Crestview
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Crestview 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
56%
15322
24%
47048
18%
15278
62%
15278
32%
27922

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
37%
720
24%
2262
13%
716
49%
716
27%
1371
January16th to endNight
32%
768
25%
2304
13%
768
43%
768
25%
1470
February1st to 15thNight
38%
704
28%
2111
14%
700
51%
700
33%
1235
February16th to endNight
33%
631
25%
1893
12%
631
43%
631
27%
1197
March1st to 15thNight
40%
720
25%
2142
14%
720
49%
720
32%
1288
March16th to endNight
48%
734
26%
2078
17%
734
55%
734
35%
1224
April1st to 15thNight
52%
539
25%
1797
23%
539
58%
539
28%
1053
April16th to endNight
60%
540
29%
1800
26%
540
69%
540
40%
927
May1st to 15thNight
61%
539
23%
1694
19%
539
67%
539
37%
943
May16th to endNight
72%
561
23%
1682
20%
561
74%
561
38%
961
June1st to 15thNight
74%
540
15%
1620
14%
540
75%
540
31%
996
June16th to endNight
77%
540
17%
1620
17%
540
78%
540
32%
996
July1st to 15thNight
82%
510
12%
1530
12%
510
82%
510
31%
952
July16th to endNight
79%
564
10%
1709
11%
531
80%
531
29%
1043
August1st to 15thNight
80%
539
11%
1788
14%
536
80%
536
27%
1112
August16th to endNight
67%
573
15%
1910
18%
573
67%
573
23%
1267
September1st to 15thNight
69%
639
17%
1899
17%
639
70%
639
29%
1210
September16th to endNight
66%
689
26%
1903
22%
689
68%
689
33%
1165
October1st to 15thNight
65%
660
33%
1815
24%
660
72%
660
47%
973
October16th to endNight
57%
704
35%
2039
29%
704
64%
704
40%
1133
November1st to 15thNight
55%
700
32%
2276
28%
700
64%
700
38%
1187
November16th to endNight
48%
720
31%
2340
24%
720
60%
720
37%
1251
December1st to 15thNight
46%
720
26%
2340
21%
720
55%
720
30%
1366
December16th to endNight
38%
768
22%
2496
16%
768
47%
768
22%
1602

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
10%5%25%6%35%5%6%8%40%
47835
Night
9%42442446%8%46%
47260
TransparencyDay
39%6%11%17%16%7%
47547
Night
33%6%13%19%18%9%
47052
SeeingDay
11%5%15%22%23%20%
5257
Night
11%5%19%29%26%6%
15325

