Brampton BrightSkies Observatory
Clear Sky Chart
History

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

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	14% 9% 3 8% 5% 5% 5% 4 6% 7% 33%	101691
	Night	15% 9% 3 8% 5% 5% 5% 4 5% 7% 35%	97244
Transparency	Day	47% 7% 13% 21% 11% 1	101458
	Night	48% 7% 12% 21% 11% 1	97096
Seeing	Day	18% 12% 29% 25% 12% 5%	14654
	Night	18% 10% 30% 29% 11% 1	23819

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% 14% 5% 11% 5% 5% 4 4 5% 5% 26%	2517
	11th to 20th	Day	11% 18% 6% 15% 9% 6% 4 3 4 5% 18%	2782
	21st to end	Day	21% 20% 6% 10% 6% 4 5% 3 4 4 17%	3124
February	1st to 10th	Day	14% 16% 4 12% 8% 6% 5% 4 5% 6% 22%	1710
	11th to 20th	Day	11% 14% 5% 12% 7% 5% 5% 4 5% 7% 25%	1663
	21st to end	Day	16% 14% 4 11% 5% 4 4 4 5% 6% 26%	1473
March	1st to 10th	Day	18% 12% 5% 8% 6% 4 5% 3 5% 5% 30%	3432
	11th to 20th	Day	10% 15% 4 9% 6% 5% 5% 4 5% 6% 29%	3480
	21st to end	Day	15% 10% 3 8% 5% 4 4 3 5% 6% 37%	3815
April	1st to 10th	Day	15% 11% 4 10% 6% 5% 4 3 5% 7% 30%	2232
	11th to 20th	Day	18% 8% 3 7% 4 4 5% 3 4 6% 36%	2339
	21st to end	Day	19% 10% 2 7% 5% 5% 4 3 5% 6% 34%	2470
May	1st to 10th	Day	18% 8% 3 7% 5% 4 4 3 6% 9% 34%	4108
	11th to 20th	Day	16% 9% 3 8% 6% 5% 5% 4 6% 7% 32%	4351
	21st to end	Day	11% 5% 2 6% 4 4 4 3 6% 8% 46%	4837
June	1st to 10th	Day	13% 7% 2 7% 5% 5% 5% 5% 6% 8% 38%	2660
	11th to 20th	Day	11% 6% 2 6% 5% 5% 4 5% 8% 9% 40%	2660
	21st to end	Day	12% 6% 2 6% 4 5% 5% 5% 6% 9% 39%	2835
July	1st to 10th	Day	9% 4 2 6% 5% 5% 6% 5% 8% 10% 40%	4536
	11th to 20th	Day	9% 4 2 5% 4 4 5% 5% 8% 9% 45%	4440
	21st to end	Day	7% 5% 2 7% 6% 5% 6% 5% 7% 9% 41%	4472
August	1st to 10th	Day	16% 7% 3 6% 4 4 5% 4 7% 8% 37%	4104
	11th to 20th	Day	9% 7% 3 8% 6% 5% 6% 5% 7% 9% 35%	4044
	21st to end	Day	8% 5% 2 6% 5% 5% 5% 4 7% 9% 42%	4376
September	1st to 10th	Day	12% 6% 3 6% 5% 4 5% 5% 6% 8% 41%	2280
	11th to 20th	Day	10% 6% 2 6% 5% 3 4 3 5% 9% 46%	2152
	21st to end	Day	14% 6% 3 8% 6% 6% 5% 4 6% 8% 35%	2062
October	1st to 10th	Day	18% 8% 2 7% 5% 4 4 4 4 6% 36%	1900
	11th to 20th	Day	18% 8% 3 8% 6% 5% 5% 3 5% 8% 30%	1900
	21st to end	Day	23% 12% 3 8% 6% 5% 4 4 6% 6% 23%	2090
November	1st to 10th	Day	14% 11% 3 7% 5% 4 6% 3 6% 9% 32%	1609
	11th to 20th	Day	13% 12% 4 9% 6% 5% 7% 5% 7% 7% 25%	1520
	21st to end	Day	16% 16% 5% 8% 6% 5% 5% 3 7% 7% 22%	1520
December	1st to 10th	Day	16% 15% 6% 13% 6% 5% 5% 4 5% 6% 17%	1520
	11th to 20th	Day	18% 14% 5% 10% 6% 5% 5% 5% 5% 6% 21%	1906
	21st to end	Day	29% 17% 6% 12% 5% 4 3 3 4 5% 12%	2772
January	1st to 10th	Night	17% 15% 6% 11% 6% 6% 5% 3 5% 5% 23%	4429
	11th to 20th	Night	14% 13% 5% 13% 9% 8% 6% 4 5% 6% 18%	4175
	21st to end	Night	20% 12% 6% 10% 7% 6% 6% 4 5% 6% 18%	4532
February	1st to 10th	Night	13% 14% 5% 10% 7% 6% 5% 4 6% 6% 25%	2470
	11th to 20th	Night	11% 13% 5% 9% 7% 7% 5% 4 5% 6% 27%	2403
