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 2024-01-12.

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% 6% 3 6% 6% 4 6% 6% 6% 8% 38%	75069
	Night	11% 6% 2 5% 5% 3 4 5% 6% 8% 47%	74667
Transparency	Day	41% 8% 12% 18% 16% 6%	74796
	Night	35% 7% 13% 19% 17% 8%	74461
Seeing	Day	12% 6% 17% 23% 25% 17%	13732
	Night	13% 5% 19% 32% 26% 6%	23584

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% 7% 3 5% 5% 3 5% 5% 5% 7% 39%	1707
	11th to 20th	Day	15% 8% 3 6% 4 3 3 3 5% 6% 45%	1634
	21st to end	Day	19% 8% 3 5% 5% 3 4 3 3 5% 42%	1782
February	1st to 10th	Day	17% 8% 4 6% 5% 3 4 4 5% 7% 36%	1746
	11th to 20th	Day	18% 9% 3 6% 4 3 5% 4 5% 6% 38%	1748
	21st to end	Day	17% 11% 4 7% 5% 2 5% 4 5% 6% 35%	1576
March	1st to 10th	Day	16% 8% 4 6% 5% 2 4 4 5% 7% 39%	1980
	11th to 20th	Day	15% 7% 3 7% 5% 4 5% 5% 5% 8% 36%	1980
	21st to end	Day	11% 6% 3 6% 4 3 4 5% 6% 9% 44%	2178
April	1st to 10th	Day	11% 6% 3 5% 5% 4 6% 6% 7% 7% 41%	2151
	11th to 20th	Day	14% 6% 3 5% 5% 3 5% 5% 7% 8% 38%	2134
	21st to end	Day	9% 5% 3 4 5% 5% 6% 6% 7% 8% 42%	2160
May	1st to 10th	Day	8% 5% 3 7% 6% 4 5% 5% 6% 8% 44%	2160
	11th to 20th	Day	8% 6% 3 5% 5% 3 6% 5% 6% 8% 44%	2124
	21st to end	Day	7% 5% 3 6% 7% 5% 7% 6% 8% 10% 36%	2377
June	1st to 10th	Day	6% 5% 3 8% 8% 5% 6% 7% 7% 9% 35%	2340
	11th to 20th	Day	5% 4 3 7% 9% 6% 8% 8% 8% 10% 33%	2340
	21st to end	Day	7% 6% 3 7% 10% 5% 10% 9% 10% 9% 23%	2340
July	1st to 10th	Day	10% 6% 4 6% 8% 5% 9% 9% 9% 10% 24%	2340
	11th to 20th	Day	8% 6% 4 7% 8% 5% 9% 8% 9% 10% 26%	2340
	21st to end	Day	9% 5% 3 8% 7% 5% 7% 8% 8% 10% 28%	2538
August	1st to 10th	Day	5% 4 2 5% 8% 4 8% 8% 10% 13% 32%	2148
	11th to 20th	Day	8% 6% 3 7% 7% 5% 8% 8% 8% 11% 29%	2125
	21st to end	Day	10% 6% 3 7% 9% 6% 8% 7% 7% 8% 31%	2376
September	1st to 10th	Day	10% 5% 3 6% 7% 4 7% 7% 8% 9% 35%	2160
	11th to 20th	Day	12% 7% 2 6% 6% 4 6% 5% 7% 7% 37%	2160
	21st to end	Day	10% 5% 2 6% 5% 3 5% 5% 6% 6% 45%	1905
October	1st to 10th	Day	7% 4 2 4 5% 3 4 5% 5% 7% 56%	1800
	11th to 20th	Day	9% 4 2 6% 5% 3 4 5% 5% 7% 52%	1800
	21st to end	Day	12% 4 1 5% 5% 2 3 4 4 6% 53%	1980
November	1st to 10th	Day	9% 5% 2 4 4 3 4 5% 5% 7% 51%	1858
	11th to 20th	Day	11% 6% 2 5% 5% 3 3 3 5% 6% 52%	1900
	21st to end	Day	14% 6% 3 5% 5% 3 5% 4 5% 5% 45%	1900
December	1st to 10th	Day	16% 6% 3 5% 5% 3 5% 4 6% 8% 40%	1900
	11th to 20th	Day	15% 9% 3 6% 5% 3 4 5% 6% 7% 37%	2247
	21st to end	Day	16% 7% 3 6% 5% 3 5% 5% 5% 7% 39%	3135
January	1st to 10th	Night	17% 5% 2 5% 4 2 4 4 5% 7% 44%	2458
	11th to 20th	Night	15% 7% 2 4 4 2 4 4 5% 5% 47%	2366
