Sparta
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sparta 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	16% 8% 3 6% 4 4 4 4 6% 7% 38%	100812
	Night	15% 8% 3 6% 4 4 4 3 5% 7% 41%	97962
Transparency	Day	44% 7% 11% 21% 15% 3	100621
	Night	43% 6% 10% 22% 16% 3	97822
Seeing	Day	19% 11% 22% 22% 17% 9%	14619
	Night	18% 9% 20% 30% 20% 3	24617

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	17% 14% 5% 10% 4 4 5% 4 5% 5% 27%	2836
	11th to 20th	Day	23% 12% 5% 11% 4 4 3 2 4 4 29%	2840
	21st to end	Day	27% 12% 6% 5% 3 3 3 3 4 5% 30%	3266
February	1st to 10th	Day	22% 12% 4 8% 4 3 3 3 4 4 33%	1900
	11th to 20th	Day	22% 10% 4 8% 4 4 3 3 4 5% 31%	1848
	21st to end	Day	24% 10% 3 6% 4 4 3 3 4 5% 32%	1570
March	1st to 10th	Day	25% 11% 3 6% 4 3 3 3 5% 6% 31%	3120
	11th to 20th	Day	16% 8% 3 6% 3 4 3 2 4 5% 46%	3443
	21st to end	Day	16% 9% 2 6% 4 4 5% 4 5% 5% 39%	3834
April	1st to 10th	Day	16% 6% 3 6% 5% 4 4 3 5% 6% 41%	2280
	11th to 20th	Day	17% 8% 2 5% 4 4 4 3 5% 6% 43%	2254
	21st to end	Day	17% 6% 2 5% 5% 4 6% 3 5% 7% 39%	2399
May	1st to 10th	Day	20% 7% 2 6% 4 5% 4 4 6% 7% 34%	4082
	11th to 20th	Day	19% 8% 3 7% 4 4 4 4 5% 6% 34%	4081
	21st to end	Day	14% 6% 2 7% 5% 5% 5% 4 6% 8% 39%	4476
June	1st to 10th	Day	12% 6% 3 6% 5% 5% 5% 5% 6% 9% 39%	2470
	11th to 20th	Day	6% 5% 2 5% 5% 5% 6% 5% 8% 9% 44%	2470
	21st to end	Day	8% 5% 2 6% 5% 6% 5% 6% 8% 12% 37%	2470
July	1st to 10th	Day	8% 5% 2 7% 6% 5% 6% 6% 9% 11% 35%	4120
	11th to 20th	Day	12% 6% 3 6% 5% 5% 6% 5% 7% 9% 37%	4120
	21st to end	Day	19% 10% 4 10% 6% 6% 6% 5% 6% 7% 20%	4466
August	1st to 10th	Day	8% 4 2 5% 4 5% 5% 5% 7% 11% 44%	4104
	11th to 20th	Day	9% 4 2 6% 6% 6% 6% 5% 7% 12% 37%	3729
	21st to end	Day	7% 4 2 5% 4 5% 5% 5% 7% 9% 46%	4180
September	1st to 10th	Day	14% 5% 2 6% 5% 5% 5% 4 6% 7% 39%	2182
	11th to 20th	Day	15% 6% 3 6% 5% 4 5% 4 5% 6% 41%	2090
	21st to end	Day	15% 6% 2 5% 4 4 3 3 5% 6% 46%	2090
October	1st to 10th	Day	11% 4 2 5% 3 4 3 3 5% 6% 53%	2090
	11th to 20th	Day	14% 5% 2 4 3 3 3 3 4 6% 52%	2028
	21st to end	Day	17% 6% 1 5% 3 4 3 4 4 6% 47%	1895
November	1st to 10th	Day	12% 6% 1 4 2 3 4 3 5% 5% 55%	1672
	11th to 20th	Day	14% 7% 3 5% 3 3 4 3 5% 6% 47%	1710
	21st to end	Day	17% 9% 3 5% 4 3 4 3 5% 5% 43%	1710
December	1st to 10th	Day	23% 12% 4 7% 4 3 4 2 4 5% 32%	1710
	11th to 20th	Day	18% 13% 3 7% 4 4 4 4 6% 5% 33%	2153
	21st to end	Day	18% 15% 5% 7% 3 4 4 3 5% 7% 29%	3124
January	1st to 10th	Night	20% 17% 5% 6% 3 3 3 3 3 6% 33%	4109
	11th to 20th	Night	23% 12% 4 6% 5% 5% 3 2 3 4 33%	4120
	21st to end	Night	25% 14% 3 6% 4 3 3 2 3 4 33%	4372
February	1st to 10th	Night	21% 10% 3 8% 5% 4 4 3 4 6% 32%	2280
	11th to 20th	Night	24% 10% 4 7% 4 4 4 2 4 4 33%	2218
	21st to end	Night	26% 12% 3 7% 4 3 3 3 5% 5% 30%	1884
March	1st to 10th	Night	25% 12% 3 6% 4 4 4 3 4 5% 31%	3733
