Deltona
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Deltona clear sky chart from 2005-11-06 to 2025-11-18.

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	8% 5% 2 7% 6% 6% 6% 5% 7% 10% 38%	126558
	Night	9% 6% 2 6% 5% 5% 5% 4 6% 9% 43%	123818
Transparency	Day	39% 7% 16% 20% 13% 5%	130253
	Night	37% 7% 16% 21% 14% 5%	128192
Seeing	Day	9% 6% 21% 26% 21% 17%	17037
	Night	9% 5% 19% 33% 27% 7%	27087

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	8% 5% 2 5% 3 4 4 3 4 8% 54%	4056
	11th to 20th	Day	19% 9% 3 8% 5% 5% 5% 4 5% 6% 32%	4060
	21st to end	Day	14% 6% 2 6% 4 3 3 3 5% 8% 46%	4489
February	1st to 10th	Day	12% 6% 3 6% 5% 5% 5% 4 6% 8% 41%	2000
	11th to 20th	Day	8% 5% 3 6% 4 4 4 4 5% 7% 51%	1948
	21st to end	Day	9% 5% 2 6% 6% 4 4 4 5% 7% 46%	1784
March	1st to 10th	Day	8% 6% 3 8% 5% 5% 5% 4 6% 10% 41%	4935
	11th to 20th	Day	5% 3 1 5% 3 4 3 3 5% 8% 60%	4980
	21st to end	Day	9% 6% 2 6% 4 4 5% 4 7% 9% 44%	5465
April	1st to 10th	Day	7% 3 2 5% 4 5% 5% 5% 7% 9% 48%	2200
	11th to 20th	Day	8% 6% 2 6% 4 5% 6% 5% 7% 9% 42%	2249
	21st to end	Day	5% 4 1 5% 5% 5% 5% 5% 7% 9% 49%	2400
May	1st to 10th	Day	4 3 2 5% 5% 6% 6% 5% 8% 11% 46%	5681
	11th to 20th	Day	9% 5% 2 6% 4 5% 5% 5% 6% 9% 44%	5861
	21st to end	Day	4 4 2 5% 5% 6% 7% 5% 7% 12% 44%	6433
June	1st to 10th	Day	10% 7% 2 10% 7% 8% 6% 6% 8% 10% 25%	2600
	11th to 20th	Day	7% 6% 3 9% 8% 8% 9% 7% 8% 9% 27%	2600
	21st to end	Day	8% 7% 3 9% 8% 7% 8% 6% 8% 8% 27%	2600
July	1st to 10th	Day	7% 6% 3 9% 8% 8% 8% 7% 11% 13% 19%	5900
	11th to 20th	Day	4 4 2 8% 7% 7% 8% 7% 10% 13% 29%	5900
	21st to end	Day	4 5% 3 7% 6% 7% 7% 6% 9% 12% 33%	6424
August	1st to 10th	Day	5% 7% 3 10% 7% 7% 7% 7% 9% 12% 25%	4234
	11th to 20th	Day	4 3 2 7% 7% 7% 7% 6% 9% 13% 33%	4047
	21st to end	Day	8% 6% 3 10% 7% 7% 9% 7% 9% 12% 23%	3961
September	1st to 10th	Day	8% 6% 3 11% 9% 9% 8% 7% 9% 10% 20%	2200
	11th to 20th	Day	10% 8% 4 10% 8% 8% 7% 6% 8% 10% 22%	2200
	21st to end	Day	10% 7% 3 10% 6% 8% 7% 5% 7% 9% 29%	2200
October	1st to 10th	Day	12% 6% 3 9% 7% 6% 6% 5% 7% 8% 31%	2145
	11th to 20th	Day	7% 5% 2 7% 5% 4 5% 5% 7% 9% 44%	2000
	21st to end	Day	8% 5% 2 5% 5% 4 6% 4 6% 8% 48%	2200
November	1st to 10th	Day	7% 5% 2 7% 6% 6% 5% 4 7% 8% 43%	2057
	11th to 20th	Day	8% 6% 2 7% 5% 6% 5% 5% 6% 7% 42%	2070
	21st to end	Day	10% 7% 2 7% 5% 4 5% 5% 5% 8% 43%	1910
December	1st to 10th	Day	5% 4 2 4 3 4 4 4 7% 8% 55%	2930
	11th to 20th	Day	9% 7% 3 8% 5% 6% 6% 4 7% 8% 36%	3373
	21st to end	Day	10% 7% 3 8% 5% 5% 5% 4 5% 7% 40%	4466
January	1st to 10th	Night	9% 5% 2 5% 4 3 3 3 4 8% 55%	5889
	11th to 20th	Night	19% 10% 3 8% 5% 4 4 4 5% 7% 31%	5900
	21st to end	Night	15% 6% 3 6% 4 4 3 3 5% 8% 43%	6462
February	1st to 10th	Night	11% 7% 2 6% 4 4 4 3 6% 8% 45%	2400
	11th to 20th	Night	10% 5% 2 6% 3 4 4 4 6% 6% 49%	2338
	21st to end	Night	8% 5% 2 6% 4 4 4 4 5% 7% 53%	1845
