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 2017-12-02.

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%
16187
23%
47953
14%
16140
50%
16140
32%
28896

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
26%
576
15%
2112
10%
576
35%
576
19%
1389
April1st to 15thNight
32%
539
21%
1860
14%
539
46%
539
27%
1065
April16th to endNight
31%
540
20%
1707
14%
540
43%
540
24%
1115
May1st to 15thNight
39%
540
20%
1620
15%
540
48%
540
27%
1042
May16th to endNight
46%
563
18%
1685
15%
561
52%
561
31%
1022
June1st to 15thNight
63%
540
20%
1449
12%
540
67%
540
42%
844
June16th to endNight
61%
540
25%
1495
15%
540
66%
540
51%
794
July1st to 15thNight
71%
510
17%
1530
15%
510
72%
510
40%
865
July16th to endNight
75%
564
25%
1594
25%
531
77%
531
44%
852
August1st to 15thNight
78%
539
24%
1610
29%
536
79%
536
42%
871
August16th to endNight
72%
573
27%
1812
31%
573
74%
573
38%
1007
September1st to 15thNight
60%
540
25%
1862
27%
540
64%
540
31%
1052
September16th to endNight
61%
537
29%
1980
27%
537
69%
537
33%
1050
October1st to 15thNight
45%
708
27%
2148
20%
708
50%
708
34%
1256
October16th to endNight
40%
768
30%
2304
16%
768
52%
768
38%
1259
November1st to 15thNight
38%
825
28%
2345
14%
825
49%
825
36%
1354
November16th to endNight
33%
975
26%
2680
11%
975
45%
975
34%
1620
December1st to 15thNight
29%
910
19%
2547
8%
910
38%
910
26%
1675
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%
48484
Night
10%5%24324446%49%
48148
TransparencyDay
38%6%13%24%14%2
48184
Night
34%5%12%26%18%3
47953
SeeingDay
13%7%25%29%20%4
6123
Night
13%7%31%32%13%1
16187

