Fredericton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fredericton clear sky chart from 2005-11-06 to 2024-01-31.

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 Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(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

By Month

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 Forecast	Data Points
Cloud Cover	Day	20% 8% 3 6% 5% 3 5% 4 5% 6% 34%	74791
	Night	20% 9% 3 6% 5% 3 4 4 5% 6% 34%	75344
Transparency	Day	51% 5% 11% 21% 11% 1	74492
	Night	51% 5% 11% 21% 11% 1	75178
Seeing	Day	27% 16% 30% 18% 7% 1	15197
	Night	25% 14% 31% 23% 6%	23267

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
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	17% 13% 5% 8% 6% 3 4 4 6% 6% 29%	1327
	11th to 20th	Day	20% 14% 5% 8% 7% 3 3 4 3 4 30%	1491
	21st to end	Day	14% 9% 4 5% 6% 4 5% 4 6% 6% 38%	1779
February	1st to 10th	Day	16% 10% 4 7% 7% 4 6% 5% 4 6% 31%	1620
	11th to 20th	Day	17% 12% 4 7% 6% 4 5% 5% 5% 6% 29%	1573
	21st to end	Day	11% 10% 5% 8% 7% 4 5% 5% 5% 6% 34%	1444
March	1st to 10th	Day	18% 13% 4 7% 6% 3 5% 4 4 5% 30%	1881
	11th to 20th	Day	17% 10% 4 7% 6% 3 5% 4 4 6% 34%	1980
	21st to end	Day	18% 12% 4 8% 6% 3 4 3 4 5% 32%	2178
April	1st to 10th	Day	22% 14% 4 7% 5% 2 5% 4 4 6% 27%	2111
	11th to 20th	Day	21% 9% 3 6% 5% 3 4 4 5% 7% 34%	2312
	21st to end	Day	27% 9% 3 5% 5% 3 3 4 4 5% 31%	2340
May	1st to 10th	Day	24% 10% 3 6% 5% 3 4 4 4 6% 30%	2340
	11th to 20th	Day	26% 6% 3 5% 5% 3 4 3 4 6% 35%	2424
	21st to end	Day	21% 6% 3 6% 6% 3 4 5% 5% 7% 34%	2822
June	1st to 10th	Day	26% 8% 3 7% 6% 3 5% 4 4 6% 27%	2700
	11th to 20th	Day	23% 6% 2 6% 5% 3 4 4 5% 7% 35%	2700
	21st to end	Day	28% 7% 3 6% 5% 3 5% 4 5% 7% 27%	2700
July	1st to 10th	Day	18% 6% 2 5% 5% 4 5% 6% 6% 9% 35%	2700
	11th to 20th	Day	18% 5% 2 5% 4 3 5% 6% 7% 10% 33%	2698
	21st to end	Day	17% 6% 3 6% 6% 3 6% 6% 7% 9% 31%	2636
August	1st to 10th	Day	19% 6% 3 6% 6% 3 5% 5% 6% 8% 34%	2327
	11th to 20th	Day	17% 7% 3 6% 6% 4 6% 5% 6% 8% 33%	2304
	21st to end	Day	16% 5% 2 5% 4 3 5% 5% 5% 8% 41%	2574
September	1st to 10th	Day	13% 5% 3 6% 4 3 5% 5% 5% 7% 45%	2145
	11th to 20th	Day	19% 6% 2 4 4 3 4 4 4 5% 46%	1980
	21st to end	Day	20% 6% 2 4 4 3 3 4 4 6% 44%	1980
October	1st to 10th	Day	19% 7% 2 5% 5% 3 4 4 5% 7% 40%	1838
	11th to 20th	Day	21% 7% 3 6% 5% 3 4 3 6% 6% 37%	1800
	21st to end	Day	22% 8% 4 7% 7% 4 4 3 5% 6% 30%	1854
