Tecumseh
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tecumseh clear sky chart from 2005-11-06 to 2024-10-25.

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 6% 4 4 4 3 5% 7% 46%	100789
	Night	10% 7% 2 6% 4 4 4 3 5% 6% 49%	98081
Transparency	Day	37% 5% 12% 26% 17% 3	100601
	Night	35% 5% 12% 26% 19% 3	97940
Seeing	Day	14% 10% 30% 28% 15% 3	15643
	Night	13% 9% 33% 33% 11% 1	25460

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% 10% 3 10% 5% 4 4 3 5% 6% 37%	2847
	11th to 20th	Day	9% 11% 4 9% 6% 7% 5% 3 4 6% 37%	2850
	21st to end	Day	12% 15% 7% 8% 3 3 3 3 4 6% 36%	3135
February	1st to 10th	Day	13% 12% 4 7% 4 5% 3 4 5% 5% 40%	1710
	11th to 20th	Day	10% 10% 3 7% 4 4 4 4 6% 7% 42%	1705
	21st to end	Day	9% 10% 3 6% 4 4 3 3 6% 6% 46%	1592
March	1st to 10th	Day	12% 8% 2 5% 4 3 3 3 4 6% 50%	3436
	11th to 20th	Day	12% 6% 1 5% 2 2 4 3 5% 6% 53%	3480
	21st to end	Day	14% 10% 6% 7% 4 4 4 3 4 6% 37%	3814
April	1st to 10th	Day	13% 7% 3 5% 4 3 4 3 4 7% 48%	2152
	11th to 20th	Day	14% 8% 3 7% 4 4 4 4 5% 7% 42%	2269
	21st to end	Day	18% 7% 3 6% 5% 4 5% 3 5% 6% 39%	2470
May	1st to 10th	Day	15% 9% 3 7% 4 3 4 3 4 6% 40%	4082
	11th to 20th	Day	15% 7% 3 6% 4 5% 4 4 5% 8% 40%	4082
	21st to end	Day	13% 6% 2 6% 4 4 4 4 6% 8% 44%	4477
June	1st to 10th	Day	5% 4 2 4 4 5% 5% 5% 7% 11% 49%	2532
	11th to 20th	Day	7% 4 2 5% 4 4 5% 4 6% 10% 48%	2647
	21st to end	Day	6% 4 2 4 4 4 5% 4 6% 8% 52%	2470
July	1st to 10th	Day	11% 6% 2 6% 4 4 5% 4 6% 8% 43%	4120
	11th to 20th	Day	5% 3 2 4 4 4 4 4 8% 10% 53%	4120
	21st to end	Day	5% 4 2 5% 4 4 5% 5% 8% 9% 49%	4465
August	1st to 10th	Day	6% 4 2 4 3 4 5% 5% 6% 8% 53%	4104
	11th to 20th	Day	11% 6% 2 6% 4 4 4 3 5% 8% 47%	4041
	21st to end	Day	5% 4 2 4 4 4 4 4 6% 9% 55%	4350
September	1st to 10th	Day	11% 4 1 5% 4 4 3 2 5% 7% 54%	2222
	11th to 20th	Day	9% 5% 2 6% 4 5% 4 4 5% 6% 50%	2090
	21st to end	Day	9% 5% 1 5% 3 3 4 4 5% 6% 55%	2090
October	1st to 10th	Day	10% 5% 2 5% 3 3 2 3 5% 8% 53%	1929
	11th to 20th	Day	11% 6% 1 5% 3 2 3 2 3 5% 58%	1900
	21st to end	Day	15% 6% 2 5% 3 3 4 3 5% 5% 50%	2026
November	1st to 10th	Day	8% 5% 2 5% 3 4 3 3 4 7% 56%	1797
	11th to 20th	Day	11% 6% 2 4 3 4 3 4 3 5% 56%	1710
	21st to end	Day	15% 7% 2 5% 4 3 2 2 4 6% 50%	1552
December	1st to 10th	Day	9% 7% 2 5% 5% 4 4 3 5% 7% 48%	1520
	11th to 20th	Day	11% 9% 4 8% 5% 4 3 3 4 6% 42%	1918
	21st to end	Day	15% 15% 7% 13% 5% 4 4 3 4 6% 25%	3085
January	1st to 10th	Night	8% 9% 4 15% 5% 4 4 2 4 5% 39%	4108
	11th to 20th	Night	10% 9% 4 8% 5% 6% 6% 3 4 5% 40%	4120
	21st to end	Night	16% 12% 4 8% 4 3 4 3 3 5% 38%	4532
February	1st to 10th	Night	11% 12% 3 7% 5% 4 4 3 5% 6% 40%	2470
	11th to 20th	Night	11% 8% 2 8% 4 3 4 3 5% 5% 46%	2380
	21st to end	Night	10% 7% 2 6% 4 5% 3 3 5% 5% 50%	1860