March	1st to 10th	Night	13% 7% 3 6% 4 4 3 3 5% 7% 45%	4918
	11th to 20th	Night	5% 3 2 4 3 3 4 4 5% 10% 56%	4980
	21st to end	Night	8% 6% 2 6% 4 4 4 3 5% 8% 49%	5467
April	1st to 10th	Night	7% 4 2 5% 3 4 4 3 7% 9% 52%	2200
	11th to 20th	Night	7% 5% 2 6% 5% 4 3 4 6% 7% 51%	2098
	21st to end	Night	5% 4 1 5% 4 4 4 4 6% 9% 55%	2000
May	1st to 10th	Night	5% 3 2 7% 4 5% 5% 4 6% 9% 51%	4228
	11th to 20th	Night	8% 6% 2 6% 4 4 4 4 6% 9% 48%	4032
	21st to end	Night	4 4 1 6% 4 4 5% 4 8% 10% 50%	4421
June	1st to 10th	Night	9% 6% 3 7% 5% 5% 6% 5% 8% 10% 35%	1800
	11th to 20th	Night	6% 5% 3 9% 6% 6% 7% 5% 8% 12% 34%	1800
	21st to end	Night	7% 6% 3 8% 6% 6% 6% 6% 8% 10% 34%	1800
July	1st to 10th	Night	8% 7% 3 9% 6% 6% 7% 6% 10% 13% 25%	4058
	11th to 20th	Night	4 4 2 7% 5% 7% 7% 6% 10% 13% 34%	4057
	21st to end	Night	5% 6% 3 8% 6% 6% 6% 5% 7% 12% 35%	4427
August	1st to 10th	Night	5% 5% 3 10% 7% 6% 6% 5% 9% 12% 34%	2915
	11th to 20th	Night	4 3 2 7% 5% 5% 6% 5% 10% 13% 39%	2968
	21st to end	Night	8% 5% 3 7% 6% 6% 6% 6% 9% 12% 33%	3930
September	1st to 10th	Night	8% 7% 2 9% 7% 7% 6% 6% 9% 11% 29%	2200
	11th to 20th	Night	9% 9% 3 8% 7% 6% 7% 5% 8% 11% 28%	2200
	21st to end	Night	10% 6% 2 7% 6% 6% 6% 5% 7% 8% 36%	2200
October	1st to 10th	Night	9% 6% 3 7% 6% 5% 7% 5% 6% 8% 38%	2252
	11th to 20th	Night	6% 4 2 5% 5% 4 4 4 6% 9% 52%	2400
	21st to end	Night	8% 5% 2 6% 4 3 4 4 6% 9% 50%	2640
November	1st to 10th	Night	8% 5% 3 7% 5% 4 5% 4 6% 8% 46%	2461
	11th to 20th	Night	8% 6% 2 6% 5% 4 5% 4 6% 7% 47%	2485
	21st to end	Night	9% 6% 3 6% 4 5% 5% 4 6% 8% 44%	2485
December	1st to 10th	Night	5% 3 1 5% 4 4 4 3 6% 7% 57%	4250
	11th to 20th	Night	11% 7% 2 6% 4 4 4 4 5% 7% 45%	4822
	21st to end	Night	12% 8% 3 7% 5% 5% 5% 4 5% 7% 39%	6490

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	30% 4 10% 16% 28% 13%	4057
	11th to 20th	Day	54% 3 4 16% 16% 7%	4060
	21st to end	Day	38% 4 7% 27% 17% 8%	4489
February	1st to 10th	Day	40% 6% 10% 15% 21% 8%	2000
	11th to 20th	Day	33% 5% 9% 21% 22% 11%	1958
	21st to end	Day	37% 5% 10% 18% 22% 9%	1784
March	1st to 10th	Day	38% 6% 12% 18% 20% 6%	4935
	11th to 20th	Day	24% 4 10% 24% 22% 17%	4980
	21st to end	Day	35% 4 10% 27% 16% 8%	5465
April	1st to 10th	Day	31% 7% 12% 23% 19% 8%	2200
	11th to 20th	Day	36% 8% 9% 20% 20% 7%	2249
	21st to end	Day	28% 7% 12% 23% 22% 8%	2400
May	1st to 10th	Day	28% 7% 22% 26% 13% 4	5713
	11th to 20th	Day	36% 7% 15% 31% 10% 1	5865
	21st to end	Day	31% 6% 17% 33% 13% 1	6447
June	1st to 10th	Day	49% 12% 18% 16% 5%	2600
	11th to 20th	Day	48% 11% 20% 19% 2	2600
	21st to end	Day	48% 12% 22% 14% 3	2600
July	1st to 10th	Day	50% 11% 28% 10% 1	5835
	11th to 20th	Day	42% 11% 35% 12%	5831
	21st to end	Day	40% 9% 28% 21% 1	6240
August	1st to 10th	Day	47% 11% 29% 11% 2	4221
	11th to 20th	Day	39% 10% 26% 20% 5%	4086
