Acadia University
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Acadia University clear sky chart from 2005-11-06 to 2024-11-04.

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 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	18% 12% 4 9% 6% 5% 4 3 5% 6% 28%	102224
	Night	18% 13% 4 10% 6% 5% 4 3 5% 6% 27%	96809
Transparency	Day	55% 7% 12% 18% 9% 1	105818
	Night	56% 7% 11% 17% 8% 1	101304
Seeing	Day	26% 17% 30% 19% 7% 1	17309
	Night	26% 16% 29% 22% 6%	24588

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	15% 18% 6% 14% 7% 7% 4 3 3 4 20%	2490
	11th to 20th	Day	14% 14% 7% 22% 8% 6% 5% 2 3 4 13%	2637
	21st to end	Day	16% 14% 8% 14% 8% 7% 4 3 4 6% 17%	3124
February	1st to 10th	Day	17% 15% 6% 13% 9% 7% 4 3 4 4 16%	1710
	11th to 20th	Day	16% 16% 5% 13% 10% 6% 4 4 3 4 18%	1663
	21st to end	Day	10% 13% 7% 10% 8% 6% 4 2 4 7% 28%	1427
March	1st to 10th	Day	22% 18% 4 9% 6% 6% 3 2 3 4 22%	3430
	11th to 20th	Day	12% 20% 6% 12% 7% 6% 4 3 4 5% 22%	3480
	21st to end	Day	23% 19% 5% 12% 5% 4 3 3 3 3 21%	3816
April	1st to 10th	Day	21% 15% 4 9% 5% 4 4 3 5% 5% 25%	2256
	11th to 20th	Day	18% 14% 3 6% 4 3 4 3 4 8% 33%	2350
	21st to end	Day	21% 12% 3 8% 4 4 4 3 5% 7% 29%	2470
May	1st to 10th	Day	24% 16% 3 7% 4 3 4 4 5% 6% 23%	4188
	11th to 20th	Day	19% 10% 2 8% 5% 4 5% 3 5% 6% 33%	4398
	21st to end	Day	14% 9% 3 7% 5% 5% 5% 4 7% 10% 32%	4836
June	1st to 10th	Day	24% 9% 3 7% 6% 4 5% 4 5% 7% 25%	2660
	11th to 20th	Day	21% 9% 3 6% 4 5% 4 3 7% 7% 32%	2850
	21st to end	Day	23% 10% 4 7% 5% 4 4 4 5% 6% 27%	2850
July	1st to 10th	Day	19% 9% 3 7% 4 4 5% 4 6% 8% 31%	4760
	11th to 20th	Day	15% 7% 3 7% 5% 4 5% 4 7% 8% 33%	4454
	21st to end	Day	13% 8% 3 8% 5% 5% 5% 4 7% 9% 32%	4640
August	1st to 10th	Day	19% 10% 3 9% 5% 5% 5% 4 5% 6% 28%	4105
	11th to 20th	Day	13% 7% 3 8% 5% 5% 5% 4 6% 7% 36%	4045
	21st to end	Day	12% 6% 2 5% 4 4 4 4 6% 8% 46%	4382
September	1st to 10th	Day	16% 7% 2 5% 4 4 3 3 5% 7% 43%	2280
	11th to 20th	Day	17% 7% 2 6% 4 3 3 3 4 6% 45%	2185
	21st to end	Day	17% 6% 3 6% 4 3 4 3 5% 7% 42%	2043
October	1st to 10th	Day	17% 7% 3 6% 4 4 4 4 5% 8% 38%	1900
	11th to 20th	Day	18% 10% 3 7% 4 4 4 4 6% 7% 33%	1900
	21st to end	Day	18% 14% 4 8% 5% 4 4 3 5% 5% 30%	2090
November	1st to 10th	Day	21% 14% 3 9% 5% 5% 4 2 3 6% 28%	1556
	11th to 20th	Day	17% 18% 5% 9% 6% 5% 4 4 4 6% 23%	1520
	21st to end	Day	18% 16% 5% 11% 7% 6% 5% 3 5% 5% 20%	1520
December	1st to 10th	Day	22% 20% 6% 13% 6% 5% 4 3 3 4 16%	1520
	11th to 20th	Day	23% 18% 7% 13% 9% 5% 3 3 3 3 12%	1906
	21st to end	Day	21% 16% 11% 14% 7% 4 4 2 4 4 14%	2783
January	1st to 10th	Night	14% 14% 7% 17% 8% 6% 5% 3 5% 5% 17%	4429
	11th to 20th	Night	15% 16% 7% 18% 8% 6% 5% 3 4 4 14%	4316
	21st to end	Night	16% 13% 5% 16% 10% 6% 4 4 5% 6% 15%	4532
February	1st to 10th	Night	17% 16% 5% 14% 10% 5% 5% 4 5% 4 16%	2470
