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 2005-11-05 to 2018-10-08.

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
44%
17210
24%
51324
15%
17163
52%
17163
33%
30251

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
28%
975
24%
2522
8%
970
40%
970
34%
1579
January16th to endNight
32%
1040
30%
2704
11%
1040
44%
1040
37%
1603
February1st to 15thNight
26%
955
20%
2483
7%
951
34%
951
29%
1620
February16th to endNight
27%
682
24%
2048
9%
682
38%
682
27%
1273
March1st to 15thNight
33%
585
23%
2145
13%
585
46%
585
25%
1259
March16th to endNight
26%
624
17%
2288
10%
624
37%
624
20%
1452
April1st to 15thNight
33%
584
22%
2025
14%
584
46%
584
28%
1158
April16th to endNight
34%
579
21%
1847
15%
579
45%
579
26%
1151
May1st to 15thNight
41%
585
20%
1755
16%
585
48%
585
28%
1116
May16th to endNight
51%
611
19%
1829
16%
609
57%
609
31%
1136
June1st to 15thNight
64%
585
19%
1755
15%
585
68%
585
40%
963
June16th to endNight
63%
585
21%
1755
15%
585
68%
585
46%
910
July1st to 15thNight
71%
555
19%
1665
19%
555
72%
555
41%
913
July16th to endNight
76%
612
25%
1738
27%
579
78%
579
41%
947
August1st to 15thNight
76%
575
26%
1717
31%
572
77%
572
41%
927
August16th to endNight
73%
621
26%
1973
30%
621
75%
621
40%
1045
September1st to 15thNight
64%
585
26%
2031
28%
585
66%
585
32%
1141
September16th to endNight
64%
582
30%
2145
29%
582
70%
582
33%
1107
October1st to 15thNight
48%
732
27%
2236
19%
732
53%
732
34%
1290
October16th to endNight
42%
768
33%
2304
17%
768
54%
768
42%
1209
November1st to 15thNight
39%
800
30%
2320
14%
800
51%
800
37%
1317
November16th to endNight
32%
975
27%
2594
12%
975
43%
975
34%
1600
December1st to 15thNight
33%
975
21%
2730
9%
975
43%
975
31%
1694
December16th to endNight
28%
1040
24%
2715
9%
1040
39%
1040
26%
1841

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%6%2442445%7%45%
51796
Night
10%5%24423347%51%
51519
TransparencyDay
37%6%12%25%15%2
51496
Night
33%5%12%26%19%3
51324
SeeingDay
12%6%24%29%21%5%
7247
Night
13%7%30%32%14%1
17210

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
11%7%145%23235%51%
1746
16th to endDay
12%6%34422346%49%
1872
February1st to 15thDay
12%8%36%423435%43%
1710
16th to endDay
13%8%35%424435%42%
1719
March1st to 15thDay
13%8%35%434445%41%
2145
16th to endDay
21%8%36%423345%35%
2286
April1st to 15thDay
14%7%25%42445%6%42%
2253
16th to endDay
19%7%35%5%34345%37%
2385
May1st to 15thDay
17%6%36%6%3445%5%37%
2526
16th to endDay
13%5%35%5%35%5%6%8%37%
2638
June1st to 15thDay
7%425%4345%6%7%47%
2535
16th to endDay
5%212335%47%9%52%
2535
July1st to 15thDay
8%424336%6%6%10%44%
2535
16th to endDay
6%315%435%5%6%9%46%
2674
August1st to 15thDay
7%324435%5%5%10%46%
2486
16th to endDay
7%424435%5%5%8%47%
2578
September1st to 15thDay
13%5%24435%446%45%
2256
16th to endDay
10%414424446%51%
2145
October1st to 15thDay
13%6%24313346%50%
1880
16th to endDay
11%6%2332334455%
1920
November1st to 15thDay
11%5%23223336%54%
1866
16th to endDay
15%5%12312236%54%
1690
December1st to 15thDay
13%7%245%33336%46%
1560
16th to endDay
16%8%46%423336%41%
1856
January1st to 15thNight
11%5%23333345%52%
2522
16th to endNight
7%425%423346%55%
2704
February1st to 15thNight
11%9%3442433448%
2473
16th to endNight
15%5%25%41335%5%46%
2048
March1st to 15thNight
11%6%25%424347%47%
2145
16th to endNight
17%6%25%424445%41%
2288
April1st to 15thNight
11%6%24423346%50%
2025
16th to endNight
14%6%25%5%23346%45%
1847
May1st to 15thNight
12%5%15%5%35%347%44%
1754
16th to endNight
11%5%2433445%9%44%
1827
June1st to 15thNight
5%32342445%8%55%
1755
16th to endNight
32133335%6%9%57%
1755
July1st to 15thNight
6%22332446%10%52%
1755
16th to endNight
42243245%6%11%52%
1846
August1st to 15thNight
5%21432437%8%54%
1727
16th to endNight
5%31432446%8%56%
1973
September1st to 15thNight
10%434423446%52%
2031
16th to endNight
6%424434347%54%
2145
October1st to 15thNight
13%423313345%53%
2236
16th to endNight
8%314222246%61%
2304
November1st to 15thNight
9%5%14323335%57%
2320
16th to endNight
13%6%24312335%53%
2594
December1st to 15thNight
15%5%24313347%47%
2730
16th to endNight
14%8%36%5%23246%42%
2715

