Broomfield
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Broomfield 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
54%
15837
27%
46504
18%
15796
63%
15796
42%
25265

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
43%
897
31%
2506
16%
895
58%
895
49%
1320
January16th to endNight
39%
815
33%
2543
19%
815
56%
815
41%
1333
February1st to 15thNight
35%
699
25%
2248
12%
698
51%
698
36%
1235
February16th to endNight
37%
632
31%
1894
14%
632
55%
632
39%
1048
March1st to 15thNight
45%
720
28%
2118
14%
720
57%
720
44%
1138
March16th to endNight
45%
678
27%
2022
15%
678
56%
678
40%
1107
April1st to 15thNight
43%
539
24%
1798
15%
539
57%
539
35%
962
April16th to endNight
44%
540
22%
1800
17%
540
54%
540
28%
1070
May1st to 15thNight
53%
540
19%
1599
16%
540
57%
540
28%
1019
May16th to endNight
60%
563
18%
1498
13%
561
64%
561
37%
887
June1st to 15thNight
69%
540
21%
1440
17%
540
71%
540
48%
785
June16th to endNight
76%
540
27%
1440
21%
540
79%
540
56%
731
July1st to 15thNight
73%
510
17%
1360
15%
510
74%
510
36%
825
July16th to endNight
79%
564
26%
1436
25%
531
80%
531
45%
788
August1st to 15thNight
77%
527
20%
1629
22%
524
78%
524
40%
864
August16th to endNight
78%
525
27%
1750
31%
525
79%
525
40%
914
September1st to 15thNight
71%
495
30%
1650
31%
495
75%
495
39%
863
September16th to endNight
75%
492
36%
1773
37%
492
81%
492
50%
783
October1st to 15thNight
57%
649
29%
1969
20%
649
63%
649
42%
1053
October16th to endNight
58%
737
33%
2145
19%
737
67%
737
47%
1126
November1st to 15thNight
55%
875
33%
2275
18%
875
63%
875
53%
1215
November16th to endNight
54%
900
34%
2403
19%
900
63%
900
52%
1280
December1st to 15thNight
41%
900
25%
2520
10%
900
55%
900
44%
1383
December16th to endNight
42%
960
27%
2688
12%
960
55%
960
40%
1536

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
5%42332446%8%53%
47486
Night
5%42332335%7%58%
46678
Cloud CoverDay
5%4143245%6%8%53%
47484
Night
5%42332335%7%57%
46678
TransparencyDay
27%6%12%24%21%8%
47163
Night
25%5%11%25%23%8%
46504
SeeingDay
9%6%25%30%20%6%
5721
Night
6%229%41%17%1
15845

