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 2017-04-01.

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%
14348
16%
45361
8%
14316
40%
14316
18%
30529

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%
720
16%
2506
7%
716
33%
716
12%
1722
January16th to endNight
19%
768
15%
2688
5%
768
33%
768
14%
1793
February1st to 15thNight
14%
704
12%
2231
3%
701
26%
701
12%
1603
February16th to endNight
19%
631
17%
1893
5%
631
34%
631
15%
1318
March1st to 15thNight
19%
720
16%
2160
6%
720
31%
720
15%
1495
March16th to endNight
25%
768
20%
2010
6%
768
36%
768
20%
1351
April1st to 15thNight
23%
662
17%
1656
4%
662
31%
662
20%
1176
April16th to endNight
26%
566
17%
1556
4%
566
35%
566
21%
1069
May1st to 15thNight
27%
460
17%
1450
10%
460
35%
460
17%
1003
May16th to endNight
41%
343
12%
1369
11%
342
48%
342
15%
901
June1st to 15thNight
34%
330
11%
1320
9%
330
44%
330
13%
898
June16th to endNight
46%
330
10%
1320
12%
330
51%
330
19%
829
July1st to 15thNight
55%
310
13%
1240
18%
310
59%
310
23%
745
July16th to endNight
54%
348
14%
1306
15%
326
60%
326
25%
756
August1st to 15thNight
52%
406
16%
1387
12%
404
57%
404
25%
840
August16th to endNight
54%
693
18%
1743
10%
693
57%
693
33%
1137
September1st to 15thNight
50%
660
20%
1675
10%
660
54%
660
33%
1087
September16th to endNight
49%
657
24%
1815
16%
657
55%
657
35%
1081
October1st to 15thNight
37%
660
19%
1885
11%
660
45%
660
21%
1298
October16th to endNight
27%
704
13%
2269
6%
704
37%
704
15%
1596
November1st to 15thNight
31%
700
18%
2277
10%
700
42%
700
19%
1497
November16th to endNight
29%
720
17%
2397
10%
720
39%
720
16%
1600
December1st to 15thNight
20%
720
13%
2520
4%
720
31%
720
12%
1782
December16th to endNight
16%
768
13%
2688
4%
768
27%
768
11%
1952

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%5%35%45%7%35%
45752
Night
15%6%35%5%345%5%6%38%
45531
Cloud CoverDay
15%7%36%5%35%45%7%35%
45762
Night
15%6%25%5%25%45%7%38%
45536
TransparencyDay
47%6%12%19%11%1
45440
Night
44%7%13%21%11%1
45361
SeeingDay
20%14%26%21%11%4
5093
Night
20%14%28%26%9%
14348

