Stellafane
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Stellafane clear sky chart from 2005-11-05 to 2018-02-22.

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
31%
15447
16%
48890
8%
15415
40%
15415
18%
32845

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
21%
780
16%
2716
7%
776
34%
776
13%
1848
January16th to endNight
20%
832
15%
2912
5%
832
34%
832
14%
1957
February1st to 15thNight
14%
764
13%
2420
3%
761
26%
761
12%
1744
February16th to endNight
19%
659
17%
1976
6%
659
33%
659
15%
1381
March1st to 15thNight
19%
720
16%
2160
6%
720
31%
720
15%
1495
March16th to endNight
25%
768
20%
2010
6%
768
35%
768
20%
1351
April1st to 15thNight
25%
718
16%
1796
4%
718
31%
718
20%
1277
April16th to endNight
26%
617
17%
1697
5%
617
35%
617
20%
1175
May1st to 15thNight
25%
502
16%
1582
9%
502
32%
502
16%
1110
May16th to endNight
39%
375
12%
1497
11%
374
46%
374
15%
999
June1st to 15thNight
35%
360
11%
1440
9%
360
45%
360
14%
956
June16th to endNight
45%
360
10%
1440
13%
360
52%
360
19%
906
July1st to 15thNight
56%
340
12%
1360
17%
340
60%
340
23%
812
July16th to endNight
55%
376
15%
1418
17%
354
61%
354
25%
826
August1st to 15thNight
53%
443
15%
1514
12%
441
57%
441
25%
913
August16th to endNight
55%
756
20%
1902
11%
756
57%
756
34%
1230
September1st to 15thNight
48%
720
19%
1827
9%
720
53%
720
33%
1184
September16th to endNight
49%
717
25%
1980
17%
717
55%
717
34%
1189
October1st to 15thNight
39%
720
18%
2057
11%
720
47%
720
22%
1396
October16th to endNight
27%
768
14%
2475
7%
768
38%
768
16%
1732
November1st to 15thNight
30%
760
17%
2472
10%
760
41%
760
18%
1640
November16th to endNight
29%
780
18%
2597
10%
780
40%
780
17%
1699
December1st to 15thNight
20%
780
13%
2730
4%
780
32%
780
12%
1935
December16th to endNight
16%
832
13%
2912
4%
832
27%
832
11%
2090

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
15%6%36%6%35%45%7%35%
49370
Night
15%6%25%5%345%5%6%38%
49060
Cloud CoverDay
15%6%36%5%35%45%7%35%
49380
Night
15%6%25%5%2445%7%38%
49065
TransparencyDay
47%6%12%19%11%1
49058
Night
44%7%13%21%12%1
48890
SeeingDay
21%15%27%20%10%4
6210
Night
20%14%28%26%9%
15447

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
13%8%36%7%345%7%8%30%
1552
16th to endDay
11%7%36%6%35%46%8%35%
1664
February1st to 15thDay
12%9%5%8%6%47%5%5%6%28%
1769
16th to endDay
12%11%48%6%345%46%32%
1644
March1st to 15thDay
17%9%47%5%345%5%6%30%
1790
16th to endDay
14%7%47%6%2335%6%38%
2211
April1st to 15thDay
17%7%36%5%43446%36%
2152
16th to endDay
17%6%35%5%245%46%37%
2262
May1st to 15thDay
22%7%35%6%2445%5%31%
2379
16th to endDay
18%6%35%5%3445%7%36%
2618
June1st to 15thDay
23%6%345%3445%6%30%
2520
16th to endDay
16%6%36%6%46%6%5%7%32%
2520
July1st to 15thDay
12%5%35%7%46%5%6%9%34%
2520
16th to endDay
12%425%6%36%5%6%8%37%
2654
August1st to 15thDay
12%426%6%45%6%6%8%35%
2424
16th to endDay
10%435%5%35%46%8%42%
2297
September1st to 15thDay
14%425%5%3436%8%41%
2133
16th to endDay
12%424424336%51%
1980
October1st to 15thDay
19%6%35%5%2434439%
1902
16th to endDay
18%7%37%5%3445%7%33%
1749
November1st to 15thDay
14%7%26%42445%7%39%
1716
16th to endDay
17%6%36%42445%6%38%
1690
December1st to 15thDay
17%9%37%6%35%346%32%
1560
16th to endDay
19%12%46%6%35%44427%
1664
January1st to 15thNight
12%8%27%6%346%5%6%35%
2716
16th to endNight
12%7%37%5%35%5%6%7%34%
2912
February1st to 15thNight
11%9%37%8%36%6%6%7%29%
2419
16th to endNight
13%8%36%6%35%5%6%7%33%
1976
March1st to 15thNight
17%7%26%5%345%5%6%35%
2147
16th to endNight
13%6%34425%45%6%41%
2010
April1st to 15thNight
17%6%35%4246%5%6%37%
1796
16th to endNight
18%5%25%5%33346%40%
1697
May1st to 15thNight
20%6%36%6%25%345%35%
1582
16th to endNight
17%5%25%6%3345%8%36%
1495
June1st to 15thNight
22%5%25%41436%6%35%
1440
16th to endNight
14%424425%6%6%7%40%
1440
July1st to 15thNight
11%3235%36%6%5%9%42%
1440
16th to endNight
11%4235%245%6%10%43%
1514
August1st to 15thNight
9%5%24435%45%8%45%
1524
16th to endNight
11%5%2332445%8%47%
1902
September1st to 15thNight
13%41332345%6%49%
1827
16th to endNight
11%414323446%53%
1980
October1st to 15thNight
18%5%245%24345%42%
2057
16th to endNight
18%6%35%435%5%6%5%35%
2475
November1st to 15thNight
13%7%36%6%34446%39%
2472
16th to endNight
15%6%35%5%34445%40%
2597
December1st to 15thNight
18%7%36%5%35%45%6%31%
2730
16th to endNight
18%9%36%6%35%45%6%29%
2912

