Blackhawk Ranch
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Blackhawk Ranch clear sky chart from 2005-11-05 to 2017-09-23.

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
49%
15848
30%
46936
17%
15807
62%
15807
43%
24590

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%
891
31%
2497
16%
886
58%
886
49%
1262
January16th to endNight
38%
768
37%
2496
19%
768
59%
768
46%
1160
February1st to 15thNight
37%
700
28%
2187
13%
700
53%
700
38%
1161
February16th to endNight
31%
632
38%
1894
13%
632
56%
632
43%
936
March1st to 15thNight
39%
720
30%
2124
13%
720
54%
720
44%
1099
March16th to endNight
39%
669
33%
2013
15%
669
57%
669
45%
1003
April1st to 15thNight
32%
539
29%
1798
13%
539
53%
539
41%
855
April16th to endNight
39%
540
25%
1800
14%
540
56%
540
34%
969
May1st to 15thNight
41%
540
23%
1698
15%
540
53%
540
33%
980
May16th to endNight
46%
561
24%
1531
11%
561
58%
561
41%
882
June1st to 15thNight
51%
540
24%
1440
14%
540
58%
540
48%
795
June16th to endNight
63%
540
24%
1440
15%
540
70%
540
44%
816
July1st to 15thNight
65%
510
18%
1360
14%
510
68%
510
33%
868
July16th to endNight
76%
564
19%
1495
18%
531
76%
531
34%
906
August1st to 15thNight
70%
539
14%
1734
15%
536
72%
536
28%
1052
August16th to endNight
73%
573
24%
1910
26%
573
76%
573
35%
1060
September1st to 15thNight
64%
540
27%
1800
24%
540
72%
540
36%
976
September16th to endNight
65%
516
38%
1870
33%
516
77%
516
51%
791
October1st to 15thNight
52%
619
34%
1939
22%
619
62%
619
49%
933
October16th to endNight
59%
712
36%
2120
21%
712
68%
712
53%
1014
November1st to 15thNight
55%
875
38%
2275
18%
875
66%
875
62%
1105
November16th to endNight
51%
900
39%
2340
19%
900
61%
900
55%
1206
December1st to 15thNight
40%
900
31%
2487
11%
900
55%
900
48%
1298
December16th to endNight
38%
960
31%
2688
13%
960
52%
960
42%
1463

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
43133245%6%8%56%
47976
Night
331332345%7%60%
47116
Cloud CoverDay
431332446%8%56%
47974
Night
441332345%7%60%
47116
TransparencyDay
23%6%11%22%24%11%
47658
Night
22%5%11%23%25%11%
46936
SeeingDay
6%9%28%31%18%5%
5759
Night
5%6%33%36%15%2
15854

