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 2026-05-02.

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% 5% 2 6% 4 4 5% 4 6% 8% 44%	131972
	Night	15% 6% 2 5% 4 4 4 4 5% 7% 45%	130531
Transparency	Day	24% 38% 8% 13% 12% 5%	135657
	Night	24% 37% 7% 13% 14% 5%	134903
Seeing	Day	17% 9% 22% 25% 18% 9%	17082
	Night	17% 6% 22% 32% 20% 3	27210

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	15% 5% 2 4 3 2 3 2 3 5% 54%	5258
	11th to 20th	Day	10% 5% 1 4 3 3 2 2 3 3 65%	5280
	21st to end	Day	19% 7% 2 7% 3 3 3 3 4 5% 44%	5780
February	1st to 10th	Day	14% 7% 2 5% 4 3 4 3 5% 7% 46%	1949
	11th to 20th	Day	20% 6% 2 5% 3 3 3 3 4 5% 45%	2048
	21st to end	Day	18% 6% 2 6% 4 3 4 3 5% 5% 43%	1730
March	1st to 10th	Day	20% 6% 2 6% 4 3 3 3 5% 5% 43%	5013
	11th to 20th	Day	11% 5% 2 5% 4 3 4 2 4 6% 54%	5090
	21st to end	Day	18% 6% 2 4 3 3 3 3 4 7% 47%	5586
April	1st to 10th	Day	13% 4 1 4 4 4 4 3 6% 8% 48%	2310
	11th to 20th	Day	13% 4 2 4 4 4 4 4 6% 6% 49%	2481
	21st to end	Day	13% 5% 1 5% 3 5% 4 4 6% 7% 48%	2730
May	1st to 10th	Day	10% 7% 2 7% 5% 6% 6% 5% 7% 10% 35%	5875
	11th to 20th	Day	19% 7% 3 7% 5% 5% 5% 5% 7% 8% 30%	5861
	21st to end	Day	12% 5% 2 6% 4 5% 5% 5% 7% 9% 41%	6433
June	1st to 10th	Day	10% 5% 3 7% 5% 6% 6% 6% 8% 11% 35%	2600
	11th to 20th	Day	7% 4 2 6% 5% 4 6% 6% 9% 11% 39%	2600
	21st to end	Day	8% 4 2 5% 5% 5% 6% 6% 9% 9% 40%	2600
July	1st to 10th	Day	6% 4 2 8% 5% 7% 7% 5% 8% 10% 38%	5900
	11th to 20th	Day	6% 5% 2 7% 6% 7% 7% 6% 9% 13% 33%	5900
	21st to end	Day	8% 6% 3 9% 7% 7% 8% 6% 10% 10% 26%	6424
August	1st to 10th	Day	17% 7% 3 7% 5% 6% 6% 5% 7% 9% 28%	4234
	11th to 20th	Day	8% 5% 2 6% 5% 6% 6% 6% 9% 12% 35%	4174
	21st to end	Day	7% 4 1 5% 4 4 4 4 6% 9% 52%	4334
September	1st to 10th	Day	10% 4 2 7% 5% 5% 5% 4 6% 9% 43%	2200
	11th to 20th	Day	16% 6% 2 6% 5% 3 4 4 6% 7% 41%	2200
	21st to end	Day	18% 5% 2 6% 3 4 4 4 5% 7% 41%	2200
October	1st to 10th	Day	15% 4 1 5% 3 3 3 2 4 6% 55%	2139
	11th to 20th	Day	13% 4 2 4 2 2 3 2 4 4 61%	2000
	21st to end	Day	15% 5% 2 3 3 2 3 2 3 4 58%	2200
November	1st to 10th	Day	13% 5% 2 4 2 2 3 3 3 5% 57%	2015
	11th to 20th	Day	14% 4 1 3 3 3 3 3 5% 6% 55%	1890
	21st to end	Day	15% 4 1 4 3 3 3 2 5% 6% 53%	1890
December	1st to 10th	Day	15% 5% 2 4 3 3 3 3 4 5% 52%	3020
	11th to 20th	Day	18% 5% 2 4 3 3 4 4 6% 6% 45%	3463
	21st to end	Day	23% 4 1 3 2 2 3 2 4 6% 48%	4565
January	1st to 10th	Night	15% 5% 1 3 2 2 3 3 4 4 58%	7635
	11th to 20th	Night	11% 5% 2 4 3 3 3 2 4 4 59%	7680
	21st to end	Night	18% 7% 2 5% 3 3 3 3 4 6% 46%	8401
February	1st to 10th	Night	15% 6% 2 5% 3 3 3 4 5% 5% 49%	2667
	11th to 20th	Night	20% 6% 2 4 3 3 3 3 4 4 45%	2458
	21st to end	Night	16% 6% 2 6% 4 3 4 4 5% 6% 44%	2076
March	1st to 10th	Night	19% 6% 2 5% 3 3 4 3 4 6% 45%	5058
