Sugar Grove Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sugar Grove Observatory clear sky chart from 2005-11-05 to 2017-08-12.

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
38%
15798
19%
46489
12%
15754
45%
15754
25%
30512

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%
899
16%
2506
5%
895
30%
895
20%
1778
January16th to endNight
21%
960
14%
2580
4%
960
28%
960
18%
1905
February1st to 15thNight
24%
811
13%
2220
4%
809
31%
809
18%
1622
February16th to endNight
24%
631
19%
1893
8%
631
34%
631
21%
1267
March1st to 15thNight
25%
720
15%
2160
7%
720
32%
720
19%
1514
March16th to endNight
28%
576
15%
1995
8%
576
37%
576
18%
1350
April1st to 15thNight
28%
539
18%
1797
11%
539
40%
539
23%
1151
April16th to endNight
34%
540
18%
1796
14%
540
42%
540
21%
1189
May1st to 15thNight
36%
540
16%
1593
10%
540
43%
540
22%
1092
May16th to endNight
48%
563
20%
1497
12%
561
53%
561
32%
971
June1st to 15thNight
56%
540
19%
1440
12%
540
60%
540
38%
871
June16th to endNight
55%
540
19%
1440
12%
540
58%
540
34%
910
July1st to 15thNight
65%
510
19%
1360
14%
510
67%
510
37%
834
July16th to endNight
74%
564
26%
1417
20%
531
77%
531
46%
786
August1st to 15thNight
77%
527
23%
1617
25%
524
78%
524
42%
880
August16th to endNight
69%
525
20%
1750
21%
525
74%
525
33%
998
September1st to 15thNight
63%
495
30%
1650
31%
495
68%
495
33%
923
September16th to endNight
60%
638
29%
1796
21%
638
66%
638
38%
1042
October1st to 15thNight
51%
660
29%
1930
20%
660
59%
660
35%
1130
October16th to endNight
29%
704
22%
2192
12%
704
40%
704
26%
1360
November1st to 15thNight
34%
700
25%
2276
17%
700
46%
700
26%
1354
November16th to endNight
27%
756
19%
2376
12%
756
36%
756
22%
1557
December1st to 15thNight
22%
900
12%
2520
5%
900
29%
900
18%
1883
December16th to endNight
18%
960
12%
2688
3%
960
25%
960
13%
2145

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
13%7%36%5%3445%7%37%
47492
Night
13%7%35%5%24446%41%
46658
Cloud CoverDay
13%7%36%5%3445%7%37%
47500
Night
13%7%35%5%34446%41%
46663
TransparencyDay
45%5%12%21%12%2
47178
Night
43%411%22%14%2
46490
SeeingDay
14%6%25%26%18%7%
5779
Night
17%8%29%29%13%1
15800

