Vincennes
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Vincennes clear sky chart from 2005-11-06 to 2024-07-31.

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% 8% 3 7% 5% 4 4 4 5% 7% 39%	89755
	Night	15% 8% 3 6% 4 4 4 3 5% 6% 40%	90054
Transparency	Day	42% 7% 11% 23% 14% 2	89510
	Night	43% 6% 11% 22% 15% 3	89905
Seeing	Day	16% 8% 24% 25% 19% 9%	15180
	Night	17% 7% 26% 32% 16% 2	24996

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	14% 14% 8% 10% 4 4 4 4 4 5% 30%	2527
	11th to 20th	Day	17% 10% 4 10% 7% 7% 5% 4 5% 5% 27%	2530
	21st to end	Day	26% 17% 5% 8% 4 3 3 2 4 5% 23%	2998
February	1st to 10th	Day	17% 12% 4 8% 5% 4 3 2 5% 6% 33%	1900
	11th to 20th	Day	15% 11% 3 8% 5% 4 4 3 5% 6% 34%	1848
	21st to end	Day	17% 10% 4 9% 5% 4 4 3 4 6% 34%	1570
March	1st to 10th	Day	23% 13% 4 7% 4 3 3 2 3 4 34%	3120
	11th to 20th	Day	14% 7% 2 6% 4 3 3 3 5% 8% 45%	3251
	21st to end	Day	14% 9% 3 7% 6% 5% 5% 4 5% 8% 34%	4155
April	1st to 10th	Day	14% 8% 3 6% 5% 4 4 3 5% 8% 40%	2280
	11th to 20th	Day	16% 8% 2 6% 4 4 4 3 5% 6% 40%	2254
	21st to end	Day	19% 6% 3 6% 5% 4 4 3 5% 7% 39%	2337
May	1st to 10th	Day	17% 7% 3 7% 5% 5% 5% 5% 7% 10% 30%	4082
	11th to 20th	Day	19% 7% 2 6% 5% 4 4 3 5% 7% 38%	4081
	21st to end	Day	10% 6% 3 7% 5% 5% 5% 5% 6% 9% 40%	4663
June	1st to 10th	Day	10% 6% 3 5% 4 4 4 4 7% 7% 46%	2660
	11th to 20th	Day	7% 5% 2 5% 5% 5% 4 4 7% 8% 48%	2660
	21st to end	Day	8% 5% 2 6% 5% 5% 5% 4 7% 9% 44%	2660
July	1st to 10th	Day	11% 5% 2 6% 5% 5% 5% 4 8% 10% 39%	2660
	11th to 20th	Day	6% 4 2 5% 5% 4 5% 5% 7% 12% 46%	2660
	21st to end	Day	9% 5% 2 6% 4 5% 6% 5% 7% 10% 42%	2861
August	1st to 10th	Day	8% 4 2 6% 5% 4 5% 5% 6% 11% 44%	2262
	11th to 20th	Day	9% 5% 2 7% 4 4 5% 4 7% 9% 44%	2125
	21st to end	Day	6% 5% 2 5% 4 4 5% 4 6% 9% 50%	2376
September	1st to 10th	Day	11% 6% 2 6% 4 3 4 4 6% 8% 46%	2160
	11th to 20th	Day	9% 4 2 6% 4 4 4 3 6% 8% 49%	2005
	21st to end	Day	11% 4 2 4 3 4 3 3 5% 7% 55%	1980
October	1st to 10th	Day	11% 5% 2 4 3 3 4 3 5% 6% 54%	1980
	11th to 20th	Day	14% 6% 3 5% 4 3 4 3 4 6% 47%	1836
	21st to end	Day	19% 7% 3 6% 4 4 3 2 4 5% 43%	1794
November	1st to 10th	Day	9% 5% 2 5% 4 3 3 3 5% 7% 54%	1672
	11th to 20th	Day	17% 8% 2 6% 4 3 3 3 4 6% 44%	1710
	21st to end	Day	19% 10% 2 7% 4 3 4 3 4 6% 40%	1710
December	1st to 10th	Day	18% 13% 4 7% 5% 4 3 2 4 5% 36%	1687
	11th to 20th	Day	17% 12% 6% 10% 4 4 4 3 5% 5% 30%	1918
	21st to end	Day	23% 17% 6% 9% 5% 4 4 3 4 5% 21%	2783
January	1st to 10th	Night	18% 12% 5% 7% 4 4 4 4 5% 6% 30%	4428
	11th to 20th	Night	16% 14% 5% 11% 4 6% 6% 3 4 4 27%	4440
	21st to end	Night	25% 15% 6% 7% 4 3 3 3 4 5% 26%	4649
February	1st to 10th	Night	20% 11% 4 8% 5% 4 4 4 5% 5% 30%	2280
	11th to 20th	Night	15% 10% 3 7% 5% 5% 4 3 4 7% 37%	2218
	21st to end	Night	20% 10% 3 7% 5% 4 3 3 4 5% 34%	1884
