Brockport State Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Brockport State Observatory clear sky chart from 2005-11-06 to 2024-01-31.

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
25%
22927
12%
75059
7%
22881
32%
22881
14%
55238

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
8%
758
7%
2649
2%
757
13%
757
4%
2217
January11th to 20thNight
9%
760
4%
2583
2%
760
12%
760
3%
2269
January21st to endNight
11%
835
8%
2711
3%
835
17%
835
5%
2328
February1st to 10thNight
6%
720
7%
2340
0%
720
15%
720
5%
1920
February11th to 20thNight
10%
703
9%
2275
2%
700
18%
700
6%
1848
February21st to endNight
11%
592
8%
1834
2%
592
17%
592
8%
1462
March1st to 10thNight
14%
720
11%
2020
4%
720
21%
720
12%
1596
March11th to 20thNight
17%
720
15%
1980
6%
720
25%
720
14%
1482
March21st to endNight
22%
792
16%
2156
6%
792
29%
792
17%
1611
April1st to 10thNight
17%
720
14%
1800
3%
720
23%
720
16%
1369
April11th to 20thNight
25%
711
15%
1775
5%
711
30%
711
20%
1292
April21st to endNight
28%
590
16%
1670
6%
590
35%
590
19%
1173
May1st to 10thNight
33%
486
15%
1566
8%
486
39%
486
18%
1064
May11th to 20thNight
35%
354
20%
1416
15%
354
48%
354
20%
849
May21st to endNight
42%
388
16%
1551
14%
388
53%
388
24%
882
June1st to 10thNight
35%
360
15%
1440
11%
360
50%
360
19%
903
June11th to 20thNight
39%
360
16%
1440
18%
360
50%
360
20%
844
June21st to endNight
37%
360
14%
1440
12%
360
49%
360
21%
877
July1st to 10thNight
50%
350
16%
1400
20%
350
57%
350
29%
747
July11th to 20thNight
46%
348
19%
1392
20%
348
54%
348
26%
766
July21st to endNight
50%
484
19%
1571
14%
457
57%
457
30%
901
August1st to 10thNight
53%
537
19%
1600
14%
534
57%
534
34%
950
August11th to 20thNight
54%
534
19%
1598
12%
534
57%
534
29%
996
August21st to endNight
49%
745
20%
1933
10%
745
53%
745
34%
1234
September1st to 10thNight
45%
720
19%
1800
8%
720
49%
720
31%
1189
September11th to 20thNight
50%
720
25%
1808
15%
720
54%
720
33%
1182
September21st to endNight
43%
720
19%
2074
15%
720
47%
720
24%
1388
October1st to 10thNight
33%
720
13%
2160
10%
720
38%
720
18%
1536
October11th to 20thNight
22%
720
11%
2160
6%
720
29%
720
15%
1600
October21st to endNight
18%
792
13%
2376
6%
792
26%
792
11%
1860
November1st to 10thNight
26%
740
18%
2434
11%
740
36%
740
16%
1663
November11th to 20thNight
19%
760
14%
2660
9%
760
27%
760
11%
1946
November21st to endNight
15%
760
9%
2660
4%
760
22%
760
8%
2071
December1st to 10thNight
9%
760
5%
2660
2%
760
13%
760
4%
2233
December11th to 20thNight
10%
760
5%
3256
1%
759
16%
759
4%
2730
December21st to endNight
7%
828
3%
4871
0%
817
11%
817
2%
4260

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
16%11%48%6%35%5%5%7%30%
74850
Night
16%11%5%8%7%45%5%5%6%29%
75281
TransparencyDay
53%6%11%18%10%1
74561
Night
55%7%11%17%9%1
75104
SeeingDay
22%19%30%19%8%3
13469
Night
22%17%29%21%9%1
22938