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
1323312337%68%
1451
16th to endDay
2323212246%67%
1728
February1st to 15thDay
2344423446%60%
1674
16th to endDay
141332335%8%61%
1580
March1st to 15thDay
242332346%7%60%
1834
16th to endDay
36%2321346%8%54%
2210
April1st to 15thDay
5%41332345%7%57%
2150
16th to endDay
6%5%243245%6%8%50%
2160
May1st to 15thDay
7%6%233245%6%7%50%
2250
16th to endDay
5%21233447%9%54%
2581
June1st to 15thDay
4212325%6%8%10%52%
2520
16th to endDay
2112325%6%9%10%55%
2520
July1st to 15thDay
4214447%8%9%10%42%
2520
16th to endDay
42145%35%7%9%12%41%
2567
August1st to 15thDay
6%424436%8%8%10%40%
2217
16th to endDay
43245%35%6%6%9%48%
2292
September1st to 15thDay
6%3144246%7%9%49%
2160
16th to endDay
222323436%67%
1924
October1st to 15thDay
421222335%6%64%
1689
16th to endDay
4311112246%70%
1738
November1st to 15thDay
121221235%7%69%
1583
16th to endDay
2412212246%68%
1620
December1st to 15thDay
425%212348%63%
1472
16th to endDay
25%1432445%7%57%
1536
January1st to 15thNight
1413313246%66%
2497
16th to endNight
2423212236%67%
2496
February1st to 15thNight
26%25%413336%58%
2177
16th to endNight
15%34222336%66%
1894
March1st to 15thNight
35%23223347%60%
2124
16th to endNight
3412223346%64%
2013
April1st to 15thNight
441221335%7%62%
1798
16th to endNight
8%5%22312347%56%
1800
May1st to 15thNight
7%6%2332435%7%52%
1697
16th to endNight
6%31331345%10%56%
1530
June1st to 15thNight
32122325%6%9%59%
1440
16th to endNight
3212325%5%8%11%53%
1440
July1st to 15thNight
5%2146%46%7%9%9%42%
1440
16th to endNight
4323436%8%9%12%42%
1598
August1st to 15thNight
4215%5%46%6%7%10%45%
1743
16th to endNight
5%22433448%11%49%
1910
September1st to 15thNight
6%41332448%11%49%
1800
16th to endNight
3111213447%68%
1870
October1st to 15thNight
5%312222236%66%
1939
16th to endNight
3312212345%68%
2120
November1st to 15thNight
1213111346%72%
2275
16th to endNight
3413212336%67%
2340
December1st to 15thNight
1222324348%63%
2487
16th to endNight
25%23224446%60%
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
1323212347%67%
1451
16th to endDay
2233212347%67%
1728
February1st to 15thDay
2433413346%60%
1674
16th to endDay
142332335%8%61%
1580
March1st to 15thDay
25%1321345%8%60%
1834
16th to endDay
46%2322346%8%55%
2208
April1st to 15thDay
5%4223235%47%57%
2150
16th to endDay
7%5%2432445%8%50%
2160
May1st to 15thDay
8%6%233245%6%8%49%
2250
16th to endDay
5%31222446%9%55%
2581
June1st to 15thDay
42123346%8%10%52%
2520
16th to endDay
212235%6%8%9%56%
2520
July1st to 15thDay
4213447%8%8%11%42%
2520
16th to endDay
43136%36%6%10%13%41%
2567
August1st to 15thDay
6%4135%36%7%9%10%41%
2217
16th to endDay
43144445%6%9%49%
2292
September1st to 15thDay
6%3134345%6%10%50%
2160
16th to endDay
312323347%68%
1924
October1st to 15thDay
421222335%6%64%
1689
16th to endDay
4311111245%70%
1738
November1st to 15thDay
12221235%7%69%
1583
16th to endDay
2412212346%68%
1620
December1st to 15thDay
15%2421235%7%63%
1472
16th to endDay
35%1432345%7%57%
1536
January1st to 15thNight
1323322246%67%
2497
16th to endNight
2423312336%67%
2496
February1st to 15thNight
26%25%423246%58%
2177
16th to endNight
15%33312335%65%
1894
March1st to 15thNight
442332335%7%60%
2124
16th to endNight
3412213346%64%
2013
April1st to 15thNight
4412213347%62%
1798
16th to endNight
8%6%23313346%56%
1800
May1st to 15thNight
8%6%1341445%6%52%
1697
16th to endNight
7%21231345%9%57%
1530
June1st to 15thNight
32123235%5%9%60%
1440
16th to endNight
33123246%8%10%54%
1440
July1st to 15thNight
5%2136%46%7%8%9%42%
1440
16th to endNight
4313427%7%9%11%43%
1598
August1st to 15thNight
42246%45%6%8%9%45%
1743
16th to endNight
6%3133245%8%10%49%
1910
September1st to 15thNight
6%3233235%6%12%49%
1800
16th to endNight
311222448%67%
1870
October1st to 15thNight
5%311322246%66%
1939
16th to endNight
332212246%67%
2120
November1st to 15thNight
1213111337%71%
2275
16th to endNight
3413212236%67%
2340
December1st to 15thNight
132332435%7%62%
2487
16th to endNight
