Crystal Mountain
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Crystal Mountain clear sky chart from 2005-11-06 to 2024-01-22.

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
46%
24167
24%
74872
17%
24106
54%
24106
30%
44059

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
29%
950
26%
2458
9%
946
40%
946
28%
1554
January11th to 20thNight
25%
950
26%
2470
8%
950
36%
950
25%
1609
January21st to endNight
27%
1000
29%
2600
9%
1000
40%
1000
31%
1605
February1st to 10thNight
25%
900
19%
2340
6%
900
32%
900
23%
1595
February11th to 20thNight
20%
788
19%
2183
6%
784
29%
784
23%
1431
February21st to endNight
21%
522
25%
1706
8%
522
36%
522
20%
1073
March1st to 10thNight
34%
540
24%
1980
15%
540
44%
540
23%
1161
March11th to 20thNight
30%
540
21%
1980
14%
540
41%
540
19%
1251
March21st to endNight
32%
594
19%
2178
12%
594
43%
594
21%
1356
April1st to 10thNight
31%
540
26%
1828
14%
540
47%
540
26%
1036
April11th to 20thNight
34%
533
26%
1775
17%
533
49%
533
27%
1016
April21st to endNight
33%
540
23%
1800
14%
540
49%
540
29%
1063
May1st to 10thNight
48%
540
20%
1782
17%
540
56%
540
29%
1056
May11th to 20thNight
48%
531
20%
1594
17%
531
53%
531
28%
994
May21st to endNight
54%
584
20%
1746
16%
582
61%
582
29%
1079
June1st to 10thNight
71%
540
21%
1620
20%
540
75%
540
40%
899
June11th to 20thNight
72%
540
24%
1620
25%
540
75%
540
47%
838
June21st to endNight
75%
540
27%
1620
26%
540
79%
540
48%
834
July1st to 10thNight
74%
525
18%
1575
20%
525
76%
525
36%
913
July11th to 20thNight
78%
522
22%
1566
24%
522
80%
522
44%
819
July21st to endNight
81%
591
25%
1673
29%
558
82%
558
40%
925
August1st to 10thNight
77%
537
19%
1601
23%
534
77%
534
40%
881
August11th to 20thNight
73%
534
26%
1733
31%
534
76%
534
35%
962
August21st to endNight
77%
594
23%
1980
26%
594
78%
594
36%
1076
September1st to 10thNight
73%
540
28%
1800
31%
540
75%
540
38%
964
September11th to 20thNight
68%
540
29%
1835
31%
540
70%
540
33%
1025
September21st to endNight
68%
605
31%
2045
28%
605
73%
605
41%
1034
October1st to 10thNight
66%
720
29%
2160
23%
720
69%
720
43%
1146
October11th to 20thNight
50%
720
33%
2160
20%
720
60%
720
38%
1192
October21st to endNight
41%
792
30%
2376
19%
792
51%
792
31%
1422
November1st to 10thNight
50%
740
32%
2220
22%
740
59%
740
37%
1216
November11th to 20thNight
41%
760
31%
2280
18%
760
54%
760
35%
1284
November21st to endNight
36%
836
27%
2531
16%
836
46%
836
28%
1524
December1st to 10thNight
32%
950
23%
2660
9%
950
43%
950
27%
1708
December11th to 20thNight
32%
948
25%
3041
11%
948
42%
948
23%
1902
December21st to endNight
28%
1041
16%
4356
9%
1026
40%
1026
17%
2616

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%6%35%5%35%5%5%7%44%
74518
Night
12%5%2443445%7%51%
75423
TransparencyDay
38%7%11%21%18%5%
74241
Night
33%6%11%22%22%6%
75220
SeeingDay
16%11%24%26%19%5%
14225
Night
15%10%24%31%18%2
24173

