Lafayette
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lafayette 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	11% 7% 3 7% 5% 5% 5% 5% 7% 8% 37%	100728
	Night	12% 6% 2 6% 4 4 4 4 6% 8% 44%	98411
Transparency	Day	40% 8% 12% 18% 16% 6%	104376
	Night	35% 7% 13% 18% 17% 9%	102904
Seeing	Day	12% 6% 18% 23% 25% 16%	14872
	Night	13% 6% 19% 32% 25% 5%	24597

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	18% 9% 3 6% 4 3 4 3 6% 7% 36%	2847
	11th to 20th	Day	13% 6% 2 5% 3 3 2 2 4 5% 55%	2850
	21st to end	Day	23% 9% 3 7% 4 4 4 3 4 5% 33%	3135
February	1st to 10th	Day	17% 9% 4 7% 4 4 4 3 5% 6% 36%	1843
	11th to 20th	Day	18% 9% 2 6% 3 4 4 3 5% 6% 38%	1848
	21st to end	Day	16% 11% 3 7% 4 4 4 3 5% 6% 36%	1672
March	1st to 10th	Day	23% 10% 3 8% 5% 4 4 4 6% 7% 26%	3436
	11th to 20th	Day	15% 7% 3 8% 6% 6% 6% 5% 6% 9% 30%	3480
	21st to end	Day	12% 6% 2 7% 5% 5% 4 4 6% 8% 42%	3814
April	1st to 10th	Day	11% 7% 2 6% 5% 5% 6% 4 6% 7% 40%	2271
	11th to 20th	Day	13% 7% 3 6% 5% 4 5% 4 7% 8% 37%	2254
	21st to end	Day	9% 5% 2 5% 5% 6% 5% 5% 7% 9% 42%	2280
May	1st to 10th	Day	11% 7% 3 9% 7% 6% 6% 5% 6% 7% 33%	3765
	11th to 20th	Day	10% 7% 3 6% 4 5% 5% 3 6% 7% 44%	3764
	21st to end	Day	6% 5% 2 6% 6% 6% 6% 5% 9% 10% 39%	4211
June	1st to 10th	Day	6% 6% 3 9% 7% 7% 6% 5% 7% 9% 35%	2470
	11th to 20th	Day	5% 5% 3 7% 7% 8% 8% 7% 8% 9% 34%	2470
	21st to end	Day	7% 6% 3 8% 9% 8% 9% 7% 10% 9% 24%	2470
July	1st to 10th	Day	7% 6% 3 9% 8% 8% 9% 7% 10% 11% 21%	4120
	11th to 20th	Day	6% 7% 3 9% 8% 8% 9% 8% 10% 11% 22%	4120
	21st to end	Day	12% 10% 3 11% 6% 7% 7% 5% 7% 9% 22%	4444
August	1st to 10th	Day	3 3 1 4 4 4 5% 4 7% 11% 54%	3785
	11th to 20th	Day	5% 4 2 6% 5% 6% 7% 6% 10% 14% 36%	3729
	21st to end	Day	11% 7% 3 8% 7% 7% 6% 5% 6% 7% 33%	4180
September	1st to 10th	Day	11% 5% 2 7% 6% 5% 6% 5% 8% 9% 34%	2280
	11th to 20th	Day	12% 8% 2 7% 5% 6% 5% 4 7% 7% 37%	2280
	21st to end	Day	10% 5% 2 7% 5% 4 5% 4 6% 6% 47%	2010
October	1st to 10th	Day	7% 4 2 5% 4 4 4 3 5% 6% 56%	1900
	11th to 20th	Day	9% 4 2 7% 4 3 4 3 5% 6% 54%	1900
	21st to end	Day	11% 4 1 5% 4 3 4 3 4 6% 53%	2090
November	1st to 10th	Day	9% 6% 2 5% 4 4 4 4 5% 7% 50%	1928
	11th to 20th	Day	11% 6% 2 6% 4 4 2 3 5% 5% 51%	1900
	21st to end	Day	14% 6% 2 6% 4 4 4 3 6% 5% 45%	1900
December	1st to 10th	Day	15% 7% 2 5% 4 4 5% 3 6% 7% 40%	1900
	11th to 20th	Day	15% 9% 3 7% 4 4 4 4 6% 7% 37%	2247
	21st to end	Day	16% 7% 3 7% 5% 4 5% 4 5% 7% 38%	3135
January	1st to 10th	Night	16% 6% 3 6% 4 4 4 3 5% 6% 44%	4108
	11th to 20th	Night	13% 6% 2 5% 3 3 3 3 4 5% 52%	4120
	21st to end	Night	24% 8% 3 6% 4 3 3 3 4 7% 37%	4532
February	1st to 10th	Night	15% 9% 3 7% 4 4 4 3 5% 6% 41%	2334
	11th to 20th	Night	19% 8% 2 5% 3 3 4 3 5% 5% 43%	2218
	21st to end	Night	19% 9% 3 6% 3 3 3 4 5% 6% 39%	1797
March	1st to 10th	Night	23% 11% 3 8% 4 3 4 3 5% 6% 30%	3419
