Hillsdale Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hillsdale Lake clear sky chart from 2005-11-05 to 2017-03-25.

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
42%
15353
23%
45408
14%
15306
50%
15306
31%
27433

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
31%
900
23%
2327
8%
895
41%
895
33%
1466
January16th to endNight
29%
960
25%
2496
9%
960
39%
960
32%
1581
February1st to 15thNight
24%
880
17%
2288
7%
876
30%
876
25%
1594
February16th to endNight
26%
660
24%
1922
9%
660
37%
660
29%
1181
March1st to 15thNight
32%
540
22%
1980
12%
540
45%
540
25%
1160
March16th to endNight
27%
558
16%
2046
11%
558
36%
558
20%
1326
April1st to 15thNight
32%
494
23%
1705
15%
494
47%
494
27%
971
April16th to endNight
32%
495
20%
1565
13%
495
44%
495
25%
1007
May1st to 15thNight
38%
495
21%
1485
16%
495
48%
495
26%
966
May16th to endNight
46%
515
17%
1541
13%
513
51%
513
30%
944
June1st to 15thNight
62%
495
21%
1328
13%
495
66%
495
42%
777
June16th to endNight
62%
495
23%
1370
15%
495
67%
495
51%
726
July1st to 15thNight
70%
465
18%
1395
15%
465
71%
465
40%
791
July16th to endNight
74%
522
23%
1468
23%
489
77%
489
43%
788
August1st to 15thNight
77%
494
26%
1475
30%
491
79%
491
42%
798
August16th to endNight
72%
525
24%
1660
28%
525
74%
525
38%
926
September1st to 15thNight
58%
495
25%
1707
28%
495
61%
495
29%
993
September16th to endNight
61%
492
29%
1815
26%
492
68%
492
33%
963
October1st to 15thNight
47%
649
29%
1969
21%
649
52%
649
35%
1132
October16th to endNight
40%
704
28%
2112
14%
704
51%
704
36%
1171
November1st to 15thNight
40%
760
30%
2160
15%
760
52%
760
37%
1225
November16th to endNight
33%
900
25%
2474
10%
900
44%
900
33%
1503
December1st to 15thNight
29%
900
19%
2520
8%
900
37%
900
26%
1662
December16th to endNight
29%
960
22%
2600
9%
960
39%
960
24%
1782

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
12%5%25%42445%7%44%
45537
Night
10%5%24324446%49%
45603
TransparencyDay
39%6%13%24%14%2
45237
Night
34%5%12%26%17%3
45408
SeeingDay
13%7%25%29%20%4
5099
Night
13%7%32%32%13%1
15353

By Month

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
10%6%26%5%24345%48%
1611
16th to endDay
12%7%46%42435%6%43%
1728
February1st to 15thDay
12%9%5%5%433336%41%
1575
16th to endDay
12%9%35%42435%6%41%
1563
March1st to 15thDay
11%8%46%5%345%5%6%36%
1980
16th to endDay
20%8%36%42334437%
2043
April1st to 15thDay
16%7%25%423335%43%
1913
16th to endDay
19%8%26%6%2444435%
2062
May1st to 15thDay
17%8%36%5%25%5%46%34%
2136
16th to endDay
16%5%35%5%26%45%8%36%
2222
June1st to 15thDay
9%3245%346%7%10%41%
2299
16th to endDay
6%3135%3446%10%50%
2254
July1st to 15thDay
9%3244345%6%9%45%
2145
16th to endDay
7%224435%5%6%10%46%
2284
August1st to 15thDay
7%314426%5%6%8%47%
2145
16th to endDay
8%4245%2345%8%48%
2190
September1st to 15thDay
14%5%24423447%46%
1922
16th to endDay
8%3143245%6%7%51%
1815
October1st to 15thDay
14%6%24322345%50%
1650
16th to endDay
13%424413245%53%
1760
November1st to 15thDay
10%423213347%55%
1695
16th to endDay
16%5%23213336%49%
1485
December1st to 15thDay
15%8%36%5%22346%41%
1440
16th to endDay
14%8%37%42435%6%39%
1620
January1st to 15thNight
8%7%24424446%50%
2327
16th to endNight
8%6%36%423446%50%
2496
February1st to 15thNight
10%9%36%5%34446%40%
2278
16th to endNight
11%6%25%423436%48%
1922
March1st to 15thNight
11%7%25%42335%6%47%
1980
16th to endNight
18%7%34323447%39%
2046
April1st to 15thNight
10%6%34423336%51%
1705
16th to endNight
15%6%34424336%44%
1565
May1st to 15thNight
14%5%2442446%7%42%
1484
16th to endNight
12%5%2422345%10%45%
1539
June1st to 15thNight
6%213235%6%7%9%52%
1328
16th to endNight
411331345%11%60%
1370
July1st to 15thNight
7%2124245%8%9%51%
1485
16th to endNight
5%313225%5%6%9%54%
1576
August1st to 15thNight
4213335%5%6%9%54%
1485
16th to endNight
7%315%324347%57%
1660
September1st to 15thNight
11%425%3245%46%49%
1707
16th to endNight
7%3144245%5%7%54%
1815
October1st to 15thNight
14%413213345%54%
1969
16th to endNight
10%42331333458%
2112
November1st to 15thNight
8%423423246%58%
2160
16th to endNight
15%5%24213235%53%
2474
December1st to 15thNight
16%6%36%323446%42%
2520
16th to endNight
15%9%37%423345%40%
2600

