Marion
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Marion clear sky chart from 2005-11-06 to 2025-01-22.

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% 7% 3 6% 4 4 4 4 5% 7% 43%	104939
	Night	14% 7% 3 6% 4 4 4 3 5% 6% 44%	104497
Transparency	Day	39% 5% 11% 25% 17% 3	108583
	Night	39% 5% 10% 24% 19% 4	108981
Seeing	Day	16% 9% 25% 25% 18% 8%	15757
	Night	17% 9% 26% 30% 15% 2	25667

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	13% 12% 5% 9% 4 5% 4 3 4 5% 36%	2607
	11th to 20th	Day	17% 8% 3 6% 5% 4 5% 3 5% 6% 37%	2709
	21st to end	Day	24% 16% 4 8% 4 3 3 3 3 4 28%	3144
February	1st to 10th	Day	15% 12% 4 7% 4 4 4 4 4 6% 36%	1828
	11th to 20th	Day	16% 9% 4 7% 4 4 5% 2 4 6% 37%	1848
	21st to end	Day	15% 10% 4 8% 4 5% 4 3 5% 6% 37%	1570
March	1st to 10th	Day	20% 13% 3 7% 4 3 4 2 3 6% 35%	3120
	11th to 20th	Day	14% 8% 2 5% 3 3 4 3 4 6% 49%	3342
	21st to end	Day	13% 8% 3 7% 5% 5% 4 4 5% 6% 39%	4149
April	1st to 10th	Day	11% 6% 2 6% 5% 4 4 3 5% 9% 45%	2280
	11th to 20th	Day	15% 8% 2 7% 3 4 5% 3 5% 6% 41%	2254
	21st to end	Day	18% 7% 3 5% 4 4 4 4 5% 6% 40%	2280
May	1st to 10th	Day	15% 7% 2 7% 5% 5% 6% 5% 7% 9% 32%	3983
	11th to 20th	Day	18% 7% 2 6% 4 4 4 4 5% 8% 37%	4081
	21st to end	Day	11% 6% 2 6% 5% 5% 4 4 6% 7% 42%	4792
June	1st to 10th	Day	10% 4 2 5% 4 4 4 4 6% 9% 46%	2660
	11th to 20th	Day	6% 4 2 5% 5% 5% 4 4 5% 10% 50%	2660
	21st to end	Day	6% 4 1 5% 5% 4 5% 5% 7% 11% 46%	2660
July	1st to 10th	Day	12% 5% 2 5% 4 5% 5% 4 6% 10% 42%	4440
	11th to 20th	Day	5% 3 2 5% 4 5% 5% 4 7% 11% 50%	4440
	21st to end	Day	8% 6% 3 9% 5% 7% 7% 5% 8% 9% 33%	4726
August	1st to 10th	Day	6% 3 2 5% 3 4 4 3 6% 9% 55%	3855
	11th to 20th	Day	10% 5% 2 6% 5% 5% 5% 4 7% 10% 42%	3729
	21st to end	Day	6% 4 1 4 4 3 4 3 6% 9% 56%	4180
September	1st to 10th	Day	12% 5% 2 6% 4 4 4 3 4 7% 49%	2280
	11th to 20th	Day	8% 6% 2 6% 4 4 5% 4 5% 7% 48%	2180
	21st to end	Day	11% 5% 2 4 3 3 3 3 5% 7% 53%	2090
October	1st to 10th	Day	10% 3 2 5% 3 2 3 3 5% 6% 59%	2028
	11th to 20th	Day	12% 5% 2 5% 3 3 4 3 5% 7% 52%	1900
	21st to end	Day	18% 7% 2 5% 3 3 4 3 4 5% 47%	1997
November	1st to 10th	Day	10% 5% 2 5% 3 4 4 3 5% 5% 53%	1762
	11th to 20th	Day	13% 8% 3 6% 5% 4 4 3 4 6% 46%	1800
	21st to end	Day	18% 10% 2 5% 4 3 3 3 5% 5% 42%	1800
December	1st to 10th	Day	10% 10% 2 6% 3 3 3 2 4 6% 50%	2775
	11th to 20th	Day	13% 10% 5% 8% 4 5% 5% 3 5% 6% 37%	3008
	21st to end	Day	25% 15% 4 9% 4 4 3 3 4 5% 25%	3982
January	1st to 10th	Night	17% 10% 3 7% 4 4 4 3 5% 6% 36%	4568
	11th to 20th	Night	14% 11% 4 9% 5% 5% 6% 3 4 5% 34%	4479
	21st to end	Night	24% 13% 6% 7% 4 3 3 2 4 5% 29%	4546
February	1st to 10th	Night	18% 12% 5% 8% 5% 4 3 3 4 5% 33%	2349
	11th to 20th	Night	15% 8% 3 8% 5% 3 4 3 5% 5% 42%	2218
	21st to end	Night	18% 9% 3 8% 4 4 4 3 5% 4 38%	1884
