Bryan College
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bryan College 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	13% 7% 2 6% 5% 5% 5% 4 6% 8% 39%	100932
	Night	14% 6% 2 6% 4 4 4 4 5% 7% 42%	98056
Transparency	Day	42% 3 11% 24% 16% 3	104713
	Night	40% 3 10% 24% 18% 4	102413
Seeing	Day	16% 8% 20% 25% 21% 11%	14726
	Night	16% 7% 21% 32% 20% 4	24733

By Month

Percentage Cloud Cover SE (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% 12% 3 6% 4 4 4 4 6% 6% 34%	2836
	11th to 20th	Day	19% 8% 4 8% 5% 3 4 2 4 5% 39%	2840
	21st to end	Day	23% 10% 2 5% 3 3 3 3 4 7% 36%	3249
February	1st to 10th	Day	19% 9% 3 7% 4 4 4 3 5% 6% 36%	1900
	11th to 20th	Day	22% 8% 3 6% 4 4 3 3 5% 5% 36%	1848
	21st to end	Day	20% 8% 3 7% 4 5% 4 3 5% 6% 36%	1570
March	1st to 10th	Day	25% 11% 2 6% 4 4 4 3 4 5% 30%	3138
	11th to 20th	Day	14% 6% 3 6% 3 3 4 3 4 5% 49%	3480
	21st to end	Day	16% 7% 3 6% 5% 4 5% 4 5% 7% 38%	3815
April	1st to 10th	Day	12% 5% 2 6% 4 5% 5% 5% 7% 7% 42%	2238
	11th to 20th	Day	14% 6% 2 6% 4 3 4 4 6% 6% 45%	2254
	21st to end	Day	12% 6% 2 6% 5% 4 5% 4 7% 8% 43%	2418
May	1st to 10th	Day	13% 8% 3 8% 5% 4 5% 4 6% 7% 37%	4082
	11th to 20th	Day	16% 8% 3 7% 4 5% 5% 4 6% 8% 36%	4081
	21st to end	Day	10% 7% 2 7% 5% 4 5% 4 6% 10% 41%	4476
June	1st to 10th	Day	9% 6% 2 7% 5% 5% 6% 4 7% 9% 38%	2470
	11th to 20th	Day	4 4 1 5% 5% 6% 6% 6% 9% 11% 43%	2470
	21st to end	Day	7% 6% 2 5% 6% 6% 7% 5% 8% 11% 39%	2470
July	1st to 10th	Day	6% 5% 2 6% 6% 7% 8% 6% 9% 11% 33%	4120
	11th to 20th	Day	10% 5% 2 7% 6% 6% 7% 5% 8% 10% 34%	4120
	21st to end	Day	14% 10% 4 11% 7% 8% 8% 6% 6% 7% 18%	4466
August	1st to 10th	Day	5% 4 2 6% 5% 6% 7% 6% 10% 10% 40%	4104
	11th to 20th	Day	6% 4 2 6% 5% 6% 6% 5% 8% 10% 42%	3768
	21st to end	Day	7% 4 2 5% 4 5% 5% 4 7% 8% 49%	4180
September	1st to 10th	Day	11% 6% 2 6% 5% 5% 6% 5% 7% 8% 40%	2153
	11th to 20th	Day	14% 5% 2 6% 5% 4 5% 4 7% 8% 40%	2090
	21st to end	Day	14% 5% 2 5% 3 4 4 3 5% 7% 48%	2090
October	1st to 10th	Day	11% 5% 2 5% 3 3 4 3 5% 5% 55%	2090
	11th to 20th	Day	12% 5% 1 4 3 3 4 2 4 6% 56%	2008
	21st to end	Day	14% 5% 2 4 4 3 4 4 5% 7% 49%	2002
November	1st to 10th	Day	11% 4 2 5% 4 3 3 4 4 4 56%	1699
	11th to 20th	Day	14% 5% 2 5% 4 3 4 3 5% 6% 48%	1710
	21st to end	Day	16% 6% 2 6% 3 4 4 3 4 6% 46%	1710
December	1st to 10th	Day	22% 7% 3 7% 5% 4 4 4 5% 5% 36%	1710
	11th to 20th	Day	14% 8% 3 7% 6% 5% 4 4 5% 5% 39%	2153
	21st to end	Day	19% 9% 3 9% 4 4 4 3 5% 7% 33%	3124
January	1st to 10th	Night	18% 9% 3 6% 4 3 4 3 5% 6% 39%	4109
	11th to 20th	Night	19% 8% 3 6% 5% 4 4 3 5% 6% 38%	4120
	21st to end	Night	22% 12% 2 6% 4 3 3 3 4 5% 35%	4404
February	1st to 10th	Night	16% 7% 3 6% 5% 5% 4 3 5% 6% 40%	2280
	11th to 20th	Night	21% 7% 3 7% 5% 4 4 4 4 4 37%	2218
	21st to end	Night	23% 8% 3 6% 4 4 4 3 5% 5% 35%	1884