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
21%9%36%42334435%
2110
April1st to 15thDay
16%7%25%423345%42%
2088
16th to endDay
19%8%26%6%3444435%
2250
May1st to 15thDay
17%8%26%5%245%46%36%
2331
16th to endDay
15%435%5%25%45%8%37%
2430
June1st to 15thDay
9%3245%246%7%9%43%
2508
16th to endDay
5%2135%3446%10%51%
2459
July1st to 15thDay
9%3244345%6%9%47%
2340
16th to endDay
7%2144345%6%9%48%
2466
August1st to 15thDay
7%314426%5%6%9%47%
2340
16th to endDay
8%4245%245%5%8%48%
2390
September1st to 15thDay
12%4245%23447%48%
2096
16th to endDay
9%3243245%6%7%51%
1980
October1st to 15thDay
14%6%2432235%6%49%
1800
16th to endDay
12%423423245%54%
1920
November1st to 15thDay
11%5%24313337%53%
1840
16th to endDay
15%5%23213336%50%
1609
December1st to 15thDay
15%8%36%5%22346%42%
1450
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%8%35%323447%38%
2112
April1st to 15thNight
11%5%34423336%50%
1860
16th to endNight
16%6%35%424336%43%
1707
May1st to 15thNight
14%5%2442346%7%44%
1619
16th to endNight
11%5%2422345%9%47%
1683
June1st to 15thNight
5%213325%6%6%8%53%
1449
16th to endNight
411332345%11%60%
1495
July1st to 15thNight
7%212425%5%7%9%51%
1620
16th to endNight
5%313225%5%5%9%54%
1702
August1st to 15thNight
4213325%5%6%9%54%
1620
16th to endNight
6%315%424336%57%
1812
September1st to 15thNight
10%425%3245%46%51%
1862
16th to endNight
7%3144245%5%7%54%
1980
October1st to 15thNight
14%413323345%53%
2148
16th to endNight
10%42321333459%
2304
November1st to 15thNight
9%423423236%56%
2345
16th to endNight
14%5%24223235%53%
2680
December1st to 15thNight
15%6%36%323446%43%
2547
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
52%5%12%19%9%1
2112
April1st to 15thDay
43%411%23%15%
2088
16th to endDay
51%5%11%19%11%
2250
May1st to 15thDay
49%6%10%21%12%
2331
16th to endDay
44%7%15%20%10%
2434
June1st to 15thDay
34%9%15%24%14%1
2508
16th to endDay
26%7%17%29%17%2
2459
July1st to 15thDay
32%6%18%27%11%2
2201
16th to endDay
27%8%16%31%14%1
2311
August1st to 15thDay
31%8%16%26%16%1
2326
16th to endDay
32%6%12%25%15%6%
2390
September1st to 15thDay
36%5%12%24%17%5%
2096
16th to endDay
29%7%11%29%20%1
1980
October1st to 15thDay
35%410%23%20%5%
1800
16th to endDay
33%411%25%20%5%
1920
November1st to 15thDay
32%411%26%20%5%
1840
16th to endDay
35%310%28%20%1
1609
December1st to 15thDay
44%414%26%9%
1450
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
46%5%12%22%11%1
2112
April1st to 15thNight
35%410%26%20%2
1860
16th to endNight
43%5%10%24%15%1
1707
May1st to 15thNight
40%5%13%23%16%1
1620
16th to endNight
33%7%17%25%13%2
1685
June1st to 15thNight
25%7%17%30%16%2
1449
16th to endNight
19%5%15%31%23%3
1495
July1st to 15thNight
25%7%15%31%15%4
1530
16th to endNight
23%6%14%31%21%2
1594
August1st to 15thNight
23%7%14%33%17%3
1610
16th to endNight
28%5%9%24%24%6%
1812
September1st to 15thNight
32%5%11%23%19%7%
1862
16th to endNight
27%7%10%28%23%3
1980
October1st to 15thNight
33%38%23%23%7%
2148
16th to endNight
28%39%29%23%5%
2304
November1st to 15thNight
30%411%24%22%7%
2345
16th to endNight
34%29%30%20%2
2680
December1st to 15thNight
41%5%14%25%12%
2547
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
27%18%30%20%3
96
April1st to 15thDay
19%10%36%23%9%
207
16th to endDay
22%14%33%21%6%1
360
May1st to 15thDay
17%10%33%26%10%1
468
16th to endDay
18%8%32%24%12%4
517
June1st to 15thDay
9%426%33%21%5%
495
16th to endDay
6%428%33%22%3
495
July1st to 15thDay
12%213%39%26%6%
475
16th to endDay
5%11%35%39%6%
515
August1st to 15thDay
7%17%39%37%6%
493
16th to endDay
10%214%30%34%7%
430
September1st to 15thDay
10%111%38%28%9%
251
16th to endDay
7%223%39%17%8%
135
October1st to 15thDay
13%7%30%31%11%6%
135
16th to endDay
9%10%43%25%10%
144
November1st to 15thDay
18%10%20%29%14%5%
135
16th to endDay
28%11%31%20%8%
135
December1st to 15thDay
18%12%41%17%7%3
94
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%
576
April1st to 15thNight
14%10%38%29%6%
539
16th to endNight
20%7%35%27%7%
540
May1st to 15thNight
16%6%33%29%13%
540
16th to endNight
13%431%32%15%2
563
June1st to 15thNight
6%222%45%21%1
540
16th to endNight
4229%45%17%1
540
July1st to 15thNight
8%113%47%27%2
510
16th to endNight
5%110%43%37%1
564
August1st to 15thNight
5%8%44%38%2
539
16th to endNight
7%111%39%36%4
573
September1st to 15thNight
11%218%39%24%3
540
16th to endNight
8%219%38%24%5%
537
October1st to 15thNight
17%429%28%17%2
708
16th to endNight
12%8%36%30%11%
768
November1st to 15thNight
11%10%36%28%12%
825
16th to endNight
17%11%36%28%6%
975
December1st to 15thNight
19%10%36%26%5%
910
16th to endNight
20%9%34%30%5%
960
Page generated at 2017-12-03 10:16:39. Version ac04

Copyright 2017 A. Danko


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