Tandy Hills Natural Area
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tandy Hills Natural Area clear sky chart from 2005-11-06 to 2024-07-31.

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	11% 5% 2 5% 4 3 4 3 5% 7% 51%	90108
	Night	11% 5% 2 4 3 3 3 3 5% 6% 56%	89757
Transparency	Day	32% 5% 10% 23% 22% 8%	89883
	Night	29% 4 9% 23% 24% 11%	89587
Seeing	Day	13% 11% 26% 29% 17% 4	14796
	Night	13% 9% 31% 33% 13% 1	24673

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	11% 6% 2 4 3 3 4 2 4 6% 56%	2847
	11th to 20th	Day	10% 5% 1 3 2 2 2 2 4 6% 61%	2850
	21st to end	Day	21% 10% 3 5% 2 2 2 2 3 4 48%	3135
February	1st to 10th	Day	14% 8% 3 5% 3 3 4 2 4 6% 48%	1862
	11th to 20th	Day	14% 8% 3 6% 3 3 3 3 4 5% 49%	1849
	21st to end	Day	20% 8% 2 3 2 2 2 2 2 3 54%	1570
March	1st to 10th	Day	15% 6% 2 4 3 2 3 3 5% 7% 50%	3435
	11th to 20th	Day	16% 6% 3 5% 4 5% 4 3 5% 6% 43%	3480
	21st to end	Day	11% 6% 2 6% 4 5% 5% 4 6% 7% 44%	3814
April	1st to 10th	Day	11% 5% 2 5% 5% 3 4 3 4 6% 50%	2090
	11th to 20th	Day	12% 6% 2 6% 4 4 4 3 5% 7% 47%	2132
	21st to end	Day	11% 5% 2 5% 4 4 5% 4 5% 6% 49%	2456
May	1st to 10th	Day	18% 8% 3 6% 3 3 4 3 5% 6% 40%	4082
	11th to 20th	Day	14% 6% 2 5% 3 4 4 3 5% 5% 49%	4082
	21st to end	Day	13% 8% 3 7% 5% 4 5% 4 6% 9% 37%	4477
June	1st to 10th	Day	4 3 2 5% 4 4 4 4 7% 10% 52%	2470
	11th to 20th	Day	4 4 1 5% 4 4 5% 3 6% 9% 54%	2470
	21st to end	Day	5% 3 1 3 4 4 4 4 6% 9% 55%	2470
July	1st to 10th	Day	5% 5% 2 6% 4 5% 5% 5% 9% 9% 45%	2470
	11th to 20th	Day	3 2 1 3 3 3 4 4 6% 8% 63%	2470
	21st to end	Day	3 3 1 5% 5% 4 5% 5% 8% 10% 51%	2678
August	1st to 10th	Day	2 1 1 3 3 4 4 4 7% 9% 63%	2328
	11th to 20th	Day	7% 4 2 5% 4 4 5% 4 7% 9% 50%	2301
	21st to end	Day	4 3 1 4 4 5% 5% 4 7% 10% 52%	2290
September	1st to 10th	Day	7% 5% 1 5% 4 3 3 3 5% 7% 55%	1980
	11th to 20th	Day	11% 4 2 5% 5% 5% 5% 4 6% 6% 46%	1980
	21st to end	Day	8% 3 1 3 3 3 4 3 6% 7% 59%	1980
October	1st to 10th	Day	5% 3 1 4 3 3 3 4 5% 8% 61%	1958
	11th to 20th	Day	11% 5% 2 3 2 3 3 2 4 6% 60%	1800
	21st to end	Day	13% 5% 2 4 2 2 2 2 3 4 61%	1980
November	1st to 10th	Day	13% 5% 2 4 3 2 3 3 3 5% 58%	1858
	11th to 20th	Day	7% 3 1 4 4 3 3 3 4 7% 61%	1748
	21st to end	Day	15% 6% 2 4 3 3 2 2 4 5% 54%	1710
December	1st to 10th	Day	13% 7% 2 4 3 3 3 4 4 6% 52%	1710
	11th to 20th	Day	15% 7% 3 6% 4 3 4 3 4 4 48%	2161
	21st to end	Day	18% 5% 2 4 3 2 3 2 3 5% 51%	3135
January	1st to 10th	Night	14% 4 1 3 3 3 3 2 3 5% 60%	4108
	11th to 20th	Night	11% 5% 1 4 2 2 2 2 3 4 65%	4120
	21st to end	Night	19% 7% 2 4 3 2 2 2 4 5% 50%	4532
February	1st to 10th	Night	14% 7% 2 5% 3 2 3 2 4 5% 53%	2333
	11th to 20th	Night	14% 7% 2 5% 4 3 3 3 4 5% 51%	2218
	21st to end	Night	17% 6% 2 3 3 2 3 2 3 5% 54%	1884
March	1st to 10th	Night	13% 8% 3 7% 4 3 3 3 4 5% 46%	3419
