Beaver River Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Beaver River Observatory clear sky chart from 2005-11-06 to 2024-11-08.

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	15% 12% 5% 10% 6% 5% 4 4 5% 6% 29%	101747
	Night	14% 14% 5% 12% 6% 5% 4 3 4 5% 28%	97367
Transparency	Day	54% 7% 11% 18% 10% 1	105319
	Night	56% 7% 11% 17% 9% 1	101884
Seeing	Day	19% 17% 30% 22% 10% 3	15060
	Night	20% 16% 30% 24% 9% 1	24152

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	12% 20% 12% 21% 10% 4 4 3 3 3 8%	2208
	11th to 20th	Day	8% 19% 11% 25% 12% 8% 5% 2 3 2 5%	2753
	21st to end	Day	14% 22% 10% 19% 8% 6% 4 3 3 3 9%	3124
February	1st to 10th	Day	11% 18% 9% 20% 11% 6% 4 3 4 4 11%	1710
	11th to 20th	Day	12% 14% 9% 20% 11% 6% 4 3 4 4 13%	1663
	21st to end	Day	13% 20% 6% 14% 8% 7% 4 4 4 5% 15%	1498
March	1st to 10th	Day	14% 16% 6% 13% 7% 5% 4 3 4 4 26%	3384
	11th to 20th	Day	9% 15% 13% 16% 6% 4 3 3 4 4 23%	3480
	21st to end	Day	13% 15% 7% 10% 6% 4 4 4 4 5% 28%	3815
April	1st to 10th	Day	16% 17% 5% 10% 5% 5% 4 3 4 6% 25%	2204
	11th to 20th	Day	17% 14% 4 7% 4 4 3 3 5% 5% 34%	2408
	21st to end	Day	19% 13% 4 8% 4 3 3 3 5% 6% 32%	2470
May	1st to 10th	Day	16% 11% 3 7% 4 4 4 3 5% 7% 36%	4108
	11th to 20th	Day	16% 9% 3 8% 5% 4 5% 4 5% 7% 33%	4300
	21st to end	Day	14% 8% 2 5% 4 4 4 3 5% 7% 44%	4837
June	1st to 10th	Day	17% 8% 2 7% 4 4 5% 5% 6% 8% 35%	2707
	11th to 20th	Day	12% 7% 2 5% 4 4 5% 5% 7% 9% 39%	2850
	21st to end	Day	17% 7% 2 5% 5% 4 4 4 6% 7% 37%	2850
July	1st to 10th	Day	14% 7% 3 7% 6% 6% 6% 5% 7% 8% 33%	4760
	11th to 20th	Day	13% 6% 2 6% 4 4 5% 5% 6% 8% 42%	4576
	21st to end	Day	11% 7% 3 7% 5% 4 3 4 6% 8% 42%	4466
August	1st to 10th	Day	14% 7% 2 7% 4 5% 6% 4 6% 7% 36%	4104
	11th to 20th	Day	15% 8% 3 7% 5% 5% 6% 5% 6% 8% 32%	4044
	21st to end	Day	12% 6% 3 6% 5% 4 4 4 6% 9% 41%	4448
September	1st to 10th	Day	17% 8% 2 7% 5% 4 4 4 4 6% 37%	2280
	11th to 20th	Day	15% 7% 2 6% 4 4 4 3 6% 8% 42%	2103
	21st to end	Day	17% 8% 3 8% 6% 5% 5% 4 5% 6% 33%	2090
October	1st to 10th	Day	20% 12% 3 7% 4 4 4 3 5% 7% 32%	1903
	11th to 20th	Day	22% 14% 5% 9% 6% 5% 4 3 5% 5% 21%	1900
	21st to end	Day	26% 21% 3 8% 4 5% 3 3 5% 6% 16%	2057
November	1st to 10th	Day	15% 20% 4 9% 6% 4 5% 4 3 6% 23%	1666
	11th to 20th	Day	14% 21% 6% 13% 6% 5% 5% 3 5% 7% 17%	1520
	21st to end	Day	16% 23% 8% 13% 7% 4 4 4 4 6% 12%	1520
December	1st to 10th	Day	13% 25% 12% 20% 6% 3 4 3 4 3 7%	1520
	11th to 20th	Day	15% 21% 9% 20% 7% 4 4 3 3 4 11%	1906
	21st to end	Day	20% 22% 9% 17% 6% 5% 3 2 4 3 8%	2515
January	1st to 10th	Night	12% 22% 12% 21% 11% 5% 4 3 3 3 7%	4748
	11th to 20th	Night	11% 15% 10% 26% 11% 9% 5% 2 2 2 6%	4199
	21st to end	Night	14% 17% 9% 20% 9% 8% 5% 3 4 3 8%	4532
February	1st to 10th	Night	10% 19% 8% 17% 11% 7% 6% 3 4 3 12%	2470
