Gunnison Valley Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Gunnison Valley Observatory clear sky chart from 2005-11-05 to 2017-08-12.

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
60%
15751
24%
46534
19%
15711
65%
15711
39%
26272

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
54%
812
22%
2422
19%
811
58%
811
36%
1396
January16th to endNight
54%
768
26%
2496
23%
768
60%
768
33%
1422
February1st to 15thNight
50%
697
17%
2288
14%
696
55%
696
30%
1376
February16th to endNight
47%
632
28%
1902
18%
632
58%
632
36%
1092
March1st to 15thNight
55%
720
25%
2022
17%
720
61%
720
45%
1116
March16th to endNight
53%
738
25%
2082
17%
738
59%
738
40%
1208
April1st to 15thNight
50%
539
20%
1798
16%
539
57%
539
34%
990
April16th to endNight
52%
540
25%
1800
20%
540
60%
540
35%
987
May1st to 15thNight
58%
540
21%
1664
18%
540
63%
540
33%
966
May16th to endNight
62%
563
22%
1497
15%
561
68%
561
43%
848
June1st to 15thNight
72%
540
28%
1440
21%
540
76%
540
59%
717
June16th to endNight
80%
540
29%
1440
26%
540
82%
540
63%
698
July1st to 15thNight
76%
510
16%
1360
14%
510
76%
510
33%
848
July16th to endNight
79%
564
15%
1586
14%
531
80%
531
31%
966
August1st to 15thNight
76%
527
17%
1583
17%
524
77%
524
34%
925
August16th to endNight
76%
525
22%
1750
24%
525
77%
525
33%
1002
September1st to 15thNight
74%
495
26%
1650
27%
495
78%
495
33%
926
September16th to endNight
79%
566
33%
1795
30%
566
82%
566
51%
860
October1st to 15thNight
64%
660
30%
1980
23%
660
69%
660
46%
1029
October16th to endNight
65%
704
33%
2112
23%
704
72%
704
47%
1082
November1st to 15thNight
62%
811
31%
2211
21%
811
67%
811
49%
1175
November16th to endNight
56%
900
31%
2448
20%
900
63%
900
48%
1325
December1st to 15thNight
47%
900
15%
2520
10%
900
50%
900
35%
1523
December16th to endNight
46%
960
19%
2688
12%
960
51%
960
27%
1795

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%5%7%9%50%
47448
Night
242442445%8%54%
46718
TransparencyDay
29%8%14%23%18%5%
47133
Night
25%8%15%26%19%4
46535
SeeingDay
6%11%26%32%18%4
5586
Night
4423%43%21%2
15762

