Shediac River Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Shediac River Observatory clear sky chart from 2005-11-05 to 2017-09-22.

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
24%
14886
13%
46764
5%
14841
33%
14841
16%
33167

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
14%
750
13%
2685
2%
746
27%
746
11%
1884
January16th to endNight
20%
775
17%
2551
4%
775
34%
775
17%
1699
February1st to 15thNight
18%
704
12%
2286
4%
701
29%
701
15%
1639
February16th to endNight
19%
631
11%
2045
3%
631
29%
631
12%
1528
March1st to 15thNight
18%
719
15%
1992
5%
719
27%
719
17%
1496
March16th to endNight
20%
768
16%
2112
6%
768
29%
768
16%
1571
April1st to 15thNight
22%
554
12%
1781
7%
554
29%
554
14%
1329
April16th to endNight
25%
540
16%
1620
8%
540
33%
540
19%
1143
May1st to 15thNight
28%
540
10%
1513
5%
540
32%
540
16%
1138
May16th to endNight
27%
561
10%
1496
3%
560
33%
560
20%
1115
June1st to 15thNight
33%
393
7%
1293
5%
393
35%
393
14%
959
June16th to endNight
34%
360
7%
1260
4%
360
38%
360
14%
901
July1st to 15thNight
40%
340
11%
1190
9%
340
45%
340
21%
760
July16th to endNight
37%
518
9%
1403
6%
485
39%
485
19%
1019
August1st to 15thNight
41%
539
9%
1608
7%
535
43%
535
18%
1156
August16th to endNight
41%
573
15%
1755
8%
573
46%
573
25%
1135
September1st to 15thNight
33%
543
16%
1803
10%
543
42%
543
24%
1134
September16th to endNight
37%
685
22%
1914
13%
685
45%
685
29%
1204
October1st to 15thNight
27%
660
19%
1980
8%
660
37%
660
22%
1305
October16th to endNight
19%
704
14%
2129
5%
704
28%
704
14%
1537
November1st to 15thNight
21%
729
13%
2446
6%
729
30%
729
15%
1739
November16th to endNight
20%
750
12%
2520
5%
750
28%
750
12%
1809
December1st to 15thNight
12%
750
12%
2520
1%
750
24%
750
11%
1825
December16th to endNight
11%
800
10%
2862
1%
800
23%
800
8%
2142

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
20%9%36%5%34446%31%
48117
Night
19%9%36%5%34446%33%
46928
TransparencyDay
52%5%11%19%9%
47799
Night
52%412%20%9%
46764
SeeingDay
23%12%30%24%8%1
7194
Night
24%12%32%23%6%
14887

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%47%6%23435%31%
1253
16th to endDay
14%10%47%6%33445%35%
1668
February1st to 15thDay
16%9%48%5%35%446%31%
1575
16th to endDay
16%13%6%8%434445%27%
1425
March1st to 15thDay
17%12%6%9%5%23335%28%
1957
16th to endDay
16%13%5%7%5%2334432%
2112
April1st to 15thDay
19%11%46%6%44446%26%
2165
16th to endDay
24%9%25%424346%32%
2340
May1st to 15thDay
25%8%36%5%24435%29%
2437
16th to endDay
24%9%36%5%23446%28%
2618
June1st to 15thDay
29%8%25%6%24445%26%
2676
16th to endDay
23%7%36%5%35%45%7%27%
2700
July1st to 15thDay
15%5%35%5%35%5%6%9%35%
2700
16th to endDay
18%5%36%6%36%5%6%8%27%
2652
August1st to 15thDay
18%7%345%36%45%7%33%
2340
16th to endDay
15%425%5%345%5%7%40%
2447
September1st to 15thDay
18%5%25%5%3435%6%38%
2154
16th to endDay
17%5%24324335%47%
1857
October1st to 15thDay
20%7%24423346%40%
1650
16th to endDay
23%7%35%5%35%435%30%
1741
November1st to 15thDay
23%10%26%333435%31%
1411
16th to endDay
15%13%36%6%346%46%27%
1440
December1st to 15thDay
24%11%46%5%32345%28%
1440
16th to endDay
23%15%6%5%422235%27%
1359
January1st to 15thNight
17%11%46%6%33345%32%
2685
16th to endNight
15%10%46%5%24345%36%
2551
February1st to 15thNight
16%12%36%5%3445%6%29%
2285
16th to endNight
17%14%5%7%6%35%445%26%
2045
March1st to 15thNight
18%12%38%5%24335%30%
1980
16th to endNight
19%12%5%6%42433333%
2112
April1st to 15thNight
22%11%27%5%34445%27%
1781
16th to endNight
23%10%35%323235%35%
1620
May1st to 15thNight
24%9%36%42445%6%28%
1513
16th to endNight
20%7%25%5%35%5%46%31%
1494
June1st to 15thNight
26%7%35%435%5%46%27%
1293
16th to endNight
22%6%35%5%35%46%7%30%
1260
July1st to 15thNight
13%6%35%426%6%7%9%35%
1260
16th to endNight
18%7%37%5%45%45%7%31%
1500
August1st to 15thNight
17%7%46%5%36%45%5%33%
1620
16th to endNight
15%426%5%345%5%7%40%
1755
September1st to 15thNight
18%5%23424347%42%
1803
16th to endNight
14%42442335%5%49%
1914
October1st to 15thNight
18%6%25%424336%41%
1980
16th to endNight
25%7%35%5%23335%33%
2129
November1st to 15thNight
22%9%25%43445%5%31%
2446
16th to endNight
20%9%45%5%34435%32%
2520
December1st to 15thNight
23%10%36%4235%3431%
2520
16th to endNight
25%13%5%4323335%26%
2862