March	1st to 10th	Night	23% 12% 3 8% 4 3 3 3 4 5% 33%	3733
	11th to 20th	Night	12% 6% 2 6% 4 3 3 3 4 6% 50%	3707
	21st to end	Night	18% 8% 3 6% 5% 4 5% 4 5% 5% 38%	3505
April	1st to 10th	Night	12% 7% 2 7% 5% 4 4 4 5% 6% 43%	1900
	11th to 20th	Night	16% 7% 2 5% 4 3 4 3 6% 7% 44%	1875
	21st to end	Night	18% 7% 2 5% 5% 4 4 5% 6% 7% 37%	1842
May	1st to 10th	Night	16% 8% 3 7% 5% 5% 4 4 6% 9% 33%	2813
	11th to 20th	Night	17% 7% 2 6% 4 4 4 3 5% 6% 43%	2812
	21st to end	Night	10% 6% 2 6% 5% 5% 6% 5% 7% 9% 40%	2881
June	1st to 10th	Night	9% 7% 2 4 3 4 4 3 7% 9% 48%	1520
	11th to 20th	Night	8% 5% 1 4 4 4 5% 4 6% 9% 50%	1520
	21st to end	Night	6% 3 1 4 3 5% 6% 4 8% 9% 51%	1520
July	1st to 10th	Night	8% 5% 2 5% 5% 4 4 4 5% 10% 48%	1520
	11th to 20th	Night	6% 4 2 4 4 4 5% 5% 8% 8% 53%	1520
	21st to end	Night	8% 5% 2 6% 4 4 4 4 6% 9% 48%	1687
August	1st to 10th	Night	6% 4 1 5% 4 5% 4 4 7% 9% 51%	1672
	11th to 20th	Night	5% 4 2 5% 5% 5% 5% 4 7% 9% 49%	1776
	21st to end	Night	5% 4 2 5% 4 3 4 4 5% 8% 56%	1980
September	1st to 10th	Night	11% 6% 2 5% 3 4 3 3 5% 7% 52%	1800
	11th to 20th	Night	7% 4 2 5% 4 4 3 4 5% 7% 54%	1935
	21st to end	Night	11% 5% 2 5% 3 3 3 3 5% 8% 52%	1980
October	1st to 10th	Night	9% 4 1 5% 2 4 3 3 5% 6% 58%	1980
	11th to 20th	Night	16% 5% 2 5% 3 4 3 2 4 5% 51%	2119
	21st to end	Night	19% 8% 2 6% 3 4 4 2 4 5% 43%	2560
November	1st to 10th	Night	11% 7% 2 5% 3 3 3 2 5% 6% 53%	2406
	11th to 20th	Night	14% 7% 2 5% 4 3 4 3 4 6% 48%	2470
	21st to end	Night	20% 8% 2 5% 4 3 3 3 4 6% 42%	2470
December	1st to 10th	Night	20% 9% 3 7% 4 3 4 3 4 8% 36%	2489
	11th to 20th	Night	19% 10% 3 8% 4 3 4 3 4 5% 38%	3279
	21st to end	Night	24% 16% 5% 8% 5% 5% 4 3 4 4 23%	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	54% 5% 11% 21% 8%	2528
	11th to 20th	Day	58% 8% 11% 18% 5%	2530
	21st to end	Day	64% 4 8% 18% 4 1	2998
February	1st to 10th	Day	53% 4 10% 21% 10% 2	1900
	11th to 20th	Day	51% 4 10% 22% 12% 2	1858
	21st to end	Day	52% 5% 8% 21% 11% 3	1570
March	1st to 10th	Day	55% 3 6% 19% 13% 4	3120
	11th to 20th	Day	38% 6% 11% 28% 15% 2	3251
	21st to end	Day	45% 9% 13% 23% 10% 1	4155
April	1st to 10th	Day	42% 7% 12% 23% 15% 1	2280
	11th to 20th	Day	43% 6% 10% 24% 14% 3	2254
	21st to end	Day	45% 5% 11% 24% 12% 3	2337
May	1st to 10th	Day	45% 11% 14% 22% 8%	4120
	11th to 20th	Day	44% 8% 11% 25% 11%	4085
	21st to end	Day	37% 8% 13% 19% 20% 3	4676
June	1st to 10th	Day	33% 9% 13% 25% 17% 4	2660
	11th to 20th	Day	31% 9% 12% 24% 20% 4	2660
	21st to end	Day	35% 8% 15% 21% 16% 5%	2660
July	1st to 10th	Day	36% 9% 14% 23% 14% 4	2591
	11th to 20th	Day	29% 9% 16% 27% 17% 3	2585
	21st to end	Day	34% 10% 14% 26% 14% 2	2710
August	1st to 10th	Day	32% 10% 15% 28% 15% 1	2249
	11th to 20th	Day	35% 9% 15% 26% 14% 2	2125
	21st to end	Day	29% 7% 16% 24% 16% 7%	2376
