Bracebridge
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bracebridge clear sky chart from 2005-11-06 to 2024-04-25.

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	17% 12% 4 8% 6% 3 4 4 5% 6% 30%	83798
	Night	17% 13% 5% 8% 6% 3 4 4 4 6% 28%	85299
Transparency	Day	54% 6% 11% 18% 9% 1	83504
	Night	57% 6% 11% 17% 9% 1	85129
Seeing	Day	25% 13% 31% 19% 9% 3	14095
	Night	25% 11% 29% 25% 10% 1	23072

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	16% 22% 12% 12% 6% 3 3 2 3 3 19%	2517
	11th to 20th	Day	12% 17% 10% 15% 13% 5% 4 4 4 4 13%	2628
	21st to end	Day	18% 21% 9% 13% 7% 3 3 3 3 4 16%	3124
February	1st to 10th	Day	13% 19% 8% 15% 8% 5% 5% 3 4 3 18%	1710
	11th to 20th	Day	14% 15% 7% 12% 8% 4 4 4 4 5% 24%	1663
	21st to end	Day	18% 17% 7% 10% 7% 4 6% 3 4 4 20%	1431
March	1st to 10th	Day	18% 16% 5% 7% 6% 3 4 4 5% 6% 27%	3432
	11th to 20th	Day	11% 18% 7% 9% 7% 4 5% 5% 4 6% 25%	3480
	21st to end	Day	15% 11% 4 6% 5% 3 4 5% 4 5% 39%	3815
April	1st to 10th	Day	21% 13% 4 7% 5% 3 4 4 4 6% 28%	2261
	11th to 20th	Day	23% 10% 3 5% 5% 3 4 4 4 5% 34%	2346
	21st to end	Day	22% 11% 4 5% 5% 3 3 4 4 5% 33%	2394
May	1st to 10th	Day	20% 8% 2 6% 6% 3 5% 6% 5% 7% 32%	2382
	11th to 20th	Day	17% 9% 3 5% 5% 3 4 4 5% 7% 38%	2478
	21st to end	Day	14% 6% 3 5% 5% 4 6% 5% 5% 8% 40%	2725
June	1st to 10th	Day	19% 8% 3 5% 5% 3 4 4 6% 7% 36%	2520
	11th to 20th	Day	16% 6% 3 4 6% 3 5% 5% 6% 9% 37%	2667
	21st to end	Day	18% 7% 2 6% 5% 3 5% 5% 5% 8% 36%	2700
July	1st to 10th	Day	12% 6% 2 5% 4 3 5% 5% 6% 9% 43%	2700
	11th to 20th	Day	13% 7% 3 5% 5% 3 5% 5% 6% 8% 40%	2538
	21st to end	Day	13% 6% 3 6% 6% 3 5% 6% 7% 9% 38%	2651
August	1st to 10th	Day	13% 6% 3 6% 5% 3 5% 6% 6% 9% 39%	2327
	11th to 20th	Day	14% 6% 2 5% 5% 3 5% 6% 7% 9% 38%	2303
	21st to end	Day	14% 6% 3 6% 6% 4 6% 5% 6% 9% 36%	2490
September	1st to 10th	Day	15% 7% 3 6% 5% 3 6% 5% 6% 7% 39%	2160
	11th to 20th	Day	15% 6% 2 5% 5% 3 5% 4 5% 7% 42%	2073
	21st to end	Day	19% 9% 3 6% 5% 3 5% 4 4 6% 35%	1934
October	1st to 10th	Day	23% 7% 2 6% 6% 3 4 5% 4 7% 32%	1800
	11th to 20th	Day	28% 9% 4 7% 8% 3 5% 4 3 7% 22%	1800
	21st to end	Day	32% 11% 4 7% 7% 3 3 3 4 5% 21%	1980
November	1st to 10th	Day	19% 13% 4 8% 5% 3 5% 5% 5% 7% 27%	1531
	11th to 20th	Day	18% 16% 5% 9% 7% 3 5% 5% 5% 5% 22%	1520
	21st to end	Day	22% 21% 5% 9% 7% 3 4 5% 5% 4 16%	1520
December	1st to 10th	Day	19% 26% 8% 10% 4 3 4 3 3 4 16%	1520
	11th to 20th	Day	20% 21% 6% 12% 6% 3 3 2 3 3 20%	1906
	21st to end	Day	25% 20% 7% 11% 7% 3 4 3 3 3 13%	2772
January	1st to 10th	Night	17% 22% 11% 13% 7% 4 4 3 3 3 13%	4429
	11th to 20th	Night	14% 16% 7% 17% 10% 5% 6% 5% 4 5% 14%	4330
	21st to end	Night	18% 18% 9% 11% 7% 4 5% 4 4 4 16%	4532
February	1st to 10th	Night	13% 18% 7% 12% 9% 5% 5% 4 4 5% 18%	2470
	11th to 20th	Night	13% 15% 9% 11% 8% 4 4 4 4 4 25%	2403
