Spruce Knob Mountain Center
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Spruce Knob Mountain Center clear sky chart from 2005-11-06 to 2024-01-16.

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
30%
23742
16%
74818
9%
23688
38%
23688
16%
52614

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 10thNight
10%
757
16%
2459
4%
757
23%
757
6%
1849
January11th to 20thNight
11%
741
14%
2406
3%
741
24%
741
8%
1877
January21st to endNight
9%
792
15%
2574
3%
792
22%
792
7%
1932
February1st to 10thNight
12%
720
14%
2340
5%
720
25%
720
9%
1695
February11th to 20thNight
7%
702
11%
2275
2%
700
17%
700
6%
1722
February21st to endNight
7%
592
18%
1718
3%
592
23%
592
9%
1300
March1st to 10thNight
15%
720
19%
1980
7%
720
27%
720
14%
1399
March11th to 20thNight
16%
720
15%
1980
5%
720
25%
720
12%
1467
March21st to endNight
17%
792
13%
2178
5%
792
24%
792
13%
1629
April1st to 10thNight
17%
720
15%
1879
4%
720
26%
720
17%
1355
April11th to 20thNight
26%
711
16%
1775
6%
711
31%
711
21%
1265
April21st to endNight
26%
608
18%
1688
6%
608
33%
608
18%
1208
May1st to 10thNight
32%
540
12%
1620
5%
540
39%
540
16%
1166
May11th to 20thNight
32%
531
12%
1593
7%
531
36%
531
17%
1158
May21st to endNight
44%
538
11%
1701
7%
538
49%
538
23%
1144
June1st to 10thNight
47%
360
16%
1440
17%
360
53%
360
20%
898
June11th to 20thNight
48%
360
13%
1440
12%
360
53%
360
18%
927
June21st to endNight
47%
378
18%
1458
17%
378
57%
378
24%
867
July1st to 10thNight
53%
525
12%
1575
10%
525
55%
525
24%
1057
July11th to 20thNight
60%
522
15%
1566
12%
522
62%
522
30%
973
July21st to endNight
57%
591
15%
1672
11%
558
60%
558
27%
1077
August1st to 10thNight
59%
537
15%
1600
12%
534
61%
534
25%
1074
August11th to 20thNight
57%
534
17%
1598
12%
534
59%
534
25%
1074
August21st to endNight
53%
747
17%
1935
10%
747
56%
747
29%
1297
September1st to 10thNight
50%
720
20%
1800
10%
720
55%
720
29%
1219
September11th to 20thNight
54%
720
24%
1952
18%
720
57%
720
30%
1266
September21st to endNight
36%
720
17%
1994
12%
720
42%
720
20%
1420
October1st to 10thNight
44%
720
18%
2160
16%
720
49%
720
23%
1431
October11th to 20thNight
33%
720
21%
2160
13%
720
45%
720
21%
1420
October21st to endNight
26%
792
22%
2376
12%
792
39%
792
17%
1643
November1st to 10thNight
33%
740
23%
2221
15%
740
44%
740
21%
1455
November11th to 20thNight
24%
760
20%
2507
11%
760
36%
760
14%
1744
November21st to endNight
20%
760
17%
2660
8%
760
32%
760
13%
1833
December1st to 10thNight
16%
760
12%
2660
6%
760
24%
760
7%
2037
December11th to 20thNight
17%
760
15%
3215
7%
759
30%
759
7%
2306
December21st to endNight
15%
832
11%
4663
6%
817
28%
817
5%
3430

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%8%48%7%46%5%6%7%33%
74633
Night
10%7%47%7%46%5%6%8%35%
75152
TransparencyDay
48%9%10%18%12%2
74354
Night
45%11%11%19%12%2
74950
SeeingDay
23%20%27%18%10%4
13799
Night
20%21%24%23%11%1
23752