March	1st to 10th	Night	12% 7% 2 5% 3 3 3 2 3 5% 53%	3419
	11th to 20th	Night	10% 6% 2 4 3 3 3 3 5% 7% 55%	3480
	21st to end	Night	16% 9% 3 6% 5% 4 4 3 5% 6% 39%	3817
April	1st to 10th	Night	10% 6% 2 5% 3 4 3 2 5% 7% 51%	2028
	11th to 20th	Night	12% 8% 2 6% 4 4 4 3 5% 7% 46%	1857
	21st to end	Night	17% 7% 2 5% 3 5% 5% 4 5% 5% 43%	1710
May	1st to 10th	Night	15% 8% 3 5% 4 4 4 3 6% 7% 42%	2823
	11th to 20th	Night	14% 6% 2 6% 4 4 4 3 5% 8% 44%	2823
	21st to end	Night	11% 4 2 4 3 3 3 3 5% 7% 54%	3090
June	1st to 10th	Night	5% 4 2 4 3 4 4 4 6% 9% 56%	1634
	11th to 20th	Night	6% 4 2 4 3 4 5% 4 7% 9% 53%	1521
	21st to end	Night	4 3 1 4 3 3 3 4 6% 8% 60%	1708
July	1st to 10th	Night	9% 6% 2 6% 4 3 4 3 5% 6% 51%	2850
	11th to 20th	Night	2 2 1 4 3 3 3 4 7% 10% 60%	2850
	21st to end	Night	5% 3 2 5% 4 4 4 4 7% 10% 51%	3098
August	1st to 10th	Night	2 1 1 4 4 4 5% 5% 6% 11% 57%	2836
	11th to 20th	Night	9% 6% 2 5% 4 4 4 3 5% 7% 51%	2798
	21st to end	Night	5% 3 2 5% 3 3 3 3 5% 8% 59%	3311
September	1st to 10th	Night	10% 4 2 5% 3 3 3 3 5% 5% 56%	1954
	11th to 20th	Night	8% 4 1 4 4 3 4 4 5% 7% 55%	2090
	21st to end	Night	6% 4 2 5% 3 4 4 3 4 6% 59%	2090
October	1st to 10th	Night	11% 4 1 5% 3 4 3 3 4 6% 55%	2231
	11th to 20th	Night	12% 4 1 4 3 3 2 2 3 6% 59%	2280
	21st to end	Night	14% 7% 2 5% 3 2 3 2 3 4 54%	2436
November	1st to 10th	Night	8% 4 1 4 3 2 3 3 4 5% 62%	2280
	11th to 20th	Night	10% 5% 2 4 4 4 3 3 5% 5% 56%	2470
	21st to end	Night	13% 7% 1 3 3 3 3 2 4 5% 54%	2624
December	1st to 10th	Night	9% 7% 3 5% 5% 4 4 4 5% 6% 48%	2660
	11th to 20th	Night	11% 8% 3 6% 4 3 4 4 5% 6% 46%	3279
	21st to end	Night	18% 16% 5% 9% 4 3 4 2 3 4 32%	4564

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	48% 5% 12% 24% 11% 1	2848
	11th to 20th	Day	50% 3 15% 19% 12% 1	2850
	21st to end	Day	50% 3 13% 20% 13% 1	3135
February	1st to 10th	Day	46% 5% 13% 22% 11% 3	1710
	11th to 20th	Day	42% 4 12% 25% 14% 3	1714
	21st to end	Day	39% 4 11% 24% 18% 4	1592
March	1st to 10th	Day	36% 3 10% 22% 23% 5%	3436
	11th to 20th	Day	31% 5% 11% 28% 22% 2	3480
	21st to end	Day	48% 6% 15% 25% 6% 1	3814
April	1st to 10th	Day	38% 4 12% 22% 21% 3	2152
	11th to 20th	Day	42% 5% 12% 23% 17% 1	2269
	21st to end	Day	46% 5% 11% 26% 11% 1	2470
May	1st to 10th	Day	45% 6% 9% 23% 15% 2	4120
	11th to 20th	Day	40% 8% 14% 21% 17%	4086
	21st to end	Day	37% 7% 10% 30% 14% 2	4489
June	1st to 10th	Day	26% 8% 17% 29% 17% 2	2532
	11th to 20th	Day	31% 7% 13% 29% 17% 2	2647
	21st to end	Day	28% 7% 14% 29% 18% 4	2470
July	1st to 10th	Day	38% 6% 13% 23% 18% 3	4056
	11th to 20th	Day	25% 7% 13% 34% 19% 3	4051
	21st to end	Day	27% 7% 16% 30% 17% 3	4325
August	1st to 10th	Day	28% 7% 12% 26% 23% 3	4090
	11th to 20th	Day	36% 5% 15% 26% 16% 1	4080
	21st to end	Day	26% 6% 17% 29% 17% 6%	4349
September	1st to 10th	Day	30% 5% 12% 26% 20% 7%	2222