	21st to end	Night	17% 8% 3 5% 5% 2 4 4 5% 5% 43%	2574
February	1st to 10th	Night	16% 8% 3 6% 5% 3 4 3 4 6% 41%	2211
	11th to 20th	Night	19% 7% 3 5% 4 2 3 4 5% 5% 43%	2098
	21st to end	Night	20% 8% 3 6% 4 2 4 4 5% 6% 38%	1694
March	1st to 10th	Night	14% 7% 2 6% 5% 3 4 4 5% 7% 44%	1980
	11th to 20th	Night	14% 8% 3 6% 5% 3 4 6% 5% 7% 41%	1980
	21st to end	Night	11% 5% 2 4 4 2 3 4 6% 8% 51%	2178
April	1st to 10th	Night	12% 6% 3 4 5% 3 4 4 6% 9% 43%	1807
	11th to 20th	Night	13% 6% 3 5% 4 2 4 4 4 7% 48%	1775
	21st to end	Night	7% 5% 2 5% 4 3 4 5% 6% 7% 53%	1800
May	1st to 10th	Night	9% 5% 2 4 5% 3 3 5% 5% 9% 50%	1800
	11th to 20th	Night	7% 4 1 4 5% 3 5% 4 7% 10% 49%	1769
	21st to end	Night	7% 4 2 3 4 3 5% 5% 6% 11% 51%	1893
June	1st to 10th	Night	5% 4 2 4 5% 3 6% 6% 7% 11% 48%	1620
	11th to 20th	Night	4 2 2 3 5% 4 6% 6% 7% 12% 49%	1620
	21st to end	Night	7% 5% 3 5% 6% 5% 7% 5% 8% 11% 39%	1620
July	1st to 10th	Night	5% 4 2 5% 4 3 6% 7% 8% 12% 44%	1620
	11th to 20th	Night	5% 3 2 5% 6% 3 6% 6% 8% 13% 44%	1620
	21st to end	Night	4 4 3 5% 6% 3 5% 6% 8% 13% 43%	1776
August	1st to 10th	Night	4 2 1 3 4 3 4 6% 7% 13% 53%	1790
	11th to 20th	Night	4 2 2 5% 5% 5% 6% 7% 10% 14% 41%	1776
	21st to end	Night	7% 4 2 5% 7% 4 6% 6% 10% 11% 39%	1980
September	1st to 10th	Night	7% 4 2 4 5% 4 5% 6% 8% 11% 44%	1800
	11th to 20th	Night	7% 7% 4 6% 6% 3 5% 6% 8% 8% 40%	1800
	21st to end	Night	8% 5% 2 5% 3 2 4 5% 5% 8% 53%	2029
October	1st to 10th	Night	5% 4 2 4 4 3 4 5% 5% 8% 59%	2160
	11th to 20th	Night	8% 4 2 3 4 3 3 4 5% 6% 58%	2160
	21st to end	Night	10% 5% 2 4 4 2 3 3 5% 6% 57%	2376
November	1st to 10th	Night	8% 5% 2 4 5% 2 3 4 4 7% 56%	2220
	11th to 20th	Night	12% 4 2 5% 4 2 4 3 4 6% 54%	2280
	21st to end	Night	15% 6% 2 4 4 3 4 4 5% 6% 48%	2280
December	1st to 10th	Night	15% 8% 3 5% 4 2 4 3 4 6% 46%	2280
	11th to 20th	Night	12% 8% 3 6% 5% 3 5% 4 6% 6% 43%	2945
	21st to end	Night	18% 9% 3 6% 5% 3 3 4 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	44% 5% 6% 18% 19% 8%	1708
	11th to 20th	Day	41% 3 6% 17% 24% 8%	1634
	21st to end	Day	46% 4 6% 15% 18% 12%	1782
February	1st to 10th	Day	48% 5% 8% 13% 17% 9%	1746
	11th to 20th	Day	47% 6% 6% 15% 16% 9%	1758
	21st to end	Day	49% 5% 8% 16% 16% 6%	1576
March	1st to 10th	Day	44% 5% 9% 18% 17% 7%	1980
	11th to 20th	Day	46% 6% 11% 11% 20% 6%	1980
	21st to end	Day	35% 6% 11% 22% 20% 5%	2178
April	1st to 10th	Day	39% 7% 11% 18% 17% 8%	2151
	11th to 20th	Day	41% 7% 10% 19% 15% 8%	2134
	21st to end	Day	35% 8% 11% 19% 23% 4	2160
May	1st to 10th	Day	36% 7% 11% 23% 17% 7%	2160
	11th to 20th	Day	35% 8% 11% 24% 18% 3	2128