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%8%345%7%8%29%
1432
16th to endDay
11%7%36%6%35%46%9%35%
1536
February1st to 15thDay
12%9%5%8%6%47%5%5%7%28%
1629
16th to endDay
13%10%48%6%345%46%32%
1580
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
16%7%36%5%43446%37%
1978
16th to endDay
16%6%35%5%245%46%38%
2073
May1st to 15thDay
22%7%35%5%2445%6%33%
2180
16th to endDay
17%6%35%5%3445%7%37%
2394
June1st to 15thDay
23%6%346%4445%6%28%
2310
16th to endDay
16%6%36%6%46%6%5%7%32%
2310
July1st to 15thDay
12%5%35%7%46%5%6%9%34%
2310
16th to endDay
12%435%6%26%5%6%8%36%
2458
August1st to 15thDay
12%426%6%46%6%6%9%34%
2222
16th to endDay
10%435%6%35%46%8%41%
2105
September1st to 15thDay
14%425%5%3435%8%41%
1955
16th to endDay
13%424424336%51%
1815
October1st to 15thDay
20%7%35%5%24345%37%
1744
16th to endDay
18%7%37%5%3445%7%32%
1603
November1st to 15thDay
14%6%26%42445%7%40%
1581
16th to endDay
17%7%36%32445%6%38%
1560
December1st to 15thDay
17%9%37%6%34346%32%
1440
16th to endDay
19%13%46%6%35%44426%
1536
January1st to 15thNight
12%8%27%6%35%6%5%6%34%
2506
16th to endNight
13%7%47%5%35%5%6%7%35%
2688
February1st to 15thNight
11%9%37%8%36%6%6%7%29%
2230
16th to endNight
13%8%36%6%35%6%6%7%33%
1893
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%5%35%4247%5%6%37%
1656
16th to endNight
18%5%25%5%33345%41%
1556
May1st to 15thNight
19%5%26%6%25%345%37%
1450
16th to endNight
16%5%35%6%3335%8%37%
1367
June1st to 15thNight
23%5%25%5%15%46%6%32%
1320
16th to endNight
14%424425%6%6%7%40%
1320
July1st to 15thNight
10%3235%36%6%5%9%41%
1320
16th to endNight
11%4235%246%6%10%43%
1402
August1st to 15thNight
9%5%245%45%5%48%45%
1397
16th to endNight
11%5%23325%45%9%46%
1743
September1st to 15thNight
13%41332445%7%49%
1675
16th to endNight
12%414323336%53%
1815
October1st to 15thNight
19%6%25%5%24345%40%
1885
16th to endNight
18%6%35%5%35%5%6%5%34%
2269
November1st to 15thNight
13%7%36%6%34446%40%
2277
16th to endNight
16%7%35%5%35%445%39%
2397
December1st to 15thNight
19%7%36%5%35%45%6%32%
2520
16th to endNight
19%9%36%6%25%45%6%28%
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
13%8%36%7%445%6%8%30%
1432
16th to endDay
11%7%46%5%35%45%9%36%
1536
February1st to 15thDay
11%10%5%8%7%37%45%7%28%
1629
16th to endDay
13%9%5%7%6%34446%32%
1580
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
16%7%36%6%33346%36%
1978
16th to endDay
16%6%26%5%2445%6%38%
2073
May1st to 15thDay
22%7%26%433446%33%
2180
16th to endDay
17%6%25%5%25%447%37%
2394
June1st to 15thDay
23%6%35%5%4445%6%29%
2310
16th to endDay
16%5%26%6%46%5%6%6%32%
2310
July1st to 15thDay
12%435%6%37%6%6%9%34%
2310
16th to endDay
12%5%35%6%36%6%6%7%37%
2458
August1st to 15thDay
12%5%26%7%36%6%6%8%35%
2222
16th to endDay
11%435%6%2446%9%41%
2105
September1st to 15thDay
13%5%25%5%25%45%8%41%
1955
16th to endDay
13%414433236%50%
1815
October1st to 15thDay
20%6%26%5%24345%37%
1744
16th to endDay
18%7%36%5%45%447%32%
1603
November1st to 15thDay
15%7%26%424447%40%
1581
16th to endDay
17%6%46%42445%6%38%
1560
December1st to 15thDay
18%9%47%5%44345%32%
1440
16th to endDay
20%13%46%6%26%45%426%
1536
January1st to 15thNight
12%8%36%6%35%5%6%6%34%
2506
16th to endNight
13%7%46%5%25%5%5%7%35%
2688
February1st to 15thNight
11%9%37%7%36%6%6%7%30%
2223
16th to endNight
13%8%36%5%36%5%6%8%33%
1893
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%5%35%4245%7%7%37%
1656
16th to endNight
18%5%245%23346%41%
1556
May1st to 15thNight
18%6%36%5%35%346%37%
1450
16th to endNight
16%6%25%5%34448%37%
1367
June1st to 15thNight
23%5%25%5%2446%6%33%
1320
16th to endNight
13%425%425%6%6%8%40%
1320
July1st to 15thNight
11%314436%6%6%8%41%
1320
16th to endNight
11%4144246%5%10%43%
1402
August1st to 15thNight
9%5%236%35%45%8%45%
1397
16th to endNight
11%5%243245%48%47%
1743
September1st to 15thNight
14%41331445%7%48%
1675
16th to endNight
12%413223346%53%
1815
October1st to 15thNight
19%7%245%24345%40%
1885
16th to endNight
18%6%35%425%6%5%6%34%
2269
November1st to 15thNight
14%7%26%6%34436%40%
2277
16th to endNight
16%7%345%35%445%39%