	11th to 20th	Night	15% 7% 2 5% 3 3 4 3 5% 6% 47%	3517
	21st to end	Night	16% 8% 3 7% 5% 5% 4 3 5% 5% 39%	3817
April	1st to 10th	Night	15% 6% 2 4 4 4 4 4 6% 7% 45%	1909
	11th to 20th	Night	17% 6% 2 5% 3 3 3 3 4 7% 47%	1875
	21st to end	Night	15% 8% 2 6% 4 3 3 3 6% 7% 44%	1781
May	1st to 10th	Night	17% 7% 3 6% 5% 5% 5% 4 6% 8% 36%	2813
	11th to 20th	Night	19% 8% 2 6% 5% 4 4 4 5% 7% 38%	2812
	21st to end	Night	9% 5% 2 6% 5% 5% 5% 5% 7% 9% 42%	3079
June	1st to 10th	Night	8% 6% 2 7% 5% 5% 4 4 6% 9% 43%	1710
	11th to 20th	Night	4 4 2 4 3 3 4 4 7% 13% 51%	1710
	21st to end	Night	6% 4 2 5% 5% 6% 5% 6% 8% 11% 42%	1710
July	1st to 10th	Night	8% 5% 3 6% 5% 5% 6% 5% 8% 11% 37%	2840
	11th to 20th	Night	10% 5% 2 5% 4 4 5% 4 7% 10% 44%	2840
	21st to end	Night	12% 10% 4 10% 7% 6% 7% 5% 6% 7% 25%	3087
August	1st to 10th	Night	6% 4 1 5% 4 4 5% 4 6% 10% 52%	2825
	11th to 20th	Night	9% 5% 2 6% 4 4 5% 5% 6% 10% 45%	3095
	21st to end	Night	5% 3 2 3 3 4 4 4 6% 9% 57%	3476
September	1st to 10th	Night	11% 5% 3 7% 4 4 4 4 5% 6% 47%	1977
	11th to 20th	Night	11% 7% 2 6% 5% 4 5% 3 5% 7% 45%	2090
	21st to end	Night	11% 5% 2 5% 3 3 3 3 6% 6% 53%	2090
October	1st to 10th	Night	11% 4 1 4 3 3 2 3 4 6% 59%	2090
	11th to 20th	Night	17% 5% 2 5% 3 3 3 3 4 5% 51%	2151
	21st to end	Night	16% 7% 2 4 2 3 3 3 4 5% 50%	2562
November	1st to 10th	Night	13% 6% 2 4 4 3 3 3 4 5% 52%	2406
	11th to 20th	Night	14% 9% 2 4 3 3 3 3 5% 7% 48%	2470
	21st to end	Night	18% 8% 3 5% 3 2 3 3 4 6% 43%	2470
December	1st to 10th	Night	23% 13% 4 6% 4 4 4 3 4 5% 31%	2470
	11th to 20th	Night	19% 12% 4 8% 3 3 3 2 4 5% 38%	3042
	21st to end	Night	17% 16% 5% 8% 5% 5% 5% 4 5% 7% 25%	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	56% 6% 6% 16% 14% 2	2837
	11th to 20th	Day	59% 5% 5% 12% 17% 1	2840
	21st to end	Day	57% 4 7% 19% 12% 1	3266
February	1st to 10th	Day	56% 4 6% 15% 17% 2	1900
	11th to 20th	Day	55% 4 7% 17% 14% 3	1858
	21st to end	Day	54% 4 8% 13% 16% 5%	1570
March	1st to 10th	Day	54% 5% 6% 16% 12% 7%	3120
	11th to 20th	Day	41% 4 8% 23% 17% 6%	3443
	21st to end	Day	46% 5% 8% 25% 14% 1	3834
April	1st to 10th	Day	43% 6% 10% 21% 17% 3	2280
	11th to 20th	Day	42% 5% 8% 20% 23% 3	2254
	21st to end	Day	44% 5% 10% 26% 14% 1	2399
May	1st to 10th	Day	47% 8% 11% 23% 11% 1	4120
	11th to 20th	Day	50% 7% 12% 22% 9%	4085
	21st to end	Day	42% 8% 11% 21% 17% 2	4489
June	1st to 10th	Day	41% 9% 14% 22% 13% 2	2470
	11th to 20th	Day	33% 9% 18% 23% 15% 2	2470
	21st to end	Day	36% 10% 18% 19% 13% 3	2470
July	1st to 10th	Day	38% 12% 20% 20% 8% 2	4055
	11th to 20th	Day	41% 8% 18% 25% 7% 2	4051
	21st to end	Day	60% 9% 10% 15% 5% 1	4324
August	1st to 10th	Day	31% 9% 16% 32% 12% 1	4091
	11th to 20th	Day	37% 8% 17% 24% 13% 1	3765
	21st to end	Day	32% 8% 13% 31% 15% 1	4179
September	1st to 10th	Day	42% 8% 11% 18% 16% 5%	2182