	21st to end	Night	17% 15% 7% 9% 8% 4 5% 4 4 5% 23%	2022
March	1st to 10th	Night	16% 13% 5% 9% 6% 3 4 4 4 6% 30%	3408
	11th to 20th	Night	12% 17% 7% 8% 6% 3 4 5% 4 5% 28%	3479
	21st to end	Night	15% 9% 5% 6% 7% 3 5% 5% 5% 6% 35%	3817
April	1st to 10th	Night	22% 13% 4 6% 6% 3 4 3 4 6% 29%	1919
	11th to 20th	Night	20% 9% 4 6% 6% 3 4 4 5% 5% 36%	1800
	21st to end	Night	19% 9% 4 7% 7% 3 5% 5% 4 6% 32%	1665
May	1st to 10th	Night	20% 6% 3 5% 4 2 5% 4 5% 9% 38%	1576
	11th to 20th	Night	16% 7% 3 4 4 3 4 5% 5% 7% 44%	1415
	21st to end	Night	11% 5% 2 4 5% 2 5% 5% 5% 9% 45%	1550
June	1st to 10th	Night	16% 7% 4 6% 5% 3 4 5% 6% 6% 37%	1440
	11th to 20th	Night	12% 7% 2 5% 4 2 4 5% 6% 9% 42%	1288
	21st to end	Night	14% 7% 3 6% 5% 3 4 6% 4 8% 38%	1260
July	1st to 10th	Night	9% 5% 2 4 4 3 4 5% 6% 7% 51%	1260
	11th to 20th	Night	13% 6% 3 6% 4 3 5% 4 6% 7% 45%	1417
	21st to end	Night	12% 6% 2 4 4 3 5% 5% 6% 7% 46%	1664
August	1st to 10th	Night	10% 5% 2 4 5% 3 4 5% 6% 8% 47%	1611
	11th to 20th	Night	10% 6% 3 4 6% 3 5% 5% 5% 7% 45%	1598
	21st to end	Night	15% 6% 2 5% 5% 3 5% 4 5% 6% 42%	1846
September	1st to 10th	Night	13% 6% 3 5% 5% 2 4 5% 6% 8% 44%	1800
	11th to 20th	Night	15% 5% 3 4 5% 3 3 4 4 7% 47%	1884
	21st to end	Night	18% 7% 3 5% 5% 3 4 4 4 6% 41%	2025
October	1st to 10th	Night	19% 8% 3 6% 6% 3 6% 4 5% 6% 35%	2160
	11th to 20th	Night	26% 11% 3 7% 6% 3 4 4 5% 5% 26%	2160
	21st to end	Night	27% 13% 4 8% 6% 3 3 4 3 5% 23%	2376
November	1st to 10th	Night	21% 13% 3 6% 5% 3 4 4 4 6% 32%	2543
	11th to 20th	Night	18% 15% 5% 8% 5% 3 5% 4 5% 6% 25%	2660
	21st to end	Night	24% 17% 6% 8% 7% 3 5% 5% 4 6% 17%	2660
December	1st to 10th	Night	21% 23% 7% 10% 6% 3 5% 3 3 5% 14%	2660
	11th to 20th	Night	19% 21% 9% 12% 6% 3 4 3 3 4 17%	3288
	21st to end	Night	25% 21% 7% 12% 7% 3 4 3 3 4 11%	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	72% 5% 8% 9% 6%	2518
	11th to 20th	Day	74% 6% 7% 7% 6%	2628
	21st to end	Day	73% 5% 7% 8% 6% 1	3124
February	1st to 10th	Day	72% 4 7% 12% 4 1	1710
	11th to 20th	Day	64% 5% 9% 13% 8% 1	1672
	21st to end	Day	68% 4 7% 13% 7%	1431
March	1st to 10th	Day	58% 6% 14% 10% 10%	3435
	11th to 20th	Day	60% 6% 11% 15% 7% 1	3480
	21st to end	Day	46% 6% 10% 20% 15% 2	3815
April	1st to 10th	Day	57% 5% 9% 18% 9% 2	2261
	11th to 20th	Day	53% 5% 8% 21% 13% 1	2346
	21st to end	Day	54% 5% 8% 19% 12% 3	2394
May	1st to 10th	Day	50% 5% 10% 20% 12% 2	2382
	11th to 20th	Day	46% 6% 10% 24% 13% 1	2482
	21st to end	Day	42% 7% 13% 21% 14% 3	2725
June	1st to 10th	Day	48% 7% 10% 22% 13% 1	2520
	11th to 20th	Day	42% 8% 11% 23% 14% 2	2667
	21st to end	Day	46% 7% 13% 22% 11% 1	2700
July	1st to 10th	Day	35% 9% 13% 27% 14% 1	2626
	11th to 20th	Day	40% 9% 13% 27% 11% 1	2462
	21st to end	Day	42% 8% 13% 26% 10% 1	2503
August	1st to 10th	Day	40% 9% 15% 23% 11% 1	2314