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%13%6%8%7%35%345%24%
1432
16th to endDay
14%13%7%9%5%36%445%26%
1641
February1st to 15thDay
13%11%5%9%7%25%335%30%
1642
16th to endDay
12%12%5%8%7%3445%6%29%
1580
March1st to 15thDay
15%11%37%5%3445%5%32%
1799
16th to endDay
15%11%47%6%245%5%7%28%
2229
April1st to 15thDay
16%9%36%5%24346%36%
2151
16th to endDay
19%8%25%5%3445%6%34%
2163
May1st to 15thDay
18%9%36%4245%5%7%31%
2355
16th to endDay
13%5%36%6%46%5%5%7%36%
2617
June1st to 15thDay
9%426%5%345%5%8%43%
2520
16th to endDay
9%5%25%5%35%5%6%9%41%
2520
July1st to 15thDay
8%425%435%6%7%9%43%
2520
16th to endDay
5%424436%7%7%10%42%
2655
August1st to 15thDay
6%424426%5%6%9%46%
2246
16th to endDay
8%415%5%35%5%6%8%44%
2100
September1st to 15thDay
13%4345%3345%6%44%
1980
16th to endDay
9%42442346%6%47%
1823
October1st to 15thDay
13%6%2443335%5%45%
1698
16th to endDay
16%7%2442335%6%42%
1680
November1st to 15thDay
15%7%24323446%46%
1582
16th to endDay
18%9%47%42324438%
1583
December1st to 15thDay
19%11%5%7%6%3435%6%25%
1440
16th to endDay
21%14%45%6%24435%25%
1536
January1st to 15thNight
13%10%37%5%34445%35%
2506
16th to endNight
13%11%6%7%6%345%45%32%
2580
February1st to 15thNight
14%10%6%7%6%34445%33%
2218
16th to endNight
13%10%37%424346%38%
1893
March1st to 15thNight
17%9%46%5%24446%34%
2147
16th to endNight
16%7%46%5%3445%8%32%
1995
April1st to 15thNight
13%7%45%434446%40%
1797
16th to endNight
19%6%25%5%35%447%37%
1796
May1st to 15thNight
18%7%34434347%37%
1593
16th to endNight
9%436%6%235%6%8%43%
1496
June1st to 15thNight
8%5%135%25%45%8%49%
1440
16th to endNight
7%325%6%35%47%8%44%
1440
July1st to 15thNight
8%42443446%10%47%
1440
16th to endNight
23245%1435%10%55%
1513
August1st to 15thNight
431332446%10%54%
1626
16th to endNight
7%3144345%47%52%
1750
September1st to 15thNight
12%323423346%53%
1650
16th to endNight
7%3144245%5%8%51%
1796
October1st to 15thNight
11%414414346%52%
1930
16th to endNight
18%7%13423336%45%
2192
November1st to 15thNight
11%6%245%2344450%
2276
16th to endNight
16%8%34433446%39%
2376
December1st to 15thNight
20%12%47%424335%31%
2520
16th to endNight
21%14%5%9%6%23335%24%
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
16%13%6%9%7%35%25%5%24%
1432
16th to endDay
14%13%6%9%6%35%445%26%
1641
February1st to 15thDay
13%11%6%9%7%24346%29%
1642
16th to endDay
12%11%5%9%6%34446%29%
1580
March1st to 15thDay
15%11%47%5%25%45%5%32%
1809
16th to endDay
15%11%38%5%3446%7%28%
2227
April1st to 15thDay
17%8%36%5%24346%37%
2151
16th to endDay
19%8%26%6%2445%6%34%
2163
May1st to 15thDay
19%9%26%5%246%5%6%31%
2355
16th to endDay
13%5%26%6%45%5%5%7%36%
2617
June1st to 15thDay
9%5%25%6%245%6%8%43%
2520
16th to endDay
9%6%25%5%35%5%6%9%40%
2520
July1st to 15thDay
8%425%5%35%6%6%10%43%
2520
16th to endDay
5%4245%35%7%7%10%42%
2655
August1st to 15thDay
6%415%5%25%5%6%9%46%
2246
16th to endDay
8%415%435%5%6%8%45%
2100
September1st to 15thDay
14%425%5%34447%45%
1980
16th to endDay
9%4344235%5%7%47%
1823
October1st to 15thDay
14%6%345%23445%45%
1698
16th to endDay
16%7%25%42345%6%41%
1680
November1st to 15thDay
15%6%2432335%5%46%
1582
16th to endDay
17%9%46%5%23245%37%
1583
December1st to 15thDay
19%12%5%7%5%3435%5%25%
1440
16th to endDay
21%14%5%5%6%24436%25%
1536
January1st to 15thNight
13%11%37%6%34445%35%
2506
16th to endNight
13%12%6%7%5%35%445%32%
2580
February1st to 15thNight
14%10%6%8%5%245%45%33%
2211
16th to endNight
13%11%46%424347%37%
1893
March1st to 15thNight
17%10%36%5%24446%34%
2160
16th to endNight
16%8%46%5%3445%7%33%
1995
April1st to 15thNight
14%7%35%5%3435%7%40%
1797
16th to endNight
19%6%15%5%34446%38%
1796
May1st to 15thNight
18%6%35%5%3445%7%37%
1592
16th to endNight
9%436%5%2446%8%43%
1496
June1st to 15thNight
9%41433445%7%50%
1440
16th to endNight
7%325%6%35%47%8%44%
1440
July1st to 15thNight
7%41444446%9%48%
1440
16th to endNight
232442425%11%55%
1513
August1st to 15thNight
431333346%9%54%
1626
16th to endNight
7%31443445%7%52%
1750
September1st to 15thNight
12%324422347%53%
1650
16th to endNight
7%41443446%8%51%
1796
October1st to 15thNight
11%324423345%52%
1930
16th to endNight