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
26%23322338%61%
1432
16th to endDay
15%24313348%62%
1692
February1st to 15thDay
16%36%424348%54%
1612
16th to endDay
25%25%32345%7%57%
1580
March1st to 15thDay
343442345%10%53%
1840
16th to endDay
6%6%233235%6%8%52%
2202
April1st to 15thDay
8%5%13323447%53%
2150
16th to endDay
12%6%2333446%7%44%
2160
May1st to 15thDay
11%6%24425%5%7%8%41%
2350
16th to endDay
9%5%15%425%5%7%9%44%
2616
June1st to 15thDay
6%313335%6%7%8%50%
2520
16th to endDay
223325%7%7%9%54%
2520
July1st to 15thDay
6%313426%7%7%9%46%
2520
16th to endDay
5%314425%6%8%10%48%
2632
August1st to 15thDay
5%3146%36%6%8%10%43%
2236
16th to endDay
5%2135%35%5%6%9%50%
2100
September1st to 15thDay
7%31331446%6%56%
1980
16th to endDay
5%312322336%65%
1856
October1st to 15thDay
6%313413446%59%
1659
16th to endDay
5%412213226%66%
1716
November1st to 15thDay
241431346%7%61%
1583
16th to endDay
341322235%7%61%
1554
December1st to 15thDay
25%34323448%55%
1440
16th to endDay
45%24323448%55%
1536
January1st to 15thNight
324323337%63%
2506
16th to endNight
26%35%313335%61%
2543
February1st to 15thNight
27%36%323347%55%
2238
16th to endNight
28%25%323345%57%
1894
March1st to 15thNight
35%2442245%7%57%
2118
16th to endNight
6%6%13323347%56%
2022
April1st to 15thNight
8%5%2332335%6%55%
1798
16th to endNight
14%6%24423346%48%
1800
May1st to 15thNight
12%6%24325%46%7%44%
1598
16th to endNight
8%41432435%8%53%
1497
June1st to 15thNight
5%2123145%5%10%58%
1440
16th to endNight
21231346%7%65%
1440
July1st to 15thNight
5%3245%345%7%9%49%
1440
16th to endNight
4212325%6%7%8%55%
1533
August1st to 15thNight
321343446%9%55%
1638
16th to endNight
5%21333445%8%56%
1750
September1st to 15thNight
9%31422336%8%55%
1650
16th to endNight
5%112222245%68%
1773
October1st to 15thNight
8%413313245%60%
1969
16th to endNight
6%423322246%61%
2145
November1st to 15thNight
3213323346%64%
2275
16th to endNight
35%23212336%64%
2403
December1st to 15thNight
36%3431335%8%57%
2520
16th to endNight
37%3432346%7%53%
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
26%23313248%60%
1432
16th to endDay
1434312347%61%
1692
February1st to 15thDay
16%36%424448%54%
1612
16th to endDay
25%16%32345%7%57%
1580
March1st to 15thDay
3425%5%2345%9%53%
1840
16th to endDay
7%5%233235%6%8%52%
2200
April1st to 15thDay
9%5%1331445%8%53%
2150
16th to endDay
12%6%2433446%7%44%
2160
May1st to 15thDay
12%6%244246%6%8%41%
2350
16th to endDay
10%5%14425%5%7%9%43%
2616
June1st to 15thDay
5%313435%6%7%9%49%
2520
16th to endDay
2212425%6%7%10%54%
2520
July1st to 15thDay
7%313436%6%8%10%46%
2520
16th to endDay
4315%325%6%7%10%48%
2632
August1st to 15thDay
5%315%5%36%7%7%10%43%
2236
16th to endDay
5%213436%5%6%9%51%
2100
September1st to 15thDay
7%41322446%7%55%
1980
16th to endDay
4312322336%65%
1856
October1st to 15thDay
6%41342335%6%59%
1659
16th to endDay
5%412213235%66%
1716
November1st to 15thDay
241331345%7%61%
1583
16th to endDay
242221345%7%61%
1554
December1st to 15thDay
25%25%42345%8%54%
1440
16th to endDay
45%3432335%7%54%
1536
January1st to 15thNight
423323346%63%
2506
16th to endNight
26%35%313335%61%
2543
February1st to 15thNight
27%36%323347%55%
2238
16th to endNight
28%35%413345%56%
1894
March1st to 15thNight
342441335%7%57%
2118
16th to endNight
6%6%1332325%7%56%
2022
April1st to 15thNight
7%6%23423447%55%
1798
16th to endNight
14%7%14413446%48%
1800
May1st to 15thNight
13%5%2442445%7%44%
1598
16th to endNight
8%31342435%8%53%
1497
June1st to 15thNight
5%21232445%9%59%
1440
16th to endNight
22231246%8%64%
1440
July1st to 15thNight
6%3144346%6%8%50%
1440
16th to endNight
4212326%47%8%56%
1533
August1st to 15thNight
322332446%9%55%
1638
16th to endNight
5%3134245%6%7%56%
1750
September1st to 15thNight
8%21431336%7%56%
1650
16th to endNight
422313346%67%
1773
October1st to 15thNight
8%413322346%59%
1969
16th to endNight
6%413312346%61%
2145
November1st to 15thNight
3213322346%65%
2275
16th to endNight
25%22212346%64%
2403
December1st to 15thNight