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
55%5%12%14%9%1
1254
16th to endDay
50%5%9%18%15%
1668
February1st to 15thDay
54%412%19%8%1
1578
16th to endDay
57%410%17%8%1
1425
March1st to 15thDay
58%38%19%8%1
1968
16th to endDay
55%39%19%9%2
2112
April1st to 15thDay
57%5%7%14%11%2
2165
16th to endDay
53%49%17%12%2
2340
May1st to 15thDay
57%47%19%10%
2437
16th to endDay
56%6%10%19%6%
2622
June1st to 15thDay
59%411%16%7%
2676
16th to endDay
55%6%12%18%6%
2700
July1st to 15thDay
42%7%16%23%10%
2541
16th to endDay
51%8%15%18%6%
2487
August1st to 15thDay
48%7%11%24%7%
2327
16th to endDay
41%7%17%25%8%
2447
September1st to 15thDay
44%5%14%23%11%
2154
16th to endDay
40%311%28%15%1
1857
October1st to 15thDay
45%411%28%9%
1650
16th to endDay
55%410%19%8%
1741
November1st to 15thDay
54%415%15%9%
1411
16th to endDay
56%6%14%15%6%
1440
December1st to 15thDay
59%6%15%15%4
1440
16th to endDay
61%213%13%8%
1359
January1st to 15thNight
53%412%18%9%1
2685
16th to endNight
48%312%23%10%
2551
February1st to 15thNight
54%411%19%10%
2286
16th to endNight
59%310%15%9%1
2045
March1st to 15thNight
56%48%19%9%1
1992
16th to endNight
56%27%19%11%1
2112
April1st to 15thNight
58%39%14%11%2
1781
16th to endNight
52%210%17%15%1
1620
May1st to 15thNight
57%410%18%8%1
1513
16th to endNight
51%7%13%19%7%
1496
June1st to 15thNight
56%6%12%16%6%
1293
16th to endNight
53%6%12%18%7%
1260
July1st to 15thNight
40%9%17%24%8%
1190
16th to endNight
51%6%15%17%8%
1403
August1st to 15thNight
52%6%14%20%7%
1608
16th to endNight
41%6%18%25%7%
1755
September1st to 15thNight
41%412%28%12%
1803
16th to endNight
36%5%14%29%12%
1914
October1st to 15thNight
44%412%28%9%
1980
16th to endNight
54%410%22%8%
2129
November1st to 15thNight
53%415%17%7%
2446
16th to endNight
54%5%13%18%7%
2520
December1st to 15thNight
56%415%19%4
2520
16th to endNight
61%310%16%7%
2862

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%23%45%10%
60
16th to endDay
16%15%41%22%3
238
February1st to 15thDay
22%13%35%21%7%
236
16th to endDay
22%17%31%21%6%
213
March1st to 15thDay
21%21%30%21%21
270
16th to endDay
25%16%32%18%42
288
April1st to 15thDay
24%17%33%18%5%
270
16th to endDay
22%17%32%19%6%1
270
May1st to 15thDay
31%10%26%20%8%1
393
16th to endDay
27%11%31%24%5%
519
June1st to 15thDay
34%10%26%21%6%
495
16th to endDay
25%7%27%29%8%1
495
July1st to 15thDay
18%5%31%32%11%1
475
16th to endDay
19%325%37%12%
480
August1st to 15thDay
20%5%25%33%12%2
313
16th to endDay
15%8%27%30%15%2
332
September1st to 15thDay
18%8%33%31%8%
315
16th to endDay
19%9%27%33%9%1
273
October1st to 15thDay
23%12%23%21%16%2
225
16th to endDay
26%20%30%14%7%1
240
November1st to 15thDay
28%16%29%14%8%2
235
16th to endDay
23%16%36%16%6%
240
December1st to 15thDay
27%22%32%13%2
240
16th to endDay
26%27%32%11%1
79
January1st to 15thNight
21%20%35%18%4
750
16th to endNight
20%17%36%19%5%
775
February1st to 15thNight
24%10%42%19%3
704
16th to endNight
26%15%29%22%31
631
March1st to 15thNight
24%14%35%22%3
720
16th to endNight
25%13%31%21%7%
768
April1st to 15thNight
27%12%29%22%7%
554
16th to endNight
27%10%30%23%7%
540
May1st to 15thNight
30%9%27%22%9%1
540
16th to endNight
23%7%36%26%6%
561
June1st to 15thNight
27%6%25%33%6%
393
16th to endNight
22%433%29%9%
360
July1st to 15thNight
15%235%32%13%
340
16th to endNight
20%5%28%35%9%
518
August1st to 15thNight
20%226%33%15%1
539
16th to endNight
16%430%35%11%1
573
September1st to 15thNight
20%6%35%30%6%
543
16th to endNight
15%9%32%31%9%
685
October1st to 15thNight
20%10%36%22%10%
660
16th to endNight
29%18%28%18%4
704
November1st to 15thNight
26%14%33%17%7%
729
16th to endNight
23%19%29%20%5%
750
December1st to 15thNight
29%20%33%14%3
750
16th to endNight
32%20%27%14%31
800
Page generated at 2017-09-23 07:43:43. Version ac04

Copyright 2017 A. Danko


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