Teter Retreat and Organic Farm
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Teter Retreat and Organic Farm clear sky chart from 2005-11-06 to 2025-07-06.

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	14% 9% 4 8% 5% 4 4 4 6% 7% 35%	119496
	Night	15% 10% 4 8% 5% 4 4 3 5% 6% 36%	119427
Transparency	Day	48% 3 11% 24% 14% 2	123137
	Night	48% 2 9% 23% 15% 2	123926
Seeing	Day	18% 7% 25% 25% 17% 7%	16480
	Night	19% 7% 27% 30% 15% 2	26320

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	13% 16% 9% 14% 7% 4 3 3 4 5% 22%	3617
	11th to 20th	Day	12% 16% 8% 12% 7% 6% 6% 5% 5% 4 18%	3620
	21st to end	Day	21% 18% 7% 12% 4 3 3 2 3 4 22%	4172
February	1st to 10th	Day	17% 15% 7% 10% 6% 6% 3 2 4 6% 24%	1978
	11th to 20th	Day	15% 12% 4 11% 7% 5% 4 2 4 5% 30%	1948
	21st to end	Day	16% 14% 5% 10% 5% 3 3 3 5% 6% 31%	1650
March	1st to 10th	Day	19% 16% 6% 9% 4 3 3 2 3 4 31%	4480
	11th to 20th	Day	11% 10% 3 6% 4 4 4 3 5% 7% 44%	4832
	21st to end	Day	17% 12% 4 9% 5% 5% 4 3 5% 7% 30%	5681
April	1st to 10th	Day	16% 10% 4 8% 6% 4 5% 3 5% 7% 33%	2400
	11th to 20th	Day	17% 9% 3 7% 4 4 6% 4 5% 6% 35%	2374
	21st to end	Day	19% 8% 3 7% 4 4 4 3 5% 8% 35%	2588
May	1st to 10th	Day	19% 10% 3 8% 5% 5% 5% 4 6% 7% 29%	5862
	11th to 20th	Day	19% 7% 3 7% 4 4 5% 3 6% 7% 36%	5861
	21st to end	Day	12% 7% 3 7% 5% 5% 5% 5% 7% 9% 36%	6585
June	1st to 10th	Day	10% 5% 3 7% 5% 5% 5% 4 7% 8% 42%	2800
	11th to 20th	Day	9% 6% 2 6% 4 5% 5% 5% 7% 8% 43%	2800
	21st to end	Day	9% 6% 2 6% 5% 5% 5% 4 7% 10% 41%	2800
July	1st to 10th	Day	12% 7% 3 7% 5% 5% 5% 4 7% 11% 34%	4511
	11th to 20th	Day	6% 4 2 6% 4 5% 5% 4 8% 12% 45%	4440
	21st to end	Day	9% 6% 3 7% 5% 5% 6% 5% 8% 9% 37%	4670
August	1st to 10th	Day	8% 5% 2 5% 5% 4 5% 4 6% 10% 45%	4104
	11th to 20th	Day	9% 5% 2 6% 4 5% 5% 4 8% 10% 42%	3902
	21st to end	Day	7% 5% 2 6% 4 4 5% 4 6% 8% 51%	4180
September	1st to 10th	Day	11% 6% 2 6% 4 4 4 4 6% 7% 46%	2242
	11th to 20th	Day	10% 5% 2 6% 4 4 4 4 7% 7% 48%	2090
	21st to end	Day	13% 7% 2 5% 4 4 4 3 5% 6% 46%	2090
October	1st to 10th	Day	12% 6% 2 6% 4 4 4 2 5% 7% 48%	2090
	11th to 20th	Day	14% 5% 2 6% 4 5% 5% 3 6% 7% 43%	1934
	21st to end	Day	19% 8% 4 8% 5% 5% 4 3 6% 6% 34%	1881
November	1st to 10th	Day	10% 7% 2 6% 4 4 4 3 5% 7% 49%	1762
	11th to 20th	Day	16% 12% 4 7% 5% 4 4 3 5% 7% 33%	1800
	21st to end	Day	18% 12% 4 9% 4 3 4 3 5% 6% 32%	1800
December	1st to 10th	Day	15% 12% 4 9% 4 3 3 2 3 5% 40%	2930
	11th to 20th	Day	16% 15% 5% 12% 5% 5% 4 4 5% 5% 24%	3040
	21st to end	Day	27% 18% 7% 9% 5% 5% 4 3 5% 4 12%	3982
January	1st to 10th	Night	16% 15% 8% 14% 6% 4 4 3 5% 4 22%	6348
	11th to 20th	Night	13% 20% 8% 13% 7% 6% 6% 4 3 3 17%	6360
	21st to end	Night	20% 14% 6% 9% 5% 4 3 3 4 4 27%	6794
February	1st to 10th	Night	18% 15% 4 10% 5% 4 4 4 5% 5% 27%	2420
	11th to 20th	Night	15% 12% 5% 11% 4 4 3 3 5% 6% 31%	2338
