Cave Mountain Observatory Retreat
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cave Mountain Observatory Retreat clear sky chart from 2005-11-05 to 2019-06-02.

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%
17621
18%
53911
10%
17584
45%
17584
22%
34707

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
16%
836
19%
2717
6%
836
31%
836
12%
1797
January16th to endNight
15%
896
18%
2912
4%
896
33%
896
13%
1919
February1st to 15thNight
16%
822
17%
2677
6%
821
30%
821
14%
1727
February16th to endNight
15%
735
17%
2235
4%
735
29%
735
12%
1565
March1st to 15thNight
20%
840
20%
2310
7%
840
33%
840
18%
1569
March16th to endNight
25%
896
16%
2464
8%
896
32%
896
19%
1674
April1st to 15thNight
24%
838
16%
2146
5%
838
31%
838
21%
1460
April16th to endNight
34%
758
18%
2004
7%
758
40%
758
26%
1333
May1st to 15thNight
41%
630
14%
1890
7%
630
47%
630
22%
1271
May16th to endNight
48%
576
14%
1891
10%
576
52%
576
26%
1191
June1st to 15thNight
56%
392
17%
1569
18%
392
62%
392
24%
899
June16th to endNight
56%
390
19%
1560
18%
390
64%
390
26%
876
July1st to 15thNight
57%
519
12%
1629
12%
519
59%
519
29%
1022
July16th to endNight
66%
612
17%
1739
13%
579
69%
579
36%
1018
August1st to 15thNight
65%
575
19%
1715
14%
572
68%
572
32%
1056
August16th to endNight
66%
741
19%
1983
13%
741
67%
741
34%
1244
September1st to 15thNight
57%
780
23%
1976
14%
780
61%
780
33%
1285
September16th to endNight
52%
777
23%
2167
19%
777
56%
777
29%
1388
October1st to 15thNight
46%
780
22%
2340
18%
780
53%
780
26%
1468
October16th to endNight
32%
832
25%
2496
14%
832
47%
832
26%
1502
November1st to 15thNight
37%
820
24%
2510
15%
820
47%
820
24%
1582
November16th to endNight
28%
840
18%
2940
10%
840
40%
840
17%
1841
December1st to 15thNight
25%
840
15%
2940
7%
840
36%
840
13%
1967
December16th to endNight
21%
896
18%
3101
7%
896
37%
896
14%
2053

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%36%6%45%5%5%7%37%
54395
Night
10%5%25%5%35%5%6%8%41%
54104
Cloud CoverDay
12%6%36%6%35%5%5%7%37%
54405
Night
10%6%25%5%35%5%5%7%42%
54108
TransparencyDay
46%412%21%13%2
54106
Night
41%5%14%23%13%2
53911
SeeingDay
22%13%24%21%13%5%
7724
Night
20%13%24%27%13%1
17629

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
8%6%48%7%46%5%6%6%34%
1881
16th to endDay
9%7%47%5%35%46%6%38%
2016
February1st to 15thDay
10%8%37%5%46%45%8%35%
1845
16th to endDay
9%10%37%5%345%46%38%
1806
March1st to 15thDay
11%7%36%6%35%446%41%
2299
16th to endDay
13%8%46%6%45%45%5%35%
2464
April1st to 15thDay
10%6%36%5%35%5%5%7%40%
2462
16th to endDay
13%5%26%5%3446%7%39%
2572
May1st to 15thDay
18%6%36%5%45%45%7%32%
2721
16th to endDay
12%5%35%6%45%5%6%8%35%
2926
June1st to 15thDay
12%424446%6%6%8%39%
2744
16th to endDay
9%425%5%46%6%7%9%37%
2730
July1st to 15thDay
10%6%26%6%47%6%6%7%35%
2566
16th to endDay
8%5%26%7%47%7%6%9%33%
2673
August1st to 15thDay
10%5%26%8%47%7%7%8%31%
2487
16th to endDay
10%435%7%6%6%5%7%9%34%
2556
September1st to 15thDay
14%5%26%6%345%5%6%39%
2311
16th to endDay
16%6%26%6%44445%37%
2122
October1st to 15thDay
15%7%245%33346%42%
1950
16th to endDay
12%7%25%424346%46%
2080
November1st to 15thDay
11%6%25%43345%6%45%
2001
16th to endDay
12%6%45%5%35%35%7%41%
1680
December1st to 15thDay
11%7%36%6%45%5%5%6%36%
1680
16th to endDay
12%8%36%7%36%5%6%6%33%
1823
January1st to 15thNight
8%7%26%6%35%5%6%8%38%
2717
16th to endNight
9%8%37%5%345%5%7%39%
2912
February1st to 15thNight
9%6%35%6%35%5%6%7%39%
2675
16th to endNight
9%8%36%6%36%5%5%7%34%
2235
March1st to 15thNight
11%6%25%5%35%5%6%7%41%
2298
16th to endNight
12%7%345%35%5%6%6%39%
2464
April1st to 15thNight
8%6%36%5%35%5%5%8%41%
2146
16th to endNight
13%5%2443346%8%43%
2004
May1st to 15thNight
13%5%35%5%25%5%5%8%38%
1890
16th to endNight
11%4244245%5%8%45%
1889
June1st to 15thNight
9%3144345%6%10%46%
1569
16th to endNight
7%214435%5%7%9%48%
1560
July1st to 15thNight
9%414425%6%6%9%44%
1719
16th to endNight
5%324336%47%11%46%
1847
August1st to 15thNight
7%4245%35%5%7%10%44%
1726
16th to endNight
7%4244345%5%9%45%
1983
September1st to 15thNight
12%41442446%7%46%
1976
16th to endNight
14%5%2443445%6%45%
2167
October1st to 15thNight
17%413325%35%6%45%
2340
16th to endNight
11%5%23425%45%6%48%
2496
November1st to 15thNight
11%7%25%5%235%5%5%45%
2510
16th to endNight
11%5%36%6%35%5%6%7%40%
2940
December1st to 15thNight
10%5%27%8%46%5%6%7%34%
2940
16th to endNight
10%6%26%6%36%6%5%8%36%
3101

