Lansing
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lansing clear sky chart from 2005-11-06 to 2024-11-01.

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% 10% 3 8% 5% 5% 5% 4 6% 7% 34%	101170
	Night	14% 11% 4 9% 5% 4 4 3 5% 6% 34%	97811
Transparency	Day	48% 6% 12% 20% 12% 1	100965
	Night	50% 6% 11% 20% 12% 1	97687
Seeing	Day	17% 11% 28% 24% 14% 6%	15749
	Night	19% 9% 30% 30% 12% 1	25589

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	16% 18% 6% 12% 7% 5% 5% 4 4 4 19%	2527
	11th to 20th	Day	15% 18% 7% 14% 10% 11% 5% 3 4 4 10%	2530
	21st to end	Day	25% 23% 6% 12% 5% 4 3 2 3 4 12%	2880
February	1st to 10th	Day	13% 14% 5% 12% 9% 7% 6% 4 5% 5% 20%	1714
	11th to 20th	Day	13% 12% 6% 13% 9% 6% 4 3 3 5% 25%	1848
	21st to end	Day	14% 16% 5% 12% 6% 4 4 3 5% 6% 24%	1570
March	1st to 10th	Day	16% 15% 3 8% 5% 4 4 3 5% 6% 30%	3120
	11th to 20th	Day	11% 11% 4 11% 7% 6% 5% 4 5% 7% 30%	3469
	21st to end	Day	19% 14% 4 8% 6% 4 4 3 4 5% 28%	3836
April	1st to 10th	Day	18% 13% 3 8% 6% 4 4 4 5% 5% 30%	2280
	11th to 20th	Day	17% 9% 3 7% 5% 4 5% 4 5% 5% 36%	2356
	21st to end	Day	17% 9% 3 8% 5% 5% 4 4 5% 7% 34%	2470
May	1st to 10th	Day	17% 9% 2 7% 4 4 4 4 5% 7% 36%	4082
	11th to 20th	Day	15% 8% 2 7% 4 5% 4 4 6% 8% 38%	4081
	21st to end	Day	11% 7% 2 6% 5% 4 4 3 5% 8% 45%	4658
June	1st to 10th	Day	11% 4 2 6% 6% 5% 5% 4 6% 8% 43%	2660
	11th to 20th	Day	11% 5% 2 6% 5% 4 4 5% 6% 9% 43%	2660
	21st to end	Day	9% 5% 2 7% 5% 5% 6% 5% 8% 8% 40%	2660
July	1st to 10th	Day	11% 7% 2 7% 5% 5% 6% 5% 7% 9% 36%	4440
	11th to 20th	Day	7% 4 2 4 4 4 5% 4 7% 10% 49%	4440
	21st to end	Day	6% 5% 2 6% 6% 4 6% 5% 7% 9% 44%	4705
August	1st to 10th	Day	12% 5% 2 5% 5% 5% 5% 4 6% 8% 42%	4104
	11th to 20th	Day	11% 6% 2 6% 5% 4 5% 4 6% 8% 43%	4044
	21st to end	Day	7% 6% 3 7% 5% 5% 6% 4 7% 8% 41%	4351
September	1st to 10th	Day	11% 6% 3 7% 5% 5% 4 4 6% 8% 42%	2199
	11th to 20th	Day	11% 5% 2 5% 4 3 4 4 6% 9% 47%	2090
	21st to end	Day	13% 8% 3 8% 4 5% 4 5% 6% 8% 37%	2090
October	1st to 10th	Day	13% 7% 2 7% 5% 4 5% 4 5% 7% 41%	2087
	11th to 20th	Day	18% 10% 4 7% 5% 4 5% 3 6% 7% 31%	1877
	21st to end	Day	20% 12% 4 8% 4 5% 5% 4 5% 6% 27%	1881
November	1st to 10th	Day	11% 12% 3 7% 4 5% 4 3 5% 6% 39%	1672
	11th to 20th	Day	14% 15% 4 9% 6% 5% 4 4 5% 6% 27%	1710
	21st to end	Day	19% 15% 5% 9% 5% 3 4 3 4 5% 27%	1710
December	1st to 10th	Day	13% 18% 9% 14% 6% 5% 4 3 4 5% 19%	1668
	11th to 20th	Day	14% 19% 6% 11% 5% 5% 5% 5% 6% 6% 20%	1918
	21st to end	Day	22% 24% 7% 13% 5% 4 4 3 3 4 11%	2783
January	1st to 10th	Night	16% 18% 7% 12% 6% 5% 5% 3 4 5% 19%	4428
	11th to 20th	Night	14% 18% 8% 17% 7% 9% 4 3 4 4 13%	4440
	21st to end	Night	23% 18% 9% 12% 6% 4 4 2 3 5% 14%	4781
February	1st to 10th	Night	15% 17% 5% 11% 9% 5% 4 4 5% 4 22%	2461
	11th to 20th	Night	13% 13% 6% 11% 7% 6% 5% 4 5% 5% 25%	2218