	21st to end	Night	18% 10% 6% 10% 5% 4 3 3 4 5% 31%	1980
March	1st to 10th	Night	18% 12% 3 6% 4 3 3 3 4 5% 38%	5373
	11th to 20th	Night	12% 7% 2 6% 4 4 4 3 5% 7% 45%	5126
	21st to end	Night	17% 9% 4 8% 5% 4 4 3 5% 7% 34%	5289
April	1st to 10th	Night	15% 8% 3 7% 5% 4 5% 3 6% 6% 38%	2000
	11th to 20th	Night	16% 8% 2 6% 4 4 4 3 6% 8% 39%	1975
	21st to end	Night	17% 7% 3 7% 4 4 5% 5% 7% 6% 35%	1810
May	1st to 10th	Night	20% 10% 4 8% 6% 4 5% 3 5% 7% 29%	4033
	11th to 20th	Night	17% 7% 2 7% 4 3 3 4 6% 8% 38%	4032
	21st to end	Night	13% 7% 3 7% 4 4 5% 4 7% 8% 39%	4259
June	1st to 10th	Night	9% 6% 2 5% 5% 4 4 3 6% 8% 48%	1600
	11th to 20th	Night	10% 5% 3 6% 4 4 4 4 4 10% 47%	1600
	21st to end	Night	7% 6% 2 6% 5% 4 4 5% 8% 9% 45%	1600
July	1st to 10th	Night	9% 5% 1 6% 5% 5% 5% 4 6% 10% 46%	2570
	11th to 20th	Night	6% 4 1 4 2 3 5% 5% 6% 8% 56%	2530
	21st to end	Night	10% 6% 3 7% 4 5% 4 4 7% 9% 41%	2889
August	1st to 10th	Night	11% 5% 2 5% 3 4 4 4 6% 8% 49%	2825
	11th to 20th	Night	6% 6% 2 7% 5% 5% 5% 4 7% 9% 45%	2910
	21st to end	Night	6% 5% 2 5% 4 4 4 4 5% 8% 53%	3476
September	1st to 10th	Night	11% 6% 2 6% 4 3 4 3 5% 8% 48%	1918
	11th to 20th	Night	7% 4 1 5% 3 4 4 3 6% 7% 56%	2090
	21st to end	Night	12% 6% 2 4 3 4 4 3 6% 6% 50%	2090
October	1st to 10th	Night	8% 4 2 6% 4 4 3 4 5% 6% 54%	2090
	11th to 20th	Night	18% 8% 2 4 4 4 3 3 4 7% 45%	2242
	21st to end	Night	18% 8% 2 6% 4 4 5% 3 5% 6% 39%	2717
November	1st to 10th	Night	12% 8% 2 6% 3 4 3 3 5% 5% 49%	2536
	11th to 20th	Night	15% 9% 3 7% 4 4 4 3 4 7% 39%	2600
	21st to end	Night	18% 13% 4 9% 5% 5% 3 3 3 6% 30%	2600
December	1st to 10th	Night	14% 9% 4 8% 5% 4 4 3 5% 6% 38%	4250
	11th to 20th	Night	18% 15% 6% 10% 5% 4 3 3 4 5% 27%	5161
	21st to end	Night	25% 19% 6% 10% 5% 4 4 3 4 4 15%	6996

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	66% 1 5% 19% 7% 1	3618
	11th to 20th	Day	70% 2 8% 9% 9% 2	3620
	21st to end	Day	68% 2 7% 14% 7% 2	4172
February	1st to 10th	Day	63% 2 9% 15% 10% 1	1978
	11th to 20th	Day	58% 2 9% 21% 10% 1	1958
	21st to end	Day	55% 3 10% 22% 8% 2	1650
March	1st to 10th	Day	59% 2 5% 21% 11% 2	4480
	11th to 20th	Day	41% 2 9% 35% 12% 1	4832
	21st to end	Day	56% 2 12% 20% 8% 2	5683
April	1st to 10th	Day	52% 3 11% 20% 13% 1	2400
	11th to 20th	Day	49% 3 10% 25% 10% 3	2374
	21st to end	Day	49% 3 11% 23% 11% 3	2588
May	1st to 10th	Day	55% 2 12% 20% 10%	5897
	11th to 20th	Day	49% 3 12% 25% 11% 1	5865
	21st to end	Day	44% 3 11% 27% 14% 1	6599
June	1st to 10th	Day	40% 3 13% 25% 16% 3	2800
	11th to 20th	Day	36% 4 12% 26% 20% 2	2800
	21st to end	Day	39% 4 16% 21% 17% 4	2800
July	1st to 10th	Day	44% 3 11% 24% 15% 2	4442
	11th to 20th	Day	30% 4 15% 29% 20% 1	4365
	21st to end	Day	42% 5% 15% 19% 16% 3	4522
August	1st to 10th	Day	33% 4 16% 30% 15% 1	4091
