Cedar Hill Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cedar Hill Park clear sky chart from 2005-11-06 to 2024-02-20.

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 5% 5% 3 5% 5% 5% 7% 42%	78461
	Night	14% 8% 3 6% 5% 3 4 4 5% 6% 43%	80775
Transparency	Day	41% 6% 11% 23% 16% 3	78172
	Night	42% 5% 10% 23% 16% 3	80585
Seeing	Day	16% 12% 27% 25% 15% 5%	14556
	Night	17% 11% 29% 28% 13% 1	24569

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	10% 12% 6% 9% 7% 3 4 5% 6% 7% 31%	2527
	11th to 20th	Day	12% 9% 5% 7% 5% 4 4 4 4 7% 39%	2786
	21st to end	Day	21% 15% 5% 7% 4 3 3 3 4 5% 31%	3135
February	1st to 10th	Day	16% 11% 5% 7% 5% 3 4 4 4 7% 35%	1710
	11th to 20th	Day	15% 9% 4 6% 7% 3 4 5% 5% 6% 38%	1814
	21st to end	Day	16% 11% 3 6% 4 2 4 4 5% 7% 38%	1480
March	1st to 10th	Day	15% 9% 4 7% 5% 2 3 4 4 5% 41%	1840
	11th to 20th	Day	20% 10% 3 7% 6% 3 5% 3 4 5% 35%	1980
	21st to end	Day	20% 11% 4 7% 7% 3 4 5% 5% 5% 29%	2281
April	1st to 10th	Day	11% 6% 3 5% 6% 3 5% 5% 5% 8% 44%	2160
	11th to 20th	Day	17% 9% 3 5% 4 3 4 4 5% 6% 40%	2134
	21st to end	Day	19% 6% 3 6% 6% 3 4 4 4 7% 37%	2160
May	1st to 10th	Day	17% 7% 3 6% 5% 3 6% 5% 5% 7% 36%	2184
	11th to 20th	Day	17% 6% 2 5% 5% 3 4 4 6% 8% 40%	2452
	21st to end	Day	10% 5% 3 6% 6% 5% 6% 7% 7% 9% 36%	2725
June	1st to 10th	Day	8% 5% 2 5% 5% 3 6% 5% 6% 8% 46%	2520
	11th to 20th	Day	8% 3 2 4 4 3 5% 5% 6% 10% 49%	2520
	21st to end	Day	5% 3 2 5% 5% 3 7% 5% 8% 9% 48%	2520
July	1st to 10th	Day	10% 3 2 5% 5% 4 5% 6% 7% 11% 43%	2520
	11th to 20th	Day	5% 3 2 3 4 3 5% 6% 7% 11% 51%	2520
	21st to end	Day	8% 5% 2 5% 6% 3 5% 6% 6% 10% 44%	2576
August	1st to 10th	Day	7% 5% 2 5% 5% 3 6% 7% 7% 10% 42%	2324
	11th to 20th	Day	10% 5% 2 5% 6% 4 6% 5% 7% 9% 40%	2125
	21st to end	Day	9% 5% 2 4 4 3 4 4 5% 9% 50%	2376
September	1st to 10th	Day	14% 5% 2 4 4 2 4 4 6% 8% 48%	2160
	11th to 20th	Day	10% 5% 2 5% 5% 3 4 5% 4 8% 50%	2146
	21st to end	Day	7% 4 2 4 6% 2 4 4 5% 8% 54%	1962
October	1st to 10th	Day	10% 4 2 6% 5% 3 4 3 4 7% 54%	1800
	11th to 20th	Day	15% 5% 2 4 4 2 3 3 4 6% 51%	1800
	21st to end	Day	18% 8% 2 4 5% 2 4 3 4 6% 46%	1980
November	1st to 10th	Day	11% 4 2 4 5% 3 3 3 4 6% 55%	1674
	11th to 20th	Day	14% 6% 3 5% 5% 2 3 3 5% 7% 47%	1710
	21st to end	Day	16% 9% 4 5% 4 2 4 4 3 5% 44%	1639
December	1st to 10th	Day	14% 10% 3 5% 4 3 4 5% 4 8% 39%	1520
	11th to 20th	Day	13% 11% 4 6% 6% 3 3 4 4 6% 39%	1918
	21st to end	Day	18% 15% 6% 8% 6% 3 4 4 4 5% 27%	2783
January	1st to 10th	Night	15% 10% 7% 8% 6% 3 4 4 4 5% 36%	4428
	11th to 20th	Night	13% 10% 4 10% 7% 4 7% 4 4 4 30%	4182
	21st to end	Night	23% 15% 5% 7% 4 2 3 3 3 4 30%	4532
February	1st to 10th	Night	17% 10% 5% 8% 5% 3 4 4 5% 6% 34%	2470
	11th to 20th	Night	14% 8% 4 7% 5% 3 4 3 4 5% 43%	2236
	21st to end	Night	17% 10% 3 7% 6% 3 3 3 3 5% 39%	1776
