Cherry Hill Farm
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cherry Hill Farm clear sky chart from 2005-11-06 to 2025-01-07.

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% 5% 2 5% 4 4 4 4 6% 8% 44%	105233
	Night	15% 5% 2 5% 4 4 4 4 5% 7% 44%	103756
Transparency	Day	21% 46% 7% 12% 11% 3	108962
	Night	22% 46% 6% 11% 11% 4	108153
Seeing	Day	17% 9% 21% 25% 19% 10%	15329
	Night	17% 6% 22% 32% 20% 3	25434

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	17% 4 1 3 3 2 3 2 4 7% 54%	2890
	11th to 20th	Day	15% 6% 2 4 3 3 3 2 3 4 54%	2840
	21st to end	Day	25% 4 2 4 2 2 2 2 4 5% 47%	3124
February	1st to 10th	Day	15% 7% 2 4 4 3 4 3 5% 7% 45%	1763
	11th to 20th	Day	20% 6% 2 5% 3 3 3 3 4 5% 46%	1848
	21st to end	Day	19% 6% 2 6% 4 4 4 3 5% 5% 42%	1570
March	1st to 10th	Day	25% 6% 2 5% 3 3 3 2 4 5% 44%	3418
	11th to 20th	Day	13% 5% 2 4 4 3 4 3 4 5% 53%	3480
	21st to end	Day	21% 5% 2 4 3 3 4 3 4 8% 43%	3815
April	1st to 10th	Day	12% 5% 1 4 4 4 4 3 5% 8% 49%	2090
	11th to 20th	Day	14% 5% 2 5% 4 5% 4 4 6% 6% 47%	2242
	21st to end	Day	14% 4 1 5% 3 5% 4 4 6% 6% 48%	2470
May	1st to 10th	Day	11% 7% 2 7% 5% 6% 6% 4 6% 9% 38%	4082
	11th to 20th	Day	17% 8% 3 6% 5% 5% 4 4 6% 7% 36%	4081
	21st to end	Day	9% 4 2 5% 4 5% 5% 5% 7% 10% 44%	4476
June	1st to 10th	Day	10% 6% 3 7% 5% 6% 6% 6% 8% 11% 35%	2470
	11th to 20th	Day	8% 4 2 6% 5% 4 6% 6% 9% 11% 39%	2470
	21st to end	Day	8% 4 3 5% 6% 5% 6% 6% 10% 9% 38%	2470
July	1st to 10th	Day	8% 5% 2 7% 5% 7% 7% 6% 8% 10% 36%	4120
	11th to 20th	Day	8% 5% 2 7% 5% 7% 7% 5% 8% 10% 35%	4120
	21st to end	Day	9% 8% 3 10% 8% 8% 8% 6% 9% 9% 22%	4466
August	1st to 10th	Day	16% 6% 2 7% 5% 6% 6% 5% 7% 10% 29%	4104
	11th to 20th	Day	8% 5% 2 6% 5% 6% 6% 6% 9% 12% 36%	4044
	21st to end	Day	7% 3 1 5% 4 4 4 3 6% 9% 52%	4202
September	1st to 10th	Day	10% 4 2 7% 5% 5% 5% 4 6% 9% 43%	2090
	11th to 20th	Day	17% 6% 2 6% 5% 3 4 4 6% 7% 41%	2090
	21st to end	Day	18% 4 2 6% 3 4 4 4 5% 7% 42%	2090
October	1st to 10th	Day	16% 4 1 4 3 3 2 2 4 6% 55%	2032
	11th to 20th	Day	13% 4 2 4 2 2 2 2 4 5% 61%	1900
	21st to end	Day	14% 4 2 3 3 2 3 2 3 4 59%	2090
November	1st to 10th	Day	14% 5% 2 5% 2 2 3 3 3 5% 56%	1917
	11th to 20th	Day	15% 4 1 3 3 3 3 3 5% 5% 54%	1800
	21st to end	Day	15% 4 1 4 3 3 3 2 5% 6% 53%	1800
December	1st to 10th	Day	15% 5% 2 4 3 3 3 3 4 5% 54%	2930
	11th to 20th	Day	19% 5% 2 4 3 3 4 4 6% 6% 44%	3373
	21st to end	Day	23% 4 2 3 2 3 3 2 4 6% 48%	4466
January	1st to 10th	Night	17% 4 1 3 3 3 3 3 4 5% 53%	4188
	11th to 20th	Night	13% 6% 2 5% 4 3 4 3 5% 5% 51%	4120
	21st to end	Night	24% 6% 2 4 3 3 3 3 3 5% 44%	4532
February	1st to 10th	Night	15% 5% 2 5% 4 3 3 4 5% 5% 49%	2413
	11th to 20th	Night	20% 6% 2 4 4 3 3 4 4 4 46%	2218
	21st to end	Night	16% 6% 2 6% 4 3 5% 4 5% 6% 42%	1884
