Stargate Colorado Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Stargate Colorado Observatory clear sky chart from 2005-11-05 to 2017-10-06.

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
47%
15872
29%
47080
16%
15830
59%
15830
40%
25068

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
50%
885
31%
2491
20%
880
60%
880
47%
1250
January16th to endNight
45%
768
36%
2496
22%
768
63%
768
45%
1170
February1st to 15thNight
38%
701
28%
2172
15%
700
52%
700
37%
1149
February16th to endNight
35%
632
38%
1894
15%
632
57%
632
42%
919
March1st to 15thNight
39%
720
30%
2128
14%
720
54%
720
40%
1128
March16th to endNight
34%
666
33%
2010
13%
666
53%
666
39%
1028
April1st to 15thNight
26%
539
28%
1798
11%
539
48%
539
33%
906
April16th to endNight
32%
540
24%
1800
12%
540
51%
540
29%
981
May1st to 15thNight
39%
540
24%
1703
15%
540
52%
540
31%
976
May16th to endNight
37%
561
24%
1551
11%
561
50%
561
36%
904
June1st to 15thNight
43%
540
24%
1440
11%
540
54%
540
44%
802
June16th to endNight
53%
540
22%
1440
13%
540
59%
540
40%
821
July1st to 15thNight
58%
510
17%
1360
12%
510
62%
510
31%
900
July16th to endNight
65%
564
17%
1501
15%
531
66%
531
32%
944
August1st to 15thNight
67%
539
11%
1749
10%
536
69%
536
25%
1113
August16th to endNight
61%
573
22%
1910
21%
573
65%
573
32%
1087
September1st to 15thNight
58%
540
25%
1800
18%
540
69%
540
34%
1005
September16th to endNight
54%
537
35%
1953
27%
537
68%
537
40%
926
October1st to 15thNight
46%
630
33%
1998
19%
630
59%
630
43%
986
October16th to endNight
58%
712
37%
2120
21%
712
68%
712
53%
1013
November1st to 15thNight
54%
875
38%
2275
18%
875
64%
875
59%
1101
November16th to endNight
51%
900
37%
2340
20%
900
60%
900
52%
1207
December1st to 15thNight
44%
900
29%
2463
13%
900
56%
900
47%
1291
December16th to endNight
43%
960
31%
2688
18%
960
53%
960
40%
1461

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
44234245%6%8%54%
48129
Night
341332345%7%58%
47260
Cloud CoverDay
44234245%6%8%54%
48127
Night
342332445%7%58%
47260
TransparencyDay
26%6%10%22%23%10%
47812
Night
24%5%11%24%24%10%
47080
SeeingDay
7%14%30%28%15%3
5783
Night
6%10%31%35%14%1
15877

