Marietta
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Marietta clear sky chart from 2005-11-06 to 2024-11-05.

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% 6% 2 6% 4 4 5% 4 6% 8% 40%	100958
	Night	13% 7% 2 6% 4 4 4 4 6% 7% 43%	98039
Transparency	Day	39% 7% 11% 20% 18% 5%	104788
	Night	37% 6% 10% 20% 21% 7%	102335
Seeing	Day	16% 10% 22% 22% 19% 10%	14845
	Night	16% 8% 23% 29% 21% 4	24846

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	18% 11% 3 6% 3 3 5% 4 5% 6% 37%	2836
	11th to 20th	Day	13% 7% 2 5% 3 4 5% 3 4 5% 49%	2840
	21st to end	Day	25% 10% 2 6% 3 3 3 2 4 5% 37%	3285
February	1st to 10th	Day	17% 9% 3 6% 4 4 5% 3 5% 7% 38%	1900
	11th to 20th	Day	21% 8% 2 6% 4 2 4 4 5% 5% 40%	1848
	21st to end	Day	22% 7% 2 6% 4 4 3 4 5% 5% 38%	1570
March	1st to 10th	Day	23% 12% 3 6% 4 3 3 3 5% 5% 33%	3184
	11th to 20th	Day	13% 6% 2 6% 4 4 4 3 5% 7% 45%	3480
	21st to end	Day	17% 5% 3 6% 5% 4 4 4 6% 7% 38%	3815
April	1st to 10th	Day	12% 5% 3 6% 5% 4 4 4 6% 6% 45%	2171
	11th to 20th	Day	11% 6% 2 7% 4 4 4 3 6% 6% 47%	2254
	21st to end	Day	10% 5% 1 5% 4 4 4 4 7% 7% 49%	2413
May	1st to 10th	Day	10% 6% 2 7% 5% 4 4 4 6% 9% 42%	4082
	11th to 20th	Day	16% 8% 3 7% 4 4 5% 4 6% 8% 35%	4081
	21st to end	Day	8% 5% 2 6% 4 4 5% 4 7% 10% 44%	4476
June	1st to 10th	Day	10% 7% 3 8% 5% 5% 6% 5% 7% 10% 35%	2470
	11th to 20th	Day	5% 3 1 4 4 5% 6% 6% 10% 12% 44%	2470
	21st to end	Day	7% 5% 2 7% 6% 6% 6% 6% 8% 10% 38%	2470
July	1st to 10th	Day	8% 6% 2 7% 7% 7% 8% 7% 10% 12% 26%	4120
	11th to 20th	Day	8% 5% 3 6% 7% 7% 7% 6% 8% 11% 33%	4120
	21st to end	Day	10% 9% 4 10% 7% 8% 8% 6% 9% 10% 19%	4466
August	1st to 10th	Day	5% 5% 2 7% 5% 6% 6% 6% 9% 13% 38%	4104
	11th to 20th	Day	7% 5% 2 6% 4 5% 5% 4 7% 11% 44%	3738
	21st to end	Day	7% 4 2 5% 4 4 4 4 8% 9% 49%	4180
September	1st to 10th	Day	10% 6% 2 7% 5% 4 5% 4 7% 8% 41%	2112
	11th to 20th	Day	14% 7% 3 6% 4 4 5% 4 5% 8% 41%	2090
	21st to end	Day	14% 5% 2 5% 4 4 5% 4 5% 6% 48%	2090
October	1st to 10th	Day	12% 5% 2 4 2 3 3 3 4 6% 55%	2090
	11th to 20th	Day	11% 5% 1 4 3 3 3 3 5% 6% 56%	2003
	21st to end	Day	13% 6% 2 5% 3 3 3 2 4 5% 55%	2085
November	1st to 10th	Day	12% 6% 2 4 4 3 3 2 5% 6% 53%	1708
	11th to 20th	Day	13% 5% 2 5% 3 4 3 3 5% 5% 52%	1710
	21st to end	Day	14% 5% 2 6% 4 3 4 4 5% 7% 45%	1710
December	1st to 10th	Day	20% 7% 3 6% 4 4 4 3 5% 6% 37%	1710
	11th to 20th	Day	16% 8% 3 7% 5% 4 3 3 4 6% 41%	2153
	21st to end	Day	21% 8% 4 6% 4 4 4 3 5% 6% 35%	3124
January	1st to 10th	Night	19% 8% 3 6% 3 4 4 3 5% 6% 40%	4109
	11th to 20th	Night	13% 9% 3 6% 4 4 4 3 4 5% 46%	4120
	21st to end	Night	24% 12% 3 5% 3 3 2 2 3 4 39%	4368
February	1st to 10th	Night	15% 8% 3 5% 4 4 4 3 6% 6% 42%	2280
	11th to 20th	Night	21% 7% 2 6% 4 3 3 3 3 5% 42%	2218
	21st to end	Night	20% 7% 2 7% 4 3 4 3 4 6% 39%	1884