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
37%312%28%16%1
1747
16th to endDay
36%314%26%16%1
1872
February1st to 15thDay
42%5%14%25%10%1
1711
16th to endDay
44%410%23%14%3
1719
March1st to 15thDay
44%5%8%22%14%4
2145
16th to endDay
52%5%12%19%9%
2288
April1st to 15thDay
41%6%14%23%13%1
2253
16th to endDay
49%5%10%22%10%1
2385
May1st to 15thDay
47%6%11%22%11%
2526
16th to endDay
42%9%14%22%11%
2642
June1st to 15thDay
32%7%14%26%16%1
2535
16th to endDay
24%8%16%28%19%2
2535
July1st to 15thDay
32%8%17%27%12%2
2396
16th to endDay
29%8%16%31%13%1
2519
August1st to 15thDay
31%7%16%22%20%1
2472
16th to endDay
32%8%13%24%14%5%
2578
September1st to 15thDay
38%6%11%21%16%6%
2256
16th to endDay
32%5%10%29%17%4
2145
October1st to 15thDay
34%412%22%19%5%
1880
16th to endDay
31%39%29%19%5%
1920
November1st to 15thDay
31%39%28%20%5%
1866
16th to endDay
34%210%26%24%1
1690
December1st to 15thDay
40%311%30%14%
1560
16th to endDay
46%411%22%12%3
1856
January1st to 15thNight
34%311%27%18%2
2522
16th to endNight
30%312%30%18%3
2704
February1st to 15thNight
39%413%27%13%2
2483
16th to endNight
38%411%23%17%3
2048
March1st to 15thNight
38%410%21%19%5%
2145
16th to endNight
44%5%11%22%14%1
2288
April1st to 15thNight
34%411%25%20%3
2025
16th to endNight
40%410%24%17%2
1847
May1st to 15thNight
39%5%13%22%16%1
1755
16th to endNight
34%7%17%23%14%1
1829
June1st to 15thNight
25%6%16%30%18%2
1755
16th to endNight
21%6%16%32%20%3
1755
July1st to 15thNight
24%6%14%31%18%3
1665
16th to endNight
24%7%13%31%21%1
1738
August1st to 15thNight
24%6%13%31%19%4
1717
16th to endNight
24%7%13%28%20%6%
1973
September1st to 15thNight
32%5%11%22%19%7%
2031
16th to endNight
29%49%27%25%3
2145
October1st to 15thNight
32%410%21%23%7%
2236
16th to endNight
25%39%27%27%6%
2304
November1st to 15thNight
30%310%26%22%7%
2320
16th to endNight
34%47%26%24%3
2594
December1st to 15thNight
36%413%26%17%
2730
16th to endNight
43%411%22%13%4
2715

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%14%28%26%5%
135
16th to endDay
14%11%40%25%7%
144
February1st to 15thDay
10%23%41%18%5%
135
16th to endDay
20%22%34%18%5%
120
March1st to 15thDay
17%22%41%14%4
135
16th to endDay
24%15%35%18%6%
144
April1st to 15thDay
16%13%37%24%6%
252
16th to endDay
23%8%33%22%10%1
397
May1st to 15thDay
16%9%33%26%10%2
543
16th to endDay
15%5%29%25%16%7%
597
June1st to 15thDay
7%221%35%26%5%
570
16th to endDay
6%225%39%21%4
570
July1st to 15thDay
9%213%34%29%10%
550
16th to endDay
7%7%31%41%10%
595
August1st to 15thDay
9%11%33%38%7%
549
16th to endDay
10%113%35%33%6%
490
September1st to 15thDay
12%112%28%31%12%
291
16th to endDay
10%116%36%25%10%
180
October1st to 15thDay
12%5%34%29%8%8%
157
16th to endDay
13%7%38%31%6%2
144
November1st to 15thDay
20%7%25%24%17%3
135
16th to endDay
22%17%28%22%6%2
135
December1st to 15thDay
11%9%51%17%8%2
135
16th to endDay
19%18%40%18%3
144
January1st to 15thNight
15%13%40%25%5%
975
16th to endNight
11%11%40%30%6%
1040
February1st to 15thNight
16%11%40%27%3
955
16th to endNight
19%11%38%27%3
682
March1st to 15thNight
15%10%36%31%6%
585
16th to endNight
20%9%40%23%6%
624
April1st to 15thNight
15%10%37%29%6%
584
16th to endNight
18%7%35%29%9%
579
May1st to 15thNight
14%5%33%32%12%1
585
16th to endNight
15%225%32%22%1
611
June1st to 15thNight
6%219%44%25%1
585
16th to endNight
4125%47%19%
585
July1st to 15thNight
9%14%40%32%3
555
16th to endNight
5%9%38%42%3
612
August1st to 15thNight
6%18%44%36%2
575
16th to endNight
7%12%40%37%2
621
September1st to 15thNight
12%213%37%29%3
585
16th to endNight
7%219%38%28%4
582
October1st to 15thNight
15%328%30%19%2
732
16th to endNight
10%7%35%31%12%
768
November1st to 15thNight
12%9%35%29%12%1
800
16th to endNight
16%11%35%27%8%
975
December1st to 15thNight
17%9%36%28%6%
975
16th to endNight
19%10%37%28%4
1040
Page generated at 2018-10-09 09:39:19. Version ac04

Copyright 2018 A. Danko


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