March	1st to 10th	Night	17% 9% 3 6% 4 3 4 3 3 5% 43%	2134
	11th to 20th	Night	19% 8% 3 6% 5% 3 4 5% 4 6% 37%	1980
	21st to end	Night	20% 11% 4 8% 6% 2 4 5% 5% 6% 30%	2075
April	1st to 10th	Night	11% 6% 3 5% 5% 3 4 3 5% 7% 48%	1800
	11th to 20th	Night	14% 8% 3 5% 5% 3 3 4 5% 7% 43%	1775
	21st to end	Night	20% 6% 3 5% 4 3 3 3 4 7% 41%	1800
May	1st to 10th	Night	16% 6% 3 4 5% 3 5% 4 5% 7% 44%	1774
	11th to 20th	Night	15% 7% 4 4 5% 2 4 3 5% 8% 44%	1439
	21st to end	Night	9% 6% 2 5% 5% 4 5% 6% 6% 9% 42%	1551
June	1st to 10th	Night	8% 4 2 5% 5% 2 5% 5% 6% 10% 48%	1440
	11th to 20th	Night	5% 3 2 3 4 3 4 4 6% 10% 55%	1440
	21st to end	Night	4 3 2 3 4 4 5% 5% 6% 9% 56%	1440
July	1st to 10th	Night	8% 3 2 4 5% 3 4 5% 6% 10% 49%	1440
	11th to 20th	Night	4 4 2 4 4 3 4 4 7% 10% 54%	1440
	21st to end	Night	6% 3 2 4 5% 3 4 5% 6% 10% 51%	1738
August	1st to 10th	Night	7% 3 1 4 5% 3 4 5% 6% 9% 53%	1613
	11th to 20th	Night	6% 4 2 4 5% 3 5% 4 6% 9% 51%	1776
	21st to end	Night	6% 3 1 5% 4 3 4 4 5% 9% 55%	1980
September	1st to 10th	Night	12% 5% 2 5% 4 2 3 3 5% 6% 53%	1800
	11th to 20th	Night	9% 5% 1 4 4 2 4 5% 5% 7% 53%	1800
	21st to end	Night	8% 5% 1 4 4 2 5% 4 5% 6% 57%	1990
October	1st to 10th	Night	8% 4 2 4 4 3 3 3 5% 7% 58%	2160
	11th to 20th	Night	14% 5% 2 5% 3 2 3 3 5% 6% 52%	2160
	21st to end	Night	20% 8% 2 3 3 1 3 3 3 6% 47%	2376
November	1st to 10th	Night	11% 5% 2 4 3 2 2 4 4 5% 57%	2401
	11th to 20th	Night	15% 5% 3 4 4 2 3 4 4 6% 49%	2470
	21st to end	Night	18% 9% 3 5% 3 2 3 3 5% 5% 45%	2536
December	1st to 10th	Night	16% 11% 3 6% 5% 3 3 5% 5% 7% 37%	2660
	11th to 20th	Night	16% 9% 4 6% 5% 3 4 3 3 6% 40%	3279
	21st to end	Night	16% 18% 5% 8% 7% 3 4 5% 4 5% 24%	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	49% 5% 12% 23% 9% 1	2528
	11th to 20th	Day	46% 4 11% 23% 16% 1	2786
	21st to end	Day	56% 3 9% 16% 13% 2	3135
February	1st to 10th	Day	49% 5% 10% 22% 12% 1	1710
	11th to 20th	Day	47% 5% 9% 20% 14% 4	1824
	21st to end	Day	46% 4 10% 23% 12% 4	1480
March	1st to 10th	Day	45% 5% 8% 22% 17% 3	1840
	11th to 20th	Day	52% 5% 10% 17% 13% 3	1980
	21st to end	Day	56% 6% 11% 16% 9% 1	2281
April	1st to 10th	Day	37% 6% 12% 26% 19% 1	2160
	11th to 20th	Day	43% 6% 10% 22% 15% 4	2134
	21st to end	Day	47% 6% 9% 23% 13% 1	2160
May	1st to 10th	Day	46% 7% 12% 23% 11% 1	2184
	11th to 20th	Day	41% 7% 11% 24% 15% 2	2456
	21st to end	Day	42% 10% 13% 21% 13% 2	2725
June	1st to 10th	Day	34% 8% 12% 27% 18% 2	2520
	11th to 20th	Day	30% 8% 12% 26% 21% 4	2520
	21st to end	Day	28% 10% 16% 25% 16% 5%	2520
July	1st to 10th	Day	34% 8% 15% 25% 14% 4	2451
	11th to 20th	Day	26% 9% 15% 26% 20% 4	2445
	21st to end	Day	36% 8% 11% 28% 15% 2	2433
August	1st to 10th	Day	33% 9% 14% 26% 16% 1	2310
	11th to 20th	Day	38% 8% 13% 25% 15% 1	2125
	21st to end	Day	31% 7% 14% 24% 18% 5%	2376
