Lynch Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lynch Park clear sky chart from 2005-11-06 to 2025-12-18.

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	17% 8% 2 6% 4 4 4 4 5% 7% 39%	126842
	Night	17% 8% 2 6% 4 4 4 3 5% 6% 39%	124192
Transparency	Day	27% 39% 8% 14% 10% 2	130375
	Night	28% 39% 7% 14% 11% 2	128746
Seeing	Day	18% 7% 24% 32% 16% 3	16473
	Night	20% 8% 29% 29% 12% 1	25356

By Month

Percentage Cloud Cover NE (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	12% 7% 3 7% 5% 4 4 4 6% 7% 42%	3597
	11th to 20th	Day	14% 8% 3 6% 3 2 3 3 5% 5% 48%	3570
	21st to end	Day	16% 9% 3 6% 4 3 3 3 4 5% 44%	3960
February	1st to 10th	Day	19% 8% 3 5% 4 5% 4 5% 5% 7% 36%	1861
	11th to 20th	Day	14% 8% 2 6% 4 4 4 4 6% 7% 40%	1948
	21st to end	Day	16% 9% 2 7% 5% 4 4 4 6% 6% 37%	1650
March	1st to 10th	Day	21% 10% 2 6% 4 3 4 3 5% 5% 35%	4476
	11th to 20th	Day	16% 10% 3 7% 4 3 4 4 6% 6% 37%	4830
	21st to end	Day	27% 8% 2 5% 4 4 4 4 6% 6% 31%	5693
April	1st to 10th	Day	20% 8% 2 5% 5% 4 4 3 4 6% 38%	2400
	11th to 20th	Day	18% 6% 2 5% 5% 4 4 4 6% 7% 39%	2414
	21st to end	Day	19% 5% 2 6% 4 4 5% 4 6% 6% 39%	2600
May	1st to 10th	Day	27% 11% 3 7% 4 3 4 3 5% 7% 25%	5886
	11th to 20th	Day	17% 10% 3 8% 5% 4 5% 4 5% 6% 32%	5897
	21st to end	Day	18% 7% 3 6% 4 4 4 3 5% 7% 37%	6949
June	1st to 10th	Day	19% 7% 2 5% 5% 5% 5% 3 7% 8% 35%	2800
	11th to 20th	Day	15% 7% 2 6% 4 4 4 5% 6% 9% 39%	2800
	21st to end	Day	16% 6% 2 6% 4 4 5% 5% 6% 9% 38%	2800
July	1st to 10th	Day	15% 8% 3 6% 5% 5% 5% 4 7% 10% 34%	6360
	11th to 20th	Day	7% 7% 2 6% 5% 5% 6% 5% 8% 11% 38%	6360
	21st to end	Day	13% 6% 2 6% 4 3 4 3 5% 8% 45%	6926
August	1st to 10th	Day	14% 6% 3 6% 5% 5% 5% 4 7% 9% 35%	4240
	11th to 20th	Day	13% 7% 3 7% 4 4 4 4 6% 8% 39%	4175
	21st to end	Day	7% 3 2 5% 4 4 5% 5% 7% 10% 47%	4322
September	1st to 10th	Day	13% 5% 1 5% 3 3 4 5% 5% 7% 48%	2375
	11th to 20th	Day	14% 6% 2 4 4 3 2 3 4 6% 53%	2200
	21st to end	Day	16% 6% 2 6% 4 3 4 3 5% 7% 44%	2200
October	1st to 10th	Day	21% 5% 2 6% 3 3 3 3 4 5% 44%	2200
	11th to 20th	Day	16% 6% 2 5% 4 3 4 3 5% 7% 45%	1958
	21st to end	Day	19% 7% 2 5% 4 3 3 4 5% 6% 41%	1980
November	1st to 10th	Day	15% 7% 3 5% 3 4 3 3 4 5% 48%	1851
	11th to 20th	Day	17% 7% 2 4 3 3 3 3 4 6% 47%	1890
	21st to end	Day	18% 7% 2 5% 3 4 3 3 5% 6% 43%	1890
December	1st to 10th	Day	15% 9% 2 5% 3 3 3 2 4 6% 48%	2782
	11th to 20th	Day	20% 7% 1 4 2 3 3 3 4 6% 47%	3042
	21st to end	Day	20% 10% 2 6% 4 4 4 3 5% 5% 37%	3960
January	1st to 10th	Night	14% 6% 2 4 4 3 4 3 4 6% 49%	6349
	11th to 20th	Night	14% 10% 3 8% 5% 5% 4 3 4 6% 39%	6315
	21st to end	Night	16% 10% 3 7% 5% 5% 4 3 5% 5% 38%	6996
February	1st to 10th	Night	17% 10% 3 6% 5% 4 4 3 6% 6% 37%	2535
	11th to 20th	Night	15% 9% 3 6% 4 4 4 3 5% 6% 41%	2338
	21st to end	Night	18% 9% 3 6% 4 3 3 3 4 6% 42%	1980
March	1st to 10th	Night	26% 8% 2 5% 4 3 3 3 4 5% 36%	5364
	11th to 20th	Night	15% 12% 3 7% 4 4 4 3 5% 5% 37%	5128
	21st to end	Night	26% 9% 3 6% 4 4 4 4 5% 4 32%	5224
April	1st to 10th	Night	19% 9% 2 7% 4 4 5% 4 5% 6% 35%	2000
	11th to 20th	Night	20% 8% 2 6% 5% 3 4 3 5% 5% 39%	1933
	21st to end	Night	19% 7% 3 7% 4 5% 4 3 5% 5% 38%	1800
May	1st to 10th	Night	29% 12% 3 7% 4 4 4 3 4 5% 26%	4054
	11th to 20th	Night	17% 10% 3 8% 5% 5% 6% 5% 7% 8% 28%	4033
