Cheyenne
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cheyenne clear sky chart from 2005-11-05 to 2017-12-04.

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
39%
16338
26%
47833
12%
16294
51%
16294
35%
26947

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
24%
898
28%
2506
8%
895
41%
895
33%
1359
January16th to endNight
18%
856
30%
2584
8%
856
41%
856
31%
1376
February1st to 15thNight
20%
702
22%
2259
5%
698
39%
698
26%
1252
February16th to endNight
20%
632
27%
1894
7%
632
41%
632
29%
1104
March1st to 15thNight
28%
720
24%
2133
9%
720
42%
720
33%
1207
March16th to endNight
34%
669
23%
2013
11%
669
45%
669
29%
1187
April1st to 15thNight
30%
539
20%
1798
11%
539
46%
539
27%
1036
April16th to endNight
32%
540
21%
1800
12%
540
47%
540
24%
1093
May1st to 15thNight
42%
540
20%
1542
13%
540
48%
540
29%
966
May16th to endNight
46%
562
17%
1498
10%
561
51%
561
31%
958
June1st to 15thNight
55%
540
18%
1440
10%
540
60%
540
42%
833
June16th to endNight
62%
540
26%
1440
16%
540
67%
540
55%
736
July1st to 15thNight
70%
510
18%
1360
15%
510
71%
510
38%
815
July16th to endNight
73%
564
25%
1416
21%
531
74%
531
45%
792
August1st to 15thNight
67%
539
21%
1627
19%
536
71%
536
40%
886
August16th to endNight
70%
573
29%
1910
31%
573
74%
573
40%
995
September1st to 15thNight
61%
540
27%
1800
25%
540
70%
540
36%
971
September16th to endNight
59%
537
35%
1938
30%
537
70%
537
42%
914
October1st to 15thNight
43%
702
27%
2142
15%
702
53%
702
36%
1208
October16th to endNight
38%
830
34%
2366
14%
830
53%
830
41%
1269
November1st to 15thNight
35%
950
30%
2470
11%
950
47%
950
41%
1408
November16th to endNight
28%
975
32%
2633
8%
975
47%
975
41%
1448
December1st to 15thNight
21%
920
20%
2576
4%
920
36%
920
29%
1515
December16th to endNight
21%
960
25%
2688
6%
960
38%
960
28%
1619

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
6%5%2442445%8%49%
48680
Night
5%5%2442445%7%54%
48005
Cloud CoverDay
6%5%244345%5%8%49%
48678
Night
5%5%2442445%7%53%
48005
TransparencyDay
31%411%26%18%6%
48354
Night
29%412%28%19%5%
47833
SeeingDay
11%8%29%28%17%5%
6166
Night
8%11%35%31%11%1
16343

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
16%245%2335%8%55%
1432
16th to endDay
25%2341445%8%57%
1650
February1st to 15thDay
26%37%5%3446%9%47%
1603
16th to endDay
18%25%424447%53%
1580
March1st to 15thDay
45%24413348%55%
1825
16th to endDay
6%7%26%435%5%48%45%
2211
April1st to 15thDay
8%7%35%32445%8%46%
2150
16th to endDay
12%8%35%5%3446%7%38%
2160
May1st to 15thDay
16%7%25%425%45%7%39%
2405
16th to endDay
13%7%25%5%35%46%8%36%
2616
June1st to 15thDay
8%324435%6%6%9%45%
2520
16th to endDay
3212335%6%6%8%57%
2520
July1st to 15thDay
8%324435%6%6%8%45%
2520
16th to endDay
5%3235%46%6%8%10%45%
2656
August1st to 15thDay
7%3145%35%6%7%9%44%
2322
16th to endDay
5%3144345%6%7%52%
2292
September1st to 15thDay
9%31331435%7%54%
2160
16th to endDay
5%413323446%60%
2022
October1st to 15thDay
8%5%23323346%55%
1815
16th to endDay
6%423313246%62%
1845
November1st to 15thDay
35%15%334448%54%
1718
16th to endDay
23243245%6%8%55%
1656
December1st to 15thDay
45%35%6%2345%8%50%
1466
16th to endDay
36%36%6%3343452%
1536
January1st to 15thNight
242342445%6%59%
2506
16th to endNight
2425%423347%58%
2584
February1st to 15thNight
25%35%5%34449%52%
2249
16th to endNight
38%35%434445%53%
1894
March1st to 15thNight
36%25%43335%7%53%
2133
16th to endNight
6%6%23425%5%5%7%49%
2013
April1st to 15thNight
5%7%36%423348%49%
1798
16th to endNight
14%7%33324347%45%
1800
May1st to 15thNight
13%5%25%32447%8%43%
1541
16th to endNight
10%4245%25%47%8%44%
1497
June1st to 15thNight
7%2123246%7%9%51%
1440
16th to endNight
321231245%7%65%
1440
July1st to 15thNight
6%323445%5%6%9%49%
1440
16th to endNight
3212436%5%6%9%53%
1512
August1st to 15thNight
43144245%6%10%51%
1635
16th to endNight
5%31442445%6%56%
1910
September1st to 15thNight
10%31333235%6%54%
1800
16th to endNight
5%413312335%63%
1938
October1st to 15thNight
10%5%13323346%54%
2142
16th to endNight
6%5%13322346%60%
2366
November1st to 15thNight
45%2332445%8%57%
2470
16th to endNight
232331446%7%57%
2633
December1st to 15thNight
36%25%5%2445%7%51%
2576
16th to endNight
36%45%435%45%6%50%
2688