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
231332125%6%67%
1458
16th to endDay
2422313345%66%
1728
February1st to 15thDay
2435%33335%7%58%
1690
16th to endDay
132332345%7%60%
1580
March1st to 15thDay
36%2332335%7%59%
1830
16th to endDay
45%2432346%8%53%
2214
April1st to 15thDay
45%1432436%7%55%
2150
16th to endDay
6%5%2432445%8%52%
2160
May1st to 15thDay
6%5%234246%5%7%49%
2247
16th to endDay
43134245%7%8%52%
2560
June1st to 15thDay
3312335%7%7%8%51%
2520
16th to endDay
2113426%7%8%9%53%
2520
July1st to 15thDay
5%3145%38%7%9%10%40%
2520
16th to endDay
5%3136%47%9%9%10%37%
2561
August1st to 15thDay
6%325%6%38%8%7%9%38%
2202
16th to endDay
6%3245%36%7%6%10%42%
2292
September1st to 15thDay
6%414435%5%7%9%46%
2160
16th to endDay
321332335%6%63%
2007
October1st to 15thDay
4212424347%61%
1756
16th to endDay
331112335%72%
1741
November1st to 15thDay
121221335%6%68%
1583
16th to endDay
2413313326%67%
1620
December1st to 15thDay
1434222349%62%
1494
16th to endDay
25%234335%6%7%55%
1536
January1st to 15thNight
1324313345%66%
2491
16th to endNight
2423223435%66%
2496
February1st to 15thNight
16%25%323346%59%
2162
16th to endNight
1414312345%67%
1894
March1st to 15thNight
25%23323447%59%
2128
16th to endNight
4222324346%63%
2010
April1st to 15thNight
35%1332345%7%58%
1798
16th to endNight
7%5%14323446%55%
1800
May1st to 15thNight
8%5%23323447%53%
1702
16th to endNight
5%41332446%7%56%
1550
June1st to 15thNight
331231446%8%58%
1440
16th to endNight
2313425%5%8%11%51%
1440
July1st to 15thNight
5%4235%47%7%8%11%39%
1440
16th to endNight
5%324435%6%8%12%42%
1604
August1st to 15thNight
5%2145%47%9%9%10%39%
1758
16th to endNight
5%3234345%9%10%46%
1910
September1st to 15thNight
5%324425%5%6%12%47%
1800
16th to endNight
331332235%6%64%
1953
October1st to 15thNight
4312312346%65%
1998
16th to endNight
3313212345%68%
2120
November1st to 15thNight
1113112347%71%
2275
16th to endNight
2312223346%66%
2340
December1st to 15thNight
232331436%8%60%
2463
16th to endNight
36%24324346%59%
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
232231225%6%67%
1458
16th to endDay
1422313345%66%
1728
February1st to 15thDay
25%35%33335%7%57%
1690
16th to endDay
13233245%5%7%60%
1580
March1st to 15thDay
26%33322346%59%
1830
16th to endDay
45%2432346%8%53%
2212
April1st to 15thDay
45%1432436%7%55%
2150
16th to endDay
6%5%25%32445%8%52%
2160
May1st to 15thDay
6%5%33425%5%6%7%48%
2247
16th to endDay
44134245%7%9%52%
2560
June1st to 15thDay
3313336%8%7%8%51%
2520
16th to endDay
2113426%7%8%9%52%
2520
July1st to 15thDay
5%3145%47%7%8%10%40%
2520
16th to endDay
5%3146%47%8%9%11%36%
2561
August1st to 15thDay
6%325%6%38%8%7%10%38%
2202
16th to endDay
6%315%5%36%6%6%10%42%
2292
September1st to 15thDay
6%414435%5%7%8%46%
2160
16th to endDay
321432345%6%63%
2007
October1st to 15thDay
4212433347%62%
1756
16th to endDay
331222235%71%
1741
November1st to 15thDay
1213213347%67%
1583
16th to endDay
2413313336%67%
1620
December1st to 15thDay
15%2421325%8%62%
1494
16th to endDay
25%2343346%7%55%
1536
January1st to 15thNight
1323313345%66%
2491
16th to endNight
2423213436%65%
2496
February1st to 15thNight
16%25%32335%5%58%
2162
16th to endNight
1423312345%66%
1894
March1st to 15thNight
25%2432345%6%59%
2128
16th to endNight
4322314346%63%
2010
April1st to 15thNight
45%1332436%7%58%
1798
16th to endNight
7%5%14323446%55%
1800
May1st to 15thNight
8%6%23314447%52%
1702
16th to endNight
5%32432445%8%55%
1550
June1st to 15thNight
3312315%5%6%8%58%
1440
16th to endNight
2413425%5%8%10%51%
1440
July1st to 15thNight
5%424447%6%8%11%39%
1440
16th to endNight
5%324435%6%8%12%42%
1604
August1st to 15thNight
4315%447%10%8%10%38%
1758
16th to endNight
5%423435%5%9%10%46%
1910
September1st to 15thNight
5%324425%5%7%11%47%
1800
16th to endNight
331232235%6%63%
1953
October1st to 15thNight
4312312346%65%
1998
16th to endNight
3312212345%68%
2120
November1st to 15thNight
1113112347%70%
2275
16th to endNight
2413223446%66%
2340
December1st to 15thNight
232431436%8%60%
2463