	11th to 20th	Night	16% 14% 6% 12% 10% 7% 5% 3 5% 5% 18%	2403
	21st to end	Night	11% 16% 5% 11% 7% 6% 5% 3 5% 5% 27%	2022
March	1st to 10th	Night	22% 15% 4 13% 8% 5% 3 3 2 3 22%	3410
	11th to 20th	Night	16% 21% 7% 9% 5% 5% 4 4 5% 5% 19%	3479
	21st to end	Night	23% 14% 6% 12% 6% 4 3 2 3 3 23%	3816
April	1st to 10th	Night	21% 15% 5% 6% 6% 5% 4 3 4 4 27%	1923
	11th to 20th	Night	21% 13% 4 7% 3 4 4 2 4 6% 32%	1778
	21st to end	Night	21% 13% 3 7% 4 5% 4 4 4 5% 30%	1710
May	1st to 10th	Night	22% 18% 2 7% 5% 4 4 3 5% 6% 24%	2755
	11th to 20th	Night	19% 10% 3 7% 4 5% 4 4 5% 7% 31%	2506
	21st to end	Night	14% 10% 4 9% 5% 5% 5% 4 6% 8% 31%	2749
June	1st to 10th	Night	24% 9% 2 7% 5% 4 4 4 5% 9% 27%	1520
	11th to 20th	Night	19% 8% 3 7% 4 5% 4 3 5% 6% 35%	1344
	21st to end	Night	22% 9% 4 6% 5% 5% 5% 3 6% 7% 28%	1330
July	1st to 10th	Night	16% 10% 4 9% 5% 5% 5% 4 7% 8% 28%	2210
	11th to 20th	Night	16% 7% 2 6% 4 5% 5% 5% 7% 10% 33%	2466
	21st to end	Night	11% 7% 3 6% 5% 4 5% 4 6% 8% 40%	2915
August	1st to 10th	Night	19% 9% 2 7% 4 4 4 4 6% 7% 33%	2825
	11th to 20th	Night	12% 7% 3 8% 6% 5% 4 4 7% 8% 37%	2782
	21st to end	Night	14% 5% 2 5% 3 3 4 3 5% 7% 49%	3273
September	1st to 10th	Night	12% 6% 3 6% 4 4 4 4 5% 8% 44%	1900
	11th to 20th	Night	16% 7% 3 6% 3 3 3 3 6% 7% 44%	1992
	21st to end	Night	17% 7% 3 6% 4 3 5% 4 5% 7% 38%	2136
October	1st to 10th	Night	17% 7% 2 5% 3 4 4 3 6% 7% 40%	2280
	11th to 20th	Night	18% 8% 3 7% 4 4 5% 3 5% 8% 36%	2280
	21st to end	Night	23% 11% 3 7% 4 4 4 3 4 6% 31%	2508
November	1st to 10th	Night	20% 12% 3 8% 5% 5% 4 3 5% 5% 30%	2593
	11th to 20th	Night	17% 17% 4 11% 7% 5% 5% 4 5% 5% 22%	2660
	21st to end	Night	20% 16% 5% 10% 6% 4 4 3 4 5% 22%	2660
December	1st to 10th	Night	21% 18% 5% 13% 7% 5% 4 3 4 5% 15%	2660
	11th to 20th	Night	20% 21% 6% 13% 7% 5% 4 3 3 3 15%	3293
	21st to end	Night	24% 15% 7% 12% 5% 4 3 3 3 3 20%	4884

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	66% 5% 18% 9% 2	2491
	11th to 20th	Day	73% 5% 7% 12% 2	2637
	21st to end	Day	66% 7% 10% 10% 7%	3124
February	1st to 10th	Day	70% 5% 8% 9% 6% 1	1710
	11th to 20th	Day	69% 7% 9% 11% 4	1671
	21st to end	Day	56% 5% 10% 18% 9% 1	1427
March	1st to 10th	Day	66% 4 8% 15% 5% 1	3434
	11th to 20th	Day	62% 6% 11% 13% 7% 1	3480
	21st to end	Day	70% 3 6% 12% 8% 1	3816
April	1st to 10th	Day	61% 5% 8% 13% 11% 3	2256
	11th to 20th	Day	52% 4 9% 21% 13% 1	2350
	21st to end	Day	55% 4 10% 18% 11% 2	2470
May	1st to 10th	Day	60% 7% 9% 16% 7% 1	4202
	11th to 20th	Day	49% 9% 13% 20% 8% 1	4402
	21st to end	Day	45% 9% 17% 18% 10%	4836
June	1st to 10th	Day	57% 6% 11% 18% 7%	2660
	11th to 20th	Day	50% 7% 13% 19% 10% 1	2850
	21st to end	Day	57% 7% 11% 15% 10% 1	2850
July	1st to 10th	Day	50% 7% 13% 18% 11% 1	4685
	11th to 20th	Day	46% 10% 15% 21% 8%	4377
	21st to end	Day	47% 9% 16% 20% 8%	4492
