Enterprise
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Enterprise clear sky chart from 2005-11-05 to 2017-09-21.

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
54%
15387
23%
47013
17%
15343
60%
15343
30%
28791

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
35%
720
23%
2318
12%
716
49%
716
26%
1412
January16th to endNight
32%
768
26%
2304
13%
768
44%
768
26%
1468
February1st to 15thNight
38%
704
27%
2109
14%
700
51%
700
30%
1264
February16th to endNight
34%
631
25%
1893
11%
631
45%
631
28%
1188
March1st to 15thNight
40%
720
24%
2115
13%
720
49%
720
32%
1262
March16th to endNight
47%
768
25%
2112
15%
768
54%
768
35%
1266
April1st to 15thNight
52%
554
26%
1812
22%
554
59%
554
33%
1003
April16th to endNight
56%
540
27%
1800
24%
540
65%
540
37%
971
May1st to 15thNight
60%
539
24%
1642
19%
539
66%
539
37%
931
May16th to endNight
67%
561
21%
1682
18%
561
70%
561
34%
1025
June1st to 15thNight
70%
540
14%
1620
12%
540
71%
540
27%
1081
June16th to endNight
75%
540
16%
1620
15%
540
76%
540
27%
1059
July1st to 15thNight
77%
510
11%
1530
10%
510
77%
510
26%
1019
July16th to endNight
76%
564
11%
1639
12%
531
76%
531
26%
1077
August1st to 15thNight
75%
539
12%
1788
14%
536
75%
536
21%
1210
August16th to endNight
66%
573
15%
1910
19%
573
66%
573
20%
1329
September1st to 15thNight
65%
663
15%
1923
14%
663
66%
663
23%
1342
September16th to endNight
60%
681
23%
1881
17%
681
64%
681
28%
1243
October1st to 15thNight
63%
660
33%
1815
24%
660
70%
660
43%
1018
October16th to endNight
56%
704
35%
2048
29%
704
63%
704
40%
1136
November1st to 15thNight
55%
700
31%
2276
28%
700
64%
700
37%
1221
November16th to endNight
46%
720
29%
2340
22%
720
58%
720
35%
1265
December1st to 15thNight
43%
720
26%
2340
20%
720
53%
720
29%
1396
December16th to endNight
38%
768
21%
2496
16%
768
46%
768
23%
1605

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
11%5%25%5%35%5%6%8%41%
47833
Night
10%42443446%8%46%
47220
TransparencyDay
39%7%11%16%16%7%
47539
Night
34%7%12%16%19%9%
47018
SeeingDay
11%414%23%25%19%
5306
Night
12%421%30%25%5%
15390

