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 2026-10-29.

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% 9% 4 8% 5% 5% 5% 4 6% 7% 35%	148922
	Night	14% 10% 4 8% 5% 4 4 4 5% 7% 36%	143357
Transparency	Day	47% 3 11% 24% 13% 2	152519
	Night	48% 3 10% 23% 15% 2	147836
Seeing	Day	18% 7% 25% 25% 17% 7%	18321
	Night	19% 7% 27% 31% 15% 2	28056

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	14% 15% 8% 13% 6% 4 3 3 5% 6% 22%	4691
	11th to 20th	Day	10% 14% 7% 14% 7% 8% 7% 5% 5% 4 19%	4710
	21st to end	Day	18% 17% 6% 13% 5% 4 4 4 5% 4 20%	5398
February	1st to 10th	Day	17% 14% 7% 10% 6% 6% 3 3 4 6% 24%	2077
	11th to 20th	Day	14% 12% 4 11% 7% 6% 4 2 4 5% 30%	2048
	21st to end	Day	15% 14% 5% 11% 5% 3 3 3 5% 5% 31%	1730
March	1st to 10th	Day	19% 16% 6% 9% 4 3 3 2 3 4 31%	4580
	11th to 20th	Day	11% 10% 3 6% 4 4 4 3 5% 7% 43%	4939
	21st to end	Day	16% 12% 4 9% 5% 5% 4 3 5% 7% 30%	5806
April	1st to 10th	Day	16% 10% 4 8% 6% 4 5% 3 5% 7% 33%	2520
	11th to 20th	Day	17% 9% 3 7% 4 4 6% 4 5% 7% 35%	2494
	21st to end	Day	19% 8% 3 7% 4 4 4 3 5% 8% 35%	2717
May	1st to 10th	Day	18% 9% 3 7% 5% 5% 5% 4 6% 7% 31%	7616
	11th to 20th	Day	17% 7% 3 7% 4 4 5% 4 5% 7% 38%	7626
	21st to end	Day	14% 8% 3 8% 5% 5% 5% 5% 7% 8% 33%	8585
June	1st to 10th	Day	10% 5% 3 7% 5% 5% 4 4 7% 8% 41%	2940
	11th to 20th	Day	9% 6% 2 5% 4 5% 5% 5% 7% 8% 43%	2940
	21st to end	Day	9% 6% 2 6% 5% 5% 5% 4 7% 10% 40%	2940
July	1st to 10th	Day	10% 6% 2 7% 5% 5% 5% 4 7% 10% 39%	8280
	11th to 20th	Day	8% 5% 2 7% 4 5% 5% 4 8% 12% 41%	8280
	21st to end	Day	9% 6% 3 8% 5% 5% 6% 5% 7% 8% 37%	8722
August	1st to 10th	Day	11% 6% 2 6% 5% 4 5% 4 6% 9% 42%	6014
	11th to 20th	Day	11% 7% 3 8% 5% 5% 5% 4 7% 9% 34%	5749
	21st to end	Day	5% 4 2 5% 3 4 5% 4 6% 9% 53%	6080
September	1st to 10th	Day	10% 6% 2 5% 4 4 4 4 6% 7% 48%	2478
	11th to 20th	Day	9% 5% 2 6% 4 4 4 4 7% 8% 48%	2310
	21st to end	Day	14% 7% 2 6% 4 4 4 3 5% 6% 46%	2310
October	1st to 10th	Day	11% 6% 2 6% 4 4 4 3 5% 6% 49%	2310
	11th to 20th	Day	13% 6% 2 6% 4 5% 5% 3 6% 7% 44%	2137
	21st to end	Day	18% 8% 3 8% 5% 5% 4 3 6% 6% 35%	2052
November	1st to 10th	Day	10% 7% 2 6% 4 4 4 3 5% 7% 49%	1852
	11th to 20th	Day	16% 12% 4 7% 5% 3 4 3 5% 7% 33%	1890
	21st to end	Day	18% 12% 4 9% 4 3 4 3 5% 6% 32%	1890
December	1st to 10th	Day	14% 11% 5% 9% 4 3 3 2 3 5% 40%	3020
	11th to 20th	Day	16% 15% 5% 12% 5% 5% 4 3 5% 5% 24%	3121
	21st to end	Day	26% 19% 7% 10% 5% 5% 4 3 5% 4 12%	4070
January	1st to 10th	Night	15% 14% 7% 13% 6% 4 4 4 5% 5% 23%	8232
	11th to 20th	Night	10% 17% 8% 14% 7% 6% 6% 4 4 4 20%	8280
	21st to end	Night	17% 13% 5% 8% 6% 5% 4 4 5% 6% 27%	8800
February	1st to 10th	Night	17% 15% 4 10% 6% 4 4 4 5% 5% 27%	2541
	11th to 20th	Night	15% 12% 5% 11% 4 5% 3 3 5% 6% 32%	2458
	21st to end	Night	18% 10% 6% 11% 5% 4 3 3 5% 5% 31%	2076