March	1st to 10th	Night	23% 10% 3 6% 4 4 3 3 4 5% 35%	3654
	11th to 20th	Night	11% 6% 2 5% 3 3 4 4 6% 8% 49%	3480
	21st to end	Night	16% 6% 2 7% 5% 4 4 3 5% 6% 42%	3817
April	1st to 10th	Night	12% 5% 2 5% 4 4 5% 4 6% 6% 47%	2024
	11th to 20th	Night	13% 6% 2 4 3 4 4 3 6% 7% 49%	1875
	21st to end	Night	9% 5% 2 5% 3 4 3 4 6% 8% 52%	1767
May	1st to 10th	Night	9% 7% 2 8% 6% 5% 5% 4 6% 8% 41%	2813
	11th to 20th	Night	14% 8% 3 7% 4 4 4 4 6% 8% 38%	2812
	21st to end	Night	5% 5% 2 6% 4 4 5% 4 8% 11% 46%	3079
June	1st to 10th	Night	7% 5% 2 7% 5% 6% 5% 7% 9% 12% 36%	1710
	11th to 20th	Night	4 3 2 5% 5% 5% 5% 5% 8% 12% 45%	1710
	21st to end	Night	6% 4 2 7% 4 5% 5% 5% 8% 11% 43%	1710
July	1st to 10th	Night	8% 7% 4 9% 8% 5% 6% 6% 9% 10% 30%	2840
	11th to 20th	Night	5% 5% 2 7% 5% 7% 7% 6% 10% 13% 34%	2840
	21st to end	Night	11% 9% 4 10% 6% 7% 7% 5% 8% 10% 23%	3087
August	1st to 10th	Night	6% 4 2 6% 5% 6% 5% 6% 8% 13% 39%	2825
	11th to 20th	Night	7% 6% 3 6% 5% 4 4 3 6% 8% 48%	3087
	21st to end	Night	8% 5% 2 5% 4 4 4 3 5% 8% 51%	3476
September	1st to 10th	Night	8% 5% 2 7% 5% 5% 6% 4 6% 10% 42%	2047
	11th to 20th	Night	13% 7% 2 6% 4 4 5% 4 6% 7% 44%	2090
	21st to end	Night	12% 5% 1 5% 4 4 4 3 5% 6% 49%	2090
October	1st to 10th	Night	10% 4 2 4 3 3 4 3 5% 7% 56%	2090
	11th to 20th	Night	11% 5% 2 5% 4 3 3 3 3 5% 59%	2175
	21st to end	Night	12% 5% 2 4 3 3 3 3 4 5% 57%	2508
November	1st to 10th	Night	12% 5% 1 4 4 3 3 3 4 5% 56%	2470
	11th to 20th	Night	12% 6% 2 5% 3 3 3 2 4 6% 53%	2470
	21st to end	Night	15% 6% 2 4 4 4 4 4 5% 7% 46%	2470
December	1st to 10th	Night	17% 7% 3 6% 5% 4 4 4 5% 6% 40%	2470
	11th to 20th	Night	17% 8% 2 5% 3 3 3 3 4 6% 47%	3042
	21st to end	Night	19% 9% 3 7% 5% 4 4 4 5% 8% 33%	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	48% 3 7% 15% 21% 5%	2837
	11th to 20th	Day	37% 3 8% 24% 23% 5%	2840
	21st to end	Day	50% 3 4 17% 20% 5%	3285
February	1st to 10th	Day	46% 4 7% 18% 20% 4	1900
	11th to 20th	Day	46% 4 6% 18% 20% 6%	1858
	21st to end	Day	47% 4 8% 14% 19% 8%	1570
March	1st to 10th	Day	53% 4 9% 12% 13% 9%	3184
	11th to 20th	Day	38% 5% 8% 17% 24% 8%	3480
	21st to end	Day	44% 5% 9% 20% 19% 4	3815
April	1st to 10th	Day	38% 6% 10% 22% 19% 6%	2171
	11th to 20th	Day	37% 5% 8% 19% 24% 7%	2254
	21st to end	Day	32% 5% 11% 28% 21% 3	2413
May	1st to 10th	Day	36% 7% 13% 23% 18% 2	4120
	11th to 20th	Day	44% 8% 12% 24% 11% 1	4085
	21st to end	Day	32% 8% 13% 26% 19% 2	4489
June	1st to 10th	Day	41% 9% 16% 22% 10% 2	2470
	11th to 20th	Day	28% 10% 20% 28% 13% 1	2470
	21st to end	Day	36% 9% 17% 23% 12% 3	2470
July	1st to 10th	Day	42% 14% 20% 18% 5% 1	4055
	11th to 20th	Day	40% 13% 20% 20% 6% 1	4051
	21st to end	Day	56% 13% 13% 13% 4	4324
August	1st to 10th	Day	33% 10% 14% 33% 10%	4091
	11th to 20th	Day	32% 9% 15% 26% 14% 2	3774
	21st to end	Day	29% 8% 15% 24% 21% 3	4179
