Inlet Outlet Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Inlet Outlet Observatory clear sky chart from 2005-11-05 to 2018-10-27.

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
36%
16508
20%
51236
11%
16477
46%
16477
22%
32677

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
23%
780
20%
2716
10%
776
38%
776
20%
1668
January16th to endNight
19%
832
21%
2792
7%
832
37%
832
19%
1732
February1st to 15thNight
19%
764
17%
2400
5%
761
34%
761
19%
1544
February16th to endNight
22%
683
25%
2049
9%
683
42%
683
22%
1280
March1st to 15thNight
23%
780
20%
2331
10%
780
36%
780
22%
1507
March16th to endNight
28%
832
24%
2158
10%
832
40%
832
25%
1449
April1st to 15thNight
32%
778
18%
1946
6%
778
38%
778
25%
1334
April16th to endNight
37%
768
18%
1924
6%
768
42%
768
25%
1317
May1st to 15thNight
34%
567
17%
1737
9%
567
40%
567
18%
1200
May16th to endNight
44%
406
15%
1625
14%
406
50%
406
15%
1053
June1st to 15thNight
46%
390
15%
1560
17%
390
52%
390
17%
1010
June16th to endNight
60%
390
15%
1560
16%
390
65%
390
21%
873
July1st to 15thNight
58%
370
14%
1480
18%
370
60%
370
20%
874
July16th to endNight
55%
408
16%
1546
16%
386
62%
386
22%
897
August1st to 15thNight
59%
627
18%
1768
12%
625
62%
625
29%
1108
August16th to endNight
64%
828
18%
2070
10%
828
65%
828
32%
1352
September1st to 15thNight
53%
780
23%
1950
14%
780
55%
780
30%
1305
September16th to endNight
50%
777
23%
2138
17%
777
55%
777
27%
1396
October1st to 15thNight
43%
780
20%
2275
16%
780
49%
780
25%
1473
October16th to endNight
32%
816
23%
2536
13%
816
46%
816
26%
1551
November1st to 15thNight
31%
760
22%
2472
13%
760
45%
760
23%
1525
November16th to endNight
29%
780
22%
2561
11%
780
42%
780
20%
1609
December1st to 15thNight
24%
780
16%
2730
7%
780
37%
780
15%
1777
December16th to endNight
17%
832
21%
2912
6%
832
36%
832
18%
1843

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
15%5%2442445%7%41%
52322
Night
16%5%2442445%6%42%
51406
Cloud CoverDay
15%5%2442445%7%41%
52331
Night
15%6%2442445%6%42%
51412
TransparencyDay
40%6%12%22%15%2
52010
Night
41%411%22%16%2
51236
SeeingDay
18%9%19%27%19%5%
7257
Night
17%16%23%26%13%2
16509

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
14%7%24425%446%43%
1552
16th to endDay
17%7%23323347%44%
1781
February1st to 15thDay
15%7%345%23345%41%
1790
16th to endDay
15%5%345%3445%6%41%
1710
March1st to 15thDay
17%5%25%425%46%7%39%
1946
16th to endDay
18%7%25%42344443%
2417
April1st to 15thDay
18%6%24424347%40%
2332
16th to endDay
15%424435%45%6%42%
2310
May1st to 15thDay
19%6%24425%5%5%7%37%
2555
16th to endDay
20%5%2433445%7%38%
2842
June1st to 15thDay
17%5%24435%5%6%8%36%
2730
16th to endDay
9%4245%35%6%6%10%41%
2730
July1st to 15thDay
9%425%5%35%6%6%9%40%
2730
16th to endDay
10%5%25%446%7%7%8%38%
2878
August1st to 15thDay
9%425%5%245%6%9%43%
2420
16th to endDay
12%4143245%6%8%46%
2484
September1st to 15thDay
13%5%24423348%46%
2340
16th to endDay
14%5%35%42445%7%41%
2152
October1st to 15thDay
19%5%24433447%41%
2012
16th to endDay
16%5%2431235%7%47%
1945
November1st to 15thDay
18%6%2442335%5%43%
1716
16th to endDay
16%423424347%45%
1726
December1st to 15thDay
16%5%25%4245%5%7%41%
1560
16th to endDay
19%7%25%42445%6%38%
1664
January1st to 15thNight
18%5%23323447%43%
2716
16th to endNight
18%7%23423346%43%
2792
February1st to 15thNight
16%7%35%424445%41%
2399
16th to endNight
17%6%1342345%5%45%
2049
March1st to 15thNight
18%6%24423346%44%
2318
16th to endNight
18%6%25%5%13335%44%
2158
April1st to 15thNight
16%7%25%323446%42%
1946
16th to endNight
18%6%24424446%41%
1924
May1st to 15thNight
18%8%35%42445%6%36%
1737
16th to endNight
21%6%244245%5%7%36%
1623
June1st to 15thNight
19%5%25%4345%47%37%
1560
16th to endNight
9%4245%25%5%6%9%44%
1560
July1st to 15thNight
8%435%5%345%6%11%40%
1560
16th to endNight
8%425%5%35%5%8%8%41%
1642
August1st to 15thNight
8%425%5%345%6%8%46%
1778
16th to endNight
11%5%2442446%8%45%
2070
September1st to 15thNight
15%42442445%7%44%
1950
16th to endNight
15%6%34413347%44%
2138
October1st to 15thNight
18%5%25%424346%43%
2275
16th to endNight
17%5%24322335%48%
2536
November1st to 15thNight
16%5%25%423245%47%
2472
16th to endNight
15%6%243245%5%6%42%
2561
December1st to 15thNight
19%6%25%5%23447%37%
2730
16th to endNight
17%5%2432345%6%41%
2912