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 10thDay
14%18%9%12%9%47%5%5%413%
1517
11th to 20thDay
15%22%8%16%10%45%33311%
1596
21st to endDay
14%18%8%15%11%6%5%5%35%10%
1872
February1st to 10thDay
17%17%7%13%9%45%5%5%5%14%
1620
11th to 20thDay
14%15%10%16%9%3444417%
1573
21st to endDay
20%15%6%13%9%44445%15%
1422
March1st to 10thDay
15%13%7%13%8%45%445%21%
1935
11th to 20thDay
14%15%5%9%7%34436%29%
1980
21st to endDay
19%13%5%7%6%34446%30%
2200
April1st to 10thDay
16%13%6%7%5%3445%6%31%
2160
11th to 20thDay
19%10%36%5%335%46%37%
2134
21st to endDay
21%11%37%5%24446%32%
2304
May1st to 10thDay
16%9%37%6%45%5%5%7%34%
2393
11th to 20thDay
15%8%26%5%35%5%6%7%39%
2478
21st to endDay
12%5%36%6%35%47%8%42%
2725
June1st to 10thDay
16%6%36%6%35%5%6%8%38%
2520
11th to 20thDay
13%5%245%35%6%6%10%40%
2520
21st to endDay
13%6%25%5%35%5%6%9%42%
2520
July1st to 10thDay
9%425%5%345%7%9%47%
2520
11th to 20thDay
11%6%26%6%35%7%7%10%37%
2520
21st to endDay
11%435%7%46%6%7%10%37%
2651
August1st to 10thDay
9%6%35%6%36%6%6%9%41%
2327
11th to 20thDay
10%5%36%7%5%6%6%7%9%36%
2303
21st to endDay
14%6%25%6%345%6%9%41%
2404
September1st to 10thDay
15%7%35%445%5%5%8%41%
2160
11th to 20thDay
15%5%25%5%35%46%8%43%
2149
21st to endDay
15%7%36%6%45%5%5%8%36%
1886
October1st to 10thDay
22%7%36%6%445%6%5%33%
1800
11th to 20thDay
20%9%49%7%35%46%7%28%
1800
21st to endDay
26%13%47%7%44445%22%
1980
November1st to 10thDay
15%11%47%7%45%5%46%31%
1643
11th to 20thDay
14%16%6%10%8%43446%25%
1520
21st to endDay
19%17%5%9%7%35%35%7%18%
1520
December1st to 10thDay
20%20%8%12%7%34346%14%
1520
11th to 20thDay
19%19%8%14%7%3445%414%
1906
21st to endDay
25%22%8%12%6%3433310%
2772
January1st to 10thNight
16%18%7%12%10%5%5%44416%
2649
11th to 20thNight
16%19%8%14%11%5%5%34411%
2583
21st to endNight
13%17%8%13%12%5%5%5%45%14%
2711
February1st to 10thNight
16%18%6%11%8%45%445%17%
2340
11th to 20thNight
14%13%7%12%10%46%5%5%5%19%
2273
21st to endNight
18%13%6%13%8%4445%5%20%
1834
March1st to 10thNight
15%14%6%10%7%5%5%44425%
2010
11th to 20thNight
16%12%5%8%6%45%445%31%
1979
21st to endNight
17%10%5%8%7%345%45%32%
2156
April1st to 10thNight
19%12%48%6%35%45%5%30%
1800
11th to 20thNight
17%9%35%6%45%46%6%35%
1775
21st to endNight
19%9%36%5%35%5%6%7%33%
1670
May1st to 10thNight
18%8%35%6%35%6%5%7%35%
1566
11th to 20thNight
13%5%35%5%35%5%6%8%42%
1415
21st to endNight
10%5%35%5%345%5%8%48%
1550
June1st to 10thNight
14%5%36%5%25%5%8%10%36%
1440
11th to 20thNight
11%5%35%5%35%5%7%9%41%
1440
21st to endNight
10%5%36%5%46%5%7%8%41%
1440
July1st to 10thNight
6%5%25%6%35%45%9%50%
1440
11th to 20thNight
10%5%25%435%5%6%9%47%
1440
21st to endNight
10%5%244345%7%9%47%
1664
August1st to 10thNight
9%425%436%46%10%47%
1611
11th to 20thNight
9%426%7%35%47%9%43%
1598
21st to endNight
8%5%25%6%35%5%6%9%46%
1933
September1st to 10thNight
14%6%35%5%2445%8%45%
1800
11th to 20thNight
14%435%5%3346%7%46%
1808
21st to endNight
15%6%25%5%35%7%7%7%39%
2074
October1st to 10thNight
19%7%37%5%35%45%7%35%
2160
11th to 20thNight
20%9%47%5%445%5%7%29%
2160
21st to endNight
28%11%36%6%345%5%6%24%
2376
November1st to 10thNight
15%10%46%6%45%5%5%7%35%
2434
11th to 20thNight
14%11%48%8%45%6%6%7%27%
2660
21st to endNight
19%15%5%7%7%45%46%7%22%
2660
December1st to 10thNight
19%18%7%11%7%45%45%6%15%
2660
11th to 20thNight
18%18%7%12%8%44445%16%
3288
21st to endNight
30%17%7%11%7%343449%
4884