	11th to 20th	Night	18% 9% 3 7% 5% 4 5% 4 5% 7% 34%	3480
	21st to end	Night	13% 7% 2 5% 4 3 4 4 6% 7% 45%	3817
April	1st to 10th	Night	13% 6% 2 5% 5% 4 4 4 7% 9% 43%	1907
	11th to 20th	Night	13% 6% 2 6% 4 4 4 3 4 7% 47%	1875
	21st to end	Night	7% 6% 2 5% 4 4 4 4 6% 7% 52%	1900
May	1st to 10th	Night	16% 7% 3 7% 5% 5% 4 4 6% 8% 35%	3130
	11th to 20th	Night	14% 5% 2 7% 4 4 4 4 6% 8% 42%	3129
	21st to end	Night	8% 5% 2 6% 4 4 5% 4 7% 12% 43%	3342
June	1st to 10th	Night	5% 4 2 5% 4 4 6% 5% 7% 10% 48%	1710
	11th to 20th	Night	4 4 1 4 5% 5% 5% 5% 7% 11% 49%	1710
	21st to end	Night	6% 6% 2 6% 6% 6% 6% 4 8% 11% 39%	1710
July	1st to 10th	Night	4 5% 2 7% 5% 6% 6% 6% 9% 14% 36%	2850
	11th to 20th	Night	4 3 2 6% 5% 6% 6% 6% 9% 13% 40%	2850
	21st to end	Night	6% 6% 3 8% 6% 6% 5% 5% 8% 13% 34%	3114
August	1st to 10th	Night	2 2 1 3 3 3 4 4 6% 11% 61%	3144
	11th to 20th	Night	2 2 1 4 3 4 5% 4 9% 14% 52%	3100
	21st to end	Night	6% 6% 3 7% 6% 5% 5% 4 8% 9% 41%	3476
September	1st to 10th	Night	8% 5% 2 6% 5% 5% 5% 5% 8% 11% 42%	1900
	11th to 20th	Night	8% 8% 3 6% 5% 5% 6% 4 8% 8% 39%	1900
	21st to end	Night	8% 5% 2 5% 3 3 4 4 6% 8% 53%	2143
October	1st to 10th	Night	5% 4 2 5% 3 3 4 3 5% 7% 59%	2280
	11th to 20th	Night	7% 4 1 4 3 3 3 3 5% 6% 59%	2280
	21st to end	Night	9% 5% 2 4 3 3 3 2 5% 6% 58%	2508
November	1st to 10th	Night	8% 6% 2 5% 4 3 3 3 4 7% 55%	2311
	11th to 20th	Night	12% 4 2 5% 4 3 3 3 4 6% 54%	2280
	21st to end	Night	15% 6% 2 5% 3 4 3 3 5% 6% 47%	2280
December	1st to 10th	Night	15% 9% 3 5% 4 3 4 3 4 6% 45%	2280
	11th to 20th	Night	12% 9% 2 6% 4 4 4 4 6% 6% 43%	2945
	21st to end	Night	18% 9% 3 7% 4 4 3 3 4 6% 40%	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	45% 6% 5% 16% 19% 8%	2848
	11th to 20th	Day	33% 4 5% 21% 29% 9%	2850
	21st to end	Day	53% 4 5% 13% 18% 8%	3135
February	1st to 10th	Day	48% 5% 8% 13% 17% 9%	1843
	11th to 20th	Day	46% 6% 6% 15% 17% 10%	1858
	21st to end	Day	48% 5% 8% 16% 17% 7%	1672
March	1st to 10th	Day	55% 7% 11% 13% 10% 4	3436
	11th to 20th	Day	47% 8% 11% 17% 13% 4	3480
	21st to end	Day	37% 6% 11% 17% 22% 6%	3814
April	1st to 10th	Day	40% 7% 11% 17% 17% 9%	2271
	11th to 20th	Day	41% 7% 10% 18% 15% 8%	2254
	21st to end	Day	35% 8% 12% 19% 23% 4	2280
May	1st to 10th	Day	44% 9% 12% 21% 10% 4	3800
	11th to 20th	Day	37% 7% 9% 19% 24% 4	3768
	21st to end	Day	33% 10% 14% 32% 10% 1	4223
June	1st to 10th	Day	42% 9% 14% 21% 13% 1	2470
	11th to 20th	Day	41% 10% 14% 21% 13% 1	2470
	21st to end	Day	48% 14% 16% 16% 6%	2470
July	1st to 10th	Day	48% 15% 21% 15% 1	4056
	11th to 20th	Day	48% 15% 25% 10% 2	4051
	21st to end	Day	55% 12% 15% 14% 3	4304
August	1st to 10th	Day	22% 9% 16% 33% 21%	3773
	11th to 20th	Day	33% 12% 24% 26% 4 1	3765
	21st to end	Day	49% 8% 13% 14% 14% 2	4179