Percentage Cloud Cover SE (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
13%7%3443445%5%43%
1552
16th to endDay
17%6%23323447%43%
1781
February1st to 15thDay
16%7%35%5%23346%41%
1790
16th to endDay
15%5%35%43435%6%41%
1710
March1st to 15thDay
16%6%25%42445%7%40%
1956
16th to endDay
18%6%24424435%42%
2416
April1st to 15thDay
18%5%24335%347%40%
2332
16th to endDay
15%5%15%4245%5%8%41%
2310
May1st to 15thDay
18%6%244245%6%7%36%
2555
16th to endDay
20%5%2442445%8%37%
2842
June1st to 15thDay
16%5%245%35%5%6%8%36%
2730
16th to endDay
9%4245%46%5%6%9%41%
2730
July1st to 15thDay
8%425%5%36%6%6%9%40%
2730
16th to endDay
10%5%245%36%6%8%10%36%
2878
August1st to 15thDay
9%425%5%245%6%9%43%
2420
16th to endDay
11%4243245%6%8%45%
2484
September1st to 15thDay
13%5%2442335%8%45%
2340
16th to endDay
14%6%36%42445%7%40%
2152
October1st to 15thDay
18%5%25%423446%41%
2012
16th to endDay
16%5%24213247%48%
1945
November1st to 15thDay
18%5%244235%45%43%
1716
16th to endDay
15%424424436%46%
1726
December1st to 15thDay
14%6%25%4245%46%42%
1560
16th to endDay
19%7%25%324447%38%
1664
January1st to 15thNight
18%5%24423346%43%
2716
16th to endNight
17%7%24423347%43%
2792
February1st to 15thNight
15%8%25%414446%42%
2392
16th to endNight
16%6%24323446%45%
2049
March1st to 15thNight
18%5%25%423245%44%
2331
16th to endNight
17%7%25%32333445%
2158
April1st to 15thNight
16%7%25%423346%42%
1946
16th to endNight
17%6%35%424447%40%
1924
May1st to 15thNight
18%8%35%5%3436%7%35%
1737
16th to endNight
20%6%24424447%36%
1623
June1st to 15thNight
19%5%345%24447%37%
1560
16th to endNight
8%4145%45%5%6%10%43%
1560
July1st to 15thNight
8%5%26%5%25%6%6%10%40%
1560
16th to endNight
7%5%345%36%47%9%40%
1642
August1st to 15thNight
8%6%145%2346%8%46%
1778
16th to endNight
10%5%245%245%6%7%45%
2070
September1st to 15thNight
15%415%424447%44%
1950
16th to endNight
15%7%3432335%6%43%
2138
October1st to 15thNight
17%5%2442245%5%44%
2275
16th to endNight
16%5%1442334449%
2536
November1st to 15thNight
16%5%25%423335%47%
2472
16th to endNight
15%5%25%42445%6%42%
2561
December1st to 15thNight
19%6%25%5%2435%6%38%
2730
16th to endNight
17%6%24434446%41%
2912