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 10thDay
8%9%5%11%7%5%7%6%5%7%30%
1706
11th to 20thDay
10%10%6%12%8%46%5%5%7%28%
1665
21st to endDay
10%8%7%11%7%445%5%7%32%
1782
February1st to 10thDay
9%11%49%8%46%5%6%8%30%
1620
11th to 20thDay
11%10%410%7%45%5%6%9%30%
1573
21st to endDay
12%12%38%7%45%5%5%6%33%
1535
March1st to 10thDay
10%7%38%5%46%5%6%7%38%
1980
11th to 20thDay
12%10%49%6%35%5%6%6%32%
1980
21st to endDay
14%11%48%8%46%5%5%5%31%
2178
April1st to 10thDay
10%8%5%9%7%45%46%8%35%
2080
11th to 20thDay
12%9%5%6%5%35%45%7%40%
2134
21st to endDay
18%7%46%6%36%5%6%7%33%
2286
May1st to 10thDay
16%10%48%8%45%5%5%5%31%
2340
11th to 20thDay
20%8%37%6%5%6%5%5%7%28%
2301
21st to endDay
12%8%49%7%5%7%5%6%8%30%
2571
June1st to 10thDay
13%7%36%6%46%5%6%7%36%
2520
11th to 20thDay
11%7%37%8%46%7%7%8%32%
2520
21st to endDay
10%5%46%7%5%7%7%8%7%34%
2496
July1st to 10thDay
10%6%48%8%5%7%7%7%9%30%
2340
11th to 20thDay
8%5%37%8%5%7%7%7%10%32%
2340
21st to endDay
11%8%49%8%47%7%7%8%28%
2547
August1st to 10thDay
11%7%37%9%5%7%7%8%10%26%
2327
11th to 20thDay
12%7%39%9%5%7%7%6%9%27%
2303
21st to endDay
11%6%37%7%6%8%6%7%9%30%
2401
September1st to 10thDay
14%6%36%7%5%5%45%7%37%
2160
11th to 20thDay
11%7%36%7%35%5%6%8%39%
2004
21st to endDay
19%9%36%5%35%45%6%35%
1964
October1st to 10thDay
14%7%36%6%4445%6%40%
1800
11th to 20thDay
15%10%37%5%34445%41%
1800
21st to endDay
13%9%36%5%345%6%7%40%
1980
November1st to 10thDay
9%7%35%5%345%47%48%
1857
11th to 20thDay
13%7%36%6%45%5%6%8%39%
1664
21st to endDay
12%7%47%6%45%5%47%40%
1520
December1st to 10thDay
11%11%6%9%7%46%6%5%8%28%
1520
11th to 20thDay
12%8%49%6%36%46%7%35%
1910
21st to endDay
13%9%5%8%8%5%6%5%7%7%26%
2929
January1st to 10thNight
8%8%5%11%9%48%6%7%8%28%
2459
11th to 20thNight
10%9%5%9%9%5%7%6%6%9%26%
2406
21st to endNight
9%8%5%8%8%5%6%5%5%8%32%
2574
February1st to 10thNight
8%7%48%7%46%7%6%11%31%
2340
11th to 20thNight
11%9%48%9%5%8%6%6%7%27%
2273
21st to endNight
10%10%49%8%45%46%7%31%
1718
March1st to 10thNight
9%7%35%6%6%5%7%6%7%39%
1980
11th to 20thNight
13%8%5%8%7%445%6%7%34%
1980
21st to endNight
12%8%47%7%46%5%6%7%33%
2178
April1st to 10thNight
10%7%5%7%6%46%5%6%7%36%
1879
11th to 20thNight
10%7%45%6%45%6%6%9%38%
1775
21st to endNight
13%7%46%6%45%5%5%7%38%
1688
May1st to 10thNight
13%9%38%6%45%6%5%7%34%
1620
11th to 20thNight
16%9%36%6%35%5%6%7%33%
1592
21st to endNight
11%6%26%6%35%6%7%11%38%
1700
June1st to 10thNight
10%5%26%5%36%5%7%10%41%
1440
11th to 20thNight
9%5%36%7%45%6%7%9%39%
1440
21st to endNight
8%4245%46%6%7%11%43%
1458
July1st to 10thNight
8%6%36%6%46%6%6%9%41%
1620
11th to 20thNight
7%3245%45%5%8%11%46%
1620
21st to endNight
7%436%7%45%5%9%11%39%
1771
August1st to 10thNight
8%5%36%7%46%6%8%11%37%
1611
11th to 20thNight
10%5%37%6%46%5%8%8%38%
1598
21st to endNight
8%6%37%6%35%5%7%10%39%
1935
September1st to 10thNight
12%6%25%5%36%6%5%6%44%
1800
11th to 20thNight
9%7%36%6%445%5%7%45%
1952
21st to endNight
15%10%25%6%45%5%5%7%36%
1994
October1st to 10thNight
14%7%36%5%35%5%5%7%41%
2160
11th to 20thNight
11%8%37%5%345%6%8%41%
2160
21st to endNight
12%8%36%6%35%5%5%6%40%
2376
November1st to 10thNight
7%8%46%5%46%5%5%6%44%
2221
11th to 20thNight
11%7%48%436%5%7%7%37%
2507
21st to endNight
11%7%37%6%47%5%6%8%36%
2660
December1st to 10thNight
11%9%6%11%7%6%5%6%7%7%26%
2660
11th to 20thNight
12%8%410%6%35%5%5%8%33%
3285
21st to endNight
12%8%6%8%8%5%6%6%7%8%25%
4722

