PSU-Greenbush Astrophysical Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the PSU-Greenbush Astrophysical Observatory clear sky chart from 2005-11-06 to 2024-11-05.

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
42%
25231
22%
95995
15%
24955
51%
24955
26%
54417

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 10thNight
29%
944
23%
4025
9%
926
42%
926
21%
2378
January11th to 20thNight
25%
949
22%
4016
9%
930
37%
930
21%
2373
January21st to endNight
28%
1036
17%
4486
9%
1023
39%
1023
19%
2841
February1st to 10thNight
24%
950
19%
2470
6%
950
32%
950
26%
1685
February11th to 20thNight
25%
910
20%
2385
7%
906
33%
906
29%
1546
February21st to endNight
24%
552
25%
1808
11%
552
38%
552
25%
1077
March1st to 10thNight
30%
566
29%
3379
14%
555
45%
555
17%
1715
March11th to 20thNight
28%
563
25%
3420
11%
550
40%
550
17%
1561
March21st to endNight
23%
621
12%
3712
7%
605
37%
605
12%
2129
April1st to 10thNight
30%
570
23%
2014
12%
570
46%
570
28%
1131
April11th to 20thNight
31%
563
24%
1875
16%
563
45%
563
25%
1115
April21st to endNight
30%
570
20%
1782
12%
570
43%
570
26%
1118
May1st to 10thNight
35%
568
21%
2832
14%
559
44%
559
16%
1691
May11th to 20thNight
45%
549
16%
2781
18%
541
52%
541
19%
1630
May21st to endNight
47%
607
14%
3059
13%
593
55%
593
21%
1525
June1st to 10thNight
67%
570
20%
1710
16%
570
71%
570
38%
953
June11th to 20thNight
62%
570
21%
1710
16%
570
66%
570
42%
921
June21st to endNight
62%
570
22%
1710
18%
570
66%
570
46%
893
July1st to 10thNight
70%
545
19%
2624
18%
535
72%
535
25%
1419
July11th to 20thNight
76%
536
20%
2441
24%
533
79%
533
35%
1118
July21st to endNight
69%
608
18%
2803
26%
569
72%
569
26%
1410
August1st to 10thNight
71%
552
32%
2494
28%
544
74%
544
35%
1027
August11th to 20thNight
73%
552
21%
2576
34%
543
76%
543
26%
1395
August21st to endNight
75%
609
24%
2914
33%
605
77%
605
35%
1239
September1st to 10thNight
66%
570
29%
1924
32%
570
69%
570
37%
1018
September11th to 20thNight
64%
570
27%
2090
28%
570
69%
570
32%
1127
September21st to endNight
65%
570
32%
2090
32%
570
70%
570
37%
1033
October1st to 10thNight
59%
731
29%
2179
22%
711
63%
711
41%
1176
October11th to 20thNight
37%
760
27%
2355
14%
740
48%
740
33%
1383
October21st to endNight
36%
836
22%
2930
14%
814
47%
814
24%
1876
November1st to 10thNight
39%
760
33%
2280
16%
760
54%
760
40%
1238
November11th to 20thNight
35%
914
28%
2434
12%
914
47%
914
36%
1459
November21st to endNight
32%
950
26%
2557
11%
950
43%
950
33%
1581
December1st to 10thNight
32%
950
23%
2660
9%
950
44%
950
31%
1643
December11th to 20thNight
29%
948
24%
3017
9%
948
39%
948
25%
1898
December21st to endNight
26%
1042
16%
4453
9%
1026
38%
1026
15%
3095

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
12%7%26%44435%7%46%
100850
Night
11%6%25%43435%7%50%
98270
TransparencyDay
36%6%12%25%18%3
104501
Night
33%5%12%26%20%4
102746
SeeingDay
13%9%27%29%18%5%
15568
Night
14%8%31%33%13%1
25380

