18%28%32%14%
809
December1st to 15thNight
13%311%27%31%13%
960
16th to endNight
9%28%32%32%14%
1024
Page generated at 2017-11-01 13:23:31. Version ac04

Copyright 2017 A. Danko


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