Elkhorn Ranch
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Elkhorn Ranch clear sky chart from 2005-11-05 to 2017-09-18.

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
42%
15920
27%
46883
13%
15875
56%
15875
37%
25201

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
31%
900
31%
2506
10%
895
51%
895
43%
1229
January16th to endNight
27%
783
35%
2511
14%
783
52%
783
41%
1198
February1st to 15thNight
25%
700
27%
2249
9%
697
46%
697
36%
1147
February16th to endNight
24%
632
34%
1894
7%
632
52%
632
39%
965
March1st to 15thNight
33%
720
28%
2100
9%
720
49%
720
35%
1138
March16th to endNight
30%
687
28%
2031
10%
687
47%
687
33%
1125
April1st to 15thNight
30%
539
25%
1798
11%
539
48%
539
32%
919
April16th to endNight
31%
540
22%
1800
11%
540
47%
540
24%
1063
May1st to 15thNight
42%
539
19%
1630
12%
539
51%
539
25%
1038
May16th to endNight
47%
562
17%
1498
9%
561
56%
561
34%
892
June1st to 15thNight
60%
540
23%
1440
14%
540
67%
540
50%
747
June16th to endNight
69%
540
25%
1440
18%
540
73%
540
50%
754
July1st to 15thNight
71%
510
16%
1360
14%
510
73%
510
31%
858
July16th to endNight
71%
564
16%
1470
14%
531
73%
531
33%
903
August1st to 15thNight
69%
539
16%
1668
15%
536
72%
536
31%
968
August16th to endNight
71%
573
24%
1910
25%
573
73%
573
32%
1074
September1st to 15thNight
65%
540
26%
1800
24%
540
71%
540
34%
995
September16th to endNight
58%
501
33%
1795
24%
501
71%
501
40%
857
October1st to 15thNight
44%
659
31%
1979
16%
659
55%
659
43%
1020
October16th to endNight
51%
717
35%
2125
17%
717
63%
717
46%
1072
November1st to 15thNight
40%
875
34%
2275
13%
875
54%
875
47%
1190
November16th to endNight
34%
900
35%
2396
12%
900
52%
900
48%
1211
December1st to 15thNight
28%
900
25%
2520
7%
900
44%
900
36%
1326
December16th to endNight
24%
960
27%
2688
7%
960
42%
960
32%
1512

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
45%25%5%345%6%7%49%
47923
Night
342332445%8%58%
47061
TransparencyDay
31%7%12%22%19%6%
47603
Night
23%6%14%28%21%6%
46883
SeeingDay
11%16%31%24%13%2
5829
Night
5%12%33%32%13%1
15926

