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 2017-12-04.

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
62%
15381
27%
47861
23%
15343
68%
15343
39%
25922

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%
709
25%
1789
12%
709
59%
709
47%
1007
May1st to 15thNight
55%
485
27%
1565
18%
485
63%
485
48%
746
May16th to endNight
62%
374
23%
1496
23%
374
69%
374
34%
722
June1st to 15thNight
65%
360
23%
1440
25%
360
75%
360
36%
680
June16th to endNight
74%
360
33%
1440
40%
360
82%
360
61%
508
July1st to 15thNight
90%
340
32%
1360
45%
340
92%
340
69%
438
July16th to endNight
90%
499
39%
1529
41%
467
92%
467
77%
556
August1st to 15thNight
91%
538
38%
1611
32%
535
93%
535
76%
633
August16th to endNight
91%
726
46%
1872
31%
726
93%
726
85%
797
September1st to 15thNight
86%
720
42%
1800
27%
720
89%
720
84%
794
September16th to endNight
78%
716
41%
1971
35%
716
83%
716
67%
893
October1st to 15thNight
64%
720
31%
2160
27%
720
74%
720
52%
1038
October16th to endNight
68%
768
35%
2304
34%
768
75%
768
45%
1195
November1st to 15thNight
64%
760
23%
2426
23%
760
68%
760
33%
1396
November16th to endNight
58%
780
20%
2730
21%
780
62%
780
28%
1589
December1st to 15thNight
47%
736
20%
2576
15%
736
55%
736
24%
1580
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
10%212212235%64%
48640
Night
13%312212336%59%
48044
TransparencyDay
23%48%18%24%21%
48322
Night
28%49%19%22%16%
47862
SeeingDay
12%8%21%29%21%7%
6117
Night
13%315%34%27%4
15392

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%62%
2169
May1st to 15thDay
5%211212348%66%
2385
16th to endDay
7%213311246%63%
2615
June1st to 15thDay
6%212213346%65%
2520
16th to endDay
4111113380%
2520
July1st to 15thDay
1112484%
2520
16th to endDay
1112288%
2531
August1st to 15thDay
11112485%
2340
16th to endDay
1111288%
2328
September1st to 15thDay
11112485%
2160
16th to endDay
311111235%78%
1987
October1st to 15thDay
6%2122335%70%
1800
16th to endDay
12%212211235%63%
1920
November1st to 15thDay
14%313224347%52%
1760
16th to endDay
17%423323347%47%
1560
December1st to 15thDay
26%412213335%44%
1465
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%
1789
May1st to 15thNight
8%11223246%67%
1565
16th to endNight
6%413324347%59%
1496
June1st to 15thNight
5%323223447%61%
1440
16th to endNight
2112213380%
1440
July1st to 15thNight
11223481%
1440
16th to endNight
1111112287%
1635
August1st to 15thNight
111112384%
1620
16th to endNight
112387%
1872
September1st to 15thNight
1112486%
1800
16th to endNight
3111223477%
1971
October1st to 15thNight
6%211212235%70%
2160
16th to endNight
10%211212236%63%
2304
November1st to 15thNight
13%41331335%7%52%
2426
16th to endNight
18%313323347%49%
2730
December1st to 15thNight
26%312212335%45%
2576
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%
2169
May1st to 15thDay
17%49%23%29%16%
2385
16th to endDay
22%410%23%27%11%
2619
June1st to 15thDay
20%5%9%17%22%24%
2520
16th to endDay
11%15%13%32%35%
2520
July1st to 15thDay
6%2311%30%45%
2371
16th to endDay
5%139%24%54%
2374
August1st to 15thDay
5%1416%30%42%
2324
16th to endDay
5%1213%31%45%
2328
September1st to 15thDay
6%1411%26%48%
2160
16th to endDay
10%26%21%33%25%
1987
October1st to 15thDay
19%27%18%30%21%
1800
16th to endDay
25%48%20%23%16%
1920
November1st to 15thDay
32%6%10%28%13%8%
1760
16th to endDay
37%5%10%20%16%9%
1560
December1st to 15thDay
42%48%17%20%6%
1465
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%
1789
May1st to 15thNight
19%49%23%29%12%
1566
16th to endNight
25%6%11%25%21%9%
1496
June1st to 15thNight
23%5%10%20%22%16%
1440
16th to endNight
11%15%15%35%29%
1440
July1st to 15thNight
7%2411%31%42%
1360
16th to endNight
6%1310%23%53%
1529
August1st to 15thNight
7%1418%31%36%
1611
16th to endNight
41316%34%39%
1872
September1st to 15thNight
5%1412%28%47%
1800
16th to endNight
10%35%20%29%29%
1971
October1st to 15thNight
18%36%18%31%22%
2160
16th to endNight
24%37%24%20%19%
2304
November1st to 15thNight
31%6%14%28%12%7%
2426
16th to endNight
36%411%21%17%8%
2730
December1st to 15thNight
41%49%15%23%4
2576
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%30%26%11%4
270
May1st to 15thDay
6%15%32%27%13%4
288
16th to endDay
6%9%24%26%22%10%
330
June1st to 15thDay
9%13%22%28%20%5%
315
16th to endDay
4425%32%25%8%
315
July1st to 15thDay
115%41%31%9%
305
16th to endDay
214%42%30%10%
327
August1st to 15thDay
2216%39%28%9%
315
16th to endDay
1317%37%25%15%
332
September1st to 15thDay
1317%33%29%13%
315
16th to endDay
37%21%31%24%11%
315
October1st to 15thDay
9%10%18%30%21%9%
315
16th to endDay
14%5%18%26%27%7%
336
November1st to 15thDay
21%6%18%22%25%5%
178
16th to endDay
17%8%21%35%15%1
90
December1st to 15thDay
39%7%21%24%7%
66
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
709
May1st to 15thNight
9%228%36%20%1
486
16th to endNight
8%319%37%29%2
375
June1st to 15thNight
6%321%45%21%1
360
16th to endNight
3119%48%26%1
360
July1st to 15thNight
6%37%51%2
340
16th to endNight
15%33%52%6%
499
August1st to 15thNight
2330%55%7%
538
16th to endNight
5%36%51%5%
726
September1st to 15thNight
19%33%48%6%
720
16th to endNight
5%211%33%39%8%
716
October1st to 15thNight
7%420%31%29%6%
720
16th to endNight
11%213%34%30%7%
768
November1st to 15thNight
14%212%39%26%4
760
16th to endNight
19%313%36%23%3
780
December1st to 15thNight
27%317%30%16%3
736
16th to endNight
29%319%31%14%1
768
Page generated at 2017-12-05 07:19:02. Version ac04

Copyright 2017 A. Danko


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