September	1st to 10th	Day	35% 6% 11% 27% 18% 5%	2160
	11th to 20th	Day	33% 5% 9% 26% 24% 2	2146
	21st to end	Day	28% 7% 8% 29% 25% 3	1962
October	1st to 10th	Day	31% 5% 10% 26% 25% 4	1800
	11th to 20th	Day	35% 5% 8% 25% 22% 6%	1800
	21st to end	Day	41% 4 8% 26% 17% 4	1980
November	1st to 10th	Day	32% 3 13% 25% 20% 6%	1674
	11th to 20th	Day	37% 5% 8% 24% 22% 5%	1710
	21st to end	Day	44% 4 9% 27% 16%	1639
December	1st to 10th	Day	44% 5% 11% 27% 13% 1	1520
	11th to 20th	Day	47% 4 10% 22% 16% 2	1915
	21st to end	Day	58% 6% 11% 15% 10% 2	2783
January	1st to 10th	Night	50% 5% 10% 24% 11% 1	4428
	11th to 20th	Night	57% 4 9% 20% 9% 1	4182
	21st to end	Night	58% 4 9% 20% 8% 1	4532
February	1st to 10th	Night	51% 5% 10% 20% 13% 1	2470
	11th to 20th	Night	45% 4 9% 22% 17% 3	2237
	21st to end	Night	49% 3 10% 21% 13% 4	1776
March	1st to 10th	Night	46% 4 8% 22% 16% 4	2134
	11th to 20th	Night	49% 5% 8% 21% 13% 3	1980
	21st to end	Night	54% 6% 11% 20% 9% 1	2075
April	1st to 10th	Night	36% 5% 11% 27% 18% 3	1800
	11th to 20th	Night	41% 4 9% 25% 16% 4	1775
	21st to end	Night	46% 4 8% 24% 16% 2	1800
May	1st to 10th	Night	41% 7% 11% 24% 16% 2	1774
	11th to 20th	Night	40% 6% 13% 24% 16% 2	1440
	21st to end	Night	37% 10% 14% 19% 17% 3	1552
June	1st to 10th	Night	31% 6% 14% 27% 18% 3	1440
	11th to 20th	Night	23% 9% 11% 28% 25% 4	1440
	21st to end	Night	23% 8% 15% 29% 19% 7%	1440
July	1st to 10th	Night	29% 9% 15% 27% 15% 5%	1400
	11th to 20th	Night	24% 7% 16% 28% 22% 4	1392
	21st to end	Night	27% 7% 14% 30% 19% 2	1641
August	1st to 10th	Night	27% 9% 15% 32% 15% 2	1603
	11th to 20th	Night	28% 8% 15% 26% 21% 2	1776
	21st to end	Night	27% 7% 13% 25% 23% 5%	1980
September	1st to 10th	Night	32% 6% 9% 26% 21% 6%	1800
	11th to 20th	Night	29% 6% 10% 25% 26% 3	1800
	21st to end	Night	28% 7% 9% 24% 28% 4	1990
October	1st to 10th	Night	26% 4 11% 26% 28% 5%	2160
	11th to 20th	Night	33% 5% 7% 26% 21% 7%	2160
	21st to end	Night	41% 4 8% 21% 21% 4	2376
November	1st to 10th	Night	30% 4 12% 25% 23% 6%	2401
	11th to 20th	Night	37% 4 8% 23% 23% 4	2470
	21st to end	Night	42% 4 9% 25% 19% 2	2536
December	1st to 10th	Night	46% 5% 11% 24% 13% 1	2660
	11th to 20th	Night	47% 4 9% 23% 16% 1	3281
	21st to end	Night	60% 6% 11% 14% 8% 2	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	26% 20% 33% 16% 3 1	270
	11th to 20th	Day	29% 24% 33% 14%	270
	21st to end	Day	18% 29% 36% 13% 3	297
February	1st to 10th	Day	26% 24% 35% 13% 2	270
	11th to 20th	Day	26% 30% 26% 13% 4 1	267
	21st to end	Day	28% 25% 34% 12% 1	198
March	1st to 10th	Day	22% 25% 42% 9% 3	240
	11th to 20th	Day	35% 18% 32% 12% 3 1	240
	21st to end	Day	32% 19% 33% 12% 4	367
April	1st to 10th	Day	18% 19% 37% 20% 6%	420
	11th to 20th	Day	25% 17% 30% 19% 8%	412
	21st to end	Day	25% 14% 36% 19% 5% 1	420
