Burkes Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Burkes Observatory clear sky chart from 2005-11-05 to 2017-10-31.

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
29%
14964
16%
47365
8%
14932
39%
14932
19%
32090

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%
720
16%
2506
6%
716
35%
716
16%
1651
January16th to endNight
18%
768
16%
2688
4%
768
33%
768
14%
1804
February1st to 15thNight
21%
704
13%
2274
6%
701
32%
701
15%
1620
February16th to endNight
20%
631
17%
1893
6%
631
34%
631
17%
1327
March1st to 15thNight
19%
720
16%
2109
5%
720
31%
720
16%
1532
March16th to endNight
27%
768
18%
2097
7%
768
36%
768
21%
1435
April1st to 15thNight
20%
688
17%
1766
4%
688
30%
688
19%
1291
April16th to endNight
25%
540
15%
1620
5%
540
32%
540
17%
1139
May1st to 15thNight
27%
540
13%
1620
7%
540
34%
540
17%
1161
May16th to endNight
24%
423
11%
1527
7%
422
33%
422
13%
1091
June1st to 15thNight
31%
360
9%
1260
7%
360
37%
360
14%
919
June16th to endNight
42%
360
9%
1260
9%
360
47%
360
21%
835
July1st to 15thNight
45%
340
10%
1347
13%
340
50%
340
20%
858
July16th to endNight
48%
376
12%
1418
10%
354
54%
354
19%
891
August1st to 15thNight
43%
521
12%
1592
9%
519
47%
519
23%
1053
August16th to endNight
48%
600
21%
1746
13%
600
52%
600
32%
1068
September1st to 15thNight
41%
720
17%
1902
8%
720
46%
720
32%
1216
September16th to endNight
42%
717
26%
1980
15%
717
51%
717
35%
1191
October1st to 15thNight
37%
720
19%
2057
9%
720
46%
720
25%
1362
October16th to endNight
24%
768
16%
2467
7%
768
35%
768
18%
1684
November1st to 15thNight
31%
700
20%
2277
11%
700
42%
700
20%
1518
November16th to endNight
29%
738
17%
2448
8%
738
41%
738
17%
1626
December1st to 15thNight
18%
750
14%
2679
5%
750
31%
750
15%
1851
December16th to endNight
18%
792
16%
2832
5%
792
32%
792
14%
1967

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
19%7%25%5%34446%36%
48374
Night
18%7%35%424446%36%
47535
TransparencyDay
47%5%11%20%12%1
48062
Night
47%5%11%21%12%1
47365
SeeingDay
24%11%30%21%9%2
6427
Night
22%10%31%26%7%
14964

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
17%8%35%5%3345%5%37%
1432
16th to endDay
15%10%36%6%23446%37%
1536
February1st to 15thDay
15%11%37%5%35%445%33%
1584
16th to endDay
14%10%47%5%36%5%46%31%
1580
March1st to 15thDay
20%9%35%5%34345%34%
1840
16th to endDay
17%6%35%43334440%
2124
April1st to 15thDay
21%8%35%5%23345%35%
2182
16th to endDay
21%7%25%423346%36%
2340
May1st to 15thDay
26%6%26%5%24447%29%
2332
16th to endDay
24%5%244445%47%31%
2594
June1st to 15thDay
26%7%46%434346%28%
2700
16th to endDay
22%6%25%5%25%46%7%30%
2700
July1st to 15thDay
13%5%25%6%36%6%6%8%36%
2529
16th to endDay
14%6%26%6%36%5%6%7%32%
2654
August1st to 15thDay
16%5%15%5%36%6%6%8%34%
2343
16th to endDay
12%4244245%47%46%
2453
September1st to 15thDay
12%5%25%5%3435%5%44%
2058
16th to endDay
14%5%2331335%7%49%
1980
October1st to 15thDay
20%6%24423346%40%
1902
16th to endDay
21%7%25%43424437%
1753
November1st to 15thDay
21%5%25%425%5%46%37%
1581
16th to endDay
21%6%15%334335%40%
1510
December1st to 15thDay
23%8%25%423445%33%
1278
16th to endDay
23%11%35%424345%31%
1389
January1st to 15thNight
15%10%25%5%3445%6%37%
2506
16th to endNight
14%8%46%6%345%46%34%
2688
February1st to 15thNight
13%10%47%6%45%5%5%6%30%
2273
16th to endNight
17%11%35%5%34345%36%
1893
March1st to 15thNight
18%11%46%424435%33%
2096
16th to endNight
16%7%35%424346%40%
2097
April1st to 15thNight
20%8%45%5%23445%33%
1766
16th to endNight
23%7%25%434346%34%
1620
May1st to 15thNight
22%7%35%4245%6%6%31%
1620
16th to endNight
22%7%46%5%34447%29%
1525
June1st to 15thNight
22%9%46%5%2435%6%27%
1260
16th to endNight
19%5%35%43445%9%35%
1260
July1st to 15thNight
15%5%346%35%5%6%8%35%
1427
16th to endNight
15%425%5%345%6%9%36%
1514
August1st to 15thNight
12%6%25%6%25%5%6%8%38%
1602
16th to endNight
12%5%1442336%7%48%
1746
September1st to 15thNight
15%5%24324437%48%
1902
16th to endNight
14%414224336%52%
1980
October1st to 15thNight
19%5%24334446%41%
2057
16th to endNight
22%7%25%424346%36%
2467
November1st to 15thNight
19%6%25%5%24446%37%
2277
16th to endNight
18%7%35%43445%6%37%
2448
December1st to 15thNight
22%9%34434445%33%
2679
16th to endNight
22%11%34324446%32%
2832

