The SkyRunner Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the The SkyRunner Observatory clear sky chart from 2005-11-05 to 2017-12-02.

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
33%
15313
20%
47793
10%
15282
44%
15282
23%
30383

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
23%
720
20%
2506
9%
716
39%
716
19%
1561
January16th to endNight
21%
768
21%
2594
6%
768
39%
768
19%
1634
February1st to 15thNight
21%
704
18%
2234
5%
701
36%
701
19%
1462
February16th to endNight
22%
631
26%
1893
9%
631
44%
631
22%
1192
March1st to 15thNight
22%
720
19%
2148
7%
720
36%
720
21%
1411
March16th to endNight
23%
768
23%
1997
8%
768
35%
768
25%
1313
April1st to 15thNight
23%
718
18%
1796
5%
718
30%
718
26%
1234
April16th to endNight
27%
708
18%
1788
4%
708
36%
708
26%
1213
May1st to 15thNight
27%
490
19%
1570
9%
490
38%
490
18%
1044
May16th to endNight
39%
374
15%
1497
13%
374
47%
374
19%
923
June1st to 15thNight
39%
360
14%
1440
12%
360
51%
360
18%
911
June16th to endNight
52%
360
15%
1440
15%
360
61%
360
25%
821
July1st to 15thNight
50%
340
13%
1360
15%
340
56%
340
21%
824
July16th to endNight
56%
376
16%
1418
18%
354
63%
354
24%
829
August1st to 15thNight
54%
551
18%
1622
12%
549
58%
549
30%
1008
August16th to endNight
54%
764
19%
1910
10%
764
56%
764
31%
1287
September1st to 15thNight
47%
720
23%
1800
12%
720
52%
720
33%
1166
September16th to endNight
52%
717
27%
1967
20%
717
57%
717
34%
1218
October1st to 15thNight
39%
720
20%
2112
14%
720
47%
720
26%
1362
October16th to endNight
30%
768
24%
2396
13%
768
46%
768
26%
1479
November1st to 15thNight
34%
760
22%
2472
11%
760
49%
760
24%
1504
November16th to endNight
29%
780
22%
2599
11%
780
44%
780
22%
1592
December1st to 15thNight
26%
728
16%
2546
7%
728
38%
728
17%
1650
December16th to endNight
21%
768
19%
2688
6%
768
37%
768
17%
1745

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
16%5%25%43445%7%40%
48664
Night
16%5%24424446%43%
47963
Cloud CoverDay
16%5%25%43445%7%40%
48673
Night
16%5%24424446%43%
47969
TransparencyDay
42%5%11%22%15%2
48352
Night
41%5%12%22%16%2
47793
SeeingDay
20%11%28%23%12%3
6028
Night
19%10%30%27%10%
15314

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
15%6%245%36%446%41%
1432
16th to endDay
14%7%25%4245%5%6%41%
1629
February1st to 15thDay
16%6%25%5%25%447%39%
1627
16th to endDay
15%5%25%5%25%5%46%41%
1580
March1st to 15thDay
17%7%25%5%35%448%36%
1800
16th to endDay
17%6%25%423335%42%
2226
April1st to 15thDay
17%7%25%323346%41%
2152
16th to endDay
17%5%24333346%43%
2172
May1st to 15thDay
23%5%14435%5%47%33%
2391
16th to endDay
16%5%25%5%35%5%5%8%35%
2618
June1st to 15thDay
20%6%245%345%5%7%34%
2520
16th to endDay
12%5%25%5%45%6%5%8%37%
2520
July1st to 15thDay
12%5%25%6%36%5%5%8%36%
2520
16th to endDay
11%5%35%6%35%6%6%8%36%
2654
August1st to 15thDay
13%5%246%45%6%6%8%36%
2314
16th to endDay
13%425%5%35%5%5%8%40%
2292
September1st to 15thDay
14%425%5%34446%44%
2160
16th to endDay
14%425%5%24436%45%
1992
October1st to 15thDay
18%5%24423347%42%
1845
16th to endDay
19%423323446%44%
1827
November1st to 15thDay
19%5%14313346%45%
1716
16th to endDay
17%5%23223447%46%
1690
December1st to 15thDay
18%5%25%41445%6%41%
1451
16th to endDay
20%7%24333347%37%
1536
January1st to 15thNight
18%5%24423447%42%
2506
16th to endNight
15%7%25%424446%42%
2594
February1st to 15thNight
14%7%35%5%25%35%5%40%
2233
16th to endNight
16%5%25%333346%46%
1893
March1st to 15thNight
18%6%24323335%43%
2135
16th to endNight
16%7%24423345%45%
1997
April1st to 15thNight
18%6%2442435%8%40%
1796
16th to endNight
19%5%24424346%43%
1788
May1st to 15thNight
19%5%35%423445%39%
1570
16th to endNight
19%5%2432345%8%40%
1495
June1st to 15thNight
20%5%233235%5%7%39%
1440
16th to endNight
10%3334245%6%10%44%
1440
July1st to 15thNight
12%325%5%25%5%7%9%40%
1440
16th to endNight
10%424436%5%7%10%40%
1514
August1st to 15thNight
11%315%4345%49%46%
1632
16th to endNight
12%425%435%5%47%44%
1910
September1st to 15thNight
16%314433347%47%
1800
16th to endNight
13%5%14323445%50%
1967
October1st to 15thNight
19%5%24323246%45%
2112
16th to endNight
18%5%1431235%6%47%
2396
November1st to 15thNight
17%5%14324345%47%
2472
16th to endNight
17%424423446%44%
2599
December1st to 15thNight
20%6%245%2445%5%39%
2546
16th to endNight
19%6%24434346%40%
2688