March	1st to 10th	Night	24% 8% 2 7% 4 4 4 3 5% 5% 33%	3715
	11th to 20th	Night	10% 6% 2 5% 4 4 4 3 5% 7% 49%	3480
	21st to end	Night	15% 7% 3 8% 5% 5% 4 4 5% 6% 40%	3817
April	1st to 10th	Night	12% 5% 2 5% 4 4 3 3 6% 7% 49%	1957
	11th to 20th	Night	13% 5% 2 5% 4 3 3 3 5% 6% 50%	1875
	21st to end	Night	11% 5% 2 5% 5% 3 4 4 6% 7% 48%	1762
May	1st to 10th	Night	13% 7% 3 7% 6% 5% 5% 4 6% 8% 38%	2813
	11th to 20th	Night	15% 6% 2 6% 5% 5% 5% 4 5% 8% 39%	2812
	21st to end	Night	8% 6% 2 6% 4 5% 5% 4 7% 9% 43%	3079
June	1st to 10th	Night	8% 6% 2 7% 5% 5% 7% 5% 6% 8% 41%	1710
	11th to 20th	Night	4 3 1 3 4 4 4 5% 8% 13% 51%	1710
	21st to end	Night	6% 4 2 6% 4 5% 6% 5% 7% 11% 44%	1710
July	1st to 10th	Night	8% 6% 2 6% 6% 6% 6% 5% 9% 12% 35%	2840
	11th to 20th	Night	9% 4 2 5% 4 5% 4 4 7% 11% 45%	2840
	21st to end	Night	13% 10% 3 10% 6% 6% 7% 5% 7% 9% 24%	3087
August	1st to 10th	Night	4 3 2 5% 4 5% 5% 4 8% 11% 48%	2825
	11th to 20th	Night	6% 4 2 5% 5% 4 4 4 6% 9% 50%	3057
	21st to end	Night	6% 3 1 4 4 4 5% 4 6% 9% 53%	3476
September	1st to 10th	Night	9% 6% 3 7% 5% 4 5% 4 6% 9% 43%	2006
	11th to 20th	Night	13% 6% 2 6% 4 4 5% 4 5% 7% 43%	2090
	21st to end	Night	11% 5% 2 5% 3 3 4 3 5% 6% 51%	2090
October	1st to 10th	Night	11% 4 1 4 3 3 3 2 4 6% 59%	2090
	11th to 20th	Night	13% 4 2 5% 3 4 3 3 5% 5% 55%	2171
	21st to end	Night	14% 5% 2 4 3 3 3 3 4 6% 54%	2593
November	1st to 10th	Night	12% 5% 2 6% 4 3 3 3 4 6% 54%	2452
	11th to 20th	Night	12% 6% 2 6% 4 3 3 3 4 7% 51%	2470
	21st to end	Night	17% 6% 2 5% 4 3 4 3 5% 7% 44%	2470
December	1st to 10th	Night	20% 9% 3 5% 5% 4 5% 3 4 6% 36%	2470
	11th to 20th	Night	16% 7% 2 6% 4 3 4 3 4 6% 44%	3042
	21st to end	Night	19% 8% 3 7% 5% 6% 6% 5% 6% 7% 28%	4532

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	50% 2 6% 22% 18% 2	2837
	11th to 20th	Day	51% 2 6% 19% 20% 1	2840
	21st to end	Day	51% 2 7% 23% 16% 1	3249
February	1st to 10th	Day	50% 3 7% 20% 17% 3	1900
	11th to 20th	Day	51% 3 7% 20% 16% 4	1858
	21st to end	Day	50% 2 9% 16% 17% 6%	1570
March	1st to 10th	Day	56% 2 7% 14% 12% 7%	3138
	11th to 20th	Day	39% 2 6% 25% 20% 6%	3480
	21st to end	Day	46% 2 8% 30% 12% 2	3815
April	1st to 10th	Day	40% 3 11% 24% 19% 3	2238
	11th to 20th	Day	40% 2 8% 20% 24% 5%	2254
	21st to end	Day	40% 3 10% 29% 16% 2	2418
May	1st to 10th	Day	47% 3 11% 24% 13% 2	4120
	11th to 20th	Day	47% 4 13% 25% 11% 1	4085
	21st to end	Day	40% 4 12% 23% 20% 2	4489
June	1st to 10th	Day	40% 5% 16% 23% 14% 2	2470
	11th to 20th	Day	31% 6% 20% 26% 15% 2	2470
	21st to end	Day	36% 7% 18% 20% 14% 4	2470
July	1st to 10th	Day	40% 6% 22% 20% 10% 1	4055
	11th to 20th	Day	42% 5% 22% 22% 6% 2	4051
	21st to end	Day	62% 5% 12% 15% 5% 1	4324
August	1st to 10th	Day	34% 6% 16% 33% 11% 1	4091
	11th to 20th	Day	33% 5% 18% 27% 15% 2	3805
	21st to end	Day	32% 4 13% 35% 16% 2	4179