	21st to end	Night	13% 11% 5% 10% 7% 6% 5% 4 4 7% 29%	1979
March	1st to 10th	Night	18% 9% 3 8% 6% 5% 5% 3 6% 6% 31%	3408
	11th to 20th	Night	12% 9% 3 8% 5% 4 5% 3 5% 8% 37%	3479
	21st to end	Night	16% 8% 2 5% 4 4 4 3 4 6% 45%	3817
April	1st to 10th	Night	17% 10% 3 9% 5% 4 5% 4 4 5% 33%	1947
	11th to 20th	Night	16% 8% 2 6% 5% 5% 4 3 5% 6% 38%	1806
	21st to end	Night	16% 8% 2 8% 4 4 5% 4 6% 7% 37%	1710
May	1st to 10th	Night	17% 7% 3 6% 4 5% 4 4 5% 6% 40%	2833
	11th to 20th	Night	15% 8% 3 7% 4 4 5% 4 5% 8% 38%	2541
	21st to end	Night	9% 4 2 5% 4 4 4 3 5% 9% 51%	2738
June	1st to 10th	Night	12% 5% 2 6% 5% 5% 4 4 6% 9% 42%	1520
	11th to 20th	Night	8% 6% 3 6% 4 5% 5% 5% 7% 10% 44%	1520
	21st to end	Night	11% 5% 2 6% 4 4 4 3 7% 7% 46%	1332
July	1st to 10th	Night	5% 5% 2 5% 4 4 4 4 6% 9% 52%	2417
	11th to 20th	Night	11% 3 2 4 3 4 4 4 6% 8% 52%	2520
	21st to end	Night	7% 4 2 5% 3 4 5% 5% 6% 8% 51%	3077
August	1st to 10th	Night	10% 5% 2 6% 5% 4 4 4 6% 7% 47%	2825
	11th to 20th	Night	10% 5% 2 5% 3 4 4 4 5% 8% 50%	2785
	21st to end	Night	10% 5% 2 6% 4 5% 4 4 6% 8% 47%	3247
September	1st to 10th	Night	9% 5% 2 5% 5% 5% 4 4 7% 7% 48%	1900
	11th to 20th	Night	10% 5% 2 4 2 3 4 3 5% 6% 55%	2024
	21st to end	Night	15% 7% 3 7% 5% 4 4 3 5% 7% 41%	2118
October	1st to 10th	Night	17% 7% 2 7% 5% 4 4 3 6% 6% 40%	2280
	11th to 20th	Night	16% 9% 3 7% 4 5% 5% 3 5% 6% 36%	2280
	21st to end	Night	19% 10% 2 9% 5% 3 6% 4 6% 7% 29%	2508
November	1st to 10th	Night	15% 8% 2 7% 5% 4 4 4 6% 7% 38%	2472
	11th to 20th	Night	15% 10% 3 9% 6% 5% 5% 4 6% 7% 30%	2660
	21st to end	Night	18% 11% 3 9% 6% 5% 4 4 6% 7% 27%	2660
December	1st to 10th	Night	20% 13% 4 9% 7% 4 4 4 5% 7% 23%	2660
	11th to 20th	Night	14% 17% 5% 10% 6% 4 5% 4 6% 7% 21%	3288
	21st to end	Night	29% 16% 5% 10% 5% 5% 4 4 4 5% 13%	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	57% 10% 14% 12% 7%	2518
	11th to 20th	Day	68% 5% 11% 11% 4	2782
	21st to end	Day	70% 6% 9% 9% 5% 1	3124
February	1st to 10th	Day	62% 6% 12% 16% 3 1	1710
	11th to 20th	Day	58% 6% 12% 15% 8% 1	1672
	21st to end	Day	58% 6% 11% 16% 8% 1	1473
March	1st to 10th	Day	55% 5% 13% 18% 8% 1	3435
	11th to 20th	Day	53% 7% 11% 19% 9% 2	3480
	21st to end	Day	48% 5% 12% 21% 13% 2	3815
April	1st to 10th	Day	53% 5% 11% 18% 11% 1	2232
	11th to 20th	Day	47% 5% 11% 21% 15% 1	2339
	21st to end	Day	51% 5% 10% 19% 12% 2	2470
May	1st to 10th	Day	45% 7% 14% 19% 14% 1	4120
	11th to 20th	Day	47% 11% 13% 20% 8% 1	4355
	21st to end	Day	34% 7% 13% 24% 17% 3	4837
June	1st to 10th	Day	42% 8% 11% 23% 15% 2	2660
	11th to 20th	Day	38% 7% 14% 24% 16% 1	2660
	21st to end	Day	38% 7% 14% 25% 14% 1	2835
July	1st to 10th	Day	36% 5% 16% 26% 15% 2	4466
	11th to 20th	Day	31% 6% 14% 36% 12% 1	4365
	21st to end	Day	36% 7% 15% 22% 19% 1	4329
August	1st to 10th	Day	42% 6% 15% 22% 14% 1	4091