November	1st to 10th	Day	22% 7% 3 6% 5% 3 4 4 4 6% 36%	1612
	11th to 20th	Day	21% 6% 2 5% 4 4 4 5% 6% 8% 35%	1520
	21st to end	Day	22% 10% 4 7% 5% 2 4 4 4 6% 32%	1520
December	1st to 10th	Day	26% 9% 3 7% 6% 2 5% 4 4 5% 29%	1482
	11th to 20th	Day	23% 12% 4 7% 7% 4 4 4 4 4 28%	1668
	21st to end	Day	22% 11% 4 6% 6% 2 3 3 3 4 35%	2431
January	1st to 10th	Night	16% 11% 5% 9% 7% 3 5% 4 6% 6% 29%	2838
	11th to 20th	Night	19% 12% 4 7% 6% 4 5% 4 5% 6% 28%	2687
	21st to end	Night	13% 10% 3 7% 5% 3 4 4 6% 7% 35%	2802
February	1st to 10th	Night	16% 12% 4 6% 4 3 5% 5% 6% 7% 33%	2340
	11th to 20th	Night	18% 12% 4 6% 7% 4 5% 5% 6% 7% 28%	2273
	21st to end	Night	15% 12% 3 7% 6% 3 5% 5% 5% 5% 33%	1811
March	1st to 10th	Night	16% 13% 4 7% 6% 3 4 3 5% 5% 34%	2065
	11th to 20th	Night	18% 10% 3 6% 6% 3 5% 5% 5% 6% 31%	1979
	21st to end	Night	18% 10% 5% 6% 6% 3 4 3 4 5% 35%	2178
April	1st to 10th	Night	26% 11% 3 6% 5% 3 4 4 4 5% 30%	1845
	11th to 20th	Night	23% 7% 3 5% 5% 2 5% 4 5% 5% 36%	1598
	21st to end	Night	28% 9% 3 5% 4 3 4 3 4 7% 31%	1620
May	1st to 10th	Night	23% 7% 3 6% 5% 3 4 5% 5% 8% 31%	1620
	11th to 20th	Night	27% 7% 2 5% 5% 4 5% 3 3 5% 33%	1470
	21st to end	Night	18% 8% 4 6% 6% 4 5% 5% 4 7% 34%	1466
June	1st to 10th	Night	27% 7% 3 5% 5% 3 5% 5% 5% 6% 29%	1260
	11th to 20th	Night	21% 5% 4 4 6% 3 5% 5% 5% 8% 35%	1260
	21st to end	Night	29% 4 2 5% 5% 2 3 4 5% 6% 34%	1260
July	1st to 10th	Night	18% 6% 3 5% 5% 3 4 6% 6% 8% 37%	1260
	11th to 20th	Night	17% 5% 3 5% 5% 4 4 6% 6% 9% 36%	1260
	21st to end	Night	20% 7% 3 6% 5% 4 5% 6% 6% 8% 32%	1664
August	1st to 10th	Night	16% 5% 3 5% 5% 3 5% 5% 6% 8% 41%	1612
	11th to 20th	Night	18% 7% 3 6% 5% 4 5% 5% 6% 8% 36%	1596
	21st to end	Night	14% 6% 2 4 5% 2 3 5% 6% 7% 46%	1782
September	1st to 10th	Night	16% 6% 2 5% 4 3 3 4 6% 7% 45%	1812
	11th to 20th	Night	17% 5% 3 4 4 3 3 3 4 6% 47%	1980
	21st to end	Night	21% 4 2 4 4 2 3 4 4 5% 47%	1980
October	1st to 10th	Night	19% 6% 2 5% 4 2 3 3 6% 7% 42%	2121
	11th to 20th	Night	21% 5% 3 5% 6% 3 5% 4 5% 7% 37%	2160
	21st to end	Night	24% 8% 3 6% 6% 3 4 4 4 5% 34%	2500
November	1st to 10th	Night	22% 7% 3 6% 5% 3 4 4 4 6% 37%	2464
	11th to 20th	Night	21% 7% 3 5% 5% 3 4 4 5% 7% 36%	2660
	21st to end	Night	22% 9% 3 6% 5% 3 5% 5% 5% 6% 31%	2660
December	1st to 10th	Night	27% 10% 4 7% 5% 2 4 4 4 5% 29%	2694
	11th to 20th	Night	26% 10% 3 6% 5% 3 5% 4 4 5% 28%	3531
	21st to end	Night	22% 12% 4 6% 5% 3 4 3 4 4 33%	5236

