Crystal Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Crystal Lake clear sky chart from 2005-11-05 to 2017-08-12.

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%
15875
17%
46472
10%
15834
43%
15834
23%
31137

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
20%
900
14%
2506
4%
895
29%
895
18%
1824
January16th to endNight
19%
960
12%
2657
4%
960
27%
960
16%
1985
February1st to 15thNight
21%
811
14%
2222
4%
811
28%
811
19%
1579
February16th to endNight
24%
631
18%
1893
8%
631
34%
631
18%
1323
March1st to 15thNight
27%
720
13%
2160
7%
720
32%
720
18%
1520
March16th to endNight
31%
615
15%
2010
10%
615
37%
615
18%
1397
April1st to 15thNight
28%
539
15%
1797
9%
539
38%
539
19%
1221
April16th to endNight
33%
540
19%
1736
11%
540
43%
540
22%
1152
May1st to 15thNight
35%
540
15%
1576
7%
540
42%
540
22%
1118
May16th to endNight
45%
561
18%
1498
9%
561
51%
561
31%
981
June1st to 15thNight
51%
540
16%
1440
10%
540
55%
540
34%
905
June16th to endNight
49%
540
16%
1440
9%
540
53%
540
30%
960
July1st to 15thNight
62%
510
17%
1360
11%
510
65%
510
39%
817
July16th to endNight
68%
564
21%
1417
15%
531
72%
531
42%
839
August1st to 15thNight
73%
527
22%
1520
20%
524
74%
524
42%
847
August16th to endNight
66%
525
20%
1750
21%
525
70%
525
34%
974
September1st to 15thNight
60%
495
30%
1650
28%
495
67%
495
35%
906
September16th to endNight
56%
654
25%
1812
18%
654
62%
654
35%
1103
October1st to 15thNight
46%
660
25%
1908
18%
660
53%
660
31%
1160
October16th to endNight
30%
704
18%
2237
9%
704
40%
704
21%
1451
November1st to 15thNight
33%
700
23%
2276
16%
700
43%
700
24%
1407
November16th to endNight
24%
779
16%
2399
8%
779
34%
779
18%
1634
December1st to 15thNight
19%
900
14%
2520
4%
900
27%
900
17%
1879
December16th to endNight
14%
960
11%
2688
3%
960
22%
960
12%
2155

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%8%36%5%35%45%7%36%
47507
Night
14%7%35%5%2445%6%40%
46640
Cloud CoverDay
13%8%36%5%35%45%7%36%
47516
Night
14%7%35%5%2445%6%40%
46645
TransparencyDay
46%6%12%21%11%1
47193
Night
43%5%12%22%13%1
46472
SeeingDay
15%8%29%26%14%5%
5848
Night
17%9%30%28%12%1
15880

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
13%13%5%6%5%35%5%5%7%27%
1432
16th to endDay
12%13%7%10%6%345%46%25%
1566
February1st to 15thDay
13%14%6%6%5%36%445%29%
1639
16th to endDay
14%10%48%6%25%35%5%32%
1580
March1st to 15thDay
15%11%47%5%2435%7%31%
1790
16th to endDay
18%8%46%5%35%446%31%
2223
April1st to 15thDay
18%10%5%6%6%34445%31%
2151
16th to endDay
18%8%36%5%2435%6%35%
2223
May1st to 15thDay
17%9%48%5%25%5%5%6%29%
2373
16th to endDay
12%6%35%5%45%5%5%7%37%
2617
June1st to 15thDay
10%6%246%3445%8%41%
2520
16th to endDay
9%5%36%5%25%5%6%9%39%
2520
July1st to 15thDay
8%415%5%35%6%7%9%42%
2520
16th to endDay
7%5%26%6%36%5%6%9%41%
2655
August1st to 15thDay
7%426%6%26%5%7%8%40%
2340
16th to endDay
10%5%26%435%5%5%8%41%
2100
September1st to 15thDay
13%31442345%7%49%
1972
16th to endDay
10%5%35%5%3445%8%43%
1815
October1st to 15thDay
15%6%24433445%43%
1719
16th to endDay
18%8%35%5%34445%37%
1634
November1st to 15thDay
13%7%36%4235%5%6%39%
1582
16th to endDay
17%9%46%433346%35%
1560
December1st to 15thDay
17%12%5%8%6%34246%28%
1440
16th to endDay
21%13%6%8%5%24435%22%
1536
January1st to 15thNight
16%10%47%5%24335%35%
2506
16th to endNight
12%11%6%9%6%3445%7%29%
2657
February1st to 15thNight
13%13%5%6%424345%35%
2220
16th to endNight
16%10%46%5%3425%6%34%
1893
March1st to 15thNight
16%8%46%5%3435%6%36%
2147
16th to endNight
16%8%36%5%3445%7%34%
2010
April1st to 15thNight
18%7%35%5%25%5%46%35%
1797
16th to endNight
19%8%25%322445%40%
1736
May1st to 15thNight
17%6%35%5%35%5%5%7%34%
1576
16th to endNight
11%436%42446%9%42%
1496
June1st to 15thNight
11%42442446%6%48%
1440
16th to endNight
7%426%5%35%6%7%9%40%
1440
July1st to 15thNight
5%223425%5%7%9%51%
1440
16th to endNight
5%323325%47%11%50%
1513
August1st to 15thNight
42135%2447%9%53%
1529
16th to endNight
9%41342435%8%52%
1750
September1st to 15thNight
10%414333335%57%
1650
16th to endNight
9%4145%24347%51%
1812
October1st to 15thNight
12%5%1442335%7%49%
1908
16th to endNight
19%7%24323345%41%
2237
November1st to 15thNight
12%8%25%423335%46%
2276
16th to endNight
15%9%46%5%23337%36%
2399
December1st to 15thNight
20%8%47%5%245%45%30%
2520
16th to endNight
22%14%47%6%24436%22%
2688

