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 2017-04-02.

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%
14528
20%
45375
10%
14497
44%
14497
23%
28901

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
24%
720
20%
2506
9%
716
40%
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
21%
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%
666
19%
1666
5%
666
30%
666
25%
1159
April16th to endNight
29%
649
19%
1639
4%
649
37%
649
27%
1096
May1st to 15thNight
29%
449
20%
1439
10%
449
40%
449
20%
937
May16th to endNight
41%
342
15%
1369
13%
342
49%
342
20%
835
June1st to 15thNight
38%
330
15%
1320
12%
330
50%
330
17%
856
June16th to endNight
56%
330
14%
1320
15%
330
63%
330
25%
750
July1st to 15thNight
51%
310
14%
1240
15%
310
57%
310
21%
745
July16th to endNight
57%
348
16%
1306
17%
326
64%
326
25%
756
August1st to 15thNight
53%
504
19%
1485
13%
502
58%
502
30%
920
August16th to endNight
53%
700
18%
1750
9%
700
56%
700
30%
1187
September1st to 15thNight
48%
660
24%
1650
13%
660
53%
660
32%
1078
September16th to endNight
51%
657
26%
1803
19%
657
56%
657
34%
1121
October1st to 15thNight
38%
660
21%
1936
14%
660
46%
660
26%
1252
October16th to endNight
29%
704
22%
2196
11%
704
45%
704
25%
1373
November1st to 15thNight
33%
700
23%
2277
11%
700
49%
700
24%
1382
November16th to endNight
29%
720
20%
2399
11%
720
42%
720
21%
1499
December1st to 15thNight
27%
720
16%
2520
7%
720
39%
720
17%
1637
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%434447%40%
45753
Night
16%5%24424446%43%
45545
Cloud CoverDay
16%5%25%43445%7%40%
45762
Night
16%5%24424446%43%
45551
TransparencyDay
42%5%11%21%15%2
45441
Night
41%5%12%22%16%2
45375
SeeingDay
20%10%28%23%12%4
5104
Night
20%10%30%27%10%
14529