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	56% 5% 13% 15% 9% 1	1328
	11th to 20th	Day	60% 5% 8% 17% 9% 1	1491
	21st to end	Day	46% 5% 11% 22% 14% 2	1779
February	1st to 10th	Day	54% 5% 11% 19% 9% 2	1620
	11th to 20th	Day	56% 6% 10% 17% 10% 1	1581
	21st to end	Day	49% 5% 11% 23% 11% 2	1444
March	1st to 10th	Day	57% 4 9% 17% 10% 2	1885
	11th to 20th	Day	53% 4 11% 18% 12% 3	1980
	21st to end	Day	55% 4 7% 19% 10% 4	2178
April	1st to 10th	Day	59% 3 9% 14% 12% 2	2111
	11th to 20th	Day	50% 4 10% 22% 13% 1	2312
	21st to end	Day	56% 5% 8% 16% 12% 5%	2340
May	1st to 10th	Day	56% 4 7% 19% 10% 2	2340
	11th to 20th	Day	52% 5% 9% 20% 12% 2	2428
	21st to end	Day	49% 7% 12% 22% 9% 1	2822
June	1st to 10th	Day	57% 6% 9% 17% 10% 1	2700
	11th to 20th	Day	50% 5% 12% 19% 13% 2	2700
	21st to end	Day	57% 6% 11% 16% 9% 1	2700
July	1st to 10th	Day	44% 8% 16% 21% 10% 1	2625
	11th to 20th	Day	43% 9% 15% 23% 10% 1	2617
	21st to end	Day	48% 8% 15% 21% 9%	2489
August	1st to 10th	Day	47% 7% 15% 24% 7%	2314
	11th to 20th	Day	48% 6% 13% 24% 8%	2304
	21st to end	Day	41% 6% 15% 26% 12%	2574
September	1st to 10th	Day	38% 6% 15% 26% 14%	2145
	11th to 20th	Day	41% 5% 10% 28% 16% 2	1980
	21st to end	Day	42% 5% 9% 26% 16% 1	1980
October	1st to 10th	Day	44% 5% 12% 27% 12%	1838
	11th to 20th	Day	47% 5% 15% 25% 8%	1800
	21st to end	Day	55% 5% 10% 19% 11%	1854
November	1st to 10th	Day	50% 5% 12% 21% 12% 1	1612
	11th to 20th	Day	47% 5% 15% 18% 13% 1	1520
	21st to end	Day	55% 5% 14% 20% 6%	1520
December	1st to 10th	Day	58% 4 11% 19% 7% 1	1482
	11th to 20th	Day	61% 4 9% 17% 9% 1	1668
	21st to end	Day	54% 4 11% 18% 10% 3	2431
January	1st to 10th	Night	56% 5% 11% 18% 10% 1	2838
	11th to 20th	Night	57% 6% 10% 17% 8% 1	2687
	21st to end	Night	48% 5% 11% 23% 12% 2	2802
February	1st to 10th	Night	51% 5% 12% 19% 12% 1	2340
	11th to 20th	Night	55% 5% 10% 17% 11% 2	2276
	21st to end	Night	53% 4 9% 19% 11% 2	1811
March	1st to 10th	Night	53% 5% 7% 20% 12% 2	2074
	11th to 20th	Night	52% 5% 10% 18% 14% 2	1980
	21st to end	Night	53% 4 7% 20% 13% 2	2178
April	1st to 10th	Night	57% 4 8% 15% 11% 4	1845
	11th to 20th	Night	49% 5% 9% 21% 15% 2	1598
	21st to end	Night	55% 4 9% 17% 11% 2	1620
May	1st to 10th	Night	52% 5% 10% 19% 12% 2	1620
	11th to 20th	Night	54% 5% 8% 20% 11% 1	1471
	21st to end	Night	50% 8% 12% 18% 11% 1	1467
June	1st to 10th	Night	56% 6% 9% 19% 9% 2	1260
	11th to 20th	Night	48% 6% 12% 22% 10% 2	1260
	21st to end	Night	52% 5% 13% 19% 9% 1	1260
July	1st to 10th	Night	43% 7% 18% 22% 9%	1225
	11th to 20th	Night	44% 7% 16% 23% 10%	1218
	21st to end	Night	49% 8% 13% 21% 9% 1	1571
August	1st to 10th	Night	42% 8% 17% 26% 8%	1600
	11th to 20th	Night	47% 7% 17% 23% 6%	1596
	21st to end	Night	37% 5% 17% 27% 14% 1	1782
September	1st to 10th	Night	38% 6% 15% 28% 13% 1	1812
	11th to 20th	Night	39% 5% 11% 28% 15% 1	1980
	21st to end	Night	41% 5% 11% 28% 15% 1	1980
October	1st to 10th	Night	42% 4 12% 26% 15% 1	2121
	11th to 20th	Night	47% 5% 11% 26% 10%	2160
	21st to end	Night	53% 5% 10% 20% 11%	2500
November	1st to 10th	Night	49% 5% 13% 22% 11% 1	2464
	11th to 20th	Night	49% 4 13% 21% 11% 1	2660
	21st to end	Night	53% 6% 14% 17% 9%	2660
December	1st to 10th	Night	59% 4 10% 20% 7%	2694
	11th to 20th	Night	59% 3 9% 19% 9%	3532
	21st to end	Night	56% 4 11% 19% 6% 4	5236

