Praesepe Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Praesepe Observatory clear sky chart from 2005-11-05 to 2018-01-20.

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
49%
16061
25%
48475
18%
16016
56%
16016
31%
29033

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
27%
975
25%
2558
10%
970
38%
970
26%
1680
January16th to endNight
24%
982
25%
2558
8%
982
36%
982
27%
1706
February1st to 15thNight
28%
704
22%
2112
9%
701
39%
701
25%
1363
February16th to endNight
28%
631
26%
1893
11%
631
40%
631
25%
1191
March1st to 15thNight
31%
657
20%
2097
11%
657
39%
657
22%
1346
March16th to endNight
37%
576
24%
2025
15%
576
48%
576
27%
1189
April1st to 15thNight
38%
539
25%
1797
17%
539
51%
539
31%
1026
April16th to endNight
43%
540
26%
1800
20%
540
54%
540
30%
1017
May1st to 15thNight
49%
540
20%
1800
17%
540
56%
540
28%
1075
May16th to endNight
63%
562
24%
1661
21%
561
67%
561
36%
973
June1st to 15thNight
74%
540
24%
1440
19%
540
77%
540
43%
851
June16th to endNight
79%
540
26%
1440
22%
540
80%
540
46%
814
July1st to 15thNight
78%
510
21%
1410
19%
510
79%
510
39%
832
July16th to endNight
81%
564
21%
1619
24%
531
82%
531
39%
906
August1st to 15thNight
80%
539
19%
1788
23%
536
81%
536
35%
989
August16th to endNight
74%
573
23%
1910
27%
573
75%
573
30%
1119
September1st to 15thNight
64%
540
25%
1800
26%
540
67%
540
31%
1053
September16th to endNight
67%
685
33%
1948
28%
685
70%
685
41%
1101
October1st to 15thNight
61%
720
32%
2100
27%
720
65%
720
42%
1154
October16th to endNight
54%
768
36%
2304
26%
768
63%
768
38%
1281
November1st to 15thNight
51%
760
28%
2417
22%
760
60%
760
34%
1350
November16th to endNight
42%
780
29%
2535
20%
780
54%
780
30%
1452
December1st to 15thNight
36%
796
24%
2551
13%
796
47%
796
25%
1585
December16th to endNight
29%
1040
20%
2912
10%
1040
38%
1040
23%
1980

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
13%5%245%3445%7%43%
49039
Night
12%5%2442445%7%49%
48670
TransparencyDay
39%6%10%20%17%4
48738
Night
34%5%10%21%21%6%
48476
SeeingDay
12%5%19%25%23%12%
5986
Night
14%7%22%29%21%3
16062

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
19%7%2442333443%
1708
16th to endDay
18%7%23422335%45%
1770
February1st to 15thDay
17%7%3432443443%
1750
16th to endDay
20%6%25%422335%41%
1580
March1st to 15thDay
19%8%26%424445%37%
1872
16th to endDay
14%5%26%5%3435%7%41%
2197
April1st to 15thDay
13%424435%446%44%
2151
16th to endDay
12%5%345%2345%6%46%
2160
May1st to 15thDay
15%5%25%5%35%45%6%39%
2151
16th to endDay
9%5%25%6%36%5%7%8%38%
2447
June1st to 15thDay
5%5%25%5%46%6%6%9%41%
2520
16th to endDay
7%2245%45%5%6%9%45%
2520
July1st to 15thDay
8%5%346%36%6%8%12%34%
2462
16th to endDay
9%415%5%37%7%8%10%36%
2439
August1st to 15thDay
8%4246%46%5%6%9%41%
2160
16th to endDay
12%5%25%5%36%5%6%9%37%
2292
September1st to 15thDay
9%425%6%35%6%6%8%41%
2160
16th to endDay
11%41443435%7%50%
1998
October1st to 15thDay
9%424323346%54%
1857
16th to endDay
14%31231222460%
1920
November1st to 15thDay
12%42441333357%
1771
16th to endDay
17%414323235%51%
1755
December1st to 15thDay
20%8%26%5%2323340%
1735
16th to endDay
19%7%24423436%40%
1664
January1st to 15thNight
17%6%24412235%46%
2558
16th to endNight
18%6%24313345%44%
2558
February1st to 15thNight
17%7%35%32333446%
2103
16th to endNight
15%7%34423336%45%
1893
March1st to 15thNight
16%5%24434447%41%
2097
16th to endNight
14%424323345%49%
2025
April1st to 15thNight
12%42432335%7%49%
1797
16th to endNight
9%5%25%424446%51%
1800
May1st to 15thNight
13%5%24424348%47%
1799
16th to endNight
7%324435%5%6%8%49%
1660
June1st to 15thNight
33144345%6%12%50%
1440
16th to endNight
3223225%46%10%55%
1440
July1st to 15thNight
5%2145%35%6%7%12%45%
1494
16th to endNight
5%213435%5%8%13%47%
1729
August1st to 15thNight
42135%35%5%7%11%50%
1800
16th to endNight
6%415%435%5%7%10%44%
1910
September1st to 15thNight
9%425%43445%8%48%
1800
16th to endNight
10%31332335%6%56%
1948
October1st to 15thNight
8%412313347%58%
2100
16th to endNight
13%31231323459%
2304
November1st to 15thNight
11%424323445%54%
2417
16th to endNight
15%5%22323235%53%
2535
December1st to 15thNight
16%7%24323346%45%
2551
16th to endNight
18%8%25%423345%40%
2912