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
46%412%19%13%2
1433
16th to endDay
47%5%12%22%11%1
1536
February1st to 15thDay
52%412%18%11%
1587
16th to endDay
51%6%10%17%11%3
1580
March1st to 15thDay
53%310%17%12%2
1850
16th to endDay
45%5%8%19%17%3
2124
April1st to 15thDay
50%36%19%15%2
2182
16th to endDay
48%410%20%12%4
2340
May1st to 15thDay
54%5%8%17%11%2
2332
16th to endDay
51%7%11%18%10%1
2598
June1st to 15thDay
57%5%10%17%8%
2700
16th to endDay
51%6%12%17%11%
2700
July1st to 15thDay
41%8%14%24%10%
2380
16th to endDay
47%7%14%21%9%1
2487
August1st to 15thDay
45%6%15%23%8%
2329
16th to endDay
35%6%14%24%17%1
2453
September1st to 15thDay
39%5%11%25%16%1
2058
16th to endDay
33%410%29%21%1
1980
October1st to 15thDay
44%411%24%13%
1902
16th to endDay
49%411%23%10%
1753
November1st to 15thDay
45%6%14%19%13%1
1581
16th to endDay
46%5%13%19%13%1
1510
December1st to 15thDay
51%5%12%20%8%
1278
16th to endDay
55%5%9%17%11%
1389
January1st to 15thNight
46%5%13%21%11%1
2506
16th to endNight
49%5%9%21%12%1
2688
February1st to 15thNight
52%412%19%9%1
2274
16th to endNight
50%410%19%13%2
1893
March1st to 15thNight
53%48%18%12%2
2109
16th to endNight
45%411%18%17%3
2097
April1st to 15thNight
52%48%17%15%1
1766
16th to endNight
50%5%10%16%13%3
1620
May1st to 15thNight
51%6%9%17%12%1
1620
16th to endNight
53%6%10%18%8%
1527
June1st to 15thNight
57%413%16%6%1
1260
16th to endNight
45%6%15%19%11%
1260
July1st to 15thNight
42%7%15%21%11%
1347
16th to endNight
41%8%16%23%8%
1418
August1st to 15thNight
41%8%16%24%9%
1592
16th to endNight
33%6%14%29%13%1
1746
September1st to 15thNight
36%5%12%30%14%
1902
16th to endNight
34%310%32%17%1
1980
October1st to 15thNight
42%5%11%24%14%1
2057
16th to endNight
49%411%23%10%
2467
November1st to 15thNight
45%6%12%21%13%1
2277
16th to endNight
46%5%13%20%13%1
2448
December1st to 15thNight
51%5%11%22%9%
2679
16th to endNight
53%411%19%11%
2832

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
21%16%36%20%5%
60
16th to endDay
21%18%37%17%4
64
February1st to 15thDay
26%12%34%20%4
228
16th to endDay
16%20%33%23%6%
239
March1st to 15thDay
31%15%32%16%4
270
16th to endDay
24%20%25%18%6%3
288
April1st to 15thDay
29%17%30%15%5%2
270
16th to endDay
30%16%31%12%7%2
270
May1st to 15thDay
35%12%27%17%6%1
288
16th to endDay
28%13%33%19%4
346
June1st to 15thDay
29%10%27%21%10%
495
16th to endDay
24%8%28%27%8%1
495
July1st to 15thDay
17%8%33%24%14%1
314
16th to endDay
14%5%35%28%11%4
326
August1st to 15thDay
16%8%30%29%13%2
313
16th to endDay
17%8%26%26%15%5%
332
September1st to 15thDay
17%7%30%26%11%6%
315
16th to endDay
17%8%27%20%15%10%
314
October1st to 15thDay
22%13%23%20%15%4
295
16th to endDay
26%12%32%21%41
288
November1st to 15thDay
24%9%29%22%11%2
235
16th to endDay
28%13%25%24%7%
240
December1st to 15thDay
30%7%41%15%5%
78
16th to endDay
37%17%34%10%
64
January1st to 15thNight
20%15%36%23%3
720
16th to endNight
20%15%37%21%3
768
February1st to 15thNight
20%14%36%25%3
704
16th to endNight
21%14%36%22%4
631
March1st to 15thNight
25%14%35%20%3
720
16th to endNight
21%16%31%23%6%
768
April1st to 15thNight
25%15%34%21%3
688
16th to endNight
29%11%30%23%5%
540
May1st to 15thNight
25%11%30%26%5%
540
16th to endNight
24%8%35%25%6%
423
June1st to 15thNight
28%5%26%33%6%
360
16th to endNight
21%128%39%9%
360
July1st to 15thNight
17%227%39%13%
340
16th to endNight
15%224%42%14%
376
August1st to 15thNight
13%427%39%14%
521
16th to endNight
15%426%37%15%
600
September1st to 15thNight
17%430%33%11%1
720
16th to endNight
16%5%31%27%16%2
717
October1st to 15thNight
22%6%29%29%11%1
720
16th to endNight
26%13%31%22%6%
768
November1st to 15thNight
23%10%28%27%8%1
700
16th to endNight
22%15%28%24%8%
738
December1st to 15thNight
27%10%37%20%4
750
16th to endNight
31%13%32%19%3
792
Page generated at 2017-11-01 17:23:39. Version ac04

Copyright 2017 A. Danko


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