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Hidden Creek Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hidden Creek Observatory clear sky chart from 2005-11-05 to 2019-09-17.

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%
17978
21%
54841
12%
17942
50%
17942
25%
34682

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
23%
836
24%
2731
8%
836
41%
836
20%
1717
January16th to endNight
23%
896
24%
2912
10%
896
42%
896
23%
1800
February1st to 15thNight
24%
821
21%
2677
9%
821
40%
821
22%
1652
February16th to endNight
20%
735
25%
2229
9%
735
38%
735
22%
1407
March1st to 15thNight
24%
840
24%
2310
10%
840
38%
840
26%
1501
March16th to endNight
27%
896
21%
2464
9%
896
38%
896
25%
1622
April1st to 15thNight
27%
838
22%
2100
6%
838
38%
838
30%
1352
April16th to endNight
37%
831
20%
2077
7%
831
43%
831
31%
1376
May1st to 15thNight
40%
658
16%
1918
8%
658
45%
658
24%
1304
May16th to endNight
53%
512
16%
1826
13%
512
57%
512
23%
1135
June1st to 15thNight
60%
420
18%
1680
21%
420
64%
420
23%
993
June16th to endNight
61%
420
17%
1680
18%
420
66%
420
24%
959
July1st to 15thNight
63%
497
15%
1697
16%
497
64%
497
26%
1062
July16th to endNight
69%
660
16%
1883
12%
627
72%
627
31%
1183
August1st to 15thNight
66%
620
16%
1850
13%
617
67%
617
28%
1223
August16th to endNight
63%
868
17%
2206
11%
868
64%
868
30%
1493
September1st to 15thNight
59%
840
23%
2100
16%
840
61%
840
31%
1415
September16th to endNight
51%
782
20%
2173
17%
782
53%
782
26%
1483
October1st to 15thNight
49%
780
24%
2340
21%
780
56%
780
27%
1495
October16th to endNight
41%
832
29%
2496
19%
832
55%
832
33%
1446
November1st to 15thNight
38%
820
26%
2528
16%
820
50%
820
27%
1568
November16th to endNight
35%
840
23%
2888
14%
840
49%
840
26%
1641
December1st to 15thNight
28%
840
19%
2940
10%
840
42%
840
19%
1906
December16th to endNight
31%
896
22%
3136
12%
896
46%
896
21%
1949

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
14%5%25%5%3445%7%42%
55831
Night
14%5%2442445%7%43%
55032
Cloud CoverDay
14%5%245%3445%7%42%
55841
Night
14%5%2442445%7%43%
55036
TransparencyDay
40%6%11%22%16%3
55539
Night
39%5%10%22%17%3
54842
SeeingDay
18%8%26%24%15%6%
8282
Night
17%8%27%29%14%1
17987

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
15%6%35%424446%42%
1865
16th to endDay
16%6%24324446%43%
2016
February1st to 15thDay
15%7%16%434446%40%
1845
16th to endDay
17%5%35%434447%39%
1814
March1st to 15thDay
16%5%15%424346%45%
2299
16th to endDay
16%5%25%5%34435%41%
2464
April1st to 15thDay
13%426%433445%48%
2506
16th to endDay
16%5%2443345%6%43%
2488
May1st to 15thDay
16%6%24435%5%6%7%37%
2703
16th to endDay
15%4145%35%5%5%8%40%
2992
June1st to 15thDay
13%3145%25%5%6%9%42%
2940
16th to endDay
8%3146%35%6%7%11%41%
2940
July1st to 15thDay
10%425%6%35%6%6%9%39%
2832
16th to endDay
8%325%6%36%6%7%11%37%
2881
August1st to 15thDay
11%436%7%46%5%6%9%35%
2682
16th to endDay
11%425%5%45%6%6%9%38%
2686
September1st to 15thDay
14%325%5%35%5%46%43%
2520
16th to endDay
19%5%25%5%2445%7%36%
2138
October1st to 15thDay
17%5%24423345%46%
1950
16th to endDay
13%424423325%52%
2080
November1st to 15thDay
16%5%24324335%48%
1989
16th to endDay
15%413223446%51%
1729
December1st to 15thDay
17%6%24323446%43%
1680
16th to endDay
19%6%35%42435%5%40%
1792
January1st to 15thNight
18%4335%24346%44%
2731
16th to endNight
16%6%24323445%45%
2912
February1st to 15thNight
14%6%25%324446%44%
2675
16th to endNight
16%6%24423335%45%
2229
March1st to 15thNight
16%5%243235%5%6%44%
2298
16th to endNight
17%5%35%423336%44%
2464
April1st to 15thNight
12%5%245%2345%8%46%
2100
16th to endNight
14%5%24323448%45%
2077
May1st to 15thNight
17%5%35%4235%5%8%37%
1918
16th to endNight
13%4144245%6%9%40%
1825
June1st to 15thNight
10%3236%3447%10%42%
1680
16th to endNight
7%4245%35%5%6%10%43%
1680
July1st to 15thNight
8%5%25%435%5%6%9%42%
1784
16th to endNight
6%324445%6%8%10%42%
1991
August1st to 15thNight
9%325%5%36%6%6%8%40%
1861
16th to endNight
11%5%25%5%35%5%6%10%38%
2206
September1st to 15thNight
14%5%244235%48%44%
2100
16th to endNight
17%7%26%324435%41%
2173
October1st to 15thNight
18%5%13423446%44%
2340
16th to endNight
15%313313345%52%
2496
November1st to 15thNight
16%5%24423435%48%
2528
16th to endNight
13%41442345%5%49%
2888
December1st to 15thNight
16%6%35%5%24446%39%
2940
16th to endNight
16%6%2442445%6%41%
3136

