Schreder Planetarium
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Schreder Planetarium clear sky chart from 2005-11-05 to 2017-04-30.

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
62%
14693
27%
45677
22%
14655
67%
14655
38%
24912

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
55%
718
19%
2470
17%
716
61%
716
27%
1455
January16th to endNight
51%
768
25%
2496
22%
768
57%
768
26%
1539
February1st to 15thNight
51%
697
22%
2288
21%
696
56%
696
25%
1453
February16th to endNight
50%
632
22%
1945
18%
632
57%
632
26%
1238
March1st to 15thNight
46%
720
15%
2018
11%
720
52%
720
24%
1383
March16th to endNight
48%
768
19%
2088
12%
768
53%
768
29%
1355
April1st to 15thNight
45%
719
21%
1799
8%
719
51%
719
31%
1190
April16th to endNight
55%
706
25%
1780
12%
706
59%
706
47%
1004
May1st to 15thNight
56%
445
29%
1435
19%
445
65%
445
47%
688
May16th to endNight
60%
342
20%
1368
19%
342
67%
342
32%
675
June1st to 15thNight
64%
330
24%
1320
26%
330
75%
330
38%
605
June16th to endNight
73%
330
30%
1320
37%
330
81%
330
59%
474
July1st to 15thNight
90%
310
34%
1240
47%
310
92%
310
67%
406
July16th to endNight
89%
462
37%
1408
38%
430
91%
430
75%
519
August1st to 15thNight
91%
493
40%
1476
34%
490
93%
490
76%
578
August16th to endNight
90%
665
43%
1715
29%
665
92%
665
84%
734
September1st to 15thNight
86%
660
45%
1650
29%
660
90%
660
86%
715
September16th to endNight
79%
656
40%
1806
34%
656
83%
656
67%
816
October1st to 15thNight
66%
660
32%
1980
28%
660
75%
660
50%
974
October16th to endNight
67%
704
33%
2112
32%
704
73%
704
43%
1117
November1st to 15thNight
66%
700
25%
2235
24%
700
70%
700
35%
1252
November16th to endNight
59%
720
20%
2520
21%
720
62%
720
28%
1453
December1st to 15thNight
47%
720
20%
2520
15%
720
55%
720
23%
1552
December16th to endNight
43%
768
21%
2688
17%
768
50%
768
21%
1737

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%212212235%63%
46060
Night
13%312212336%58%
45860
TransparencyDay
24%48%18%23%20%
45742
Night
28%49%19%22%16%
45678
SeeingDay
13%8%21%29%20%6%
5302
Night
14%316%34%27%3
14704

By Month

Percentage Cloud Cover SW (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%313312448%46%
1465
16th to endDay
22%423322235%48%
1728
February1st to 15thDay
22%31321436%5%45%
1576
16th to endDay
21%323332338%44%
1529
March1st to 15thDay
23%42432245%8%37%
1941
16th to endDay
20%5%13223248%45%
2136
April1st to 15thDay
18%42321345%8%45%
2149
16th to endDay
6%313313346%61%
2158
May1st to 15thDay
6%212212348%65%
2185
16th to endDay
8%213312246%62%
2391
June1st to 15thDay
6%212213346%66%
2310
16th to endDay
4111113379%
2310
July1st to 15thDay
11212483%
2310
16th to endDay
1112288%
2344
August1st to 15thDay
11111387%
2145
16th to endDay
1111288%
2133
September1st to 15thDay
1112485%
1980
16th to endDay
311111235%79%
1822
October1st to 15thDay
7%22212335%68%
1650
16th to endDay
13%312311235%61%
1760
November1st to 15thDay
12%212224447%55%
1622
16th to endDay
17%323323346%49%
1440
December1st to 15thDay
26%412213345%44%
1440
16th to endDay
28%322312226%42%
1536
January1st to 15thNight
18%41331335%7%47%
2470
16th to endNight
23%31321333448%
2496
February1st to 15thNight
23%413323346%43%
2276
16th to endNight
21%5%13323347%43%
1945
March1st to 15thNight
22%6%24323348%38%
2018
16th to endNight
20%413323447%45%
2088
April1st to 15thNight
15%325%424447%46%
1799
16th to endNight
9%313212246%62%
1780
May1st to 15thNight
8%11223245%67%
1435
16th to endNight
6%413424347%57%
1368
June1st to 15thNight
5%322223446%63%
1320
16th to endNight
31112213378%
1320
July1st to 15thNight
11233480%
1320
16th to endNight
1111112286%
1514
August1st to 15thNight
11112384%
1485
16th to endNight
112387%
1715
September1st to 15thNight
1111489%
1650
16th to endNight
4111222478%
1806
October1st to 15thNight
7%211213235%68%
1980
16th to endNight
11%212322336%61%
2112
November1st to 15thNight
12%31331235%7%54%
2235
16th to endNight
18%312323347%50%
2520
December1st to 15thNight
27%312212335%45%
2520
16th to endNight
28%412312345%41%
2688