	11th to 20th	Day	33% 6% 9% 27% 21% 3	2090
	21st to end	Day	29% 6% 9% 28% 25% 3	2090
October	1st to 10th	Day	30% 4 12% 27% 24% 3	1929
	11th to 20th	Day	30% 3 7% 25% 28% 7%	1900
	21st to end	Day	36% 4 11% 25% 19% 6%	2026
November	1st to 10th	Day	29% 5% 12% 29% 20% 6%	1797
	11th to 20th	Day	32% 3 10% 29% 23% 3	1710
	21st to end	Day	37% 4 10% 26% 22% 2	1552
December	1st to 10th	Day	35% 4 15% 31% 14% 1	1520
	11th to 20th	Day	44% 4 12% 25% 13% 1	1915
	21st to end	Day	61% 4 10% 17% 8% 1	3085
January	1st to 10th	Night	47% 4 14% 22% 12% 1	4108
	11th to 20th	Night	46% 4 13% 22% 15% 1	4120
	21st to end	Night	49% 4 15% 19% 12% 2	4532
February	1st to 10th	Night	44% 5% 12% 22% 14% 3	2470
	11th to 20th	Night	40% 3 11% 25% 16% 4	2381
	21st to end	Night	37% 4 9% 22% 21% 7%	1860
March	1st to 10th	Night	34% 4 8% 27% 23% 4	3419
	11th to 20th	Night	28% 5% 10% 26% 27% 5%	3480
	21st to end	Night	44% 6% 16% 24% 8% 1	3817
April	1st to 10th	Night	34% 3 11% 24% 23% 5%	2028
	11th to 20th	Night	37% 6% 9% 26% 19% 3	1857
	21st to end	Night	41% 6% 11% 25% 15% 2	1710
May	1st to 10th	Night	40% 8% 14% 21% 15% 3	2850
	11th to 20th	Night	38% 7% 13% 26% 17% 1	2824
	21st to end	Night	29% 7% 14% 31% 18% 1	3099
June	1st to 10th	Night	24% 7% 17% 33% 16% 3	1634
	11th to 20th	Night	25% 8% 13% 32% 18% 3	1521
	21st to end	Night	20% 5% 15% 34% 21% 4	1708
July	1st to 10th	Night	34% 6% 12% 23% 20% 5%	2805
	11th to 20th	Night	17% 6% 14% 35% 25% 3	2796
	21st to end	Night	26% 6% 18% 31% 18% 1	2999
August	1st to 10th	Night	20% 6% 18% 27% 22% 6%	2826
	11th to 20th	Night	33% 5% 14% 27% 20% 2	2825
	21st to end	Night	24% 5% 13% 35% 18% 5%	3311
September	1st to 10th	Night	29% 5% 10% 27% 21% 9%	1954
	11th to 20th	Night	27% 6% 11% 27% 25% 5%	2090
	21st to end	Night	27% 4 8% 26% 31% 4	2090
October	1st to 10th	Night	30% 5% 9% 23% 28% 6%	2231
	11th to 20th	Night	29% 3 7% 28% 25% 9%	2280
	21st to end	Night	36% 3 8% 23% 26% 4	2436
November	1st to 10th	Night	26% 3 12% 28% 24% 7%	2280
	11th to 20th	Night	29% 4 11% 28% 24% 4	2470
	21st to end	Night	34% 3 10% 30% 20% 3	2624
December	1st to 10th	Night	36% 5% 13% 27% 17% 1	2660
	11th to 20th	Night	39% 4 10% 30% 16% 1	3281
	21st to end	Night	56% 4 8% 21% 8% 2	4564

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	21% 16% 36% 21% 7%	270
	11th to 20th	Day	25% 18% 39% 16% 2	270
	21st to end	Day	12% 15% 49% 21% 3	297
February	1st to 10th	Day	21% 20% 39% 17% 2	270
	11th to 20th	Day	18% 19% 46% 11% 6%	270
	21st to end	Day	12% 29% 43% 12% 4	225
March	1st to 10th	Day	15% 17% 44% 21% 3	270
	11th to 20th	Day	25% 15% 37% 17% 5%	270
	21st to end	Day	27% 22% 37% 10% 3	297
April	1st to 10th	Day	22% 18% 36% 19% 6%	332
	11th to 20th	Day	18% 15% 38% 23% 5% 1	467
	21st to end	Day	22% 15% 36% 18% 9%	650
