Krause's Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Krause's Observatory clear sky chart from 2005-11-05 to 2017-09-22.

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
60%
15924
21%
46991
17%
15885
64%
15885
30%
29291

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
45%
718
21%
2327
16%
716
54%
716
26%
1442
January16th to endNight
42%
768
24%
2451
17%
768
51%
768
28%
1470
February1st to 15thNight
45%
701
24%
2106
16%
700
54%
700
31%
1266
February16th to endNight
44%
631
25%
1844
14%
631
54%
631
32%
1129
March1st to 15thNight
52%
720
29%
1980
17%
720
62%
720
40%
1121
March16th to endNight
56%
768
27%
2112
20%
768
61%
768
41%
1205
April1st to 15thNight
57%
718
25%
1976
17%
718
64%
718
42%
1109
April16th to endNight
60%
720
27%
1842
18%
720
64%
720
44%
1080
May1st to 15thNight
72%
544
25%
1624
20%
544
76%
544
43%
882
May16th to endNight
76%
561
24%
1682
20%
561
77%
561
36%
995
June1st to 15thNight
70%
540
13%
1620
10%
540
70%
540
24%
1108
June16th to endNight
73%
540
9%
1620
8%
540
73%
540
22%
1156
July1st to 15thNight
72%
510
8%
1530
8%
510
72%
510
21%
1099
July16th to endNight
76%
564
7%
1595
6%
531
77%
531
22%
1123
August1st to 15thNight
75%
539
7%
1609
7%
536
75%
536
22%
1126
August16th to endNight
68%
705
11%
2028
11%
705
68%
705
22%
1442
September1st to 15thNight
66%
720
9%
1980
8%
720
66%
720
22%
1412
September16th to endNight
62%
685
15%
1892
14%
685
63%
685
20%
1374
October1st to 15thNight
68%
660
26%
1874
26%
660
69%
660
34%
1141
October16th to endNight
63%
704
28%
2112
28%
704
68%
704
34%
1263
November1st to 15thNight
59%
700
29%
2101
25%
700
67%
700
37%
1188
November16th to endNight
53%
720
28%
2250
21%
720
62%
720
32%
1317
December1st to 15thNight
51%
720
28%
2340
26%
720
57%
720
30%
1387
December16th to endNight
55%
768
24%
2496
22%
768
61%
768
30%
1456

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
8%5%26%6%46%6%6%8%37%
47872
Night
7%5%25%5%35%5%6%8%44%
47197
TransparencyDay
41%7%13%17%13%6%
47573
Night
35%7%15%20%14%6%
47000
SeeingDay
10%212%20%27%27%
5776
Night
10%217%32%28%8%
15932