March	1st to 10th	Night	23% 7% 2 5% 4 3 4 3 4 6% 39%	3433
	11th to 20th	Night	11% 5% 1 4 3 3 4 3 5% 8% 53%	3480
	21st to end	Night	21% 4 2 5% 4 3 4 3 5% 6% 43%	3817
April	1st to 10th	Night	13% 5% 1 5% 3 3 3 4 5% 7% 49%	2090
	11th to 20th	Night	14% 5% 2 6% 3 3 3 3 6% 7% 49%	1901
	21st to end	Night	12% 5% 2 5% 5% 3 4 4 5% 6% 50%	1710
May	1st to 10th	Night	14% 6% 2 7% 5% 4 5% 4 6% 8% 40%	2813
	11th to 20th	Night	17% 6% 2 7% 5% 4 4 3 6% 7% 38%	2812
	21st to end	Night	9% 5% 2 6% 5% 4 5% 4 6% 10% 43%	3079
June	1st to 10th	Night	10% 5% 3 6% 5% 5% 7% 6% 8% 12% 32%	1710
	11th to 20th	Night	11% 5% 2 6% 5% 5% 5% 5% 7% 11% 38%	1710
	21st to end	Night	9% 5% 2 7% 5% 5% 6% 5% 8% 10% 38%	1710
July	1st to 10th	Night	9% 6% 3 9% 6% 7% 7% 7% 8% 10% 29%	2840
	11th to 20th	Night	8% 5% 2 7% 6% 6% 7% 5% 9% 13% 31%	2840
	21st to end	Night	12% 9% 4 10% 6% 7% 7% 5% 10% 10% 20%	3087
August	1st to 10th	Night	14% 9% 4 8% 6% 5% 5% 5% 8% 10% 27%	2825
	11th to 20th	Night	12% 6% 3 7% 6% 6% 7% 5% 7% 10% 30%	2785
	21st to end	Night	7% 5% 2 7% 4 5% 6% 4 6% 8% 44%	3416
September	1st to 10th	Night	12% 6% 2 6% 4 5% 5% 5% 7% 8% 40%	2090
	11th to 20th	Night	18% 6% 3 8% 5% 4 5% 4 5% 7% 35%	2090
	21st to end	Night	19% 6% 2 5% 4 4 4 3 5% 6% 43%	2090
October	1st to 10th	Night	18% 4 1 4 3 3 4 3 4 5% 50%	2147
	11th to 20th	Night	15% 5% 2 4 3 2 3 2 5% 6% 53%	2280
	21st to end	Night	14% 4 1 4 2 3 3 3 4 4 58%	2508
November	1st to 10th	Night	15% 4 2 5% 3 3 3 3 4 5% 53%	2376
	11th to 20th	Night	14% 5% 2 4 3 3 4 3 4 5% 53%	2600
	21st to end	Night	15% 5% 1 4 3 3 4 3 5% 7% 51%	2600
December	1st to 10th	Night	15% 5% 2 4 2 3 3 2 4 5% 55%	4250
	11th to 20th	Night	20% 6% 2 5% 3 3 4 3 4 5% 44%	4822
	21st to end	Night	22% 4 2 4 3 3 3 3 4 6% 47%	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	20% 36% 2 17% 19% 6%	2891
	11th to 20th	Day	21% 37% 3 10% 24% 4	2840
	21st to end	Day	26% 40% 3 10% 18% 3	3124
February	1st to 10th	Day	14% 65% 3 9% 7% 2	1763
	11th to 20th	Day	16% 64% 3 7% 7% 2	1858
	21st to end	Day	17% 66% 3 4 8% 2	1570
March	1st to 10th	Day	32% 41% 5% 10% 6% 6%	3418
	11th to 20th	Day	15% 41% 4 10% 20% 10%	3480
	21st to end	Day	24% 41% 4 14% 15% 3	3815
April	1st to 10th	Day	13% 66% 4 5% 9% 2	2090
	11th to 20th	Day	15% 68% 3 7% 5% 2	2242
	21st to end	Day	13% 65% 5% 10% 6% 1	2470
May	1st to 10th	Day	25% 46% 9% 12% 7% 1	4120
	11th to 20th	Day	28% 42% 6% 14% 9%	4085
	21st to end	Day	17% 45% 12% 14% 12% 1	4489
June	1st to 10th	Day	15% 67% 6% 7% 3 1	2470
	11th to 20th	Day	10% 68% 7% 9% 5%	2470
	21st to end	Day	14% 67% 8% 7% 4	2470
July	1st to 10th	Day	24% 43% 14% 14% 5%	4055
	11th to 20th	Day	25% 41% 19% 14% 1	4051
	21st to end	Day	40% 42% 8% 8% 2 1	4324
August	1st to 10th	Day	33% 40% 11% 14% 2	4091
	11th to 20th	Day	19% 43% 18% 11% 9% 2	4083
	21st to end	Day	12% 39% 9% 24% 16% 1	4202