September	1st to 10th	Day	38% 9% 15% 17% 18% 4	2112
	11th to 20th	Day	40% 8% 10% 19% 21% 2	2090
	21st to end	Day	36% 6% 10% 18% 23% 7%	2090
October	1st to 10th	Day	25% 3 6% 13% 39% 14%	3480
	11th to 20th	Day	20% 3 5% 16% 30% 26%	3308
	21st to end	Day	27% 3 5% 22% 31% 12%	3411
November	1st to 10th	Day	33% 3 7% 15% 31% 10%	1708
	11th to 20th	Day	35% 3 7% 18% 27% 10%	1710
	21st to end	Day	39% 5% 6% 19% 25% 6%	1710
December	1st to 10th	Day	47% 5% 6% 20% 17% 5%	1710
	11th to 20th	Day	46% 3 5% 16% 23% 7%	2150
	21st to end	Day	48% 4 9% 18% 18% 3	3124
January	1st to 10th	Night	43% 5% 6% 17% 25% 4	4109
	11th to 20th	Night	40% 3 6% 23% 20% 7%	4120
	21st to end	Night	51% 2 4 12% 25% 6%	4368
February	1st to 10th	Night	42% 4 8% 18% 20% 8%	2280
	11th to 20th	Night	46% 3 6% 17% 21% 8%	2219
	21st to end	Night	47% 4 6% 16% 17% 9%	1884
March	1st to 10th	Night	50% 5% 9% 15% 14% 7%	3654
	11th to 20th	Night	32% 5% 9% 16% 26% 11%	3480
	21st to end	Night	42% 4 7% 20% 20% 7%	3817
April	1st to 10th	Night	36% 5% 9% 20% 24% 7%	2024
	11th to 20th	Night	34% 4 8% 19% 24% 10%	1875
	21st to end	Night	30% 5% 10% 29% 21% 5%	1767
May	1st to 10th	Night	36% 10% 13% 22% 16% 2	2840
	11th to 20th	Night	41% 8% 13% 26% 12% 1	2813
	21st to end	Night	27% 8% 15% 26% 20% 3	3087
June	1st to 10th	Night	36% 13% 16% 20% 13% 2	1710
	11th to 20th	Night	28% 10% 22% 25% 14% 2	1710
	21st to end	Night	31% 11% 19% 20% 15% 4	1710
July	1st to 10th	Night	46% 11% 19% 18% 5% 1	2795
	11th to 20th	Night	36% 14% 20% 21% 7% 2	2786
	21st to end	Night	53% 13% 15% 13% 5% 1	2988
August	1st to 10th	Night	34% 9% 17% 31% 9% 1	2814
	11th to 20th	Night	33% 8% 14% 29% 16% 1	3117
	21st to end	Night	30% 8% 13% 20% 26% 3	3476
September	1st to 10th	Night	36% 10% 15% 18% 17% 5%	2047
	11th to 20th	Night	38% 9% 11% 21% 19% 3	2090
	21st to end	Night	34% 7% 10% 19% 21% 8%	2090
October	1st to 10th	Night	24% 3 8% 13% 38% 13%	3480
	11th to 20th	Night	18% 3 4 17% 34% 25%	3609
	21st to end	Night	23% 2 4 23% 31% 17%	4120
November	1st to 10th	Night	32% 3 8% 17% 28% 12%	2470
	11th to 20th	Night	33% 4 5% 18% 28% 12%	2470
	21st to end	Night	38% 4 6% 19% 26% 7%	2470
December	1st to 10th	Night	43% 6% 8% 19% 18% 5%	2470
	11th to 20th	Night	40% 3 7% 15% 28% 6%	3044
	21st to end	Night	49% 4 7% 20% 17% 2	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	24% 25% 37% 11% 3	270
	11th to 20th	Day	29% 19% 30% 15% 6% 1	270
	21st to end	Day	24% 26% 36% 11% 3 1	297
February	1st to 10th	Day	21% 22% 39% 14% 3	270
	11th to 20th	Day	37% 20% 27% 15% 1	270
	21st to end	Day	30% 22% 36% 11% 2	225
March	1st to 10th	Day	25% 18% 32% 18% 6%	308
	11th to 20th	Day	22% 17% 32% 21% 7% 1	460
	21st to end	Day	19% 20% 32% 22% 6% 1	506
April	1st to 10th	Day	19% 15% 30% 22% 13% 1	460
	11th to 20th	Day	12% 16% 33% 23% 13% 2	452
	21st to end	Day	16% 9% 27% 27% 18% 3	460
May	1st to 10th	Day	12% 11% 29% 27% 15% 6%	463
