Great Sand Dunes National Park and Preserve
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Great Sand Dunes National Park and Preserve clear sky chart from 2005-11-05 to 2017-12-20.

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
41%
16256
26%
48063
13%
16211
53%
16211
35%
26612

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
36%
861
27%
2467
14%
856
50%
856
43%
1271
January16th to endNight
36%
768
31%
2496
18%
768
52%
768
39%
1239
February1st to 15thNight
26%
702
23%
2229
10%
700
41%
700
33%
1202
February16th to endNight
19%
632
32%
1894
9%
632
43%
632
35%
1007
March1st to 15thNight
31%
720
26%
2085
9%
720
45%
720
35%
1144
March16th to endNight
30%
695
28%
2039
11%
695
46%
695
34%
1114
April1st to 15thNight
25%
539
23%
1798
8%
539
43%
539
25%
982
April16th to endNight
29%
540
24%
1800
10%
540
47%
540
24%
994
May1st to 15thNight
31%
540
19%
1711
9%
540
45%
540
25%
1015
May16th to endNight
35%
563
21%
1497
8%
561
47%
561
29%
890
June1st to 15thNight
45%
540
25%
1440
13%
540
55%
540
42%
778
June16th to endNight
59%
540
23%
1440
15%
540
65%
540
41%
802
July1st to 15thNight
59%
510
14%
1360
10%
510
61%
510
26%
924
July16th to endNight
72%
564
13%
1528
13%
531
73%
531
23%
1052
August1st to 15thNight
66%
539
12%
1691
12%
536
67%
536
23%
1102
August16th to endNight
65%
573
18%
1910
19%
573
68%
573
26%
1183
September1st to 15thNight
57%
540
22%
1800
17%
540
66%
540
27%
1100
September16th to endNight
54%
537
34%
1923
26%
537
68%
537
39%
911
October1st to 15thNight
43%
720
31%
2160
16%
720
56%
720
39%
1128
October16th to endNight
47%
768
38%
2304
19%
768
62%
768
45%
1135
November1st to 15thNight
41%
931
34%
2451
14%
931
53%
931
49%
1233
November16th to endNight
40%
975
36%
2555
16%
975
55%
975
47%
1338
December1st to 15thNight
30%
975
23%
2730
8%
975
43%
975
39%
1494
December16th to endNight
28%
984
26%
2755
11%
984
41%
984
33%
1574

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
3424435%5%6%8%51%
48783
Night
242442445%7%56%
48247
TransparencyDay
28%7%14%24%19%5%
48468
Night
25%7%14%26%21%5%
48064
SeeingDay
11%20%31%23%10%1
6022
Night
6%15%33%28%14%2
16258

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%42345%8%59%
1480
16th to endDay
42431235%7%61%
1728
February1st to 15thDay
1336%42435%8%55%
1631
16th to endDay
5%344245%5%8%55%
1580
March1st to 15thDay
15%46%42445%9%52%
1872
16th to endDay
26%26%435%45%7%51%
2184
April1st to 15thDay
26%35%5%35%45%9%49%
2150
16th to endDay
48%346%346%5%8%44%
2160
May1st to 15thDay
5%6%36%5%36%5%6%7%41%
2238
16th to endDay
4425%5%25%5%6%7%51%
2616
June1st to 15thDay
3313425%5%7%9%52%
2520
16th to endDay
1212425%5%7%9%56%
2520
July1st to 15thDay
5%325%6%48%7%8%9%38%
2520
16th to endDay
4435%6%48%8%10%10%33%
2532
August1st to 15thDay
6%426%5%47%7%9%8%36%
2259
16th to endDay
5%5%15%5%37%5%8%9%41%
2292
September1st to 15thDay
5%425%5%35%7%7%8%46%
2160
16th to endDay
22134245%45%62%
2034
October1st to 15thDay
3423423446%60%
1800
16th to endDay
2213413336%66%
1920
November1st to 15thDay
323223249%64%
1724
16th to endDay
1323223347%64%
1735
December1st to 15thDay
5%1431335%8%60%
1560
16th to endDay
1425%42446%11%51%
1568
January1st to 15thNight
313423446%65%
2467
16th to endNight
323423447%62%
2496
February1st to 15thNight
15%36%313346%58%
2219
16th to endNight
425%42335%8%58%
1894
March1st to 15thNight
15%2441345%9%57%
2085
16th to endNight
26%24413347%59%
2039
April1st to 15thNight
15%2443445%7%55%
1798
16th to endNight
27%24335%5%5%8%50%
1800
May1st to 15thNight
46%25%5%36%6%46%48%
1710
16th to endNight
44134346%6%9%51%
1497
June1st to 15thNight
23325%5%5%8%60%
1440
16th to endNight
1212326%7%8%7%55%
1440
July1st to 15thNight
4446%7%36%6%7%9%37%
1440
16th to endNight
43246%5%9%8%9%8%36%
1634
August1st to 15thNight
3427%7%46%6%7%8%40%
1700
16th to endNight
5%325%5%37%9%8%9%39%
1910
September1st to 15thNight
5%415%5%37%6%7%9%44%
1800
16th to endNight
231332345%6%62%
1923
October1st to 15thNight
3312323447%63%
2160
16th to endNight
231321335%6%66%
2304
November1st to 15thNight
111122335%7%67%
2451
16th to endNight
1213323348%65%
2555
December1st to 15thNight
1324423347%60%
2730
16th to endNight
1315%435%45%8%56%
2755