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 10thDay
15%9%37%5%43246%41%
2847
11th to 20thDay
10%11%37%6%33347%43%
2850
21st to endDay
18%12%47%43334439%
3135
February1st to 10thDay
16%10%37%433345%42%
1710
11th to 20thDay
13%9%28%433346%45%
1697
21st to endDay
14%9%36%5%445%45%41%
1644
March1st to 10thDay
15%8%35%333245%50%
3436
11th to 20thDay
13%6%15%33335%7%50%
3480
21st to endDay
15%9%46%5%4435%7%36%
3814
April1st to 10thDay
12%7%26%44445%6%45%
2166
11th to 20thDay
15%7%26%45%445%6%42%
2254
21st to endDay
20%8%36%43335%6%38%
2394
May1st to 10thDay
20%7%37%5%44346%36%
4082
11th to 20thDay
14%7%36%44446%7%41%
4082
21st to endDay
14%6%26%5%5%5%46%9%39%
4477
June1st to 10thDay
7%426%4445%7%9%49%
2470
11th to 20thDay
7%5%245%45%46%8%49%
2470
21st to endDay
5%31334438%8%56%
2470
July1st to 10thDay
9%7%27%45%5%46%8%42%
4120
11th to 20thDay
5%425%445%46%10%52%
4120
21st to endDay
6%425%5%6%6%5%8%11%42%
4465
August1st to 10thDay
5%325%445%46%9%54%
4104
11th to 20thDay
7%6%27%5%5%5%5%6%8%45%
4041
21st to endDay
5%42434446%7%58%
4252
September1st to 10thDay
11%5%25%444346%54%
2252
11th to 20thDay
10%5%25%445%46%7%49%
2090
21st to endDay
10%42443435%6%55%
2090
October1st to 10thDay
11%426%33435%6%54%
1909
11th to 20thDay
12%5%23323246%59%
1900
21st to endDay
18%7%2433323451%
2090
November1st to 10thDay
11%6%25%222345%58%
1898
11th to 20thDay
14%6%24323335%54%
1744
21st to endDay
16%7%34332246%51%
1615
December1st to 10thDay
11%10%36%443345%47%
1520
11th to 20thDay
13%11%36%5%5%3335%43%
2027
21st to endDay
18%15%6%7%434446%29%
3135
January1st to 10thNight
12%9%38%443245%47%
4108
11th to 20thNight
10%7%37%6%5%5%446%46%
4120
21st to endNight
20%10%46%322245%42%
4532
February1st to 10thNight
13%11%35%444345%42%
2470
11th to 20thNight
14%7%26%333345%48%
2384
21st to endNight
15%7%35%43335%5%47%
1808
March1st to 10thNight
14%7%25%333345%50%
3419
11th to 20thNight
11%5%25%33435%6%54%
3480
21st to endNight
14%6%37%44435%5%44%
3817
April1st to 10thNight
11%7%25%434346%51%
2014
11th to 20thNight
14%6%25%43335%5%49%
1875
21st to endNight
15%7%27%43435%7%44%
1782
May1st to 10thNight
16%7%26%5%44348%41%
2823
11th to 20thNight
14%7%37%44336%8%42%
2823
21st to endNight
11%5%25%43435%8%50%
3090
June1st to 10thNight
6%415%34446%10%53%
1710
11th to 20thNight
442443447%11%54%
1710
21st to endNight
5%32444445%8%59%
1710
July1st to 10thNight
10%5%26%44446%8%50%
2850
11th to 20thNight
221443446%11%58%
2850
21st to endNight
6%435%445%5%8%12%46%
3098
August1st to 10thNight
321434436%10%62%
2836
11th to 20thNight
8%5%25%44446%8%52%
2798
21st to endNight
321432435%8%65%
3404
September1st to 10thNight
8%425%443336%58%
1924
11th to 20thNight
8%5%2444435%7%52%
2090
21st to endNight
7%425%443346%60%
2090
October1st to 10thNight
9%31423435%6%60%
2251
11th to 20thNight
12%5%25%232245%58%
2280
21st to endNight
14%6%25%333245%53%
2508
November1st to 10thNight
11%5%14223245%61%
2280
11th to 20thNight
10%7%25%333345%55%
2434
21st to endNight
16%7%24322345%53%
2557
December1st to 10thNight
13%7%36%33335%7%48%
2660
11th to 20thNight
12%8%36%434246%46%
3153
21st to endNight
17%13%5%8%433346%34%
4532

