Grand-Barachois
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Grand-Barachois clear sky chart from 2005-11-05 to 2017-09-18.

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%
14894
12%
46706
5%
14849
32%
14849
15%
34179

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
15%
750
11%
2679
2%
746
27%
746
11%
1938
January16th to endNight
18%
775
15%
2541
4%
775
32%
775
15%
1743
February1st to 15thNight
17%
704
10%
2286
2%
701
27%
701
14%
1672
February16th to endNight
19%
631
10%
2051
3%
631
28%
631
11%
1564
March1st to 15thNight
21%
719
14%
1987
5%
719
29%
719
16%
1519
March16th to endNight
22%
768
14%
2112
6%
768
29%
768
16%
1597
April1st to 15thNight
22%
548
11%
1786
7%
548
28%
548
13%
1354
April16th to endNight
27%
540
14%
1620
6%
540
34%
540
19%
1169
May1st to 15thNight
27%
540
9%
1506
5%
540
31%
540
15%
1152
May16th to endNight
27%
561
10%
1496
3%
560
33%
560
19%
1126
June1st to 15thNight
31%
413
6%
1313
4%
413
33%
413
14%
1001
June16th to endNight
34%
360
7%
1260
5%
360
38%
360
14%
924
July1st to 15thNight
43%
340
11%
1190
10%
340
47%
340
21%
776
July16th to endNight
38%
536
8%
1413
6%
503
40%
503
18%
1044
August1st to 15thNight
41%
539
8%
1608
6%
535
43%
535
18%
1173
August16th to endNight
42%
573
13%
1761
8%
573
46%
573
22%
1165
September1st to 15thNight
34%
540
15%
1800
11%
540
41%
540
23%
1145
September16th to endNight
37%
663
20%
1868
13%
663
44%
663
26%
1215
October1st to 15thNight
29%
660
17%
1980
8%
660
36%
660
21%
1351
October16th to endNight
18%
704
12%
2120
4%
704
24%
704
12%
1595
November1st to 15thNight
21%
730
10%
2451
5%
730
27%
730
12%
1847
November16th to endNight
21%
750
11%
2520
5%
750
29%
750
10%
1890
December1st to 15thNight
12%
750
9%
2520
1%
750
21%
750
7%
1959
December16th to endNight
10%
800
8%
2838
1%
800
18%
800
6%
2260

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%9%36%5%34446%31%
48091
Night
19%10%36%5%24446%32%
46870
TransparencyDay
52%6%13%18%8%
47773
Night
53%6%12%18%8%
46706
SeeingDay
24%10%30%25%8%1
7237
Night
24%11%32%23%6%
14895

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%14%49%6%3334331%
1257
16th to endDay
13%11%47%6%25%345%33%
1680
February1st to 15thDay
15%12%48%5%34446%30%
1575
16th to endDay
14%13%7%7%5%35%446%26%
1422
March1st to 15thDay
18%11%6%8%5%34345%28%
1960
16th to endDay
17%13%5%7%5%24435%31%
2112
April1st to 15thDay
19%11%46%7%4445%6%27%
2162
16th to endDay
23%9%36%5%23346%31%
2340
May1st to 15thDay
23%9%36%5%34435%29%
2444
16th to endDay
24%8%46%5%23347%28%
2618
June1st to 15thDay
28%8%25%5%35%446%25%
2657
16th to endDay
23%7%36%6%25%447%28%
2700
July1st to 15thDay
14%6%25%5%35%5%6%8%35%
2700
16th to endDay
15%6%37%7%35%6%5%9%28%
2643
August1st to 15thDay
17%7%35%5%245%48%33%
2340
16th to endDay
13%6%244345%5%7%40%
2441
September1st to 15thDay
17%5%25%4345%5%7%38%
2160
16th to endDay
18%424413346%46%
1813
October1st to 15thDay
20%7%25%423347%38%
1650
16th to endDay
22%9%36%5%4445%5%28%
1749
November1st to 15thDay
24%9%36%5%23346%29%
1405
16th to endDay
15%12%5%8%6%35%45%5%26%
1440
December1st to 15thDay
23%11%36%5%33345%27%
1440
16th to endDay
22%16%46%5%22225%27%
1383
January1st to 15thNight
16%12%47%6%23345%31%
2679
16th to endNight
15%10%46%5%24346%35%
2541
February1st to 15thNight
16%12%47%5%25%5%5%5%29%
2285
16th to endNight
16%14%5%7%6%3445%5%26%
2051
March1st to 15thNight
18%12%47%5%34345%29%
1975
16th to endNight
19%13%47%43333432%
2112
April1st to 15thNight
22%12%35%6%25%345%26%
1786
16th to endNight
23%9%25%5%23325%34%
1620
May1st to 15thNight
24%9%36%5%335%45%28%
1506
16th to endNight
21%7%35%435%5%5%5%32%
1494
June1st to 15thNight
27%7%36%4245%5%6%26%
1313
16th to endNight
21%7%45%5%2445%7%30%
1260
July1st to 15thNight
14%5%244346%7%10%34%
1260
16th to endNight
16%7%36%6%45%5%5%7%30%
1510
August1st to 15thNight
18%6%37%5%35%5%46%32%
1620
16th to endNight
14%6%345%3446%8%39%
1761
September1st to 15thNight
18%5%14434338%43%
1800
16th to endNight
14%415%42435%7%46%
1868
October1st to 15thNight
17%6%36%5%33446%38%
1980
16th to endNight
25%9%36%5%32445%30%
2120
November1st to 15thNight
23%9%36%5%34445%29%
2451
16th to endNight
20%10%46%5%24345%31%
2520
December1st to 15thNight
22%11%46%5%2445%5%27%
2520
16th to endNight
25%15%5%5%42433425%
2838