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
15%10%34423346%47%
1707
11th to 20thDay
15%7%36%5%34445%45%
1710
21st to endDay
15%7%34423336%50%
1791
February1st to 10thDay
20%9%245%3333444%
1620
11th to 20thDay
16%8%45%6%24445%41%
1663
21st to endDay
21%9%37%434345%37%
1565
March1st to 10thDay
17%7%245%34335%46%
1980
11th to 20thDay
20%7%36%5%3344442%
1980
21st to endDay
18%7%26%5%3445%7%39%
2178
April1st to 10thDay
13%6%26%6%345%47%44%
2132
11th to 20thDay
16%6%25%5%33446%45%
2134
21st to endDay
15%6%35%6%35%45%6%41%
2160
May1st to 10thDay
17%5%35%5%3445%7%40%
2174
11th to 20thDay
13%5%25%6%46%5%6%6%42%
2302
21st to endDay
9%5%37%7%47%6%7%8%37%
2531
June1st to 10thDay
9%5%36%6%46%5%7%10%41%
2340
11th to 20thDay
5%435%6%46%7%7%10%43%
2340
21st to endDay
5%325%6%46%6%7%9%48%
2340
July1st to 10thDay
6%5%37%7%46%8%8%10%34%
2340
11th to 20thDay
5%425%6%5%8%6%6%9%44%
2340
21st to endDay
8%425%6%46%7%8%11%40%
2546
August1st to 10thDay
7%426%7%5%7%7%8%9%39%
2328
11th to 20thDay
12%426%5%35%6%7%9%41%
2168
21st to endDay
8%425%6%47%6%7%9%43%
2376
September1st to 10thDay
12%5%25%5%35%5%5%6%46%
2160
11th to 20thDay
15%4245%45%5%5%6%45%
2121
21st to endDay
10%424434446%54%
1895
October1st to 10thDay
7%425%5%3345%6%56%
1800
11th to 20thDay
15%5%24322336%56%
1800
21st to endDay
17%5%24423445%51%
1980
November1st to 10thDay
11%5%24323445%58%
1858
11th to 20thDay
10%42442345%7%54%
1900
21st to endDay
16%8%35%32333448%
1640
December1st to 10thDay
17%6%34433446%46%
1520
11th to 20thDay
13%8%37%6%34445%43%
1964
21st to endDay
13%8%37%6%45%5%5%5%39%
3135
January1st to 10thNight
15%6%25%433345%50%
2458
11th to 20thNight
16%7%34323345%49%
2470
21st to endNight
16%5%23323335%53%
2600
February1st to 10thNight
19%7%45%433345%42%
2340
11th to 20thNight
16%7%35%5%33345%46%
2182
21st to endNight
18%8%34423345%45%
1706
March1st to 10thNight
17%6%35%433446%46%
1980
11th to 20thNight
19%8%25%32334444%
1980
21st to endNight
14%7%35%435%447%43%
2178
April1st to 10thNight
12%425%42445%7%51%
1828
11th to 20thNight
11%5%25%43345%6%51%
1775
21st to endNight
13%6%25%43445%6%49%
1800
May1st to 10thNight
13%424435%5%5%7%49%
1782
11th to 20thNight
12%6%245%4445%8%45%
1593
21st to endNight
8%5%36%43446%10%45%
1745
June1st to 10thNight
6%31342446%11%55%
1620
11th to 20thNight
431432445%9%60%
1620
21st to endNight
5%21332445%9%62%
1620
July1st to 10thNight
43345%35%5%9%11%47%
1620
11th to 20thNight
32134346%8%11%55%
1620
21st to endNight
4213435%6%7%11%54%
1772
August1st to 10thNight
5%3245%35%5%7%11%50%
1611
11th to 20thNight
7%414425%5%6%9%52%
1733
21st to endNight
6%415%4345%7%9%52%
1980
September1st to 10thNight
8%42432345%7%57%
1800
11th to 20thNight
10%5%2442445%7%53%
1835
21st to endNight
9%32232245%6%60%
2045
October1st to 10thNight
7%323424347%61%
2160
11th to 20thNight
12%324323335%60%
2160
21st to endNight
18%5%2442322455%
2376
November1st to 10thNight
10%5%23323346%59%
2220
11th to 20thNight
11%42342445%6%56%
2280
21st to endNight
13%5%24434345%51%
2531
December1st to 10thNight
17%6%25%424445%47%
2660
11th to 20thNight
14%6%25%5%34445%49%
3211
21st to endNight
14%7%35%5%34446%45%
4532