September	1st to 10th	Day	14% 63% 5% 9% 8% 1	2090
	11th to 20th	Day	18% 62% 5% 8% 6% 2	2090
	21st to end	Day	18% 61% 6% 9% 6%	2090
October	1st to 10th	Day	15% 38% 4 13% 22% 7%	3370
	11th to 20th	Day	8% 36% 3 10% 20% 22%	3140
	21st to end	Day	18% 36% 2 17% 13% 14%	3428
November	1st to 10th	Day	20% 56% 3 9% 10% 3	1917
	11th to 20th	Day	15% 57% 3 9% 12% 4	1800
	21st to end	Day	13% 57% 5% 10% 12% 3	1800
December	1st to 10th	Day	19% 36% 3 13% 20% 8%	2930
	11th to 20th	Day	28% 33% 6% 10% 17% 6%	3370
	21st to end	Day	29% 27% 6% 23% 13% 2	4466
January	1st to 10th	Night	21% 36% 4 12% 20% 6%	4188
	11th to 20th	Night	19% 39% 4 10% 22% 6%	4120
	21st to end	Night	28% 40% 4 8% 15% 4	4532
February	1st to 10th	Night	13% 65% 4 8% 9% 1	2413
	11th to 20th	Night	17% 64% 3 6% 7% 2	2219
	21st to end	Night	16% 65% 4 6% 7% 3	1884
March	1st to 10th	Night	33% 45% 6% 8% 6% 3	3433
	11th to 20th	Night	13% 41% 4 12% 18% 13%	3480
	21st to end	Night	25% 41% 4 10% 12% 6%	3817
April	1st to 10th	Night	13% 66% 3 7% 8% 2	2090
	11th to 20th	Night	15% 67% 3 7% 5% 2	1901
	21st to end	Night	12% 66% 4 10% 7% 1	1710
May	1st to 10th	Night	26% 44% 7% 15% 7% 1	2840
	11th to 20th	Night	24% 43% 9% 13% 10%	2813
	21st to end	Night	15% 45% 9% 21% 9% 1	3087
June	1st to 10th	Night	15% 68% 6% 6% 4 1	1710
	11th to 20th	Night	12% 69% 8% 7% 4	1710
	21st to end	Night	13% 66% 9% 6% 6%	1710
July	1st to 10th	Night	29% 42% 13% 12% 4	2795
	11th to 20th	Night	26% 42% 17% 14% 1	2786
	21st to end	Night	41% 41% 8% 7% 1 1	2988
August	1st to 10th	Night	36% 41% 13% 9% 1	2814
	11th to 20th	Night	29% 43% 13% 9% 5%	2812
	21st to end	Night	18% 40% 7% 23% 11% 1	3416
September	1st to 10th	Night	14% 63% 7% 8% 7% 1	2090
	11th to 20th	Night	19% 63% 6% 6% 5% 1	2090
	21st to end	Night	19% 61% 6% 8% 5%	2090
October	1st to 10th	Night	21% 39% 5% 11% 18% 6%	3576
	11th to 20th	Night	9% 37% 3 12% 21% 18%	3779
	21st to end	Night	19% 36% 2 13% 17% 13%	4120
November	1st to 10th	Night	20% 56% 3 9% 8% 4	2376
	11th to 20th	Night	15% 57% 4 7% 12% 6%	2600
	21st to end	Night	14% 57% 3 11% 13% 2	2600
December	1st to 10th	Night	20% 35% 3 15% 20% 6%	4250
	11th to 20th	Night	31% 33% 5% 11% 14% 6%	4824
	21st to end	Night	29% 28% 8% 19% 15% 1	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	22% 18% 35% 18% 6%	288
	11th to 20th	Day	26% 19% 31% 18% 6%	270
	21st to end	Day	22% 17% 40% 17% 4	297
February	1st to 10th	Day	20% 19% 34% 20% 6% 1	270
	11th to 20th	Day	34% 21% 30% 13% 1	270
	21st to end	Day	29% 24% 31% 12% 4	225
March	1st to 10th	Day	21% 14% 31% 24% 9% 1	443
	11th to 20th	Day	21% 13% 34% 25% 6% 1	460
	21st to end	Day	22% 16% 30% 24% 7% 1	506
April	1st to 10th	Day	18% 16% 30% 22% 12% 2	460
	11th to 20th	Day	16% 16% 27% 22% 17% 3	452
	21st to end	Day	19% 10% 26% 26% 14% 6%	460
May	1st to 10th	Day	14% 11% 30% 28% 13% 5%	463