May	1st to 10th	Day	18% 17% 36% 21% 8%	653
	11th to 20th	Day	18% 8% 32% 29% 12% 2	675
	21st to end	Day	17% 10% 31% 26% 14% 2	734
June	1st to 10th	Day	5% 5% 23% 36% 26% 5%	680
	11th to 20th	Day	6% 5% 30% 36% 18% 5%	680
	21st to end	Day	7% 7% 34% 38% 13% 2	680
July	1st to 10th	Day	10% 3 18% 33% 28% 9%	671
	11th to 20th	Day	4 2 19% 40% 28% 6%	668
	21st to end	Day	8% 3 19% 35% 28% 8%	739
August	1st to 10th	Day	8% 3 17% 41% 27% 5%	676
	11th to 20th	Day	9% 2 21% 41% 23% 4	665
	21st to end	Day	10% 1 15% 36% 31% 7%	644
September	1st to 10th	Day	13% 2 19% 36% 26% 4	432
	11th to 20th	Day	6% 3 24% 38% 25% 4	300
	21st to end	Day	14% 6% 29% 34% 13% 4	300
October	1st to 10th	Day	12% 8% 29% 29% 15% 6%	300
	11th to 20th	Day	9% 18% 42% 20% 10% 1	300
	21st to end	Day	22% 16% 35% 19% 8% 1	311
November	1st to 10th	Day	14% 13% 36% 27% 9% 2	270
	11th to 20th	Day	15% 18% 36% 24% 7%	270
	21st to end	Day	22% 14% 37% 19% 7%	270
December	1st to 10th	Day	9% 17% 39% 27% 6% 2	270
	11th to 20th	Day	17% 17% 37% 21% 7% 1	270
	21st to end	Day	21% 22% 38% 18% 1	297
January	1st to 10th	Night	12% 13% 38% 30% 7%	950
	11th to 20th	Night	15% 13% 38% 28% 5% 1	950
	21st to end	Night	14% 12% 40% 29% 4	1045
February	1st to 10th	Night	18% 13% 40% 26% 3	950
	11th to 20th	Night	15% 14% 40% 28% 3	906
	21st to end	Night	15% 14% 42% 23% 6%	604
March	1st to 10th	Night	14% 13% 42% 26% 5%	570
	11th to 20th	Night	18% 11% 36% 28% 5% 1	570
	21st to end	Night	23% 14% 37% 22% 4	627
April	1st to 10th	Night	14% 13% 42% 25% 5%	570
	11th to 20th	Night	16% 13% 41% 25% 5%	563
	21st to end	Night	20% 11% 37% 25% 6% 1	570
May	1st to 10th	Night	17% 9% 37% 30% 6% 1	570
	11th to 20th	Night	14% 9% 32% 34% 11% 1	561
	21st to end	Night	12% 6% 33% 34% 14% 2	617
June	1st to 10th	Night	6% 4 24% 42% 23% 1	570
	11th to 20th	Night	7% 3 29% 43% 16% 1	570
	21st to end	Night	4 5% 34% 45% 12% 1	570
July	1st to 10th	Night	8% 3 15% 46% 27% 2	555
	11th to 20th	Night	3 1 18% 50% 26% 2	552
	21st to end	Night	7% 2 16% 47% 26% 2	624
August	1st to 10th	Night	4 1 17% 48% 28% 2	567
	11th to 20th	Night	7% 1 15% 50% 26% 2	564
	21st to end	Night	7% 1 17% 42% 31% 2	627
September	1st to 10th	Night	12% 3 19% 43% 21% 2	570
	11th to 20th	Night	9% 1 23% 43% 21% 2	570
	21st to end	Night	8% 4 27% 43% 18% 1	570
October	1st to 10th	Night	13% 5% 29% 34% 19% 1	711
	11th to 20th	Night	14% 8% 41% 30% 7%	760
	21st to end	Night	17% 12% 35% 27% 8%	812
November	1st to 10th	Night	10% 10% 34% 34% 11% 1	800
	11th to 20th	Night	12% 14% 38% 29% 7%	950
	21st to end	Night	17% 10% 35% 31% 7%	950
December	1st to 10th	Night	13% 12% 38% 31% 5% 1	950
	11th to 20th	Night	17% 10% 40% 28% 5%	950
	21st to end	Night	18% 15% 36% 26% 4	1045

Page generated at 2024-10-22 19:20:59. Version ac07

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