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
18%7%25%323345%41%
1984
16th to endDay
16%424433347%44%
1991
May1st to 15thDay
23%5%14434447%34%
2191
16th to endDay
15%5%26%5%35%5%48%36%
2394
June1st to 15thDay
20%6%245%35%45%7%33%
2310
16th to endDay
12%5%25%6%45%6%5%8%37%
2310
July1st to 15thDay
11%6%25%6%36%5%6%8%36%
2310
16th to endDay
10%435%6%35%6%6%9%37%
2458
August1st to 15thDay
12%5%245%45%6%6%8%37%
2122
16th to endDay
14%426%5%35%5%5%7%39%
2100
September1st to 15thDay
15%4245%34447%44%
1980
16th to endDay
15%325%424436%45%
1826
October1st to 15thDay
18%5%24423347%42%
1691
16th to endDay
19%423423446%43%
1675
November1st to 15thDay
19%5%14312345%46%
1581
16th to endDay
19%5%23223447%44%
1560
December1st to 15thDay
18%5%25%41445%6%40%
1440
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%3442435%7%39%
1666
16th to endNight
18%5%24424346%45%
1639
May1st to 15thNight
18%5%35%423446%40%
1439
16th to endNight
17%5%2432345%8%41%
1367
June1st to 15thNight
21%5%333235%6%7%37%
1320
16th to endNight
10%3334245%6%10%44%
1320
July1st to 15thNight
12%325%435%5%7%9%40%
1320
16th to endNight
9%424436%5%7%10%41%
1402
August1st to 15thNight
11%316%3345%48%46%
1495
16th to endNight
13%425%445%5%47%43%
1750
September1st to 15thNight
16%314433347%46%
1650
16th to endNight
14%5%15%323335%50%
1803
October1st to 15thNight
19%5%24323236%45%
1936
16th to endNight
18%5%1431235%6%45%
2196
November1st to 15thNight
17%6%24323345%47%
2277
16th to endNight
18%424423446%42%
2399
December1st to 15thNight
20%5%245%25%45%5%38%
2520
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%323336%41%
1984
16th to endDay
16%424424347%44%
1991
May1st to 15thDay
23%5%24434447%35%
2191
16th to endDay
15%6%26%4345%5%8%36%
2394
June1st to 15thDay
20%5%345%345%5%8%33%
2310
16th to endDay
11%425%5%45%5%6%9%37%
2310
July1st to 15thDay
11%5%36%5%36%5%6%8%36%
2310
16th to endDay
10%5%26%5%36%5%6%8%37%
2458
August1st to 15thDay
12%4246%46%6%6%7%37%
2122
16th to endDay
13%5%35%6%35%45%8%38%
2100
September1st to 15thDay
14%425%5%35%347%44%
1980
16th to endDay
15%425%5%34445%45%
1826
October1st to 15thDay
18%6%24434347%42%
1691
16th to endDay
19%5%13423446%44%
1675
November1st to 15thDay
19%5%24322346%45%
1581
16th to endDay
18%5%23323447%44%
1560
December1st to 15thDay
17%6%26%414346%40%
1440
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%7%38%
1666
16th to endNight
18%5%24423336%45%
1639
May1st to 15thNight
18%5%35%423446%40%
1439
16th to endNight
17%5%25%32345%8%41%
1367
June1st to 15thNight
21%5%234235%5%7%37%
1320
16th to endNight
9%4235%35%5%5%10%44%
1320
July1st to 15thNight
11%315%5%35%5%6%9%40%
1320
16th to endNight
9%4145%36%6%8%9%40%
1402
August1st to 15thNight
11%415%5%25%45%7%47%
1495
16th to endNight
13%425%436%45%6%43%
1750
September1st to 15thNight
16%414423347%46%
1650
16th to endNight
14%5%24413345%49%
1803
October1st to 15thNight
18%5%25%323246%44%
1936
16th to endNight
18%5%23313347%45%
2196
November1st to 15thNight
17%5%24313335%47%
2277
16th to endNight
18%5%25%423346%42%
2399
December1st to 15thNight
20%6%24434446%38%
2520
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
44%310%20%15%4
1984
16th to endDay
39%49%20%22%3
1991
May1st to 15thDay
47%5%9%19%15%2
2191
16th to endDay
44%6%13%19%14%1
2398
June1st to 15thDay
46%7%12%20%10%
2310
16th to endDay
40%8%13%23%13%1
2310
July1st to 15thDay
42%7%11%21%15%1
2161
16th to endDay
40%7%13%23%12%2
2291
August1st to 15thDay
41%7%13%19%16%
2108
16th to endDay
41%6%8%23%17%1
2100
September1st to 15thDay
39%5%10%21%21%1
1980
16th to endDay
39%5%7%20%23%2
1826
October1st to 15thDay
41%5%10%22%17%2
1691
16th to endDay
40%410%25%16%2
1675
November1st to 15thDay
40%311%20%19%2
1581
16th to endDay
39%412%26%14%2
1560
December1st to 15thDay
43%6%15%20%13%1
1440
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
44%410%21%16%2
1666
16th to endNight
41%38%19%23%3
1639
May1st to 15thNight
43%6%9%20%17%2
1439
16th to endNight
40%7%17%16%16%2
1369
June1st to 15thNight
45%6%13%18%14%1
1320
16th to endNight
34%7%13%28%14%
1320
July1st to 15thNight
37%9%13%21%15%2
1240
16th to endNight
34%8%16%22%14%3
1306
August1st to 15thNight
34%7%13%25%16%2
1485
16th to endNight
39%6%11%21%18%1
1750
September1st to 15thNight
37%5%10%26%18%
1650
16th to endNight
36%46%24%27%1
1803
October1st to 15thNight
42%411%23%16%2
1936
16th to endNight
39%412%25%16%
2196
November1st to 15thNight
39%310%21%19%4
2277
16th to endNight
42%312%25%13%2
2399
December1st to 15thNight
45%5%14%20%12%
2520
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
25%11%32%17%11%1
214
16th to endDay
18%11%36%18%10%4
210
May1st to 15thDay
34%13%23%17%8%2
228
16th to endDay
18%8%25%30%13%3
267
June1st to 15thDay
25%10%25%24%12%1
255
16th to endDay
17%430%27%16%2
255
July1st to 15thDay
14%8%22%32%17%4
245
16th to endDay
10%427%31%24%2
270
August1st to 15thDay
13%418%37%16%9%
253
16th to endDay
17%216%26%25%11%
268
September1st to 15thDay
16%5%27%23%15%12%
255
16th to endDay
18%323%24%14%15%
254
October1st to 15thDay
22%6%23%24%18%4
255
16th to endDay
19%14%32%21%10%1
257
November1st to 15thDay
22%10%25%26%11%2
235
16th to endDay
20%16%33%21%6%2
180
December1st to 15thDay
20%25%35%11%6%1
60
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
22%15%35%22%4
666
16th to endNight
20%14%32%24%8%
649
May1st to 15thNight
20%11%33%26%8%
449
16th to endNight
20%5%25%37%10%1
343
June1st to 15thNight
21%428%31%13%
330
16th to endNight
10%223%47%14%
330
July1st to 15thNight
13%324%40%17%
310
16th to endNight
11%222%41%19%2
348
August1st to 15thNight
14%122%38%21%
504
16th to endNight
15%217%34%26%2
700
September1st to 15thNight
18%422%34%18%1
660
16th to endNight
17%321%33%20%4
657
October1st to 15thNight
21%7%27%26%15%1
660
16th to endNight
23%10%32%25%8%
704
November1st to 15thNight
20%11%29%23%13%1
700
16th to endNight
21%15%29%23%9%1
720
December1st to 15thNight
24%12%30%25%5%1
720
16th to endNight
23%13%36%23%2
768
Page generated at 2017-04-03 01:35:10. Version ac04

Copyright 2017 A. Danko


The SkyRunner Observatory Clear Sky Chart | Charts Home