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
11%6%35%5%345%5%7%41%
1611
16th to endDay
10%434425%46%7%46%
1770
February1st to 15thDay
12%5%25%5%35%35%5%45%
1750
16th to endDay
9%5%3443445%7%48%
1628
March1st to 15thDay
6%4245%3445%8%50%
1980
16th to endDay
6%5%26%5%2445%6%49%
2111
April1st to 15thDay
5%325%5%25%45%9%49%
1972
16th to endDay
5%3244345%7%8%50%
2119
May1st to 15thDay
5%314436%5%5%8%50%
2331
16th to endDay
6%425%6%46%7%7%9%38%
2431
June1st to 15thDay
9%5%37%8%5%8%7%7%9%27%
2340
16th to endDay
8%5%46%9%5%9%8%7%9%25%
2340
July1st to 15thDay
9%6%37%8%5%8%7%8%9%22%
2340
16th to endDay
9%6%5%8%9%5%8%8%8%9%19%
2465
August1st to 15thDay
6%7%38%9%6%8%8%7%10%21%
2340
16th to endDay
11%6%48%8%5%8%7%8%8%22%
2156
September1st to 15thDay
8%5%38%10%5%7%7%8%9%23%
1980
16th to endDay
11%7%38%9%5%7%7%7%7%23%
1881
October1st to 15thDay
8%5%26%8%45%5%5%9%38%
1755
16th to endDay
8%6%15%5%25%446%47%
1760
November1st to 15thDay
7%4145%2445%7%51%
1757
16th to endDay
8%5%245%35%447%47%
1707
December1st to 15thDay
11%6%25%4245%5%8%42%
1620
16th to endDay
6%5%25%5%25%46%9%44%
1728
January1st to 15thNight
10%7%35%4345%5%9%41%
2327
16th to endNight
13%425%4135%5%8%45%
2451
February1st to 15thNight
11%5%2443345%5%50%
2103
16th to endNight
8%5%245%245%5%7%47%
1844
March1st to 15thNight
6%32332446%6%56%
1980
16th to endNight
7%42432335%7%56%
2112
April1st to 15thNight
6%41332435%9%55%
1976
16th to endNight
6%323424447%55%
1842
May1st to 15thNight
42143235%6%9%55%
1624
16th to endNight
5%3245%246%6%7%50%
1682
June1st to 15thNight
9%425%5%46%8%7%9%35%
1620
16th to endNight
7%6%35%5%5%6%6%9%12%30%
1620
July1st to 15thNight
6%436%7%47%7%8%12%32%
1620
16th to endNight
45%25%7%5%8%9%8%10%32%
1703
August1st to 15thNight
4326%8%5%6%7%9%13%31%
1620
16th to endNight
8%5%36%6%36%7%8%11%33%
2028
September1st to 15thNight
8%6%26%6%36%5%7%12%33%
1980
16th to endNight
8%7%37%6%47%7%7%10%29%
1892
October1st to 15thNight
7%5%245%3447%8%47%
1874
16th to endNight
8%5%25%33445%6%50%
2112
November1st to 15thNight
5%425%42346%7%52%
2101
16th to endNight
7%434435%45%7%48%
2250
December1st to 15thNight
9%5%245%24447%47%
2340
16th to endNight
8%5%25%4345%5%8%45%
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
41%47%20%17%8%
1612
16th to endDay
36%47%18%21%10%
1770
February1st to 15thDay
40%46%13%20%14%
1752
16th to endDay
36%49%16%21%11%
1628
March1st to 15thDay
30%5%10%23%21%8%
1980
16th to endDay
34%312%20%18%9%
2112
April1st to 15thDay
30%6%11%20%23%8%
1972
16th to endDay
28%412%23%21%8%
2119
May1st to 15thDay
29%5%13%22%19%9%
2331
16th to endDay
37%6%15%20%14%3
2435
June1st to 15thDay
49%9%16%19%4
2340
16th to endDay
50%10%21%14%3
2340
July1st to 15thDay
51%12%22%12%1
2201
16th to endDay
53%12%20%12%1
2310
August1st to 15thDay
50%12%24%9%1
2327
16th to endDay
53%13%17%13%1
2156
September1st to 15thDay
53%12%18%11%4
1980
16th to endDay
53%9%12%13%7%2
1881
October1st to 15thDay
42%6%7%16%15%11%
1755
16th to endDay
36%48%14%23%12%
1760
November1st to 15thDay
31%39%22%22%10%
1757
16th to endDay
38%38%17%20%12%
1707
December1st to 15thDay
38%5%12%19%17%5%
1620
16th to endDay
35%5%13%20%16%8%
1728
January1st to 15thNight
40%410%20%15%8%
2327
16th to endNight
37%49%17%22%9%
2451
February1st to 15thNight
35%48%16%19%16%
2112
16th to endNight
35%5%11%16%22%9%
1844
March1st to 15thNight
27%412%25%21%8%
1980
16th to endNight
28%411%24%20%10%
2112
April1st to 15thNight
26%5%13%25%21%8%
1976
16th to endNight
27%412%25%22%7%
1842
May1st to 15thNight
25%5%17%25%18%7%
1625
16th to endNight
30%6%16%24%19%2
1684
June1st to 15thNight
41%9%20%22%5%
1620
16th to endNight
42%13%22%17%3
1620
July1st to 15thNight
42%13%27%13%2
1530
16th to endNight
40%14%30%12%2
1595
August1st to 15thNight
37%15%33%12%
1609
16th to endNight
41%13%24%17%2
2028
September1st to 15thNight
41%13%24%15%5%
1980
16th to endNight
47%10%16%18%5%2
1892
October1st to 15thNight
33%6%11%20%18%9%
1874
16th to endNight
34%48%14%27%10%
2112
November1st to 15thNight
30%49%23%21%9%
2101
16th to endNight
34%48%20%18%13%
2250
December1st to 15thNight
35%49%26%15%7%
2340
16th to endNight
35%414%22%14%8%
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
18%5%25%28%14%6%
90
16th to endDay
13%13%31%26%12%3
96
February1st to 15thDay
8%15%24%24%20%6%
90
16th to endDay
16%6%30%28%17%
129
March1st to 15thDay
9%428%33%21%2
270
16th to endDay
10%423%25%30%6%
288
April1st to 15thDay
7%5%18%34%25%8%
270
16th to endDay
7%17%21%35%16%
270
May1st to 15thDay
6%210%27%31%21%
288
16th to endDay
7%5%18%32%35%
331
June1st to 15thDay
15%314%27%39%
315
16th to endDay
6%210%23%55%
315
July1st to 15thDay
7%1321%65%
305
16th to endDay
11%39%23%51%
326
August1st to 15thDay
9%5%8%25%50%
313
16th to endDay
12%29%24%51%
332
September1st to 15thDay
14%1210%33%37%
315
16th to endDay
14%5%9%36%34%
278
October1st to 15thDay
13%9%27%36%13%
255
16th to endDay
8%21%27%34%7%
272
November1st to 15thDay
8%214%31%33%10%
265
16th to endDay
10%25%32%24%5%
177
December1st to 15thDay
5%440%35%13%1
90
16th to endDay
7%115%40%28%7%
96
January1st to 15thNight
14%6%28%32%16%1
720
16th to endNight
18%6%28%35%11%
768
February1st to 15thNight
14%430%37%12%
704
16th to endNight
11%6%31%42%7%
631
March1st to 15thNight
8%6%27%41%14%
720
16th to endNight
9%325%42%17%1
768
April1st to 15thNight
8%225%44%17%1
718
16th to endNight
8%223%42%22%
720
May1st to 15thNight
5%112%48%28%3
545
16th to endNight
7%6%35%41%8%
563
June1st to 15thNight
11%5%29%38%14%
540
16th to endNight
10%215%45%26%
540
July1st to 15thNight
9%210%42%35%
510
16th to endNight
5%210%53%27%
564
August1st to 15thNight
6%210%50%30%
539
16th to endNight
13%415%40%26%
705
September1st to 15thNight
11%5%20%40%20%
720
16th to endNight
12%6%26%41%11%
685
October1st to 15thNight
10%19%36%37%4
660
16th to endNight
13%114%37%30%3
704
November1st to 15thNight
7%221%40%25%2
700
16th to endNight
9%226%40%19%1
720
December1st to 15thNight
12%423%35%23%
720
16th to endNight
10%5%21%38%22%1
768
Page generated at 2017-09-23 06:43:45. Version ac04

Copyright 2017 A. Danko


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