Elk Creek Visitor's Center
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Elk Creek Visitor's Center clear sky chart from 2005-11-05 to 2017-10-31.

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
59%
16025
25%
47423
19%
15985
64%
15985
40%
26104

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
52%
800
23%
2410
19%
799
57%
799
35%
1360
January16th to endNight
54%
768
26%
2496
24%
768
60%
768
38%
1345
February1st to 15thNight
48%
697
18%
2288
16%
696
53%
696
33%
1311
February16th to endNight
41%
632
28%
1911
16%
632
55%
632
37%
1050
March1st to 15thNight
51%
720
26%
2010
17%
720
58%
720
45%
1106
March16th to endNight
49%
744
24%
2088
17%
744
55%
744
38%
1211
April1st to 15thNight
45%
539
20%
1798
16%
539
52%
539
35%
976
April16th to endNight
48%
540
25%
1800
19%
540
58%
540
34%
971
May1st to 15thNight
56%
540
22%
1668
18%
540
61%
540
32%
962
May16th to endNight
59%
563
23%
1498
15%
561
66%
561
42%
843
June1st to 15thNight
68%
540
28%
1440
19%
540
74%
540
59%
713
June16th to endNight
79%
540
29%
1440
26%
540
81%
540
61%
695
July1st to 15thNight
77%
510
16%
1369
14%
510
78%
510
34%
844
July16th to endNight
80%
564
14%
1593
13%
531
81%
531
31%
965
August1st to 15thNight
77%
539
17%
1611
17%
536
77%
536
35%
926
August16th to endNight
78%
573
26%
1910
28%
573
79%
573
36%
1067
September1st to 15thNight
75%
540
25%
1800
26%
540
79%
540
35%
992
September16th to endNight
75%
629
36%
1965
30%
629
81%
629
52%
931
October1st to 15thNight
61%
720
30%
2160
21%
720
68%
720
48%
1088
October16th to endNight
66%
768
36%
2304
25%
768
72%
768
50%
1137
November1st to 15thNight
60%
799
31%
2199
22%
799
65%
799
49%
1146
November16th to endNight
56%
900
31%
2457
20%
900
62%
900
50%
1278
December1st to 15thNight
45%
900
16%
2520
10%
900
50%
900
37%
1466
December16th to endNight
45%
960
20%
2688
14%
960
49%
960
29%
1721

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
23245%35%6%7%10%48%
48331
Night
1324435%5%6%10%53%
47607
TransparencyDay
29%9%14%21%19%5%
48018
Night
23%8%16%25%20%5%
47423
SeeingDay
6%15%29%29%16%3
5858
Night
36%24%39%23%2
16036

By Month

Percentage Cloud Cover SW (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
225%6%5%8%7%9%14%37%
1537
16th to endDay
325%5%35%6%9%13%44%
1728
February1st to 15thDay
324426%7%10%16%39%
1575
16th to endDay
425%7%46%6%8%12%40%
1563
March1st to 15thDay
2145%36%5%7%12%50%
1947
16th to endDay
3245%35%6%7%11%49%
2135
April1st to 15thDay
1424435%5%7%11%48%
2150
16th to endDay
14244346%6%11%49%
2160
May1st to 15thDay
25%25%5%36%6%7%10%43%
2278
16th to endDay
23245%35%5%6%9%51%
2616
June1st to 15thDay
231342435%7%62%
2520
16th to endDay
111332445%8%63%
2520
July1st to 15thDay
4325%6%46%7%7%9%43%
2508
16th to endDay
5%436%7%47%7%8%10%35%
2467
August1st to 15thDay
6%5%26%6%45%7%6%10%38%
2338
16th to endDay
3315%7%36%7%7%9%44%
2292
September1st to 15thDay
4425%6%35%5%6%7%47%
2160
16th to endDay
4314422446%60%
1992
October1st to 15thDay
33134245%5%8%56%
1800
16th to endDay
132431445%7%60%
1918
November1st to 15thDay
12133245%5%11%58%
1648
16th to endDay
12133245%6%12%55%
1503
December1st to 15thDay
1416%6%35%7%9%11%41%
1440
16th to endDay
5%26%6%5%8%9%9%13%31%
1536
January1st to 15thNight
425%5%35%5%8%12%45%
2410
16th to endNight
14245%35%5%7%12%48%
2496
February1st to 15thNight
1326%5%36%5%8%11%44%
2277
16th to endNight
5%34425%5%6%9%51%
1911
March1st to 15thNight
313435%46%9%57%
2010
16th to endNight
1423435%46%8%54%
2088
April1st to 15thNight
14244345%6%11%50%
1798
16th to endNight
2424425%5%5%9%54%
1800
May1st to 15thNight
3425%5%26%46%8%51%
1667
16th to endNight
43133245%5%8%57%
1497
June1st to 15thNight
11222336%6%69%
1440
16th to endNight
1111445%8%68%
1440
July1st to 15thNight
23245%35%6%9%10%45%
1449
16th to endNight
22245%35%7%9%13%42%
1701
August1st to 15thNight
44134245%7%9%51%
1620
16th to endNight
33244345%6%9%51%
1910
September1st to 15thNight
3324435%5%6%8%50%
1800
16th to endNight
231231335%6%65%
1965
October1st to 15thNight
3313323348%62%
2160
16th to endNight
121332345%8%63%
2304
November1st to 15thNight
121232445%11%60%
2199
16th to endNight
132332346%12%56%
2457
December1st to 15thNight
1425%435%46%11%48%
2520
16th to endNight
438%7%46%6%8%10%38%
2688