September	1st to 10th	Day	42% 12% 15% 17% 10% 4	2280
	11th to 20th	Day	44% 8% 14% 15% 14% 6%	2280
	21st to end	Day	36% 6% 12% 20% 16% 10%	2010
October	1st to 10th	Day	25% 4 6% 12% 23% 31%	3160
	11th to 20th	Day	20% 3 5% 19% 28% 25%	3140
	21st to end	Day	25% 4 4 11% 39% 17%	3428
November	1st to 10th	Day	32% 5% 10% 19% 25% 10%	1928
	11th to 20th	Day	34% 4 6% 17% 27% 12%	1900
	21st to end	Day	40% 5% 8% 17% 22% 9%	1900
December	1st to 10th	Day	41% 6% 9% 20% 16% 8%	1900
	11th to 20th	Day	45% 5% 7% 15% 19% 9%	2245
	21st to end	Day	43% 6% 8% 15% 24% 4	3135
January	1st to 10th	Night	40% 5% 7% 15% 25% 8%	4108
	11th to 20th	Night	35% 4 6% 18% 25% 12%	4120
	21st to end	Night	48% 4 5% 17% 17% 9%	4532
February	1st to 10th	Night	45% 3 7% 16% 19% 10%	2334
	11th to 20th	Night	43% 5% 7% 17% 17% 12%	2219
	21st to end	Night	46% 5% 10% 13% 15% 11%	1797
March	1st to 10th	Night	54% 6% 11% 12% 11% 6%	3419
	11th to 20th	Night	48% 7% 10% 16% 14% 4	3480
	21st to end	Night	37% 7% 11% 19% 20% 7%	3817
April	1st to 10th	Night	37% 7% 12% 17% 17% 10%	1907
	11th to 20th	Night	37% 6% 11% 19% 16% 12%	1875
	21st to end	Night	30% 7% 10% 22% 24% 7%	1900
May	1st to 10th	Night	43% 10% 13% 18% 11% 5%	3160
	11th to 20th	Night	38% 7% 12% 19% 23% 2	3130
	21st to end	Night	30% 10% 21% 27% 12% 1	3351
June	1st to 10th	Night	27% 12% 20% 24% 17% 1	1710
	11th to 20th	Night	27% 10% 19% 27% 14% 2	1710
	21st to end	Night	37% 10% 22% 23% 8% 1	1710
July	1st to 10th	Night	34% 15% 32% 15% 3	2805
	11th to 20th	Night	31% 15% 38% 13% 3	2796
	21st to end	Night	39% 17% 22% 17% 5%	3015
August	1st to 10th	Night	17% 8% 20% 34% 22%	3132
	11th to 20th	Night	19% 10% 34% 31% 4	3130
	21st to end	Night	38% 11% 17% 19% 14% 2	3476
September	1st to 10th	Night	34% 10% 20% 21% 9% 6%	1900
	11th to 20th	Night	38% 11% 17% 16% 14% 5%	1900
	21st to end	Night	29% 8% 13% 23% 16% 11%	2143
October	1st to 10th	Night	24% 4 9% 14% 19% 31%	3800
	11th to 20th	Night	17% 3 5% 21% 29% 26%	3779
	21st to end	Night	20% 3 6% 12% 36% 24%	4120
November	1st to 10th	Night	30% 5% 9% 19% 25% 12%	2311
	11th to 20th	Night	32% 4 8% 17% 25% 14%	2280
	21st to end	Night	38% 5% 7% 19% 21% 10%	2280
December	1st to 10th	Night	41% 5% 8% 21% 18% 8%	2280
	11th to 20th	Night	41% 5% 8% 13% 20% 13%	2946
	21st to end	Night	46% 5% 8% 14% 19% 8%	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	20% 14% 37% 18% 7% 3	270
	11th to 20th	Day	13% 16% 35% 26% 9% 1	270
	21st to end	Day	24% 12% 40% 18% 6%	297
February	1st to 10th	Day	23% 12% 29% 27% 8%	270
	11th to 20th	Day	24% 17% 29% 21% 10%	270
	21st to end	Day	17% 19% 42% 16% 5%	225
March	1st to 10th	Day	20% 15% 32% 25% 7% 1	270
	11th to 20th	Day	20% 13% 36% 24% 7% 1	270
	21st to end	Day	13% 14% 38% 23% 8% 3	297
April	1st to 10th	Day	15% 13% 30% 28% 13% 1	451
	11th to 20th	Day	18% 11% 28% 25% 16% 2	452
	21st to end	Day	10% 7% 27% 33% 20% 3	460