	21st to end	Night	17% 11% 5% 10% 5% 5% 4 4 5% 6% 27%	1884
March	1st to 10th	Night	15% 10% 4 8% 5% 4 3 3 5% 7% 37%	3733
	11th to 20th	Night	8% 10% 3 6% 4 4 5% 4 5% 8% 44%	3490
	21st to end	Night	16% 11% 5% 10% 5% 4 4 3 4 6% 32%	3817
April	1st to 10th	Night	15% 12% 3 7% 5% 3 4 4 6% 6% 35%	1908
	11th to 20th	Night	19% 9% 2 7% 4 4 4 3 5% 6% 37%	1772
	21st to end	Night	17% 8% 2 7% 4 5% 4 4 4 7% 37%	1710
May	1st to 10th	Night	14% 9% 2 7% 4 4 5% 4 6% 9% 35%	2813
	11th to 20th	Night	17% 8% 2 6% 4 4 3 3 4 6% 43%	2812
	21st to end	Night	11% 6% 3 6% 3 5% 5% 4 5% 9% 45%	2899
June	1st to 10th	Night	12% 4 2 6% 4 3 4 4 6% 8% 46%	1520
	11th to 20th	Night	11% 5% 2 5% 5% 4 4 3 7% 8% 45%	1520
	21st to end	Night	9% 5% 2 5% 5% 3 4 4 6% 10% 46%	1520
July	1st to 10th	Night	8% 5% 2 5% 5% 4 5% 4 7% 10% 44%	2530
	11th to 20th	Night	9% 4 2 5% 3 4 4 4 5% 7% 55%	2530
	21st to end	Night	5% 5% 3 7% 5% 5% 4 5% 6% 9% 46%	2841
August	1st to 10th	Night	9% 5% 2 6% 4 4 4 3 5% 9% 48%	2825
	11th to 20th	Night	11% 6% 2 6% 4 4 4 4 5% 7% 47%	2785
	21st to end	Night	9% 7% 3 7% 5% 4 5% 4 6% 7% 45%	3302
September	1st to 10th	Night	9% 6% 2 5% 4 5% 4 4 6% 7% 49%	1961
	11th to 20th	Night	10% 5% 2 4 4 3 3 3 4 7% 55%	2090
	21st to end	Night	15% 6% 2 6% 4 4 4 3 5% 7% 42%	2090
October	1st to 10th	Night	15% 7% 2 6% 4 3 3 3 5% 6% 46%	2091
	11th to 20th	Night	18% 12% 2 8% 4 4 4 3 5% 5% 33%	2299
	21st to end	Night	20% 10% 3 8% 5% 4 4 3 5% 6% 31%	2717
November	1st to 10th	Night	14% 10% 3 7% 4 4 4 3 4 6% 41%	2413
	11th to 20th	Night	14% 14% 3 10% 5% 5% 5% 4 6% 7% 27%	2470
	21st to end	Night	18% 14% 4 9% 4 4 4 3 5% 6% 28%	2470
December	1st to 10th	Night	16% 19% 7% 12% 6% 5% 4 3 4 5% 19%	2508
	11th to 20th	Night	14% 16% 6% 15% 7% 5% 5% 3 5% 5% 20%	3279
	21st to end	Night	26% 22% 6% 10% 5% 4 3 3 4 4 12%	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	67% 7% 10% 13% 3	2528
	11th to 20th	Day	76% 7% 9% 6% 2	2530
	21st to end	Day	77% 4 9% 7% 2	2880
February	1st to 10th	Day	64% 6% 10% 13% 6%	1714
	11th to 20th	Day	63% 4 8% 16% 9% 1	1858
	21st to end	Day	61% 5% 11% 15% 6% 1	1570
March	1st to 10th	Day	54% 6% 12% 20% 8% 1	3120
	11th to 20th	Day	51% 6% 13% 20% 9% 1	3469
	21st to end	Day	57% 5% 11% 16% 9% 2	3836
April	1st to 10th	Day	55% 5% 11% 18% 11%	2280
	11th to 20th	Day	48% 6% 10% 20% 14% 2	2356
	21st to end	Day	49% 5% 12% 17% 14% 2	2470
May	1st to 10th	Day	47% 6% 12% 21% 13% 1	4120
	11th to 20th	Day	42% 8% 14% 24% 10% 1	4085
	21st to end	Day	36% 7% 11% 21% 23% 3	4671
June	1st to 10th	Day	37% 7% 12% 27% 15% 2	2660
	11th to 20th	Day	37% 7% 12% 24% 18% 1	2660
	21st to end	Day	38% 8% 13% 22% 16% 2	2660
July	1st to 10th	Day	42% 7% 12% 20% 15% 3	4371
	11th to 20th	Day	28% 7% 14% 32% 18% 2	4365
	21st to end	Day	34% 8% 15% 20% 22% 2	4556
August	1st to 10th	Day	37% 7% 12% 26% 16% 1	4091
	11th to 20th	Day	37% 6% 11% 31% 13% 1	4083
