Brooke Stream Manor Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Brooke Stream Manor Observatory clear sky chart from 2005-11-05 to 2017-09-23.

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
37%
15265
22%
46964
12%
15227
48%
15227
25%
29023

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
20%
717
22%
2395
8%
716
38%
716
18%
1499
January16th to endNight
18%
768
22%
2496
6%
768
38%
768
20%
1551
February1st to 15thNight
21%
702
21%
2287
6%
701
39%
701
20%
1389
February16th to endNight
16%
631
24%
1938
6%
631
37%
631
19%
1199
March1st to 15thNight
22%
720
23%
1980
8%
720
37%
720
23%
1267
March16th to endNight
21%
768
21%
2103
9%
768
33%
768
22%
1397
April1st to 15thNight
27%
718
19%
1796
5%
718
36%
718
27%
1191
April16th to endNight
38%
720
20%
1800
8%
720
44%
720
30%
1187
May1st to 15thNight
40%
549
18%
1629
9%
549
46%
549
24%
1080
May16th to endNight
51%
379
18%
1502
16%
379
58%
379
23%
861
June1st to 15thNight
55%
360
20%
1440
19%
360
63%
360
26%
807
June16th to endNight
60%
360
19%
1440
20%
360
67%
360
28%
789
July1st to 15thNight
56%
354
13%
1374
14%
354
59%
354
21%
833
July16th to endNight
73%
564
18%
1595
13%
531
79%
531
40%
889
August1st to 15thNight
65%
539
20%
1609
15%
536
67%
536
32%
1017
August16th to endNight
63%
735
22%
1881
15%
735
64%
735
35%
1204
September1st to 15thNight
53%
720
25%
1800
14%
720
57%
720
35%
1162
September16th to endNight
53%
689
24%
1903
20%
689
56%
689
29%
1257
October1st to 15thNight
45%
660
26%
1980
21%
660
55%
660
27%
1241
October16th to endNight
34%
704
30%
2112
16%
704
53%
704
31%
1212
November1st to 15thNight
35%
700
26%
2200
16%
700
50%
700
27%
1305
November16th to endNight
30%
720
23%
2496
12%
720
46%
720
22%
1452
December1st to 15thNight
26%
720
19%
2520
7%
720
40%
720
18%
1569
December16th to endNight
22%
768
22%
2688
7%
768
40%
768
19%
1665

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
14%5%245%3445%7%41%
47923
Night
14%5%2442445%7%43%
47148
Cloud CoverDay
14%5%245%3445%7%41%
47933
Night
14%5%2442445%7%43%
47152
TransparencyDay
40%411%24%16%2
47625
Night
39%411%24%17%3
46964
SeeingDay
18%10%23%23%16%7%
5658
Night
17%11%26%28%13%1
15271

