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 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
55%
16617
28%
48818
18%
16576
64%
16576
42%
26440

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
44%
972
31%
2716
15%
970
59%
970
48%
1437
January16th to endNight
41%
883
34%
2755
21%
883
57%
883
43%
1428
February1st to 15thNight
36%
755
25%
2427
12%
754
52%
754
37%
1328
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
44%
539
24%
1798
15%
539
57%
539
35%
962
April16th to endNight
43%
540
22%
1800
17%
540
54%
540
28%
1070
May1st to 15thNight
54%
540
19%
1599
16%
540
57%
540
28%
1019
May16th to endNight
61%
563
18%
1498
13%
561
65%
561
37%
887
June1st to 15thNight
70%
540
21%
1440
17%
540
72%
540
48%
785
June16th to endNight
77%
540
27%
1440
21%
540
80%
540
56%
731
July1st to 15thNight
73%
510
17%
1360
15%
510
74%
510
36%
825
July16th to endNight
80%
564
26%
1436
25%
531
81%
531
45%
788
August1st to 15thNight
78%
539
20%
1668
22%
536
78%
536
40%
882
August16th to endNight
79%
573
29%
1910
33%
573
80%
573
41%
987
September1st to 15thNight
73%
540
28%
1800
30%
540
77%
540
41%
927
September16th to endNight
73%
537
36%
1934
36%
537
80%
537
47%
880
October1st to 15thNight
57%
708
28%
2148
20%
708
64%
708
43%
1142
October16th to endNight
59%
804
35%
2340
21%
804
68%
804
47%
1224
November1st to 15thNight
56%
950
32%
2470
17%
950
63%
950
53%
1321
November16th to endNight
54%
975
35%
2603
19%
975
63%
975
53%
1376
December1st to 15thNight
42%
975
26%
2730
10%
975
56%
975
45%
1485
December16th to endNight
42%
1040
27%
2912
12%
1040
55%
1040
40%
1663

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%
49275
Night
5%42332335%7%58%
48992
Cloud CoverDay
5%41432446%8%53%
49273
Night
5%42332335%7%57%
48992
TransparencyDay
27%6%12%24%21%8%
48952
Night
25%5%11%25%23%8%
48818
SeeingDay
9%6%26%31%20%6%
6318
Night
6%229%41%17%1
16625

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%60%
1552
16th to endDay
15%24313348%61%
1833
February1st to 15thDay
15%36%424348%54%
1733
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%3136%36%6%8%10%43%
2283
16th to endDay
5%2135%35%5%7%9%51%
2292
September1st to 15thDay
7%31332446%7%56%
2160
16th to endDay
5%412322346%63%
2025
October1st to 15thDay
6%313413346%59%
1810
16th to endDay
5%412213226%66%
1872
November1st to 15thDay
241431346%7%61%
1718
16th to endDay
241332235%8%62%
1683
December1st to 15thDay
25%34323448%56%
1560
16th to endDay
45%24323448%56%
1664
January1st to 15thNight
1424323347%63%
2716
16th to endNight
26%25%313236%61%
2755
February1st to 15thNight
27%35%323347%55%
2417
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
321342446%10%54%
1677
16th to endNight
5%213335%45%8%56%
1910
September1st to 15thNight
8%31422336%8%56%
1800
16th to endNight
6%212223345%66%
1934
October1st to 15thNight
8%413313245%61%
2148
16th to endNight
6%413322236%61%
2340
November1st to 15thNight
3223223347%63%
2470
16th to endNight
3413212346%64%
2603
December1st to 15thNight
36%34313247%58%
2730
16th to endNight
37%2442346%7%53%
2912