May	1st to 10th	Day	22% 15% 34% 21% 8%	423
	11th to 20th	Day	21% 12% 29% 24% 12% 3	598
	21st to end	Day	13% 6% 33% 27% 15% 6%	679
June	1st to 10th	Day	10% 6% 23% 31% 24% 6%	630
	11th to 20th	Day	9% 3 25% 39% 18% 6%	630
	21st to end	Day	5% 7% 29% 35% 18% 6%	630
July	1st to 10th	Day	11% 2 15% 29% 30% 12%	621
	11th to 20th	Day	5% 4 21% 39% 25% 6%	618
	21st to end	Day	8% 4 17% 33% 30% 8%	684
August	1st to 10th	Day	9% 3 15% 38% 28% 8%	622
	11th to 20th	Day	13% 3 17% 31% 28% 8%	439
	21st to end	Day	10% 2 16% 28% 32% 12%	495
September	1st to 10th	Day	15% 4 16% 27% 30% 7%	450
	11th to 20th	Day	9% 2 16% 32% 28% 13%	450
	21st to end	Day	9% 8% 22% 31% 20% 9%	432
October	1st to 10th	Day	13% 10% 27% 36% 12% 2	270
	11th to 20th	Day	18% 17% 34% 23% 7%	270
	21st to end	Day	32% 19% 27% 19% 4	297
November	1st to 10th	Day	16% 12% 41% 19% 10% 3	270
	11th to 20th	Day	19% 20% 32% 19% 8% 1	270
	21st to end	Day	27% 17% 32% 17% 7% 1	270
December	1st to 10th	Day	19% 21% 34% 17% 7% 2	270
	11th to 20th	Day	23% 19% 34% 19% 4	270
	21st to end	Day	24% 25% 35% 13% 3	297
January	1st to 10th	Night	20% 22% 33% 22% 4	950
	11th to 20th	Night	22% 22% 34% 18% 3	950
	21st to end	Night	19% 20% 38% 21% 2	1045
February	1st to 10th	Night	24% 19% 32% 22% 2	950
	11th to 20th	Night	22% 20% 38% 19% 2	765
	21st to end	Night	24% 20% 34% 19% 2	592
March	1st to 10th	Night	24% 17% 35% 21% 3	694
	11th to 20th	Night	24% 13% 34% 24% 5%	540
	21st to end	Night	26% 13% 34% 23% 4	594
April	1st to 10th	Night	16% 15% 36% 26% 6%	540
	11th to 20th	Night	19% 13% 33% 26% 8% 1	533
	21st to end	Night	25% 10% 36% 22% 7%	540
May	1st to 10th	Night	17% 10% 32% 32% 9% 1	540
	11th to 20th	Night	19% 6% 26% 32% 16% 1	531
	21st to end	Night	11% 6% 25% 35% 20% 3	584
June	1st to 10th	Night	10% 3 19% 39% 28% 1	540
	11th to 20th	Night	6% 2 24% 46% 21% 1	540
	21st to end	Night	4 3 24% 44% 23% 2	540
July	1st to 10th	Night	10% 1 11% 38% 34% 7%	525
	11th to 20th	Night	5% 2 14% 43% 33% 3	522
	21st to end	Night	8% 1 17% 39% 32% 4	591
August	1st to 10th	Night	8% 1 13% 40% 37% 2	537
	11th to 20th	Night	7% 2 13% 40% 35% 4	534
	21st to end	Night	7% 1 14% 34% 39% 4	594
September	1st to 10th	Night	13% 2 15% 35% 30% 5%	540
	11th to 20th	Night	10% 3 14% 35% 32% 6%	540
	21st to end	Night	10% 6% 23% 30% 27% 4	715
October	1st to 10th	Night	8% 5% 29% 31% 22% 5%	720
	11th to 20th	Night	18% 12% 30% 27% 12% 1	720
	21st to end	Night	25% 13% 30% 26% 6%	792
November	1st to 10th	Night	13% 10% 37% 30% 10%	740
	11th to 20th	Night	19% 16% 31% 26% 8%	760
	21st to end	Night	23% 15% 33% 24% 6%	826
December	1st to 10th	Night	24% 13% 33% 25% 5% 1	950
	11th to 20th	Night	24% 14% 30% 27% 4	950
	21st to end	Night	24% 18% 34% 21% 3	1045

Page generated at 2024-02-17 05:28:38. Version ac07

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