	21st to end	Day	49% 11% 24% 16% 1	3961
September	1st to 10th	Day	52% 15% 19% 10% 4	2200
	11th to 20th	Day	53% 12% 19% 13% 3	2200
	21st to end	Day	48% 9% 15% 16% 9% 3	2200
October	1st to 10th	Day	55% 7% 15% 12% 8% 4	3496
	11th to 20th	Day	31% 4 7% 22% 29% 7%	3240
	21st to end	Day	28% 4 6% 23% 32% 7%	3538
November	1st to 10th	Day	37% 7% 11% 18% 20% 8%	2057
	11th to 20th	Day	39% 6% 8% 19% 19% 8%	2070
	21st to end	Day	39% 6% 9% 20% 19% 7%	1910
December	1st to 10th	Day	27% 4 16% 27% 17% 9%	2930
	11th to 20th	Day	44% 4 11% 17% 18% 6%	3370
	21st to end	Day	42% 5% 11% 22% 16% 5%	4466
January	1st to 10th	Night	30% 4 8% 18% 28% 13%	5889
	11th to 20th	Night	53% 4 8% 16% 15% 4	5900
	21st to end	Night	39% 5% 9% 23% 15% 9%	6462
February	1st to 10th	Night	37% 5% 11% 18% 17% 12%	2400
	11th to 20th	Night	34% 7% 11% 19% 20% 10%	2339
	21st to end	Night	30% 5% 14% 19% 24% 8%	1845
March	1st to 10th	Night	40% 4 11% 17% 19% 8%	4918
	11th to 20th	Night	23% 5% 14% 24% 17% 17%	4980
	21st to end	Night	34% 5% 11% 24% 20% 6%	5467
April	1st to 10th	Night	28% 7% 16% 25% 15% 9%	2200
	11th to 20th	Night	30% 7% 10% 26% 19% 8%	2098
	21st to end	Night	27% 6% 13% 28% 20% 7%	2000
May	1st to 10th	Night	28% 6% 21% 29% 13% 3	4258
	11th to 20th	Night	33% 7% 20% 29% 11% 1	4033
	21st to end	Night	28% 7% 20% 32% 13%	4429
June	1st to 10th	Night	40% 10% 23% 22% 4	1800
	11th to 20th	Night	40% 13% 23% 22% 3	1800
	21st to end	Night	41% 13% 24% 16% 5% 1	1800
July	1st to 10th	Night	48% 12% 28% 11% 1	4015
	11th to 20th	Night	37% 13% 39% 11% 1	4006
	21st to end	Night	39% 10% 27% 23% 1	4297
August	1st to 10th	Night	41% 10% 36% 11% 2	2904
	11th to 20th	Night	32% 10% 31% 21% 6%	2995
	21st to end	Night	41% 12% 29% 15% 2	3930
September	1st to 10th	Night	44% 18% 20% 13% 5%	2200
	11th to 20th	Night	47% 12% 21% 16% 3	2200
	21st to end	Night	41% 11% 18% 20% 9% 2	2200
October	1st to 10th	Night	54% 8% 13% 14% 7% 3	3681
	11th to 20th	Night	31% 4 6% 26% 28% 5%	3899
	21st to end	Night	31% 4 7% 22% 30% 6%	4252
November	1st to 10th	Night	34% 7% 11% 20% 19% 8%	2461
	11th to 20th	Night	34% 7% 10% 20% 19% 9%	2485
	21st to end	Night	37% 7% 11% 21% 18% 7%	2485
December	1st to 10th	Night	26% 4 16% 29% 11% 13%	4250
	11th to 20th	Night	40% 4 11% 21% 15% 8%	4824
	21st to end	Night	44% 5% 11% 22% 13% 5%	6490

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	12% 14% 46% 21% 6% 1	300
	11th to 20th	Day	10% 13% 41% 24% 7% 3	300
	21st to end	Day	18% 17% 44% 15% 5%	330
February	1st to 10th	Day	13% 14% 36% 21% 13% 3	300
	11th to 20th	Day	13% 11% 39% 26% 9% 2	300
	21st to end	Day	11% 12% 32% 29% 14% 2	383
March	1st to 10th	Day	6% 15% 34% 32% 11% 1	500
	11th to 20th	Day	9% 13% 32% 28% 16% 3	500
	21st to end	Day	8% 10% 32% 30% 17% 3	550
April	1st to 10th	Day	8% 11% 35% 27% 15% 4	500
	11th to 20th	Day	8% 12% 29% 27% 18% 6%	492
	21st to end	Day	6% 5% 26% 32% 18% 14%	500