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 10thDay
45%410%25%15%1
2848
11th to 20thDay
42%415%26%10%3
2850
21st to endDay
49%310%19%18%1
3135
February1st to 10thDay
46%5%10%24%12%3
1710
11th to 20thDay
43%312%23%16%3
1706
21st to endDay
43%5%9%21%15%7%
1644
March1st to 10thDay
37%47%23%23%5%
3436
11th to 20thDay
33%6%11%28%19%3
3480
21st to endDay
46%8%15%22%8%1
3814
April1st to 10thDay
37%7%13%22%17%3
2166
11th to 20thDay
42%6%13%21%15%3
2254
21st to endDay
48%5%11%24%12%1
2394
May1st to 10thDay
49%7%11%18%13%2
4120
11th to 20thDay
40%8%13%27%12%
4086
21st to endDay
40%9%16%22%13%1
4489
June1st to 10thDay
30%9%18%25%16%2
2470
11th to 20thDay
31%7%13%31%15%2
2470
21st to endDay
22%7%16%32%19%4
2470
July1st to 10thDay
37%8%13%20%17%4
4056
11th to 20thDay
27%7%12%35%17%2
4051
21st to endDay
30%9%21%29%10%
4325
August1st to 10thDay
25%6%15%25%24%5%
4090
11th to 20thDay
36%7%16%24%17%1
4080
21st to endDay
25%7%13%39%13%4
4251
September1st to 10thDay
32%5%10%26%18%9%
2252
11th to 20thDay
33%6%11%25%23%2
2090
21st to endDay
29%6%10%25%25%5%
2090
October1st to 10thDay
19%47%18%37%16%
3169
11th to 20thDay
17%25%29%36%11%
3140
21st to endDay
31%37%27%27%5%
3428
November1st to 10thDay
29%49%30%22%5%
1898
11th to 20thDay
34%38%25%25%5%
1744
21st to endDay
36%310%26%23%1
1615
December1st to 10thDay
39%49%32%15%1
1520
11th to 20thDay
45%38%22%19%3
2025
21st to endDay
56%5%10%18%9%1
3135
January1st to 10thNight
40%411%28%15%2
4108
11th to 20thNight
39%5%13%26%15%1
4120
21st to endNight
46%313%20%15%3
4532
February1st to 10thNight
44%411%24%14%3
2470
11th to 20thNight
38%411%25%19%3
2385
21st to endNight
39%39%21%20%7%
1808
March1st to 10thNight
36%410%22%21%6%
3419
11th to 20thNight
31%5%10%25%27%2
3480
21st to endNight
42%6%14%26%11%1
3817
April1st to 10thNight
34%5%11%22%22%6%
2014
11th to 20thNight
37%5%10%23%20%5%
1875
21st to endNight
40%5%11%25%17%3
1782
May1st to 10thNight
41%8%14%19%15%4
2850
11th to 20thNight
40%7%14%25%14%1
2824
21st to endNight
31%8%15%27%18%1
3099
June1st to 10thNight
25%9%17%28%18%3
1710
11th to 20thNight
23%8%17%31%19%2
1710
21st to endNight
23%5%15%31%20%5%
1710
July1st to 10thNight
32%6%15%25%19%4
2805
11th to 20thNight
20%6%12%38%21%3
2796
21st to endNight
27%8%21%30%13%1
2999
August1st to 10thNight
18%5%15%34%20%7%
2826
11th to 20thNight
29%7%14%28%20%2
2825
21st to endNight
18%5%13%40%18%4
3404
September1st to 10thNight
29%411%26%21%9%
1924
11th to 20thNight
31%6%9%24%26%5%
2090
21st to endNight
27%49%26%30%5%
2090
October1st to 10thNight
15%36%16%44%16%
3758
11th to 20thNight
21%35%20%35%17%
3779
21st to endNight
30%37%28%26%6%
4120
November1st to 10thNight
27%410%28%25%7%
2280
11th to 20thNight
32%38%24%28%4
2434
21st to endNight
36%48%24%24%4
2557
December1st to 10thNight
36%5%13%27%19%1
2660
11th to 20thNight
40%49%24%21%2
3154
21st to endNight
52%5%9%21%11%2
4532