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
13%5%25%434446%45%
1617
16th to endDay
18%5%24324445%45%
1920
February1st to 15thDay
13%5%25%423447%47%
1750
16th to endDay
15%5%2442435%6%44%
1580
March1st to 15thDay
12%42442445%8%45%
1845
16th to endDay
12%425%42435%7%47%
2111
April1st to 15thDay
13%5%24424447%46%
2145
16th to endDay
7%434424447%51%
2160
May1st to 15thDay
8%3245%25%5%5%8%46%
2307
16th to endDay
6%5%245%45%6%7%8%43%
2431
June1st to 15thDay
8%5%36%6%46%7%7%11%32%
2340
16th to endDay
6%337%6%5%7%6%7%11%34%
2340
July1st to 15thDay
9%5%36%8%49%8%8%10%25%
2340
16th to endDay
8%5%37%8%47%6%8%12%27%
2413
August1st to 15thDay
10%7%37%8%5%7%7%8%10%24%
2160
16th to endDay
11%7%38%7%47%6%7%9%27%
2292
September1st to 15thDay
10%5%26%7%5%7%6%6%8%32%
2024
16th to endDay
10%5%26%5%3446%8%41%
1872
October1st to 15thDay
9%5%25%32346%7%50%
1815
16th to endDay
10%313323246%59%
1821
November1st to 15thDay
8%422314447%55%
1582
16th to endDay
12%424423345%52%
1620
December1st to 15thDay
14%5%2442445%6%45%
1620
16th to endDay
21%7%36%423337%37%
1728
January1st to 15thNight
12%6%2442445%6%45%
2318
16th to endNight
17%6%34323345%45%
2304
February1st to 15thNight
14%423423346%49%
2103
16th to endNight
14%6%14424345%46%
1893
March1st to 15thNight
10%425%5%2346%6%48%
2115
16th to endNight
9%424424347%52%
2112
April1st to 15thNight
10%42442346%8%49%
1812
16th to endNight
7%42332445%7%54%
1800
May1st to 15thNight
8%41432445%7%53%
1641
16th to endNight
5%4145%345%7%9%47%
1682
June1st to 15thNight
6%435%5%45%6%7%11%39%
1620
16th to endNight
5%425%5%46%5%8%11%40%
1620
July1st to 15thNight
6%4245%46%7%10%12%35%
1620
16th to endNight
34345%37%6%9%13%37%
1751
August1st to 15thNight
6%335%6%38%6%10%14%30%
1800
16th to endNight
9%5%26%6%46%6%8%10%33%
1910
September1st to 15thNight
9%5%26%5%46%6%6%9%36%
1923
16th to endNight
8%5%35%6%3445%7%43%
1881
October1st to 15thNight
7%31342346%7%55%
1815
16th to endNight
9%5%2342234458%
2048
November1st to 15thNight
7%414422446%56%
2276
16th to endNight
11%323323345%56%
2340
December1st to 15thNight
12%5%245%2345%6%47%
2340
16th to endNight
17%6%25%5%2435%6%40%
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
39%48%13%24%10%
1618
16th to endDay
40%45%14%24%10%
1920
February1st to 15thDay
37%47%15%24%10%
1752
16th to endDay
39%5%6%16%22%10%
1580
March1st to 15thDay
36%410%18%22%8%
1845
16th to endDay
37%5%10%17%20%8%
2112
April1st to 15thDay
37%5%7%18%19%10%
2145
16th to endDay
32%5%10%21%21%7%
2160
May1st to 15thDay
34%6%11%18%21%7%
2307
16th to endDay
34%10%13%23%15%3
2435
June1st to 15thDay
42%11%15%20%9%1
2340
16th to endDay
40%12%17%16%11%1
2340
July1st to 15thDay
46%15%19%12%4
2201
16th to endDay
44%12%22%14%5%
2262
August1st to 15thDay
50%13%15%14%4
2148
16th to endDay
50%11%15%12%7%1
2292
September1st to 15thDay
46%10%15%12%11%3
2024
16th to endDay
38%8%12%16%17%6%
1872
October1st to 15thDay
32%410%18%21%12%
1815
16th to endDay
27%36%13%30%19%
1821
November1st to 15thDay
27%48%19%25%14%
1582
16th to endDay
32%37%17%22%16%
1620
December1st to 15thDay
38%5%9%18%20%8%
1620
16th to endDay
48%46%19%14%7%
1728
January1st to 15thNight
39%47%13%25%10%
2318
16th to endNight
41%46%12%24%10%
2304
February1st to 15thNight
36%36%16%22%14%
2112
16th to endNight
38%46%13%20%16%
1893
March1st to 15thNight
34%5%9%18%22%9%
2115
16th to endNight
32%410%19%22%11%
2112
April1st to 15thNight
31%410%16%23%13%
1812
16th to endNight
28%5%10%25%20%10%
1800
May1st to 15thNight
29%5%14%15%24%10%
1642
16th to endNight
30%9%17%19%15%7%
1684
June1st to 15thNight
36%11%18%19%12%1
1620
16th to endNight
34%12%18%20%11%1
1620
July1st to 15thNight
32%16%28%16%41
1530
16th to endNight
33%15%27%17%6%
1639
August1st to 15thNight
36%16%24%17%31
1788
16th to endNight
41%13%17%13%10%2
1910
September1st to 15thNight
41%12%15%14%10%5%
1923
16th to endNight
39%7%12%13%20%6%
1881
October1st to 15thNight
26%410%20%23%14%
1815
16th to endNight
29%25%13%26%21%
2048
November1st to 15thNight
28%35%16%26%17%
2276
16th to endNight
29%48%14%23%19%
2340
December1st to 15thNight
35%5%7%18%24%7%
2340
16th to endNight
43%5%8%18%16%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
17%14%32%20%7%7%
90
16th to endDay
15%21%32%21%7%1
96
February1st to 15thDay
10%24%35%21%8%
90
16th to endDay
12%16%38%27%6%
81
March1st to 15thDay
12%13%38%26%8%
135
16th to endDay
12%6%27%30%20%3
288
April1st to 15thDay
15%9%21%26%25%1
270
16th to endDay
11%320%30%25%8%
270
May1st to 15thDay
10%5%16%29%23%13%
288
16th to endDay
9%210%29%22%25%
331
June1st to 15thDay
14%16%18%28%30%
315
16th to endDay
9%419%31%34%
315
July1st to 15thDay
5%29%38%43%
305
16th to endDay
7%215%30%44%
326
August1st to 15thDay
11%317%34%33%
313
16th to endDay
10%25%19%29%32%
332
September1st to 15thDay
13%19%21%29%23%
315
16th to endDay
11%19%28%33%15%
275
October1st to 15thDay
10%312%36%28%9%
255
16th to endDay
10%322%26%28%8%
250
November1st to 15thDay
22%28%27%13%7%
90
16th to endDay
7%8%36%30%10%6%
90
December1st to 15thDay
22%11%31%24%10%1
90
16th to endDay
31%10%15%26%15%1
96
January1st to 15thNight
15%11%32%29%9%
720
16th to endNight
19%11%33%26%8%
768
February1st to 15thNight
17%8%31%32%10%
704
16th to endNight
16%8%37%32%5%
631
March1st to 15thNight
13%9%32%34%10%
720
16th to endNight
11%7%29%34%16%
768
April1st to 15thNight
13%5%23%37%18%
554
16th to endNight
9%325%35%24%1
540
May1st to 15thNight
8%222%39%23%3
540
16th to endNight
7%14%31%39%5%
563
June1st to 15thNight
7%8%28%46%7%
540
16th to endNight
6%6%25%47%13%
540
July1st to 15thNight
8%323%45%19%
510
16th to endNight
6%223%48%18%
564
August1st to 15thNight
8%417%49%20%
539
16th to endNight
12%25%19%43%16%
573
September1st to 15thNight
10%19%26%38%12%
663
16th to endNight
11%112%36%32%4
681
October1st to 15thNight
10%119%35%30%3
660
16th to endNight
10%422%29%29%2
704
November1st to 15thNight
10%424%37%19%3
700
16th to endNight
12%6%30%32%17%
720
December1st to 15thNight
14%6%29%33%13%1
720
16th to endNight
21%5%28%30%12%
768
Page generated at 2017-09-22 06:35:33. Version ac04

Copyright 2017 A. Danko


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