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
16%6%34423446%42%
1865
16th to endDay
16%6%24324446%43%
2016
February1st to 15thDay
15%6%25%5%25%446%41%
1845
16th to endDay
17%5%36%5%24446%39%
1814
March1st to 15thDay
16%5%25%424346%45%
2310
16th to endDay
16%5%25%5%34335%41%
2463
April1st to 15thDay
13%425%42345%6%48%
2506
16th to endDay
16%5%2443345%6%43%
2488
May1st to 15thDay
16%6%244345%5%7%37%
2703
16th to endDay
14%4145%35%45%9%40%
2992
June1st to 15thDay
12%424435%5%6%9%42%
2940
16th to endDay
8%3146%35%6%7%11%41%
2940
July1st to 15thDay
10%425%6%36%5%6%9%39%
2832
16th to endDay
7%325%6%46%7%7%11%37%
2881
August1st to 15thDay
11%5%26%7%45%6%5%9%35%
2682
16th to endDay
11%425%6%35%6%6%9%37%
2686
September1st to 15thDay
13%4246%35%5%46%43%
2520
16th to endDay
19%5%245%3446%7%36%
2138
October1st to 15thDay
17%424433345%45%
1950
16th to endDay
13%424423335%52%
2080
November1st to 15thDay
16%5%2342433448%
1989
16th to endDay
15%413223445%51%
1729
December1st to 15thDay
16%6%23423446%43%
1680
16th to endDay
18%6%36%423345%40%
1792
January1st to 15thNight
18%5%24433345%44%
2731
16th to endNight
16%6%24323445%45%
2912
February1st to 15thNight
15%6%25%424446%44%
2668
16th to endNight
16%6%25%424346%45%
2229
March1st to 15thNight
16%5%2432345%6%44%
2310
16th to endNight
17%5%35%323337%44%
2464
April1st to 15thNight
12%5%2442345%7%46%
2100
16th to endNight
14%5%2432345%8%45%
2077
May1st to 15thNight
16%5%25%4345%5%8%38%
1917
16th to endNight
12%4144346%6%10%40%
1825
June1st to 15thNight
10%4245%35%47%10%42%
1680
16th to endNight
7%4245%35%6%6%10%44%
1680
July1st to 15thNight
8%5%35%4245%6%9%43%
1784
16th to endNight
6%3245%36%6%7%10%42%
1991
August1st to 15thNight
9%435%5%36%5%6%9%40%
1861
16th to endNight
10%5%16%6%35%5%6%10%38%
2206
September1st to 15thNight
13%5%2442345%7%44%
2100
16th to endNight
17%6%26%424435%41%
2173
October1st to 15thNight
18%5%13423346%44%
2340
16th to endNight
15%31332335%5%52%
2496
November1st to 15thNight
16%5%24323345%48%
2528
16th to endNight
13%41442445%6%49%
2888
December1st to 15thNight
16%6%35%5%24446%39%
2940
16th to endNight
16%6%3442335%6%41%
3136