March	1st to 10th	Night	18% 12% 3 6% 4 3 3 3 4 5% 38%	5493
	11th to 20th	Night	12% 7% 2 6% 4 5% 4 4 5% 7% 44%	5239
	21st to end	Night	17% 9% 4 8% 5% 4 4 4 5% 7% 34%	5406
April	1st to 10th	Night	15% 8% 3 7% 5% 4 5% 3 6% 6% 38%	2100
	11th to 20th	Night	15% 8% 2 6% 5% 4 4 3 6% 8% 39%	2075
	21st to end	Night	17% 7% 3 7% 4 4 5% 5% 7% 7% 36%	1901
May	1st to 10th	Night	20% 9% 3 8% 5% 4 4 3 5% 6% 30%	5237
	11th to 20th	Night	15% 7% 2 6% 4 3 3 3 5% 8% 41%	5234
	21st to end	Night	13% 7% 3 8% 5% 4 5% 4 7% 8% 36%	5560
June	1st to 10th	Night	9% 6% 2 5% 5% 4 4 3 6% 8% 48%	1680
	11th to 20th	Night	10% 5% 3 6% 4 4 4 4 4 10% 47%	1680
	21st to end	Night	7% 6% 2 6% 5% 4 4 5% 8% 9% 45%	1680
July	1st to 10th	Night	8% 5% 2 6% 5% 5% 5% 4 7% 9% 46%	4708
	11th to 20th	Night	8% 6% 2 6% 4 4 4 4 6% 8% 48%	4707
	21st to end	Night	8% 6% 3 7% 4 5% 5% 5% 7% 9% 42%	5360
August	1st to 10th	Night	13% 6% 2 5% 3 3 4 4 5% 7% 47%	4135
	11th to 20th	Night	9% 8% 3 8% 5% 5% 5% 4 6% 8% 39%	4280
	21st to end	Night	5% 4 2 5% 4 4 4 4 6% 9% 54%	5046
September	1st to 10th	Night	10% 6% 2 6% 4 3 4 3 5% 8% 50%	2120
	11th to 20th	Night	8% 4 2 5% 4 4 4 3 5% 7% 55%	2310
	21st to end	Night	12% 6% 2 5% 3 4 4 3 6% 6% 50%	2310
October	1st to 10th	Night	8% 4 2 5% 3 4 4 4 5% 6% 55%	2310
	11th to 20th	Night	17% 8% 2 4 4 4 3 3 4 7% 46%	2478
	21st to end	Night	17% 8% 2 6% 4 4 5% 3 5% 6% 40%	2965
November	1st to 10th	Night	12% 8% 2 6% 3 4 3 3 5% 6% 49%	2666
	11th to 20th	Night	15% 9% 4 7% 4 4 4 3 4 7% 39%	2730
	21st to end	Night	19% 13% 4 9% 5% 5% 4 3 3 6% 30%	2730
December	1st to 10th	Night	14% 9% 4 8% 5% 4 4 3 5% 6% 37%	4380
	11th to 20th	Night	18% 15% 6% 10% 5% 4 3 3 4 5% 27%	5300
	21st to end	Night	26% 19% 6% 10% 5% 4 4 3 4 4 15%	7150

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	65% 1 10% 18% 5% 1	4692
	11th to 20th	Day	69% 2 7% 11% 9% 2	4710
	21st to end	Day	69% 2 7% 15% 6% 2	5398
February	1st to 10th	Day	63% 2 9% 16% 9% 1	2077
	11th to 20th	Day	58% 2 9% 21% 9% 1	2058
	21st to end	Day	55% 3 10% 23% 8% 2	1730
March	1st to 10th	Day	59% 2 5% 21% 11% 2	4580
	11th to 20th	Day	42% 2 9% 34% 12% 1	4939
	21st to end	Day	56% 2 13% 20% 8% 2	5808
April	1st to 10th	Day	52% 3 11% 20% 13% 1	2520
	11th to 20th	Day	48% 3 10% 25% 10% 3	2494
	21st to end	Day	48% 3 11% 24% 11% 3	2717
May	1st to 10th	Day	52% 3 13% 21% 11%	7651
	11th to 20th	Day	46% 3 13% 23% 15% 1	7630
	21st to end	Day	49% 3 10% 23% 13% 3	8599
June	1st to 10th	Day	40% 3 13% 25% 17% 3	2940
	11th to 20th	Day	36% 4 12% 26% 20% 2	2940
	21st to end	Day	39% 4 16% 21% 16% 4	2940
July	1st to 10th	Day	40% 3 12% 28% 16% 1	8211
	11th to 20th	Day	37% 4 14% 30% 14% 1	8205
	21st to end	Day	43% 4 12% 25% 15% 2	8530
August	1st to 10th	Day	39% 4 14% 25% 16% 2	6001
	11th to 20th	Day	45% 4 12% 28% 10%	5788