August	1st to 10th	Day	55% 7% 11% 19% 8%	4092
	11th to 20th	Day	45% 8% 14% 22% 11%	4084
	21st to end	Day	34% 8% 15% 25% 17% 1	4382
September	1st to 10th	Day	41% 5% 13% 25% 14% 2	2280
	11th to 20th	Day	42% 4 12% 24% 16% 1	2185
	21st to end	Day	42% 5% 10% 28% 15% 1	2043
October	1st to 10th	Day	43% 10% 13% 23% 11%	3160
	11th to 20th	Day	42% 7% 11% 26% 14%	3140
	21st to end	Day	46% 5% 14% 22% 13%	3428
November	1st to 10th	Day	59% 6% 9% 17% 8% 1	1556
	11th to 20th	Day	61% 7% 13% 13% 5% 1	1520
	21st to end	Day	66% 7% 12% 12% 4	1520
December	1st to 10th	Day	73% 6% 7% 10% 4	1520
	11th to 20th	Day	75% 6% 7% 8% 3 1	1905
	21st to end	Day	73% 6% 12% 7% 3	2783
January	1st to 10th	Night	65% 7% 13% 12% 2	4429
	11th to 20th	Night	71% 7% 9% 8% 5%	4316
	21st to end	Night	67% 7% 12% 11% 3	4532
February	1st to 10th	Night	71% 6% 8% 9% 6%	2470
	11th to 20th	Night	67% 6% 10% 12% 5% 1	2406
	21st to end	Night	58% 5% 10% 18% 8% 1	2022
March	1st to 10th	Night	68% 4 6% 14% 7% 1	3419
	11th to 20th	Night	65% 6% 8% 13% 7% 1	3480
	21st to end	Night	67% 3 7% 14% 8% 1	3816
April	1st to 10th	Night	60% 5% 8% 13% 11% 3	1923
	11th to 20th	Night	54% 5% 7% 20% 13% 1	1778
	21st to end	Night	56% 5% 10% 14% 12% 2	1710
May	1st to 10th	Night	60% 7% 13% 13% 6% 1	2761
	11th to 20th	Night	50% 9% 12% 22% 7% 1	2507
	21st to end	Night	50% 9% 16% 19% 5% 1	2750
June	1st to 10th	Night	53% 9% 11% 20% 6%	1520
	11th to 20th	Night	49% 6% 11% 22% 10% 1	1344
	21st to end	Night	55% 10% 11% 16% 8% 2	1330
July	1st to 10th	Night	52% 9% 14% 15% 9% 1	2175
	11th to 20th	Night	44% 10% 20% 17% 9%	2420
	21st to end	Night	39% 9% 16% 24% 12%	2823
August	1st to 10th	Night	50% 9% 14% 22% 6%	2813
	11th to 20th	Night	43% 10% 16% 23% 8%	2809
	21st to end	Night	33% 7% 17% 26% 16% 1	3272
September	1st to 10th	Night	38% 8% 11% 28% 14% 1	1900
	11th to 20th	Night	40% 5% 12% 29% 14% 1	1992
	21st to end	Night	44% 7% 10% 25% 13% 1	2136
October	1st to 10th	Night	47% 6% 12% 23% 11%	3800
	11th to 20th	Night	38% 7% 13% 25% 16%	3779
	21st to end	Night	44% 5% 12% 23% 15%	4120
November	1st to 10th	Night	54% 6% 12% 19% 9% 1	2593
	11th to 20th	Night	62% 7% 10% 14% 6%	2660
	21st to end	Night	63% 7% 13% 13% 4	2660
December	1st to 10th	Night	71% 5% 10% 11% 3	2660
	11th to 20th	Night	75% 5% 7% 10% 4	3295
	21st to end	Night	69% 5% 10% 13% 3	4884

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	30% 25% 31% 13% 2	334
	11th to 20th	Day	31% 25% 29% 11% 3	370
	21st to end	Day	21% 26% 35% 15% 2	407
February	1st to 10th	Day	30% 23% 31% 11% 4 1	370
	11th to 20th	Day	31% 30% 23% 14% 1	366
	21st to end	Day	23% 21% 38% 16% 3	312
March	1st to 10th	Day	28% 24% 32% 12% 3	460
	11th to 20th	Day	25% 25% 34% 12% 4	460
	21st to end	Day	32% 25% 27% 11% 5%	506
April	1st to 10th	Day	38% 22% 27% 11% 2	460
	11th to 20th	Day	24% 26% 32% 14% 3 1	452