March	1st to 10th	Night	22% 9% 2 7% 3 3 4 3 4 5% 38%	3733
	11th to 20th	Night	13% 6% 2 6% 3 3 4 2 5% 6% 50%	3647
	21st to end	Night	16% 7% 2 7% 5% 4 4 4 5% 7% 39%	3480
April	1st to 10th	Night	12% 5% 2 6% 4 4 4 3 4 8% 48%	1900
	11th to 20th	Night	16% 6% 2 5% 4 4 3 4 5% 6% 45%	1875
	21st to end	Night	18% 7% 2 6% 4 4 4 4 6% 6% 39%	1900
May	1st to 10th	Night	17% 7% 2 6% 5% 3 4 3 5% 8% 39%	2912
	11th to 20th	Night	16% 7% 2 5% 5% 4 4 4 4 6% 44%	2812
	21st to end	Night	9% 4 2 7% 5% 4 5% 4 6% 9% 44%	2759
June	1st to 10th	Night	10% 4 2 5% 4 4 5% 4 6% 9% 48%	1520
	11th to 20th	Night	5% 3 1 4 3 3 4 5% 5% 10% 55%	1520
	21st to end	Night	4 3 1 4 4 5% 4 4 8% 11% 52%	1520
July	1st to 10th	Night	12% 4 2 5% 4 4 4 3 6% 8% 50%	2530
	11th to 20th	Night	6% 3 2 4 4 4 3 3 6% 8% 58%	2530
	21st to end	Night	7% 7% 2 9% 6% 5% 5% 5% 9% 10% 36%	2833
August	1st to 10th	Night	5% 3 1 4 3 3 4 3 6% 8% 59%	3073
	11th to 20th	Night	8% 4 2 5% 4 4 4 4 5% 8% 52%	3100
	21st to end	Night	4 3 1 5% 3 3 4 3 6% 10% 59%	3476
September	1st to 10th	Night	10% 5% 2 6% 4 3 4 2 4 6% 53%	1900
	11th to 20th	Night	8% 5% 2 6% 3 4 3 3 6% 8% 52%	1981
	21st to end	Night	12% 5% 1 4 3 3 4 3 4 7% 53%	2090
October	1st to 10th	Night	7% 3 2 4 3 3 3 3 4 6% 60%	2147
	11th to 20th	Night	13% 5% 2 5% 3 3 3 2 3 6% 56%	2280
	21st to end	Night	19% 7% 2 6% 3 3 2 2 4 5% 48%	2599
November	1st to 10th	Night	11% 5% 1 5% 3 3 2 3 5% 6% 56%	2536
	11th to 20th	Night	12% 6% 2 5% 3 3 4 3 5% 6% 50%	2600
	21st to end	Night	17% 8% 3 6% 4 3 3 2 3 6% 46%	2600
December	1st to 10th	Night	16% 9% 3 7% 3 3 3 2 4 5% 45%	4405
	11th to 20th	Night	15% 8% 3 5% 4 4 4 3 5% 5% 44%	5199
	21st to end	Night	24% 13% 4 8% 5% 4 4 3 4 5% 27%	6996

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	51% 3 10% 25% 9% 2	2608
	11th to 20th	Day	46% 4 11% 22% 15% 1	2709
	21st to end	Day	60% 3 8% 18% 9% 1	3144
February	1st to 10th	Day	49% 5% 10% 22% 12% 1	1828
	11th to 20th	Day	49% 4 9% 20% 14% 4	1858
	21st to end	Day	49% 4 10% 19% 13% 5%	1570
March	1st to 10th	Day	53% 4 6% 19% 13% 5%	3120
	11th to 20th	Day	38% 4 9% 28% 16% 5%	3342
	21st to end	Day	43% 6% 15% 22% 13% 1	4149
April	1st to 10th	Day	37% 4 13% 27% 18% 1	2280
	11th to 20th	Day	43% 5% 10% 23% 16% 3	2254
	21st to end	Day	45% 5% 11% 26% 12% 2	2280
May	1st to 10th	Day	45% 9% 13% 23% 9% 1	4019
	11th to 20th	Day	44% 7% 11% 25% 12% 1	4085
	21st to end	Day	39% 7% 12% 18% 23% 1	4805
June	1st to 10th	Day	34% 7% 13% 26% 18% 2	2660
	11th to 20th	Day	29% 7% 11% 27% 22% 3	2660
	21st to end	Day	31% 7% 16% 23% 17% 5%	2660
July	1st to 10th	Day	36% 6% 12% 26% 16% 2	4371
	11th to 20th	Day	26% 7% 12% 36% 16% 2	4365
	21st to end	Day	44% 9% 13% 23% 9% 1	4577
August	1st to 10th	Day	26% 6% 14% 32% 20% 1	3841
	11th to 20th	Day	35% 7% 13% 25% 18% 1	3765
	21st to end	Day	25% 5% 12% 36% 19% 3	4179