	11th to 20th	Night	10% 16% 8% 18% 9% 6% 5% 4 4 5% 16%	2403
	21st to end	Night	12% 16% 6% 14% 9% 6% 5% 4 4 5% 19%	1951
March	1st to 10th	Night	12% 15% 6% 10% 5% 4 5% 4 5% 7% 29%	3455
	11th to 20th	Night	9% 17% 8% 11% 5% 4 4 3 5% 5% 29%	3479
	21st to end	Night	11% 12% 5% 12% 5% 5% 5% 3 5% 5% 32%	3817
April	1st to 10th	Night	17% 16% 4 9% 5% 4 4 4 5% 5% 28%	1976
	11th to 20th	Night	17% 13% 3 7% 4 4 4 2 3 7% 37%	1738
	21st to end	Night	17% 14% 5% 8% 5% 4 4 3 4 6% 31%	1710
May	1st to 10th	Night	14% 8% 2 7% 4 4 4 3 5% 7% 40%	2833
	11th to 20th	Night	15% 8% 2 5% 4 4 4 4 5% 7% 41%	2591
	21st to end	Night	10% 7% 2 6% 3 4 4 3 5% 7% 49%	2738
June	1st to 10th	Night	15% 8% 3 6% 5% 5% 5% 4 6% 7% 38%	1468
	11th to 20th	Night	11% 5% 2 6% 5% 5% 5% 4 6% 9% 42%	1330
	21st to end	Night	14% 7% 2 5% 4 4 3 4 5% 8% 43%	1330
July	1st to 10th	Night	9% 7% 3 6% 4 3 4 3 5% 8% 46%	2210
	11th to 20th	Night	13% 6% 1 4 4 3 3 3 5% 7% 51%	2382
	21st to end	Night	7% 7% 2 6% 4 4 5% 4 6% 8% 47%	3087
August	1st to 10th	Night	11% 7% 3 6% 5% 3 5% 4 6% 7% 44%	2825
	11th to 20th	Night	14% 7% 3 7% 5% 4 4 4 5% 7% 41%	2785
	21st to end	Night	14% 6% 2 6% 4 4 5% 3 5% 7% 45%	3174
September	1st to 10th	Night	13% 5% 2 6% 4 3 4 4 5% 7% 47%	1900
	11th to 20th	Night	12% 7% 2 4 3 3 4 3 5% 7% 49%	2075
	21st to end	Night	18% 9% 2 7% 4 4 5% 3 5% 6% 36%	2090
October	1st to 10th	Night	19% 10% 3 6% 4 4 4 3 4 7% 35%	2276
	11th to 20th	Night	21% 15% 3 8% 4 5% 4 3 5% 6% 26%	2280
	21st to end	Night	21% 18% 4 8% 6% 4 4 4 5% 5% 20%	2536
November	1st to 10th	Night	17% 20% 5% 8% 5% 4 4 3 4 5% 26%	2571
	11th to 20th	Night	14% 19% 6% 12% 6% 5% 5% 3 5% 6% 20%	2660
	21st to end	Night	16% 20% 8% 13% 6% 4 5% 3 4 5% 15%	2660
December	1st to 10th	Night	16% 24% 8% 17% 6% 4 4 3 4 4 10%	2660
	11th to 20th	Night	10% 22% 10% 20% 8% 5% 4 3 4 4 11%	3288
	21st to end	Night	19% 21% 9% 21% 6% 5% 4 3 3 3 7%	5140

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	81% 6% 8% 4	2209
	11th to 20th	Day	85% 7% 3 3 2	2753
	21st to end	Day	81% 6% 7% 4 2	3124
February	1st to 10th	Day	76% 7% 7% 8% 2	1710
	11th to 20th	Day	73% 6% 7% 8% 5% 1	1672
	21st to end	Day	71% 6% 8% 10% 4	1498
March	1st to 10th	Day	61% 6% 11% 13% 9%	3387
	11th to 20th	Day	63% 6% 8% 16% 5% 1	3480
	21st to end	Day	55% 6% 13% 16% 9% 1	3815
April	1st to 10th	Day	60% 6% 9% 16% 8% 1	2204
	11th to 20th	Day	52% 5% 9% 19% 15% 1	2408
	21st to end	Day	53% 6% 10% 17% 12% 2	2470
May	1st to 10th	Day	45% 7% 13% 20% 15% 1	4120
	11th to 20th	Day	46% 9% 13% 21% 10% 1	4304
	21st to end	Day	39% 6% 12% 21% 18% 4	4837
June	1st to 10th	Day	44% 8% 11% 21% 15% 1	2707
	11th to 20th	Day	38% 8% 12% 23% 17% 1	2850
	21st to end	Day	44% 7% 13% 22% 13% 1	2850
July	1st to 10th	Day	47% 6% 14% 18% 14% 1	4686
	11th to 20th	Day	37% 7% 12% 33% 12% 1	4495
	21st to end	Day	38% 6% 11% 26% 17% 2	4324
August	1st to 10th	Day	43% 7% 13% 23% 13% 1	4091
