Bluefield Ranch
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bluefield Ranch 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
64%
16229
19%
47137
16%
16191
67%
16191
30%
30055

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
53%
716
17%
2327
14%
716
59%
716
27%
1441
January16th to endNight
50%
768
25%
2484
20%
768
59%
768
32%
1427
February1st to 15thNight
50%
701
25%
2105
19%
699
57%
699
34%
1247
February16th to endNight
56%
631
29%
1755
18%
631
65%
631
38%
1017
March1st to 15thNight
58%
720
28%
1980
18%
720
66%
720
44%
1103
March16th to endNight
63%
768
26%
2112
21%
768
67%
768
44%
1181
April1st to 15thNight
68%
718
23%
1976
20%
718
70%
718
45%
1103
April16th to endNight
67%
720
26%
1803
16%
720
70%
720
44%
1084
May1st to 15thNight
72%
703
24%
1783
17%
703
74%
703
45%
1054
May16th to endNight
78%
561
18%
1682
16%
561
78%
561
32%
1061
June1st to 15thNight
65%
540
9%
1620
8%
540
65%
540
19%
1189
June16th to endNight
77%
540
10%
1620
9%
540
77%
540
23%
1146
July1st to 15thNight
69%
510
6%
1530
5%
510
69%
510
19%
1126
July16th to endNight
78%
564
9%
1595
8%
531
78%
531
25%
1111
August1st to 15thNight
78%
572
8%
1642
7%
569
78%
569
25%
1145
August16th to endNight
65%
764
6%
2015
4%
764
65%
764
18%
1550
September1st to 15thNight
67%
720
5%
1980
4%
720
67%
720
18%
1495
September16th to endNight
63%
717
8%
1980
8%
717
63%
717
17%
1506
October1st to 15thNight
67%
684
20%
1981
22%
684
68%
684
27%
1284
October16th to endNight
61%
704
22%
2112
22%
704
65%
704
28%
1350
November1st to 15thNight
65%
700
26%
2101
25%
700
69%
700
34%
1253
November16th to endNight
57%
720
26%
2160
23%
720
64%
720
30%
1330
December1st to 15thNight
59%
720
24%
2298
22%
720
65%
720
27%
1416
December16th to endNight
63%
768
23%
2496
22%
768
67%
768
32%
1436

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
7%5%36%7%47%7%7%9%32%
48037
Night
7%425%5%35%5%6%9%42%
47344
TransparencyDay
43%10%15%15%10%3
47738
Night
34%9%17%20%13%4
47147
SeeingDay
7%112%21%27%29%
6054
Night
8%214%31%32%11%
16239

By Month

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
10%6%36%5%45%6%5%9%36%
1611
16th to endDay
9%325%5%36%5%7%8%41%
1737
February1st to 15thDay
10%5%235%25%46%9%43%
1750
16th to endDay
6%414445%6%6%9%46%
1715
March1st to 15thDay
4325%6%47%6%7%8%44%
1980
16th to endDay
5%435%6%35%5%5%10%43%
2111
April1st to 15thDay
5%215%6%46%7%7%10%41%
1972
16th to endDay
5%435%7%46%6%7%10%39%
2155
May1st to 15thDay
5%3245%45%5%7%10%45%
2175
16th to endDay
7%437%8%5%8%8%8%10%28%
2431
June1st to 15thDay
10%7%47%10%5%7%7%8%10%18%
2340
16th to endDay
7%5%38%10%5%10%9%8%9%20%
2340
July1st to 15thDay
8%6%48%9%6%9%8%9%9%18%
2340
16th to endDay
6%6%38%10%6%9%9%9%10%19%
2465
August1st to 15thDay
6%427%9%6%9%9%9%10%23%
2292
16th to endDay
8%5%39%9%6%10%8%9%8%19%
2184
September1st to 15thDay
7%5%48%8%5%10%9%9%10%20%
1980
16th to endDay
10%8%39%10%6%8%7%8%8%18%
1980
October1st to 15thDay
8%5%27%8%47%7%8%8%31%
1775
16th to endDay
10%6%25%7%46%6%7%9%33%
1760
November1st to 15thDay
6%5%17%6%37%6%5%8%40%
1757
16th to endDay
8%6%36%6%46%5%6%8%38%
1800
December1st to 15thDay
12%5%36%6%35%46%7%38%
1659
16th to endDay
6%425%6%35%5%7%11%41%
1728
January1st to 15thNight
7%6%25%5%35%5%6%10%40%
2327
16th to endNight
8%424425%5%6%8%47%
2484
February1st to 15thNight
10%5%24424346%50%
2103
16th to endNight
6%313335%5%5%9%51%
1755
March1st to 15thNight
421442445%9%56%
1980
16th to endNight
4213425%5%5%8%55%
2112
April1st to 15thNight
421342446%9%56%
1976
16th to endNight
6%22332447%8%53%
1803
May1st to 15thNight
43224245%5%9%55%
1783
16th to endNight
6%3245%35%6%8%11%42%
1682
June1st to 15thNight
10%6%36%6%48%6%8%12%25%
1620
16th to endNight
5%426%6%5%7%7%7%13%33%
1620
July1st to 15thNight
9%7%35%6%47%6%7%10%32%
1620
16th to endNight
3436%7%37%5%8%13%35%
1703
August1st to 15thNight
5%5%15%6%35%7%8%13%35%
1653
16th to endNight
10%5%26%7%47%7%8%11%29%
2015
September1st to 15thNight
7%5%37%7%5%6%8%9%10%28%
1980
16th to endNight
9%7%36%7%5%7%6%9%10%26%
1980
October1st to 15thNight
7%5%26%5%45%5%7%9%39%
1981
16th to endNight
9%5%245%35%5%6%9%41%
2112
November1st to 15thNight
5%425%5%35%5%5%8%47%
2101
16th to endNight
7%5%345%36%45%7%45%
2160
December1st to 15thNight
8%426%5%35%5%6%7%43%
2298
16th to endNight
5%424435%5%6%9%47%
2496