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%23322248%60%
1552
16th to endDay
1424322347%61%
1833
February1st to 15thDay
16%36%424348%54%
1733
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%
2283
16th to endDay
5%213435%5%7%9%51%
2292
September1st to 15thDay
6%31222446%7%56%
2160
16th to endDay
6%312322336%63%
2025
October1st to 15thDay
6%41332335%6%59%
1810
16th to endDay
5%412212235%66%
1872
November1st to 15thDay
241431346%7%60%
1718
16th to endDay
242221345%7%62%
1683
December1st to 15thDay
25%25%423448%56%
1560
16th to endDay
45%3432335%7%55%
1664
January1st to 15thNight
1424323346%62%
2716
16th to endNight
26%34312336%61%
2755
February1st to 15thNight
17%36%423347%55%
2417
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
32133245%6%10%55%
1677
16th to endNight
5%3134245%6%7%57%
1910
September1st to 15thNight
8%21431336%7%57%
1800
16th to endNight
6%23313345%65%
1934
October1st to 15thNight
8%413322346%60%
2148
16th to endNight
6%413322346%61%
2340
November1st to 15thNight
3213323346%64%
2470
16th to endNight
2422312347%64%
2603
December1st to 15thNight
36%24323347%58%
2730
16th to endNight
36%3442346%7%53%
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
23%313%32%22%5%
1553
16th to endDay
22%310%34%21%7%
1833
February1st to 15thDay
28%415%31%14%4
1734
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
31%9%14%17%15%10%
2268
16th to endDay
26%7%12%21%24%8%
2292
September1st to 15thDay
25%5%10%21%21%15%
2160
16th to endDay
22%47%22%34%9%
2025
October1st to 15thDay
23%5%12%19%27%11%
1810
16th to endDay
20%38%26%28%11%
1872
November1st to 15thDay
20%410%28%26%10%
1718
16th to endDay
19%39%25%32%9%
1683
December1st to 15thDay
25%5%11%32%20%4
1560
16th to endDay
27%5%14%25%21%5%
1664
January1st to 15thNight
21%5%11%31%25%5%
2716
16th to endNight
25%38%27%26%7%
2755
February1st to 15thNight
28%5%11%31%19%3
2427
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
23%7%17%24%17%9%
1668
16th to endNight
23%6%10%24%26%8%
1910
September1st to 15thNight
25%5%13%23%18%14%
1800
16th to endNight
19%39%25%31%9%
1934
October1st to 15thNight
24%5%12%19%27%11%
2148
16th to endNight
23%38%24%28%11%
2340
November1st to 15thNight
19%48%26%27%12%
2470
16th to endNight
20%38%25%30%9%
2603
December1st to 15thNight
24%413%29%20%6%
2730
16th to endNight
27%5%15%26%20%3
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
7%7%25%43%11%4
135
16th to endDay
3333%40%16%2
144
February1st to 15thDay
410%47%34%2
130
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
7%427%29%22%8%
315
16th to endDay
6%320%37%25%7%
332
September1st to 15thDay
6%326%33%21%8%
315
16th to endDay
7%322%38%18%9%
180
October1st to 15thDay
10%321%33%22%8%
135
16th to endDay
8%228%31%24%4
144
November1st to 15thDay
222%40%25%8%
135
16th to endDay
8%6%29%42%12%
135
December1st to 15thDay
5%9%44%28%10%
135
16th to endDay
4239%45%7%1
144
January1st to 15thNight
3342%39%9%2
975
16th to endNight
5%343%37%9%
883
February1st to 15thNight
5%246%39%5%
760
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%7%42%41%2
539
16th to endNight
5%8%42%38%4
573
September1st to 15thNight
8%11%44%28%5%
540
16th to endNight
5%14%46%28%4
537
October1st to 15thNight
11%124%41%17%3
708
16th to endNight
7%225%44%17%2
804
November1st to 15thNight
4230%46%13%2
950
16th to endNight
5%234%46%10%
975
December1st to 15thNight
5%342%40%8%
975
16th to endNight
5%340%40%8%1
1040
Page generated at 2018-02-15 08:58:50. Version ac04

Copyright 2018 A. Danko


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