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
74%6%8%10%2
1518
11th to 20thDay
79%5%7%6%21
1596
21st to endDay
78%5%9%6%1
1872
February1st to 10thDay
72%5%10%10%2
1620
11th to 20thDay
72%5%8%12%3
1582
21st to endDay
72%5%7%10%5%
1422
March1st to 10thDay
66%410%14%5%1
1938
11th to 20thDay
58%5%9%16%11%1
1980
21st to endDay
58%48%18%11%2
2200
April1st to 10thDay
54%6%9%18%11%1
2160
11th to 20thDay
48%6%9%21%14%2
2134
21st to endDay
54%5%9%18%13%2
2304
May1st to 10thDay
49%6%11%21%12%2
2393
11th to 20thDay
44%6%11%23%13%2
2482
21st to endDay
39%8%14%24%14%1
2725
June1st to 10thDay
43%7%12%20%18%1
2520
11th to 20thDay
39%6%14%25%14%1
2520
21st to endDay
39%8%14%23%16%1
2520
July1st to 10thDay
33%7%13%28%17%2
2450
11th to 20thDay
38%9%16%25%12%
2445
21st to endDay
40%10%16%21%13%1
2503
August1st to 10thDay
37%9%16%25%12%1
2314
11th to 20thDay
43%9%14%23%10%1
2303
21st to endDay
39%8%14%27%11%2
2404
September1st to 10thDay
41%7%13%27%11%1
2160
11th to 20thDay
39%6%12%27%15%
2149
21st to endDay
46%7%13%22%11%1
1886
October1st to 10thDay
51%7%12%18%11%
1800
11th to 20thDay
56%6%14%17%6%1
1800
21st to endDay
65%5%10%12%6%1
1980
November1st to 10thDay
54%7%11%18%10%2
1643
11th to 20thDay
59%7%14%13%6%1
1520
21st to endDay
67%5%12%13%3
1520
December1st to 10thDay
73%5%10%10%2
1520
11th to 20thDay
74%7%9%7%3
1906
21st to endDay
80%5%7%6%1
2772
January1st to 10thNight
71%6%9%10%4
2649
11th to 20thNight
78%5%8%7%2
2583
21st to endNight
73%6%7%9%4
2711
February1st to 10thNight
69%6%9%12%5%
2340
11th to 20thNight
67%6%9%14%4
2275
21st to endNight
65%5%11%13%5%
1834
March1st to 10thNight
61%5%11%16%6%
2020
11th to 20thNight
55%6%10%19%9%1
1980
21st to endNight
55%6%8%18%12%2
2156
April1st to 10thNight
56%5%9%20%10%1
1800
11th to 20thNight
48%6%11%18%14%2
1775
21st to endNight
49%6%10%19%13%2
1670
May1st to 10thNight
48%6%10%19%15%1
1566
11th to 20thNight
39%8%12%23%15%2
1416
21st to endNight
34%7%15%22%19%2
1551
June1st to 10thNight
41%9%12%22%15%2
1440
11th to 20thNight
38%7%11%23%19%2
1440
21st to endNight
40%8%12%23%17%2
1440
July1st to 10thNight
31%7%14%26%19%3
1400
11th to 20thNight
34%6%13%30%16%1
1392
21st to endNight
32%7%15%28%16%2
1571
August1st to 10thNight
31%7%17%29%14%1
1600
11th to 20thNight
36%8%16%29%12%
1598
21st to endNight
33%8%14%30%13%2
1933
September1st to 10thNight
37%6%13%29%13%2
1800
11th to 20thNight
36%7%11%28%17%1
1808
21st to endNight
41%8%12%25%13%
2074
October1st to 10thNight
49%8%12%19%12%1
2160
11th to 20thNight
53%8%13%18%8%1
2160
21st to endNight
60%7%10%13%8%1
2376
November1st to 10thNight
48%7%11%21%11%2
2434
11th to 20thNight
55%7%13%16%8%1
2660
21st to endNight
62%7%14%14%3
2660
December1st to 10thNight
70%8%10%10%2
2660
11th to 20thNight
69%8%9%11%2
3288
21st to endNight
78%6%9%6%1
4884

