EverStaR Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the EverStaR Observatory clear sky chart from 2005-11-05 to 2017-12-04.

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
41%
16207
23%
47952
14%
16160
49%
16160
31%
28910

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
30%
900
22%
2327
8%
895
40%
895
32%
1472
January16th to endNight
26%
960
25%
2496
9%
960
37%
960
32%
1595
February1st to 15thNight
22%
880
16%
2288
6%
876
29%
876
24%
1609
February16th to endNight
25%
664
24%
1926
8%
664
37%
664
29%
1191
March1st to 15thNight
30%
540
22%
1980
11%
540
45%
540
25%
1149
March16th to endNight
24%
576
15%
2112
9%
576
33%
576
18%
1384
April1st to 15thNight
33%
539
21%
1855
13%
539
46%
539
27%
1071
April16th to endNight
31%
540
20%
1707
13%
540
44%
540
24%
1108
May1st to 15thNight
38%
540
19%
1620
15%
540
46%
540
27%
1053
May16th to endNight
45%
563
19%
1664
14%
561
51%
561
32%
1007
June1st to 15thNight
61%
540
20%
1440
12%
540
65%
540
42%
844
June16th to endNight
59%
540
25%
1462
14%
540
64%
540
53%
779
July1st to 15thNight
70%
510
17%
1530
14%
510
72%
510
41%
853
July16th to endNight
72%
564
24%
1594
23%
531
76%
531
44%
839
August1st to 15thNight
77%
539
25%
1610
29%
536
79%
536
43%
863
August16th to endNight
70%
573
28%
1812
31%
573
73%
573
39%
980
September1st to 15thNight
60%
540
26%
1854
27%
540
65%
540
32%
1052
September16th to endNight
61%
537
29%
1980
27%
537
68%
537
33%
1028
October1st to 15thNight
44%
711
27%
2151
18%
711
50%
711
34%
1272
October16th to endNight
39%
768
30%
2304
15%
768
51%
768
37%
1273
November1st to 15thNight
36%
828
27%
2348
12%
828
48%
828
36%
1352
November16th to endNight
31%
975
26%
2698
10%
975
44%
975
33%
1624
December1st to 15thNight
28%
920
18%
2575
7%
920
38%
920
25%
1712
December16th to endNight
27%
960
21%
2619
7%
960
38%
960
23%
1800

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
12%6%25%42445%7%44%
48523
Night
10%5%2442445%6%49%
48147
TransparencyDay
38%6%13%25%14%2
48223
Night
34%5%12%26%17%3
47952
SeeingDay
12%8%26%30%17%3
6139
Night
13%8%32%32%12%1
16207

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%7%35%5%2434447%
1611
16th to endDay
11%8%46%424346%42%
1728
February1st to 15thDay
12%9%6%6%333346%40%
1575
16th to endDay
12%9%35%42445%6%40%
1554
March1st to 15thDay
11%10%47%5%25%45%7%36%
1980
16th to endDay
20%10%46%32434434%
2110
April1st to 15thDay
15%7%35%42435%5%41%
2091
16th to endDay
19%8%36%5%34446%34%
2250
May1st to 15thDay
17%8%45%5%24445%36%
2331
16th to endDay
15%5%245%35%46%8%37%
2448
June1st to 15thDay
8%5%24425%5%7%9%43%
2520
16th to endDay
5%2134345%6%10%51%
2493
July1st to 15thDay
8%4134345%7%9%46%
2340
16th to endDay
6%215%5%26%6%7%9%47%
2466
August1st to 15thDay
7%324425%5%6%10%46%
2340
16th to endDay
9%4244345%48%48%
2390
September1st to 15thDay
12%5%245%23346%49%
2103
16th to endDay
8%315%42346%8%50%
1977
October1st to 15thDay
14%6%2431325%6%49%
1800
16th to endDay
11%5%23423345%53%
1920
November1st to 15thDay
10%5%14323337%53%
1838
16th to endDay
14%5%24422336%50%
1589
December1st to 15thDay
14%9%34433346%40%
1467
16th to endDay
14%8%46%42345%6%38%
1602
January1st to 15thNight
8%6%25%424446%50%
2327
16th to endNight
8%7%35%5%24345%49%
2496
February1st to 15thNight
11%9%46%6%34446%39%
2278
16th to endNight
11%6%35%423346%47%
1926
March1st to 15thNight
11%7%34423446%47%
1980
16th to endNight
19%7%35%41435%7%37%
2112
April1st to 15thNight
10%6%2442335%5%50%
1855
16th to endNight
18%6%24423345%43%
1707
May1st to 15thNight
13%6%24425%45%7%43%
1619
16th to endNight
11%42432345%8%48%
1662
June1st to 15thNight
5%2133345%5%9%53%
1440
16th to endNight
411331346%11%59%
1462
July1st to 15thNight
6%2133245%7%9%51%
1620
16th to endNight
4213325%5%7%9%53%
1702
August1st to 15thNight
3212425%46%10%54%
1620
16th to endNight
6%41342335%459%
1812
September1st to 15thNight
9%4244235%5%5%51%
1854
16th to endNight
6%32342445%6%54%
1980
October1st to 15thNight
14%413323335%53%
2151
16th to endNight
10%413213245%58%
2304
November1st to 15thNight
9%5%14323246%55%
2348
16th to endNight
12%6%23322336%52%
2698
December1st to 15thNight
13%8%35%5%24446%42%
2575
16th to endNight
14%9%47%424345%40%
2619