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 10thDay
53%10%6%16%13%2
1707
11th to 20thDay
56%10%7%14%11%2
1665
21st to endDay
53%9%7%14%13%4
1782
February1st to 10thDay
53%10%8%18%10%2
1620
11th to 20thDay
51%12%7%16%13%2
1582
21st to endDay
51%11%7%16%12%4
1535
March1st to 10thDay
43%9%9%21%15%2
1980
11th to 20thDay
52%8%7%18%12%3
1980
21st to endDay
55%8%7%17%11%3
2178
April1st to 10thDay
47%8%11%16%14%3
2080
11th to 20thDay
44%8%8%20%17%4
2134
21st to endDay
50%8%9%20%11%2
2286
May1st to 10thDay
54%8%9%17%10%1
2340
11th to 20thDay
55%8%12%16%7%2
2305
21st to endDay
50%10%14%18%7%1
2571
June1st to 10thDay
45%9%12%21%12%
2520
11th to 20thDay
46%12%14%18%10%1
2520
21st to endDay
44%11%13%21%10%1
2496
July1st to 10thDay
47%11%11%18%11%1
2275
11th to 20thDay
42%11%13%21%12%1
2271
21st to endDay
50%10%9%18%12%1
2405
August1st to 10thDay
50%11%14%18%8%
2314
11th to 20thDay
52%10%12%18%8%
2303
21st to endDay
47%10%12%19%10%2
2401
September1st to 10thDay
46%8%10%16%16%3
2160
11th to 20thDay
43%7%8%22%16%4
2004
21st to endDay
49%5%9%19%16%2
1964
October1st to 10thDay
43%6%10%21%15%5%
1800
11th to 20thDay
46%6%8%21%17%2
1800
21st to endDay
43%9%7%21%16%4
1980
November1st to 10thDay
37%8%7%22%19%6%
1857
11th to 20thDay
42%9%8%16%20%5%
1664
21st to endDay
45%9%8%19%16%2
1520
December1st to 10thDay
56%10%7%14%10%2
1520
11th to 20thDay
45%14%6%18%14%3
1906
21st to endDay
53%11%9%15%11%1
2929
January1st to 10thNight
51%14%6%13%13%4
2459
11th to 20thNight
53%15%7%13%10%2
2406
21st to endNight
52%12%7%15%11%3
2574
February1st to 10thNight
49%11%10%18%10%2
2340
11th to 20thNight
54%11%7%15%9%3
2275
21st to endNight
54%9%7%16%10%4
1718
March1st to 10thNight
43%11%7%22%13%4
1980
11th to 20thNight
49%10%10%19%11%2
1980
21st to endNight
50%10%9%15%12%4
2178
April1st to 10thNight
46%9%10%19%14%2
1879
11th to 20thNight
41%10%12%19%14%3
1775
21st to endNight
45%9%11%22%11%2
1688
May1st to 10thNight
48%10%13%18%9%2
1620
11th to 20thNight
49%9%13%19%9%1
1593
21st to endNight
39%12%22%20%7%1
1701
June1st to 10thNight
35%13%13%27%10%
1440
11th to 20thNight
39%13%15%22%10%1
1440
21st to endNight
33%12%17%26%12%1
1458
July1st to 10thNight
37%13%17%19%12%2
1575
11th to 20thNight
30%13%19%26%12%2
1566
21st to endNight
34%12%19%22%12%
1672
August1st to 10thNight
37%12%19%21%10%
1600
11th to 20thNight
38%11%18%22%10%1
1598
21st to endNight
38%10%17%24%11%2
1935
September1st to 10thNight
38%9%15%19%17%3
1800
11th to 20thNight
37%7%10%26%16%3
1952
21st to endNight
46%9%11%19%15%
1994
October1st to 10thNight
41%8%11%24%13%3
2160
11th to 20thNight
40%9%10%23%16%3
2160
21st to endNight
43%10%7%19%17%3
2376
November1st to 10thNight
40%8%9%17%18%8%
2221
11th to 20thNight
43%13%5%16%19%4
2507
21st to endNight
46%11%9%17%14%3
2660
December1st to 10thNight
56%11%7%15%9%2
2660
11th to 20thNight
50%11%7%12%17%2
3288
21st to endNight
51%15%8%15%10%1
4722