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
28%32%26%10%31
180
11th to 20thDay
31%33%25%9%1
216
21st to endDay
23%32%30%11%3
294
February1st to 10thDay
31%39%25%5%
240
11th to 20thDay
30%40%26%5%
240
21st to endDay
40%25%27%7%1
288
March1st to 10thDay
24%29%30%14%3
420
11th to 20thDay
27%26%31%12%41
420
21st to endDay
32%24%24%15%41
462
April1st to 10thDay
27%23%34%12%5%
420
11th to 20thDay
31%22%26%13%7%2
412
21st to endDay
28%24%27%15%5%1
420
May1st to 10thDay
26%16%31%16%6%4
423
11th to 20thDay
18%15%34%23%7%2
447
21st to endDay
15%15%32%23%11%4
485
June1st to 10thDay
20%14%37%22%6%1
450
11th to 20thDay
17%14%31%26%9%2
450
21st to endDay
14%14%38%22%10%2
450
July1st to 10thDay
9%12%29%30%17%4
445
11th to 20thDay
14%10%30%29%12%4
444
21st to endDay
11%9%41%28%8%2
488
August1st to 10thDay
9%9%31%30%15%6%
446
11th to 20thDay
12%9%31%28%14%6%
439
21st to endDay
14%10%31%25%14%5%
495
September1st to 10thDay
15%12%27%26%12%7%
450
11th to 20thDay
14%11%22%25%19%8%
450
21st to endDay
18%16%28%22%11%6%
450
October1st to 10thDay
24%16%26%18%12%4
450
11th to 20thDay
24%25%28%16%5%2
450
21st to endDay
32%20%29%14%5%
495
November1st to 10thDay
22%22%30%17%8%2
332
11th to 20thDay
28%28%29%10%32
180
21st to endDay
27%28%35%8%2
180
December1st to 10thDay
32%26%27%12%31
180
11th to 20thDay
29%32%27%8%3
180
21st to endDay
34%32%24%9%1
198
January1st to 10thNight
26%31%28%12%3
760
11th to 20thNight
27%28%30%13%2
760
21st to endNight
21%29%32%14%4
835
February1st to 10thNight
29%29%30%11%1
720
11th to 20thNight
25%29%31%13%2
703
21st to endNight
27%28%30%14%1
592
March1st to 10thNight
26%20%34%16%3
720
11th to 20thNight
26%21%32%17%4
720
21st to endNight
23%15%34%19%7%1
792
April1st to 10thNight
26%19%34%18%3
720
11th to 20thNight
24%17%31%22%5%1
711
21st to endNight
24%12%32%25%7%
590
May1st to 10thNight
22%12%27%26%12%1
486
11th to 20thNight
15%8%33%35%8%
354
21st to endNight
11%11%31%30%16%1
389
June1st to 10thNight
14%9%35%31%11%1
360
11th to 20thNight
13%11%31%34%12%
360
21st to endNight
11%8%38%35%8%
360
July1st to 10thNight
7%5%30%37%19%2
350
11th to 20thNight
10%8%31%31%19%1
348
21st to endNight
11%5%29%37%15%3
484
August1st to 10thNight
10%426%35%21%3
537
11th to 20thNight
10%5%24%34%24%3
534
21st to endNight
11%7%27%32%22%2
745
September1st to 10thNight
16%8%25%30%18%3
720
11th to 20thNight
16%6%22%28%23%5%
720
21st to endNight
17%11%23%29%17%3
720
October1st to 10thNight
22%13%26%23%14%2
720
11th to 20thNight
24%19%30%20%6%1
720
21st to endNight
34%15%29%20%3
792
November1st to 10thNight
24%16%29%24%7%1
740
11th to 20thNight
23%23%29%16%7%1
760
21st to endNight
27%23%30%14%6%
760
December1st to 10thNight
33%25%27%11%4
760
11th to 20thNight
25%28%29%15%3
760
21st to endNight
33%24%29%12%2
836
Page generated at 2024-01-28 05:26:33. Version ac07

Copyright 2024 Attilla Danko


Brockport State Observatory Clear Sky Chart |Charts Home