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
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	31% 15% 36% 16% 2	180
	11th to 20th	Day	35% 21% 32% 9% 3 1	180
	21st to end	Day	23% 19% 36% 17% 5% 1	311
February	1st to 10th	Day	29% 19% 32% 17% 3	340
	11th to 20th	Day	29% 23% 29% 16% 3 1	336
	21st to end	Day	24% 25% 29% 19% 2	330
March	1st to 10th	Day	31% 21% 32% 13% 3 1	420
	11th to 20th	Day	27% 20% 32% 15% 5% 1	420
	21st to end	Day	30% 22% 27% 13% 7% 1	462
April	1st to 10th	Day	38% 25% 23% 11% 3	420
	11th to 20th	Day	32% 20% 29% 14% 4 1	412
	21st to end	Day	33% 19% 30% 12% 5% 1	420
May	1st to 10th	Day	35% 17% 29% 15% 4	423
	11th to 20th	Day	30% 19% 27% 16% 6% 1	570
	21st to end	Day	26% 18% 34% 15% 7%	680
June	1st to 10th	Day	32% 17% 27% 17% 6% 1	630
	11th to 20th	Day	27% 15% 28% 20% 9% 1	630
	21st to end	Day	28% 11% 30% 23% 8% 1	630
July	1st to 10th	Day	24% 10% 35% 20% 10% 1	620
	11th to 20th	Day	21% 7% 33% 24% 12% 2	616
	21st to end	Day	17% 9% 37% 26% 9% 2	488
August	1st to 10th	Day	19% 8% 35% 26% 10% 2	446
	11th to 20th	Day	21% 9% 28% 28% 12% 2	439
	21st to end	Day	21% 13% 25% 27% 11% 3	495
September	1st to 10th	Day	13% 12% 34% 27% 10% 3	450
	11th to 20th	Day	24% 11% 29% 22% 10% 3	450
	21st to end	Day	21% 18% 30% 16% 11% 4	450
October	1st to 10th	Day	24% 15% 23% 22% 12% 3	378
	11th to 20th	Day	24% 19% 29% 16% 11% 3	360
	21st to end	Day	31% 18% 31% 14% 6%	396
November	1st to 10th	Day	30% 14% 30% 20% 6% 1	365
	11th to 20th	Day	33% 18% 27% 15% 6%	370
	21st to end	Day	31% 22% 28% 16% 4	370
December	1st to 10th	Day	32% 17% 30% 16% 4 1	332
	11th to 20th	Day	38% 26% 24% 10% 2	180
	21st to end	Day	31% 25% 27% 14% 2 1	198
January	1st to 10th	Night	25% 19% 32% 21% 3	850
	11th to 20th	Night	29% 17% 30% 21% 4	772
	21st to end	Night	19% 21% 34% 21% 4	835
February	1st to 10th	Night	24% 21% 31% 20% 3	720
	11th to 20th	Night	26% 21% 33% 16% 4	703
	21st to end	Night	23% 19% 32% 23% 4	592
March	1st to 10th	Night	25% 18% 35% 20% 3	720
	11th to 20th	Night	25% 15% 33% 21% 6%	720
	21st to end	Night	24% 17% 34% 21% 5%	792
April	1st to 10th	Night	33% 16% 32% 16% 3	643
	11th to 20th	Night	29% 17% 32% 17% 5%	534
	21st to end	Night	32% 14% 29% 20% 5%	540
May	1st to 10th	Night	28% 14% 30% 24% 5%	540
	11th to 20th	Night	30% 14% 31% 20% 5%	532
	21st to end	Night	20% 16% 35% 24% 4	499
June	1st to 10th	Night	31% 6% 32% 24% 7%	360
	11th to 20th	Night	21% 10% 32% 30% 6% 1	360
	21st to end	Night	32% 4 26% 32% 5% 1	360
July	1st to 10th	Night	21% 5% 37% 31% 7%	350
	11th to 20th	Night	18% 5% 29% 34% 13% 1	348
	21st to end	Night	22% 6% 31% 33% 9%	484
August	1st to 10th	Night	17% 5% 29% 36% 13%	538
	11th to 20th	Night	20% 6% 27% 33% 14%	532
	21st to end	Night	18% 7% 29% 30% 15% 1	594
September	1st to 10th	Night	19% 9% 36% 26% 11% 1	575
	11th to 20th	Night	22% 9% 24% 31% 12% 1	720
	21st to end	Night	22% 12% 28% 26% 12%	720
October	1st to 10th	Night	22% 10% 29% 28% 10% 1	720
	11th to 20th	Night	21% 13% 31% 24% 10% 1	720
	21st to end	Night	28% 17% 30% 19% 5%	792
November	1st to 10th	Night	28% 13% 29% 23% 6% 1	767
	11th to 20th	Night	28% 16% 29% 20% 6% 1	850
	21st to end	Night	27% 20% 28% 21% 5%	850
December	1st to 10th	Night	35% 14% 29% 19% 4	850
	11th to 20th	Night	30% 20% 30% 17% 3	850
	21st to end	Night	30% 20% 28% 18% 3 1	935

Page generated at 2024-01-28 06:26:33. Version ac07

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