	21st to end	Day	37% 7% 12% 29% 13% 2	4350
September	1st to 10th	Day	39% 7% 13% 25% 15% 2	2199
	11th to 20th	Day	34% 6% 12% 30% 18% 1	2090
	21st to end	Day	44% 6% 13% 22% 15%	2090
October	1st to 10th	Day	41% 7% 10% 26% 15% 1	2087
	11th to 20th	Day	52% 6% 13% 19% 10%	1877
	21st to end	Day	57% 5% 13% 17% 7% 1	1881
November	1st to 10th	Day	46% 7% 12% 22% 13% 1	1672
	11th to 20th	Day	57% 5% 12% 18% 7% 1	1710
	21st to end	Day	59% 5% 14% 16% 6% 1	1710
December	1st to 10th	Day	68% 6% 10% 13% 3 1	1668
	11th to 20th	Day	63% 7% 13% 14% 3	1915
	21st to end	Day	78% 4 9% 6% 3	2783
January	1st to 10th	Night	66% 6% 9% 12% 5% 1	4428
	11th to 20th	Night	74% 6% 8% 7% 5%	4440
	21st to end	Night	74% 5% 8% 10% 3 1	4781
February	1st to 10th	Night	64% 6% 10% 13% 6% 1	2461
	11th to 20th	Night	60% 5% 9% 17% 9% 1	2219
	21st to end	Night	57% 5% 13% 16% 8% 2	1884
March	1st to 10th	Night	47% 5% 15% 25% 8% 1	3733
	11th to 20th	Night	37% 6% 16% 21% 19% 2	3490
	21st to end	Night	52% 6% 12% 21% 8% 1	3817
April	1st to 10th	Night	47% 6% 11% 20% 15% 1	1908
	11th to 20th	Night	47% 5% 11% 18% 17% 2	1772
	21st to end	Night	45% 6% 13% 19% 15% 3	1710
May	1st to 10th	Night	44% 6% 13% 21% 14% 2	2840
	11th to 20th	Night	41% 7% 8% 25% 17% 2	2813
	21st to end	Night	36% 7% 11% 22% 20% 4	2907
June	1st to 10th	Night	34% 7% 11% 28% 18% 3	1520
	11th to 20th	Night	36% 6% 14% 24% 18% 2	1520
	21st to end	Night	33% 7% 13% 27% 18% 2	1520
July	1st to 10th	Night	34% 5% 13% 27% 14% 7%	2490
	11th to 20th	Night	28% 5% 12% 31% 22% 1	2482
	21st to end	Night	33% 7% 17% 17% 24% 2	2750
August	1st to 10th	Night	33% 6% 14% 28% 19% 1	2814
	11th to 20th	Night	35% 7% 9% 33% 14% 1	2812
	21st to end	Night	37% 6% 11% 30% 15% 2	3302
September	1st to 10th	Night	33% 7% 11% 28% 19% 2	1961
	11th to 20th	Night	29% 5% 11% 31% 22% 2	2090
	21st to end	Night	40% 6% 12% 26% 15% 1	2090
October	1st to 10th	Night	39% 5% 11% 27% 17% 1	2091
	11th to 20th	Night	52% 5% 11% 19% 12% 1	2299
	21st to end	Night	53% 5% 11% 21% 9% 1	2717
November	1st to 10th	Night	45% 5% 11% 24% 15% 1	2413
	11th to 20th	Night	54% 6% 13% 19% 7% 1	2470
	21st to end	Night	57% 5% 13% 18% 6%	2470
December	1st to 10th	Night	67% 6% 10% 11% 5%	2508
	11th to 20th	Night	65% 6% 11% 12% 6%	3281
	21st to end	Night	76% 4 10% 7% 3	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	20% 16% 38% 19% 7% 2	270
	11th to 20th	Day	21% 14% 44% 15% 5% 1	270
	21st to end	Day	28% 16% 31% 20% 5%	297
February	1st to 10th	Day	22% 23% 33% 17% 3 1	270
	11th to 20th	Day	23% 18% 39% 18% 2	270
	21st to end	Day	24% 26% 36% 10% 3	225
March	1st to 10th	Day	21% 20% 42% 13% 4	270
	11th to 20th	Day	22% 15% 33% 22% 8%	449
	21st to end	Day	27% 13% 30% 23% 5% 2	506
April	1st to 10th	Day	21% 15% 33% 23% 7% 1	460
	11th to 20th	Day	26% 16% 30% 16% 7% 5%	452
	21st to end	Day	20% 14% 30% 22% 12% 2	460