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
12%6%25%424347%45%
1674
16th to endDay
16%6%25%323345%45%
1920
February1st to 15thDay
13%5%2442435%7%47%
1750
16th to endDay
14%6%245%23446%44%
1580
March1st to 15thDay
11%4245%335%6%7%46%
1818
16th to endDay
11%4145%2445%6%48%
2153
April1st to 15thDay
13%5%2443445%6%45%
2151
16th to endDay
7%424434447%50%
2160
May1st to 15thDay
7%5%245%35%5%7%7%45%
2253
16th to endDay
6%425%6%46%6%6%8%40%
2431
June1st to 15thDay
7%5%36%7%5%7%8%7%9%30%
2340
16th to endDay
6%426%7%5%8%8%8%11%30%
2340
July1st to 15thDay
7%6%37%8%5%10%8%9%10%21%
2340
16th to endDay
8%5%38%8%5%9%8%8%10%23%
2337
August1st to 15thDay
9%6%38%8%5%7%8%8%11%23%
2160
16th to endDay
11%7%48%7%5%6%7%5%7%27%
2292
September1st to 15thDay
10%7%38%7%5%6%6%6%7%30%
2048
16th to endDay
7%5%37%6%46%5%5%7%41%
1894
October1st to 15thDay
7%42442445%7%51%
1815
16th to endDay
9%32332233460%
1829
November1st to 15thDay
7%5%1331336%8%54%
1582
16th to endDay
10%32342445%5%53%
1620
December1st to 15thDay
11%6%35%5%24347%46%
1620
16th to endDay
19%8%36%5%22336%37%
1728
January1st to 15thNight
12%6%24424347%46%
2262
16th to endNight
17%5%35%32344444%
2304
February1st to 15thNight
14%5%23323346%50%
2103
16th to endNight
15%5%25%5%23245%46%
1893
March1st to 15thNight
10%5%25%42445%8%45%
2142
16th to endNight
8%3245%24447%51%
2078
April1st to 15thNight
10%5%245%2446%7%46%
1797
16th to endNight
7%41331435%8%56%
1800
May1st to 15thNight
8%32343445%8%51%
1694
16th to endNight
44143345%7%11%48%
1682
June1st to 15thNight
5%2245%45%7%8%13%39%
1620
16th to endNight
5%3235%36%6%9%11%41%
1620
July1st to 15thNight
43245%37%6%8%15%39%
1620
16th to endNight
42245%36%8%10%12%37%
1827
August1st to 15thNight
43236%36%7%9%15%36%
1800
16th to endNight
7%6%36%7%45%5%7%11%33%
1910
September1st to 15thNight
8%415%6%45%6%7%11%38%
1899
16th to endNight
6%416%4345%6%8%46%
1903
October1st to 15thNight
5%32331347%8%56%
1815
16th to endNight
8%42342333459%
2039
November1st to 15thNight
7%424423347%57%
2276
16th to endNight
9%424323346%55%
2340
December1st to 15thNight
12%5%23425%447%47%
2340
16th to endNight
17%6%345%2345%6%39%
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
38%37%14%25%10%
1675
16th to endDay
40%35%16%23%11%
1920
February1st to 15thDay
37%27%18%23%11%
1752
16th to endDay
39%5%5%17%22%10%
1580
March1st to 15thDay
35%49%21%20%9%
1818
16th to endDay
34%412%18%18%10%
2154
April1st to 15thDay
38%37%18%21%9%
2151
16th to endDay
30%412%23%20%8%
2160
May1st to 15thDay
33%6%13%17%19%9%
2253
16th to endDay
36%7%13%21%17%2
2435
June1st to 15thDay
43%9%15%23%7%1
2340
16th to endDay
40%11%17%19%9%1
2340
July1st to 15thDay
47%12%21%13%3
2201
16th to endDay
47%11%21%15%3
2192
August1st to 15thDay
48%10%20%14%5%
2148
16th to endDay
50%10%15%13%7%1
2292
September1st to 15thDay
49%7%13%13%11%4
2048
16th to endDay
40%7%11%17%16%7%
1894
October1st to 15thDay
30%48%20%21%14%
1815
16th to endDay
28%2314%28%21%
1829
November1st to 15thDay
27%37%19%26%15%
1582
16th to endDay
30%46%18%22%17%
1620
December1st to 15thDay
37%39%19%20%8%
1620
16th to endDay
47%35%21%14%7%
1728
January1st to 15thNight
38%37%14%25%11%
2262
16th to endNight
42%36%13%23%10%
2304
February1st to 15thNight
34%26%18%22%14%
2112
16th to endNight
41%35%14%21%14%
1893
March1st to 15thNight
36%39%19%22%8%
2142
16th to endNight
32%39%22%20%11%
2078
April1st to 15thNight
36%48%16%22%11%
1797
16th to endNight
26%310%28%21%8%
1800
May1st to 15thNight
30%414%17%23%9%
1695
16th to endNight
27%7%18%25%16%5%
1684
June1st to 15thNight
30%11%21%23%11%1
1620
16th to endNight
29%11%24%21%11%1
1620
July1st to 15thNight
28%14%30%21%4
1530
16th to endNight
28%14%34%17%4
1709
August1st to 15thNight
31%13%32%17%4
1788
16th to endNight
40%10%22%16%7%2
1910
September1st to 15thNight
35%9%20%18%12%3
1899
16th to endNight
33%7%15%17%19%6%
1903
October1st to 15thNight
23%410%21%24%15%
1815
16th to endNight
29%2414%25%23%
2039
November1st to 15thNight
27%35%19%26%16%
2276
16th to endNight
29%36%17%22%20%
2340
December1st to 15thNight
36%38%20%23%7%
2340
16th to endNight
43%47%21%15%7%
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
15%13%38%18%10%3
90
16th to endDay
17%29%32%12%8%
96
February1st to 15thDay
8%30%24%25%11%
90
16th to endDay
12%22%38%24%2
81
March1st to 15thDay
14%18%45%15%31
108
16th to endDay
14%6%27%27%20%3
288
April1st to 15thDay
15%10%22%28%18%4
270
16th to endDay
9%6%21%30%26%6%
270
May1st to 15thDay
10%5%19%23%26%14%
288
16th to endDay
9%314%24%23%25%
331
June1st to 15thDay
13%16%22%26%28%
315
16th to endDay
9%16%18%25%37%
315
July1st to 15thDay
3114%27%51%
305
16th to endDay
7%1413%33%40%
326
August1st to 15thDay
10%417%28%38%
313
16th to endDay
12%1419%28%33%
332
September1st to 15thDay
13%211%20%28%23%
315
16th to endDay
8%19%30%33%16%
283
October1st to 15thDay
6%315%35%30%9%
255
16th to endDay
10%425%26%22%10%
220
November1st to 15thDay
21%125%35%11%5%
90
16th to endDay
5%11%43%26%8%4
90
December1st to 15thDay
16%15%36%18%11%1
90
16th to endDay
35%10%21%25%7%
96
January1st to 15thNight
16%10%30%32%9%
720
16th to endNight
20%11%30%28%8%
768
February1st to 15thNight
15%10%31%31%10%
704
16th to endNight
16%9%35%30%7%
631
March1st to 15thNight
14%9%33%31%10%
720
16th to endNight
9%8%28%34%16%1
734
April1st to 15thNight
12%8%19%40%18%
539
16th to endNight
9%321%39%24%1
540
May1st to 15thNight
10%317%37%27%4
540
16th to endNight
7%19%30%44%6%
563
June1st to 15thNight
6%17%28%45%11%
540
16th to endNight
6%1418%49%19%
540
July1st to 15thNight
4119%48%24%
510
16th to endNight
41217%50%23%
564
August1st to 15thNight
4112%51%29%
539
16th to endNight
8%2417%45%19%
573
September1st to 15thNight
11%17%20%42%16%
639
16th to endNight
10%19%33%37%8%
689
October1st to 15thNight
7%118%35%33%3
660
16th to endNight
11%322%32%27%3
704
November1st to 15thNight
9%5%23%36%21%3
700
16th to endNight
11%5%29%34%17%1
720
December1st to 15thNight
15%6%26%32%16%1
720
16th to endNight
20%7%28%29%12%1
768
Page generated at 2017-09-24 09:15:53. Version ac04

Copyright 2017 A. Danko


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