	11th to 20th	Day	46% 7% 15% 23% 9%	4083
	21st to end	Day	38% 6% 13% 31% 11% 1	4448
September	1st to 10th	Day	45% 7% 13% 23% 11% 2	2280
	11th to 20th	Day	40% 7% 14% 27% 13%	2103
	21st to end	Day	50% 8% 11% 22% 8% 1	2090
October	1st to 10th	Day	47% 6% 11% 24% 11% 1	3163
	11th to 20th	Day	56% 5% 9% 18% 11%	3140
	21st to end	Day	63% 6% 11% 16% 4	3371
November	1st to 10th	Day	61% 7% 11% 14% 6%	1666
	11th to 20th	Day	67% 9% 10% 9% 5%	1520
	21st to end	Day	75% 7% 9% 8% 1	1520
December	1st to 10th	Day	81% 7% 7% 5% 1	1520
	11th to 20th	Day	77% 8% 9% 6% 1	1906
	21st to end	Day	82% 6% 6% 5%	2515
January	1st to 10th	Night	82% 7% 6% 4	4748
	11th to 20th	Night	83% 8% 5% 3 1	4199
	21st to end	Night	79% 9% 7% 4 2	4532
February	1st to 10th	Night	75% 7% 7% 9% 2	2470
	11th to 20th	Night	69% 7% 9% 12% 3	2405
	21st to end	Night	64% 8% 10% 11% 6%	1951
March	1st to 10th	Night	52% 7% 14% 18% 8%	3465
	11th to 20th	Night	53% 9% 13% 16% 8% 1	3480
	21st to end	Night	51% 7% 11% 20% 9% 1	3817
April	1st to 10th	Night	57% 5% 8% 19% 11%	1976
	11th to 20th	Night	49% 5% 8% 19% 17% 1	1738
	21st to end	Night	54% 6% 8% 15% 16% 2	1710
May	1st to 10th	Night	41% 7% 12% 19% 16% 4	2840
	11th to 20th	Night	41% 8% 12% 24% 12% 2	2592
	21st to end	Night	33% 9% 12% 24% 20% 2	2739
June	1st to 10th	Night	43% 7% 11% 20% 18% 2	1468
	11th to 20th	Night	37% 7% 13% 26% 18% 1	1330
	21st to end	Night	39% 7% 14% 25% 13% 2	1330
July	1st to 10th	Night	36% 5% 14% 24% 18% 4	2175
	11th to 20th	Night	33% 5% 12% 34% 15% 1	2340
	21st to end	Night	34% 7% 13% 28% 17% 1	2988
August	1st to 10th	Night	39% 5% 12% 27% 16% 1	2814
	11th to 20th	Night	42% 6% 16% 22% 12% 1	2812
	21st to end	Night	38% 7% 12% 30% 12% 1	3174
September	1st to 10th	Night	34% 9% 14% 29% 13% 1	1900
	11th to 20th	Night	33% 8% 14% 28% 16% 1	2075
	21st to end	Night	47% 9% 11% 24% 9% 1	2090
October	1st to 10th	Night	42% 6% 9% 25% 17% 1	3796
	11th to 20th	Night	52% 5% 12% 18% 13%	3779
	21st to end	Night	55% 7% 14% 19% 5%	4172
November	1st to 10th	Night	60% 7% 10% 16% 6% 1	2571
	11th to 20th	Night	64% 8% 13% 10% 4 1	2660
	21st to end	Night	71% 8% 12% 7% 1	2660
December	1st to 10th	Night	77% 9% 8% 5% 1	2660
	11th to 20th	Night	76% 7% 10% 6% 1	3288
	21st to end	Night	84% 6% 5% 5%	5140

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	17% 29% 33% 15% 5% 1	180
	11th to 20th	Day	16% 32% 36% 12% 3	263
	21st to end	Day	23% 22% 34% 19% 2	297
February	1st to 10th	Day	23% 31% 33% 10% 2	270
	11th to 20th	Day	20% 30% 39% 9% 2	270
	21st to end	Day	25% 32% 34% 9%	225
March	1st to 10th	Day	20% 23% 37% 16% 4	423
	11th to 20th	Day	19% 22% 38% 17% 4	460
	21st to end	Day	26% 16% 33% 18% 6%	506
April	1st to 10th	Day	23% 21% 34% 17% 5%	460
	11th to 20th	Day	28% 21% 24% 14% 8% 4	452
	21st to end	Day	27% 16% 29% 20% 7% 1	460