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
41%5%7%22%19%6%
1708
11th to 20thDay
43%5%7%21%20%3
1710
21st to endDay
39%26%25%22%6%
1791
February1st to 10thDay
46%5%8%20%16%4
1620
11th to 20thDay
46%47%19%18%5%
1672
21st to endDay
52%46%14%16%9%
1565
March1st to 10thDay
43%48%16%19%10%
1980
11th to 20thDay
47%5%8%19%17%4
1980
21st to endDay
45%6%10%21%15%2
2178
April1st to 10thDay
40%6%9%21%20%4
2132
11th to 20thDay
41%5%9%21%17%7%
2134
21st to endDay
43%7%9%19%19%3
2160
May1st to 10thDay
45%6%11%17%18%3
2174
11th to 20thDay
41%9%13%23%13%1
2306
21st to endDay
42%9%15%21%13%1
2531
June1st to 10thDay
36%10%14%23%15%2
2340
11th to 20thDay
33%9%15%24%17%1
2340
21st to endDay
29%10%13%25%20%3
2340
July1st to 10thDay
37%12%17%21%11%1
2276
11th to 20thDay
32%10%15%25%15%3
2271
21st to endDay
33%12%18%25%12%1
2405
August1st to 10thDay
36%10%17%26%10%1
2314
11th to 20thDay
37%10%13%22%17%2
2168
21st to endDay
36%9%14%23%13%5%
2376
September1st to 10thDay
36%8%11%20%19%6%
2160
11th to 20thDay
37%7%13%16%22%5%
2121
21st to endDay
31%6%8%20%26%8%
1895
October1st to 10thDay
28%6%10%21%27%8%
1800
11th to 20thDay
32%47%18%29%11%
1800
21st to endDay
37%47%21%22%10%
1980
November1st to 10thDay
30%5%8%25%23%9%
1858
11th to 20thDay
30%5%8%21%28%9%
1900
21st to endDay
43%36%18%25%6%
1640
December1st to 10thDay
39%5%10%22%18%6%
1520
11th to 20thDay
43%5%6%18%23%5%
1961
21st to endDay
43%8%10%16%17%6%
3135
January1st to 10thNight
37%48%20%27%5%
2458
11th to 20thNight
39%5%9%21%21%6%
2470
21st to endNight
35%37%23%26%6%
2600
February1st to 10thNight
45%49%19%18%6%
2340
11th to 20thNight
43%47%21%20%6%
2183
21st to endNight
42%48%16%21%9%
1706
March1st to 10thNight
40%310%14%21%12%
1980
11th to 20thNight
45%48%20%17%7%
1980
21st to endNight
43%5%9%21%19%4
2178
April1st to 10thNight
33%6%10%23%20%8%
1828
11th to 20thNight
33%6%9%23%21%8%
1775
21st to endNight
35%6%12%23%21%3
1800
May1st to 10thNight
35%7%12%23%19%5%
1782
11th to 20thNight
36%7%14%24%16%2
1594
21st to endNight
34%9%16%25%16%1
1746
June1st to 10thNight
23%9%15%31%19%2
1620
11th to 20thNight
21%6%14%33%22%3
1620
21st to endNight
19%7%13%30%24%6%
1620
July1st to 10thNight
27%11%22%23%16%1
1575
11th to 20thNight
19%10%21%28%19%3
1566
21st to endNight
22%11%17%32%17%1
1673
August1st to 10thNight
24%8%22%31%13%
1601
11th to 20thNight
26%9%14%29%19%2
1733
21st to endNight
25%9%18%26%19%3
1980
September1st to 10thNight
26%7%12%24%23%8%
1800
11th to 20thNight
30%8%12%19%25%6%
1835
21st to endNight
24%5%10%22%29%9%
2045
October1st to 10thNight
24%5%13%22%24%11%
2160
11th to 20thNight
28%5%8%17%31%12%
2160
21st to endNight
36%45%20%24%11%
2376
November1st to 10thNight
28%5%8%23%26%10%
2220
11th to 20thNight
31%47%22%26%10%
2280
21st to endNight
36%47%19%27%6%
2531
December1st to 10thNight
40%5%9%19%21%7%
2660
11th to 20thNight
40%46%18%25%7%
3213
21st to endNight
39%6%9%23%19%4
4532

