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 2018-02-14.

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%
16583
19%
48804
12%
16539
45%
16539
25%
31975

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
22%
974
16%
2716
5%
970
31%
970
20%
1926
January16th to endNight
21%
1040
14%
2795
4%
1040
28%
1040
18%
2065
February1st to 15thNight
23%
876
13%
2397
4%
874
30%
874
18%
1758
February16th to endNight
23%
631
19%
1893
8%
631
33%
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
36%
576
18%
1350
April1st to 15thNight
28%
539
18%
1797
10%
539
40%
539
23%
1151
April16th to endNight
34%
540
18%
1796
14%
540
42%
540
21%
1189
May1st to 15thNight
37%
540
16%
1593
10%
540
44%
540
22%
1092
May16th to endNight
48%
563
20%
1497
12%
561
54%
561
32%
971
June1st to 15thNight
55%
540
19%
1440
12%
540
60%
540
38%
871
June16th to endNight
55%
540
19%
1440
12%
540
59%
540
34%
910
July1st to 15thNight
64%
510
19%
1360
14%
510
66%
510
37%
834
July16th to endNight
73%
564
27%
1417
20%
531
76%
531
46%
786
August1st to 15thNight
77%
539
23%
1655
25%
536
78%
536
42%
896
August16th to endNight
70%
573
22%
1910
22%
573
74%
573
33%
1080
September1st to 15thNight
64%
540
28%
1800
30%
540
68%
540
34%
996
September16th to endNight
61%
696
31%
1959
23%
696
66%
696
39%
1127
October1st to 15thNight
49%
720
28%
2106
19%
720
56%
720
34%
1251
October16th to endNight
30%
768
23%
2391
14%
768
41%
768
26%
1477
November1st to 15thNight
33%
760
24%
2471
16%
760
45%
760
26%
1494
November16th to endNight
28%
819
21%
2574
12%
819
39%
819
23%
1654
December1st to 15thNight
23%
975
12%
2730
5%
975
30%
975
19%
2003
December16th to endNight
18%
1040
12%
2912
4%
1040
25%
1040
13%
2313

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%
49281
Night
13%7%35%5%24446%41%
48973
Cloud CoverDay
13%7%36%5%3445%7%37%
49289
Night
13%7%35%5%34446%41%
48978
TransparencyDay
45%5%12%22%12%2
48967
Night
43%411%23%15%2
48805
SeeingDay
15%7%26%26%18%6%
6392
Night
17%8%29%29%13%1
16585