	11th to 20th	Day	14% 4 23% 29% 18% 12%	487
	21st to end	Day	13% 5% 16% 27% 25% 13%	529
June	1st to 10th	Day	13% 3 14% 26% 29% 13%	490
	11th to 20th	Day	6% 4 15% 25% 25% 26%	490
	21st to end	Day	9% 5% 13% 28% 27% 19%	490
July	1st to 10th	Day	9% 2 8% 23% 33% 25%	485
	11th to 20th	Day	9% 2 9% 17% 30% 33%	484
	21st to end	Day	8% 1 9% 20% 37% 25%	532
August	1st to 10th	Day	11% 2 14% 21% 28% 24%	486
	11th to 20th	Day	11% 4 9% 24% 32% 20%	479
	21st to end	Day	14% 1 10% 24% 28% 23%	539
September	1st to 10th	Day	11% 3 13% 25% 30% 18%	490
	11th to 20th	Day	18% 3 12% 22% 31% 12%	490
	21st to end	Day	16% 4 18% 22% 31% 10%	490
October	1st to 10th	Day	16% 3 21% 30% 22% 8%	490
	11th to 20th	Day	12% 10% 25% 24% 23% 6%	490
	21st to end	Day	17% 8% 22% 28% 20% 4	534
November	1st to 10th	Day	19% 9% 30% 22% 16% 5%	282
	11th to 20th	Day	16% 19% 36% 20% 7% 2	270
	21st to end	Day	9% 18% 39% 22% 11% 1	270
December	1st to 10th	Day	24% 24% 30% 17% 4 1	270
	11th to 20th	Day	23% 19% 32% 19% 6%	270
	21st to end	Day	31% 14% 35% 15% 5%	297
January	1st to 10th	Night	24% 17% 32% 21% 5% 1	760
	11th to 20th	Night	21% 16% 33% 23% 7%	760
	21st to end	Night	21% 16% 35% 24% 3	836
February	1st to 10th	Night	20% 12% 32% 30% 6%	760
	11th to 20th	Night	25% 15% 34% 24% 2	743
	21st to end	Night	23% 18% 34% 21% 3	628
March	1st to 10th	Night	18% 13% 35% 28% 5%	760
	11th to 20th	Night	17% 13% 35% 25% 10% 1	760
	21st to end	Night	18% 13% 29% 31% 9%	836
April	1st to 10th	Night	14% 12% 33% 28% 12% 1	694
	11th to 20th	Night	17% 10% 28% 31% 13% 1	563
	21st to end	Night	12% 7% 24% 38% 18% 2	570
May	1st to 10th	Night	10% 8% 25% 32% 24% 1	570
	11th to 20th	Night	12% 4 23% 33% 25% 4	561
	21st to end	Night	10% 2 15% 34% 33% 7%	617
June	1st to 10th	Night	9% 1 12% 37% 35% 6%	570
	11th to 20th	Night	4 2 14% 28% 39% 13%	570
	21st to end	Night	7% 2 8% 33% 41% 9%	570
July	1st to 10th	Night	8% 3 8% 24% 43% 14%	555
	11th to 20th	Night	7% 1 7% 18% 52% 16%	552
	21st to end	Night	8% 1 8% 25% 45% 12%	624
August	1st to 10th	Night	8% 2 7% 29% 44% 11%	567
	11th to 20th	Night	11% 2 9% 26% 44% 8%	564
	21st to end	Night	14% 2 8% 27% 39% 10%	627
September	1st to 10th	Night	10% 1 11% 27% 40% 11%	717
	11th to 20th	Night	17% 2 11% 28% 37% 5%	760
	21st to end	Night	16% 2 13% 33% 34% 3	760
October	1st to 10th	Night	10% 5% 20% 32% 25% 7%	760
	11th to 20th	Night	13% 6% 25% 32% 22% 3	760
	21st to end	Night	14% 8% 22% 35% 19% 3	836
November	1st to 10th	Night	14% 7% 23% 34% 21% 2	760
	11th to 20th	Night	16% 11% 30% 28% 13% 2	760
	21st to end	Night	19% 10% 27% 30% 13%	760
December	1st to 10th	Night	20% 14% 30% 28% 8% 1	760
	11th to 20th	Night	23% 10% 30% 28% 9% 1	760
	21st to end	Night	28% 12% 27% 27% 6%	836

Page generated at 2024-11-03 02:11:29. Version ac07

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