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
326%7%46%6%8%12%42%
1525
16th to endDay
434425%6%7%10%48%
1728
February1st to 15thDay
324436%7%9%12%44%
1575
16th to endDay
436%7%45%5%7%11%44%
1572
March1st to 15thDay
1313335%5%6%10%54%
1937
16th to endDay
13235%26%6%6%9%51%
2142
April1st to 15thDay
14244345%7%9%51%
2150
16th to endDay
2415%436%47%10%48%
2160
May1st to 15thDay
24245%45%7%7%9%45%
2282
16th to endDay
23135%35%5%7%8%53%
2616
June1st to 15thDay
231331346%7%61%
2520
16th to endDay
11232445%8%63%
2520
July1st to 15thDay
4325%5%36%6%8%9%43%
2520
16th to endDay
4426%6%47%6%8%10%36%
2473
August1st to 15thDay
6%5%25%6%45%6%7%8%41%
2282
16th to endDay
3326%5%46%6%8%9%44%
2100
September1st to 15thDay
5%316%6%25%5%6%7%47%
1980
16th to endDay
5%313324336%62%
1832
October1st to 15thDay
332242346%8%57%
1650
16th to endDay
232432345%6%62%
1760
November1st to 15thDay
131241345%7%63%
1636
16th to endDay
122332446%7%62%
1512
December1st to 15thDay
1425%6%36%5%9%10%43%
1440
16th to endDay
16%27%6%48%6%9%11%36%
1536
January1st to 15thNight
326%5%35%5%6%10%49%
2422
16th to endNight
1426%5%345%6%7%51%
2496
February1st to 15thNight
426%6%36%5%6%11%46%
2277
16th to endNight
6%343335%6%10%50%
1902
March1st to 15thNight
414324449%59%
2022
16th to endNight
1424425%46%8%55%
2082
April1st to 15thNight
25%244245%6%8%53%
1798
16th to endNight
25%25%32445%8%54%
1800
May1st to 15thNight
26%24425%36%9%51%
1663
16th to endNight
5%31232446%9%57%
1497
June1st to 15thNight
1122235%7%70%
1440
16th to endNight
1224448%69%
1440
July1st to 15thNight
3325%5%35%5%7%10%48%
1440
16th to endNight
3324435%6%8%13%45%
1693
August1st to 15thNight
4315%3245%6%9%51%
1592
16th to endNight
3424435%45%9%51%
1750
September1st to 15thNight
5%2145%345%7%8%50%
1650
16th to endNight
2213213445%67%
1795
October1st to 15thNight
3313324247%62%
1980
16th to endNight
1214423348%63%
2112
November1st to 15thNight
2313314447%64%
2211
16th to endNight
131432345%6%63%
2448
December1st to 15thNight
16%34435%5%5%10%49%
2520
16th to endNight
16%37%7%36%6%6%8%40%
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
31%8%25%24%10%
1526
16th to endDay
29%8%19%28%12%2
1728
February1st to 15thDay
28%13%21%24%9%2
1575
16th to endDay
33%8%13%28%15%1
1572
March1st to 15thDay
26%6%18%31%16%1
1937
16th to endDay
30%7%15%27%15%3
2142
April1st to 15thDay
30%7%14%25%18%4
2150
16th to endDay
29%8%16%25%17%1
2160
May1st to 15thDay
32%10%13%24%17%1
2282
16th to endDay
26%8%14%23%21%4
2620
June1st to 15thDay
21%6%10%18%27%15%
2520
16th to endDay
18%5%9%16%29%20%
2520
July1st to 15thDay
33%10%14%13%15%12%
2371
16th to endDay
38%11%19%17%9%4
2317
August1st to 15thDay
39%10%11%14%15%7%
2267
16th to endDay
33%10%14%19%17%5%
2100
September1st to 15thDay
34%7%12%14%21%8%
1980
16th to endDay
24%5%9%23%30%6%
1832
October1st to 15thDay
25%7%10%28%23%4
1650
16th to endDay
23%5%12%29%24%4
1760
November1st to 15thDay
21%5%14%25%27%6%
1636
16th to endDay
19%5%15%35%18%4
1512
December1st to 15thDay
31%10%19%28%9%
1440
16th to endDay
36%11%19%22%9%1
1536
January1st to 15thNight
28%7%21%27%13%
2422
16th to endNight
28%8%14%30%13%2
2496
February1st to 15thNight
30%11%19%25%11%1
2288
16th to endNight
28%7%13%30%17%1
1902
March1st to 15thNight
22%7%18%33%16%1
2022
16th to endNight
26%7%12%33%17%1
2082
April1st to 15thNight
26%8%15%24%20%3
1798
16th to endNight
25%9%13%29%19%2
1800
May1st to 15thNight
29%9%15%26%18%2
1664
16th to endNight
22%8%16%26%20%4
1498
June1st to 15thNight
13%6%11%22%27%18%
1440
16th to endNight
13%410%19%28%23%
1440
July1st to 15thNight
29%11%17%12%15%13%
1360
16th to endNight
26%15%24%17%10%6%
1586
August1st to 15thNight
25%12%19%16%16%9%
1583
16th to endNight
29%8%17%20%17%6%
1750
September1st to 15thNight
28%8%16%15%20%10%
1650
16th to endNight
17%5%11%27%34%4
1795
October1st to 15thNight
21%5%12%29%25%5%
1980
16th to endNight
20%6%10%31%28%3
2112
November1st to 15thNight
21%5%13%29%25%4
2211
16th to endNight
21%6%10%35%23%3
2448
December1st to 15thNight
29%9%22%24%13%
2520
16th to endNight
37%10%17%22%10%
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
7%10%14%40%23%4
90
16th to endDay
1427%41%21%4
96
February1st to 15thDay
410%30%38%16%
90
16th to endDay
9%29%37%17%6%
81
March1st to 15thDay
5%13%33%33%13%1
227
16th to endDay
6%23%34%27%6%1
288
April1st to 15thDay
8%24%31%21%10%2
269
16th to endDay
9%28%36%19%4
270
May1st to 15thDay
6%22%34%25%9%1
303
16th to endDay
5%11%27%33%18%4
517
June1st to 15thDay
410%26%31%22%4
495
16th to endDay
16%22%34%28%5%
495
July1st to 15thDay
5%413%32%35%9%
475
16th to endDay
10%118%40%19%8%
332
August1st to 15thDay
14%427%32%15%6%
300
16th to endDay
5%424%44%16%3
268
September1st to 15thDay
10%5%35%33%11%3
255
16th to endDay
6%8%30%30%19%6%
183
October1st to 15thDay
5%7%15%26%34%10%
90
16th to endDay
13%7%15%28%26%9%
96
November1st to 15thDay
3415%31%32%13%
90
16th to endDay
8%16%28%28%16%
90
December1st to 15thDay
315%34%41%5%
90
16th to endDay
5%10%18%51%12%2
96
January1st to 15thNight
15%28%45%17%1
816
16th to endNight
4428%45%14%2
768
February1st to 15thNight
2332%49%10%
704
16th to endNight
36%36%44%8%
632
March1st to 15thNight
2333%48%11%1
720
16th to endNight
25%33%45%12%
738
April1st to 15thNight
46%34%44%10%
539
16th to endNight
5%6%32%42%12%
540
May1st to 15thNight
5%5%26%45%16%
540
16th to endNight
7%320%42%22%2
563
June1st to 15thNight
1220%46%27%
540
16th to endNight
1113%48%34%1
540
July1st to 15thNight
5%5%38%46%3
510
16th to endNight
41330%54%5%
564
August1st to 15thNight
7%5%35%46%3
527
16th to endNight
6%5%36%43%7%
525
September1st to 15thNight
5%18%46%35%2
495
16th to endNight
329%42%35%5%
566
October1st to 15thNight
5%321%44%23%2
660
16th to endNight
2221%45%22%3
704
November1st to 15thNight
45%25%44%19%1
811
16th to endNight
46%28%42%17%2
900
December1st to 15thNight
5%6%35%42%9%1
900
16th to endNight
27%31%43%13%1
960
Page generated at 2017-08-13 12:16:25. Version ac04

Copyright 2017 A. Danko


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