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%5%245%245%5%6%40%
1540
16th to endDay
14%7%24433446%41%
1728
February1st to 15thDay
12%8%25%5%35%5%5%5%39%
1575
16th to endDay
12%6%35%5%24447%41%
1533
March1st to 15thDay
16%5%24434246%44%
1966
16th to endDay
17%5%25%5%2445%6%38%
2119
April1st to 15thDay
13%435%42445%6%43%
2152
16th to endDay
17%5%3442335%6%43%
2160
May1st to 15thDay
17%5%244245%5%9%36%
2331
16th to endDay
15%4246%245%5%7%39%
2610
June1st to 15thDay
11%424425%5%7%9%42%
2520
16th to endDay
9%3246%35%5%7%9%43%
2520
July1st to 15thDay
9%5%36%6%36%5%6%8%38%
2502
16th to endDay
7%3146%37%6%8%11%38%
2465
August1st to 15thDay
10%5%25%7%36%5%7%8%36%
2340
16th to endDay
12%4235%35%5%7%8%42%
2308
September1st to 15thDay
14%425%5%33447%44%
2160
16th to endDay
15%6%25%5%34446%41%
1889
October1st to 15thDay
20%414323336%46%
1650
16th to endDay
14%424424345%49%
1760
November1st to 15thDay
13%5%24324446%48%
1657
16th to endDay
17%425%424446%43%
1462
December1st to 15thDay
15%5%15%435%46%6%40%
1440
16th to endDay
17%7%24424446%39%
1536
January1st to 15thNight
16%6%25%434447%40%
2395
16th to endNight
16%7%2442345%6%42%
2496
February1st to 15thNight
12%6%25%424446%44%
2285
16th to endNight
13%6%25%5%15%45%6%42%
1938
March1st to 15thNight
17%5%2332445%5%44%
1968
16th to endNight
16%6%25%42435%5%41%
2103
April1st to 15thNight
13%5%26%43445%7%41%
1796
16th to endNight
14%5%25%42345%7%43%
1800
May1st to 15thNight
17%6%15%43445%8%38%
1629
16th to endNight
13%5%244245%6%8%42%
1500
June1st to 15thNight
11%324435%5%6%8%45%
1440
16th to endNight
8%434425%5%7%10%43%
1440
July1st to 15thNight
9%425%6%36%6%8%9%36%
1455
16th to endNight
5%223336%5%8%11%46%
1703
August1st to 15thNight
7%5%15%5%35%6%5%9%43%
1620
16th to endNight
11%413435%46%8%44%
1881
September1st to 15thNight
13%425%43336%6%46%
1800
16th to endNight
15%6%25%423445%44%
1903
October1st to 15thNight
20%414323435%46%
1980
16th to endNight
13%413422346%53%
2112
November1st to 15thNight
13%6%25%31334451%
2200
16th to endNight
17%4143245%5%8%44%
2496
December1st to 15thNight
17%5%25%5%3445%6%39%
2520
16th to endNight
17%5%25%425%45%7%39%
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%5%25%5%245%5%6%40%
1540
16th to endDay
14%8%244245%46%41%
1728
February1st to 15thDay
13%8%25%5%35%6%5%6%38%
1575
16th to endDay
12%6%45%5%34447%41%
1533
March1st to 15thDay
16%5%245%34246%44%
1977
16th to endDay
17%6%25%6%2445%6%39%
2118
April1st to 15thDay
13%435%5%3445%6%43%
2152
16th to endDay
17%4345%24445%43%
2160
May1st to 15thDay
17%6%15%425%5%5%8%36%
2331
16th to endDay
15%425%5%245%6%7%39%
2610
June1st to 15thDay
11%424435%5%7%9%42%
2520
16th to endDay
9%3245%35%5%6%9%43%
2520
July1st to 15thDay
9%5%35%5%46%5%7%8%38%
2502
16th to endDay
7%3246%46%7%8%11%38%
2465
August1st to 15thDay
10%5%25%6%35%6%7%8%36%
2340
16th to endDay
12%4135%35%5%6%8%42%
2308
September1st to 15thDay
14%415%433447%44%
2160
16th to endDay
15%5%25%5%34447%40%
1889
October1st to 15thDay
20%414314236%46%
1650
16th to endDay
14%424423345%49%
1760
November1st to 15thDay
13%5%24323445%48%
1657
16th to endDay
17%424423446%43%
1462
December1st to 15thDay
16%5%245%35%46%6%40%
1440
16th to endDay
17%7%24435%446%39%
1536
January1st to 15thNight
16%6%34424447%40%
2395
16th to endNight
17%6%25%32345%6%41%
2496
February1st to 15thNight
12%6%25%42445%6%44%
2278
16th to endNight
13%6%26%5%2445%6%43%
1938
March1st to 15thNight
16%42342445%6%44%
1980
16th to endNight
16%6%25%43445%5%41%
2103
April1st to 15thNight
13%5%26%43445%7%41%
1796
16th to endNight
14%5%2442346%7%43%
1800
May1st to 15thNight
17%6%25%43345%8%37%
1628
16th to endNight
13%5%25%425%45%9%42%
1500
June1st to 15thNight
10%324435%6%5%7%46%
1440
16th to endNight
8%4244345%8%9%43%
1440
July1st to 15thNight
9%425%6%36%6%7%9%37%
1455
16th to endNight
5%223426%6%7%12%46%
1703
August1st to 15thNight
7%5%25%445%6%5%8%43%
1620
16th to endNight
11%423425%5%6%9%43%
1881
September1st to 15thNight
13%425%43345%6%46%
1800
16th to endNight
15%6%25%424345%44%
1903
October1st to 15thNight
20%413423335%46%
1980
16th to endNight
13%413323336%53%
2112