	11th to 20th	Night	15% 5% 2 5% 3 4 3 3 5% 7% 47%	3480
	21st to end	Night	12% 6% 2 5% 4 3 3 3 5% 6% 51%	3817
April	1st to 10th	Night	9% 6% 2 3 4 3 4 3 5% 7% 55%	2090
	11th to 20th	Night	14% 4 2 5% 3 3 3 3 5% 7% 52%	1994
	21st to end	Night	11% 5% 1 4 3 2 3 3 5% 6% 56%	1720
May	1st to 10th	Night	20% 7% 3 6% 4 3 3 3 5% 6% 41%	2823
	11th to 20th	Night	11% 7% 2 6% 4 3 3 3 5% 6% 50%	2823
	21st to end	Night	13% 5% 2 4 4 3 4 3 6% 7% 49%	3090
June	1st to 10th	Night	4 3 2 4 4 4 4 4 6% 9% 58%	1710
	11th to 20th	Night	3 2 1 3 2 3 4 3 6% 9% 64%	1710
	21st to end	Night	2 2 1 4 4 2 4 4 7% 10% 59%	1710
July	1st to 10th	Night	3 4 1 4 3 4 4 4 7% 12% 54%	1710
	11th to 20th	Night	3 1 1 2 2 2 2 3 5% 8% 71%	1710
	21st to end	Night	1 2 1 3 3 3 5% 3 7% 10% 61%	1871
August	1st to 10th	Night	2 1 1 1 1 2 2 2 5% 10% 72%	1611
	11th to 20th	Night	5% 4 2 3 3 3 3 4 6% 10% 58%	1600
	21st to end	Night	4 3 1 3 3 4 3 3 7% 11% 57%	2058
September	1st to 10th	Night	7% 5% 1 4 3 4 4 3 6% 8% 56%	1980
	11th to 20th	Night	11% 5% 2 4 3 3 3 3 5% 7% 52%	1980
	21st to end	Night	6% 3 1 3 2 3 2 3 6% 7% 63%	1980
October	1st to 10th	Night	6% 3 1 3 3 3 3 3 4 7% 64%	1982
	11th to 20th	Night	10% 4 1 3 2 2 2 2 4 5% 64%	2160
	21st to end	Night	15% 3 1 3 2 2 2 1 3 5% 61%	2376
November	1st to 10th	Night	10% 5% 2 4 3 3 3 2 3 4 62%	2220
	11th to 20th	Night	6% 3 2 4 3 3 3 3 5% 7% 61%	2430
	21st to end	Night	15% 6% 1 4 3 3 3 2 3 5% 54%	2470
December	1st to 10th	Night	11% 6% 2 4 3 3 3 3 4 6% 56%	2470
	11th to 20th	Night	12% 7% 2 5% 3 3 3 3 5% 6% 52%	3036
	21st to end	Night	16% 6% 2 4 2 2 3 2 3 5% 55%	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	30% 4 6% 20% 32% 7%	2848
	11th to 20th	Day	27% 2 8% 22% 33% 9%	2850
	21st to end	Day	42% 3 4 19% 23% 8%	3135
February	1st to 10th	Day	38% 3 7% 19% 21% 11%	1862
	11th to 20th	Day	39% 3 7% 20% 22% 10%	1859
	21st to end	Day	38% 2 4 15% 26% 16%	1570
March	1st to 10th	Day	34% 3 7% 16% 28% 12%	3435
	11th to 20th	Day	42% 4 11% 22% 16% 5%	3480
	21st to end	Day	36% 5% 14% 21% 18% 7%	3814
April	1st to 10th	Day	34% 4 10% 20% 19% 12%	2090
	11th to 20th	Day	36% 4 9% 21% 20% 10%	2132
	21st to end	Day	34% 5% 9% 21% 25% 6%	2456
May	1st to 10th	Day	43% 6% 10% 19% 16% 6%	4120
	11th to 20th	Day	37% 4 10% 23% 24% 2	4086
	21st to end	Day	42% 6% 13% 22% 11% 6%	4489
June	1st to 10th	Day	26% 7% 15% 30% 18% 4	2470
	11th to 20th	Day	26% 5% 12% 31% 20% 6%	2470
	21st to end	Day	25% 5% 12% 27% 26% 5%	2470
July	1st to 10th	Day	31% 7% 17% 28% 15% 2	2406
	11th to 20th	Day	18% 6% 13% 35% 23% 5%	2401
	21st to end	Day	21% 8% 18% 34% 18% 1	2537
August	1st to 10th	Day	16% 6% 14% 34% 27% 3	2314
	11th to 20th	Day	28% 7% 16% 27% 20% 2	2301
	21st to end	Day	25% 7% 13% 32% 20% 4	2290
September	1st to 10th	Day	28% 4 9% 23% 25% 10%	1980