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%45%5%23%
1552
16th to endDay
13%13%6%9%5%35%345%27%
1778
February1st to 15thDay
13%12%5%9%7%25%335%29%
1766
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%324436%5%6%9%46%
2294
16th to endDay
7%415%5%45%5%6%8%44%
2292
September1st to 15thDay
12%4345%3345%6%46%
2160
16th to endDay
9%4245%2445%6%48%
1989
October1st to 15thDay
15%6%25%43335%5%43%
1852
16th to endDay
16%7%2442335%6%42%
1833
November1st to 15thDay
16%7%24323446%44%
1717
16th to endDay
17%9%36%42324439%
1715
December1st to 15thDay
18%10%5%7%6%3435%6%27%
1560
16th to endDay
20%15%45%6%24436%25%
1664
January1st to 15thNight
14%11%37%5%34445%35%
2716
16th to endNight
12%11%6%7%6%345%35%32%
2795
February1st to 15thNight
14%10%6%7%5%24445%32%
2395
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%9%54%
1664
16th to endNight
7%3144345%47%52%
1910
September1st to 15thNight
11%323423346%54%
1800
16th to endNight
7%3244245%5%8%52%
1959
October1st to 15thNight
13%414414346%51%
2106
16th to endNight
17%6%14423336%45%
2391
November1st to 15thNight
12%6%245%23445%48%
2471
16th to endNight
16%7%34423446%40%
2574
December1st to 15thNight
19%11%37%424335%33%
2730
16th to endNight
20%14%5%9%6%23335%25%
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
15%13%6%9%7%35%36%5%23%
1552
16th to endDay
14%13%6%9%6%35%445%27%
1778
February1st to 15thDay
13%12%6%9%7%24345%29%
1766
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%
2294
16th to endDay
8%415%5%36%5%6%8%45%
2292
September1st to 15thDay
13%414433447%46%
2160
16th to endDay
9%4344335%5%6%48%
1989
October1st to 15thDay
16%6%245%23445%43%
1852
16th to endDay
16%7%25%42345%6%42%
1833
November1st to 15thDay
16%6%2442335%6%44%
1717
16th to endDay
17%8%46%42334439%
1715
December1st to 15thDay
18%11%5%7%5%3435%6%27%
1560
16th to endDay
20%14%46%6%24436%25%
1664
January1st to 15thNight
13%11%37%5%34445%35%
2716
16th to endNight
13%11%5%7%6%35%445%32%
2795
February1st to 15thNight
15%10%6%7%5%24435%32%
2388
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%
1664
16th to endNight
7%31443445%6%53%
1910
September1st to 15thNight
11%324422346%54%
1800
16th to endNight
7%31443445%7%52%
1959
October1st to 15thNight
13%424423346%51%
2106
16th to endNight
18%6%23423345%45%
2391
November1st to 15thNight
12%6%25%424435%47%
2471
16th to endNight
16%7%34423446%41%
2574
December1st to 15thNight
19%12%46%424335%33%
2730
16th to endNight
21%14%6%9%6%2333425%
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
62%310%13%9%
1553
16th to endDay
59%313%17%6%
1778
February1st to 15thDay
57%312%18%6%1
1768
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%13%27%16%1
2279
16th to endDay
33%7%11%24%16%5%
2292
September1st to 15thDay
36%5%8%22%20%6%
2160
16th to endDay
34%48%28%21%2
1989
October1st to 15thDay
43%38%24%16%3
1852
16th to endDay
42%313%23%14%1
1833
November1st to 15thDay
40%312%23%16%3
1717
16th to endDay
47%311%26%10%
1715
December1st to 15thDay
57%5%11%17%8%
1560
16th to endDay
60%5%11%15%7%1
1664
January1st to 15thNight
51%311%19%14%
2716
16th to endNight
54%413%19%8%
2795
February1st to 15thNight
53%411%18%10%1
2397
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%31%21%2
1655
16th to endNight
29%7%10%25%20%5%
1910
September1st to 15thNight
31%46%25%24%6%
1800
16th to endNight
29%5%10%27%24%3
1959
October1st to 15thNight
33%38%27%20%4
2106
16th to endNight
41%29%25%18%2
2391
November1st to 15thNight
39%39%23%18%4
2471
16th to endNight
44%312%24%14%
2574
December1st to 15thNight
54%312%18%10%1
2730
16th to endNight
63%38%15%7%1
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
23%15%37%17%6%
135
16th to endDay
15%18%38%22%3
144
February1st to 15thDay
19%16%40%18%4
130
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%28%32%15%
409
16th to endDay
7%215%29%33%11%
332
September1st to 15thDay
12%412%29%31%9%
315
16th to endDay
8%5%14%30%29%11%
314
October1st to 15thDay
17%7%22%31%14%6%
187
16th to endDay
24%440%23%42
144
November1st to 15thDay
14%8%29%20%19%8%
135
16th to endDay
28%11%34%18%6%
135
December1st to 15thDay
14%27%33%17%5%2
135
16th to endDay
27%14%45%10%2
144
January1st to 15thNight
18%14%38%22%5%
975
16th to endNight
18%14%37%25%3
1040
February1st to 15thNight
20%11%36%26%4
877
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%
539
16th to endNight
7%113%37%36%3
573
September1st to 15thNight
13%212%36%30%4
540
16th to endNight
9%319%34%28%4
696
October1st to 15thNight
14%5%24%34%17%2
720
16th to endNight
23%9%34%23%9%
768
November1st to 15thNight
15%10%35%27%10%
760
16th to endNight
20%11%36%25%6%
819
December1st to 15thNight
26%10%35%21%6%
975
16th to endNight
27%12%33%23%3
1040
Page generated at 2018-02-15 09:58:46. Version ac04

Copyright 2018 A. Danko


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