Suwannee Skies Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Suwannee Skies 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
56%
16040
22%
47853
16%
16001
63%
16001
30%
29402

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
38%
717
20%
2327
11%
716
50%
716
24%
1433
January16th to endNight
38%
768
23%
2405
15%
768
48%
768
25%
1520
February1st to 15thNight
41%
701
26%
2107
15%
699
53%
699
31%
1265
February16th to endNight
41%
631
24%
1893
14%
631
51%
631
29%
1167
March1st to 15thNight
43%
720
28%
1989
15%
720
54%
720
37%
1172
March16th to endNight
49%
768
25%
2112
15%
768
56%
768
37%
1230
April1st to 15thNight
48%
718
23%
1976
14%
718
54%
718
36%
1190
April16th to endNight
57%
618
30%
1786
20%
618
65%
618
43%
956
May1st to 15thNight
68%
539
27%
1619
21%
539
72%
539
42%
870
May16th to endNight
75%
561
24%
1682
19%
561
77%
561
40%
944
June1st to 15thNight
70%
540
16%
1620
14%
540
72%
540
29%
1036
June16th to endNight
79%
540
12%
1620
10%
540
80%
540
29%
1052
July1st to 15thNight
77%
510
10%
1530
10%
510
77%
510
27%
1025
July16th to endNight
77%
564
8%
1595
8%
531
78%
531
22%
1115
August1st to 15thNight
75%
539
7%
1672
7%
536
75%
536
24%
1124
August16th to endNight
69%
645
12%
1982
12%
645
69%
645
20%
1395
September1st to 15thNight
65%
720
10%
1980
10%
720
65%
720
20%
1438
September16th to endNight
60%
717
19%
1980
17%
717
62%
717
24%
1380
October1st to 15thNight
62%
720
27%
2000
24%
720
66%
720
35%
1222
October16th to endNight
56%
768
32%
2304
27%
768
65%
768
37%
1296
November1st to 15thNight
56%
760
31%
2281
24%
760
66%
760
40%
1242
November16th to endNight
48%
780
29%
2532
21%
780
60%
780
34%
1395
December1st to 15thNight
47%
728
26%
2365
23%
728
54%
728
29%
1412
December16th to endNight
46%
768
24%
2496
20%
768
55%
768
27%
1523

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
9%5%25%6%35%5%6%8%39%
48580
Night
8%4244345%6%8%46%
48058
TransparencyDay
39%8%13%17%14%6%
48281
Night
34%7%14%19%15%7%
47861
SeeingDay
10%315%23%25%20%
5899
Night
10%419%31%26%6%
16049

By Month

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
12%7%35%424447%43%
1611
16th to endDay
13%425%41435%7%46%
1817
February1st to 15thDay
16%5%24423245%48%
1750
16th to endDay
12%5%25%5%23335%50%
1580
March1st to 15thDay
8%41332345%9%51%
1969
16th to endDay
8%42443445%6%51%
2111
April1st to 15thDay
8%4244345%5%8%46%
1972
16th to endDay
6%314425%5%6%7%50%
2181
May1st to 15thDay
6%313435%5%6%9%49%
2331
16th to endDay
7%315%6%46%6%6%9%43%
2431
June1st to 15thDay
9%5%36%7%47%7%8%11%28%
2340
16th to endDay
7%426%7%5%9%8%8%10%27%
2340
July1st to 15thDay
8%5%27%7%5%8%8%10%12%23%
2340
16th to endDay
8%6%38%9%6%9%8%8%11%20%
2465
August1st to 15thDay
12%437%7%5%8%8%10%12%18%
2274
16th to endDay
11%6%38%10%5%8%8%7%9%21%
2207
September1st to 15thDay
11%6%39%8%6%7%7%6%8%22%
1980
16th to endDay
11%7%48%7%46%5%6%8%29%
1980
October1st to 15thDay
10%5%246%35%45%7%43%
1959
16th to endDay
8%325%434446%52%
1920
November1st to 15thDay
7%413425%347%54%
1907
16th to endDay
9%5%13434437%51%
1755
December1st to 15thDay
10%5%26%33445%7%45%
1632
16th to endDay
10%5%25%5%3447%7%42%
1728
January1st to 15thNight
12%6%35%434348%43%
2327
16th to endNight
15%5%25%5%24445%43%
2405
February1st to 15thNight
12%5%24423345%51%
2103
16th to endNight
12%5%24424445%48%
1893
March1st to 15thNight
7%424423448%52%
1989
16th to endNight
8%5%24323446%54%
2112
April1st to 15thNight
7%4244235%5%6%51%
1976
16th to endNight
5%323423348%58%
1786
May1st to 15thNight
5%21342335%10%56%
1619
16th to endNight
44234235%5%11%52%
1682
June1st to 15thNight
8%4245%35%5%9%11%38%
1620
16th to endNight
6%3235%36%6%7%13%39%
1620
July1st to 15thNight
5%3245%35%6%10%16%36%
1620
16th to endNight
3326%6%47%9%10%13%31%
1703
August1st to 15thNight
6%415%5%47%7%9%14%33%
1683
16th to endNight
6%427%7%46%7%8%10%34%
1982
September1st to 15thNight
9%427%7%46%7%8%12%29%
1980
16th to endNight
10%7%36%6%35%6%7%9%34%
1980
October1st to 15thNight
7%5%245%3445%7%50%
2000
16th to endNight
7%42442435%6%54%
2304
November1st to 15thNight
6%324324448%54%
2281
16th to endNight
9%42441445%6%53%
2532
December1st to 15thNight
11%6%34324348%46%
2365
16th to endNight
10%5%35%5%3345%8%44%
2496