	11th to 20th	Day	40% 9% 17% 24% 9%	2303
	21st to end	Day	43% 8% 15% 23% 10% 1	2490
September	1st to 10th	Day	43% 7% 14% 25% 10% 1	2160
	11th to 20th	Day	40% 7% 13% 28% 10% 1	2073
	21st to end	Day	49% 7% 11% 25% 8%	1934
October	1st to 10th	Day	52% 7% 12% 18% 10% 1	1800
	11th to 20th	Day	63% 8% 12% 12% 6% 1	1800
	21st to end	Day	66% 5% 9% 13% 6%	1980
November	1st to 10th	Day	55% 8% 13% 19% 5%	1531
	11th to 20th	Day	62% 8% 11% 12% 5% 1	1520
	21st to end	Day	70% 5% 11% 10% 3	1520
December	1st to 10th	Day	73% 4 9% 10% 3 1	1520
	11th to 20th	Day	70% 5% 6% 11% 7%	1906
	21st to end	Day	77% 4 5% 10% 4	2772
January	1st to 10th	Night	76% 5% 7% 8% 4	4429
	11th to 20th	Night	72% 8% 8% 7% 4 1	4330
	21st to end	Night	71% 8% 7% 8% 5% 1	4532
February	1st to 10th	Night	69% 5% 9% 12% 5% 1	2470
	11th to 20th	Night	62% 6% 8% 16% 7%	2405
	21st to end	Night	64% 5% 9% 15% 7%	2022
March	1st to 10th	Night	55% 5% 13% 15% 10% 1	3418
	11th to 20th	Night	57% 7% 14% 14% 7% 1	3480
	21st to end	Night	45% 9% 10% 22% 13% 1	3817
April	1st to 10th	Night	57% 4 8% 18% 10% 2	1919
	11th to 20th	Night	49% 6% 7% 22% 15% 2	1800
	21st to end	Night	53% 6% 9% 15% 15% 2	1665
May	1st to 10th	Night	44% 4 12% 20% 17% 3	1576
	11th to 20th	Night	40% 6% 10% 23% 20% 2	1416
	21st to end	Night	34% 8% 14% 25% 16% 3	1551
June	1st to 10th	Night	45% 8% 10% 21% 14% 1	1440
	11th to 20th	Night	38% 6% 13% 24% 19% 1	1288
	21st to end	Night	44% 6% 15% 23% 11% 1	1260
July	1st to 10th	Night	30% 7% 14% 26% 20% 3	1225
	11th to 20th	Night	38% 6% 13% 30% 13% 1	1371
	21st to end	Night	35% 7% 13% 29% 14% 1	1571
August	1st to 10th	Night	33% 7% 18% 29% 12% 1	1600
	11th to 20th	Night	36% 9% 16% 25% 13% 1	1598
	21st to end	Night	40% 7% 14% 27% 10% 1	1846
September	1st to 10th	Night	37% 7% 16% 26% 12% 1	1800
	11th to 20th	Night	36% 7% 16% 31% 11%	1884
	21st to end	Night	44% 6% 13% 28% 9%	2025
October	1st to 10th	Night	50% 7% 11% 19% 12%	2160
	11th to 20th	Night	58% 7% 12% 18% 5%	2160
	21st to end	Night	64% 6% 10% 12% 9% 1	2376
November	1st to 10th	Night	53% 6% 12% 21% 7% 1	2543
	11th to 20th	Night	59% 7% 12% 14% 7% 1	2660
	21st to end	Night	68% 7% 11% 11% 3	2660
December	1st to 10th	Night	74% 6% 8% 9% 4	2660
	11th to 20th	Night	70% 7% 8% 10% 5%	3288
	21st to end	Night	78% 5% 6% 8% 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	26% 21% 34% 12% 7% 1	180
	11th to 20th	Day	25% 21% 38% 11% 5% 1	213
	21st to end	Day	30% 13% 37% 15% 4	297
February	1st to 10th	Day	31% 26% 33% 7% 4	270
	11th to 20th	Day	27% 24% 40% 7% 1	270
	21st to end	Day	39% 24% 30% 7%	234
March	1st to 10th	Day	26% 17% 40% 14% 3	460
	11th to 20th	Day	24% 19% 35% 17% 4 1	460
	21st to end	Day	34% 13% 32% 15% 6%	506
April	1st to 10th	Day	28% 19% 30% 15% 6% 1	460
	11th to 20th	Day	38% 15% 22% 14% 8% 3	452
	21st to end	Day	33% 14% 32% 13% 7% 1	437