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
38%412%25%17%1
1612
16th to endDay
40%5%15%25%12%1
1728
February1st to 15thDay
45%5%14%24%9%1
1576
16th to endDay
43%314%24%11%2
1563
March1st to 15thDay
46%5%11%22%12%2
1980
16th to endDay
50%5%13%20%9%1
2045
April1st to 15thDay
44%410%24%15%
1913
16th to endDay
50%5%11%20%11%
2062
May1st to 15thDay
51%6%10%19%11%
2136
16th to endDay
46%7%15%19%9%
2226
June1st to 15thDay
35%10%15%23%13%1
2299
16th to endDay
27%7%17%28%17%1
2254
July1st to 15thDay
33%6%18%26%11%2
2006
16th to endDay
27%8%16%31%13%1
2129
August1st to 15thDay
30%8%15%25%16%1
2131
16th to endDay
33%7%13%24%14%6%
2190
September1st to 15thDay
38%5%12%21%17%5%
1922
16th to endDay
29%7%12%28%20%1
1815
October1st to 15thDay
35%410%24%20%4
1650
16th to endDay
34%411%25%19%4
1760
November1st to 15thDay
29%411%27%21%5%
1695
16th to endDay
37%310%29%19%
1485
December1st to 15thDay
44%314%26%9%
1440
16th to endDay
45%5%13%21%11%2
1620
January1st to 15thNight
34%414%25%18%1
2327
16th to endNight
35%5%13%27%16%2
2496
February1st to 15thNight
44%5%11%23%12%1
2288
16th to endNight
37%412%24%18%2
1922
March1st to 15thNight
37%5%11%23%16%4
1980
16th to endNight
45%5%12%23%11%1
2046
April1st to 15thNight
34%49%26%21%3
1705
16th to endNight
41%410%25%16%1
1565
May1st to 15thNight
40%6%13%23%14%1
1485
16th to endNight
34%7%18%24%12%2
1541
June1st to 15thNight
25%7%18%30%15%2
1328
16th to endNight
19%5%15%31%23%3
1370
July1st to 15thNight
25%7%16%31%14%4
1395
16th to endNight
23%6%14%31%21%2
1468
August1st to 15thNight
23%7%14%32%18%4
1475
16th to endNight
28%5%9%24%24%7%
1660
September1st to 15thNight
34%5%11%21%19%7%
1707
16th to endNight
27%7%9%27%24%3
1815
October1st to 15thNight
32%39%24%23%6%
1969
16th to endNight
29%39%29%21%4
2112
November1st to 15thNight
29%311%24%23%7%
2160
16th to endNight
35%29%30%19%2
2474
December1st to 15thNight
41%5%14%25%12%
2520
16th to endNight
45%411%21%12%3
2600

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
21%15%40%18%4
90
16th to endDay
17%13%45%16%5%1
96
February1st to 15thDay
6%26%41%20%5%
90
16th to endDay
14%20%39%16%8%
81
March1st to 15thDay
15%18%50%13%2
90
16th to endDay
19%20%34%21%3
78
April1st to 15thDay
19%10%35%23%9%
152
16th to endDay
20%13%34%21%7%1
292
May1st to 15thDay
17%10%35%24%10%1
393
16th to endDay
19%7%29%25%13%4
437
June1st to 15thDay
9%5%27%32%20%4
420
16th to endDay
7%324%34%26%4
420
July1st to 15thDay
12%214%40%25%5%
400
16th to endDay
5%12%35%38%6%
445
August1st to 15thDay
7%7%39%38%6%
418
16th to endDay
11%214%29%34%8%
358
September1st to 15thDay
13%112%39%26%6%
197
16th to endDay
4423%35%18%13%
90
October1st to 15thDay
8%6%23%37%14%8%
90
16th to endDay
9%5%42%30%11%1
96
November1st to 15thDay
8%7%20%34%20%8%
90
16th to endDay
36%12%27%18%31
90
December1st to 15thDay
18%13%42%16%5%3
90
16th to endDay
23%19%32%21%2
96
January1st to 15thNight
12%13%41%27%6%
900
16th to endNight
11%11%42%29%4
960
February1st to 15thNight
15%10%42%26%3
880
16th to endNight
15%12%41%25%3
660
March1st to 15thNight
15%8%38%29%6%
540
16th to endNight
22%9%38%24%5%
558
April1st to 15thNight
14%11%38%28%6%
494
16th to endNight
19%7%36%27%8%
495
May1st to 15thNight
16%6%33%30%12%
495
16th to endNight
14%331%31%16%2
515
June1st to 15thNight
6%224%44%20%1
495
16th to endNight
4128%45%18%1
495
July1st to 15thNight
8%114%47%26%2
465
16th to endNight
5%110%43%36%1
522
August1st to 15thNight
419%45%37%2
494
16th to endNight
7%111%37%38%4
525
September1st to 15thNight
12%219%39%22%3
495
16th to endNight
8%319%38%25%5%
492
October1st to 15thNight
16%428%29%18%2
649
16th to endNight
13%8%36%29%11%
704
November1st to 15thNight
10%10%36%29%13%
760
16th to endNight
18%11%35%27%6%
900
December1st to 15thNight
19%10%37%26%4
900
16th to endNight
20%9%34%30%5%
960
Page generated at 2017-03-26 12:16:40. Version ac04

Copyright 2017 A. Danko


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