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
40%5%8%17%18%10%
1612
16th to endDay
37%49%17%20%10%
1817
February1st to 15thDay
39%26%14%20%16%
1752
16th to endDay
36%49%13%23%12%
1580
March1st to 15thDay
28%5%11%21%23%9%
1969
16th to endDay
31%5%11%21%18%11%
2112
April1st to 15thDay
33%411%18%21%9%
1972
16th to endDay
29%6%11%21%20%10%
2181
May1st to 15thDay
29%6%12%22%20%8%
2331
16th to endDay
34%9%15%21%15%3
2435
June1st to 15thDay
43%12%18%18%6%
2340
16th to endDay
44%15%17%16%6%
2340
July1st to 15thDay
44%15%24%13%1
2201
16th to endDay
51%12%22%10%2
2310
August1st to 15thDay
48%17%21%10%1
2261
16th to endDay
54%12%19%10%3
2207
September1st to 15thDay
54%11%17%9%5%1
1980
16th to endDay
48%9%12%16%9%3
1980
October1st to 15thDay
37%5%11%17%16%11%
1959
16th to endDay
31%5%7%14%24%16%
1920
November1st to 15thDay
28%410%22%22%12%
1907
16th to endDay
32%48%18%24%12%
1755
December1st to 15thDay
37%410%21%19%6%
1632
16th to endDay
37%5%12%22%12%8%
1728
January1st to 15thNight
40%49%17%18%9%
2327
16th to endNight
41%47%13%22%10%
2405
February1st to 15thNight
35%47%16%22%15%
2112
16th to endNight
37%48%15%22%11%
1893
March1st to 15thNight
30%411%24%18%10%
1989
16th to endNight
29%5%12%21%19%11%
2112
April1st to 15thNight
31%6%11%18%22%9%
1976
16th to endNight
23%5%12%28%21%8%
1786
May1st to 15thNight
23%6%12%26%19%10%
1620
16th to endNight
25%8%18%25%19%2
1684
June1st to 15thNight
35%9%20%28%5%
1620
16th to endNight
33%12%25%21%6%
1620
July1st to 15thNight
32%16%30%17%3
1530
16th to endNight
35%18%29%13%3
1595
August1st to 15thNight
36%14%32%14%1
1672
16th to endNight
39%16%23%16%3
1982
September1st to 15thNight
42%15%23%13%5%
1980
16th to endNight
42%10%15%18%9%3
1980
October1st to 15thNight
32%6%12%16%20%11%
2000
16th to endNight
30%37%16%24%16%
2304
November1st to 15thNight
27%49%23%24%11%
2281
16th to endNight
30%49%19%20%15%
2532
December1st to 15thNight
36%410%26%14%7%
2365
16th to endNight
38%410%23%14%8%
2496

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
17%14%40%12%10%5%
90
16th to endDay
21%11%40%15%10%
96
February1st to 15thDay
11%20%33%21%14%
90
16th to endDay
9%13%40%27%8%
81
March1st to 15thDay
10%9%33%28%14%3
259
16th to endDay
10%9%26%27%24%2
288
April1st to 15thDay
10%10%24%28%24%2
270
16th to endDay
7%121%30%27%11%
270
May1st to 15thDay
8%318%28%22%18%
288
16th to endDay
6%29%21%32%28%
331
June1st to 15thDay
12%7%15%32%30%
315
16th to endDay
9%217%27%42%
315
July1st to 15thDay
4212%24%55%
305
16th to endDay
7%1313%32%41%
326
August1st to 15thDay
15%411%30%37%
313
16th to endDay
9%315%30%40%
332
September1st to 15thDay
13%26%19%28%28%
315
16th to endDay
14%16%21%34%21%
314
October1st to 15thDay
10%117%30%28%10%
315
16th to endDay
8%425%30%22%6%
336
November1st to 15thDay
9%316%39%25%6%
325
16th to endDay
8%234%31%19%3
135
December1st to 15thDay
5%10%38%29%13%2
94
16th to endDay
13%7%28%32%14%4
96
January1st to 15thNight
15%12%26%30%13%1
720
16th to endNight
16%9%30%32%11%
768
February1st to 15thNight
14%8%32%31%12%1
704
16th to endNight
14%9%30%38%6%
631
March1st to 15thNight
10%8%32%35%12%
720
16th to endNight
10%6%28%34%18%
768
April1st to 15thNight
9%6%30%34%17%
718
16th to endNight
5%427%36%24%1
618
May1st to 15thNight
6%119%45%23%3
540
16th to endNight
6%110%35%39%7%
563
June1st to 15thNight
9%17%28%41%11%
540
16th to endNight
7%220%46%21%
540
July1st to 15thNight
6%315%43%30%
510
16th to endNight
4114%56%22%
564
August1st to 15thNight
8%212%53%22%
539
16th to endNight
8%419%43%21%
645
September1st to 15thNight
10%16%23%40%16%
720
16th to endNight
15%19%30%36%6%
717
October1st to 15thNight
10%216%38%28%3
720
16th to endNight
8%323%36%25%1
768
November1st to 15thNight
8%325%40%21%1
760
16th to endNight
10%6%29%35%16%1
780
December1st to 15thNight
13%7%25%33%19%
728
16th to endNight
12%8%26%34%17%
768
Page generated at 2017-12-03 11:16:40. Version ac04

Copyright 2017 A. Danko


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