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
42%410%20%17%4
1866
16th to endDay
40%410%23%16%4
2016
February1st to 15thDay
44%48%24%15%2
1847
16th to endDay
45%49%20%17%2
1814
March1st to 15thDay
40%49%21%18%5%
2310
16th to endDay
44%48%19%17%4
2464
April1st to 15thDay
37%410%24%18%5%
2506
16th to endDay
41%410%19%16%6%
2488
May1st to 15thDay
43%7%13%19%14%1
2703
16th to endDay
39%7%15%24%12%
2996
June1st to 15thDay
36%8%16%23%13%1
2940
16th to endDay
34%9%16%22%15%1
2940
July1st to 15thDay
38%7%13%21%14%3
2690
16th to endDay
36%9%14%22%15%1
2726
August1st to 15thDay
43%8%13%21%11%1
2669
16th to endDay
38%9%15%21%12%2
2686
September1st to 15thDay
39%6%11%18%19%3
2520
16th to endDay
45%6%9%20%17%1
2138
October1st to 15thDay
40%48%24%18%3
1950
16th to endDay
35%35%28%22%4
2080
November1st to 15thDay
39%38%20%21%5%
1989
16th to endDay
34%410%24%23%4
1729
December1st to 15thDay
41%411%22%15%4
1680
16th to endDay
45%49%23%15%1
1792
January1st to 15thNight
42%48%18%18%7%
2731
16th to endNight
40%49%24%18%3
2912
February1st to 15thNight
40%48%24%17%4
2677
16th to endNight
41%38%24%18%4
2229
March1st to 15thNight
40%49%24%18%3
2310
16th to endNight
41%49%21%19%3
2464
April1st to 15thNight
36%5%11%21%20%5%
2100
16th to endNight
37%6%11%20%17%7%
2077
May1st to 15thNight
43%6%13%18%13%2
1918
16th to endNight
37%10%14%23%11%2
1827
June1st to 15thNight
36%8%13%24%15%1
1680
16th to endNight
34%8%16%20%18%2
1680
July1st to 15thNight
36%9%14%20%15%3
1697
16th to endNight
33%9%16%25%13%1
1883
August1st to 15thNight
38%9%15%21%14%1
1850
16th to endNight
39%8%14%23%12%2
2206
September1st to 15thNight
37%8%13%20%15%3
2100
16th to endNight
44%5%8%19%18%3
2173
October1st to 15thNight
40%5%9%23%17%4
2340
16th to endNight
33%37%25%24%5%
2496
November1st to 15thNight
38%47%20%21%7%
2528
16th to endNight
35%49%23%22%4
2888
December1st to 15thNight
45%5%9%21%15%3
2940
16th to endNight
42%411%23%14%3
3136

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
27%21%34%15%1
176
16th to endDay
28%20%35%11%4
192
February1st to 15thDay
29%22%36%6%5%
180
16th to endDay
27%15%33%20%2
295
March1st to 15thDay
21%17%37%19%4
390
16th to endDay
20%17%32%21%6%1
416
April1st to 15thDay
20%15%31%20%8%2
390
16th to endDay
21%9%31%23%10%3
379
May1st to 15thDay
23%9%30%20%11%3
408
16th to endDay
19%327%25%19%4
459
June1st to 15thDay
15%424%27%20%6%
435
16th to endDay
9%5%26%30%20%6%
435
July1st to 15thDay
11%18%33%26%10%
425
16th to endDay
9%119%31%25%12%
454
August1st to 15thDay
10%219%28%26%12%
418
16th to endDay
11%213%28%27%15%
460
September1st to 15thDay
18%217%22%20%18%
435
16th to endDay
28%215%27%14%11%
378
October1st to 15thDay
22%418%24%22%8%
375
16th to endDay
13%14%28%25%15%2
400
November1st to 15thDay
24%9%23%25%13%3
365
16th to endDay
17%13%33%23%10%1
169
December1st to 15thDay
25%14%35%13%11%
120
16th to endDay
30%16%32%20%
128
January1st to 15thNight
22%15%33%23%5%
840
16th to endNight
20%13%39%24%2
896
February1st to 15thNight
20%12%38%25%2
824
16th to endNight
21%17%37%21%2
735
March1st to 15thNight
20%15%35%24%3
840
16th to endNight
20%12%35%24%7%
896
April1st to 15thNight
15%15%38%23%6%
838
16th to endNight
17%9%32%31%9%
831
May1st to 15thNight
19%5%28%29%15%
658
16th to endNight
14%122%37%21%1
514
June1st to 15thNight
10%117%40%28%1
420
16th to endNight
8%219%44%22%1
420
July1st to 15thNight
10%115%37%32%3
497
16th to endNight
7%112%38%33%6%
660
August1st to 15thNight
11%10%41%31%3
620
16th to endNight
11%112%37%30%5%
868
September1st to 15thNight
15%115%33%30%4
840
16th to endNight
20%317%29%25%3
782
October1st to 15thNight
23%317%29%21%3
780
16th to endNight
17%8%30%27%15%
832
November1st to 15thNight
17%10%28%28%14%1
820
16th to endNight
15%10%32%28%10%1
840
December1st to 15thNight
21%10%33%24%9%
840
16th to endNight
20%10%32%32%3
896
Page generated at 2019-09-17 21:12:15. Version ac04

Copyright 2019 A. Danko


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