May	1st to 10th	Day	29% 12% 29% 20% 6% 4	423
	11th to 20th	Day	23% 15% 30% 19% 10% 3	447
	21st to end	Day	21% 13% 31% 21% 12% 2	485
June	1st to 10th	Day	24% 12% 32% 25% 6% 2	450
	11th to 20th	Day	19% 13% 29% 24% 13% 2	597
	21st to end	Day	21% 10% 37% 23% 7% 2	630
July	1st to 10th	Day	13% 8% 32% 30% 13% 4	621
	11th to 20th	Day	19% 8% 25% 29% 14% 6%	461
	21st to end	Day	15% 9% 33% 28% 10% 6%	488
August	1st to 10th	Day	17% 4 29% 29% 15% 7%	446
	11th to 20th	Day	17% 4 25% 29% 18% 8%	439
	21st to end	Day	18% 8% 30% 23% 14% 6%	495
September	1st to 10th	Day	16% 9% 31% 22% 15% 7%	450
	11th to 20th	Day	16% 8% 28% 25% 16% 8%	450
	21st to end	Day	23% 12% 26% 25% 12% 2	450
October	1st to 10th	Day	29% 11% 24% 18% 14% 4	450
	11th to 20th	Day	32% 13% 33% 16% 4 2	450
	21st to end	Day	39% 16% 28% 14% 3	495
November	1st to 10th	Day	33% 18% 31% 16% 3	211
	11th to 20th	Day	31% 23% 29% 12% 5%	180
	21st to end	Day	38% 18% 33% 10% 1	180
December	1st to 10th	Day	36% 13% 34% 14% 2 1	180
	11th to 20th	Day	37% 24% 21% 14% 3 1	180
	21st to end	Day	39% 21% 29% 9% 2 1	198
January	1st to 10th	Night	31% 16% 30% 18% 5%	760
	11th to 20th	Night	32% 15% 29% 18% 5% 1	760
	21st to end	Night	23% 10% 36% 23% 8% 1	836
February	1st to 10th	Night	24% 19% 34% 20% 3	760
	11th to 20th	Night	22% 17% 35% 19% 6%	743
	21st to end	Night	28% 18% 30% 20% 4	628
March	1st to 10th	Night	22% 17% 36% 21% 3	760
	11th to 20th	Night	24% 16% 34% 21% 5% 1	760
	21st to end	Night	22% 13% 31% 25% 8%	836
April	1st to 10th	Night	29% 13% 31% 21% 6%	760
	11th to 20th	Night	28% 12% 29% 21% 9% 1	676
	21st to end	Night	26% 9% 30% 25% 9% 1	555
May	1st to 10th	Night	25% 3 26% 32% 12% 1	496
	11th to 20th	Night	19% 9% 31% 29% 12%	354
	21st to end	Night	13% 5% 35% 33% 14%	389
June	1st to 10th	Night	21% 5% 30% 33% 11% 1	360
	11th to 20th	Night	17% 7% 24% 39% 12%	360
	21st to end	Night	19% 4 23% 40% 14% 1	360
July	1st to 10th	Night	12% 3 19% 48% 18% 1	350
	11th to 20th	Night	16% 4 24% 36% 19% 1	348
	21st to end	Night	12% 4 23% 39% 20% 1	484
August	1st to 10th	Night	13% 3 17% 38% 27% 2	537
	11th to 20th	Night	13% 3 17% 38% 26% 3	534
	21st to end	Night	18% 5% 25% 29% 22% 2	658
September	1st to 10th	Night	16% 6% 25% 33% 18% 3	720
	11th to 20th	Night	18% 4 24% 30% 20% 4	720
	21st to end	Night	22% 7% 20% 32% 17% 3	720
October	1st to 10th	Night	23% 10% 27% 27% 13% 1	720
	11th to 20th	Night	31% 10% 30% 20% 8% 1	720
	21st to end	Night	34% 14% 29% 20% 4	792
November	1st to 10th	Night	30% 10% 26% 26% 7% 1	740
	11th to 20th	Night	28% 18% 29% 19% 6% 1	760
	21st to end	Night	35% 13% 27% 21% 4 1	760
December	1st to 10th	Night	35% 17% 30% 14% 4	760
	11th to 20th	Night	31% 16% 34% 14% 3 1	760
	21st to end	Night	35% 13% 30% 18% 3	836

Page generated at 2024-04-22 09:25:44. Version ac07

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