Thomas J Boyce Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Thomas J Boyce Park clear sky chart from 2005-11-05 to 2017-12-04.

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
26%
15264
18%
47811
8%
15232
38%
15232
17%
31280

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
16%
720
19%
2506
7%
716
32%
716
13%
1615
January16th to endNight
14%
768
19%
2634
5%
768
34%
768
12%
1704
February1st to 15thNight
13%
704
16%
2219
3%
701
29%
701
13%
1507
February16th to endNight
14%
631
21%
1893
6%
631
32%
631
14%
1247
March1st to 15thNight
15%
720
17%
2160
5%
720
28%
720
12%
1465
March16th to endNight
17%
768
23%
1995
5%
768
31%
768
16%
1341
April1st to 15thNight
15%
718
15%
1796
2%
718
23%
718
15%
1303
April16th to endNight
21%
674
17%
1754
2%
674
30%
674
17%
1227
May1st to 15thNight
20%
503
16%
1583
5%
503
31%
503
13%
1087
May16th to endNight
31%
375
13%
1497
11%
374
39%
374
14%
963
June1st to 15thNight
30%
360
13%
1440
8%
360
43%
360
15%
946
June16th to endNight
41%
360
14%
1440
13%
360
51%
360
21%
837
July1st to 15thNight
45%
340
13%
1360
15%
340
51%
340
20%
815
July16th to endNight
44%
376
15%
1418
15%
354
53%
354
20%
851
August1st to 15thNight
46%
514
17%
1585
10%
512
52%
512
26%
964
August16th to endNight
53%
764
19%
1910
9%
764
56%
764
30%
1280
September1st to 15thNight
38%
720
22%
1803
9%
720
44%
720
30%
1179
September16th to endNight
44%
717
27%
1980
16%
717
52%
717
29%
1227
October1st to 15thNight
34%
720
21%
2088
12%
720
43%
720
22%
1350
October16th to endNight
25%
768
18%
2426
9%
768
38%
768
18%
1581
November1st to 15thNight
27%
760
20%
2472
10%
760
41%
760
18%
1570
November16th to endNight
23%
780
21%
2590
10%
780
37%
780
16%
1662
December1st to 15thNight
21%
736
15%
2574
5%
736
32%
736
11%
1737
December16th to endNight
12%
768
17%
2688
4%
768
29%
768
10%
1822

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%6%25%5%3445%7%38%
48689
Night
15%6%35%43445%6%40%
47981
Cloud CoverDay
16%6%25%5%3445%7%38%
48699
Night
15%6%25%42445%6%40%
47986
TransparencyDay
44%6%11%21%14%1
48377
Night
43%6%12%22%14%1
47811
SeeingDay
20%20%26%18%9%3
6041
Night
18%26%23%21%7%
15264