September	1st to 10th	Day	36% 7% 11% 25% 18% 4	2160
	11th to 20th	Day	33% 6% 12% 26% 22% 3	2005
	21st to end	Day	30% 5% 8% 27% 27% 3	1980
October	1st to 10th	Day	30% 5% 9% 27% 25% 4	1980
	11th to 20th	Day	37% 6% 8% 25% 21% 3	1836
	21st to end	Day	45% 4 8% 25% 16% 2	1794
November	1st to 10th	Day	31% 5% 10% 30% 17% 6%	1672
	11th to 20th	Day	42% 4 9% 23% 18% 5%	1710
	21st to end	Day	47% 3 10% 22% 16% 2	1710
December	1st to 10th	Day	52% 4 11% 21% 11% 1	1687
	11th to 20th	Day	56% 5% 8% 22% 9% 1	1915
	21st to end	Day	66% 6% 10% 12% 6% 1	2783
January	1st to 10th	Night	52% 7% 12% 20% 8% 1	4428
	11th to 20th	Night	60% 6% 9% 16% 8% 1	4440
	21st to end	Night	61% 4 9% 16% 9% 1	4649
February	1st to 10th	Night	56% 5% 11% 19% 9% 1	2280
	11th to 20th	Night	47% 5% 11% 21% 14% 1	2219
	21st to end	Night	52% 4 10% 20% 11% 3	1884
March	1st to 10th	Night	54% 4 7% 20% 12% 2	3733
	11th to 20th	Night	35% 6% 12% 24% 21% 2	3707
	21st to end	Night	46% 7% 10% 27% 9% 1	3505
April	1st to 10th	Night	40% 6% 10% 27% 15% 3	1900
	11th to 20th	Night	39% 4 11% 22% 19% 4	1875
	21st to end	Night	44% 6% 11% 22% 14% 3	1842
May	1st to 10th	Night	45% 12% 15% 21% 7% 1	2840
	11th to 20th	Night	41% 7% 13% 26% 13% 1	2813
	21st to end	Night	36% 10% 13% 20% 17% 4	2889
June	1st to 10th	Night	32% 6% 10% 26% 22% 4	1520
	11th to 20th	Night	29% 7% 12% 22% 23% 7%	1520
	21st to end	Night	26% 10% 15% 22% 20% 8%	1520
July	1st to 10th	Night	31% 8% 14% 25% 18% 4	1480
	11th to 20th	Night	26% 8% 15% 26% 20% 5%	1472
	21st to end	Night	30% 6% 14% 28% 19% 3	1598
August	1st to 10th	Night	26% 9% 17% 25% 20% 3	1661
	11th to 20th	Night	28% 9% 14% 28% 18% 3	1776
	21st to end	Night	25% 7% 14% 26% 21% 7%	1980
September	1st to 10th	Night	32% 6% 9% 26% 20% 6%	1800
	11th to 20th	Night	28% 4 11% 25% 26% 5%	1935
	21st to end	Night	30% 6% 10% 22% 25% 7%	1980
October	1st to 10th	Night	27% 5% 11% 24% 28% 5%	1980
	11th to 20th	Night	36% 4 6% 27% 22% 5%	2119
	21st to end	Night	43% 4 7% 24% 17% 4	2560
November	1st to 10th	Night	33% 5% 9% 26% 22% 6%	2406
	11th to 20th	Night	37% 4 10% 23% 22% 4	2470
	21st to end	Night	45% 3 11% 24% 15% 2	2470
December	1st to 10th	Night	49% 5% 11% 22% 12% 1	2489
	11th to 20th	Night	48% 5% 11% 22% 13% 1	3281
	21st to end	Night	65% 6% 8% 13% 8% 1	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	23% 14% 32% 22% 7% 1	270
	11th to 20th	Day	27% 16% 31% 21% 5%	270
	21st to end	Day	24% 14% 38% 18% 7%	297
February	1st to 10th	Day	24% 16% 35% 21% 3	270
	11th to 20th	Day	22% 19% 36% 17% 4 1	270
	21st to end	Day	27% 10% 39% 20% 4	225
March	1st to 10th	Day	21% 19% 37% 18% 4 1	270
	11th to 20th	Day	25% 18% 34% 15% 7% 1	322
	21st to end	Day	27% 14% 34% 17% 7% 1	506
April	1st to 10th	Day	17% 16% 32% 26% 9% 1	460
	11th to 20th	Day	20% 14% 28% 22% 14% 2	452
	21st to end	Day	21% 13% 33% 21% 8% 3	460