35%23323447%59%
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
18%38%30%30%8%
1452
16th to endDay
18%28%26%32%10%
1728
February1st to 15thDay
24%48%28%25%8%
1675
16th to endDay
20%37%25%31%10%
1580
March1st to 15thDay
21%49%22%28%12%
1834
16th to endDay
25%5%10%22%27%8%
2210
April1st to 15thDay
24%5%10%24%22%12%
2150
16th to endDay
27%6%13%21%22%8%
2160
May1st to 15thDay
30%6%14%19%21%7%
2250
16th to endDay
23%8%13%21%19%13%
2585
June1st to 15thDay
22%8%14%17%19%17%
2520
16th to endDay
19%7%12%20%23%17%
2520
July1st to 15thDay
30%11%13%19%14%10%
2371
16th to endDay
27%12%18%25%12%3
2407
August1st to 15thDay
31%13%18%16%13%7%
2202
16th to endDay
29%9%13%21%21%5%
2292
September1st to 15thDay
27%7%14%24%17%8%
2160
16th to endDay
17%48%21%32%15%
1924
October1st to 15thDay
18%5%10%18%33%13%
1689
16th to endDay
15%37%22%34%16%
1738
November1st to 15thDay
13%39%24%29%19%
1583
16th to endDay
18%2421%35%17%
1620
December1st to 15thDay
20%412%26%26%9%
1472
16th to endDay
25%5%12%26%22%8%
1536
January1st to 15thNight
19%39%29%28%9%
2497
16th to endNight
18%37%25%33%11%
2496
February1st to 15thNight
27%39%29%22%7%
2187
16th to endNight
20%26%24%33%11%
1894
March1st to 15thNight
23%39%24%31%8%
2124
16th to endNight
20%410%23%31%10%
2013
April1st to 15thNight
20%412%26%23%12%
1798
16th to endNight
27%5%13%21%21%10%
1800
May1st to 15thNight
30%6%13%18%21%9%
1698
16th to endNight
23%8%15%19%18%13%
1531
June1st to 15thNight
20%7%13%20%17%21%
1440
16th to endNight
21%9%12%18%20%18%
1440
July1st to 15thNight
32%10%14%19%13%9%
1360
16th to endNight
26%12%20%23%13%2
1495
August1st to 15thNight
31%11%20%17%11%6%
1734
16th to endNight
27%8%14%25%16%6%
1910
September1st to 15thNight
26%8%15%25%16%7%
1800
16th to endNight
14%5%10%22%31%15%
1870
October1st to 15thNight
19%412%18%31%14%
1939
16th to endNight
17%38%19%33%17%
2120
November1st to 15thNight
13%28%24%30%20%
2275
16th to endNight
18%25%23%32%17%
2340
December1st to 15thNight
19%411%29%26%7%
2487
16th to endNight
24%412%24%25%9%
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
12%8%28%30%15%4
90
16th to endDay
413%36%25%17%3
96
February1st to 15thDay
7%10%46%22%13%
90
16th to endDay
6%13%40%30%7%1
81
March1st to 15thDay
320%36%32%7%
124
16th to endDay
10%27%36%19%5%1
288
April1st to 15thDay
8%25%37%20%43
269
16th to endDay
11%24%39%20%3
270
May1st to 15thDay
10%12%36%28%9%2
387
16th to endDay
7%9%33%31%14%3
517
June1st to 15thDay
49%27%32%21%6%
495
16th to endDay
4222%36%27%5%
495
July1st to 15thDay
7%216%34%30%8%
475
16th to endDay
419%35%32%15%
426
August1st to 15thDay
6%218%41%23%7%
315
16th to endDay
6%125%37%25%3
332
September1st to 15thDay
6%331%34%17%6%
315
16th to endDay
45%28%33%20%7%
142
October1st to 15thDay
311%23%33%18%10%
90
16th to endDay
5%5%34%28%20%6%
96
November1st to 15thDay
17%20%37%23%10%
90
16th to endDay
10%12%46%20%11%
90
December1st to 15thDay
36%60%23%6%
90
16th to endDay
6%16%45%28%3
96
January1st to 15thNight
38%38%33%12%3
891
16th to endNight
5%8%43%29%10%1
768
February1st to 15thNight
5%7%44%35%6%
704
16th to endNight
415%45%29%5%
632
March1st to 15thNight
6%9%40%33%8%
720
16th to endNight
6%9%41%36%5%
669
April1st to 15thNight
6%11%46%30%5%
539
16th to endNight
13%8%35%34%7%
540
May1st to 15thNight
10%5%38%34%11%
540
16th to endNight
8%5%36%34%13%2
563
June1st to 15thNight
4336%37%16%
540
16th to endNight
3125%44%23%1
540
July1st to 15thNight
6%115%40%33%2
510
16th to endNight
419%37%42%4
564
August1st to 15thNight
5%10%40%37%4
539
16th to endNight
6%10%42%34%4
573
September1st to 15thNight
8%120%40%24%4
540
16th to endNight
4323%43%19%4
516
October1st to 15thNight
6%333%37%15%3
619
16th to endNight
5%428%39%19%3
712
November1st to 15thNight
26%32%41%15%1
875
16th to endNight
5%7%33%38%13%2
900
December1st to 15thNight
28%45%33%7%1
900
16th to endNight
5%9%42%32%8%1
960
Page generated at 2017-09-24 07:15:47. Version ac04

Copyright 2017 A. Danko


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