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%13%6%6%6%35%5%5%7%27%
1432
16th to endDay
12%13%7%10%7%34445%25%
1566
February1st to 15thDay
13%13%6%6%5%46%445%29%
1639
16th to endDay
14%10%48%6%34446%32%
1580
March1st to 15thDay
15%11%47%6%3445%7%31%
1800
16th to endDay
18%9%46%6%35%446%31%
2222
April1st to 15thDay
17%11%5%6%5%34445%31%
2151
16th to endDay
18%9%25%5%3335%6%35%
2223
May1st to 15thDay
17%9%38%5%26%45%7%29%
2373
16th to endDay
12%7%35%5%35%5%5%8%37%
2617
June1st to 15thDay
10%6%25%5%35%5%6%7%41%
2520
16th to endDay
9%5%36%6%35%5%7%9%39%
2520
July1st to 15thDay
7%425%5%35%6%7%9%42%
2520
16th to endDay
7%5%25%5%36%5%6%9%42%
2655
August1st to 15thDay
7%436%5%36%5%6%9%40%
2340
16th to endDay
10%425%5%36%45%8%41%
2100
September1st to 15thDay
13%31432445%7%49%
1972
16th to endDay
9%5%245%345%6%8%43%
1815
October1st to 15thDay
14%6%34423445%44%
1719
16th to endDay
18%7%36%5%34445%37%
1634
November1st to 15thDay
14%7%36%42446%5%39%
1582
16th to endDay
17%9%47%5%33346%35%
1560
December1st to 15thDay
16%12%48%6%34347%28%
1440
16th to endDay
20%13%7%8%5%24445%22%
1536
January1st to 15thNight
16%11%47%5%24335%35%
2506
16th to endNight
13%11%6%9%6%25%45%7%29%
2657
February1st to 15thNight
13%13%46%434346%36%
2213
16th to endNight
16%10%46%5%2425%6%34%
1893
March1st to 15thNight
16%8%46%5%34445%36%
2160
16th to endNight
16%8%36%5%3445%7%34%
2010
April1st to 15thNight
18%7%35%5%25%5%36%35%
1797
16th to endNight
19%7%25%314345%40%
1736
May1st to 15thNight
17%6%35%5%445%5%7%34%
1575
16th to endNight
11%5%36%42346%9%42%
1496
June1st to 15thNight
10%4245%2446%6%48%
1440
16th to endNight
7%425%6%25%6%7%9%40%
1440
July1st to 15thNight
5%3143345%6%9%51%
1440
16th to endNight
5%22233447%11%50%
1513
August1st to 15thNight
421342447%9%53%
1529
16th to endNight
9%32432445%7%52%
1750
September1st to 15thNight
10%414323245%57%
1650
16th to endNight
9%4245%24347%51%
1812
October1st to 15thNight
12%424423347%49%
1908
16th to endNight
19%7%24423345%41%
2237
November1st to 15thNight
12%8%25%423345%46%
2276
16th to endNight
16%9%46%5%23346%36%
2399
December1st to 15thNight
19%9%47%6%24445%30%
2520
16th to endNight
23%13%5%8%5%34435%22%
2688