	11th to 20th	Day	36% 6% 10% 20% 20% 8%	1980
	21st to end	Day	24% 4 8% 24% 27% 13%	1980
October	1st to 10th	Day	22% 4 12% 24% 22% 16%	1958
	11th to 20th	Day	27% 3 6% 18% 27% 19%	1800
	21st to end	Day	29% 3 6% 20% 25% 17%	1980
November	1st to 10th	Day	30% 3 8% 23% 26% 11%	1858
	11th to 20th	Day	25% 3 9% 22% 30% 12%	1748
	21st to end	Day	35% 2 5% 21% 24% 12%	1710
December	1st to 10th	Day	33% 3 9% 23% 24% 8%	1710
	11th to 20th	Day	39% 4 7% 15% 26% 10%	2159
	21st to end	Day	37% 3 4 24% 22% 10%	3135
January	1st to 10th	Night	28% 3 5% 21% 33% 11%	4108
	11th to 20th	Night	26% 2 6% 22% 29% 15%	4120
	21st to end	Night	39% 3 5% 17% 26% 11%	4532
February	1st to 10th	Night	35% 3 8% 18% 21% 15%	2333
	11th to 20th	Night	36% 3 7% 16% 27% 11%	2218
	21st to end	Night	35% 3 6% 16% 22% 17%	1884
March	1st to 10th	Night	40% 3 5% 15% 23% 13%	3419
	11th to 20th	Night	36% 4 11% 22% 19% 7%	3480
	21st to end	Night	35% 5% 8% 21% 26% 5%	3817
April	1st to 10th	Night	29% 4 10% 22% 20% 16%	2090
	11th to 20th	Night	32% 4 11% 19% 19% 15%	1994
	21st to end	Night	28% 5% 11% 22% 28% 6%	1720
May	1st to 10th	Night	43% 4 9% 21% 14% 8%	2850
	11th to 20th	Night	35% 5% 12% 22% 25% 2	2824
	21st to end	Night	32% 6% 14% 28% 14% 6%	3099
June	1st to 10th	Night	22% 6% 14% 32% 21% 5%	1710
	11th to 20th	Night	17% 4 13% 34% 23% 8%	1710
	21st to end	Night	19% 7% 12% 27% 28% 7%	1710
July	1st to 10th	Night	21% 6% 17% 36% 17% 3	1665
	11th to 20th	Night	12% 4 11% 37% 29% 7%	1656
	21st to end	Night	15% 5% 18% 35% 23% 3	1772
August	1st to 10th	Night	9% 4 11% 39% 31% 6%	1601
	11th to 20th	Night	22% 5% 14% 31% 23% 6%	1600
	21st to end	Night	21% 6% 12% 33% 24% 5%	2058
September	1st to 10th	Night	26% 6% 10% 22% 26% 10%	1980
	11th to 20th	Night	31% 6% 12% 19% 21% 11%	1980
	21st to end	Night	20% 4 8% 24% 28% 17%	1980
October	1st to 10th	Night	21% 3 8% 28% 21% 19%	1982
	11th to 20th	Night	24% 2 8% 17% 26% 22%	2160
	21st to end	Night	29% 2 4 17% 28% 20%	2376
November	1st to 10th	Night	28% 3 6% 20% 27% 15%	2220
	11th to 20th	Night	23% 4 7% 23% 28% 15%	2430
	21st to end	Night	34% 3 7% 16% 28% 13%	2470
December	1st to 10th	Night	31% 2 7% 24% 24% 12%	2470
	11th to 20th	Night	34% 3 6% 16% 28% 13%	3037
	21st to end	Night	33% 3 6% 18% 26% 14%	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	21% 24% 31% 19% 5%	270
	11th to 20th	Day	22% 27% 33% 13% 4 1	270
	21st to end	Day	23% 25% 32% 14% 5%	297
February	1st to 10th	Day	23% 23% 37% 14% 2 1	270
	11th to 20th	Day	26% 21% 41% 9% 3	270
	21st to end	Day	31% 28% 32% 5% 3	225
March	1st to 10th	Day	24% 27% 32% 15% 2	270
	11th to 20th	Day	25% 25% 37% 11% 3	270
	21st to end	Day	16% 26% 44% 11% 3	297
April	1st to 10th	Day	19% 25% 35% 17% 3	270
	11th to 20th	Day	22% 22% 37% 16% 4	330
	21st to end	Day	15% 19% 39% 19% 6% 1	636
