DeepSkyEye Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the DeepSkyEye Observatory clear sky chart from 2005-11-05 to 2017-08-12.

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
20%
14935
11%
46319
5%
14890
27%
14890
12%
34899

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
9%
737
6%
2546
2%
733
16%
733
6%
2063
January16th to endNight
9%
768
5%
2496
1%
768
14%
768
5%
2117
February1st to 15thNight
8%
704
5%
2286
0%
701
13%
701
5%
1932
February16th to endNight
13%
631
8%
1979
2%
631
21%
631
9%
1566
March1st to 15thNight
15%
720
12%
2007
4%
720
22%
720
11%
1568
March16th to endNight
17%
768
14%
2112
4%
768
26%
768
14%
1552
April1st to 15thNight
16%
596
14%
1808
5%
596
24%
596
12%
1339
April16th to endNight
21%
540
14%
1620
5%
540
28%
540
15%
1153
May1st to 15thNight
18%
540
11%
1620
4%
540
25%
540
12%
1219
May16th to endNight
21%
561
10%
1498
4%
560
27%
560
15%
1133
June1st to 15thNight
22%
461
7%
1361
3%
461
27%
461
12%
1068
June16th to endNight
29%
360
8%
1260
5%
360
34%
360
12%
906
July1st to 15thNight
35%
343
10%
1193
9%
343
39%
343
15%
832
July16th to endNight
25%
565
7%
1579
6%
532
29%
532
14%
1234
August1st to 15thNight
36%
528
12%
1575
9%
524
38%
524
17%
1110
August16th to endNight
35%
525
16%
1597
8%
525
41%
525
20%
1082
September1st to 15thNight
34%
554
18%
1709
12%
554
41%
554
19%
1157
September16th to endNight
36%
657
23%
1815
13%
657
44%
657
25%
1179
October1st to 15thNight
27%
660
17%
1970
8%
660
34%
660
18%
1357
October16th to endNight
20%
704
14%
2130
5%
704
28%
704
16%
1508
November1st to 15thNight
24%
713
12%
2355
7%
713
31%
713
14%
1682
November16th to endNight
18%
750
11%
2520
5%
750
25%
750
9%
1869
December1st to 15thNight
14%
750
7%
2520
2%
750
19%
750
8%
2007
December16th to endNight
11%
800
7%
2763
2%
800
17%
800
5%
2266

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
23%10%46%5%23346%29%
47633
Night
22%10%47%5%34446%26%
46493
TransparencyDay
56%5%10%17%9%1
47325
Night
57%5%11%16%7%
46319
SeeingDay
28%22%25%15%6%1
6965
Night
25%24%23%18%6%
14935

By Month

Percentage Cloud Cover NE (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
20%18%6%11%8%3333414%
1385
16th to endDay
20%14%5%11%9%35%44415%
1728
February1st to 15thDay
16%17%9%13%10%3444411%
1575
16th to endDay
13%16%8%13%7%3333421%
1491
March1st to 15thDay
22%12%5%9%6%3233426%
1940
16th to endDay
19%12%7%7%5%23245%30%
2112
April1st to 15thDay
22%12%45%423335%32%
2137
16th to endDay
25%8%24323346%35%
2340
May1st to 15thDay
28%9%35%422245%30%
2332
16th to endDay
27%7%2442435%8%30%
2613
June1st to 15thDay
28%8%35%5%33335%28%
2608
16th to endDay
25%6%2432435%6%34%
2700
July1st to 15thDay
24%6%2432345%7%35%
2682
16th to endDay
24%7%245%2445%7%30%
2479
August1st to 15thDay
21%6%25%5%245%46%36%
2288
16th to endDay
19%5%145%2245%6%41%
2253
September1st to 15thDay
19%5%13323346%44%
1920
16th to endDay
19%6%24322246%45%
1815
October1st to 15thDay
22%8%15%323346%38%
1659
16th to endDay
25%9%35%5%3435%5%27%
1741
November1st to 15thDay
24%11%36%5%33435%27%
1500
16th to endDay
22%14%5%9%6%34335%19%
1440
December1st to 15thDay
27%15%6%7%6%24435%15%
1440
16th to endDay
25%14%7%9%6%4433414%
1455
January1st to 15thNight
19%14%6%10%8%35%446%15%
2546
16th to endNight
18%14%7%10%8%46%5%45%13%
2496
February1st to 15thNight
18%14%6%12%9%45%5%45%12%
2285
16th to endNight
15%13%5%10%8%46%5%5%5%19%
1979
March1st to 15thNight
20%10%5%8%7%34435%25%
1995
16th to endNight
18%10%47%6%3445%6%31%
2112
April1st to 15thNight
25%10%245%34346%27%
1808
16th to endNight
23%8%3433345%7%31%
1620
May1st to 15thNight
26%10%35%434346%27%
1620
16th to endNight
25%8%36%32345%6%29%
1496
June1st to 15thNight
30%9%5%5%423446%23%
1361
16th to endNight
26%8%345%24446%29%
1260
July1st to 15thNight
23%8%335%2346%8%29%
1263
16th to endNight
23%8%37%6%3345%6%24%
1686
August1st to 15thNight
21%8%35%42335%8%34%
1587
16th to endNight
17%9%3332345%7%39%
1597
September1st to 15thNight
21%7%2342335%6%38%
1709
16th to endNight
21%5%23313436%44%
1815
October1st to 15thNight
22%6%25%423445%37%
1970
16th to endNight
23%9%35%433346%32%
2130
November1st to 15thNight
21%8%36%5%345%6%7%26%
2355
16th to endNight
21%13%46%6%33446%25%
2520
December1st to 15thNight
25%13%5%6%5%345%5%7%16%
2520
16th to endNight
25%15%5%9%6%35%43416%
2763