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
28%10%23%24%11%1
1538
16th to endDay
26%7%20%28%14%2
1728
February1st to 15thDay
28%12%20%22%11%2
1575
16th to endDay
32%9%12%27%16%1
1563
March1st to 15thDay
26%8%17%28%17%1
1947
16th to endDay
30%8%13%26%16%3
2135
April1st to 15thDay
30%9%14%24%17%4
2150
16th to endDay
29%10%16%25%16%1
2160
May1st to 15thDay
33%10%12%23%17%1
2278
16th to endDay
28%9%13%22%22%4
2620
June1st to 15thDay
22%6%9%17%28%15%
2520
16th to endDay
18%6%7%14%31%20%
2520
July1st to 15thDay
34%12%13%12%15%12%
2360
16th to endDay
39%13%17%15%8%3
2312
August1st to 15thDay
39%12%12%12%14%7%
2323
16th to endDay
32%12%14%17%19%4
2292
September1st to 15thDay
33%10%11%13%22%8%
2160
16th to endDay
24%7%9%22%29%6%
1992
October1st to 15thDay
25%7%9%26%25%6%
1800
16th to endDay
22%6%10%29%25%5%
1918
November1st to 15thDay
20%6%12%25%28%6%
1648
16th to endDay
18%5%16%32%21%5%
1503
December1st to 15thDay
31%8%19%27%12%
1440
16th to endDay
34%11%21%20%10%1
1536
January1st to 15thNight
26%8%20%27%15%1
2410
16th to endNight
25%6%18%29%16%3
2496
February1st to 15thNight
29%8%21%25%13%2
2288
16th to endNight
25%7%15%29%19%2
1911
March1st to 15thNight
21%7%17%31%18%2
2010
16th to endNight
26%7%13%32%18%2
2088
April1st to 15thNight
25%8%17%23%21%3
1798
16th to endNight
25%8%13%30%19%3
1800
May1st to 15thNight
29%8%13%27%19%2
1668
16th to endNight
22%8%16%25%22%4
1498
June1st to 15thNight
12%7%11%20%29%19%
1440
16th to endNight
12%5%8%19%29%24%
1440
July1st to 15thNight
28%12%16%12%16%13%
1369
16th to endNight
25%15%25%17%9%6%
1593
August1st to 15thNight
23%13%18%18%16%9%
1611
16th to endNight
26%8%16%22%19%5%
1910
September1st to 15thNight
25%10%16%18%20%10%
1800
16th to endNight
16%5%10%26%35%4
1965
October1st to 15thNight
18%6%12%26%28%7%
2160
16th to endNight
17%6%10%30%29%5%
2304
November1st to 15thNight
19%5%14%27%27%5%
2199
16th to endNight
20%413%34%24%4
2457
December1st to 15thNight
27%7%23%25%15%
2520
16th to endNight
34%9%19%23%12%1
2688

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
6%15%18%31%23%4
90
16th to endDay
112%33%31%19%2
96
February1st to 15thDay
6%22%27%32%11%
90
16th to endDay
120%35%25%12%3
81
March1st to 15thDay
227%35%28%31
237
16th to endDay
6%34%39%15%4
288
April1st to 15thDay
8%30%32%18%7%2
269
16th to endDay
11%36%32%17%2
270
May1st to 15thDay
8%25%35%22%6%1
289
16th to endDay
415%28%30%17%3
517
June1st to 15thDay
412%29%28%21%3
495
16th to endDay
28%22%35%25%4
495
July1st to 15thDay
5%417%32%32%7%
464
16th to endDay
10%221%41%20%4
327
August1st to 15thDay
11%431%31%15%5%
315
16th to endDay
6%328%41%15%5%
332
September1st to 15thDay
9%6%37%26%14%5%
315
16th to endDay
413%37%27%12%4
243
October1st to 15thDay
9%11%22%28%18%8%
135
16th to endDay
6%13%20%33%20%6%
144
November1st to 15thDay
46%22%27%34%4
90
16th to endDay
6%21%37%22%12%
90
December1st to 15thDay
227%41%25%3
90
16th to endDay
318%26%41%9%1
96
January1st to 15thNight
29%26%41%17%2
804
16th to endNight
38%26%41%16%3
768
February1st to 15thNight
26%33%44%12%
704
16th to endNight
29%40%39%8%
632
March1st to 15thNight
25%36%40%13%1
720
16th to endNight
310%32%39%13%
744
April1st to 15thNight
38%39%37%10%
539
16th to endNight
411%32%37%13%1
540
May1st to 15thNight
45%27%44%16%
540
16th to endNight
6%6%23%36%24%2
563
June1st to 15thNight
1223%41%29%1
540
16th to endNight
115%42%37%2
540
July1st to 15thNight
35%33%52%3
510
16th to endNight
4426%56%7%
564
August1st to 15thNight
6%15%34%47%4
539
16th to endNight
47%32%46%8%
573
September1st to 15thNight
5%10%39%41%3
540
16th to endNight
4213%38%36%5%
629
October1st to 15thNight
2425%40%23%3
720
16th to endNight
1323%41%25%4
768
November1st to 15thNight
37%25%39%21%1
799
16th to endNight
310%26%38%19%2
900
December1st to 15thNight
311%33%38%10%1
900
16th to endNight
112%30%40%13%1
960
Page generated at 2017-11-01 15:23:35. Version ac04

Copyright 2017 A. Danko


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