	11th to 20th	Day	35% 3 13% 34% 14% 1	3941
	21st to end	Day	32% 4 12% 32% 17% 4	4179
September	1st to 10th	Day	38% 3 10% 26% 18% 4	2242
	11th to 20th	Day	34% 3 10% 26% 22% 4	2090
	21st to end	Day	39% 3 8% 26% 22% 1	2090
October	1st to 10th	Day	25% 2 9% 33% 30% 2	3480
	11th to 20th	Day	35% 2 9% 26% 26% 1	3189
	21st to end	Day	42% 2 9% 26% 19% 1	3081
November	1st to 10th	Day	35% 3 12% 29% 18% 3	1762
	11th to 20th	Day	51% 2 9% 22% 13% 3	1800
	21st to end	Day	54% 2 10% 23% 9% 1	1800
December	1st to 10th	Day	49% 1 10% 28% 12%	2930
	11th to 20th	Day	63% 3 10% 19% 4	3037
	21st to end	Day	75% 2 8% 10% 5%	3982
January	1st to 10th	Night	66% 2 7% 17% 8%	6348
	11th to 20th	Night	73% 2 5% 10% 8% 2	6360
	21st to end	Night	62% 1 9% 18% 8% 1	6794
February	1st to 10th	Night	59% 2 11% 18% 9% 1	2420
	11th to 20th	Night	55% 2 9% 20% 12% 2	2339
	21st to end	Night	56% 3 10% 19% 11% 2	1980
March	1st to 10th	Night	50% 1 6% 28% 12% 3	5373
	11th to 20th	Night	41% 2 10% 29% 17% 2	5126
	21st to end	Night	51% 3 9% 28% 8% 1	5289
April	1st to 10th	Night	46% 3 11% 25% 14% 1	2000
	11th to 20th	Night	45% 2 9% 24% 16% 4	1975
	21st to end	Night	47% 5% 9% 23% 13% 4	1810
May	1st to 10th	Night	57% 3 8% 18% 12% 2	4060
	11th to 20th	Night	44% 3 13% 26% 13% 1	4033
	21st to end	Night	43% 3 13% 25% 14% 2	4267
June	1st to 10th	Night	35% 2 10% 28% 21% 4	1600
	11th to 20th	Night	35% 4 12% 25% 21% 4	1600
	21st to end	Night	33% 5% 16% 25% 17% 4	1600
July	1st to 10th	Night	35% 4 11% 28% 15% 6%	2530
	11th to 20th	Night	25% 3 13% 33% 24% 2	2482
	21st to end	Night	40% 4 14% 23% 16% 4	2797
August	1st to 10th	Night	33% 4 14% 33% 14% 1	2814
	11th to 20th	Night	36% 4 12% 29% 17% 1	2937
	21st to end	Night	30% 3 12% 30% 22% 3	3476
September	1st to 10th	Night	35% 3 11% 24% 21% 6%	1918
	11th to 20th	Night	29% 3 9% 28% 27% 4	2090
	21st to end	Night	35% 3 10% 25% 24% 4	2090
October	1st to 10th	Night	22% 2 6% 31% 38% 2	3480
	11th to 20th	Night	30% 1 9% 25% 33% 1	3726
	21st to end	Night	34% 2 7% 29% 24% 3	4467
November	1st to 10th	Night	38% 3 8% 27% 22% 3	2536
	11th to 20th	Night	46% 2 8% 24% 17% 3	2600
	21st to end	Night	57% 2 8% 24% 9%	2600
December	1st to 10th	Night	48% 2 11% 27% 11%	4250
	11th to 20th	Night	62% 2 10% 16% 9% 1	5163
	21st to end	Night	74% 2 9% 11% 4	6996

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	25% 14% 34% 21% 5% 1	300
	11th to 20th	Day	19% 18% 38% 19% 5% 1	300
	21st to end	Day	31% 12% 30% 21% 6%	330
February	1st to 10th	Day	26% 13% 35% 21% 5%	300
	11th to 20th	Day	24% 15% 38% 17% 6%	300
	21st to end	Day	25% 11% 43% 17% 4	249
March	1st to 10th	Day	24% 17% 35% 21% 2 1	300
	11th to 20th	Day	25% 11% 36% 19% 7% 1	430
	21st to end	Day	31% 11% 31% 19% 7% 1	550
April	1st to 10th	Day	21% 12% 35% 21% 9% 2	500
	11th to 20th	Day	21% 14% 29% 22% 12% 3	492
	21st to end	Day	24% 10% 33% 20% 10% 2	500