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 10thDay
19%14%35%25%7%
270
11th to 20thDay
21%19%38%20%2
270
21st to endDay
14%13%47%20%6%
297
February1st to 10thDay
22%19%33%22%4
270
11th to 20thDay
17%18%41%18%41
270
21st to endDay
21%21%40%14%4
225
March1st to 10thDay
20%17%38%21%4
270
11th to 20thDay
24%17%33%22%4
270
21st to endDay
25%18%36%16%41
297
April1st to 10thDay
17%16%40%21%6%1
346
11th to 20thDay
18%13%41%22%6%
452
21st to endDay
22%14%33%22%8%1
574
May1st to 10thDay
16%12%35%28%8%1
653
11th to 20thDay
16%9%30%26%14%4
675
21st to endDay
14%8%29%24%17%7%
734
June1st to 10thDay
6%318%35%29%9%
680
11th to 20thDay
7%322%39%23%6%
680
21st to endDay
5%5%27%40%20%4
680
July1st to 10thDay
10%314%31%31%12%
671
11th to 20thDay
4215%37%34%8%
668
21st to endDay
7%210%35%33%13%
739
August1st to 10thDay
8%114%39%32%6%
676
11th to 20thDay
8%216%34%31%8%
665
21st to endDay
8%110%31%40%10%
585
September1st to 10thDay
10%213%32%32%10%
462
11th to 20thDay
5%216%39%28%11%
300
21st to endDay
11%5%20%35%21%7%
300
October1st to 10thDay
12%7%27%24%19%11%
300
11th to 20thDay
10%12%41%26%10%2
300
21st to endDay
25%11%32%23%7%1
330
November1st to 10thDay
16%10%35%24%12%2
282
11th to 20thDay
16%16%33%23%10%2
270
21st to endDay
19%14%34%24%7%2
270
December1st to 10thDay
13%11%45%19%8%3
270
11th to 20thDay
18%14%35%24%7%1
270
21st to endDay
18%24%40%16%2
297
January1st to 10thNight
15%13%39%27%5%
950
11th to 20thNight
16%13%41%25%5%
950
21st to endNight
15%12%40%29%5%
1045
February1st to 10thNight
19%13%41%24%4
950
11th to 20thNight
18%15%38%26%3
910
21st to endNight
21%12%39%25%3
552
March1st to 10thNight
14%12%39%30%4
570
11th to 20thNight
20%12%36%26%6%
570
21st to endNight
21%13%40%21%5%
627
April1st to 10thNight
13%13%41%27%6%
570
11th to 20thNight
18%13%35%29%6%
563
21st to endNight
18%11%38%26%7%
570
May1st to 10thNight
15%6%37%33%8%1
570
11th to 20thNight
14%6%28%35%17%1
561
21st to endNight
14%428%33%20%1
617
June1st to 10thNight
6%316%45%28%2
570
11th to 20thNight
5%125%48%20%1
570
21st to endNight
6%225%49%18%1
570
July1st to 10thNight
9%112%41%34%3
555
11th to 20thNight
4111%47%36%3
552
21st to endNight
7%113%39%36%4
624
August1st to 10thNight
4214%45%33%1
567
11th to 20thNight
8%19%52%26%2
564
21st to endNight
5%112%37%42%3
627
September1st to 10thNight
10%215%44%27%2
570
11th to 20thNight
11%216%43%25%4
570
21st to endNight
7%320%44%24%2
570
October1st to 10thNight
9%326%37%23%2
731
11th to 20thNight
14%7%39%32%8%1
760
21st to endNight
16%11%33%29%10%1
836
November1st to 10thNight
13%7%38%31%10%1
760
11th to 20thNight
13%12%36%30%9%
914
21st to endNight
18%12%34%28%7%
950
December1st to 10thNight
16%10%39%29%6%
950
11th to 20thNight
19%10%38%29%4
950
21st to endNight
17%14%38%27%3
1045
Page generated at 2024-11-03 01:11:17. Version ac07

Copyright © 2024 Attilla Danko.


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