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
57%5%12%13%9%1
1258
16th to endDay
52%6%11%16%13%
1680
February1st to 15thDay
55%5%12%18%7%1
1578
16th to endDay
58%6%11%15%7%1
1422
March1st to 15thDay
56%5%10%17%7%1
1971
16th to endDay
56%410%18%8%2
2112
April1st to 15thDay
57%5%9%15%10%1
2162
16th to endDay
52%5%11%17%11%1
2340
May1st to 15thDay
57%6%8%18%9%
2444
16th to endDay
56%7%11%17%6%
2622
June1st to 15thDay
59%6%11%15%6%
2657
16th to endDay
54%7%12%17%6%
2700
July1st to 15thDay
41%8%17%22%9%
2541
16th to endDay
50%8%17%17%5%
2478
August1st to 15thDay
46%8%13%23%7%
2327
16th to endDay
39%8%19%23%8%
2441
September1st to 15thDay
44%7%16%20%10%
2160
16th to endDay
39%413%27%13%1
1813
October1st to 15thDay
47%413%25%8%
1650
16th to endDay
57%6%11%17%6%
1749
November1st to 15thDay
56%7%14%12%8%
1405
16th to endDay
58%8%14%12%5%
1440
December1st to 15thDay
61%11%11%12%2
1440
16th to endDay
63%7%12%10%6%
1383
January1st to 15thNight
55%6%12%16%9%
2679
16th to endNight
50%413%21%8%
2541
February1st to 15thNight
55%5%12%16%9%
2286
16th to endNight
59%5%10%13%8%1
2051
March1st to 15thNight
57%5%10%17%8%1
1987
16th to endNight
56%48%18%10%1
2112
April1st to 15thNight
59%5%8%13%10%1
1786
16th to endNight
52%5%11%15%13%1
1620
May1st to 15thNight
56%7%10%17%7%
1506
16th to endNight
51%8%14%18%6%
1496
June1st to 15thNight
58%6%12%15%6%
1313
16th to endNight
52%9%12%17%6%
1260
July1st to 15thNight
40%10%17%24%6%
1190
16th to endNight
51%8%15%16%7%
1413
August1st to 15thNight
50%8%13%19%6%
1608
16th to endNight
42%8%17%24%6%
1761
September1st to 15thNight
41%6%13%27%10%
1800
16th to endNight
38%7%14%27%11%
1868
October1st to 15thNight
46%5%12%26%8%
1980
16th to endNight
56%5%11%17%8%
2120
November1st to 15thNight
57%6%14%14%6%
2451
16th to endNight
56%7%13%15%5%
2520
December1st to 15thNight
59%8%13%14%4
2520
16th to endNight
65%6%9%12%5%
2838

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
17%23%50%7%1
64
16th to endDay
17%12%43%23%3
256
February1st to 15thDay
21%12%36%22%5%1
236
16th to endDay
22%16%33%21%5%
212
March1st to 15thDay
22%18%31%21%41
270
16th to endDay
26%14%32%17%6%1
288
April1st to 15thDay
25%16%32%19%4
270
16th to endDay
22%14%34%18%10%
270
May1st to 15thDay
33%6%29%19%8%2
400
16th to endDay
29%8%28%28%4
519
June1st to 15thDay
34%6%27%22%7%
495
16th to endDay
26%428%32%8%1
495
July1st to 15thDay
17%432%31%11%2
475
16th to endDay
21%324%39%11%
487
August1st to 15thDay
21%321%34%16%2
313
16th to endDay
14%7%27%33%15%2
332
September1st to 15thDay
17%7%33%31%9%
315
16th to endDay
20%7%30%31%8%1
257
October1st to 15thDay
20%13%24%25%13%2
225
16th to endDay
26%20%31%14%5%1
240
November1st to 15thDay
28%14%30%16%8%1
235
16th to endDay
25%16%32%17%6%
240
December1st to 15thDay
29%22%31%15%1
240
16th to endDay
20%26%34%15%2
103
January1st to 15thNight
22%16%36%19%3
750
16th to endNight
20%16%38%18%4
775
February1st to 15thNight
24%9%41%18%4
704
16th to endNight
26%13%32%21%41
631
March1st to 15thNight
24%12%34%24%3
720
16th to endNight
26%14%29%22%7%
768
April1st to 15thNight
27%9%32%24%5%
548
16th to endNight
29%7%32%23%7%
540
May1st to 15thNight
29%8%29%22%9%1
540
16th to endNight
23%6%35%27%6%
561
June1st to 15thNight
30%427%31%6%
413
16th to endNight
21%431%32%8%1
360
July1st to 15thNight
16%132%36%12%
340
16th to endNight
19%427%37%10%
536
August1st to 15thNight
19%225%35%15%1
539
16th to endNight
17%428%36%11%1
573
September1st to 15thNight
21%6%33%29%7%
540
16th to endNight
16%9%32%31%9%
663
October1st to 15thNight
20%10%35%23%10%
660
16th to endNight
31%18%28%17%3
704
November1st to 15thNight
30%12%32%17%6%1
730
16th to endNight
25%19%28%21%5%
750
December1st to 15thNight
28%22%31%13%3
750
16th to endNight
33%19%29%13%3
800
Page generated at 2017-09-19 08:32:34. Version ac04

Copyright 2017 A. Danko


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