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
27%18%31%17%6%1
270
11th to 20thDay
25%27%32%13%2
270
21st to endDay
23%26%33%13%41
267
February1st to 10thDay
31%17%36%12%41
240
11th to 20thDay
30%27%30%12%1
240
21st to endDay
38%23%28%9%21
198
March1st to 10thDay
29%18%34%15%4
240
11th to 20thDay
33%20%33%13%2
240
21st to endDay
27%27%34%9%3
264
April1st to 10thDay
19%21%35%16%8%
392
11th to 20thDay
26%15%31%20%6%1
412
21st to endDay
20%19%35%17%7%2
420
May1st to 10thDay
21%15%32%23%8%1
437
11th to 20thDay
16%10%29%27%16%2
625
21st to endDay
11%7%28%33%16%5%
679
June1st to 10thDay
10%5%20%29%28%7%
630
11th to 20thDay
6%321%39%25%6%
630
21st to endDay
5%423%36%24%8%
630
July1st to 10thDay
6%215%32%33%11%
621
11th to 20thDay
6%215%31%36%11%
618
21st to endDay
7%211%33%34%13%
684
August1st to 10thDay
7%314%36%32%8%
626
11th to 20thDay
13%210%33%33%9%
482
21st to endDay
12%26%29%36%15%
495
September1st to 10thDay
12%310%28%38%10%
450
11th to 20thDay
11%413%25%36%11%
411
21st to endDay
12%5%17%39%21%6%
270
October1st to 10thDay
6%5%30%36%20%3
270
11th to 20thDay
17%14%33%23%11%2
270
21st to endDay
28%16%30%18%7%1
297
November1st to 10thDay
17%14%33%20%14%2
270
11th to 20thDay
15%17%36%25%41
270
21st to endDay
28%16%24%21%10%
270
December1st to 10thDay
22%26%27%17%7%1
270
11th to 20thDay
24%21%31%19%6%
270
21st to endDay
25%20%38%14%3
297
January1st to 10thNight
21%18%29%28%4
950
11th to 20thNight
23%18%31%24%4
950
21st to endNight
21%15%36%26%4
1000
February1st to 10thNight
26%17%30%23%4
900
11th to 20thNight
22%19%36%22%1
788
21st to endNight
27%19%32%20%3
522
March1st to 10thNight
22%13%29%31%5%
540
11th to 20thNight
23%14%30%28%5%1
540
21st to endNight
20%13%32%29%6%
594
April1st to 10thNight
15%15%36%28%7%
540
11th to 20thNight
14%15%33%27%11%
533
21st to endNight
15%12%38%26%9%
540
May1st to 10thNight
13%8%28%40%10%1
540
11th to 20thNight
12%9%27%31%20%2
531
21st to endNight
10%6%22%35%23%5%
584
June1st to 10thNight
6%214%36%37%5%
540
11th to 20thNight
5%114%43%35%3
540
21st to endNight
4114%38%37%6%
540
July1st to 10thNight
3110%35%43%8%
525
11th to 20thNight
3111%31%45%9%
522
21st to endNight
416%37%42%11%
591
August1st to 10thNight
5%17%38%42%6%
537
11th to 20thNight
8%210%36%37%7%
534
21st to endNight
7%17%34%43%8%
594
September1st to 10thNight
9%19%31%46%4
540
11th to 20thNight
11%112%32%40%4
540
21st to endNight
10%215%31%36%5%
605
October1st to 10thNight
9%317%36%31%4
720
11th to 20thNight
13%8%25%38%15%1
720
21st to endNight
21%8%27%27%15%2
792
November1st to 10thNight
11%10%25%37%15%2
740
11th to 20thNight
14%11%31%33%12%
760
21st to endNight
18%16%28%27%11%
836
December1st to 10thNight
22%11%33%28%7%
950
11th to 20thNight
21%14%29%29%6%
950
21st to endNight
21%17%28%28%5%
1045
Page generated at 2024-01-19 08:28:34. Version ac07

Copyright 2024 Attilla Danko


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