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
14%6%35%6%35%5%5%6%39%
1432
16th to endDay
14%6%35%5%25%46%7%38%
1587
February1st to 15thDay
15%7%26%6%36%5%5%6%33%
1640
16th to endDay
14%7%36%6%35%347%37%
1580
March1st to 15thDay
16%6%37%6%25%446%34%
1790
16th to endDay
18%6%35%424246%39%
2228
April1st to 15thDay
19%8%34434445%37%
2152
16th to endDay
17%6%24423347%43%
2205
May1st to 15thDay
22%7%35%425%45%6%33%
2378
16th to endDay
16%6%35%5%25%45%7%37%
2618
June1st to 15thDay
22%5%24435%5%6%8%31%
2520
16th to endDay
12%6%36%6%35%45%10%35%
2520
July1st to 15thDay
12%6%25%6%35%46%8%37%
2520
16th to endDay
12%5%25%5%35%6%6%8%38%
2654
August1st to 15thDay
14%5%245%35%5%6%8%38%
2351
16th to endDay
11%6%244345%5%8%43%
2292
September1st to 15thDay
13%5%245%4445%6%42%
2155
16th to endDay
12%5%2432445%7%47%
1980
October1st to 15thDay
19%7%1442435%5%42%
1870
16th to endDay
19%5%146%35%346%39%
1797
November1st to 15thDay
16%7%23413347%43%
1716
16th to endDay
18%42432435%7%43%
1700
December1st to 15thDay
16%7%37%424446%36%
1468
16th to endDay
19%8%35%5%245%6%7%31%
1536
January1st to 15thNight
15%7%35%4345%46%39%
2506
16th to endNight
14%8%35%43445%5%39%
2634
February1st to 15thNight
13%7%45%5%36%45%5%36%
2218
16th to endNight
15%7%245%25%35%6%40%
1893
March1st to 15thNight
18%5%25%4245%5%6%37%
2147
16th to endNight
17%6%3443445%6%41%
1995
April1st to 15thNight
17%7%36%5%4445%5%34%
1796
16th to endNight
17%6%35%433345%41%
1754
May1st to 15thNight
19%7%35%5%44436%35%
1583
16th to endNight
16%6%245%25%45%8%37%
1495
June1st to 15thNight
18%6%344245%5%6%38%
1440
16th to endNight
12%4233245%5%10%44%
1440
July1st to 15thNight
12%6%33435%5%6%7%41%
1440
16th to endNight
9%5%246%25%5%6%8%41%
1514
August1st to 15thNight
11%314425%5%6%7%45%
1595
16th to endNight
13%4245%2446%6%45%
1910
September1st to 15thNight
14%5%23323346%48%
1803
16th to endNight
13%5%24323446%50%
1980
October1st to 15thNight
15%5%26%423346%45%
2088
16th to endNight
18%7%145%2435%6%39%
2426
November1st to 15thNight
16%7%25%42345%5%42%
2472
16th to endNight
16%6%35%5%2445%6%39%
2590
December1st to 15thNight
19%5%35%5%245%5%6%35%
2574
16th to endNight
19%7%35%43445%6%33%
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
14%6%26%6%35%446%39%
1432
16th to endDay
14%6%35%5%25%45%7%38%
1587
February1st to 15thDay
15%7%26%5%35%5%5%7%34%
1640
16th to endDay
14%7%35%5%36%346%38%
1580
March1st to 15thDay
17%7%36%7%3445%6%35%
1800
16th to endDay
18%7%35%423346%40%
2228
April1st to 15thDay
19%8%245%24436%37%
2152
16th to endDay
16%6%24424346%43%
2205
May1st to 15thDay
21%7%2443445%5%34%
2378
16th to endDay
16%6%25%43445%6%37%
2618
June1st to 15thDay
21%5%24425%5%6%8%32%
2520
16th to endDay
12%6%26%6%45%5%5%9%35%
2520
July1st to 15thDay
12%6%35%5%46%46%8%37%
2520
16th to endDay
11%5%25%5%36%5%6%8%37%
2654
August1st to 15thDay
13%6%15%5%35%5%6%8%37%
2351
16th to endDay
11%5%344245%7%8%42%
2292
September1st to 15thDay
13%425%5%35%447%42%
2155
16th to endDay
12%5%15%424447%46%
1980
October1st to 15thDay
18%7%24423445%42%
1870
16th to endDay
18%5%246%2445%5%40%
1797
November1st to 15thDay
17%7%23323346%43%
1716
16th to endDay
18%5%24313347%44%
1700
December1st to 15thDay
16%7%36%5%34445%37%
1468
16th to endDay
19%7%36%4245%5%7%32%
1536
January1st to 15thNight
16%7%2443445%6%40%
2506
16th to endNight
14%8%345%2445%6%39%
2634
February1st to 15thNight
13%8%35%5%35%5%46%37%
2211
16th to endNight
15%6%345%2445%6%40%
1893
March1st to 15thNight
18%5%35%4245%5%6%37%
2160
16th to endNight
16%6%25%424446%42%
1994
April1st to 15thNight
16%8%36%5%3445%6%35%
1796
16th to endNight
17%6%35%424336%41%
1754
May1st to 15thNight
18%7%26%5%34446%35%
1583
16th to endNight
17%7%2443445%7%37%
1495
June1st to 15thNight
19%5%25%42446%6%38%
1440
16th to endNight
11%425%4245%6%9%44%
1440
July1st to 15thNight
12%6%344346%6%9%39%
1440
16th to endNight
10%5%25%5%26%5%6%8%40%
1514
August1st to 15thNight
11%4235%15%5%7%8%44%
1595
16th to endNight
13%4245%3345%7%44%
1910
September1st to 15thNight
14%6%23423346%48%
1803
16th to endNight
13%5%24323436%50%
1980
October1st to 15thNight
15%7%25%422345%45%
2088
16th to endNight
18%5%25%433446%40%