	11th to 20th	Night	10% 5% 1 4 3 3 4 3 5% 8% 55%	5090
	21st to end	Night	17% 4 2 5% 4 4 4 3 5% 6% 46%	5588
April	1st to 10th	Night	13% 5% 1 5% 3 3 4 4 5% 7% 48%	2310
	11th to 20th	Night	13% 4 2 5% 3 2 3 3 6% 7% 51%	2104
	21st to end	Night	12% 5% 2 5% 5% 3 5% 4 5% 6% 50%	1890
May	1st to 10th	Night	13% 6% 2 7% 5% 5% 5% 4 6% 9% 37%	4042
	11th to 20th	Night	21% 6% 2 7% 5% 4 5% 4 6% 8% 32%	4032
	21st to end	Night	14% 6% 2 7% 4 4 5% 3 6% 9% 41%	4421
June	1st to 10th	Night	10% 5% 3 6% 6% 5% 7% 6% 9% 11% 32%	1800
	11th to 20th	Night	11% 5% 2 6% 5% 5% 5% 5% 7% 11% 38%	1800
	21st to end	Night	9% 4 2 7% 5% 6% 6% 5% 8% 10% 38%	1800
July	1st to 10th	Night	8% 6% 3 9% 6% 7% 8% 6% 8% 10% 29%	4058
	11th to 20th	Night	8% 6% 3 8% 6% 6% 7% 6% 9% 13% 27%	4057
	21st to end	Night	11% 9% 4 10% 6% 6% 7% 5% 9% 10% 23%	4427
August	1st to 10th	Night	15% 9% 4 8% 6% 5% 5% 5% 8% 10% 26%	2915
	11th to 20th	Night	13% 7% 3 7% 6% 6% 7% 5% 7% 10% 29%	2875
	21st to end	Night	7% 6% 2 7% 4 6% 6% 4 6% 9% 43%	3524
September	1st to 10th	Night	12% 6% 2 6% 4 5% 5% 5% 7% 8% 40%	2200
	11th to 20th	Night	17% 6% 3 8% 5% 4 5% 4 5% 7% 35%	2200
	21st to end	Night	19% 7% 2 5% 4 4 4 3 5% 6% 42%	2200
October	1st to 10th	Night	17% 4 2 5% 3 3 4 3 5% 6% 49%	2260
	11th to 20th	Night	14% 5% 2 4 3 2 3 2 5% 6% 54%	2400
	21st to end	Night	15% 4 1 4 2 3 3 3 4 4 58%	2640
November	1st to 10th	Night	15% 4 2 5% 3 3 3 3 4 5% 54%	2498
	11th to 20th	Night	14% 5% 2 4 3 2 4 3 4 5% 54%	2730
	21st to end	Night	15% 5% 1 4 3 3 3 3 5% 6% 51%	2730
December	1st to 10th	Night	15% 5% 2 4 2 3 3 2 4 5% 54%	4380
	11th to 20th	Night	20% 6% 2 5% 3 3 4 3 4 5% 45%	4952
	21st to end	Night	22% 4 2 4 3 3 3 3 4 6% 47%	6633

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	28% 20% 7% 16% 24% 6%	5259
	11th to 20th	Day	19% 21% 3 9% 33% 16%	5280
	21st to end	Day	35% 23% 3 15% 17% 8%	5780
February	1st to 10th	Day	15% 59% 3 11% 9% 2	1949
	11th to 20th	Day	19% 58% 4 8% 8% 2	2058
	21st to end	Day	18% 60% 3 4 11% 3	1730
March	1st to 10th	Day	35% 29% 5% 10% 11% 10%	5013
	11th to 20th	Day	20% 29% 3 10% 21% 17%	5090
	21st to end	Day	27% 29% 4 19% 16% 5%	5586
April	1st to 10th	Day	16% 60% 5% 7% 9% 2	2310
	11th to 20th	Day	15% 61% 3 10% 8% 2	2481
	21st to end	Day	15% 60% 6% 12% 7% 1	2730
May	1st to 10th	Day	31% 34% 12% 15% 8% 1	5910
	11th to 20th	Day	37% 32% 10% 13% 7% 1	5865
	21st to end	Day	27% 33% 10% 14% 13% 3	6447
June	1st to 10th	Day	16% 64% 7% 8% 4 1	2600
	11th to 20th	Day	11% 65% 9% 9% 5%	2600
	21st to end	Day	14% 64% 9% 9% 4	2600
July	1st to 10th	Day	27% 33% 13% 19% 7%	5835
	11th to 20th	Day	28% 33% 25% 13% 1	5831
	21st to end	Day	38% 33% 11% 14% 4 1	6240
August	1st to 10th	Day	35% 39% 11% 13% 2	4221
	11th to 20th	Day	20% 42% 17% 11% 8% 2	4213
	21st to end	Day	13% 38% 9% 23% 16% 1	4334
September	1st to 10th	Day	14% 60% 6% 9% 9% 1	2200