September	1st to 10th	Day	36% 4 9% 26% 19% 5%	2280
	11th to 20th	Day	34% 5% 9% 24% 25% 2	2180
	21st to end	Day	31% 5% 8% 25% 27% 4	2090
October	1st to 10th	Day	17% 2 5% 23% 46% 7%	3366
	11th to 20th	Day	23% 3 8% 23% 34% 8%	3140
	21st to end	Day	32% 3 5% 26% 29% 4	3274
November	1st to 10th	Day	34% 5% 9% 27% 19% 6%	1762
	11th to 20th	Day	40% 4 7% 23% 21% 6%	1800
	21st to end	Day	46% 3 8% 24% 16% 2	1800
December	1st to 10th	Day	37% 4 10% 33% 16% 1	2775
	11th to 20th	Day	50% 3 9% 24% 12% 2	3005
	21st to end	Day	62% 4 11% 14% 8% 1	3982
January	1st to 10th	Night	48% 5% 10% 26% 11% 1	4568
	11th to 20th	Night	52% 4 8% 22% 11% 2	4479
	21st to end	Night	58% 4 10% 18% 9% 1	4546
February	1st to 10th	Night	55% 3 8% 21% 12% 1	2349
	11th to 20th	Night	46% 4 8% 23% 17% 3	2219
	21st to end	Night	49% 5% 8% 18% 15% 4	1884
March	1st to 10th	Night	50% 4 8% 18% 17% 4	3733
	11th to 20th	Night	36% 6% 11% 22% 19% 6%	3647
	21st to end	Night	44% 6% 12% 27% 10% 1	3480
April	1st to 10th	Night	36% 5% 10% 27% 18% 3	1900
	11th to 20th	Night	39% 4 10% 23% 20% 5%	1875
	21st to end	Night	44% 6% 10% 24% 15% 3	1900
May	1st to 10th	Night	42% 9% 15% 24% 9% 1	2941
	11th to 20th	Night	41% 7% 12% 23% 15% 1	2813
	21st to end	Night	36% 7% 13% 25% 16% 2	2767
June	1st to 10th	Night	33% 5% 13% 23% 22% 3	1520
	11th to 20th	Night	24% 6% 12% 27% 25% 6%	1520
	21st to end	Night	23% 6% 18% 26% 18% 7%	1520
July	1st to 10th	Night	33% 6% 12% 27% 18% 4	2490
	11th to 20th	Night	24% 6% 12% 36% 18% 4	2482
	21st to end	Night	39% 10% 16% 23% 12% 1	2743
August	1st to 10th	Night	22% 6% 18% 34% 19% 1	3063
	11th to 20th	Night	30% 6% 13% 28% 20% 3	3130
	21st to end	Night	21% 5% 12% 37% 21% 3	3476
September	1st to 10th	Night	33% 5% 8% 27% 21% 7%	1900
	11th to 20th	Night	31% 5% 8% 29% 23% 5%	1981
	21st to end	Night	31% 5% 9% 23% 26% 6%	2090
October	1st to 10th	Night	16% 2 5% 16% 49% 11%	3576
	11th to 20th	Night	22% 3 5% 21% 43% 7%	3779
	21st to end	Night	31% 3 6% 25% 26% 10%	4272
November	1st to 10th	Night	30% 3 10% 25% 25% 6%	2536
	11th to 20th	Night	35% 4 7% 24% 23% 7%	2600
	21st to end	Night	42% 3 7% 24% 21% 2	2600
December	1st to 10th	Night	44% 3 8% 27% 18% 1	4405
	11th to 20th	Night	43% 3 11% 22% 19% 1	5201
	21st to end	Night	60% 4 10% 17% 7% 2	6996

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	25% 16% 33% 21% 4 1	300
	11th to 20th	Day	25% 23% 35% 14% 3	300
	21st to end	Day	23% 20% 39% 13% 5%	300
February	1st to 10th	Day	25% 16% 41% 13% 4	270
	11th to 20th	Day	28% 19% 38% 13% 2 1	270
	21st to end	Day	29% 22% 31% 14% 4	225
March	1st to 10th	Day	22% 16% 42% 17% 3	270
	11th to 20th	Day	27% 20% 36% 14% 3	270
	21st to end	Day	27% 16% 31% 19% 6% 1	490
April	1st to 10th	Day	19% 17% 32% 23% 7% 1	460
	11th to 20th	Day	23% 16% 26% 23% 11%	452
	21st to end	Day	22% 13% 32% 21% 10% 2	460
May	1st to 10th	Day	20% 11% 32% 24% 10% 3	463