November1st to 15thNight
14%5%35%31334451%
2200
16th to endNight
16%4143135%5%8%44%
2496
December1st to 15thNight
16%5%25%5%3445%6%39%
2520
16th to endNight
16%6%25%425%45%7%40%
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
42%411%23%14%3
1541
16th to endDay
42%310%25%14%3
1728
February1st to 15thDay
44%411%23%14%2
1577
16th to endDay
42%310%26%14%1
1533
March1st to 15thDay
41%310%24%15%3
1977
16th to endDay
45%311%19%17%2
2119
April1st to 15thDay
40%310%22%18%3
2152
16th to endDay
41%48%20%19%5%
2160
May1st to 15thDay
44%413%20%15%1
2331
16th to endDay
42%413%26%12%1
2614
June1st to 15thDay
35%6%14%27%14%1
2520
16th to endDay
33%6%16%24%16%1
2520
July1st to 15thDay
40%6%11%23%15%2
2354
16th to endDay
34%6%15%26%15%1
2310
August1st to 15thDay
41%5%12%22%16%
2327
16th to endDay
36%6%12%27%14%2
2308
September1st to 15thDay
38%410%20%22%3
2160
16th to endDay
42%46%25%20%1
1889
October1st to 15thDay
40%39%27%16%3
1650
16th to endDay
37%28%28%21%1
1760
November1st to 15thDay
37%210%22%19%6%
1657
16th to endDay
41%310%26%15%2
1462
December1st to 15thDay
42%314%23%12%3
1440
16th to endDay
45%211%25%13%1
1536
January1st to 15thNight
43%310%20%17%4
2395
16th to endNight
42%212%25%16%1
2496
February1st to 15thNight
39%310%26%16%2
2287
16th to endNight
40%39%28%16%1
1938
March1st to 15thNight
39%411%29%12%2
1980
16th to endNight
43%310%21%17%2
2103
April1st to 15thNight
40%310%22%20%3
1796
16th to endNight
38%410%22%17%7%
1800
May1st to 15thNight
44%410%22%14%3
1629
16th to endNight
37%5%16%24%14%2
1502
June1st to 15thNight
35%5%13%27%17%1
1440
16th to endNight
32%5%14%25%18%2
1440
July1st to 15thNight
40%7%14%20%13%4
1374
16th to endNight
26%6%20%25%19%1
1595
August1st to 15thNight
36%6%11%25%18%2
1609
16th to endNight
35%5%12%24%19%2
1881
September1st to 15thNight
37%411%22%21%3
1800
16th to endNight
42%46%23%20%3
1903
October1st to 15thNight
40%37%26%19%2
1980
16th to endNight
32%28%30%23%2
2112
November1st to 15thNight
36%36%23%21%7%
2200
16th to endNight
37%310%25%18%4
2496
December1st to 15thNight
44%211%24%14%1
2520
16th to endNight
42%413%24%13%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
32%30%21%11%3
78
16th to endDay
28%36%21%13%
96
February1st to 15thDay
30%32%32%41
90
16th to endDay
21%25%30%20%1
192
March1st to 15thDay
22%19%27%24%5%
270
16th to endDay
20%16%32%19%6%3
288
April1st to 15thDay
16%16%30%21%12%2
270
16th to endDay
22%10%26%17%18%5%
270
May1st to 15thDay
28%17%22%14%12%4
288
16th to endDay
20%5%20%24%21%8%
331
June1st to 15thDay
15%7%24%23%20%8%
315
16th to endDay
10%5%29%31%16%6%
315
July1st to 15thDay
16%321%26%24%6%
305
16th to endDay
9%212%36%26%13%
326
August1st to 15thDay
13%419%23%24%14%
313
16th to endDay
11%13%33%23%17%
332
September1st to 15thDay
17%6%15%23%20%16%
315
16th to endDay
22%119%24%19%13%
283
October1st to 15thDay
23%418%25%20%7%
255
16th to endDay
13%15%28%25%14%1
272
November1st to 15thDay
17%9%26%25%16%4
248
16th to endDay
23%19%29%18%7%2
82
December1st to 15thDay
20%28%25%15%10%1
60
16th to endDay
28%20%32%18%
64
January1st to 15thNight
23%18%31%21%5%
720
16th to endNight
22%18%35%21%2
768
February1st to 15thNight
18%18%35%26%2
704
16th to endNight
21%22%35%19%2
631
March1st to 15thNight
23%16%34%21%3
720
16th to endNight
20%18%34%19%5%1
768
April1st to 15thNight
17%15%35%26%4
718
16th to endNight
19%10%25%30%13%
720
May1st to 15thNight
21%6%25%33%12%
549
16th to endNight
17%316%41%18%1
380
June1st to 15thNight
11%322%36%24%1
360
16th to endNight
8%318%47%20%1
360
July1st to 15thNight
11%218%37%27%1
354
16th to endNight
7%111%39%33%5%
564
August1st to 15thNight
10%210%43%28%3
539
16th to endNight
13%212%38%29%4
735
September1st to 15thNight
14%319%31%27%4
720
16th to endNight
17%415%30%29%3
689
October1st to 15thNight
21%7%19%27%21%2
660
16th to endNight
16%14%30%26%11%
704
November1st to 15thNight
16%13%28%28%12%1
700
16th to endNight
20%17%26%25%9%
720
December1st to 15thNight
21%15%32%22%7%
720
16th to endNight
21%14%36%25%1
768
Page generated at 2017-09-24 09:15:53. Version ac04

Copyright 2017 A. Danko


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