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
8%7%48%7%46%5%6%5%34%
1881
16th to endDay
10%8%46%445%5%5%6%37%
2016
February1st to 15thDay
11%8%47%6%45%45%7%35%
1845
16th to endDay
9%9%48%5%345%46%38%
1806
March1st to 15thDay
12%8%36%5%35%346%41%
2310
16th to endDay
13%8%37%7%35%445%35%
2463
April1st to 15thDay
11%6%36%5%245%5%6%41%
2462
16th to endDay
14%5%25%5%3446%7%38%
2572
May1st to 15thDay
19%5%36%5%35%45%7%32%
2721
16th to endDay
12%5%36%7%45%5%5%8%36%
2926
June1st to 15thDay
12%4245%46%6%6%8%39%
2744
16th to endDay
9%425%6%46%6%6%10%37%
2730
July1st to 15thDay
10%6%35%7%46%5%6%7%35%
2566
16th to endDay
9%5%26%7%46%7%7%9%33%
2673
August1st to 15thDay
10%5%26%7%5%6%7%6%8%32%
2487
16th to endDay
10%425%7%5%6%7%7%9%34%
2556
September1st to 15thDay
14%5%26%6%245%5%6%40%
2311
16th to endDay
16%6%26%5%45%446%37%
2122
October1st to 15thDay
16%6%35%5%24346%42%
1950
16th to endDay
13%7%25%334346%46%
2080
November1st to 15thDay
12%6%2442345%6%46%
2001
16th to endDay
12%7%445%3445%6%41%
1680
December1st to 15thDay
11%7%37%6%45%5%5%6%36%
1680
16th to endDay
13%9%36%6%35%5%6%6%33%
1823
January1st to 15thNight
9%8%27%5%35%5%5%8%38%
2717
16th to endNight
9%9%36%5%35%5%5%6%39%
2912
February1st to 15thNight
9%7%35%5%35%5%6%8%39%
2668
16th to endNight
10%7%36%6%46%6%5%7%35%
2235
March1st to 15thNight
12%6%25%5%35%5%5%7%41%
2310
16th to endNight
12%7%346%35%46%6%40%
2464
April1st to 15thNight
9%6%26%435%5%5%8%41%
2146
16th to endNight
12%5%245%3345%8%43%
2004
May1st to 15thNight
14%5%35%6%245%6%8%38%
1889
16th to endNight
11%4244335%6%8%45%
1889
June1st to 15thNight
9%2144345%5%10%46%
1569
16th to endNight
6%3145%245%6%10%48%
1560
July1st to 15thNight
9%3244345%6%9%44%
1719
16th to endNight
5%323435%5%7%11%46%
1847
August1st to 15thNight
6%425%436%5%7%10%44%
1726
16th to endNight
7%415%425%5%6%9%45%
1983
September1st to 15thNight
12%315%42445%6%47%
1976
16th to endNight
14%5%2443445%6%45%
2167
October1st to 15thNight
17%42332435%6%45%
2340
16th to endNight
12%5%23425%45%6%48%
2496
November1st to 15thNight
12%7%25%42346%5%45%
2510
16th to endNight
11%6%35%5%35%5%5%7%40%
2940
December1st to 15thNight
10%6%36%7%46%5%6%7%35%
2940
16th to endNight
11%7%25%7%35%5%6%7%36%
3101