	11th to 20th	Day	20% 8% 25% 26% 15% 6%	487
	21st to end	Day	12% 6% 25% 29% 19% 9%	715
June	1st to 10th	Day	13% 4 20% 26% 24% 14%	680
	11th to 20th	Day	6% 3 20% 34% 28% 9%	680
	21st to end	Day	7% 4 25% 34% 22% 9%	680
July	1st to 10th	Day	11% 3 11% 29% 25% 21%	671
	11th to 20th	Day	6% 2 15% 32% 29% 15%	668
	21st to end	Day	8% 3 14% 32% 31% 13%	739
August	1st to 10th	Day	7% 3 13% 31% 31% 16%	531
	11th to 20th	Day	13% 4 15% 28% 28% 11%	479
	21st to end	Day	9% 3 10% 27% 34% 17%	539
September	1st to 10th	Day	12% 3 11% 29% 30% 15%	490
	11th to 20th	Day	10% 2 10% 27% 35% 16%	490
	21st to end	Day	14% 7% 21% 24% 22% 11%	490
October	1st to 10th	Day	9% 4 21% 35% 22% 8%	428
	11th to 20th	Day	18% 10% 35% 23% 11% 4	300
	21st to end	Day	27% 12% 30% 23% 8%	330
November	1st to 10th	Day	15% 11% 34% 25% 12% 4	300
	11th to 20th	Day	17% 18% 30% 25% 9% 1	300
	21st to end	Day	29% 12% 29% 22% 7% 1	300
December	1st to 10th	Day	18% 16% 39% 15% 9% 3	300
	11th to 20th	Day	24% 15% 35% 19% 6%	300
	21st to end	Day	28% 18% 37% 15% 2 1	330
January	1st to 10th	Night	23% 18% 31% 25% 3	1000
	11th to 20th	Night	25% 19% 34% 17% 4	1000
	21st to end	Night	21% 14% 39% 23% 2	1051
February	1st to 10th	Night	25% 16% 33% 24% 2	829
	11th to 20th	Night	23% 17% 35% 23% 2	743
	21st to end	Night	26% 17% 36% 20% 2	628
March	1st to 10th	Night	22% 15% 34% 24% 4	760
	11th to 20th	Night	22% 13% 33% 25% 6%	672
	21st to end	Night	24% 12% 29% 28% 7%	627
April	1st to 10th	Night	16% 13% 36% 29% 7%	570
	11th to 20th	Night	20% 11% 29% 26% 13% 1	563
	21st to end	Night	22% 8% 31% 29% 9% 1	570
May	1st to 10th	Night	19% 5% 28% 35% 12% 1	570
	11th to 20th	Night	16% 5% 23% 35% 19% 2	561
	21st to end	Night	9% 3 20% 42% 23% 3	617
June	1st to 10th	Night	12% 2 16% 38% 29% 3	570
	11th to 20th	Night	6% 2 14% 49% 28% 2	570
	21st to end	Night	4 2 19% 44% 30% 2	570
July	1st to 10th	Night	10% 1 9% 32% 39% 10%	555
	11th to 20th	Night	5% 3 10% 41% 35% 7%	552
	21st to end	Night	7% 1 12% 38% 36% 6%	624
August	1st to 10th	Night	6% 4 8% 37% 40% 5%	567
	11th to 20th	Night	9% 2 9% 38% 36% 5%	564
	21st to end	Night	6% 2 7% 35% 41% 8%	627
September	1st to 10th	Night	11% 3 12% 31% 37% 6%	570
	11th to 20th	Night	9% 3 12% 31% 40% 5%	651
	21st to end	Night	13% 5% 18% 34% 23% 6%	760
October	1st to 10th	Night	10% 5% 17% 38% 25% 6%	760
	11th to 20th	Night	16% 6% 29% 30% 17% 2	760
	21st to end	Night	23% 8% 32% 27% 10% 1	836
November	1st to 10th	Night	14% 7% 34% 34% 11% 1	780
	11th to 20th	Night	16% 12% 31% 31% 10%	800
	21st to end	Night	23% 11% 31% 25% 10%	800
December	1st to 10th	Night	23% 12% 33% 27% 4 1	890
	11th to 20th	Night	23% 10% 33% 27% 6% 1	1000
	21st to end	Night	26% 12% 36% 22% 4	1100

Page generated at 2025-01-19 02:06:44. Version ac07

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