Mountain City
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mountain City clear sky chart from 2005-11-05 to 2019-07-16.

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
40%
18101
17%
54225
11%
18059
46%
18059
19%
37559

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
19%
839
16%
2717
8%
836
31%
836
10%
2025
January16th to endNight
18%
896
16%
2912
7%
896
31%
896
12%
2097
February1st to 15thNight
22%
824
16%
2609
8%
821
32%
821
13%
1859
February16th to endNight
12%
735
16%
2205
6%
735
23%
735
11%
1663
March1st to 15thNight
20%
840
17%
2321
8%
840
28%
840
15%
1705
March16th to endNight
27%
896
13%
2464
7%
896
32%
896
17%
1799
April1st to 15thNight
30%
838
17%
2261
6%
838
38%
838
20%
1536
April16th to endNight
39%
656
17%
1902
10%
656
45%
656
20%
1306
May1st to 15thNight
40%
630
13%
1890
7%
630
45%
630
20%
1329
May16th to endNight
54%
657
12%
1972
9%
657
56%
657
22%
1361
June1st to 15thNight
61%
630
12%
1890
10%
630
63%
630
24%
1262
June16th to endNight
63%
630
14%
1890
11%
630
65%
630
25%
1239
July1st to 15thNight
62%
600
11%
1800
9%
600
62%
600
24%
1215
July16th to endNight
69%
615
11%
1748
10%
582
70%
582
25%
1164
August1st to 15thNight
69%
575
15%
1715
13%
572
69%
572
23%
1188
August16th to endNight
68%
675
17%
1933
15%
675
68%
675
26%
1301
September1st to 15thNight
58%
780
17%
2145
13%
780
60%
780
24%
1476
September16th to endNight
56%
777
21%
2145
18%
777
59%
777
27%
1441
October1st to 15thNight
48%
780
25%
2265
20%
780
55%
780
27%
1450
October16th to endNight
37%
832
26%
2496
18%
832
50%
832
25%
1578
November1st to 15thNight
44%
820
24%
2573
19%
820
53%
820
24%
1615
November16th to endNight
36%
840
23%
2730
15%
840
46%
840
20%
1736
December1st to 15thNight
25%
840
17%
2730
10%
840
34%
840
12%
1972
December16th to endNight
21%
896
15%
2912
7%
896
31%
896
10%
2242

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
15%9%47%6%35%5%5%7%31%
55085
Night
13%9%36%5%3445%7%36%
54422
TransparencyDay
50%7%10%16%11%2
54786
Night
45%7%11%18%12%2
54225
SeeingDay
22%14%20%19%14%8%
7926
Night
19%14%19%25%18%3
18104

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
18%11%49%7%33345%28%
1881
16th to endDay
13%12%8%7%435%345%30%
2016
February1st to 15thDay
17%12%5%8%6%33335%28%
1910
16th to endDay
21%11%5%8%323236%29%
1840
March1st to 15thDay
17%11%5%6%424245%36%
2297
16th to endDay
18%11%46%5%2435%6%31%
2463
April1st to 15thDay
14%9%35%42445%6%38%
2346
16th to endDay
17%8%35%425%45%6%35%
2674
May1st to 15thDay
17%7%37%6%45%5%5%6%29%
2721
16th to endDay
15%7%36%6%35%6%7%8%29%
2847
June1st to 15thDay
11%7%36%7%47%5%6%8%28%
2730
16th to endDay
10%6%36%8%47%6%8%8%29%
2730
July1st to 15thDay
13%7%47%7%46%6%7%9%24%
2730
16th to endDay
14%7%49%8%47%7%7%7%23%
2676
August1st to 15thDay
11%6%38%9%5%7%8%7%7%22%
2487
16th to endDay
11%6%37%7%47%8%6%8%27%
2604
September1st to 15thDay
13%7%37%6%46%6%5%7%28%
2145
16th to endDay
15%6%37%6%36%5%6%6%31%
2145
October1st to 15thDay
15%5%25%5%24446%42%
2025
16th to endDay
16%9%25%32333445%
2080
November1st to 15thDay
13%9%25%323446%43%
1942
16th to endDay
11%9%36%5%3435%6%40%
1890
December1st to 15thDay
16%13%47%5%34346%30%
1890
16th to endDay
16%13%5%6%5%345%45%29%
2016
January1st to 15thNight
15%10%5%10%7%34445%28%
2717
16th to endNight
15%12%6%8%5%3434432%
2912
February1st to 15thNight
14%12%5%7%6%2435%5%33%
2600
16th to endNight
17%12%5%9%6%23445%28%
2205
March1st to 15thNight
16%12%5%6%42434434%
2321
16th to endNight
13%11%46%435%46%7%32%
2464
April1st to 15thNight
13%9%35%4245%6%7%38%
2261
16th to endNight
13%6%346%25%46%6%38%
1902
May1st to 15thNight
15%7%26%5%345%7%8%34%
1889
16th to endNight
8%6%36%5%36%6%8%10%33%
1970
June1st to 15thNight
8%425%436%6%7%12%37%
1890
16th to endNight
7%5%25%5%36%6%8%10%38%
1890
July1st to 15thNight
9%6%26%5%35%6%7%10%36%
1890
16th to endNight
6%426%6%36%7%9%10%35%
1856
August1st to 15thNight
9%6%25%5%35%7%7%10%35%
1726
16th to endNight
7%426%5%37%6%8%10%36%
1933
September1st to 15thNight
11%6%25%5%345%6%8%38%
2145
16th to endNight
14%6%25%3245%5%6%43%
2145
October1st to 15thNight
13%5%2442345%8%46%
2265
16th to endNight
13%10%24333335%46%
2496
November1st to 15thNight
14%8%24323346%45%
2573
16th to endNight
11%9%36%32445%6%41%
2730
December1st to 15thNight
15%11%5%9%6%3435%5%29%
2730
16th to endNight
18%15%6%6%5%34346%24%
2912