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
72%5%10%8%2
1386
16th to endDay
69%48%14%2
1728
February1st to 15thDay
74%6%10%7%2
1578
16th to endDay
65%5%9%14%4
1491
March1st to 15thDay
62%310%14%7%1
1951
16th to endDay
56%39%18%10%1
2112
April1st to 15thDay
56%48%15%13%1
2137
16th to endDay
50%48%21%12%1
2340
May1st to 15thDay
57%5%7%18%9%2
2332
16th to endDay
53%5%13%17%9%
2617
June1st to 15thDay
58%49%16%8%1
2608
16th to endDay
50%7%11%17%11%1
2700
July1st to 15thDay
48%7%14%17%10%1
2524
16th to endDay
53%7%12%17%7%
2323
August1st to 15thDay
48%8%10%19%11%1
2275
16th to endDay
42%7%13%23%12%
2253
September1st to 15thDay
41%5%11%21%17%1
1920
16th to endDay
42%36%26%19%1
1815
October1st to 15thDay
48%310%23%12%1
1659
16th to endDay
57%5%9%17%9%
1741
November1st to 15thDay
58%411%17%7%1
1500
16th to endDay
67%411%11%4
1440
December1st to 15thDay
69%411%11%2
1440
16th to endDay
72%39%10%4
1455
January1st to 15thNight
66%6%13%10%3
2546
16th to endNight
71%6%9%9%2
2496
February1st to 15thNight
72%412%7%2
2286
16th to endNight
63%412%13%4
1979
March1st to 15thNight
61%410%14%8%
2007
16th to endNight
53%410%16%13%
2112
April1st to 15thNight
57%48%17%10%2
1808
16th to endNight
52%410%19%10%1
1620
May1st to 15thNight
59%39%18%9%
1620
16th to endNight
55%5%12%17%7%
1498
June1st to 15thNight
62%49%17%4
1361
16th to endNight
54%6%11%15%11%
1260
July1st to 15thNight
50%7%15%17%8%
1193
16th to endNight
57%8%11%16%41
1579
August1st to 15thNight
48%6%11%23%8%
1575
16th to endNight
43%8%11%24%11%
1597
September1st to 15thNight
46%5%7%25%13%1
1709
16th to endNight
41%37%27%19%1
1815
October1st to 15thNight
47%5%11%20%12%1
1970
16th to endNight
52%310%22%9%
2130
November1st to 15thNight
52%5%15%17%7%
2355
16th to endNight
58%5%15%14%6%
2520
December1st to 15thNight
64%6%14%11%2
2520
16th to endNight
68%6%10%10%3
2763

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
27%28%31%9%2
114
16th to endDay
28%29%30%9%1
256
February1st to 15thDay
25%29%30%11%2
236
16th to endDay
18%31%30%15%3
224
March1st to 15thDay
30%33%22%7%5%
270
16th to endDay
27%31%23%11%41
288
April1st to 15thDay
28%32%25%8%4
270
16th to endDay
24%27%30%11%41
270
May1st to 15thDay
35%25%22%11%41
288
16th to endDay
31%25%21%15%5%
514
June1st to 15thDay
27%21%25%18%6%
495
16th to endDay
29%20%23%18%7%1
495
July1st to 15thDay
29%14%24%20%9%2
475
16th to endDay
28%15%27%21%7%1
340
August1st to 15thDay
24%13%28%20%9%3
297
16th to endDay
23%12%28%19%12%4
268
September1st to 15thDay
23%12%28%23%8%3
255
16th to endDay
22%13%28%20%9%5%
254
October1st to 15thDay
27%15%24%18%8%5%
226
16th to endDay
29%25%25%13%6%
240
November1st to 15thDay
24%24%21%18%8%2
235
16th to endDay
28%26%24%14%5%1
240
December1st to 15thDay
34%26%24%11%2
240
16th to endDay
39%32%14%12%
175
January1st to 15thNight
26%32%26%11%3
737
16th to endNight
26%31%25%13%2
768
February1st to 15thNight
27%31%26%14%
704
16th to endNight
25%29%27%12%4
631
March1st to 15thNight
25%31%22%15%4
720
16th to endNight
22%30%25%15%5%
768
April1st to 15thNight
27%27%26%16%3
596
16th to endNight
24%24%25%17%6%
540
May1st to 15thNight
28%24%26%15%4
540
16th to endNight
25%23%24%21%4
561
June1st to 15thNight
27%21%22%21%6%
461
16th to endNight
27%19%18%24%10%
360
July1st to 15thNight
26%13%19%27%12%
343
16th to endNight
22%20%25%24%7%
565
August1st to 15thNight
23%14%20%29%11%
528
16th to endNight
20%13%24%26%13%1
525
September1st to 15thNight
24%14%24%23%12%1
554
16th to endNight
22%15%20%23%14%3
657
October1st to 15thNight
25%18%23%21%8%1
660
16th to endNight
25%22%27%19%4
704
November1st to 15thNight
21%23%24%19%9%
713
16th to endNight
27%30%19%16%6%
750
December1st to 15thNight
32%27%22%14%3
750
16th to endNight
33%31%20%13%1
800
Page generated at 2017-08-13 15:16:24. Version ac04

Copyright 2017 A. Danko


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