May	1st to 10th	Day	12% 6% 24% 34% 20% 4	463
	11th to 20th	Day	10% 3 21% 30% 27% 9%	487
	21st to end	Day	7% 2 15% 30% 32% 14%	572
June	1st to 10th	Day	7% 2 12% 29% 32% 18%	680
	11th to 20th	Day	7% 1 11% 28% 35% 17%	680
	21st to end	Day	9% 2 8% 25% 30% 27%	680
July	1st to 10th	Day	8% 3 4 18% 35% 31%	671
	11th to 20th	Day	7% 1 4 16% 36% 36%	668
	21st to end	Day	9% 2 5% 16% 37% 31%	730
August	1st to 10th	Day	3 1 3 12% 36% 45%	486
	11th to 20th	Day	7% 1 4 8% 30% 50%	479
	21st to end	Day	12% 2 6% 16% 31% 33%	539
September	1st to 10th	Day	12% 2 7% 18% 35% 27%	490
	11th to 20th	Day	10% 4 6% 19% 37% 24%	490
	21st to end	Day	10% 3 8% 22% 38% 18%	357
October	1st to 10th	Day	8% 3 17% 39% 25% 9%	300
	11th to 20th	Day	6% 5% 18% 34% 25% 12%	300
	21st to end	Day	15% 9% 19% 27% 23% 6%	330
November	1st to 10th	Day	12% 5% 20% 32% 25% 6%	291
	11th to 20th	Day	16% 11% 23% 29% 19% 3	270
	21st to end	Day	19% 10% 30% 26% 13% 3	270
December	1st to 10th	Day	20% 7% 27% 27% 13% 6%	270
	11th to 20th	Day	21% 12% 31% 25% 10%	270
	21st to end	Day	22% 10% 32% 23% 12% 1	297
January	1st to 10th	Night	19% 9% 33% 31% 9%	950
	11th to 20th	Night	18% 9% 30% 33% 10%	950
	21st to end	Night	21% 9% 32% 31% 7%	1045
February	1st to 10th	Night	19% 11% 30% 35% 6%	814
	11th to 20th	Night	23% 10% 27% 34% 7%	743
	21st to end	Night	24% 13% 31% 28% 4	541
March	1st to 10th	Night	18% 9% 28% 37% 8%	570
	11th to 20th	Night	16% 8% 29% 37% 9%	570
	21st to end	Night	15% 6% 32% 35% 12%	627
April	1st to 10th	Night	15% 9% 31% 34% 11% 1	570
	11th to 20th	Night	13% 10% 30% 32% 15% 1	563
	21st to end	Night	8% 6% 27% 45% 14% 1	570
May	1st to 10th	Night	11% 5% 20% 48% 15% 1	570
	11th to 20th	Night	10% 3 17% 47% 21% 2	561
	21st to end	Night	7% 2 12% 38% 35% 5%	617
June	1st to 10th	Night	4 2 7% 36% 43% 8%	570
	11th to 20th	Night	4 1 6% 31% 49% 8%	570
	21st to end	Night	7% 2 5% 24% 45% 16%	570
July	1st to 10th	Night	5% 1 5% 16% 56% 17%	555
	11th to 20th	Night	4 1 3 11% 57% 25%	552
	21st to end	Night	5% 1 3 17% 55% 19%	624
August	1st to 10th	Night	4 1 2 14% 57% 23%	567
	11th to 20th	Night	4 1 1 13% 55% 27%	564
	21st to end	Night	6% 2 4 18% 50% 20%	627
September	1st to 10th	Night	8% 1 5% 18% 50% 18%	570
	11th to 20th	Night	12% 2 5% 22% 48% 10%	570
	21st to end	Night	10% 2 6% 28% 47% 7%	686
October	1st to 10th	Night	6% 2 12% 38% 38% 5%	760
	11th to 20th	Night	8% 4 18% 39% 28% 3	760
	21st to end	Night	11% 6% 18% 38% 25% 2	836
November	1st to 10th	Night	10% 4 18% 41% 25% 2	771
	11th to 20th	Night	13% 6% 22% 41% 17% 1	760
	21st to end	Night	16% 6% 28% 35% 14% 1	760
December	1st to 10th	Night	18% 9% 23% 34% 16%	760
	11th to 20th	Night	18% 8% 29% 34% 12%	859
	21st to end	Night	23% 9% 28% 30% 10%	1045

Page generated at 2024-11-05 07:15:50. Version ac07

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