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
42%8%12%16%15%4
1612
16th to endDay
37%5%11%19%17%8%
1737
February1st to 15thDay
36%5%9%21%17%9%
1752
16th to endDay
31%6%15%21%17%7%
1715
March1st to 15thDay
33%5%14%23%17%5%
1980
16th to endDay
34%6%14%19%17%6%
2112
April1st to 15thDay
32%8%15%21%17%3
1972
16th to endDay
37%5%13%18%19%4
2155
May1st to 15thDay
31%7%14%23%16%6%
2175
16th to endDay
46%10%15%17%9%
2435
June1st to 15thDay
54%11%17%12%3
2340
16th to endDay
50%16%20%10%2
2340
July1st to 15thDay
53%18%18%7%1
2201
16th to endDay
51%16%21%10%
2310
August1st to 15thDay
45%17%26%9%
2279
16th to endDay
54%15%20%7%
2184
September1st to 15thDay
51%17%21%8%1
1980
16th to endDay
57%13%16%9%3
1980
October1st to 15thDay
45%8%14%16%12%2
1775
16th to endDay
43%6%11%15%15%6%
1760
November1st to 15thDay
39%5%10%20%15%7%
1757
16th to endDay
41%6%11%15%15%10%
1800
December1st to 15thDay
43%7%11%18%13%5%
1659
16th to endDay
36%6%14%20%15%5%
1728
January1st to 15thNight
37%6%16%21%13%4
2327
16th to endNight
32%5%11%26%16%6%
2484
February1st to 15thNight
33%5%8%21%21%9%
2112
16th to endNight
27%7%13%24%20%5%
1755
March1st to 15thNight
24%5%14%30%18%6%
1980
16th to endNight
24%6%15%26%19%7%
2112
April1st to 15thNight
22%7%19%27%18%5%
1976
16th to endNight
26%7%14%24%22%4
1803
May1st to 15thNight
24%7%13%30%17%6%
1784
16th to endNight
30%11%20%23%12%
1684
June1st to 15thNight
45%13%20%15%5%
1620
16th to endNight
38%15%26%17%2
1620
July1st to 15thNight
44%15%26%12%1
1530
16th to endNight
35%16%29%16%1
1595
August1st to 15thNight
33%18%33%14%
1642
16th to endNight
43%19%25%11%
2015
September1st to 15thNight
43%18%25%10%2
1980
16th to endNight
46%16%20%13%3
1980
October1st to 15thNight
37%9%15%18%17%2
1981
16th to endNight
37%7%11%17%18%6%
2112
November1st to 15thNight
33%5%11%21%21%6%
2101
16th to endNight
36%6%11%19%16%9%
2160
December1st to 15thNight
37%6%14%21%14%5%
2298
16th to endNight
31%7%16%22%16%5%
2496

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
17%431%26%14%5%
90
16th to endDay
13%12%25%29%16%3
96
February1st to 15thDay
5%6%26%31%22%7%
90
16th to endDay
7%5%26%36%23%1
216
March1st to 15thDay
4227%35%25%3
270
16th to endDay
5%419%32%32%5%
288
April1st to 15thDay
3223%31%28%10%
270
16th to endDay
6%116%28%28%18%
270
May1st to 15thDay
5%111%22%37%22%
288
16th to endDay
5%16%17%35%34%
331
June1st to 15thDay
11%9%16%23%39%
315
16th to endDay
438%24%58%
315
July1st to 15thDay
5%15%25%61%
305
16th to endDay
8%28%22%57%
326
August1st to 15thDay
5%27%23%61%
313
16th to endDay
10%15%12%19%51%
332
September1st to 15thDay
7%412%22%53%
315
16th to endDay
10%413%28%42%
314
October1st to 15thDay
10%18%23%38%19%
278
16th to endDay
10%119%29%25%14%
272
November1st to 15thDay
9%19%34%30%14%
265
16th to endDay
6%221%34%30%4
270
December1st to 15thDay
17%320%34%19%5%
129
16th to endDay
2115%35%35%10%
96
January1st to 15thNight
10%423%34%24%2
720
16th to endNight
8%430%38%17%
768
February1st to 15thNight
10%427%39%16%
704
16th to endNight
9%225%43%18%
631
March1st to 15thNight
5%327%41%19%2
720
16th to endNight
6%221%43%25%
768
April1st to 15thNight
4218%45%26%2
718
16th to endNight
7%218%46%24%1
720
May1st to 15thNight
5%113%45%31%2
704
16th to endNight
6%15%31%42%13%
563
June1st to 15thNight
10%15%17%46%17%
540
16th to endNight
6%212%45%32%
540
July1st to 15thNight
9%29%45%32%
510
16th to endNight
416%45%40%
564
August1st to 15thNight
7%17%43%39%
572
16th to endNight
10%1414%39%30%
764
September1st to 15thNight
8%410%45%29%
720
16th to endNight
13%318%42%21%
717
October1st to 15thNight
10%8%32%37%10%
684
16th to endNight
13%113%30%33%6%
704
November1st to 15thNight
6%117%39%31%3
700
16th to endNight
9%320%38%25%2
720
December1st to 15thNight
9%317%39%27%2
720
16th to endNight
7%219%36%29%4
768
Page generated at 2017-10-07 14:07:44. Version ac04

Copyright 2017 A. Danko


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