2397
December1st to 15thNight
19%7%35%5%25%45%6%32%
2520
16th to endNight
20%10%36%5%2445%6%28%
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
49%7%12%20%9%1
1433
16th to endDay
44%7%16%21%9%1
1536
February1st to 15thDay
55%7%12%16%8%
1632
16th to endDay
52%5%10%16%12%2
1580
March1st to 15thDay
53%6%11%14%10%2
1800
16th to endDay
47%5%10%18%14%4
2211
April1st to 15thDay
48%6%10%18%13%2
1978
16th to endDay
45%5%9%20%14%3
2073
May1st to 15thDay
51%5%8%18%13%2
2180
16th to endDay
46%7%12%18%12%1
2398
June1st to 15thDay
54%6%13%17%7%
2310
16th to endDay
48%9%13%16%11%
2310
July1st to 15thDay
44%8%13%20%12%
2161
16th to endDay
42%7%16%22%10%
2291
August1st to 15thDay
43%9%14%21%8%1
2208
16th to endDay
38%7%16%24%11%1
2105
September1st to 15thDay
41%7%12%23%15%
1955
16th to endDay
35%411%27%19%1
1815
October1st to 15thDay
49%6%8%22%10%2
1744
16th to endDay
51%6%14%18%8%1
1603
November1st to 15thDay
43%8%14%20%12%1
1581
16th to endDay
46%5%14%18%12%1
1560
December1st to 15thDay
53%6%13%16%9%
1440
16th to endDay
60%6%12%12%8%
1536
January1st to 15thNight
47%8%12%18%10%1
2506
16th to endNight
46%6%12%19%12%1
2688
February1st to 15thNight
50%8%14%16%9%
2231
16th to endNight
47%6%12%21%9%2
1893
March1st to 15thNight
48%5%12%20%10%2
2160
16th to endNight
41%5%13%17%17%4
2010
April1st to 15thNight
43%7%12%19%15%1
1656
16th to endNight
44%5%9%19%16%3
1556
May1st to 15thNight
49%5%9%17%15%2
1450
16th to endNight
45%8%13%20%10%1
1369
June1st to 15thNight
50%7%13%20%7%
1320
16th to endNight
40%10%14%22%11%
1320
July1st to 15thNight
35%10%16%26%11%
1240
16th to endNight
34%8%16%27%10%1
1306
August1st to 15thNight
35%9%15%25%12%1
1387
16th to endNight
34%8%14%29%13%
1743
September1st to 15thNight
34%8%13%28%15%
1675
16th to endNight
31%5%11%30%20%1
1815
October1st to 15thNight
45%5%12%20%12%2
1885
16th to endNight
48%8%13%21%8%
2269
November1st to 15thNight
44%5%14%18%14%1
2277
16th to endNight
46%6%14%21%10%2
2397
December1st to 15thNight
51%7%14%19%6%
2520
16th to endNight
54%6%13%16%7%
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
25%23%25%21%5%
60
16th to endDay
26%21%31%15%4
64
February1st to 15thDay
22%28%26%17%4
163
16th to endDay
21%20%32%20%4
239
March1st to 15thDay
29%17%31%18%3
270
16th to endDay
24%22%27%13%8%3
288
April1st to 15thDay
27%19%23%16%10%2
212
16th to endDay
21%14%27%19%11%5%
210
May1st to 15thDay
28%15%25%16%9%4
228
16th to endDay
17%12%30%28%9%1
267
June1st to 15thDay
27%15%25%18%11%1
255
16th to endDay
15%9%32%23%14%3
255
July1st to 15thDay
14%6%29%27%17%4
245
16th to endDay
11%5%36%29%14%2
270
August1st to 15thDay
11%11%28%24%17%7%
253
16th to endDay
13%5%20%26%19%14%
268
September1st to 15thDay
16%6%20%22%22%11%
255
16th to endDay
15%9%25%19%13%16%
254
October1st to 15thDay
24%12%18%23%15%5%
255
16th to endDay
23%16%25%24%9%
243
November1st to 15thDay
21%13%22%29%11%1
235
16th to endDay
25%19%27%15%10%2
180
December1st to 15thDay
23%30%23%18%5%
60
16th to endDay
37%20%31%10%
64
January1st to 15thNight
20%20%32%23%2
720
16th to endNight
21%17%36%22%2
768
February1st to 15thNight
18%19%38%21%1
704
16th to endNight
21%22%32%22%2
631
March1st to 15thNight
25%19%31%21%1
720
16th to endNight
21%19%29%21%7%
768
April1st to 15thNight
22%21%30%21%5%
662
16th to endNight
22%16%30%21%8%
566
May1st to 15thNight
21%13%31%27%6%
460
16th to endNight
17%9%27%31%13%1
343
June1st to 15thNight
24%10%25%29%11%
330
16th to endNight
13%329%41%11%
330
July1st to 15thNight
12%5%21%41%16%1
310
16th to endNight
12%225%39%19%1
348
August1st to 15thNight
11%324%44%15%
406
16th to endNight
14%5%20%33%23%3
693
September1st to 15thNight
14%6%24%33%20%1
660
16th to endNight
15%7%22%28%20%4
657
October1st to 15thNight
25%13%18%28%12%1
660
16th to endNight
23%16%27%25%6%
704
November1st to 15thNight
18%15%26%28%10%1
700
16th to endNight
22%16%27%22%9%1
720
December1st to 15thNight
24%18%32%19%4
720
16th to endNight
27%19%33%18%1
768
Page generated at 2017-04-02 07:39:03. Version ac04

Copyright 2017 A. Danko


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