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
13%8%36%7%445%6%8%30%
1552
16th to endDay
12%7%46%5%3445%9%35%
1664
February1st to 15thDay
11%10%5%8%7%36%45%6%28%
1769
16th to endDay
13%9%5%7%6%34446%32%
1644
March1st to 15thDay
17%9%5%7%5%35%45%6%30%
1800
16th to endDay
13%8%46%5%34346%38%
2211
April1st to 15thDay
17%7%36%6%34446%36%
2152
16th to endDay
17%6%26%5%2445%6%37%
2262
May1st to 15thDay
23%8%36%5%33446%31%
2379
16th to endDay
18%6%25%5%25%447%36%
2618
June1st to 15thDay
23%6%35%5%4445%6%30%
2520
16th to endDay
16%5%26%6%46%5%6%6%32%
2520
July1st to 15thDay
12%425%6%37%6%5%9%34%
2520
16th to endDay
12%5%25%6%36%6%6%7%37%
2654
August1st to 15thDay
12%5%26%6%36%6%6%8%35%
2424
16th to endDay
10%435%5%2446%9%43%
2297
September1st to 15thDay
13%5%25%5%25%45%8%41%
2133
16th to endDay
13%414433236%51%
1980
October1st to 15thDay
19%6%26%5%24335%39%
1902
16th to endDay
18%7%36%5%45%447%33%
1749
November1st to 15thDay
15%7%25%5%24447%40%
1716
16th to endDay
16%6%36%424446%38%
1690
December1st to 15thDay
17%8%48%6%34345%32%
1560
16th to endDay
20%12%36%6%36%44427%
1664
January1st to 15thNight
12%8%36%6%35%5%6%6%34%
2716
16th to endNight
13%7%36%5%35%5%5%7%34%
2912
February1st to 15thNight
11%9%37%7%36%6%6%7%30%
2412
16th to endNight
13%8%36%5%36%5%6%8%33%
1976
March1st to 15thNight
17%7%36%5%3445%6%36%
2160
16th to endNight
13%7%24435%45%6%41%
2009
April1st to 15thNight
17%6%35%4245%6%7%37%
1796
16th to endNight
19%5%245%23346%40%
1697
May1st to 15thNight
20%6%36%5%35%345%35%
1582
16th to endNight
17%6%25%6%3445%8%36%
1495
June1st to 15thNight
23%5%25%42445%7%35%
1440
16th to endNight
13%425%425%6%6%8%40%
1440
July1st to 15thNight
11%314436%6%6%8%42%
1440
16th to endNight
12%4144246%6%10%43%
1514
August1st to 15thNight
9%5%245%25%45%8%45%
1524
16th to endNight
11%5%233245%5%7%48%
1902
September1st to 15thNight
13%41331445%7%49%
1827
16th to endNight
12%413223446%53%
1980
October1st to 15thNight
18%6%245%24345%41%
2057
16th to endNight
19%6%25%4246%5%5%35%
2475
November1st to 15thNight
14%7%36%6%34436%40%
2472
16th to endNight
15%7%345%25%45%5%40%
2597
December1st to 15thNight
18%8%36%6%35%46%6%32%
2730
16th to endNight
19%9%36%5%345%5%6%29%
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
48%7%12%20%9%1
1553
16th to endDay
44%7%16%21%9%1
1664
February1st to 15thDay
56%6%11%16%7%
1772
16th to endDay
52%6%10%16%12%1
1644
March1st to 15thDay
53%6%11%14%10%2
1800
16th to endDay
47%5%10%18%14%4
2211
April1st to 15thDay
49%6%10%19%12%2
2152
16th to endDay
46%6%9%19%14%3
2262
May1st to 15thDay
54%5%7%18%12%1
2379
16th to endDay
47%7%12%18%11%1
2622
June1st to 15thDay
52%6%13%16%9%
2520
16th to endDay
49%9%13%15%11%
2520
July1st to 15thDay
44%9%12%19%12%
2371
16th to endDay
42%7%16%22%10%
2487
August1st to 15thDay
43%9%15%21%8%1
2410
16th to endDay
37%7%16%25%13%
2297
September1st to 15thDay
40%7%12%22%15%1
2133
16th to endDay
35%411%27%19%2
1980
October1st to 15thDay
48%5%8%23%10%2
1902
16th to endDay
50%5%13%20%8%1
1749
November1st to 15thDay
43%8%13%20%12%1
1716
16th to endDay
45%5%15%19%13%1
