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 2018-02-14.

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
61%
16519
25%
48837
19%
16479
66%
16479
39%
27333

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
55%
880
23%
2625
19%
879
60%
879
37%
1487
January16th to endNight
56%
832
28%
2704
25%
832
62%
832
35%
1502
February1st to 15thNight
50%
753
18%
2470
15%
752
56%
752
31%
1454
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%
539
17%
1620
17%
536
77%
536
34%
940
August16th to endNight
76%
573
25%
1910
26%
573
77%
573
34%
1085
September1st to 15thNight
75%
540
24%
1800
26%
540
79%
540
34%
1002
September16th to endNight
78%
618
35%
1959
31%
618
83%
618
51%
942
October1st to 15thNight
65%
720
30%
2160
22%
720
69%
720
47%
1109
October16th to endNight
67%
768
36%
2304
25%
768
73%
768
49%
1159
November1st to 15thNight
61%
880
31%
2400
21%
880
66%
880
49%
1275
November16th to endNight
57%
975
33%
2652
21%
975
64%
975
49%
1416
December1st to 15thNight
49%
975
16%
2730
11%
975
52%
975
37%
1614
December16th to endNight
47%
1040
20%
2912
14%
1040
51%
1040
28%
1912

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%51%
49248
Night
242442445%8%55%
49021
TransparencyDay
28%8%14%23%18%5%
48933
Night
25%8%15%26%19%4
48838
SeeingDay
6%11%26%32%18%4
6187
Night
4423%44%21%2
16530

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
325%7%36%6%8%11%44%
1653
16th to endDay
434425%5%6%10%51%
1872
February1st to 15thDay
424436%6%8%11%46%
1693
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%
2331
16th to endDay
3316%5%36%6%8%9%44%
2292
September1st to 15thDay
5%325%6%25%5%7%7%47%
2160
16th to endDay
5%313324336%61%
1998
October1st to 15thDay
332242346%7%58%
1800
16th to endDay
232432345%6%63%
1920
November1st to 15thDay
131241345%6%64%
1775
16th to endDay
122232446%7%63%
1638
December1st to 15thDay
425%6%36%48%10%46%
1560
16th to endDay
15%26%6%47%6%8%11%38%
1664
January1st to 15thNight
326%5%3446%10%51%
2625
16th to endNight
1426%5%345%5%7%53%
2704
February1st to 15thNight
426%6%35%5%6%10%48%
2459
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%
1629
16th to endNight
342443445%9%51%
1910
September1st to 15thNight
42145%345%7%8%51%
1800
16th to endNight
221321245%5%67%
1959
October1st to 15thNight
3313323247%64%
2160
16th to endNight
1213323347%64%
2304
November1st to 15thNight
2313323447%64%
2400
16th to endNight
131432245%6%63%
2652
December1st to 15thNight
16%34435%5%5%9%52%
2730
16th to endNight
16%37%7%36%6%6%8%42%
2912

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
30%7%24%25%10%1
1654
16th to endDay
27%7%19%30%13%2
1872
February1st to 15thDay
27%12%23%24%9%2
1693
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%11%12%15%15%7%
2316
16th to endDay
32%9%14%19%18%4
2292
September1st to 15thDay
32%8%13%15%21%8%
2160
16th to endDay
24%5%9%23%29%7%
1998
October1st to 15thDay
24%7%10%27%24%6%
1800
16th to endDay
22%5%12%30%24%5%
1920
November1st to 15thDay
20%5%13%26%27%6%
1775
16th to endDay
18%5%15%37%19%4
1638
December1st to 15thDay
29%9%19%28%12%1
1560
16th to endDay
35%10%18%23%10%1
1664
January1st to 15thNight
27%7%20%28%13%1
2625
16th to endNight
27%8%14%32%14%2
2704
February1st to 15thNight
29%10%21%25%11%1
2470
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%17%16%9%
1620
16th to endNight
28%8%17%21%18%5%
1910
September1st to 15thNight
28%8%17%16%19%10%
1800
16th to endNight
17%5%11%27%33%4
1959
October1st to 15thNight
21%5%11%28%26%6%
2160
16th to endNight
19%6%10%30%28%4
2304
November1st to 15thNight
21%5%12%29%26%4
2400
16th to endNight
20%6%10%35%23%3
2652
December1st to 15thNight
28%8%22%24%15%1
2730
16th to endNight
36%9%16%24%11%
2912

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
5%8%19%42%20%2
135
16th to endDay
5%24%43%22%4
144
February1st to 15thDay
316%28%35%16%
130
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%426%32%15%6%
315
16th to endDay
6%423%40%19%6%
332
September1st to 15thDay
9%431%32%13%8%
315
16th to endDay
411%33%28%16%5%
236
October1st to 15thDay
8%10%17%27%28%7%
135
16th to endDay
9%9%19%27%25%9%
144
November1st to 15thDay
48%22%29%25%9%
135
16th to endDay
8%13%26%31%18%
135
December1st to 15thDay
213%29%42%10%1
135
16th to endDay
412%22%44%13%2
144
January1st to 15thNight
1427%46%17%1
884
16th to endNight
3327%46%14%2
832
February1st to 15thNight
2333%49%10%
760
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
6%5%35%46%3
539
16th to endNight
6%5%35%43%7%
573
September1st to 15thNight
5%18%43%37%4
540
16th to endNight
2211%44%33%5%
618
October1st to 15thNight
5%321%45%22%2
720
16th to endNight
2221%46%22%3
768
November1st to 15thNight
4426%44%18%1
880
16th to endNight
45%27%42%17%1
975
December1st to 15thNight
5%6%33%44%10%1
975
16th to endNight
27%31%43%13%1
1040
Page generated at 2018-02-15 08:58:38. Version ac04

Copyright 2018 A. Danko


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