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 10thDay
35%34%19%9%3
270
11th to 20thDay
37%33%24%6%1
255
21st to endDay
40%28%26%6%1
264
February1st to 10thDay
40%36%19%41
240
11th to 20thDay
48%30%20%3
240
21st to endDay
40%30%22%7%
274
March1st to 10thDay
33%28%27%10%3
420
11th to 20thDay
32%30%20%12%4
420
21st to endDay
28%27%28%11%5%
462
April1st to 10thDay
26%30%28%11%5%1
420
11th to 20thDay
27%21%29%13%8%2
412
21st to endDay
30%25%27%12%5%2
420
May1st to 10thDay
28%25%25%12%7%3
423
11th to 20thDay
23%21%29%19%5%4
447
21st to endDay
18%13%27%22%14%6%
485
June1st to 10thDay
17%17%30%19%13%4
450
11th to 20thDay
18%14%31%20%13%5%
450
21st to endDay
11%18%34%23%10%3
450
July1st to 10thDay
12%13%27%24%16%9%
445
11th to 20thDay
6%9%33%31%12%9%
444
21st to endDay
14%10%28%24%17%7%
488
August1st to 10thDay
15%10%23%26%15%10%
446
11th to 20thDay
13%9%26%25%17%10%
439
21st to endDay
11%9%27%26%18%8%
495
September1st to 10thDay
17%10%23%24%18%8%
450
11th to 20thDay
14%7%23%28%20%8%
450
21st to endDay
24%15%26%19%13%3
450
October1st to 10thDay
20%13%25%24%16%3
450
11th to 20thDay
22%20%28%19%10%1
450
21st to endDay
23%24%29%15%7%1
495
November1st to 10thDay
18%25%26%19%9%2
455
11th to 20thDay
31%23%26%14%5%1
258
21st to endDay
31%19%37%10%3
180
December1st to 10thDay
32%33%23%9%21
180
11th to 20thDay
37%25%23%12%21
180
21st to endDay
31%29%24%12%3
242
January1st to 10thNight
28%36%22%11%3
760
11th to 20thNight
27%32%27%13%1
741
21st to endNight
25%37%25%12%1
792
February1st to 10thNight
25%35%25%13%2
720
11th to 20thNight
31%38%23%9%
703
21st to endNight
30%35%26%9%1
592
March1st to 10thNight
25%31%26%16%2
720
11th to 20thNight
29%27%24%14%41
720
21st to endNight
24%28%27%16%5%1
792
April1st to 10thNight
21%30%30%16%4
720
11th to 20thNight
20%23%26%21%9%
711
21st to endNight
21%19%30%25%6%
608
May1st to 10thNight
20%19%24%26%11%1
540
11th to 20thNight
18%16%27%28%9%2
531
21st to endNight
14%9%28%29%18%3
540
June1st to 10thNight
11%9%28%31%20%1
360
11th to 20thNight
13%7%24%39%17%1
360
21st to endNight
7%8%30%38%16%1
378
July1st to 10thNight
11%6%21%33%24%6%
525
11th to 20thNight
7%422%35%26%5%
522
21st to endNight
10%5%20%32%30%2
591
August1st to 10thNight
9%5%16%41%27%2
537
11th to 20thNight
11%7%15%37%26%4
534
21st to endNight
11%6%21%36%23%4
747
September1st to 10thNight
15%5%20%31%23%6%
720
11th to 20thNight
12%9%18%32%26%4
720
21st to endNight
21%13%23%23%18%2
720
October1st to 10thNight
18%13%18%28%19%3
720
11th to 20thNight
19%20%24%25%11%1
720
21st to endNight
22%22%26%21%8%1
792
November1st to 10thNight
16%22%25%26%9%2
740
11th to 20thNight
25%23%25%19%8%1
760
21st to endNight
23%24%29%18%5%1
760
December1st to 10thNight
25%33%22%16%4
760
11th to 20thNight
22%32%25%17%4
760
21st to endNight
24%28%28%18%2
836
Page generated at 2024-01-13 01:38:11. Version ac07

Copyright 2024 Attilla Danko


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