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
50%311%19%12%2
1882
16th to endDay
47%313%20%13%2
2016
February1st to 15thDay
50%411%19%12%1
1847
16th to endDay
48%213%21%11%1
1806
March1st to 15thDay
45%311%23%12%2
2310
16th to endDay
51%310%18%14%1
2464
April1st to 15thDay
44%411%21%15%3
2462
16th to endDay
44%311%21%15%4
2572
May1st to 15thDay
51%414%18%9%1
2721
16th to endDay
46%6%16%21%8%1
2930
June1st to 15thDay
41%7%15%22%11%
2744
16th to endDay
41%7%16%20%12%1
2730
July1st to 15thDay
45%6%12%19%13%2
2427
16th to endDay
45%7%12%19%12%1
2518
August1st to 15thDay
47%6%15%19%10%
2474
16th to endDay
44%6%15%21%10%
2556
September1st to 15thDay
44%5%11%19%17%1
2311
16th to endDay
48%47%23%13%1
2122
October1st to 15thDay
45%212%22%13%3
1950
16th to endDay
41%29%26%18%2
2080
November1st to 15thDay
40%310%22%18%5%
2001
16th to endDay
44%211%24%15%1
1680
December1st to 15thDay
48%413%19%12%2
1680
16th to endDay
51%5%11%21%9%1
1823
January1st to 15thNight
44%6%12%19%13%3
2717
16th to endNight
47%312%22%12%2
2912
February1st to 15thNight
44%414%23%11%1
2677
16th to endNight
50%5%12%21%9%1
2235
March1st to 15thNight
44%412%26%9%2
2310
16th to endNight
44%414%21%13%1
2464
April1st to 15thNight
42%5%13%22%13%2
2146
16th to endNight
39%5%13%21%15%4
2004
May1st to 15thNight
44%6%17%20%9%1
1890
16th to endNight
37%8%19%22%10%1
1891
June1st to 15thNight
34%8%18%26%12%
1569
16th to endNight
32%8%16%25%15%1
1560
July1st to 15thNight
36%7%20%19%13%2
1629
16th to endNight
28%8%20%26%14%1
1739
August1st to 15thNight
34%6%19%24%13%
1715
16th to endNight
34%6%16%29%12%1
1983
September1st to 15thNight
36%6%15%21%18%1
1976
16th to endNight
38%5%10%28%16%
2167
October1st to 15thNight
40%313%25%13%2
2340
16th to endNight
36%312%27%18%1
2496
November1st to 15thNight
41%310%20%17%6%
2510
16th to endNight
43%312%21%15%2
2940
December1st to 15thNight
48%413%20%10%1
2940
16th to endNight
47%5%14%22%9%
3101

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%23%32%7%5%
180
16th to endDay
45%20%27%6%
192
February1st to 15thDay
41%22%27%7%
180
16th to endDay
35%18%32%13%
229
March1st to 15thDay
30%21%28%16%3
390
16th to endDay
26%19%28%18%6%
416
April1st to 15thDay
25%22%24%18%6%1
390
16th to endDay
24%16%28%16%9%4
379
May1st to 15thDay
28%13%24%19%9%4
408
16th to endDay
20%11%25%20%15%5%
459
June1st to 15thDay
16%9%22%25%19%7%
379
16th to endDay
13%12%29%23%16%4
375
July1st to 15thDay
13%6%29%26%15%8%
365
16th to endDay
10%5%21%26%23%12%
390
August1st to 15thDay
15%5%16%27%23%12%
358
16th to endDay
8%415%32%23%15%
396
September1st to 15thDay
19%8%13%22%24%12%
375
16th to endDay
22%6%20%23%18%9%
374
October1st to 15thDay
20%9%16%27%20%6%
375
16th to endDay
24%16%27%20%10%1
400
November1st to 15thDay
23%12%24%25%11%1
337
16th to endDay
26%15%32%18%6%
120
December1st to 15thDay
35%19%26%12%5%
120
16th to endDay
36%23%27%13%
137
January1st to 15thNight
29%22%27%17%2
840
16th to endNight
26%24%30%17%1
896
February1st to 15thNight
27%21%30%18%1
824
16th to endNight
27%23%30%17%
735
March1st to 15thNight
24%21%30%20%2
840
16th to endNight
22%17%29%22%6%1
896
April1st to 15thNight
20%22%29%21%5%
838
16th to endNight
21%12%25%27%10%
758
May1st to 15thNight
17%11%22%32%15%
630
16th to endNight
13%5%24%33%19%2
578
June1st to 15thNight
8%6%23%36%23%1
392
16th to endNight
6%423%45%17%1
390
July1st to 15thNight
10%316%39%26%2
519
16th to endNight
6%215%37%33%4
612
August1st to 15thNight
9%113%40%31%3
575
16th to endNight
9%112%39%33%3
741
September1st to 15thNight
13%5%15%31%28%5%
780
16th to endNight
16%5%16%29%27%3
777
October1st to 15thNight
21%10%16%28%20%3
780
16th to endNight
21%15%27%24%10%1
832
November1st to 15thNight
21%11%25%28%12%1
820
16th to endNight
23%18%25%22%8%
840
December1st to 15thNight
24%18%28%24%5%
840
16th to endNight
26%16%30%24%1
896
Page generated at 2019-06-02 19:43:10. Version ac04

Copyright 2019 A. Danko


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