September	1st to 10th	Day	41% 5% 13% 19% 17% 6%	2153
	11th to 20th	Day	41% 5% 11% 22% 18% 3	2090
	21st to end	Day	37% 3 12% 22% 20% 6%	2090
October	1st to 10th	Day	24% 2 5% 23% 33% 13%	3480
	11th to 20th	Day	23% 1 5% 26% 32% 12%	3313
	21st to end	Day	31% 1 8% 26% 25% 8%	3278
November	1st to 10th	Day	33% 3 8% 23% 27% 6%	1699
	11th to 20th	Day	37% 2 6% 25% 24% 5%	1710
	21st to end	Day	41% 2 7% 26% 19% 4	1710
December	1st to 10th	Day	51% 3 6% 23% 14% 3	1710
	11th to 20th	Day	48% 3 8% 22% 18% 3	2150
	21st to end	Day	52% 3 9% 23% 11% 2	3124
January	1st to 10th	Night	48% 2 5% 26% 18% 2	4109
	11th to 20th	Night	49% 2 6% 20% 18% 5%	4120
	21st to end	Night	54% 2 6% 20% 17% 1	4404
February	1st to 10th	Night	45% 2 10% 23% 17% 3	2280
	11th to 20th	Night	51% 2 7% 20% 15% 5%	2219
	21st to end	Night	52% 3 6% 17% 17% 5%	1884
March	1st to 10th	Night	54% 2 9% 16% 15% 4	3715
	11th to 20th	Night	36% 2 8% 26% 18% 11%	3480
	21st to end	Night	46% 2 6% 26% 18% 2	3817
April	1st to 10th	Night	35% 3 11% 25% 23% 4	1957
	11th to 20th	Night	36% 3 8% 22% 24% 7%	1875
	21st to end	Night	35% 4 12% 30% 17% 2	1762
May	1st to 10th	Night	45% 3 13% 25% 13% 1	2840
	11th to 20th	Night	44% 4 14% 23% 14% 1	2813
	21st to end	Night	37% 4 13% 26% 18% 1	3087
June	1st to 10th	Night	39% 7% 14% 25% 13% 3	1710
	11th to 20th	Night	23% 6% 23% 30% 16% 2	1710
	21st to end	Night	32% 7% 17% 25% 13% 4	1710
July	1st to 10th	Night	40% 7% 21% 22% 8% 1	2795
	11th to 20th	Night	33% 4 23% 29% 7% 4	2786
	21st to end	Night	55% 8% 14% 15% 6% 1	2988
August	1st to 10th	Night	29% 5% 15% 36% 14% 1	2814
	11th to 20th	Night	30% 4 22% 28% 16% 1	3086
	21st to end	Night	27% 4 14% 36% 18% 1	3476
September	1st to 10th	Night	37% 5% 15% 21% 16% 6%	2006
	11th to 20th	Night	40% 5% 12% 20% 21% 1	2090
	21st to end	Night	35% 4 9% 23% 23% 6%	2090
October	1st to 10th	Night	21% 2 5% 25% 31% 16%	3480
	11th to 20th	Night	21% 1 5% 23% 34% 16%	3605
	21st to end	Night	27% 2 5% 28% 29% 10%	4267
November	1st to 10th	Night	33% 2 8% 23% 25% 8%	2452
	11th to 20th	Night	36% 2 6% 23% 26% 8%	2470
	21st to end	Night	41% 2 6% 25% 22% 4	2470
December	1st to 10th	Night	50% 3 8% 21% 15% 3	2470
	11th to 20th	Night	42% 2 6% 24% 24% 2	3044
	21st to end	Night	55% 3 7% 20% 14% 1	4532

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	24% 20% 27% 23% 5% 1	270
	11th to 20th	Day	26% 20% 31% 14% 6% 2	270
	21st to end	Day	22% 13% 41% 19% 4	297
February	1st to 10th	Day	24% 17% 34% 17% 7%	270
	11th to 20th	Day	35% 13% 34% 13% 4 1	270
	21st to end	Day	37% 18% 32% 10% 4	225
March	1st to 10th	Day	25% 16% 33% 18% 7% 1	275
	11th to 20th	Day	23% 14% 30% 25% 8%	460
	21st to end	Day	21% 11% 33% 27% 8%	506
April	1st to 10th	Day	17% 16% 23% 29% 12% 3	460
	11th to 20th	Day	18% 10% 31% 25% 15% 2	452
	21st to end	Day	17% 7% 31% 28% 13% 4	460
May	1st to 10th	Day	14% 10% 26% 27% 15% 7%	463
