Crystal Mountain
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Crystal Mountain clear sky chart from 2005-11-05 to 2017-09-20.

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%
15667
25%
47225
17%
15620
54%
15620
31%
27911

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
28%
900
28%
2327
9%
895
41%
895
28%
1459
January16th to endNight
25%
960
28%
2496
9%
960
37%
960
29%
1571
February1st to 15thNight
22%
879
20%
2287
5%
875
31%
875
26%
1502
February16th to endNight
23%
585
27%
1847
9%
585
38%
585
26%
1073
March1st to 15thNight
28%
540
22%
1980
13%
540
40%
540
21%
1218
March16th to endNight
34%
576
20%
2112
15%
576
43%
576
22%
1300
April1st to 15thNight
31%
539
25%
1815
13%
539
48%
539
28%
1014
April16th to endNight
35%
540
23%
1800
16%
540
49%
540
28%
1042
May1st to 15thNight
45%
540
19%
1728
14%
540
54%
540
26%
1072
May16th to endNight
51%
563
21%
1685
16%
561
58%
561
30%
1035
June1st to 15thNight
75%
540
23%
1620
21%
540
79%
540
45%
860
June16th to endNight
73%
540
24%
1620
23%
540
77%
540
43%
871
July1st to 15thNight
70%
510
17%
1530
19%
510
72%
510
34%
900
July16th to endNight
84%
564
24%
1594
28%
531
84%
531
42%
866
August1st to 15thNight
76%
539
23%
1640
27%
536
78%
536
40%
892
August16th to endNight
76%
573
23%
1910
28%
573
76%
573
32%
1087
September1st to 15thNight
68%
540
25%
1800
28%
540
70%
540
34%
1017
September16th to endNight
65%
547
31%
1874
29%
547
70%
547
36%
997
October1st to 15thNight
58%
660
30%
1980
23%
660
62%
660
38%
1119
October16th to endNight
49%
704
34%
2112
22%
704
60%
704
39%
1140
November1st to 15thNight
48%
700
31%
2100
21%
700
57%
700
35%
1168
November16th to endNight
35%
768
29%
2319
16%
768
48%
768
28%
1391
December1st to 15thNight
32%
900
21%
2520
10%
900
41%
900
27%
1635
December16th to endNight
29%
960
24%
2529
9%
960
39%
960
25%
1682

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%5%3445%6%43%
47604
Night
11%42432345%7%50%
47420
TransparencyDay
40%6%10%20%17%4
47304
Night
33%5%10%22%21%6%
47225
SeeingDay
14%6%21%27%22%7%
5716
Night
14%9%25%29%18%2
15667

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
15%6%23323345%48%
1611
16th to endDay
13%6%35%423235%48%
1728
February1st to 15thDay
16%7%2342333447%
1575
16th to endDay
14%7%46%5%3344441%
1637
March1st to 15thDay
18%6%24424435%43%
1980
16th to endDay
17%6%36%5%24345%40%
2110
April1st to 15thDay
12%6%25%4135%37%45%
2133
16th to endDay
15%6%35%5%34446%41%
2160
May1st to 15thDay
17%6%35%5%35%35%5%38%
2220
16th to endDay
10%5%37%7%36%6%6%6%35%
2430
June1st to 15thDay
6%425%6%46%5%6%9%40%
2340
16th to endDay
4325%6%47%6%6%10%40%
2340
July1st to 15thDay
7%5%37%7%5%6%6%7%8%34%
2340
16th to endDay
6%315%6%47%7%7%10%39%
2466
August1st to 15thDay
8%325%6%46%7%7%9%38%
2310
16th to endDay
9%425%5%47%6%7%8%37%
2292
September1st to 15thDay
14%5%15%435%5%5%6%43%
2160
16th to endDay
12%324425%345%51%
1840
October1st to 15thDay
12%5%25%422345%50%
1650
16th to endDay
13%312212335%58%
1760
November1st to 15thDay
10%423313345%57%
1758
16th to endDay
13%7%24323235%50%
1635
December1st to 15thDay
15%7%24423346%45%
1440
16th to endDay
15%7%36%5%3433343%
1689
January1st to 15thNight
15%5%23322335%52%
2327
16th to endNight
15%5%2332333452%
2496
February1st to 15thNight
15%6%36%323345%46%
2277
16th to endNight
13%5%2332335%5%51%
1847
March1st to 15thNight
17%6%25%423345%43%
1980
16th to endNight
14%6%25%434347%44%
2112
April1st to 15thNight
9%315%42335%7%52%
1815
16th to endNight
9%5%25%32435%6%50%
1800
May1st to 15thNight
12%423445%446%46%
1727
16th to endNight
7%5%25%5%3436%9%45%
1683
June1st to 15thNight
311232446%9%59%
1620
16th to endNight
421422445%10%56%
1620
July1st to 15thNight
3325%6%35%6%10%11%42%
1620
16th to endNight
31123346%6%12%53%
1702
August1st to 15thNight
4214425%5%6%11%50%
1650
16th to endNight
6%4143345%7%10%46%
1910
September1st to 15thNight
9%424323447%52%
1800
16th to endNight
7%4124235%5%7%54%
1874
October1st to 15thNight
10%423423346%55%
1980
16th to endNight
12%31322222363%
2112
November1st to 15thNight
8%413423346%56%
2100
16th to endNight
15%5%1432333451%
2319
December1st to 15thNight
15%6%25%323345%46%
2520
16th to endNight
15%6%345%23335%45%
2529