	21st to end	Day	37% 10% 16% 23% 13% 1	2377
June	1st to 10th	Day	43% 9% 14% 21% 13% 1	2340
	11th to 20th	Day	41% 10% 14% 21% 12% 1	2340
	21st to end	Day	50% 15% 14% 16% 6%	2340
July	1st to 10th	Day	47% 15% 17% 17% 3	2276
	11th to 20th	Day	47% 13% 19% 16% 4	2271
	21st to end	Day	44% 14% 19% 16% 5% 1	2397
August	1st to 10th	Day	36% 15% 24% 19% 6%	2136
	11th to 20th	Day	44% 14% 19% 17% 4 1	2125
	21st to end	Day	48% 11% 16% 15% 8% 2	2376
September	1st to 10th	Day	40% 12% 15% 18% 10% 4	2160
	11th to 20th	Day	44% 8% 14% 14% 14% 5%	2160
	21st to end	Day	37% 6% 12% 20% 17% 8%	1905
October	1st to 10th	Day	28% 5% 10% 20% 23% 13%	1800
	11th to 20th	Day	31% 5% 7% 17% 26% 14%	1800
	21st to end	Day	32% 5% 6% 16% 25% 16%	1980
November	1st to 10th	Day	32% 5% 9% 19% 25% 10%	1858
	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	39% 5% 8% 15% 24% 9%	2458
	11th to 20th	Night	39% 5% 6% 18% 20% 13%	2366
	21st to end	Night	44% 4 6% 15% 20% 12%	2574
February	1st to 10th	Night	45% 3 7% 16% 18% 10%	2211
	11th to 20th	Night	42% 5% 8% 17% 17% 11%	2099
	21st to end	Night	47% 6% 10% 12% 14% 11%	1694
March	1st to 10th	Night	39% 5% 12% 16% 18% 10%	1980
	11th to 20th	Night	41% 7% 13% 14% 18% 7%	1980
	21st to end	Night	31% 6% 12% 22% 21% 8%	2178
April	1st to 10th	Night	36% 8% 12% 18% 17% 10%	1807
	11th to 20th	Night	37% 6% 11% 19% 16% 12%	1775
	21st to end	Night	30% 7% 10% 22% 24% 7%	1800
May	1st to 10th	Night	32% 6% 13% 25% 17% 8%	1800
	11th to 20th	Night	28% 8% 15% 24% 23% 2	1770
	21st to end	Night	26% 8% 20% 28% 16% 1	1894
June	1st to 10th	Night	26% 13% 20% 24% 17% 1	1620
	11th to 20th	Night	26% 10% 19% 28% 14% 2	1620
	21st to end	Night	37% 10% 21% 23% 7% 1	1620
July	1st to 10th	Night	30% 15% 28% 21% 6%	1575
	11th to 20th	Night	28% 15% 30% 21% 6%	1566
	21st to end	Night	28% 15% 30% 20% 8%	1677
August	1st to 10th	Night	22% 12% 32% 26% 8%	1778
	11th to 20th	Night	28% 14% 29% 23% 5% 1	1776
	21st to end	Night	36% 13% 22% 19% 8% 3	1980
September	1st to 10th	Night	32% 10% 20% 22% 9% 6%	1800
	11th to 20th	Night	37% 11% 18% 16% 14% 5%	1800
	21st to end	Night	29% 8% 13% 23% 16% 10%	2029
October	1st to 10th	Night	23% 6% 13% 23% 21% 14%	2160
	11th to 20th	Night	26% 6% 8% 21% 24% 16%	2160
	21st to end	Night	29% 4 8% 16% 24% 20%	2376
November	1st to 10th	Night	29% 5% 9% 19% 26% 12%	2220
	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	14% 14% 35% 26% 9% 2	245
	21st to end	Day	23% 11% 42% 17% 6%	264
February	1st to 10th	Day	23% 12% 29% 28% 8%	240
	11th to 20th	Day	24% 17% 28% 20% 11%	240
	21st to end	Day	19% 19% 40% 16% 6%	198
March	1st to 10th	Day	18% 16% 33% 25% 8% 1	240