May	1st to 10th	Day	25% 13% 27% 24% 10% 2	463
	11th to 20th	Day	18% 10% 26% 25% 15% 6%	487
	21st to end	Day	15% 7% 24% 27% 19% 9%	633
June	1st to 10th	Day	12% 8% 28% 31% 16% 5%	680
	11th to 20th	Day	14% 6% 30% 29% 18% 4	680
	21st to end	Day	12% 9% 26% 30% 17% 6%	680
July	1st to 10th	Day	9% 6% 19% 30% 22% 14%	671
	11th to 20th	Day	10% 6% 24% 29% 21% 10%	668
	21st to end	Day	7% 4 25% 33% 23% 9%	680
August	1st to 10th	Day	9% 3 21% 28% 19% 20%	486
	11th to 20th	Day	14% 4 17% 27% 26% 12%	479
	21st to end	Day	11% 4 21% 26% 26% 13%	539
September	1st to 10th	Day	14% 7% 21% 24% 22% 11%	490
	11th to 20th	Day	11% 4 18% 24% 29% 13%	490
	21st to end	Day	18% 12% 19% 24% 18% 10%	490
October	1st to 10th	Day	18% 10% 27% 23% 15% 7%	490
	11th to 20th	Day	20% 15% 29% 26% 9% 1	467
	21st to end	Day	28% 15% 35% 16% 4 1	330
November	1st to 10th	Day	17% 17% 34% 22% 9% 1	270
	11th to 20th	Day	24% 20% 33% 18% 4	270
	21st to end	Day	26% 15% 40% 14% 5%	270
December	1st to 10th	Day	24% 24% 26% 18% 6% 1	270
	11th to 20th	Day	23% 19% 39% 14% 4	270
	21st to end	Day	24% 23% 37% 14% 2	297
January	1st to 10th	Night	22% 13% 37% 21% 6% 1	950
	11th to 20th	Night	24% 14% 35% 22% 4 1	950
	21st to end	Night	19% 11% 37% 28% 5%	981
February	1st to 10th	Night	24% 12% 35% 25% 3	760
	11th to 20th	Night	22% 13% 36% 25% 4	743
	21st to end	Night	24% 15% 39% 20% 3	628
March	1st to 10th	Night	20% 12% 36% 26% 6% 1	760
	11th to 20th	Night	17% 14% 37% 26% 6% 1	760
	21st to end	Night	23% 9% 32% 28% 7%	836
April	1st to 10th	Night	19% 12% 37% 26% 6% 1	578
	11th to 20th	Night	23% 10% 35% 23% 8% 1	563
	21st to end	Night	22% 7% 34% 30% 6% 1	570
May	1st to 10th	Night	19% 7% 31% 34% 9% 1	570
	11th to 20th	Night	23% 4 30% 30% 12% 1	561
	21st to end	Night	13% 3 27% 35% 20% 2	617
June	1st to 10th	Night	12% 4 25% 43% 15% 1	570
	11th to 20th	Night	13% 4 26% 40% 16% 1	570
	21st to end	Night	10% 4 23% 41% 20% 1	570
July	1st to 10th	Night	8% 2 17% 41% 28% 3	555
	11th to 20th	Night	11% 1 20% 40% 26% 3	552
	21st to end	Night	6% 3 19% 47% 23% 2	624
August	1st to 10th	Night	8% 1 16% 46% 27% 2	567
	11th to 20th	Night	9% 2 17% 39% 28% 5%	564
	21st to end	Night	12% 2 18% 38% 27% 3	627
September	1st to 10th	Night	11% 3 20% 37% 25% 4	631
	11th to 20th	Night	12% 4 16% 37% 27% 4	760
	21st to end	Night	17% 7% 23% 29% 19% 5%	760
October	1st to 10th	Night	18% 6% 24% 33% 17% 2	760
	11th to 20th	Night	23% 12% 28% 28% 8% 1	760
	21st to end	Night	24% 10% 34% 24% 7%	836
November	1st to 10th	Night	19% 11% 29% 30% 10% 1	743
	11th to 20th	Night	20% 15% 36% 22% 7%	760
	21st to end	Night	25% 11% 34% 26% 4	760
December	1st to 10th	Night	25% 14% 36% 20% 6%	798
	11th to 20th	Night	24% 12% 38% 23% 3	950
	21st to end	Night	32% 11% 35% 20% 2	1045

Page generated at 2024-10-29 11:20:47. Version ac07

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