	21st to end	Day	27% 20% 30% 15% 9%	460
May	1st to 10th	Day	32% 19% 28% 14% 5% 2	506
	11th to 20th	Day	24% 17% 25% 25% 7% 1	674
	21st to end	Day	26% 14% 33% 20% 7% 1	735
June	1st to 10th	Day	30% 12% 27% 22% 8% 1	680
	11th to 20th	Day	25% 12% 31% 24% 7% 1	680
	21st to end	Day	29% 10% 27% 23% 8% 2	680
July	1st to 10th	Day	21% 7% 33% 28% 10% 1	670
	11th to 20th	Day	19% 7% 32% 27% 13% 2	668
	21st to end	Day	22% 7% 30% 28% 11% 1	640
August	1st to 10th	Day	15% 8% 31% 33% 10% 2	486
	11th to 20th	Day	20% 9% 29% 25% 12% 4	479
	21st to end	Day	15% 13% 29% 23% 16% 4	539
September	1st to 10th	Day	19% 10% 34% 25% 10% 1	490
	11th to 20th	Day	22% 14% 26% 25% 10% 3	490
	21st to end	Day	20% 15% 31% 22% 11% 2	465
October	1st to 10th	Day	22% 13% 30% 22% 9% 3	390
	11th to 20th	Day	25% 18% 28% 19% 8% 2	390
	21st to end	Day	26% 22% 29% 18% 4 1	429
November	1st to 10th	Day	30% 17% 30% 18% 4 1	374
	11th to 20th	Day	36% 21% 24% 13% 6% 1	370
	21st to end	Day	32% 22% 31% 13% 2 1	370
December	1st to 10th	Day	35% 22% 29% 12% 2 1	370
	11th to 20th	Day	39% 25% 26% 9% 1	370
	21st to end	Day	34% 24% 28% 11% 3 1	407
January	1st to 10th	Night	30% 23% 31% 15% 2	850
	11th to 20th	Night	30% 22% 29% 15% 3	816
	21st to end	Night	26% 23% 32% 15% 4	836
February	1st to 10th	Night	31% 23% 29% 15% 2	760
	11th to 20th	Night	31% 24% 29% 13% 2	743
	21st to end	Night	24% 22% 32% 18% 4	628
March	1st to 10th	Night	28% 20% 32% 17% 3	760
	11th to 20th	Night	24% 19% 31% 21% 5%	760
	21st to end	Night	28% 19% 30% 17% 6%	836
April	1st to 10th	Night	32% 18% 30% 17% 3	593
	11th to 20th	Night	27% 17% 34% 17% 5%	564
	21st to end	Night	29% 17% 30% 18% 6% 1	570
May	1st to 10th	Night	31% 12% 29% 21% 6%	570
	11th to 20th	Night	26% 10% 29% 27% 7%	562
	21st to end	Night	21% 11% 37% 26% 5%	616
June	1st to 10th	Night	28% 10% 30% 26% 5%	570
	11th to 20th	Night	23% 8% 27% 34% 7% 1	394
	21st to end	Night	24% 7% 27% 31% 10% 1	380
July	1st to 10th	Night	19% 6% 29% 38% 9%	370
	11th to 20th	Night	16% 6% 29% 37% 13%	516
	21st to end	Night	19% 5% 26% 41% 9%	623
August	1st to 10th	Night	16% 5% 26% 40% 13% 1	568
	11th to 20th	Night	17% 6% 27% 33% 15% 1	562
	21st to end	Night	17% 7% 24% 34% 18% 1	627
September	1st to 10th	Night	14% 9% 30% 34% 12% 1	570
	11th to 20th	Night	19% 10% 26% 32% 12% 1	662
	21st to end	Night	22% 11% 30% 25% 10% 2	760
October	1st to 10th	Night	23% 11% 31% 24% 10% 1	760
	11th to 20th	Night	23% 16% 33% 20% 8% 1	760
	21st to end	Night	32% 19% 25% 19% 5%	836
November	1st to 10th	Night	28% 19% 28% 20% 5%	831
	11th to 20th	Night	30% 21% 26% 18% 4	850
	21st to end	Night	33% 19% 28% 18% 2	850
December	1st to 10th	Night	34% 21% 28% 14% 3	850
	11th to 20th	Night	34% 25% 27% 11% 2	850
	21st to end	Night	32% 22% 27% 16% 3 1	935

Page generated at 2024-11-01 23:47:29. Version ac07

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