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
142432335%7%61%
1432
16th to endDay
435%312448%60%
1723
February1st to 15thDay
5%26%42445%8%55%
1612
16th to endDay
5%26%325%448%57%
1580
March1st to 15thDay
25%25%424449%53%
1857
16th to endDay
38%344345%6%8%47%
2193
April1st to 15thDay
48%245%25%45%8%46%
2150
16th to endDay
8%12%35%5%35%446%40%
2160
May1st to 15thDay
9%9%26%5%35%5%6%8%37%
2317
16th to endDay
7%6%36%5%35%6%7%8%38%
2616
June1st to 15thDay
5%4244345%7%9%47%
2520
16th to endDay
33145%35%6%7%8%50%
2520
July1st to 15thDay
7%5%26%7%46%7%8%7%36%
2520
16th to endDay
7%5%36%6%47%6%7%8%35%
2594
August1st to 15thDay
8%5%37%8%36%6%7%7%35%
2281
16th to endDay
6%425%5%45%6%7%8%42%
2292
September1st to 15thDay
7%425%5%345%5%6%49%
2160
16th to endDay
432242445%5%60%
1889
October1st to 15thDay
5%423434446%56%
1650
16th to endDay
45%13312347%61%
1735
November1st to 15thDay
132431245%7%63%
1583
16th to endDay
424214347%64%
1563
December1st to 15thDay
346%42325%7%59%
1440
16th to endDay
42442446%8%56%
1536
January1st to 15thNight
31332335%7%66%
2506
16th to endNight
324313336%65%
2511
February1st to 15thNight
5%35%324347%61%
2239
16th to endNight
42431335%6%63%
1894
March1st to 15thNight
24233245%5%6%58%
2100
16th to endNight
36%23323446%59%
2031
April1st to 15thNight
27%2322335%6%59%
1798
16th to endNight
8%10%23323336%51%
1800
May1st to 15thNight
9%6%244245%6%9%43%
1629
16th to endNight
6%42343447%9%50%
1497
June1st to 15thNight
231221435%10%63%
1440
16th to endNight
2122345%7%9%60%
1440
July1st to 15thNight
5%3245%36%5%5%11%45%
1440
16th to endNight
5%314446%6%8%10%44%
1571
August1st to 15thNight
4424435%5%7%9%48%
1677
16th to endNight
431443447%9%50%
1910
September1st to 15thNight
7%3244245%6%9%50%
1800
16th to endNight
331331335%6%63%
1795
October1st to 15thNight
4312314446%62%
1979
16th to endNight
35%2221335%7%63%
2125
November1st to 15thNight
1312323248%66%
2275
16th to endNight
5%13213347%66%
2396
December1st to 15thNight
141341345%9%60%
2520
16th to endNight
15%45%42335%8%55%
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
21%419%30%19%4
1433
16th to endDay
21%5%14%32%19%6%
1723
February1st to 15thDay
25%416%32%16%4
1613
16th to endDay
24%5%10%29%24%4
1580
March1st to 15thDay
27%5%11%28%22%4
1857
16th to endDay
33%6%10%25%19%4
2193
April1st to 15thDay
32%7%11%25%16%6%
2150
16th to endDay
43%6%10%20%16%3
2160
May1st to 15thDay
43%7%11%19%16%
2317
16th to endDay
39%9%13%19%12%5%
2620
June1st to 15thDay
29%9%13%16%19%11%
2520
16th to endDay
27%7%9%20%23%11%
2520
July1st to 15thDay
40%9%11%15%14%7%
2371
16th to endDay
41%11%14%18%9%3
2432
August1st to 15thDay
44%10%11%13%13%6%
2266
16th to endDay
36%8%11%21%18%3
2292
September1st to 15thDay
34%6%10%18%20%9%
2160
16th to endDay
24%49%22%32%6%
1889
October1st to 15thDay
27%5%9%23%27%6%
1650
16th to endDay
23%49%24%31%7%
1735
November1st to 15thDay
19%412%24%26%12%
1583
16th to endDay
19%38%30%29%8%
1563
December1st to 15thDay
24%5%16%30%19%3
1440
16th to endDay
24%5%18%25%19%5%
1536
January1st to 15thNight
16%418%32%23%3
2506
16th to endNight
19%312%31%24%7%
2511
February1st to 15thNight
22%5%13%38%15%4
2249
16th to endNight
20%49%33%24%6%
1894
March1st to 15thNight
22%6%10%30%25%4
2100
16th to endNight
26%5%11%31%21%3
2031
April1st to 15thNight
24%5%12%31%19%6%
1798
16th to endNight
34%6%12%27%15%3
1800
May1st to 15thNight
36%9%12%23%15%2
1630
16th to endNight
27%8%21%24%13%5%
1498
June1st to 15thNight
17%6%19%25%17%14%
1440
16th to endNight
18%7%14%23%24%12%
1440
July1st to 15thNight
32%10%15%20%14%7%
1360
16th to endNight
29%10%22%23%10%2
1470
August1st to 15thNight
30%8%19%20%14%5%
1668
16th to endNight
29%8%15%26%16%3
1910
September1st to 15thNight
28%7%14%22%17%8%
1800
16th to endNight
21%6%11%29%26%5%
1795
October1st to 15thNight
21%5%12%26%26%7%
1979
16th to endNight
20%410%27%30%6%
2125
November1st to 15thNight
17%5%11%27%26%12%
2275
16th to endNight
17%310%29%29%8%
2396
December1st to 15thNight
20%6%19%30%18%4
2520
16th to endNight
26%5%16%25%20%4
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
16%13%31%14%23%1
90
16th to endDay
210%47%32%7%
96
February1st to 15thDay
10%27%42%17%2
90
16th to endDay
9%27%30%24%6%1
81
March1st to 15thDay
13%23%40%18%2
147
16th to endDay
13%38%33%13%1
288
April1st to 15thDay
16%35%28%14%21
269
16th to endDay
27%32%25%11%3
270
May1st to 15thDay
15%18%36%20%7%1
400
16th to endDay
12%15%29%24%15%1
517
June1st to 15thDay
8%12%31%26%17%3
495
16th to endDay
410%33%30%18%3
495
July1st to 15thDay
7%6%24%33%21%6%
475
16th to endDay
11%322%29%26%6%
453
August1st to 15thDay
14%8%29%31%13%3
315
16th to endDay
13%9%31%30%13%2
332
September1st to 15thDay
9%17%32%27%10%2
315
16th to endDay
413%39%24%14%3
149
October1st to 15thDay
311%36%28%11%8%
90
16th to endDay
13%15%28%30%8%4
96
November1st to 15thDay
5%14%30%17%28%3
90
16th to endDay
6%25%42%18%6%
90
December1st to 15thDay
12%28%43%13%2
90
16th to endDay
420%45%21%5%2
96
January1st to 15thNight
219%41%26%7%2
900
16th to endNight
216%47%25%6%1
783
February1st to 15thNight
217%50%25%4
704
16th to endNight
219%47%26%3
632
March1st to 15thNight
316%42%28%7%
720
16th to endNight
6%17%41%28%5%
687
April1st to 15thNight
7%20%38%28%4
539
16th to endNight
12%17%32%28%7%
540
May1st to 15thNight
11%8%31%35%10%1
540
16th to endNight
7%9%28%35%15%2
563
June1st to 15thNight
46%25%44%16%2
540
16th to endNight
2221%49%23%1
540
July1st to 15thNight
7%110%43%33%3
510
16th to endNight
5%110%37%40%4
564
August1st to 15thNight
7%111%43%30%3
539
16th to endNight
6%312%43%30%3
573
September1st to 15thNight
8%316%41%26%4
540
16th to endNight
5%5%24%37%24%2
501
October1st to 15thNight
410%36%30%14%3
659
16th to endNight
5%9%29%36%14%3
717
November1st to 15thNight
416%35%30%12%1
875
16th to endNight
316%42%28%8%1
900
December1st to 15thNight
322%41%26%5%
900
16th to endNight
5%19%45%23%6%
960
Page generated at 2017-09-19 05:32:27. Version ac04

Copyright 2017 A. Danko


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