May	1st to 10th	Day	7% 6% 21% 32% 22% 12%	503
	11th to 20th	Day	9% 4 20% 31% 22% 14%	527
	21st to end	Day	7% 2 13% 26% 31% 21%	573
June	1st to 10th	Day	12% 2 13% 28% 25% 19%	530
	11th to 20th	Day	7% 2 11% 25% 25% 30%	530
	21st to end	Day	7% 2 6% 19% 29% 38%	530
July	1st to 10th	Day	7% 3 3 13% 31% 43%	525
	11th to 20th	Day	5% 1 2 15% 32% 45%	524
	21st to end	Day	9% 1 3 18% 28% 41%	576
August	1st to 10th	Day	6% 2 6% 18% 29% 39%	526
	11th to 20th	Day	4 1 3 15% 29% 48%	519
	21st to end	Day	10% 2 6% 22% 25% 34%	583
September	1st to 10th	Day	10% 3 8% 17% 31% 31%	530
	11th to 20th	Day	10% 4 9% 26% 28% 22%	530
	21st to end	Day	9% 2 12% 26% 28% 24%	530
October	1st to 10th	Day	14% 5% 21% 30% 22% 8%	530
	11th to 20th	Day	7% 5% 18% 37% 26% 8%	530
	21st to end	Day	8% 5% 24% 35% 23% 5%	583
November	1st to 10th	Day	10% 7% 23% 30% 26% 4	535
	11th to 20th	Day	10% 8% 27% 34% 16% 5%	528
	21st to end	Day	12% 7% 30% 34% 14% 3	410
December	1st to 10th	Day	5% 12% 42% 27% 12% 2	300
	11th to 20th	Day	12% 12% 34% 28% 12% 1	300
	21st to end	Day	10% 10% 32% 38% 10% 1	330
January	1st to 10th	Night	11% 9% 33% 35% 11% 1	800
	11th to 20th	Night	11% 8% 31% 36% 14% 1	800
	21st to end	Night	15% 9% 35% 33% 8%	880
February	1st to 10th	Night	14% 7% 30% 34% 13% 1	800
	11th to 20th	Night	13% 7% 32% 36% 10% 1	783
	21st to end	Night	9% 8% 34% 40% 8%	660
March	1st to 10th	Night	6% 9% 35% 40% 11% 1	800
	11th to 20th	Night	8% 8% 28% 40% 15% 1	800
	21st to end	Night	7% 8% 32% 38% 13% 1	880
April	1st to 10th	Night	8% 6% 33% 38% 14% 1	800
	11th to 20th	Night	7% 8% 28% 38% 18% 1	791
	21st to end	Night	7% 4 24% 45% 19% 1	800
May	1st to 10th	Night	7% 3 16% 49% 23% 2	694
	11th to 20th	Night	7% 2 14% 40% 33% 3	591
	21st to end	Night	7% 2 8% 33% 43% 7%	650
June	1st to 10th	Night	11% 3 10% 29% 42% 6%	600
	11th to 20th	Night	7% 2 4 24% 44% 19%	600
	21st to end	Night	7% 2 5% 18% 50% 18%	600
July	1st to 10th	Night	11% 2 3 17% 46% 22%	585
	11th to 20th	Night	6% 1 1 12% 52% 28%	582
	21st to end	Night	5% 2 3 16% 51% 24%	657
August	1st to 10th	Night	6% 1 3 17% 50% 23%	597
	11th to 20th	Night	4 1 2 14% 49% 29%	648
	21st to end	Night	12% 1 7% 20% 41% 19%	880
September	1st to 10th	Night	11% 2 6% 19% 43% 19%	800
	11th to 20th	Night	12% 2 8% 27% 41% 10%	800
	21st to end	Night	12% 2 7% 25% 42% 12%	800
October	1st to 10th	Night	13% 2 14% 37% 28% 6%	800
	11th to 20th	Night	7% 3 13% 38% 35% 4	800
	21st to end	Night	10% 3 16% 39% 29% 3	880
November	1st to 10th	Night	10% 3 21% 36% 28% 2	820
	11th to 20th	Night	8% 6% 21% 42% 21% 2	829
	21st to end	Night	10% 5% 28% 39% 18% 1	800
December	1st to 10th	Night	8% 4 29% 36% 22% 2	800
	11th to 20th	Night	12% 8% 22% 37% 19% 1	800
	21st to end	Night	11% 6% 27% 38% 17% 1	880

Page generated at 2025-11-15 00:55:59. Version ac07

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