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%335%2336%8%55%
1432
16th to endDay
25%2342445%8%56%
1650
February1st to 15thDay
16%37%5%3345%9%46%
1603
16th to endDay
27%25%424447%53%
1580
March1st to 15thDay
35%2442345%8%55%
1825
16th to endDay
6%6%35%435%5%48%44%
2209
April1st to 15thDay
8%7%35%42445%8%45%
2150
16th to endDay
11%8%35%5%45%46%7%37%
2160
May1st to 15thDay
15%7%25%43445%7%39%
2405
16th to endDay
12%7%35%5%36%5%6%8%36%
2616
June1st to 15thDay
7%325%425%6%6%10%44%
2520
16th to endDay
3212335%5%6%7%58%
2520
July1st to 15thDay
7%414435%6%7%8%45%
2520
16th to endDay
42235%46%6%7%10%44%
2656
August1st to 15thDay
7%3145%45%6%7%9%43%
2322
16th to endDay
5%3244345%5%8%51%
2292
September1st to 15thDay
9%31342345%6%54%
2160
16th to endDay
5%412324346%60%
2022
October1st to 15thDay
8%5%13324347%54%
1815
16th to endDay
6%412312346%62%
1845
November1st to 15thDay
35%2442445%8%54%
1718
16th to endDay
23143245%7%9%55%
1656
December1st to 15thDay
45%36%5%2345%9%50%
1466
16th to endDay
36%36%6%3344452%
1536
January1st to 15thNight
24234235%5%6%58%
2506
16th to endNight
2425%423346%58%
2584
February1st to 15thNight
25%35%5%2435%9%52%
2249
16th to endNight
28%345%245%45%53%
1894
March1st to 15thNight
36%25%433447%53%
2133
16th to endNight
6%6%23426%5%5%7%49%
2013
April1st to 15thNight
5%8%26%5%24447%48%
1798
16th to endNight
13%7%24324346%45%
1800
May1st to 15thNight
12%5%2442437%8%42%
1541
16th to endNight
10%424425%5%5%9%44%
1497
June1st to 15thNight
6%2134247%7%9%50%
1440
16th to endNight
221231346%7%65%
1440
July1st to 15thNight
5%3235%35%5%6%10%48%
1440
16th to endNight
3212436%5%6%9%53%
1512
August1st to 15thNight
43143245%6%10%51%
1635
16th to endNight
5%314424447%56%
1910
September1st to 15thNight
10%31342345%6%54%
1800
16th to endNight
5%313312445%63%
1938
October1st to 15thNight
10%5%1332335%5%54%
2142
16th to endNight
6%5%13322346%59%
2366
November1st to 15thNight
442332445%7%57%
2470
16th to endNight
232342446%7%57%
2633
December1st to 15thNight
36%25%43445%7%52%
2576
16th to endNight
36%46%43446%6%50%
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
26%317%32%15%3
1433
16th to endDay
25%416%31%18%4
1650
February1st to 15thDay
32%5%16%32%9%3
1604
16th to endDay
30%313%32%16%4
1580
March1st to 15thDay
28%214%29%20%4
1825
16th to endDay
35%5%12%28%14%3
2211
April1st to 15thDay
35%412%27%14%6%
2150
16th to endDay
44%5%10%24%13%2
2160
May1st to 15thDay
43%411%24%14%1
2405
16th to endDay
43%7%12%22%12%2
2620
June1st to 15thDay
32%6%14%22%17%6%
2520
16th to endDay
22%5%9%25%24%13%
2520
July1st to 15thDay
33%6%10%20%15%13%
2371
16th to endDay
29%6%9%25%20%8%
2489
August1st to 15thDay
33%5%11%21%16%11%
2306
16th to endDay
27%5%8%23%24%10%
2292
September1st to 15thDay
28%46%23%25%11%
2160
16th to endDay
24%47%27%32%4
2022
October1st to 15thDay
30%48%24%25%6%
1815
16th to endDay
22%310%32%23%7%
1845
November1st to 15thDay
26%311%27%21%8%
1718
16th to endDay
23%411%32%24%4
1656
December1st to 15thDay
31%317%31%13%2
1466