	11th to 20th	Day	42% 6% 18% 24% 10%	4083
	21st to end	Day	35% 6% 13% 35% 10% 1	4376
September	1st to 10th	Day	38% 9% 14% 27% 11% 1	2280
	11th to 20th	Day	34% 6% 14% 31% 15% 1	2152
	21st to end	Day	44% 7% 15% 25% 9%	2062
October	1st to 10th	Day	46% 7% 15% 19% 11% 1	1900
	11th to 20th	Day	51% 7% 13% 20% 8% 1	1900
	21st to end	Day	59% 7% 13% 16% 5% 1	2090
November	1st to 10th	Day	47% 7% 16% 21% 8% 1	1609
	11th to 20th	Day	53% 7% 15% 15% 8%	1520
	21st to end	Day	59% 7% 15% 16% 3	1520
December	1st to 10th	Day	65% 7% 12% 12% 3	1520
	11th to 20th	Day	61% 9% 13% 12% 5%	1906
	21st to end	Day	74% 6% 9% 9% 2	2772
January	1st to 10th	Night	60% 9% 11% 15% 5%	4429
	11th to 20th	Night	64% 9% 12% 11% 3 1	4175
	21st to end	Night	64% 8% 11% 11% 5% 1	4532
February	1st to 10th	Night	57% 6% 11% 20% 5% 1	2470
	11th to 20th	Night	57% 6% 11% 17% 9%	2405
	21st to end	Night	54% 5% 14% 19% 9%	1979
March	1st to 10th	Night	51% 6% 13% 21% 7% 1	3418
	11th to 20th	Night	44% 8% 14% 21% 12% 2	3480
	21st to end	Night	41% 5% 9% 24% 19% 2	3817
April	1st to 10th	Night	51% 5% 10% 18% 14% 1	1947
	11th to 20th	Night	46% 6% 10% 20% 16% 2	1806
	21st to end	Night	46% 7% 10% 19% 16% 2	1710
May	1st to 10th	Night	43% 8% 11% 18% 17% 3	2840
	11th to 20th	Night	43% 12% 13% 19% 11% 2	2542
	21st to end	Night	29% 8% 13% 24% 23% 3	2739
June	1st to 10th	Night	38% 7% 11% 25% 18% 2	1520
	11th to 20th	Night	35% 6% 12% 24% 21% 2	1520
	21st to end	Night	36% 6% 13% 26% 17% 1	1332
July	1st to 10th	Night	29% 5% 15% 26% 22% 4	2377
	11th to 20th	Night	31% 4 13% 34% 17% 1	2472
	21st to end	Night	30% 7% 16% 29% 17% 2	2979
August	1st to 10th	Night	37% 5% 12% 28% 15% 3	2814
	11th to 20th	Night	33% 5% 15% 33% 12% 1	2812
	21st to end	Night	35% 6% 13% 30% 15% 1	3247
September	1st to 10th	Night	33% 7% 15% 29% 15% 1	1900
	11th to 20th	Night	29% 6% 11% 34% 19%	2024
	21st to end	Night	42% 7% 13% 27% 11% 1	2118
October	1st to 10th	Night	43% 7% 11% 22% 16% 1	2280
	11th to 20th	Night	48% 7% 12% 25% 9%	2280
	21st to end	Night	53% 7% 11% 19% 10% 1	2508
November	1st to 10th	Night	44% 6% 13% 23% 12% 1	2472
	11th to 20th	Night	50% 7% 15% 18% 9% 1	2660
	21st to end	Night	55% 6% 17% 18% 4	2660
December	1st to 10th	Night	60% 7% 12% 16% 5%	2660
	11th to 20th	Night	60% 8% 14% 14% 4	3288
	21st to end	Night	72% 8% 10% 8% 2	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	22% 18% 29% 23% 7% 1	180
	11th to 20th	Day	22% 27% 30% 13% 7% 1	256
	21st to end	Day	25% 19% 31% 21% 4	297
February	1st to 10th	Day	23% 23% 39% 10% 5%	270
	11th to 20th	Day	21% 23% 39% 15% 2	270
	21st to end	Day	29% 26% 33% 11% 1	233
March	1st to 10th	Day	21% 17% 34% 22% 6%	460
	11th to 20th	Day	22% 18% 34% 19% 6% 1	460
	21st to end	Day	26% 15% 32% 20% 6% 1	506
April	1st to 10th	Day	18% 18% 35% 21% 7%	460
	11th to 20th	Day	26% 17% 28% 17% 8% 3	452
	21st to end	Day	23% 13% 33% 20% 8% 2	460