	11th to 20th	Day	22% 11% 38% 21% 8% 1	240
	21st to end	Day	13% 16% 34% 25% 9% 3	264
April	1st to 10th	Day	14% 11% 30% 30% 13% 1	411
	11th to 20th	Day	19% 9% 27% 25% 17% 2	412
	21st to end	Day	11% 7% 26% 35% 20% 2	420
May	1st to 10th	Day	11% 5% 23% 35% 21% 4	423
	11th to 20th	Day	9% 3 19% 30% 28% 10%	447
	21st to end	Day	8% 2 14% 28% 34% 15%	525
June	1st to 10th	Day	7% 3 11% 29% 32% 19%	630
	11th to 20th	Day	7% 1 11% 27% 37% 18%	630
	21st to end	Day	9% 2 8% 24% 30% 27%	630
July	1st to 10th	Day	9% 3 4 17% 35% 32%	621
	11th to 20th	Day	7% 1 4 15% 36% 37%	618
	21st to end	Day	9% 2 4 15% 37% 33%	676
August	1st to 10th	Day	3 1 3 9% 35% 48%	446
	11th to 20th	Day	8% 1 4 7% 31% 49%	439
	21st to end	Day	12% 2 6% 14% 31% 35%	495
September	1st to 10th	Day	10% 1 6% 17% 38% 29%	450
	11th to 20th	Day	10% 4 5% 19% 38% 25%	450
	21st to end	Day	11% 3 7% 22% 38% 20%	324
October	1st to 10th	Day	8% 3 14% 37% 27% 10%	270
	11th to 20th	Day	7% 4 17% 33% 26% 14%	270
	21st to end	Day	17% 9% 21% 26% 22% 6%	297
November	1st to 10th	Day	13% 4 18% 31% 27% 6%	270
	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% 8% 30% 34% 10%	910
	21st to end	Night	21% 9% 32% 31% 7%	990
February	1st to 10th	Night	20% 10% 30% 35% 5%	771
	11th to 20th	Night	22% 10% 27% 33% 7%	703
	21st to end	Night	24% 13% 31% 28% 4	510
March	1st to 10th	Night	18% 8% 29% 37% 9%	540
	11th to 20th	Night	16% 8% 29% 37% 10%	540
	21st to end	Night	14% 6% 31% 36% 13%	594
April	1st to 10th	Night	14% 8% 31% 34% 11% 1	540
	11th to 20th	Night	14% 9% 30% 32% 15% 1	533
	21st to end	Night	8% 5% 26% 46% 14% 1	540
May	1st to 10th	Night	10% 4 20% 48% 15% 1	540
	11th to 20th	Night	9% 2 17% 48% 22% 2	531
	21st to end	Night	7% 2 10% 38% 38% 6%	584
June	1st to 10th	Night	4 2 6% 36% 43% 9%	540
	11th to 20th	Night	3 1 6% 31% 50% 9%	540
	21st to end	Night	7% 2 5% 24% 46% 16%	540
July	1st to 10th	Night	5% 1 5% 16% 57% 17%	525
	11th to 20th	Night	4 1 3 11% 57% 25%	522
	21st to end	Night	4 1 3 17% 55% 20%	591
August	1st to 10th	Night	4 1 1 13% 56% 25%	537
	11th to 20th	Night	4 1 1 12% 55% 27%	534
	21st to end	Night	7% 2 4 17% 50% 21%	594
September	1st to 10th	Night	7% 1 4 18% 51% 19%	540
	11th to 20th	Night	11% 2 5% 22% 49% 10%	540
	21st to end	Night	10% 2 5% 28% 48% 7%	649
October	1st to 10th	Night	6% 1 10% 38% 40% 5%	720
	11th to 20th	Night	8% 4 17% 39% 28% 3	720
	21st to end	Night	12% 6% 17% 38% 25% 2	792
November	1st to 10th	Night	10% 4 17% 41% 26% 2	740
	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 2024-01-09 15:24:27. Version ac07

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