	11th to 20th	Day	18% 59% 6% 9% 7% 1	2200
	21st to end	Day	20% 58% 7% 9% 5%	2200
October	1st to 10th	Day	16% 37% 5% 13% 22% 7%	3477
	11th to 20th	Day	9% 35% 3 11% 21% 21%	3240
	21st to end	Day	19% 35% 2 17% 14% 13%	3538
November	1st to 10th	Day	19% 53% 3 10% 11% 4	2015
	11th to 20th	Day	15% 54% 3 11% 13% 4	1890
	21st to end	Day	14% 54% 5% 11% 12% 3	1890
December	1st to 10th	Day	21% 35% 4 13% 20% 7%	3020
	11th to 20th	Day	28% 32% 7% 10% 17% 6%	3460
	21st to end	Day	29% 27% 6% 23% 13% 2	4565
January	1st to 10th	Night	24% 20% 8% 19% 23% 6%	7636
	11th to 20th	Night	21% 21% 3 11% 32% 10%	7680
	21st to end	Night	31% 23% 5% 14% 18% 9%	8401
February	1st to 10th	Night	15% 59% 4 10% 9% 2	2667
	11th to 20th	Night	20% 58% 4 7% 8% 2	2459
	21st to end	Night	17% 59% 4 7% 9% 3	2076
March	1st to 10th	Night	31% 31% 5% 9% 19% 5%	5058
	11th to 20th	Night	16% 29% 4 11% 24% 16%	5090
	21st to end	Night	27% 29% 5% 17% 15% 7%	5588
April	1st to 10th	Night	15% 60% 5% 8% 9% 2	2310
	11th to 20th	Night	14% 61% 4 11% 8% 3	2104
	21st to end	Night	15% 60% 5% 11% 8% 1	1890
May	1st to 10th	Night	31% 33% 10% 18% 7% 1	4069
	11th to 20th	Night	36% 33% 11% 13% 8%	4033
	21st to end	Night	27% 32% 9% 20% 10% 2	4429
June	1st to 10th	Night	16% 65% 7% 7% 4 1	1800
	11th to 20th	Night	14% 66% 9% 7% 4	1800
	21st to end	Night	14% 63% 9% 7% 6%	1800
July	1st to 10th	Night	35% 32% 14% 15% 5%	4015
	11th to 20th	Night	34% 34% 20% 10% 1	4006
	21st to end	Night	42% 31% 12% 11% 3	4297
August	1st to 10th	Night	37% 40% 13% 9% 1	2904
	11th to 20th	Night	30% 42% 13% 9% 5%	2902
	21st to end	Night	19% 39% 8% 23% 11% 1	3524
September	1st to 10th	Night	15% 60% 8% 8% 8% 1	2200
	11th to 20th	Night	20% 60% 7% 7% 6% 1	2200
	21st to end	Night	21% 59% 7% 8% 4	2200
October	1st to 10th	Night	21% 38% 5% 11% 18% 6%	3689
	11th to 20th	Night	10% 36% 3 12% 22% 18%	3899
	21st to end	Night	20% 35% 2 13% 18% 12%	4252
November	1st to 10th	Night	20% 54% 3 10% 10% 4	2498
	11th to 20th	Night	15% 54% 4 8% 13% 6%	2730
	21st to end	Night	15% 55% 3 12% 13% 2	2730
December	1st to 10th	Night	21% 34% 3 15% 20% 6%	4380
	11th to 20th	Night	31% 32% 5% 11% 14% 6%	4954
	21st to end	Night	29% 27% 8% 19% 15% 1	6633

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% 36% 18% 6%	330
	11th to 20th	Day	26% 22% 28% 18% 5%	330
	21st to end	Day	21% 20% 38% 17% 4	363
February	1st to 10th	Day	18% 18% 38% 20% 6% 1	330
	11th to 20th	Day	37% 20% 29% 13% 1	330
	21st to end	Day	29% 22% 31% 13% 4	273
March	1st to 10th	Day	22% 15% 29% 25% 9% 1	521
	11th to 20th	Day	22% 14% 32% 25% 6% 1	540
	21st to end	Day	21% 16% 32% 23% 7% 1	594
April	1st to 10th	Day	20% 15% 29% 23% 12% 2	540
	11th to 20th	Day	15% 16% 28% 23% 16% 3	532
	21st to end	Day	18% 9% 27% 26% 14% 6%	540
May	1st to 10th	Day	15% 11% 30% 27% 13% 5%	507