May	1st to 10th	Day	21% 10% 29% 24% 11% 5%	463
	11th to 20th	Day	17% 7% 30% 26% 13% 6%	487
	21st to end	Day	14% 6% 28% 29% 17% 5%	529
June	1st to 10th	Day	13% 10% 30% 32% 12% 3	490
	11th to 20th	Day	14% 8% 26% 31% 19% 2	490
	21st to end	Day	14% 8% 30% 32% 13% 3	665
July	1st to 10th	Day	8% 5% 24% 36% 20% 7%	542
	11th to 20th	Day	13% 5% 22% 33% 18% 9%	484
	21st to end	Day	7% 4 26% 38% 18% 7%	532
August	1st to 10th	Day	12% 6% 21% 27% 23% 11%	486
	11th to 20th	Day	7% 6% 22% 32% 20% 13%	479
	21st to end	Day	12% 7% 22% 29% 20% 10%	539
September	1st to 10th	Day	12% 7% 24% 29% 17% 11%	490
	11th to 20th	Day	9% 5% 21% 24% 25% 16%	490
	21st to end	Day	16% 9% 28% 23% 17% 7%	490
October	1st to 10th	Day	22% 11% 26% 22% 13% 6%	490
	11th to 20th	Day	19% 14% 35% 21% 9% 3	490
	21st to end	Day	28% 13% 27% 24% 7% 1	539
November	1st to 10th	Day	21% 21% 26% 21% 10% 1	257
	11th to 20th	Day	26% 18% 30% 20% 4 2	180
	21st to end	Day	25% 15% 39% 17% 3	180
December	1st to 10th	Day	26% 17% 37% 16% 3	180
	11th to 20th	Day	26% 23% 32% 15% 4	180
	21st to end	Day	26% 21% 37% 13% 3	198
January	1st to 10th	Night	23% 17% 36% 19% 5%	760
	11th to 20th	Night	26% 17% 31% 22% 4	760
	21st to end	Night	19% 11% 39% 24% 7%	836
February	1st to 10th	Night	20% 18% 38% 21% 3	760
	11th to 20th	Night	22% 14% 39% 21% 4	743
	21st to end	Night	18% 17% 38% 23% 4	628
March	1st to 10th	Night	19% 13% 37% 25% 5%	760
	11th to 20th	Night	20% 15% 36% 24% 5%	760
	21st to end	Night	20% 11% 33% 27% 8%	836
April	1st to 10th	Night	23% 10% 35% 28% 4	760
	11th to 20th	Night	19% 12% 36% 24% 8% 1	682
	21st to end	Night	20% 8% 30% 32% 10%	570
May	1st to 10th	Night	17% 6% 29% 31% 15% 2	570
	11th to 20th	Night	16% 4 28% 39% 13% 1	407
	21st to end	Night	11% 3 27% 36% 22% 1	411
June	1st to 10th	Night	14% 5% 27% 37% 17% 1	380
	11th to 20th	Night	8% 7% 28% 40% 17%	380
	21st to end	Night	12% 5% 23% 44% 16%	380
July	1st to 10th	Night	6% 3 21% 47% 21% 2	370
	11th to 20th	Night	11% 3 22% 41% 22% 2	368
	21st to end	Night	8% 3 19% 45% 24% 2	614
August	1st to 10th	Night	9% 2 16% 42% 28% 2	567
	11th to 20th	Night	8% 3 15% 43% 27% 4	564
	21st to end	Night	11% 3 23% 35% 26% 3	698
September	1st to 10th	Night	11% 7% 22% 34% 21% 5%	760
	11th to 20th	Night	12% 4 19% 31% 29% 5%	760
	21st to end	Night	17% 7% 20% 32% 20% 4	760
October	1st to 10th	Night	18% 6% 28% 27% 18% 3	760
	11th to 20th	Night	21% 11% 29% 28% 10% 1	760
	21st to end	Night	25% 10% 32% 28% 5%	836
November	1st to 10th	Night	20% 11% 29% 29% 10% 1	743
	11th to 20th	Night	19% 14% 36% 23% 7% 2	760
	21st to end	Night	24% 12% 33% 25% 5%	760
December	1st to 10th	Night	29% 13% 36% 17% 5%	760
	11th to 20th	Night	23% 14% 41% 19% 3	760
	21st to end	Night	30% 14% 33% 20% 3	836

Page generated at 2024-10-29 11:20:44. Version ac07

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