May	1st to 10th	Day	20% 16% 32% 22% 9% 2	463
	11th to 20th	Day	19% 9% 30% 25% 14% 3	487
	21st to end	Day	17% 11% 27% 27% 14% 3	529
June	1st to 10th	Day	18% 14% 28% 28% 12% 1	537
	11th to 20th	Day	14% 12% 32% 29% 10% 3	680
	21st to end	Day	20% 9% 31% 27% 10% 3	680
July	1st to 10th	Day	13% 10% 27% 31% 17% 3	671
	11th to 20th	Day	13% 9% 29% 29% 13% 6%	580
	21st to end	Day	10% 6% 31% 32% 17% 4	532
August	1st to 10th	Day	13% 8% 24% 32% 15% 7%	486
	11th to 20th	Day	15% 6% 21% 30% 19% 8%	479
	21st to end	Day	14% 11% 25% 30% 16% 5%	539
September	1st to 10th	Day	16% 13% 25% 25% 16% 6%	490
	11th to 20th	Day	13% 8% 23% 27% 20% 9%	490
	21st to end	Day	15% 15% 28% 24% 14% 4	490
October	1st to 10th	Day	24% 16% 24% 20% 12% 3	490
	11th to 20th	Day	24% 24% 32% 16% 4	490
	21st to end	Day	33% 26% 25% 13% 3	506
November	1st to 10th	Day	25% 28% 29% 13% 5%	257
	11th to 20th	Day	24% 29% 33% 11% 2 1	180
	21st to end	Day	23% 29% 38% 9% 1	180
December	1st to 10th	Day	21% 35% 32% 12% 1	180
	11th to 20th	Day	21% 37% 31% 9% 2	180
	21st to end	Day	26% 34% 32% 6% 2	198
January	1st to 10th	Night	20% 28% 33% 16% 4	950
	11th to 20th	Night	22% 24% 33% 17% 4 1	790
	21st to end	Night	15% 18% 40% 21% 5% 1	836
February	1st to 10th	Night	19% 26% 35% 19% 2	760
	11th to 20th	Night	18% 21% 36% 20% 4	743
	21st to end	Night	21% 24% 33% 18% 3	628
March	1st to 10th	Night	17% 20% 37% 20% 5%	760
	11th to 20th	Night	17% 21% 37% 19% 4 1	760
	21st to end	Night	19% 16% 31% 26% 7% 1	836
April	1st to 10th	Night	23% 17% 33% 24% 3	760
	11th to 20th	Night	21% 15% 31% 23% 9% 1	614
	21st to end	Night	23% 14% 28% 25% 11%	570
May	1st to 10th	Night	19% 8% 28% 33% 12% 2	570
	11th to 20th	Night	18% 8% 27% 35% 11% 1	431
	21st to end	Night	13% 6% 27% 39% 15%	411
June	1st to 10th	Night	17% 8% 29% 34% 10% 1	380
	11th to 20th	Night	11% 10% 23% 40% 16%	380
	21st to end	Night	18% 6% 24% 35% 17% 1	380
July	1st to 10th	Night	9% 5% 19% 47% 19% 1	370
	11th to 20th	Night	10% 5% 28% 34% 21% 1	382
	21st to end	Night	10% 4 24% 42% 19% 1	624
August	1st to 10th	Night	12% 5% 21% 36% 25% 1	567
	11th to 20th	Night	10% 5% 19% 36% 26% 4	564
	21st to end	Night	16% 6% 23% 30% 23% 2	651
September	1st to 10th	Night	14% 8% 25% 32% 17% 5%	760
	11th to 20th	Night	16% 6% 21% 35% 18% 4	760
	21st to end	Night	19% 11% 22% 30% 14% 4	760
October	1st to 10th	Night	24% 10% 29% 22% 13% 1	760
	11th to 20th	Night	27% 18% 27% 21% 6% 1	760
	21st to end	Night	32% 20% 28% 16% 3	836
November	1st to 10th	Night	28% 17% 31% 17% 7%	771
	11th to 20th	Night	22% 28% 29% 16% 4 1	760
	21st to end	Night	24% 24% 34% 16% 2	760
December	1st to 10th	Night	26% 25% 33% 12% 3	760
	11th to 20th	Night	21% 27% 36% 13% 2 1	760
	21st to end	Night	27% 25% 34% 13% 1	988

Page generated at 2024-11-05 08:15:54. Version ac07

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