16th to endDay
35%412%26%16%4
1536
January1st to 15thNight
25%317%29%19%4
2506
16th to endNight
25%312%31%20%5%
2584
February1st to 15thNight
30%5%17%31%13%2
2259
16th to endNight
32%310%28%19%4
1894
March1st to 15thNight
30%311%29%20%4
2133
16th to endNight
33%5%11%29%17%3
2013
April1st to 15thNight
34%413%28%15%3
1798
16th to endNight
39%49%27%17%2
1800
May1st to 15thNight
37%5%14%27%14%
1542
16th to endNight
36%6%18%22%12%3
1498
June1st to 15thNight
25%7%20%26%14%6%
1440
16th to endNight
17%5%11%30%23%12%
1440
July1st to 15thNight
30%5%11%24%16%10%
1360
16th to endNight
24%5%14%28%17%9%
1416
August1st to 15thNight
26%5%16%23%17%9%
1627
16th to endNight
26%48%26%23%10%
1910
September1st to 15thNight
29%39%22%20%13%
1800
16th to endNight
23%36%31%29%5%
1938
October1st to 15thNight
31%311%22%24%6%
2142
16th to endNight
25%310%27%24%8%
2366
November1st to 15thNight
25%410%26%24%8%
2470
16th to endNight
23%410%31%22%6%
2633
December1st to 15thNight
30%5%16%30%13%3
2576
16th to endNight
33%5%14%28%16%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
13%11%31%26%8%8%
90
16th to endDay
7%18%45%16%8%3
96
February1st to 15thDay
8%24%53%10%3
90
16th to endDay
7%20%39%23%6%2
81
March1st to 15thDay
6%22%42%18%8%
115
16th to endDay
15%14%43%22%3
288
April1st to 15thDay
13%20%40%15%7%1
269
16th to endDay
28%17%27%17%7%1
270
May1st to 15thDay
21%7%30%22%13%4
461
16th to endDay
18%6%25%26%17%5%
517
June1st to 15thDay
8%5%26%31%22%6%
495
16th to endDay
4228%38%19%6%
495
July1st to 15thDay
9%315%32%30%9%
475
16th to endDay
6%216%34%31%7%
515
August1st to 15thDay
10%222%38%22%3
340
16th to endDay
5%326%34%21%8%
332
September1st to 15thDay
11%426%36%15%4
315
16th to endDay
9%5%30%27%19%8%
177
October1st to 15thDay
14%5%28%31%14%5%
135
16th to endDay
9%13%40%21%9%4
144
November1st to 15thDay
5%5%40%24%17%7%
135
16th to endDay
13%17%47%17%4
135
December1st to 15thDay
8%28%42%19%3
100
16th to endDay
6%16%48%22%5%
96
January1st to 15thNight
5%25%40%19%7%2
900
16th to endNight
6%22%47%18%4
856
February1st to 15thNight
421%46%22%4
704
16th to endNight
7%18%47%23%2
632
March1st to 15thNight
5%14%46%24%7%
720
16th to endNight
9%12%40%29%7%
669
April1st to 15thNight
10%13%41%28%5%
539
16th to endNight
18%11%33%28%7%
540
May1st to 15thNight
15%7%29%33%11%1
540
16th to endNight
13%428%35%17%1
563
June1st to 15thNight
8%427%41%16%1
540
16th to endNight
3225%46%19%1
540
July1st to 15thNight
7%10%45%33%2
510
16th to endNight
3112%45%33%3
564
August1st to 15thNight
6%115%48%25%2
539
16th to endNight
6%113%47%27%3
573
September1st to 15thNight
10%318%38%24%5%
540
16th to endNight
7%324%42%19%3
537
October1st to 15thNight
12%7%32%32%13%2
702
16th to endNight
9%10%37%30%10%2
830
November1st to 15thNight
7%12%38%31%8%1
950
16th to endNight
5%14%47%27%41
975
December1st to 15thNight
7%20%44%21%41
920
16th to endNight
6%20%45%22%4
960
Page generated at 2017-12-05 08:18:59. Version ac04

Copyright 2017 A. Danko


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