	11th to 20th	Day	18% 7% 18% 30% 19% 8%	527
	21st to end	Day	18% 6% 17% 27% 20% 13%	573
June	1st to 10th	Day	11% 5% 19% 30% 22% 12%	530
	11th to 20th	Day	10% 5% 19% 24% 24% 18%	530
	21st to end	Day	10% 3 14% 27% 29% 16%	530
July	1st to 10th	Day	9% 2 10% 25% 30% 25%	525
	11th to 20th	Day	7% 2 6% 25% 33% 26%	524
	21st to end	Day	7% 2 8% 26% 32% 24%	576
August	1st to 10th	Day	21% 2 13% 23% 23% 17%	526
	11th to 20th	Day	12% 2 11% 25% 30% 18%	519
	21st to end	Day	13% 3 12% 22% 29% 23%	583
September	1st to 10th	Day	10% 3 13% 25% 31% 17%	530
	11th to 20th	Day	18% 3 12% 18% 31% 18%	530
	21st to end	Day	22% 5% 17% 26% 23% 8%	530
October	1st to 10th	Day	18% 4 15% 29% 23% 11%	530
	11th to 20th	Day	14% 9% 20% 30% 22% 5%	530
	21st to end	Day	20% 7% 20% 31% 18% 4	583
November	1st to 10th	Day	21% 8% 24% 29% 14% 4	493
	11th to 20th	Day	17% 14% 33% 27% 8% 2	330
	21st to end	Day	14% 14% 31% 27% 12% 2	330
December	1st to 10th	Day	25% 16% 31% 24% 5%	330
	11th to 20th	Day	22% 12% 33% 24% 8% 1	330
	21st to end	Day	27% 12% 31% 21% 8% 1	363
January	1st to 10th	Night	20% 10% 34% 29% 6%	840
	11th to 20th	Night	19% 10% 35% 31% 5%	840
	21st to end	Night	18% 9% 38% 31% 3	924
February	1st to 10th	Night	17% 9% 34% 37% 3	840
	11th to 20th	Night	22% 12% 39% 25% 2	823
	21st to end	Night	17% 12% 39% 29% 3	692
March	1st to 10th	Night	18% 9% 31% 35% 6%	840
	11th to 20th	Night	18% 12% 31% 32% 7% 1	840
	21st to end	Night	18% 8% 34% 32% 7%	924
April	1st to 10th	Night	15% 11% 32% 30% 11%	840
	11th to 20th	Night	15% 11% 26% 32% 14% 1	786
	21st to end	Night	15% 5% 23% 37% 19% 1	630
May	1st to 10th	Night	14% 4 26% 35% 19% 1	603
	11th to 20th	Night	17% 5% 18% 32% 25% 2	591
	21st to end	Night	16% 3 10% 32% 34% 5%	650
June	1st to 10th	Night	11% 2 11% 36% 36% 5%	600
	11th to 20th	Night	12% 2 12% 31% 31% 13%	600
	21st to end	Night	9% 2 9% 27% 45% 8%	600
July	1st to 10th	Night	11% 2 8% 22% 48% 9%	585
	11th to 20th	Night	10% 2 4 23% 47% 14%	582
	21st to end	Night	8% 2 6% 29% 44% 11%	657
August	1st to 10th	Night	16% 3 8% 26% 37% 10%	597
	11th to 20th	Night	16% 2 6% 26% 40% 10%	594
	21st to end	Night	13% 2 7% 25% 45% 9%	748
September	1st to 10th	Night	13% 2 8% 29% 41% 8%	800
	11th to 20th	Night	17% 4 9% 26% 38% 6%	800
	21st to end	Night	21% 3 13% 33% 28% 2	800
October	1st to 10th	Night	18% 3 16% 29% 28% 6%	800
	11th to 20th	Night	16% 5% 23% 34% 21% 2	800
	21st to end	Night	16% 6% 22% 37% 18% 2	880
November	1st to 10th	Night	17% 6% 20% 39% 17% 3	820
	11th to 20th	Night	16% 8% 27% 37% 11% 1	840
	21st to end	Night	17% 8% 26% 35% 13% 1	840
December	1st to 10th	Night	23% 8% 27% 35% 8%	840
	11th to 20th	Night	19% 5% 29% 38% 8% 1	840
	21st to end	Night	25% 7% 27% 33% 7%	924

Page generated at 2026-04-29 02:21:44. Version ac07

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