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
53%7%15%14%9%
1433
16th to endDay
59%5%11%15%7%
1566
February1st to 15thDay
56%6%11%17%8%1
1641
16th to endDay
52%6%11%19%8%1
1580
March1st to 15thDay
52%6%13%18%7%
1800
16th to endDay
54%5%14%19%5%
2223
April1st to 15thDay
55%5%9%20%9%
2151
16th to endDay
48%6%12%18%12%2
2223
May1st to 15thDay
53%7%11%21%6%
2373
16th to endDay
44%7%12%20%13%1
2621
June1st to 15thDay
38%7%12%24%16%1
2520
16th to endDay
40%7%14%20%15%1
2520
July1st to 15thDay
34%8%13%26%14%2
2371
16th to endDay
35%7%17%21%14%3
2488
August1st to 15thDay
37%8%14%26%12%1
2325
16th to endDay
38%6%12%22%17%2
2100
September1st to 15thDay
34%6%11%25%18%2
1972
16th to endDay
36%5%12%27%15%
1815
October1st to 15thDay
40%6%11%25%14%1
1719
16th to endDay
47%5%13%21%9%1
1634
November1st to 15thDay
43%5%11%23%13%2
1582
16th to endDay
50%5%13%23%6%
1560
December1st to 15thDay
57%5%13%17%6%
1440
16th to endDay
63%5%10%11%7%
1536
January1st to 15thNight
51%5%10%19%11%
2506
16th to endNight
54%5%13%15%9%
2657
February1st to 15thNight
50%411%20%11%
2222
16th to endNight
50%412%22%8%2
1893
March1st to 15thNight
50%6%12%17%11%2
2160
16th to endNight
48%6%13%20%8%1
2010
April1st to 15thNight
48%5%10%20%13%1
1797
16th to endNight
44%5%10%22%12%4
1736
May1st to 15thNight
46%7%11%22%10%
1576
16th to endNight
37%7%12%22%17%2
1498
June1st to 15thNight
33%7%11%25%18%2
1440
16th to endNight
37%8%13%20%18%1
1440
July1st to 15thNight
27%8%13%28%18%2
1360
16th to endNight
26%8%16%26%17%4
1417
August1st to 15thNight
24%8%16%29%19%1
1520
16th to endNight
30%6%12%28%17%4
1750
September1st to 15thNight
29%48%27%26%2
1650
16th to endNight
32%5%10%32%16%1
1812
October1st to 15thNight
35%411%26%20%1
1908
16th to endNight
44%412%24%12%1
2237
November1st to 15thNight
40%48%24%17%3
2276
16th to endNight
48%413%22%10%
2399
December1st to 15thNight
54%6%10%20%8%
2520
16th to endNight
64%410%13%5%1
2688

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%17%40%23%1
90
16th to endDay
21%11%32%26%7%1
96
February1st to 15thDay
21%17%47%12%1
90
16th to endDay
24%11%32%20%8%2
81
March1st to 15thDay
36%12%32%16%2
90
16th to endDay
27%8%29%20%11%2
237
April1st to 15thDay
25%11%29%24%8%
270
16th to endDay
22%12%28%22%8%4
270
May1st to 15thDay
20%13%30%21%9%3
330
16th to endDay
17%10%31%24%11%3
517
June1st to 15thDay
10%7%33%29%14%4
495
16th to endDay
12%8%34%27%12%5%
495
July1st to 15thDay
8%429%30%18%9%
475
16th to endDay
8%327%34%16%8%
515
August1st to 15thDay
8%221%32%21%14%
399
16th to endDay
11%5%13%32%25%12%
268
September1st to 15thDay
11%420%30%23%9%
255
16th to endDay
10%5%22%25%26%9%
254
October1st to 15thDay
13%9%26%28%16%5%
159
16th to endDay
27%11%33%21%6%
96
November1st to 15thDay
414%30%33%13%4
90
16th to endDay
25%14%38%14%6%
90
December1st to 15thDay
15%20%40%20%4
90
16th to endDay
28%27%40%31
96
January1st to 15thNight
20%15%37%20%5%
900
16th to endNight
18%14%38%26%2
960
February1st to 15thNight
22%11%37%23%4
814
16th to endNight
22%12%32%26%5%
631
March1st to 15thNight
20%13%33%24%8%
720
16th to endNight
20%7%34%27%9%
615
April1st to 15thNight
23%10%34%25%6%
539
16th to endNight
23%8%31%27%8%
540
May1st to 15thNight
19%6%32%30%10%
540
16th to endNight
12%7%29%33%17%
563
June1st to 15thNight
12%227%42%14%
540
16th to endNight
9%332%36%16%1
540
July1st to 15thNight
7%122%41%25%2
510
16th to endNight
4120%45%26%2
564
August1st to 15thNight
413%50%27%3
527
16th to endNight
9%216%36%30%4
525
September1st to 15thNight
11%219%32%28%4
495
16th to endNight
11%6%19%32%27%2
654
October1st to 15thNight
16%7%25%29%18%1
660
16th to endNight
23%11%32%23%8%
704
November1st to 15thNight
17%10%35%25%9%1
700
16th to endNight
20%14%34%23%7%
779
December1st to 15thNight
24%13%37%20%4
900
16th to endNight
29%12%34%20%2
960
Page generated at 2017-08-13 13:16:30. Version ac04

Copyright 2017 A. Danko


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