May	1st to 10th	Day	23% 8% 31% 23% 12% 2	503
	11th to 20th	Day	23% 6% 23% 26% 15% 7%	527
	21st to end	Day	15% 4 26% 25% 19% 12%	634
June	1st to 10th	Day	12% 5% 25% 31% 21% 7%	730
	11th to 20th	Day	14% 3 21% 34% 20% 8%	730
	21st to end	Day	13% 3 24% 29% 22% 10%	730
July	1st to 10th	Day	13% 1 15% 27% 26% 19%	697
	11th to 20th	Day	8% 2 17% 34% 25% 15%	668
	21st to end	Day	11% 1 13% 30% 31% 14%	658
August	1st to 10th	Day	11% 1 10% 30% 27% 21%	486
	11th to 20th	Day	13% 1 15% 28% 28% 15%	479
	21st to end	Day	9% 1 11% 27% 34% 17%	539
September	1st to 10th	Day	13% 2 13% 27% 33% 12%	490
	11th to 20th	Day	10% 2 13% 24% 33% 19%	490
	21st to end	Day	19% 6% 19% 21% 23% 12%	490
October	1st to 10th	Day	11% 6% 19% 35% 19% 9%	490
	11th to 20th	Day	14% 13% 33% 23% 14% 3	428
	21st to end	Day	28% 8% 38% 21% 5%	330
November	1st to 10th	Day	13% 11% 33% 25% 14% 4	300
	11th to 20th	Day	24% 13% 33% 19% 9% 2	300
	21st to end	Day	27% 10% 35% 23% 6%	300
December	1st to 10th	Day	21% 16% 34% 22% 5% 1	300
	11th to 20th	Day	23% 12% 36% 22% 6% 1	300
	21st to end	Day	33% 10% 32% 20% 5%	330
January	1st to 10th	Night	25% 13% 33% 25% 5%	1000
	11th to 20th	Night	26% 12% 36% 22% 4	1000
	21st to end	Night	25% 12% 35% 25% 4	1015
February	1st to 10th	Night	27% 9% 34% 27% 3	800
	11th to 20th	Night	21% 12% 38% 26% 3	783
	21st to end	Night	23% 10% 40% 23% 3	660
March	1st to 10th	Night	20% 14% 33% 27% 7%	800
	11th to 20th	Night	20% 11% 36% 26% 7% 1	800
	21st to end	Night	25% 9% 32% 29% 5% 1	805
April	1st to 10th	Night	19% 9% 37% 27% 8%	600
	11th to 20th	Night	19% 9% 31% 30% 10% 1	593
	21st to end	Night	21% 6% 39% 26% 8% 1	600
May	1st to 10th	Night	23% 6% 31% 29% 11%	600
	11th to 20th	Night	21% 3 23% 31% 19% 2	591
	21st to end	Night	11% 3 22% 38% 24% 2	650
June	1st to 10th	Night	12% 2 21% 45% 19% 1	600
	11th to 20th	Night	12% 3 18% 43% 22% 3	600
	21st to end	Night	10% 1 21% 39% 28% 2	600
July	1st to 10th	Night	11% 1 9% 39% 34% 7%	570
	11th to 20th	Night	7% 1 13% 40% 33% 5%	552
	21st to end	Night	9% 1 11% 41% 35% 3	624
August	1st to 10th	Night	11% 1 9% 40% 36% 4	567
	11th to 20th	Night	7% 1 11% 43% 32% 6%	564
	21st to end	Night	9% 1 11% 34% 40% 5%	627
September	1st to 10th	Night	13% 1 12% 34% 34% 5%	588
	11th to 20th	Night	10% 1 13% 34% 36% 5%	760
	21st to end	Night	15% 4 18% 35% 26% 3	760
October	1st to 10th	Night	12% 3 22% 38% 21% 4	760
	11th to 20th	Night	22% 7% 28% 29% 14%	760
	21st to end	Night	23% 8% 33% 28% 8%	836
November	1st to 10th	Night	18% 7% 31% 31% 12% 1	780
	11th to 20th	Night	19% 13% 31% 28% 8% 1	800
	21st to end	Night	26% 11% 28% 28% 7% 1	800
December	1st to 10th	Night	25% 9% 35% 25% 5%	800
	11th to 20th	Night	26% 8% 33% 25% 7%	975
	21st to end	Night	31% 11% 30% 22% 5%	1100

Page generated at 2025-07-03 01:30:16. Version ac07

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