	11th to 20th	Day	43% 6% 12% 20% 17% 2	2090
	21st to end	Day	38% 6% 12% 21% 18% 4	2090
October	1st to 10th	Day	32% 6% 9% 21% 26% 7%	2090
	11th to 20th	Day	33% 4 9% 21% 25% 8%	2028
	21st to end	Day	38% 5% 7% 21% 24% 6%	1895
November	1st to 10th	Day	31% 4 8% 24% 28% 5%	1672
	11th to 20th	Day	38% 4 6% 23% 23% 6%	1710
	21st to end	Day	43% 4 6% 22% 21% 4	1710
December	1st to 10th	Day	54% 5% 5% 20% 14% 3	1710
	11th to 20th	Day	52% 4 9% 16% 16% 2	2150
	21st to end	Day	54% 4 10% 19% 11% 3	3124
January	1st to 10th	Night	54% 4 6% 19% 16% 2	4109
	11th to 20th	Night	56% 4 6% 12% 17% 6%	4120
	21st to end	Night	56% 3 6% 14% 19% 2	4372
February	1st to 10th	Night	53% 4 8% 17% 15% 2	2280
	11th to 20th	Night	57% 3 6% 17% 13% 5%	2219
	21st to end	Night	56% 5% 7% 15% 13% 4	1884
March	1st to 10th	Night	55% 5% 8% 12% 15% 4	3733
	11th to 20th	Night	38% 5% 8% 25% 14% 11%	3517
	21st to end	Night	47% 5% 8% 24% 15% 1	3817
April	1st to 10th	Night	38% 6% 10% 24% 20% 3	1909
	11th to 20th	Night	37% 4 9% 21% 22% 6%	1875
	21st to end	Night	40% 5% 10% 29% 15% 1	1781
May	1st to 10th	Night	42% 11% 12% 23% 11% 1	2840
	11th to 20th	Night	45% 7% 13% 21% 12% 1	2813
	21st to end	Night	34% 10% 15% 25% 16% 1	3087
June	1st to 10th	Night	37% 7% 15% 27% 12% 2	1710
	11th to 20th	Night	22% 9% 22% 29% 15% 2	1710
	21st to end	Night	32% 11% 16% 25% 13% 4	1710
July	1st to 10th	Night	36% 11% 21% 23% 8% 1	2795
	11th to 20th	Night	32% 8% 18% 31% 8% 3	2786
	21st to end	Night	55% 11% 12% 15% 7% 1	2988
August	1st to 10th	Night	26% 7% 13% 37% 15% 1	2814
	11th to 20th	Night	32% 8% 21% 24% 13% 1	3125
	21st to end	Night	23% 7% 12% 39% 17% 1	3476
September	1st to 10th	Night	36% 8% 13% 21% 18% 5%	1977
	11th to 20th	Night	37% 7% 11% 21% 22% 2	2090
	21st to end	Night	32% 6% 11% 23% 24% 5%	2090
October	1st to 10th	Night	28% 4 7% 24% 27% 10%	2090
	11th to 20th	Night	36% 4 7% 21% 23% 8%	2151
	21st to end	Night	37% 3 6% 22% 25% 8%	2562
November	1st to 10th	Night	35% 4 6% 22% 25% 8%	2406
	11th to 20th	Night	37% 3 7% 20% 25% 8%	2470
	21st to end	Night	43% 4 6% 23% 20% 4	2470
December	1st to 10th	Night	56% 5% 6% 17% 14% 3	2470
	11th to 20th	Night	50% 3 7% 17% 20% 3	3044
	21st to end	Night	57% 6% 9% 16% 11% 1	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	28% 24% 32% 11% 3 1	270
	11th to 20th	Day	36% 26% 21% 13% 4	270
	21st to end	Day	26% 26% 37% 8% 3	297
February	1st to 10th	Day	30% 23% 30% 14% 3	270
	11th to 20th	Day	38% 24% 30% 6% 2	270
	21st to end	Day	39% 24% 31% 5% 1	225
March	1st to 10th	Day	28% 21% 35% 13% 3	270
	11th to 20th	Day	30% 20% 28% 17% 5% 1	436
	21st to end	Day	28% 18% 31% 16% 7%	506
April	1st to 10th	Day	24% 18% 26% 22% 9% 1	460
	11th to 20th	Day	23% 14% 30% 23% 8% 2	452
	21st to end	Day	24% 12% 28% 22% 12% 2	460
May	1st to 10th	Day	22% 12% 30% 20% 11% 5%	463