1690
December1st to 15thDay
53%6%13%16%9%
1560
16th to endDay
59%5%11%13%9%
1664
January1st to 15thNight
46%8%12%18%11%1
2716
16th to endNight
47%6%12%19%12%1
2912
February1st to 15thNight
50%7%14%16%9%
2420
16th to endNight
48%6%12%20%9%2
1976
March1st to 15thNight
48%5%12%20%10%2
2160
16th to endNight
41%5%13%17%17%4
2010
April1st to 15thNight
44%6%12%19%15%1
1796
16th to endNight
45%6%9%19%16%2
1697
May1st to 15thNight
51%48%17%15%2
1582
16th to endNight
46%8%13%19%10%1
1497
June1st to 15thNight
48%6%14%21%8%
1440
16th to endNight
40%10%15%22%11%
1440
July1st to 15thNight
35%10%15%26%11%
1360
16th to endNight
34%8%15%27%11%1
1418
August1st to 15thNight
35%8%15%25%13%1
1514
16th to endNight
33%7%13%30%14%
1902
September1st to 15thNight
34%7%12%27%17%
1827
16th to endNight
31%5%10%30%19%1
1980
October1st to 15thNight
44%6%12%22%12%2
2057
16th to endNight
48%8%12%22%8%
2475
November1st to 15thNight
45%5%13%19%13%1
2472
16th to endNight
44%6%15%21%10%1
2597
December1st to 15thNight
51%7%14%18%7%
2730
16th to endNight
53%6%13%16%9%
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
24%22%26%21%5%
90
16th to endDay
23%20%37%14%3
96
February1st to 15thDay
23%31%25%16%3
213
16th to endDay
22%21%30%20%3
265
March1st to 15thDay
29%17%31%18%3
270
16th to endDay
24%22%27%13%8%3
288
April1st to 15thDay
28%19%26%14%9%1
270
16th to endDay
24%14%28%18%9%4
270
May1st to 15thDay
31%17%23%15%7%3
288
16th to endDay
19%13%32%25%7%1
331
June1st to 15thDay
25%14%29%19%10%1
315
16th to endDay
16%14%33%20%12%2
315
July1st to 15thDay
16%7%32%24%15%3
305
16th to endDay
12%5%36%27%14%3
326
August1st to 15thDay
12%11%28%22%16%7%
313
16th to endDay
13%7%21%26%17%12%
332
September1st to 15thDay
16%9%22%22%19%9%
315
16th to endDay
14%8%25%19%15%16%
314
October1st to 15thDay
22%12%20%23%16%4
315
16th to endDay
25%14%25%23%9%
293
November1st to 15thDay
22%14%22%28%10%1
280
16th to endDay
26%20%25%17%9%1
220
December1st to 15thDay
22%30%24%15%7%
90
16th to endDay
37%22%30%9%
96
January1st to 15thNight
20%20%33%23%2
780
16th to endNight
21%17%36%22%2
832
February1st to 15thNight
19%19%38%20%1
764
16th to endNight
21%21%31%22%2
659
March1st to 15thNight
25%19%31%21%1
720
16th to endNight
21%19%29%21%7%
768
April1st to 15thNight
22%20%29%22%5%
718
16th to endNight
23%16%30%21%8%
617
May1st to 15thNight
23%13%30%26%6%
502
16th to endNight
18%8%27%30%13%1
375
June1st to 15thNight
24%9%24%30%11%
360
16th to endNight
13%430%41%10%
360
July1st to 15thNight
12%5%21%43%15%1
340
16th to endNight
12%224%37%21%1
376
August1st to 15thNight
11%324%42%16%1
443
16th to endNight
14%5%19%33%24%3
756
September1st to 15thNight
15%6%25%33%18%1
720
16th to endNight
15%7%22%28%21%5%
717
October1st to 15thNight
23%12%19%29%13%2
720
16th to endNight
23%16%27%24%7%
768
November1st to 15thNight
18%16%25%27%10%
760
16th to endNight
21%16%28%23%8%1
780
December1st to 15thNight
24%18%32%20%3
780
16th to endNight
26%18%34%18%1
832
Page generated at 2018-02-23 11:21:40. Version ac04

Copyright 2018 A. Danko


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