	11th to 20th	Day	14% 5% 22% 27% 21% 11%	487
	21st to end	Day	14% 5% 16% 25% 22% 19%	529
June	1st to 10th	Day	13% 4 14% 27% 27% 15%	490
	11th to 20th	Day	6% 3 11% 27% 30% 23%	490
	21st to end	Day	10% 3 11% 28% 27% 21%	490
July	1st to 10th	Day	10% 3 7% 22% 29% 28%	485
	11th to 20th	Day	11% 2 8% 23% 29% 27%	484
	21st to end	Day	11% 2 6% 23% 34% 24%	532
August	1st to 10th	Day	10% 3 8% 23% 35% 20%	486
	11th to 20th	Day	13% 3 8% 29% 34% 13%	479
	21st to end	Day	14% 2 6% 21% 34% 24%	539
September	1st to 10th	Day	11% 2 8% 26% 33% 19%	490
	11th to 20th	Day	15% 2 9% 23% 32% 18%	490
	21st to end	Day	17% 2 13% 23% 32% 12%	490
October	1st to 10th	Day	13% 4 18% 24% 29% 11%	490
	11th to 20th	Day	12% 9% 22% 29% 22% 5%	490
	21st to end	Day	18% 6% 21% 32% 20% 4	451
November	1st to 10th	Day	18% 5% 25% 30% 16% 5%	279
	11th to 20th	Day	13% 12% 33% 33% 8% 1	270
	21st to end	Day	14% 11% 34% 26% 14% 1	270
December	1st to 10th	Day	31% 9% 27% 24% 9% 1	270
	11th to 20th	Day	17% 16% 30% 25% 11% 1	270
	21st to end	Day	29% 13% 27% 22% 8%	297
January	1st to 10th	Night	24% 11% 36% 25% 5%	760
	11th to 20th	Night	23% 13% 31% 26% 6%	760
	21st to end	Night	21% 11% 34% 32% 2	836
February	1st to 10th	Night	20% 11% 33% 31% 5%	760
	11th to 20th	Night	26% 14% 33% 25% 2	743
	21st to end	Night	30% 12% 34% 23% 2	628
March	1st to 10th	Night	20% 11% 30% 34% 5%	760
	11th to 20th	Night	20% 10% 34% 29% 7% 1	760
	21st to end	Night	17% 11% 30% 34% 8% 1	836
April	1st to 10th	Night	15% 8% 31% 35% 10% 1	627
	11th to 20th	Night	16% 7% 29% 34% 13%	563
	21st to end	Night	12% 6% 26% 41% 12% 1	570
May	1st to 10th	Night	14% 4 25% 35% 20% 2	570
	11th to 20th	Night	14% 5% 18% 35% 23% 5%	561
	21st to end	Night	11% 2 12% 33% 36% 6%	617
June	1st to 10th	Night	11% 2 12% 34% 36% 5%	570
	11th to 20th	Night	5% 1 10% 35% 37% 11%	570
	21st to end	Night	6% 2 6% 35% 40% 10%	570
July	1st to 10th	Night	12% 3 6% 25% 43% 11%	555
	11th to 20th	Night	12% 2 5% 26% 43% 13%	552
	21st to end	Night	9% 2 7% 25% 46% 11%	624
August	1st to 10th	Night	6% 2 5% 29% 48% 11%	567
	11th to 20th	Night	12% 2 6% 34% 40% 6%	564
	21st to end	Night	12% 2 4 27% 45% 10%	627
September	1st to 10th	Night	10% 3 9% 29% 41% 8%	676
	11th to 20th	Night	15% 3 9% 27% 40% 6%	760
	21st to end	Night	14% 1 13% 34% 34% 3	760
October	1st to 10th	Night	12% 5% 15% 31% 29% 8%	760
	11th to 20th	Night	14% 5% 22% 36% 21% 2	760
	21st to end	Night	16% 5% 18% 42% 16% 3	836
November	1st to 10th	Night	14% 7% 19% 37% 20% 3	755
	11th to 20th	Night	15% 8% 31% 33% 12% 1	760
	21st to end	Night	19% 9% 26% 33% 12% 1	760
December	1st to 10th	Night	24% 12% 26% 31% 7%	760
	11th to 20th	Night	20% 8% 28% 36% 8%	760
	21st to end	Night	27% 9% 25% 33% 6%	836

Page generated at 2024-11-01 22:47:32. Version ac07

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