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
15%6%245%25%446%41%
1432
16th to endDay
14%7%2442446%6%42%
1629
February1st to 15thDay
16%6%35%425%447%39%
1627
16th to endDay
15%5%246%245%5%6%41%
1580
March1st to 15thDay
17%7%25%5%3445%7%36%
1810
16th to endDay
17%6%25%424336%43%
2225
April1st to 15thDay
18%7%25%323346%41%
2152
16th to endDay
17%424423347%43%
2172
May1st to 15thDay
22%5%24425%448%34%
2391
16th to endDay
16%6%26%435%5%5%8%35%
2618
June1st to 15thDay
19%5%245%345%5%8%35%
2520
16th to endDay
12%425%5%45%5%6%8%37%
2520
July1st to 15thDay
11%5%36%5%36%5%6%8%36%
2520
16th to endDay
10%5%26%5%36%5%6%8%36%
2654
August1st to 15thDay
12%4246%5%6%6%6%7%37%
2314
16th to endDay
13%425%5%25%45%8%40%
2292
September1st to 15thDay
14%425%5%35%347%44%
2160
16th to endDay
14%5%26%5%33445%45%
1992
October1st to 15thDay
18%6%24433347%42%
1845
16th to endDay
20%413323346%45%
1827
November1st to 15thDay
18%5%24322346%44%
1716
16th to endDay
17%5%23323446%46%
1690
December1st to 15thDay
17%6%26%414346%41%
1451
16th to endDay
21%7%24324346%38%
1536
January1st to 15thNight
18%5%24423447%42%
2506
16th to endNight
15%8%25%433446%41%
2594
February1st to 15thNight
13%7%36%43435%5%40%
2226
16th to endNight
16%5%2432435%5%45%
1893
March1st to 15thNight
18%7%34324336%42%
2148
16th to endNight
16%7%24423345%45%
1997
April1st to 15thNight
18%6%2442435%8%39%
1796
16th to endNight
19%5%24423346%43%
1788
May1st to 15thNight
19%5%35%423446%38%
1570
16th to endNight
19%5%25%32345%8%40%
1495
June1st to 15thNight
20%5%234235%5%7%39%
1440
16th to endNight
9%4235%35%5%5%10%44%
1440
July1st to 15thNight
12%325%5%35%5%6%9%40%
1440
16th to endNight
9%4145%26%6%8%9%40%
1514
August1st to 15thNight
10%415%5%2445%7%46%
1632
16th to endNight
12%425%435%45%6%44%
1910
September1st to 15thNight
16%414423347%47%
1800
16th to endNight
13%5%1441335%5%50%
1967
October1st to 15thNight
18%6%25%323246%45%
2112
16th to endNight
18%5%23313246%46%
2396
November1st to 15thNight
17%5%24313335%47%
2472
16th to endNight
17%5%24423346%44%
2599
December1st to 15thNight
19%6%24434446%38%
2546
16th to endNight
19%6%24434346%39%
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
42%5%13%23%11%3
1433
16th to endDay
41%413%24%13%2
1629
February1st to 15thDay
44%6%12%22%13%2
1630
16th to endDay
41%412%25%14%1
1580
March1st to 15thDay
45%5%14%21%10%2
1810
16th to endDay
44%410%20%17%3
2226
April1st to 15thDay
43%310%22%15%4
2152
16th to endDay
40%49%20%20%3
2172
May1st to 15thDay
47%6%9%19%15%2
2391
16th to endDay
45%6%12%20%13%1
2622
June1st to 15thDay
45%7%12%20%12%
2520
16th to endDay
40%8%13%22%13%1
2520
July1st to 15thDay
42%7%11%21%15%1
2371
16th to endDay
41%7%13%23%12%2
2487
August1st to 15thDay
42%7%13%19%16%
2300
16th to endDay
39%6%9%24%18%1
2292
September1st to 15thDay
39%5%10%21%21%1
2160
16th to endDay
39%5%7%21%23%2
1992
October1st to 15thDay
41%5%11%22%17%2
1845
16th to endDay
40%49%25%17%2
1827
November1st to 15thDay
41%312%21%18%2
1716
16th to endDay
37%411%27%16%2
1690
December1st to 15thDay