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%313%24%16%1
1612
16th to endDay
42%415%24%11%1
1728
February1st to 15thDay
45%5%14%23%8%1
1576
16th to endDay
42%5%13%24%11%2
1554
March1st to 15thDay
45%6%11%23%10%1
1980
16th to endDay
53%412%19%8%1
2112
April1st to 15thDay
43%5%11%23%15%
2091
16th to endDay
51%5%11%19%11%
2250
May1st to 15thDay
48%6%11%22%11%
2331
16th to endDay
43%8%15%20%10%1
2452
June1st to 15thDay
34%8%15%26%14%1
2520
16th to endDay
26%8%17%28%17%2
2493
July1st to 15thDay
32%8%18%26%12%2
2201
16th to endDay
28%6%15%32%14%1
2311
August1st to 15thDay
30%8%15%27%16%1
2326
16th to endDay
32%7%12%26%16%5%
2390
September1st to 15thDay
36%5%10%24%17%5%
2103
16th to endDay
30%6%11%30%19%1
1977
October1st to 15thDay
35%49%25%19%4
1800
16th to endDay
32%312%26%21%4
1920
November1st to 15thDay
31%5%11%25%19%5%
1838
16th to endDay
37%39%29%19%
1589
December1st to 15thDay
44%415%23%9%
1467
16th to endDay
45%5%13%21%11%2
1602
January1st to 15thNight
35%415%24%17%1
2327
16th to endNight
36%413%27%16%2
2496
February1st to 15thNight
45%5%12%22%12%1
2288
16th to endNight
38%312%24%18%2
1926
March1st to 15thNight
37%411%24%16%4
1980
16th to endNight
47%413%22%9%2
2112
April1st to 15thNight
35%49%27%19%2
1855
16th to endNight
43%411%23%16%1
1707
May1st to 15thNight
40%6%12%22%16%1
1620
16th to endNight
33%6%17%25%13%2
1664
June1st to 15thNight
25%7%16%31%16%2
1440
16th to endNight
18%5%15%33%22%3
1462
July1st to 15thNight
26%6%14%31%16%3
1530
16th to endNight
22%7%14%32%20%2
1594
August1st to 15thNight
21%8%15%33%17%3
1610
16th to endNight
27%48%27%24%7%
1812
September1st to 15thNight
32%6%10%24%19%7%
1854
16th to endNight
28%5%10%29%22%3
1980
October1st to 15thNight
33%47%24%22%7%
2151
16th to endNight
28%49%28%24%4
2304
November1st to 15thNight
30%412%23%22%7%
2348
16th to endNight
34%39%30%19%2
2698
December1st to 15thNight
42%5%13%26%11%
2575
16th to endNight
46%412%20%12%3
2619

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
24%18%40%13%3
90
16th to endDay
17%17%44%15%31
96
February1st to 15thDay
6%26%41%23%2
90
16th to endDay
14%24%37%17%6%
81
March1st to 15thDay
13%22%52%10%11
90
16th to endDay
26%17%33%21%1
96
April1st to 15thDay
17%14%36%23%8%
210
16th to endDay
25%14%32%19%7%1
360
May1st to 15thDay
18%10%34%23%10%1
468
16th to endDay
18%8%33%25%11%2
517
June1st to 15thDay
9%6%24%35%19%4
495
16th to endDay
6%430%35%19%3
495
July1st to 15thDay
10%417%39%24%4
475
16th to endDay
5%112%42%31%6%
515
August1st to 15thDay
6%12%41%33%5%
493
16th to endDay
11%314%34%28%8%
430
September1st to 15thDay
7%117%39%27%6%
258
16th to endDay
10%222%43%13%8%
135
October1st to 15thDay
14%7%35%28%7%6%
135
16th to endDay
9%11%45%24%9%
144
November1st to 15thDay
11%13%25%32%13%3
135
16th to endDay
27%13%34%17%6%
135
December1st to 15thDay
17%18%41%16%44
100
16th to endDay
20%25%33%18%2
96
January1st to 15thNight
11%14%39%27%5%1
900
16th to endNight
11%13%43%27%4
960
February1st to 15thNight
15%12%41%26%3
880
16th to endNight
14%14%43%23%4
664
March1st to 15thNight
15%12%36%27%7%
540
16th to endNight
22%12%38%22%4
576
April1st to 15thNight
14%12%36%30%5%
539
16th to endNight
20%9%34%27%7%
540
May1st to 15thNight
15%7%34%30%10%
540
16th to endNight
13%5%31%34%12%2
563
June1st to 15thNight
5%324%46%18%
540
16th to endNight
4131%44%16%1
540
July1st to 15thNight
8%115%48%24%2
510
16th to endNight
6%13%46%31%1
564
August1st to 15thNight
419%48%35%1
539
16th to endNight
6%115%38%33%4
573
September1st to 15thNight
10%418%39%23%3
540
16th to endNight
8%321%41%21%3
537
October1st to 15thNight
16%5%30%29%15%2
711
16th to endNight
12%10%36%30%10%
768
November1st to 15thNight
11%10%37%27%11%
828
16th to endNight
17%13%36%27%5%
975
December1st to 15thNight
18%11%37%25%5%
920
16th to endNight
18%12%36%28%4
960
Page generated at 2017-12-05 09:18:59. Version ac04

Copyright 2017 A. Danko


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