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
42%5%12%23%13%3
1553
16th to endDay
40%313%25%13%2
1781
February1st to 15thDay
44%5%11%22%14%2
1793
16th to endDay
43%410%25%14%1
1710
March1st to 15thDay
42%5%13%22%13%2
1956
16th to endDay
43%49%21%16%3
2417
April1st to 15thDay
43%5%10%22%13%4
2332
16th to endDay
40%6%10%19%21%2
2310
May1st to 15thDay
44%7%11%19%14%1
2555
16th to endDay
44%7%13%20%12%1
2846
June1st to 15thDay
42%9%13%21%12%1
2730
16th to endDay
35%9%13%23%15%1
2730
July1st to 15thDay
36%9%11%23%16%2
2581
16th to endDay
36%9%13%25%12%2
2711
August1st to 15thDay
34%8%14%25%16%
2406
16th to endDay
33%7%13%23%19%2
2484
September1st to 15thDay
35%6%13%22%20%1
2340
16th to endDay
40%6%9%19%21%1
2152
October1st to 15thDay
42%5%12%19%17%1
2012
16th to endDay
35%5%10%26%20%1
1945
November1st to 15thDay
43%312%22%17%1
1716
16th to endDay
39%411%25%16%2
1726
December1st to 15thDay
42%416%21%13%1
1560
16th to endDay
46%415%18%13%
1664
January1st to 15thNight
41%413%22%15%2
2716
16th to endNight
42%311%26%15%1
2792
February1st to 15thNight
43%414%21%14%2
2400
16th to endNight
40%39%25%18%3
2049
March1st to 15thNight
43%312%22%15%3
2331
16th to endNight
43%38%22%17%4
2158
April1st to 15thNight
42%410%20%17%2
1946
16th to endNight
42%5%8%17%22%3
1924
May1st to 15thNight
48%5%9%18%15%2
1737
16th to endNight
45%6%13%18%13%2
1625
June1st to 15thNight
45%7%11%18%16%
1560
16th to endNight
35%6%13%26%16%1
1560
July1st to 15thNight
37%8%15%21%14%2
1480
16th to endNight
35%8%15%26%11%2
1546
August1st to 15thNight
34%7%15%24%16%1
1768
16th to endNight
35%7%12%23%19%1
2070
September1st to 15thNight
39%5%10%24%18%1
1950
16th to endNight
41%46%22%22%2
2138
October1st to 15thNight
42%412%21%16%2
2275
16th to endNight
39%310%26%18%1
2536
November1st to 15thNight
41%310%21%18%4
2472
16th to endNight
41%411%24%14%2
2561
December1st to 15thNight
46%415%20%11%1
2730
16th to endNight
43%412%24%13%1
2912

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
17%448%18%10%
90
16th to endDay
28%433%26%8%
123
February1st to 15thDay
22%12%33%30%
216
16th to endDay
20%13%32%28%4
291
March1st to 15thDay
19%13%34%27%4
330
16th to endDay
21%15%28%25%6%1
352
April1st to 15thDay
17%12%30%27%10%1
330
16th to endDay
20%11%20%31%13%2
319
May1st to 15thDay
23%10%21%28%12%3
348
16th to endDay
28%9%7%25%24%5%
395
June1st to 15thDay
19%8%14%25%24%7%
375
16th to endDay
11%9%12%37%25%4
375
July1st to 15thDay
12%6%6%28%34%12%
365
16th to endDay
11%8%7%31%32%8%
390
August1st to 15thDay
12%5%5%33%32%11%
358
16th to endDay
10%45%28%34%16%
396
September1st to 15thDay
17%412%26%24%13%
375
16th to endDay
22%412%27%22%10%
374
October1st to 15thDay
25%5%14%22%24%6%
375
16th to endDay
14%10%30%24%16%3
358
November1st to 15thDay
17%12%25%24%18%1
280
16th to endDay
15%14%34%19%14%1
256
December1st to 15thDay
18%7%36%21%14%1
90
16th to endDay
28%6%37%23%4
96
January1st to 15thNight
17%22%31%23%3
780
16th to endNight
20%20%36%20%2
832
February1st to 15thNight
18%20%35%23%1
764
16th to endNight
19%21%32%24%2
683
March1st to 15thNight
19%19%33%22%5%
780
16th to endNight
18%18%27%25%7%1
832
April1st to 15thNight
17%19%25%30%6%
778
16th to endNight
16%17%22%32%10%1
768
May1st to 15thNight
22%17%17%29%11%1
567
16th to endNight
22%16%9%28%19%3
407
June1st to 15thNight
20%15%12%27%22%1
390
16th to endNight
8%16%7%40%25%1
390
July1st to 15thNight
9%11%9%35%30%4
370
16th to endNight
11%15%8%30%31%3
408
August1st to 15thNight
11%8%9%36%30%3
627
16th to endNight
12%8%7%32%31%8%
828
September1st to 15thNight
16%8%14%28%25%6%
780
16th to endNight
19%9%12%27%24%7%
777
October1st to 15thNight
20%10%18%26%20%3
780
16th to endNight
18%13%30%25%11%
816
November1st to 15thNight
16%17%27%22%14%2
760
16th to endNight
15%21%28%24%9%
780
December1st to 15thNight
22%21%26%20%8%1
780
16th to endNight
19%21%37%19%1
832
Page generated at 2018-10-28 08:41:06. Version ac04

Copyright 2018 A. Danko


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