18%6%23322335%45%
2192
November1st to 15thNight
12%6%25%424335%49%
2276
16th to endNight
16%7%34433446%39%
2376
December1st to 15thNight
20%12%47%424335%31%
2520
16th to endNight
21%14%5%9%6%2333424%
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
62%310%13%9%
1433
16th to endDay
60%313%16%5%
1641
February1st to 15thDay
57%312%18%6%1
1644
16th to endDay
54%6%11%20%7%
1580
March1st to 15thDay
52%5%14%20%6%
1809
16th to endDay
53%5%13%20%5%1
2229
April1st to 15thDay
48%410%23%11%
2151
16th to endDay
49%5%12%17%11%2
2163
May1st to 15thDay
50%7%12%20%8%
2355
16th to endDay
44%6%13%18%14%2
2621
June1st to 15thDay
36%7%12%25%16%2
2520
16th to endDay
38%6%13%21%16%3
2520
July1st to 15thDay
35%7%13%25%14%3
2371
16th to endDay
31%9%16%26%14%1
2488
August1st to 15thDay
32%7%14%27%16%1
2231
16th to endDay
34%6%11%24%16%5%
2100
September1st to 15thDay
38%5%8%22%19%5%
1980
16th to endDay
34%48%27%21%3
1823
October1st to 15thDay
41%39%25%17%3
1698
16th to endDay
42%313%23%14%2
1680
November1st to 15thDay
39%311%23%17%3
1582
16th to endDay
49%311%24%9%
1583
December1st to 15thDay
60%5%11%15%7%
1440
16th to endDay
60%5%11%14%7%1
1536
January1st to 15thNight
51%312%19%13%
2506
16th to endNight
54%414%18%8%
2580
February1st to 15thNight
53%412%18%10%1
2220
16th to endNight
47%313%25%10%
1893
March1st to 15thNight
51%411%21%10%1
2160
16th to endNight
49%5%13%21%9%1
1995
April1st to 15thNight
43%310%24%14%2
1797
16th to endNight
46%5%10%21%12%4
1796
May1st to 15thNight
46%5%12%20%14%
1593
16th to endNight
37%6%14%20%19%2
1498
June1st to 15thNight
32%412%27%18%4
1440
16th to endNight
34%6%13%22%19%4
1440
July1st to 15thNight
32%6%11%28%18%3
1360
16th to endNight
23%5%15%33%18%2
1417
August1st to 15thNight
24%6%14%30%20%2
1617
16th to endNight
30%7%10%25%20%6%
1750
September1st to 15thNight
32%46%25%24%6%
1650
16th to endNight
29%5%10%27%23%3
1796
October1st to 15thNight
32%39%27%21%4
1930
16th to endNight
41%29%25%18%2
2192
November1st to 15thNight
38%39%23%19%5%
2276
16th to endNight
45%312%23%13%
2376
December1st to 15thNight
56%311%18%9%
2520
16th to endNight
64%38%14%7%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
28%13%37%15%4
90
16th to endDay
16%18%34%26%4
96
February1st to 15thDay
15%15%45%16%6%
90
16th to endDay
13%16%32%32%6%
81
March1st to 15thDay
32%22%26%15%3
90
16th to endDay
24%12%30%23%7%1
213
April1st to 15thDay
18%12%36%21%9%1
270
16th to endDay
21%7%29%25%12%4
270
May1st to 15thDay
24%9%25%27%8%3
312
16th to endDay
18%6%32%23%13%5%
517
June1st to 15thDay
11%325%30%23%5%
495
16th to endDay
11%7%31%27%16%5%
495
July1st to 15thDay
12%222%28%21%12%
475
16th to endDay
5%119%30%30%12%
515
August1st to 15thDay
8%113%27%31%16%
393
16th to endDay
8%213%29%34%11%
268
September1st to 15thDay
14%410%30%30%9%
255
16th to endDay
10%5%14%31%27%11%
254
October1st to 15thDay
7%9%23%31%18%8%
138
16th to endDay
22%344%22%6%
96
November1st to 15thDay
6%7%26%23%25%10%
90
16th to endDay
37%11%31%14%5%
90
December1st to 15thDay
20%18%33%21%33
90
16th to endDay
29%13%44%10%2
96
January1st to 15thNight
17%15%38%22%5%
900
16th to endNight
19%14%36%24%3
960
February1st to 15thNight
19%11%36%26%4
812
16th to endNight
20%12%37%25%3
631
March1st to 15thNight
22%10%34%26%5%
720
16th to endNight
19%10%38%22%8%
576
April1st to 15thNight
15%15%35%25%7%
539
16th to endNight
23%5%32%27%10%
540
May1st to 15thNight
21%6%28%32%9%1
540
16th to endNight
11%330%34%18%1
563
June1st to 15thNight
11%224%46%15%
540
16th to endNight
8%226%40%21%
540
July1st to 15thNight
10%116%39%28%3
510
16th to endNight
4112%42%35%3
564
August1st to 15thNight
6%9%42%35%5%
527
16th to endNight
7%112%38%36%3
525
September1st to 15thNight
14%212%36%30%4
495
16th to endNight
9%320%34%27%4
638
October1st to 15thNight
13%5%24%35%18%2
660
16th to endNight
24%8%34%23%8%
704
November1st to 15thNight
14%10%35%27%10%1
700
16th to endNight
21%11%35%25%6%
756
December1st to 15thNight
27%10%35%20%6%
900
16th to endNight
27%12%32%23%3
960
Page generated at 2017-08-13 13:16:38. Version ac04

Copyright 2017 A. Danko


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