2426
November1st to 15thNight
15%7%24423445%43%
2472
16th to endNight
16%6%35%424447%39%
2590
December1st to 15thNight
19%6%25%43445%5%36%
2574
16th to endNight
19%7%25%43446%6%34%
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
43%6%12%23%10%2
1433
16th to endDay
42%6%12%23%12%1
1587
February1st to 15thDay
48%7%11%18%12%1
1643
16th to endDay
46%5%10%23%12%1
1580
March1st to 15thDay
49%412%21%9%1
1800
16th to endDay
45%410%19%17%2
2228
April1st to 15thDay
47%6%8%20%14%2
2152
16th to endDay
41%49%22%18%3
2205
May1st to 15thDay
50%6%7%19%13%2
2378
16th to endDay
45%8%11%20%12%1
2622
June1st to 15thDay
50%7%12%19%9%1
2520
16th to endDay
43%8%14%21%11%
2520
July1st to 15thDay
44%7%11%20%14%1
2371
16th to endDay
41%7%14%21%13%1
2487
August1st to 15thDay
42%8%13%21%13%
2337
16th to endDay
38%6%10%25%17%
2292
September1st to 15thDay
41%7%10%21%18%1
2155
16th to endDay
36%6%9%21%24%2
1980
October1st to 15thDay
44%5%9%24%14%2
1870
16th to endDay
45%5%11%22%13%1
1797
November1st to 15thDay
40%5%14%21%15%2
1716
16th to endDay
41%312%26%14%2
1700
December1st to 15thDay
47%5%15%19%11%
1468
16th to endDay
51%6%13%18%9%
1536
January1st to 15thNight
44%5%13%21%12%2
2506
16th to endNight
43%6%10%22%14%2
2634
February1st to 15thNight
46%6%13%19%11%2
2219
16th to endNight
43%5%11%21%15%2
1893
March1st to 15thNight
45%6%13%21%11%2
2160
16th to endNight
42%5%9%20%17%4
1995
April1st to 15thNight
46%6%10%20%13%1
1796
16th to endNight
44%5%7%21%17%2
1754
May1st to 15thNight
49%5%10%18%13%2
1583
16th to endNight
45%6%15%18%11%1
1497
June1st to 15thNight
47%6%12%20%11%1
1440
16th to endNight
35%8%16%26%13%
1440
July1st to 15thNight
39%6%13%26%12%1
1360
16th to endNight
38%7%14%23%13%2
1418
August1st to 15thNight
34%8%15%26%14%1
1585
16th to endNight
36%8%11%25%17%
1910
September1st to 15thNight
37%5%10%26%19%
1803
16th to endNight
35%5%6%24%26%1
1980
October1st to 15thNight
41%5%11%22%17%2
2088
16th to endNight
43%5%13%23%13%
2426
November1st to 15thNight
41%5%11%20%16%3
2472
16th to endNight
44%412%24%12%1
2590
December1st to 15thNight
47%7%14%20%11%
2574
16th to endNight
48%6%12%20%11%
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
26%31%26%11%3
60
16th to endDay
30%19%42%8%
73
February1st to 15thDay
26%37%21%14%
156
16th to endDay
22%31%29%14%2
239
March1st to 15thDay
27%27%30%11%2
270
16th to endDay
22%31%28%10%6%
288
April1st to 15thDay
27%25%25%12%7%
270
16th to endDay
21%24%31%11%8%2
270
May1st to 15thDay
34%24%20%12%43
288
16th to endDay
16%20%28%23%9%1
331
June1st to 15thDay
22%20%25%18%11%1
315
16th to endDay
15%21%29%18%12%2
315
July1st to 15thDay
17%11%29%27%11%2
305
16th to endDay
13%14%27%25%16%3
326
August1st to 15thDay
16%11%25%25%14%7%
313
16th to endDay
12%9%25%26%13%12%
332
September1st to 15thDay
13%16%25%20%15%8%
315
16th to endDay
15%12%24%19%14%13%
314
October1st to 15thDay
23%11%24%20%16%3
315
16th to endDay
22%21%23%22%9%
305
November1st to 15thDay
21%23%23%19%9%2
280
16th to endDay
23%29%21%16%7%1
230
December1st to 15thDay
28%23%23%17%41
67
16th to endDay
40%25%25%9%
64
January1st to 15thNight
19%34%26%15%2
720
16th to endNight
19%36%26%16%1
768
February1st to 15thNight
19%32%29%17%1
704
16th to endNight
21%34%26%14%2
631
March1st to 15thNight
23%35%22%16%2
720
16th to endNight
18%37%22%16%5%
768
April1st to 15thNight
20%33%28%13%3
718
16th to endNight
17%33%24%17%6%
674
May1st to 15thNight
21%30%25%16%5%
503
16th to endNight
18%23%22%28%6%
375
June1st to 15thNight
17%22%25%22%11%
360
16th to endNight
13%19%22%35%8%
360
July1st to 15thNight
15%14%20%33%15%
340
16th to endNight
10%19%18%34%16%1
376
August1st to 15thNight
14%11%22%35%14%1
514
16th to endNight
13%10%15%35%22%2
764
September1st to 15thNight
14%15%25%28%13%2
720
16th to endNight
15%13%20%24%19%5%
717
October1st to 15thNight
19%17%23%26%10%1
720
16th to endNight
21%22%27%22%6%
768
November1st to 15thNight
19%26%23%20%8%1
760
16th to endNight
17%30%24%19%7%1
780
December1st to 15thNight
24%30%20%18%5%
736
16th to endNight
25%34%24%13%2
768
Page generated at 2017-12-05 10:19:04. Version ac04

Copyright 2017 A. Danko


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