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
22%5%21%29%18%2
1481
16th to endDay
21%5%16%33%17%4
1728
February1st to 15thDay
26%6%18%31%12%4
1632
16th to endDay
24%6%13%28%22%4
1580
March1st to 15thDay
28%414%24%23%4
1872
16th to endDay
30%5%11%29%19%2
2184
April1st to 15thDay
32%6%12%26%18%4
2150
16th to endDay
34%8%12%21%19%3
2160
May1st to 15thDay
38%7%13%21%16%2
2238
16th to endDay
29%8%13%21%19%6%
2620
June1st to 15thDay
25%7%14%17%21%13%
2520
16th to endDay
19%7%11%23%24%13%
2520
July1st to 15thDay
36%10%14%17%13%6%
2371
16th to endDay
36%15%20%19%6%
2375
August1st to 15thDay
38%12%15%15%12%5%
2244
16th to endDay
34%9%14%23%16%2
2292
September1st to 15thDay
31%10%13%21%17%5%
2160
16th to endDay
21%6%10%23%33%4
2034
October1st to 15thDay
25%48%26%28%6%
1800
16th to endDay
20%410%29%30%4
1920
November1st to 15thDay
18%412%25%31%6%
1724
16th to endDay
18%411%32%25%6%
1735
December1st to 15thDay
21%5%22%28%17%4
1560
16th to endDay
25%10%21%25%14%2
1568
January1st to 15thNight
20%5%19%29%22%2
2467
16th to endNight
20%6%13%34%20%4
2496
February1st to 15thNight
27%5%18%29%16%2
2229
16th to endNight
24%5%12%29%23%3
1894
March1st to 15thNight
23%6%14%28%24%2
2085
16th to endNight
25%5%11%30%25%2
2039
April1st to 15thNight
27%7%12%26%20%4
1798
16th to endNight
30%6%14%27%19%2
1800
May1st to 15thNight
32%7%13%24%16%4
1711
16th to endNight
27%8%16%22%16%8%
1498
June1st to 15thNight
20%7%14%20%20%17%
1440
16th to endNight
20%9%13%20%21%13%
1440
July1st to 15thNight
38%10%15%15%10%8%
1360
16th to endNight
36%16%19%20%7%1
1528
August1st to 15thNight
35%13%19%15%10%5%
1691
16th to endNight
33%11%18%19%12%3
1910
September1st to 15thNight
32%10%16%21%12%6%
1800
16th to endNight
20%6%10%25%31%5%
1923
October1st to 15thNight
20%6%10%24%29%7%
2160
16th to endNight
18%47%29%32%6%
2304
November1st to 15thNight
15%412%29%31%6%
2451
16th to endNight
19%310%30%29%6%
2555
December1st to 15thNight
22%6%19%27%19%3
2730
16th to endNight
24%8%19%26%18%3
2755

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
11%28%32%17%10%
90
16th to endDay
7%27%33%23%8%
96
February1st to 15thDay
10%36%33%18%1
90
16th to endDay
11%34%30%18%4
81
March1st to 15thDay
15%29%32%19%3
162
16th to endDay
23%32%33%7%2
288
April1st to 15thDay
18%37%27%12%2
269
16th to endDay
22%44%24%7%1
270
May1st to 15thDay
12%29%35%17%31
357
16th to endDay
9%24%32%21%11%1
517
June1st to 15thDay
8%17%29%25%17%2
495
16th to endDay
5%9%31%29%21%3
495
July1st to 15thDay
10%6%27%32%18%4
475
16th to endDay
9%326%38%17%3
391
August1st to 15thDay
13%6%33%33%12%
315
16th to endDay
10%7%35%34%9%1
332
September1st to 15thDay
9%17%37%24%9%1
315
16th to endDay
6%20%40%21%8%2
192
October1st to 15thDay
13%24%26%23%8%2
135
16th to endDay
6%25%29%25%9%2
144
November1st to 15thDay
10%21%29%24%12%1
135
16th to endDay
11%37%28%17%4
135
December1st to 15thDay
8%35%34%14%5%1
135
16th to endDay
11%36%32%14%4
108
January1st to 15thNight
415%40%26%10%2
861
16th to endNight
416%40%28%8%1
768
February1st to 15thNight
416%49%24%5%
704
16th to endNight
6%20%50%18%4
632
March1st to 15thNight
6%20%37%27%7%
720
16th to endNight
9%19%39%23%8%
695
April1st to 15thNight
10%23%36%24%4
539
16th to endNight
8%25%35%23%6%
540
May1st to 15thNight
7%19%36%25%9%1
540
16th to endNight
8%19%32%24%13%1
563
June1st to 15thNight
312%32%32%16%2
540
16th to endNight
28%24%37%24%2
540
July1st to 15thNight
8%316%32%32%5%
510
16th to endNight
5%29%32%43%7%
564
August1st to 15thNight
7%311%37%34%6%
539
16th to endNight
7%115%38%32%5%
573
September1st to 15thNight
7%6%21%35%23%5%
540
16th to endNight
411%25%35%19%2
537
October1st to 15thNight
5%16%30%30%13%2
720
16th to endNight
413%31%30%17%2
768
November1st to 15thNight
5%17%33%29%12%
931
16th to endNight
6%16%34%29%10%1
975
December1st to 15thNight
6%19%41%25%6%
975
16th to endNight
5%23%38%24%8%
984
Page generated at 2017-12-21 05:04:54. Version ac04

Copyright 2017 A. Danko


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