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
36%6%12%19%17%6%
1465
16th to endDay
40%47%15%19%12%
1728
February1st to 15thDay
39%412%16%22%3
1576
16th to endDay
40%49%27%15%3
1529
March1st to 15thDay
45%6%10%17%14%5%
1941
16th to endDay
39%5%12%20%16%5%
2136
April1st to 15thDay
38%6%11%20%18%4
2149
16th to endDay
23%5%10%24%26%9%
2158
May1st to 15thDay
17%49%22%28%17%
2185
16th to endDay
23%411%23%26%10%
2395
June1st to 15thDay
20%5%8%16%23%25%
2310
16th to endDay
11%15%14%33%34%
2310
July1st to 15thDay
6%2412%31%43%
2161
16th to endDay
5%2310%25%52%
2187
August1st to 15thDay
5%1314%30%44%
2129
16th to endDay
5%1213%31%44%
2133
September1st to 15thDay
5%149%27%50%
1980
16th to endDay
10%26%21%33%26%
1822
October1st to 15thDay
20%28%19%29%18%
1650
16th to endDay
26%49%21%23%14%
1760
November1st to 15thDay
30%6%11%28%14%9%
1622
16th to endDay
37%5%9%20%17%10%
1440
December1st to 15thDay
42%5%8%17%20%6%
1440
16th to endDay
46%39%18%15%6%
1536
January1st to 15thNight
36%5%13%19%16%8%
2470
16th to endNight
40%46%15%19%12%
2496
February1st to 15thNight
42%49%19%18%6%
2288
16th to endNight
40%410%22%17%3
1945
March1st to 15thNight
44%6%11%17%14%6%
2018
16th to endNight
38%5%13%20%15%5%
2088
April1st to 15thNight
38%5%14%21%14%6%
1799
16th to endNight
23%412%27%24%7%
1780
May1st to 15thNight
20%48%23%28%13%
1436
16th to endNight
26%6%12%25%20%9%
1368
June1st to 15thNight
22%5%10%20%24%17%
1320
16th to endNight
12%15%16%36%27%
1320
July1st to 15thNight
8%2412%32%40%
1240
16th to endNight
7%1411%24%51%
1408
August1st to 15thNight
7%1416%31%38%
1476
16th to endNight
5%1315%34%39%
1715
September1st to 15thNight
41311%30%49%
1650
16th to endNight
10%35%19%29%30%
1806
October1st to 15thNight
19%47%19%31%19%
1980
16th to endNight
25%37%25%21%16%
2112
November1st to 15thNight
29%6%14%28%12%8%
2235
16th to endNight
35%410%21%18%8%
2520
December1st to 15thNight
42%49%15%23%4
2520
16th to endNight
46%47%15%20%5%
2688

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
34%424%24%9%2
93
16th to endDay
25%8%21%17%17%8%
256
February1st to 15thDay
27%5%19%23%20%2
236
16th to endDay
24%10%20%26%15%3
229
March1st to 15thDay
32%10%20%20%11%6%
270
16th to endDay
21%13%26%22%14%1
288
April1st to 15thDay
20%18%21%22%12%2
269
16th to endDay
10%16%31%26%11%4
267
May1st to 15thDay
7%14%34%28%10%4
228
16th to endDay
7%10%25%25%20%9%
266
June1st to 15thDay
8%15%24%27%20%5%
255
16th to endDay
45%28%30%22%7%
255
July1st to 15thDay
1117%43%28%7%
245
16th to endDay
212%46%29%8%
271
August1st to 15thDay
2318%43%26%5%
255
16th to endDay
1419%39%23%12%
268
September1st to 15thDay
2318%34%28%12%
255
16th to endDay
37%16%32%27%12%
255
October1st to 15thDay
11%7%16%32%20%11%
255
16th to endDay
16%6%22%27%22%5%
272
November1st to 15thDay
16%6%16%23%30%6%
130
16th to endDay
18%11%25%30%13%1
60
December1st to 15thDay
40%8%23%21%6%
60
16th to endDay
18%23%35%17%4
64
January1st to 15thNight
19%315%35%20%4
720
16th to endNight
23%416%30%20%5%
768
February1st to 15thNight
23%315%34%21%1
704
16th to endNight
21%6%16%36%15%3
632
March1st to 15thNight
22%6%18%30%20%2
720
16th to endNight
20%6%20%34%17%1
768
April1st to 15thNight
14%8%24%31%18%1
719
16th to endNight
11%424%37%18%2
706
May1st to 15thNight
10%228%36%21%1
446
16th to endNight
8%420%37%27%1
343
June1st to 15thNight
6%322%45%20%
330
16th to endNight
3120%48%26%
330
July1st to 15thNight
7%39%50%2
310
16th to endNight
16%32%53%5%
462
August1st to 15thNight
1433%54%6%
493
16th to endNight
6%38%50%4
665
September1st to 15thNight
110%33%47%6%
660
16th to endNight
5%210%31%41%8%
656
October1st to 15thNight
8%319%31%30%7%
660
16th to endNight
12%213%34%29%6%
704
November1st to 15thNight
12%212%40%26%4
700
16th to endNight
18%313%35%24%4
720
December1st to 15thNight
27%317%30%16%4
720
16th to endNight
29%319%31%14%1
768
Page generated at 2017-04-30 17:40:04. Version ac04

Copyright 2017 A. Danko


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