May	1st to 10th	Day	17% 13% 40% 24% 5% 1	653
	11th to 20th	Day	18% 8% 36% 26% 11% 1	675
	21st to end	Day	14% 10% 33% 28% 13% 3	734
June	1st to 10th	Day	4 4 25% 40% 22% 6%	680
	11th to 20th	Day	5% 3 30% 40% 18% 4	680
	21st to end	Day	4 3 17% 44% 26% 6%	680
July	1st to 10th	Day	6% 2 14% 41% 28% 9%	671
	11th to 20th	Day	2 1 12% 42% 37% 7%	668
	21st to end	Day	3 2 9% 40% 37% 10%	736
August	1st to 10th	Day	1 1 9% 45% 36% 8%	626
	11th to 20th	Day	9% 2 10% 38% 34% 7%	615
	21st to end	Day	4 2 7% 35% 36% 15%	409
September	1st to 10th	Day	6% 1 8% 34% 40% 11%	270
	11th to 20th	Day	7% 2 12% 35% 34% 10%	270
	21st to end	Day	14% 3 11% 39% 21% 11%	270
October	1st to 10th	Day	3 5% 31% 37% 20% 4	270
	11th to 20th	Day	12% 10% 34% 31% 11% 2	270
	21st to end	Day	25% 9% 32% 23% 9% 1	297
November	1st to 10th	Day	21% 13% 33% 24% 7% 2	270
	11th to 20th	Day	13% 14% 39% 26% 7% 2	270
	21st to end	Day	24% 21% 31% 19% 4 1	270
December	1st to 10th	Day	20% 17% 34% 19% 9% 2	270
	11th to 20th	Day	19% 21% 34% 22% 4	270
	21st to end	Day	23% 20% 36% 16% 4	297
January	1st to 10th	Night	13% 12% 37% 31% 7%	950
	11th to 20th	Night	18% 16% 31% 29% 6%	950
	21st to end	Night	16% 15% 32% 30% 6%	1045
February	1st to 10th	Night	18% 16% 37% 25% 3 1	813
	11th to 20th	Night	18% 16% 39% 24% 3	744
	21st to end	Night	22% 17% 39% 19% 2	628
March	1st to 10th	Night	17% 15% 39% 25% 4	570
	11th to 20th	Night	18% 13% 39% 25% 5%	570
	21st to end	Night	14% 16% 39% 27% 4	627
April	1st to 10th	Night	12% 18% 40% 25% 4	570
	11th to 20th	Night	16% 16% 38% 27% 4	563
	21st to end	Night	15% 13% 43% 23% 6% 1	570
May	1st to 10th	Night	12% 13% 41% 27% 6% 1	570
	11th to 20th	Night	12% 7% 40% 30% 11% 1	561
	21st to end	Night	10% 7% 36% 32% 14% 1	617
June	1st to 10th	Night	5% 3 28% 42% 20% 2	570
	11th to 20th	Night	4 2 34% 47% 12% 1	570
	21st to end	Night	2 2 28% 40% 25% 3	570
July	1st to 10th	Night	4 22% 42% 28% 3	555
	11th to 20th	Night	3 1 19% 49% 26% 1	552
	21st to end	Night	2 1 13% 56% 26% 2	624
August	1st to 10th	Night	2 1 12% 54% 28% 2	537
	11th to 20th	Night	7% 1 13% 44% 30% 5%	534
	21st to end	Night	4 2 9% 44% 35% 6%	594
September	1st to 10th	Night	8% 1 14% 43% 30% 4	540
	11th to 20th	Night	13% 1 13% 37% 33% 3	540
	21st to end	Night	8% 2 20% 40% 26% 4	540
October	1st to 10th	Night	7% 2 27% 36% 24% 3	542
	11th to 20th	Night	12% 8% 29% 34% 16% 1	720
	21st to end	Night	18% 9% 31% 30% 12%	792
November	1st to 10th	Night	12% 6% 35% 34% 13% 1	740
	11th to 20th	Night	8% 11% 35% 33% 12% 1	910
	21st to end	Night	19% 12% 34% 24% 9% 1	950
December	1st to 10th	Night	15% 12% 34% 32% 6%	950
	11th to 20th	Night	19% 10% 34% 31% 6%	950
	21st to end	Night	18% 12% 35% 28% 6%	1045

Page generated at 2024-07-28 08:52:11. Version ac07

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