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
45%26%20%21%4
1709
16th to endDay
42%36%21%21%4
1770
February1st to 15thDay
43%38%22%16%5%
1752
16th to endDay
45%37%19%19%4
1580
March1st to 15thDay
49%48%18%13%6%
1872
16th to endDay
42%6%10%21%18%1
2199
April1st to 15thDay
39%5%9%22%18%5%
2151
16th to endDay
38%5%8%21%23%1
2160
May1st to 15thDay
44%7%9%16%18%4
2151
16th to endDay
41%8%14%22%11%1
2451
June1st to 15thDay
37%8%11%23%17%1
2520
16th to endDay
33%8%15%20%19%3
2520
July1st to 15thDay
37%11%17%20%8%4
2317
16th to endDay
37%9%18%22%10%1
2286
August1st to 15thDay
36%9%15%22%12%3
2148
16th to endDay
40%8%15%20%11%2
2292
September1st to 15thDay
38%8%11%20%13%7%
2160
16th to endDay
32%5%11%21%20%9%
1998
October1st to 15thDay
30%5%10%22%21%10%
1857
16th to endDay
29%2321%32%10%
1920
November1st to 15thDay
32%36%20%28%8%
1771
16th to endDay
37%26%20%25%7%
1755
December1st to 15thDay
48%37%18%15%6%
1735
16th to endDay
47%310%18%16%3
1664
January1st to 15thNight
41%36%20%22%5%
2558
16th to endNight
42%35%18%22%7%
2558
February1st to 15thNight
42%36%21%21%4
2112
16th to endNight
40%36%20%21%7%
1893
March1st to 15thNight
42%49%17%17%8%
2097
16th to endNight
37%49%22%22%3
2025
April1st to 15thNight
33%48%23%21%8%
1797
16th to endNight
33%49%22%24%5%
1800
May1st to 15thNight
36%5%11%20%21%5%
1800
16th to endNight
30%6%15%26%18%2
1662
June1st to 15thNight
26%7%15%28%21%1
1440
16th to endNight
22%7%14%27%23%4
1440
July1st to 15thNight
26%8%18%28%13%4
1410
16th to endNight
24%9%20%30%14%1
1619
August1st to 15thNight
25%10%20%24%14%4
1788
16th to endNight
31%9%17%21%15%4
1910
September1st to 15thNight
33%6%11%22%17%8%
1800
16th to endNight
28%49%22%25%9%
1948
October1st to 15thNight
26%48%23%24%12%
2100
16th to endNight
30%3316%32%13%
2304
November1st to 15thNight
31%37%20%25%10%
2417
16th to endNight
35%36%17%27%10%
2535
December1st to 15thNight
40%47%21%18%6%
2551
16th to endNight
46%39%18%18%4
2912

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
21%16%37%14%10%
135
16th to endDay
21%23%38%8%43
109
February1st to 15thDay
20%20%42%12%23
90
16th to endDay
25%14%37%22%
81
March1st to 15thDay
30%16%35%15%2
90
16th to endDay
14%14%29%28%11%1
183
April1st to 15thDay
17%16%30%22%11%2
270
16th to endDay
17%10%22%31%15%2
270
May1st to 15thDay
19%6%23%32%10%6%
288
16th to endDay
11%323%28%19%13%
358
June1st to 15thDay
7%116%29%27%17%
495
16th to endDay
6%113%29%33%16%
495
July1st to 15thDay
5%19%32%33%17%
475
16th to endDay
6%7%21%35%28%
488
August1st to 15thDay
10%15%20%39%22%
313
16th to endDay
16%26%20%31%22%
332
September1st to 15thDay
10%29%24%31%20%
315
16th to endDay
9%111%28%31%16%
314
October1st to 15thDay
7%322%27%31%7%
192
16th to endDay
12%6%31%30%12%6%
144
November1st to 15thDay
18%436%29%9%1
135
16th to endDay
18%8%28%24%15%4
135
December1st to 15thDay
21%11%38%17%8%2
135
16th to endDay
17%18%36%22%4
144
January1st to 15thNight
20%17%29%24%7%
975
16th to endNight
20%12%39%24%3
982
February1st to 15thNight
20%13%33%26%5%
704
16th to endNight
19%16%33%27%3
631
March1st to 15thNight
19%12%30%31%5%
657
16th to endNight
18%7%32%26%13%
576
April1st to 15thNight
12%10%35%28%11%1
539
16th to endNight
11%9%30%31%15%1
540
May1st to 15thNight
14%5%24%36%15%3
540
16th to endNight
7%118%36%31%4
563
June1st to 15thNight
5%10%37%37%7%
540
16th to endNight
39%30%46%10%
540
July1st to 15thNight
47%29%46%11%
510
16th to endNight
4426%47%16%
564
August1st to 15thNight
5%425%47%16%
539
16th to endNight
9%15%24%47%11%
573
September1st to 15thNight
11%111%27%41%5%
540
16th to endNight
12%111%32%35%5%
685
October1st to 15thNight
10%319%32%30%4
720
16th to endNight
15%6%20%30%24%2
768
November1st to 15thNight
13%6%24%33%18%2
760
16th to endNight
18%8%28%27%15%1
780
December1st to 15thNight
21%9%28%30%9%
796
16th to endNight
24%14%27%26%6%
1040
Page generated at 2018-01-21 11:19:25. Version ac04

Copyright 2018 A. Danko


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