36%2432335%7%57%
2520
16th to endNight
37%2442346%7%53%
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
22%313%33%22%4
1433
16th to endDay
21%210%35%21%7%
1692
February1st to 15thDay
28%415%32%14%4
1613
16th to endDay
24%5%9%28%26%5%
1580
March1st to 15thDay
26%410%27%23%7%
1840
16th to endDay
29%5%14%22%21%5%
2202
April1st to 15thDay
29%5%12%25%20%8%
2150
16th to endDay
35%7%12%21%18%4
2160
May1st to 15thDay
37%8%14%22%13%3
2350
16th to endDay
34%7%15%22%12%6%
2620
June1st to 15thDay
27%8%14%20%18%10%
2520
16th to endDay
20%7%11%20%28%10%
2520
July1st to 15thDay
31%8%13%19%15%12%
2371
16th to endDay
27%9%14%23%17%7%
2467
August1st to 15thDay
32%9%14%17%15%10%
2221
16th to endDay
27%7%12%21%23%7%
2100
September1st to 15thDay
26%5%10%20%20%16%
1980
16th to endDay
19%37%23%36%9%
1856
October1st to 15thDay
23%5%13%19%27%10%
1659
16th to endDay
20%38%27%29%10%
1716
November1st to 15thDay
20%410%27%25%11%
1583
16th to endDay
19%38%26%31%9%
1554
December1st to 15thDay
26%5%12%33%19%3
1440
16th to endDay
28%5%15%24%20%6%
1536
January1st to 15thNight
21%411%30%26%5%
2506
16th to endNight
26%38%28%25%8%
2543
February1st to 15thNight
29%410%31%19%3
2248
16th to endNight
28%46%27%23%9%
1894
March1st to 15thNight
24%49%25%27%7%
2118
16th to endNight
27%411%26%24%5%
2022
April1st to 15thNight
28%5%12%24%21%8%
1798
16th to endNight
36%5%10%24%17%5%
1800
May1st to 15thNight
37%8%14%20%15%4
1599
16th to endNight
28%8%20%23%13%6%
1498
June1st to 15thNight
21%6%17%28%14%11%
1440
16th to endNight
15%6%12%22%31%12%
1440
July1st to 15thNight
28%10%14%20%16%9%
1360
16th to endNight
21%8%15%29%16%8%
1436
August1st to 15thNight
24%7%16%24%18%9%
1629
16th to endNight
24%7%11%24%24%8%
1750
September1st to 15thNight
26%5%13%21%18%15%
1650
16th to endNight
17%48%26%33%9%
1773
October1st to 15thNight
25%5%12%18%27%10%
1969
16th to endNight
23%38%24%28%10%
2145
November1st to 15thNight
19%48%25%27%13%
2275
16th to endNight
21%38%25%31%10%
2403
December1st to 15thNight
25%414%30%20%5%
2520
16th to endNight
27%6%15%27%20%3
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%7%24%37%15%6%
90
16th to endDay
5%330%39%18%3
96
February1st to 15thDay
411%42%40%2
90
16th to endDay
3440%37%9%3
81
March1st to 15thDay
416%27%39%9%2
130
16th to endDay
15%21%32%24%41
288
April1st to 15thDay
12%17%35%21%9%3
269
16th to endDay
22%16%33%20%5%1
270
May1st to 15thDay
14%7%26%32%16%2
428
16th to endDay
14%7%23%28%17%7%
517
June1st to 15thDay
7%324%30%26%7%
495
16th to endDay
4223%33%27%8%
495
July1st to 15thDay
11%215%27%34%9%
475
16th to endDay
6%115%27%37%12%
491
August1st to 15thDay
8%428%29%21%8%
300
16th to endDay
7%422%38%21%6%
268
September1st to 15thDay
7%430%35%19%2
255
16th to endDay
3318%38%22%12%
131
October1st to 15thDay
8%118%33%26%11%
90
16th to endDay
6%128%30%29%5%
96
November1st to 15thDay
1116%35%32%13%
90
16th to endDay
11%7%27%40%13%
90
December1st to 15thDay
6%8%46%27%8%1
90
16th to endDay
4234%50%7%2
96
January1st to 15thNight
2343%37%10%2
900
16th to endNight
5%345%35%9%
815
February1st to 15thNight
6%246%39%5%
704
16th to endNight
5%444%39%5%
632
March1st to 15thNight
5%141%40%10%
720
16th to endNight
7%6%36%42%7%
678
April1st to 15thNight
10%5%36%39%8%
539
16th to endNight
16%430%35%12%
540
May1st to 15thNight
16%318%44%14%1
540
16th to endNight
9%122%40%23%2
563
June1st to 15thNight
6%217%48%22%2
540
16th to endNight
2113%48%32%1
540
July1st to 15thNight
6%18%39%40%2
510
16th to endNight
46%37%47%3
564
August1st to 15thNight
5%8%43%40%2
527
16th to endNight
5%8%42%37%4
525
September1st to 15thNight
8%12%47%25%4
495
16th to endNight
413%46%30%4
492
October1st to 15thNight
11%224%40%18%3
649
16th to endNight
6%225%44%17%2
737
November1st to 15thNight
4331%44%14%2
875
16th to endNight
5%233%46%11%1
900
December1st to 15thNight
5%343%39%8%
900
16th to endNight
5%340%39%8%1
960
Page generated at 2017-08-13 12:16:20. Version ac04

Copyright 2017 A. Danko


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