	11th to 20th	Day	17% 8% 25% 26% 15% 8%	487
	21st to end	Day	15% 8% 19% 28% 17% 14%	529
June	1st to 10th	Day	14% 6% 20% 26% 21% 14%	490
	11th to 20th	Day	7% 4 15% 31% 25% 18%	490
	21st to end	Day	10% 5% 19% 25% 24% 17%	490
July	1st to 10th	Day	14% 3 11% 25% 27% 21%	485
	11th to 20th	Day	13% 4 9% 24% 26% 24%	484
	21st to end	Day	14% 4 9% 26% 27% 20%	532
August	1st to 10th	Day	14% 4 11% 23% 29% 18%	486
	11th to 20th	Day	10% 4 15% 33% 29% 10%	479
	21st to end	Day	13% 3 9% 25% 28% 22%	539
September	1st to 10th	Day	14% 4 9% 24% 34% 15%	490
	11th to 20th	Day	16% 4 9% 29% 29% 14%	490
	21st to end	Day	16% 6% 16% 26% 29% 8%	490
October	1st to 10th	Day	13% 4 19% 33% 23% 8%	490
	11th to 20th	Day	15% 10% 26% 27% 17% 5%	490
	21st to end	Day	23% 10% 26% 25% 13% 3	382
November	1st to 10th	Day	19% 11% 31% 27% 10% 3	270
	11th to 20th	Day	17% 17% 36% 25% 5%	270
	21st to end	Day	21% 14% 38% 17% 8% 2	270
December	1st to 10th	Day	31% 17% 32% 14% 5% 1	270
	11th to 20th	Day	30% 16% 29% 17% 7% 1	270
	21st to end	Day	29% 19% 31% 18% 2 1	297
January	1st to 10th	Night	25% 18% 29% 23% 5%	760
	11th to 20th	Night	31% 19% 24% 22% 5%	760
	21st to end	Night	24% 16% 31% 26% 3	836
February	1st to 10th	Night	25% 14% 32% 26% 3	760
	11th to 20th	Night	29% 17% 31% 20% 2	743
	21st to end	Night	32% 18% 27% 20% 2	628
March	1st to 10th	Night	25% 14% 30% 27% 4	760
	11th to 20th	Night	25% 14% 28% 24% 7% 1	760
	21st to end	Night	21% 14% 28% 28% 8%	836
April	1st to 10th	Night	18% 10% 29% 31% 11%	579
	11th to 20th	Night	20% 9% 30% 30% 11% 1	563
	21st to end	Night	20% 6% 26% 34% 12% 1	570
May	1st to 10th	Night	16% 6% 25% 33% 18% 2	570
	11th to 20th	Night	14% 5% 18% 36% 23% 4	561
	21st to end	Night	8% 3 13% 37% 33% 6%	617
June	1st to 10th	Night	9% 3 12% 37% 35% 5%	570
	11th to 20th	Night	3 2 11% 36% 38% 10%	570
	21st to end	Night	6% 2 8% 38% 37% 8%	570
July	1st to 10th	Night	11% 3 5% 26% 46% 10%	555
	11th to 20th	Night	9% 2 7% 27% 43% 12%	552
	21st to end	Night	9% 3 5% 30% 44% 10%	624
August	1st to 10th	Night	9% 1 5% 27% 49% 9%	567
	11th to 20th	Night	9% 2 6% 35% 43% 5%	564
	21st to end	Night	10% 2 5% 27% 49% 8%	627
September	1st to 10th	Night	12% 2 7% 33% 38% 8%	647
	11th to 20th	Night	14% 2 11% 32% 35% 6%	760
	21st to end	Night	13% 4 13% 34% 31% 6%	760
October	1st to 10th	Night	12% 5% 15% 33% 27% 8%	760
	11th to 20th	Night	19% 6% 22% 32% 19% 2	760
	21st to end	Night	19% 9% 22% 33% 16% 2	812
November	1st to 10th	Night	15% 7% 21% 37% 17% 2	740
	11th to 20th	Night	18% 12% 26% 31% 10% 2	760
	21st to end	Night	23% 11% 24% 30% 11% 1	760
December	1st to 10th	Night	28% 14% 24% 26% 8%	760
	11th to 20th	Night	25% 13% 24% 29% 7% 1	760
	21st to end	Night	27% 17% 25% 27% 5%	836

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

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