	21st to end	Day	28% 3 13% 36% 16% 3	6079
September	1st to 10th	Day	36% 3 10% 28% 19% 4	2478
	11th to 20th	Day	33% 3 10% 27% 23% 3	2310
	21st to end	Day	39% 3 8% 25% 24% 1	2310
October	1st to 10th	Day	25% 2 8% 33% 30% 2	3700
	11th to 20th	Day	35% 2 9% 26% 26% 2	3392
	21st to end	Day	42% 2 8% 26% 20% 1	3252
November	1st to 10th	Day	35% 3 12% 29% 18% 3	1852
	11th to 20th	Day	51% 2 9% 22% 13% 3	1890
	21st to end	Day	55% 2 10% 23% 9% 1	1890
December	1st to 10th	Day	49% 1 10% 27% 12%	3020
	11th to 20th	Day	63% 3 10% 19% 4	3118
	21st to end	Day	75% 2 8% 10% 5%	4070
January	1st to 10th	Night	64% 2 9% 18% 7%	8233
	11th to 20th	Night	68% 2 6% 12% 10% 1	8280
	21st to end	Night	59% 1 10% 21% 7% 1	8800
February	1st to 10th	Night	59% 2 10% 18% 9% 1	2541
	11th to 20th	Night	55% 2 9% 21% 12% 2	2459
	21st to end	Night	56% 2 10% 19% 11% 2	2076
March	1st to 10th	Night	51% 1 6% 27% 12% 2	5493
	11th to 20th	Night	41% 2 10% 29% 17% 2	5239
	21st to end	Night	51% 3 9% 28% 8% 1	5406
April	1st to 10th	Night	46% 3 11% 25% 14% 1	2100
	11th to 20th	Night	45% 2 10% 24% 16% 4	2075
	21st to end	Night	46% 5% 9% 24% 13% 3	1901
May	1st to 10th	Night	56% 3 7% 20% 13% 1	5264
	11th to 20th	Night	42% 3 12% 26% 16% 1	5235
	21st to end	Night	45% 3 13% 22% 13% 4	5570
June	1st to 10th	Night	36% 2 10% 27% 21% 4	1680
	11th to 20th	Night	36% 4 11% 25% 21% 4	1680
	21st to end	Night	34% 5% 15% 24% 17% 4	1680
July	1st to 10th	Night	35% 4 11% 29% 17% 4	4670
	11th to 20th	Night	34% 3 13% 31% 18% 1	4662
	21st to end	Night	39% 3 13% 27% 16% 3	5240
August	1st to 10th	Night	36% 4 13% 27% 18% 1	4124
	11th to 20th	Night	43% 4 16% 23% 14% 1	4307
	21st to end	Night	28% 3 14% 33% 21% 2	5046
September	1st to 10th	Night	34% 3 10% 26% 21% 6%	2120
	11th to 20th	Night	29% 3 9% 28% 27% 3	2310
	21st to end	Night	35% 3 10% 24% 24% 3	2310
October	1st to 10th	Night	21% 2 6% 30% 38% 2	3700
	11th to 20th	Night	31% 1 8% 25% 33% 2	3962
	21st to end	Night	35% 2 7% 29% 24% 4	4715
November	1st to 10th	Night	38% 3 8% 27% 22% 3	2666
	11th to 20th	Night	46% 2 8% 24% 17% 3	2730
	21st to end	Night	57% 2 8% 23% 9%	2730
December	1st to 10th	Night	49% 2 11% 27% 11%	4380
	11th to 20th	Night	62% 2 10% 17% 9% 1	5302
	21st to end	Night	74% 2 9% 11% 4	7150

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% 14% 33% 22% 5% 1	330
	11th to 20th	Day	19% 21% 37% 18% 5% 1	330
	21st to end	Day	30% 14% 31% 20% 6%	363
February	1st to 10th	Day	25% 12% 35% 22% 5%	330
	11th to 20th	Day	23% 15% 39% 17% 6%	330
	21st to end	Day	24% 12% 44% 16% 3	273
March	1st to 10th	Day	24% 16% 38% 19% 2 1	330
	11th to 20th	Day	26% 12% 36% 18% 7% 1	467
	21st to end	Day	29% 13% 31% 19% 7% 1	594
April	1st to 10th	Day	21% 12% 36% 20% 8% 2	540
	11th to 20th	Day	20% 15% 30% 21% 12% 2	532
	21st to end	Day	24% 10% 33% 21% 11% 2	540
May	1st to 10th	Day	23% 9% 33% 22% 11% 2	543