	11th to 20th	Day	16% 7% 18% 31% 19% 9%	487
	21st to end	Day	16% 4 16% 28% 21% 14%	529
June	1st to 10th	Day	11% 4 17% 31% 23% 13%	490
	11th to 20th	Day	10% 4 18% 24% 25% 19%	490
	21st to end	Day	11% 4 15% 28% 27% 15%	490
July	1st to 10th	Day	9% 2 10% 23% 31% 26%	485
	11th to 20th	Day	8% 2 7% 25% 33% 24%	484
	21st to end	Day	7% 2 9% 28% 32% 23%	532
August	1st to 10th	Day	19% 2 13% 23% 24% 18%	486
	11th to 20th	Day	12% 2 12% 27% 30% 18%	479
	21st to end	Day	12% 2 11% 21% 29% 24%	539
September	1st to 10th	Day	10% 3 13% 23% 32% 18%	490
	11th to 20th	Day	19% 3 12% 18% 30% 18%	490
	21st to end	Day	22% 4 16% 26% 23% 8%	490
October	1st to 10th	Day	19% 5% 14% 27% 23% 12%	490
	11th to 20th	Day	14% 9% 20% 30% 22% 5%	490
	21st to end	Day	19% 6% 18% 33% 19% 4	539
November	1st to 10th	Day	22% 8% 23% 28% 15% 4	455
	11th to 20th	Day	18% 13% 34% 26% 8% 2	300
	21st to end	Day	13% 13% 32% 27% 13% 3	300
December	1st to 10th	Day	24% 16% 30% 25% 5%	300
	11th to 20th	Day	22% 12% 33% 24% 8% 1	300
	21st to end	Day	27% 11% 31% 21% 8% 1	330
January	1st to 10th	Night	20% 11% 33% 29% 7%	785
	11th to 20th	Night	20% 8% 35% 32% 5%	760
	21st to end	Night	19% 9% 37% 31% 3	836
February	1st to 10th	Night	17% 8% 34% 37% 4	760
	11th to 20th	Night	21% 11% 40% 26% 2	743
	21st to end	Night	17% 12% 39% 29% 3	628
March	1st to 10th	Night	18% 9% 31% 35% 6%	760
	11th to 20th	Night	19% 11% 31% 31% 7% 1	760
	21st to end	Night	19% 8% 33% 32% 8%	836
April	1st to 10th	Night	16% 11% 33% 29% 11%	760
	11th to 20th	Night	16% 11% 25% 31% 15% 1	710
	21st to end	Night	15% 5% 23% 37% 19% 1	570
May	1st to 10th	Night	14% 4 26% 35% 20% 1	570
	11th to 20th	Night	17% 5% 18% 33% 25% 2	561
	21st to end	Night	15% 2 9% 32% 36% 6%	617
June	1st to 10th	Night	11% 2 11% 35% 36% 5%	570
	11th to 20th	Night	12% 2 11% 31% 31% 14%	570
	21st to end	Night	9% 2 9% 28% 44% 8%	570
July	1st to 10th	Night	11% 2 8% 21% 49% 10%	555
	11th to 20th	Night	10% 2 4 24% 47% 13%	552
	21st to end	Night	8% 2 6% 30% 43% 11%	624
August	1st to 10th	Night	15% 2 8% 26% 39% 10%	567
	11th to 20th	Night	14% 2 6% 27% 40% 10%	564
	21st to end	Night	13% 2 6% 24% 46% 9%	710
September	1st to 10th	Night	13% 2 8% 27% 42% 8%	760
	11th to 20th	Night	18% 4 9% 26% 37% 6%	760
	21st to end	Night	21% 3 14% 32% 28% 3	760
October	1st to 10th	Night	18% 3 16% 28% 28% 6%	760
	11th to 20th	Night	17% 5% 23% 33% 21% 2	760
	21st to end	Night	15% 5% 21% 38% 18% 2	836
November	1st to 10th	Night	17% 5% 19% 38% 17% 3	780
	11th to 20th	Night	16% 7% 27% 37% 12% 1	800
	21st to end	Night	17% 8% 25% 36% 14% 1	800
December	1st to 10th	Night	22% 9% 27% 35% 8%	800
	11th to 20th	Night	19% 5% 29% 37% 9% 1	800
	21st to end	Night	25% 7% 27% 32% 8%	880

Page generated at 2025-01-04 03:24:00. Version ac07

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