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
39%46%23%20%5%
1612
16th to endDay
40%26%23%22%4
1728
February1st to 15thDay
41%39%23%17%4
1576
16th to endDay
46%47%19%17%5%
1637
March1st to 15thDay
45%39%16%17%6%
1980
16th to endDay
46%5%10%22%14%1
2112
April1st to 15thDay
39%5%9%21%18%5%
2133
16th to endDay
43%5%8%19%18%3
2160
May1st to 15thDay
48%5%9%16%17%3
2220
16th to endDay
45%8%13%20%11%1
2434
June1st to 15thDay
37%8%13%23%16%1
2340
16th to endDay
35%9%13%22%16%2
2340
July1st to 15thDay
41%10%14%22%10%1
2201
16th to endDay
34%10%16%23%12%1
2311
August1st to 15thDay
37%10%13%21%14%2
2296
16th to endDay
41%9%13%18%13%3
2292
September1st to 15thDay
39%7%10%17%16%7%
2160
16th to endDay
33%5%10%20%23%6%
1840
October1st to 15thDay
36%48%18%23%8%
1650
16th to endDay
29%25%23%27%11%
1760
November1st to 15thDay
29%38%25%23%8%
1758
16th to endDay
39%36%19%25%6%
1635
December1st to 15thDay
40%5%10%20%16%5%
1440
16th to endDay
44%49%19%17%4
1689
January1st to 15thNight
37%26%21%27%4
2327
16th to endNight
36%37%23%22%6%
2496
February1st to 15thNight
40%49%21%18%5%
2287
16th to endNight
34%39%25%19%7%
1847
March1st to 15thNight
43%310%16%18%7%
1980
16th to endNight
42%49%22%18%3
2112
April1st to 15thNight
31%5%11%22%20%8%
1815
16th to endNight
34%5%11%22%22%4
1800
May1st to 15thNight
38%5%10%20%18%5%
1728
16th to endNight
35%7%17%24%15%1
1685
June1st to 15thNight
20%8%13%32%22%2
1620
16th to endNight
23%7%13%28%22%5%
1620
July1st to 15thNight
28%9%18%26%14%1
1530
16th to endNight
21%10%17%30%18%1
1594
August1st to 15thNight
25%7%17%28%18%2
1640
16th to endNight
29%8%16%25%17%2
1910
September1st to 15thNight
30%6%11%22%21%8%
1800
16th to endNight
27%5%10%22%25%9%
1874
October1st to 15thNight
29%411%18%23%12%
1980
16th to endNight
27%35%20%30%12%
2112
November1st to 15thNight
29%48%23%23%11%
2100
16th to endNight
37%36%18%28%6%
2319
December1st to 15thNight
41%39%19%18%6%
2520
16th to endNight
42%38%21%18%5%
2529

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%16%40%16%5%
90
16th to endDay
25%25%35%7%7%
96
February1st to 15thDay
23%14%45%12%31
90
16th to endDay
18%33%30%12%31
81
March1st to 15thDay
30%17%43%7%1
90
16th to endDay
19%20%32%25%2
96
April1st to 15thDay
20%17%34%16%9%1
252
16th to endDay
24%12%29%20%11%2
270
May1st to 15thDay
21%11%33%20%10%2
357
16th to endDay
14%6%30%29%13%4
517
June1st to 15thDay
9%218%34%27%7%
495
16th to endDay
6%222%36%26%6%
495
July1st to 15thDay
6%216%37%28%6%
475
16th to endDay
6%15%30%39%16%
515
August1st to 15thDay
10%10%34%31%12%
463
16th to endDay
16%6%28%35%12%
332
September1st to 15thDay
12%210%20%42%13%
315
16th to endDay
10%214%37%24%11%
135
October1st to 15thDay
10%330%38%13%4
90
16th to endDay
20%423%35%12%3
96
November1st to 15thDay
16%8%30%21%20%3
90
16th to endDay
33%16%25%15%7%1
90
December1st to 15thDay
22%17%32%16%8%2
90
16th to endDay
27%16%43%9%3
96
January1st to 15thNight
21%19%28%25%4
900
16th to endNight
19%17%36%23%3
960
February1st to 15thNight
22%17%34%22%3
879
16th to endNight
20%18%36%21%3
585
March1st to 15thNight
22%12%33%27%4
540
16th to endNight
16%11%33%30%7%
576
April1st to 15thNight
13%17%35%23%9%
539
16th to endNight
13%12%36%26%11%
540
May1st to 15thNight
14%7%28%36%11%1
540
16th to endNight
10%427%32%21%3
563
June1st to 15thNight
413%40%35%5%
540
16th to endNight
5%13%38%37%4
540
July1st to 15thNight
411%37%39%5%
510
16th to endNight
4432%47%10%
564
August1st to 15thNight
5%8%35%41%8%
539
16th to endNight
8%17%32%42%6%
573
September1st to 15thNight
11%12%27%43%4
540
16th to endNight
10%115%29%37%4
547
October1st to 15thNight
13%320%30%27%4
660
16th to endNight
15%8%24%32%18%1
704
November1st to 15thNight
10%12%24%34%16%1
700
16th to endNight
18%16%27%23%13%
768
December1st to 15thNight
21%12%31%27%7%
900
16th to endNight
22%14%29%26%6%
960
Page generated at 2017-09-21 06:18:17. Version ac04

Copyright 2017 A. Danko


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