43%6%15%19%13%1
1451
16th to endDay
46%5%14%21%11%
1536
January1st to 15thNight
41%5%12%23%13%3
2506
16th to endNight
43%311%23%15%2
2594
February1st to 15thNight
44%5%12%22%13%2
2234
16th to endNight
40%38%25%18%3
1893
March1st to 15thNight
43%413%21%13%3
2148
16th to endNight
40%411%21%18%4
1997
April1st to 15thNight
42%410%23%16%2
1796
16th to endNight
42%49%19%21%3
1788
May1st to 15thNight
45%5%9%19%17%2
1570
16th to endNight
41%7%16%17%14%2
1497
June1st to 15thNight
44%6%12%19%15%1
1440
16th to endNight
34%7%14%27%14%1
1440
July1st to 15thNight
38%9%13%21%15%2
1360
16th to endNight
35%8%16%22%14%3
1418
August1st to 15thNight
34%8%13%25%16%2
1622
16th to endNight
38%6%11%21%19%1
1910
September1st to 15thNight
37%5%10%26%18%1
1800
16th to endNight
35%47%23%27%1
1967
October1st to 15thNight
41%410%23%16%2
2112
16th to endNight
39%311%26%17%1
2396
November1st to 15thNight
39%411%22%18%4
2472
16th to endNight
40%312%26%14%2
2599
December1st to 15thNight
45%5%14%21%12%
2546
16th to endNight
45%413%22%12%1
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
20%23%36%16%3
60
16th to endDay
25%12%45%11%5%
79
February1st to 15thDay
22%23%33%19%
143
16th to endDay
17%20%35%20%4
239
March1st to 15thDay
22%21%29%21%5%
270
16th to endDay
22%15%33%18%7%1
288
April1st to 15thDay
24%12%33%17%10%1
270
16th to endDay
24%10%37%14%9%3
270
May1st to 15thDay
31%15%26%15%7%2
288
16th to endDay
22%7%27%29%11%2
331
June1st to 15thDay
23%10%27%24%13%1
315
16th to endDay
19%8%31%25%13%2
315
July1st to 15thDay
14%8%27%31%15%3
305
16th to endDay
12%424%30%24%2
326
August1st to 15thDay
15%420%33%16%9%
313
16th to endDay
15%220%28%23%9%
332
September1st to 15thDay
15%8%28%22%14%10%
315
16th to endDay
17%5%22%23%15%15%
314
October1st to 15thDay
24%5%22%24%18%4
315
16th to endDay
20%14%29%21%12%1
313
November1st to 15thDay
23%10%27%25%11%2
280
16th to endDay
19%18%31%22%5%2
220
December1st to 15thDay
19%23%34%12%6%3
63
16th to endDay
39%17%32%10%
64
January1st to 15thNight
20%13%38%22%5%
720
16th to endNight
20%17%35%23%2
768
February1st to 15thNight
18%15%38%25%1
704
16th to endNight
20%17%35%22%3
631
March1st to 15thNight
23%15%34%21%4
720
16th to endNight
20%14%35%21%6%
768
April1st to 15thNight
21%14%36%22%4
718
16th to endNight
21%13%32%24%7%
708
May1st to 15thNight
21%12%33%25%7%
490
16th to endNight
22%5%25%35%10%1
375
June1st to 15thNight
20%328%33%13%
360
16th to endNight
11%326%45%13%
360
July1st to 15thNight
14%223%42%16%
340
16th to endNight
12%122%40%20%2
376
August1st to 15thNight
14%122%37%22%1
551
16th to endNight
15%218%35%26%2
764
September1st to 15thNight
18%423%34%17%1
720
16th to endNight
16%420%32%20%5%
717
October1st to 15thNight
21%7%27%25%15%2
720
16th to endNight
22%10%32%24%9%
768
November1st to 15thNight
20%10%28%24%13%1
760
16th to endNight
20%15%30%24%8%1
780
December1st to 15thNight
24%12%30%25%5%1
728
16th to endNight
23%13%36%23%2
768
Page generated at 2017-12-03 11:16:41. Version ac04

Copyright 2017 A. Danko


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