	11th to 20th	Day	23% 7% 24% 26% 14% 6%	567
	21st to end	Day	16% 4 25% 24% 20% 11%	681
June	1st to 10th	Day	12% 5% 25% 30% 21% 7%	780
	11th to 20th	Day	14% 4 22% 33% 19% 8%	780
	21st to end	Day	13% 4 23% 29% 22% 9%	780
July	1st to 10th	Day	12% 1 14% 28% 27% 18%	771
	11th to 20th	Day	8% 2 15% 34% 26% 14%	768
	21st to end	Day	11% 2 14% 30% 31% 13%	759
August	1st to 10th	Day	11% 1 10% 29% 27% 22%	566
	11th to 20th	Day	14% 1 14% 27% 29% 14%	559
	21st to end	Day	8% 2 12% 28% 34% 16%	627
September	1st to 10th	Day	11% 2 14% 28% 32% 13%	570
	11th to 20th	Day	10% 1 12% 24% 34% 19%	570
	21st to end	Day	20% 5% 18% 21% 23% 12%	570
October	1st to 10th	Day	11% 5% 18% 36% 20% 9%	570
	11th to 20th	Day	14% 12% 31% 25% 15% 3	501
	21st to end	Day	26% 9% 35% 21% 7% 2	387
November	1st to 10th	Day	12% 13% 33% 25% 13% 4	330
	11th to 20th	Day	24% 14% 32% 19% 9% 2	330
	21st to end	Day	28% 10% 35% 22% 5%	330
December	1st to 10th	Day	20% 15% 37% 22% 5% 1	330
	11th to 20th	Day	22% 13% 36% 22% 5% 1	330
	21st to end	Day	32% 11% 33% 20% 5%	363
January	1st to 10th	Night	24% 12% 34% 25% 5%	1050
	11th to 20th	Night	25% 12% 37% 21% 4	1050
	21st to end	Night	24% 12% 36% 24% 3	1066
February	1st to 10th	Night	26% 9% 34% 28% 3	840
	11th to 20th	Night	21% 12% 38% 26% 3	823
	21st to end	Night	23% 11% 41% 23% 3	692
March	1st to 10th	Night	21% 14% 32% 26% 7%	840
	11th to 20th	Night	20% 11% 36% 25% 7% 1	840
	21st to end	Night	25% 9% 32% 30% 5% 1	845
April	1st to 10th	Night	19% 10% 37% 26% 8%	630
	11th to 20th	Night	19% 9% 32% 30% 9% 1	623
	21st to end	Night	20% 6% 38% 27% 8% 1	630
May	1st to 10th	Night	23% 6% 32% 29% 10%	630
	11th to 20th	Night	20% 4 24% 31% 19% 2	621
	21st to end	Night	11% 3 22% 39% 24% 2	683
June	1st to 10th	Night	12% 2 21% 46% 19%	630
	11th to 20th	Night	12% 3 18% 43% 21% 3	630
	21st to end	Night	11% 1 20% 39% 27% 2	630
July	1st to 10th	Night	11% 1 9% 39% 35% 7%	615
	11th to 20th	Night	7% 1 13% 39% 34% 5%	612
	21st to end	Night	9% 1 12% 40% 36% 3	690
August	1st to 10th	Night	11% 1 9% 40% 35% 3	627
	11th to 20th	Night	8% 1 10% 43% 32% 6%	624
	21st to end	Night	8% 1 11% 37% 39% 5%	693
September	1st to 10th	Night	12% 2 12% 35% 34% 5%	650
	11th to 20th	Night	10% 1 13% 36% 35% 5%	840
	21st to end	Night	15% 4 17% 35% 26% 3	840
October	1st to 10th	Night	11% 3 22% 39% 21% 4	840
	11th to 20th	Night	21% 7% 28% 30% 14%	840
	21st to end	Night	21% 8% 32% 29% 9%	913
November	1st to 10th	Night	18% 7% 32% 31% 12% 1	820
	11th to 20th	Night	19% 13% 32% 27% 8% 1	840
	21st to end	Night	26% 12% 27% 27% 7%	840
December	1st to 10th	Night	25% 9% 35% 25% 5%	840
	11th to 20th	Night	26% 9% 33% 25% 7%	1024
	21st to end	Night	32% 11% 30% 22% 4	1155

Page generated at 2026-10-26 04:37:48. Version ac07

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