16th to endNight
36%24323446%58%
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
19%29%28%33%7%
1459
16th to endDay
20%28%25%31%10%
1728
February1st to 15thDay
27%39%26%24%9%
1691
16th to endDay
21%47%25%29%12%
1580
March1st to 15thDay
24%38%22%29%11%
1830
16th to endDay
27%5%9%23%25%8%
2214
April1st to 15thDay
27%48%25%23%11%
2150
16th to endDay
29%5%10%23%22%8%
2160
May1st to 15thDay
32%7%12%18%22%7%
2247
16th to endDay
26%8%11%19%19%13%
2564
June1st to 15thDay
24%9%13%16%18%17%
2520
16th to endDay
23%7%10%20%20%17%
2520
July1st to 15thDay
33%10%13%19%13%10%
2371
16th to endDay
33%13%17%21%12%2
2402
August1st to 15thDay
36%12%17%16%11%5%
2187
16th to endDay
35%7%11%21%18%5%
2292
September1st to 15thDay
32%7%12%24%15%7%
2160
16th to endDay
20%5%9%22%29%13%
2007
October1st to 15thDay
22%5%8%20%31%11%
1756
16th to endDay
14%37%24%36%13%
1741
November1st to 15thDay
15%38%23%31%16%
1583
16th to endDay
18%35%20%35%16%
1620
December1st to 15thDay
22%313%27%24%8%
1494
16th to endDay
25%5%12%26%22%7%
1536
January1st to 15thNight
19%38%31%28%8%
2491
16th to endNight
20%28%25%32%10%
2496
February1st to 15thNight
27%310%29%22%6%
2172
16th to endNight
19%27%26%31%12%
1894
March1st to 15thNight
24%39%23%31%7%
2128
16th to endNight
22%49%23%29%10%
2010
April1st to 15thNight
24%48%28%22%11%
1798
16th to endNight
30%413%20%21%8%
1800
May1st to 15thNight
30%6%10%21%22%8%
1703
16th to endNight
26%7%13%20%17%14%
1551
June1st to 15thNight
20%7%13%22%16%18%
1440
16th to endNight
25%7%13%17%19%16%
1440
July1st to 15thNight
35%9%14%18%12%8%
1360
16th to endNight
32%10%22%23%8%1
1501
August1st to 15thNight
34%12%23%14%9%5%
1749
16th to endNight
28%9%16%26%14%4
1910
September1st to 15thNight
29%6%18%26%12%5%
1800
16th to endNight
21%5%8%22%29%12%
1953
October1st to 15thNight
21%410%19%33%10%
1998
16th to endNight
17%37%21%34%14%
2120
November1st to 15thNight
13%29%26%30%16%
2275
16th to endNight
18%27%24%31%15%
2340
December1st to 15thNight
22%312%29%26%6%
2463
16th to endNight
25%312%24%25%8%
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%14%32%28%16%
90
16th to endDay
6%18%29%26%14%5%
96
February1st to 15thDay
221%38%26%11%
90
16th to endDay
9%22%28%28%9%1
81
March1st to 15thDay
8%19%40%26%31
120
16th to endDay
14%32%33%13%41
288
April1st to 15thDay
13%32%35%12%41
269
16th to endDay
13%35%35%14%1
270
May1st to 15thDay
10%23%34%21%8%1
384
16th to endDay
9%15%35%26%11%1
517
June1st to 15thDay
5%13%28%26%20%4
495
16th to endDay
3431%31%26%3
495
July1st to 15thDay
6%322%34%27%5%
475
16th to endDay
5%215%38%28%10%
420
August1st to 15thDay
7%326%39%17%6%
315
16th to endDay
7%426%41%16%2
332
September1st to 15thDay
7%6%35%29%13%6%
315
16th to endDay
9%14%32%24%17%1
162
October1st to 15thDay
318%27%29%14%6%
107
16th to endDay
7%13%28%27%18%5%
96
November1st to 15thDay
214%22%28%26%5%
90
16th to endDay
15%14%41%18%10%
90
December1st to 15thDay
26%43%23%6%
90
16th to endDay
8%23%30%34%3
96
January1st to 15thNight
411%28%38%13%2
885
16th to endNight
5%10%35%36%10%1
768
February1st to 15thNight
5%13%39%32%9%
704
16th to endNight
5%20%36%32%5%
632
March1st to 15thNight
7%14%34%35%8%
720
16th to endNight
7%17%39%28%7%
666
April1st to 15thNight
7%20%44%23%3
539
16th to endNight
12%16%34%29%6%
540
May1st to 15thNight
10%12%32%34%8%
540
16th to endNight
8%10%38%30%10%1
563
June1st to 15thNight
6%6%39%32%14%1
540
16th to endNight
3432%40%17%1
540
July1st to 15thNight
5%322%38%28%2
510
16th to endNight
6%117%37%32%4
564
August1st to 15thNight
5%118%32%36%5%
539
16th to endNight
5%121%34%31%3
573
September1st to 15thNight
7%5%22%39%22%2
540
16th to endNight
48%29%34%19%2
537
October1st to 15thNight
7%11%31%32%14%2
630
16th to endNight
4428%41%16%4
712
November1st to 15thNight
310%29%38%16%1
875
16th to endNight
5%10%31%36%13%3
900
December1st to 15thNight
411%38%36%8%1
900
16th to endNight
7%13%32%36%9%1
960
Page generated at 2017-10-07 12:07:50. Version ac04

Copyright 2017 A. Danko


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