May	1st to 10th	Day	19% 11% 29% 28% 9% 3	463
	11th to 20th	Day	20% 6% 26% 24% 16% 8%	487
	21st to end	Day	11% 4 26% 26% 20% 13%	638
June	1st to 10th	Day	12% 5% 21% 25% 28% 8%	680
	11th to 20th	Day	10% 4 19% 32% 26% 11%	680
	21st to end	Day	8% 5% 25% 31% 21% 11%	680
July	1st to 10th	Day	11% 3 12% 25% 25% 24%	671
	11th to 20th	Day	7% 2 13% 33% 28% 17%	668
	21st to end	Day	10% 2 12% 29% 34% 13%	711
August	1st to 10th	Day	9% 3 11% 25% 34% 19%	446
	11th to 20th	Day	13% 3 10% 27% 32% 14%	439
	21st to end	Day	8% 1 9% 24% 35% 23%	495
September	1st to 10th	Day	10% 3 14% 24% 34% 15%	450
	11th to 20th	Day	8% 2 10% 26% 36% 17%	450
	21st to end	Day	13% 4 20% 24% 25% 14%	450
October	1st to 10th	Day	12% 4 20% 35% 20% 8%	450
	11th to 20th	Day	14% 11% 34% 26% 12% 3	306
	21st to end	Day	24% 12% 32% 25% 6%	297
November	1st to 10th	Day	13% 8% 34% 24% 15% 7%	270
	11th to 20th	Day	17% 16% 29% 24% 11% 3	270
	21st to end	Day	25% 9% 28% 26% 11% 2	270
December	1st to 10th	Day	16% 18% 36% 18% 9% 4	270
	11th to 20th	Day	24% 13% 34% 21% 8% 1	270
	21st to end	Day	29% 15% 33% 17% 5% 1	297
January	1st to 10th	Night	21% 12% 34% 28% 5%	950
	11th to 20th	Night	25% 13% 36% 23% 4	950
	21st to end	Night	23% 10% 36% 29% 3	1034
February	1st to 10th	Night	26% 10% 35% 26% 3	760
	11th to 20th	Night	21% 13% 38% 27% 2	743
	21st to end	Night	25% 13% 37% 23% 2	628
March	1st to 10th	Night	22% 11% 36% 27% 4	760
	11th to 20th	Night	20% 11% 37% 25% 7% 1	760
	21st to end	Night	24% 8% 29% 32% 6% 1	653
April	1st to 10th	Night	16% 10% 32% 35% 7%	570
	11th to 20th	Night	18% 8% 31% 29% 13% 1	563
	21st to end	Night	21% 6% 32% 31% 8% 1	570
May	1st to 10th	Night	16% 6% 29% 37% 10% 1	570
	11th to 20th	Night	15% 5% 23% 37% 18% 2	561
	21st to end	Night	9% 3 19% 40% 26% 3	617
June	1st to 10th	Night	12% 2 18% 41% 26% 1	570
	11th to 20th	Night	9% 2 17% 44% 26% 2	570
	21st to end	Night	7% 20% 42% 29% 2	570
July	1st to 10th	Night	10% 1 10% 34% 36% 8%	555
	11th to 20th	Night	5% 2 10% 42% 37% 5%	552
	21st to end	Night	8% 2 10% 39% 36% 5%	624
August	1st to 10th	Night	7% 1 8% 41% 39% 5%	537
	11th to 20th	Night	7% 1 8% 39% 41% 4	534
	21st to end	Night	7% 2 8% 34% 42% 9%	594
September	1st to 10th	Night	13% 1 10% 33% 38% 5%	540
	11th to 20th	Night	7% 1 14% 34% 36% 7%	675
	21st to end	Night	11% 4 21% 30% 31% 4	720
October	1st to 10th	Night	10% 4 20% 37% 24% 5%	720
	11th to 20th	Night	18% 6% 30% 30% 14% 2	720
	21st to end	Night	23% 8% 30% 31% 8%	792
November	1st to 10th	Night	13% 7% 30% 35% 14% 1	740
	11th to 20th	Night	16% 10% 32% 31% 10% 1	760
	21st to end	Night	23% 10% 27% 30% 9%	760
December	1st to 10th	Night	24% 8% 34% 28% 7%	779
	11th to 20th	Night	25% 7% 29% 31% 7% 1	950
	21st to end	Night	28% 13% 32% 22% 4	1045

Page generated at 2024-07-28 09:52:14. Version ac07

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