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
57%47%15%10%4
1882
16th to endDay
54%47%19%11%2
2016
February1st to 15thDay
57%47%16%13%1
1912
16th to endDay
56%310%16%11%2
1840
March1st to 15thDay
51%48%17%14%4
2297
16th to endDay
53%6%9%19%9%1
2464
April1st to 15thDay
44%6%11%23%11%3
2346
16th to endDay
48%7%10%18%12%3
2674
May1st to 15thDay
53%8%12%18%7%
2721
16th to endDay
48%10%15%18%6%1
2851
June1st to 15thDay
50%10%14%16%7%
2730
16th to endDay
48%11%12%15%10%
2730
July1st to 15thDay
51%11%14%11%9%1
2591
16th to endDay
55%11%11%13%7%1
2521
August1st to 15thDay
55%12%11%13%6%
2474
16th to endDay
49%11%13%15%8%1
2604
September1st to 15thDay
51%10%11%13%10%2
2145
16th to endDay
49%8%9%15%14%1
2145
October1st to 15thDay
41%6%9%21%16%4
2025
16th to endDay
42%46%22%19%4
2080
November1st to 15thDay
42%47%16%23%6%
1942
16th to endDay
43%47%20%19%3
1890
December1st to 15thDay
54%47%16%13%3
1890
16th to endDay
55%6%10%14%11%2
2016
January1st to 15thNight
57%5%6%14%11%5%
2717
16th to endNight
55%38%15%14%2
2912
February1st to 15thNight
52%48%19%11%2
2609
16th to endNight
57%5%8%17%8%2
2205
March1st to 15thNight
52%5%8%17%12%2
2321
16th to endNight
49%7%12%19%10%
2464
April1st to 15thNight
42%7%13%22%11%3
2261
16th to endNight
44%7%11%18%14%2
1902
May1st to 15thNight
44%10%16%20%7%
1890
16th to endNight
40%12%18%19%6%1
1972
June1st to 15thNight
37%13%21%19%7%
1890
16th to endNight
36%11%18%20%11%1
1890
July1st to 15thNight
39%11%19%17%10%1
1800
16th to endNight
35%13%21%18%8%1
1748
August1st to 15thNight
40%12%17%18%10%
1715
16th to endNight
37%11%17%22%9%
1933
September1st to 15thNight
40%10%16%17%11%2
2145
16th to endNight
40%8%11%21%18%
2145
October1st to 15thNight
36%8%10%23%18%3
2265
16th to endNight
40%45%23%20%5%
2496
November1st to 15thNight
39%5%7%18%21%6%
2573
16th to endNight
42%5%7%20%20%3
2730
December1st to 15thNight
54%5%8%15%12%3
2730
16th to endNight
60%6%7%12%11%2
2912

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
30%32%27%7%11
180
16th to endDay
38%29%21%9%1
192
February1st to 15thDay
36%30%24%6%2
180
16th to endDay
43%22%29%4
159
March1st to 15thDay
28%30%21%13%5%
377
16th to endDay
25%24%25%16%6%1
416
April1st to 15thDay
25%19%24%18%9%2
390
16th to endDay
25%14%24%17%12%5%
379
May1st to 15thDay
25%15%24%16%11%7%
408
16th to endDay
19%9%20%21%14%15%
459
June1st to 15thDay
16%7%21%25%20%9%
435
16th to endDay
14%12%22%20%19%10%
435
July1st to 15thDay
16%416%27%19%15%
425
16th to endDay
14%318%26%20%16%
391
August1st to 15thDay
14%315%26%21%18%
358
16th to endDay
14%212%24%23%23%
396
September1st to 15thDay
17%5%11%19%29%16%
375
16th to endDay
15%5%19%22%23%13%
374
October1st to 15thDay
21%9%18%22%20%7%
375
16th to endDay
23%17%19%19%17%4
400
November1st to 15thDay
25%16%22%20%11%4
270
16th to endDay
18%23%26%22%7%1
180
December1st to 15thDay
31%25%27%14%1
180
16th to endDay
35%23%29%10%1
192
January1st to 15thNight
26%25%21%20%4
840
16th to endNight
25%28%23%19%3
896
February1st to 15thNight
26%25%22%22%2
824
16th to endNight
30%29%24%13%2
735
March1st to 15thNight
25%24%26%19%4
840
16th to endNight
20%18%28%23%8%
896
April1st to 15thNight
22%19%24%23%9%
838
16th to endNight
17%16%21%30%12%1
656
May1st to 15thNight
18%10%23%28%17%2
630
16th to endNight
11%5%17%29%29%7%
659
June1st to 15thNight
10%414%30%33%6%
630
16th to endNight
9%314%30%36%5%
630
July1st to 15thNight
14%111%27%39%4
600
16th to endNight
8%26%27%44%10%
615
August1st to 15thNight
11%8%34%37%7%
575
16th to endNight
10%8%29%40%10%
675
September1st to 15thNight
13%413%25%34%7%
780
16th to endNight
17%413%29%29%5%
777
October1st to 15thNight
17%10%17%22%24%6%
780
16th to endNight
19%15%23%23%15%2
832
November1st to 15thNight
19%13%18%28%16%3
820
16th to endNight
20%20%20%26%12%
840
December1st to 15thNight
26%20%20%23%7%
840
16th to endNight
30%21%20%23%4
896
Page generated at 2019-07-17 08:53:05. Version ac04

Copyright 2019 A. Danko


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