	21st to end	Night	20% 8% 3 8% 5% 5% 4 4 5% 5% 32%	3930
June	1st to 10th	Night	18% 9% 2 7% 5% 4 4 3 4 6% 37%	1600
	11th to 20th	Night	18% 7% 2 6% 3 4 4 3 6% 10% 36%	1600
	21st to end	Night	16% 6% 2 7% 4 4 4 4 7% 8% 38%	1600
July	1st to 10th	Night	11% 7% 3 7% 5% 5% 5% 4 6% 10% 37%	3600
	11th to 20th	Night	10% 7% 3 7% 5% 5% 5% 5% 7% 9% 38%	3600
	21st to end	Night	11% 7% 2 6% 5% 4 4 3 5% 7% 44%	3926
August	1st to 10th	Night	18% 7% 3 8% 5% 5% 5% 4 6% 8% 32%	2876
	11th to 20th	Night	9% 8% 3 7% 6% 6% 6% 5% 7% 8% 35%	2872
	21st to end	Night	8% 5% 2 4 4 4 4 3 5% 9% 51%	3573
September	1st to 10th	Night	12% 5% 2 6% 4 4 3 4 5% 7% 47%	2025
	11th to 20th	Night	13% 6% 1 5% 3 3 3 3 4 5% 54%	2200
	21st to end	Night	17% 6% 2 6% 3 4 4 3 5% 7% 43%	2200
October	1st to 10th	Night	19% 6% 2 6% 4 4 3 3 4 5% 44%	2200
	11th to 20th	Night	16% 6% 2 5% 4 4 4 4 5% 7% 46%	2438
	21st to end	Night	21% 7% 2 6% 4 3 4 3 5% 6% 40%	2860
November	1st to 10th	Night	15% 5% 2 5% 4 3 3 3 5% 6% 48%	2667
	11th to 20th	Night	16% 7% 2 5% 4 3 3 4 4 5% 47%	2730
	21st to end	Night	16% 7% 3 4 4 4 4 3 4 6% 44%	2730
December	1st to 10th	Night	18% 8% 2 5% 4 4 3 3 4 5% 43%	4613
	11th to 20th	Night	21% 8% 2 6% 3 3 3 3 4 5% 42%	5307
	21st to end	Night	18% 10% 2 6% 4 3 3 3 5% 6% 40%	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	29% 28% 7% 20% 15% 1	3598
	11th to 20th	Day	25% 28% 9% 19% 17% 3	3600
	21st to end	Day	31% 31% 7% 14% 15% 2	3960
February	1st to 10th	Day	18% 63% 6% 7% 5% 1	1861
	11th to 20th	Day	18% 61% 4 8% 8% 1	1957
	21st to end	Day	14% 63% 6% 9% 7% 1	1650
March	1st to 10th	Day	38% 30% 6% 9% 9% 9%	4479
	11th to 20th	Day	32% 32% 12% 17% 7% 1	4830
	21st to end	Day	42% 30% 6% 9% 8% 5%	5693
April	1st to 10th	Day	21% 62% 3 7% 6% 2	2400
	11th to 20th	Day	15% 63% 5% 8% 7% 2	2414
	21st to end	Day	18% 62% 4 8% 7% 1	2600
May	1st to 10th	Day	43% 34% 11% 9% 3	5897
	11th to 20th	Day	40% 32% 11% 12% 5% 1	5901
	21st to end	Day	35% 32% 9% 15% 9%	6949
June	1st to 10th	Day	15% 63% 5% 9% 7%	2800
	11th to 20th	Day	14% 62% 6% 8% 8% 1	2800
	21st to end	Day	15% 62% 6% 9% 8% 1	2800
July	1st to 10th	Day	35% 28% 10% 14% 11% 1	6290
	11th to 20th	Day	28% 29% 13% 19% 10%	6285
	21st to end	Day	28% 27% 10% 23% 12% 1	6728
August	1st to 10th	Day	29% 39% 11% 15% 4	4226
	11th to 20th	Day	29% 38% 9% 19% 5%	4214
	21st to end	Day	16% 39% 10% 23% 12% 1	4322
September	1st to 10th	Day	13% 58% 6% 13% 9%	2375
	11th to 20th	Day	16% 57% 5% 10% 11% 1	2200
	21st to end	Day	19% 57% 4 11% 8% 1	2200
October	1st to 10th	Day	25% 37% 6% 17% 13% 2	3590
	11th to 20th	Day	18% 36% 4 20% 19% 3	3161
	21st to end	Day	18% 36% 6% 24% 15% 1	3180
November	1st to 10th	Day	19% 54% 7% 11% 7% 1	1851
	11th to 20th	Day	17% 54% 5% 9% 13% 2	1890
	21st to end	Day	18% 54% 7% 12% 8% 1	1890
December	1st to 10th	Day	24% 35% 10% 23% 9%	2782
	11th to 20th	Day	27% 32% 10% 11% 15% 5%	3042
	21st to end	Day	37% 28% 6% 16% 9% 4	3960
January	1st to 10th	Night	25% 27% 7% 26% 12% 2	6349
	11th to 20th	Night	34% 27% 9% 16% 11% 3	6360
	21st to end	Night	37% 30% 6% 11% 13% 4	6996
February	1st to 10th	Night	18% 63% 5% 7% 5% 1	2535
	11th to 20th	Night	18% 61% 4 7% 9% 1	2340
	21st to end	Night	18% 61% 4 9% 7% 2	1980
March	1st to 10th	Night	39% 29% 6% 8% 11% 7%	5374
	11th to 20th	Night	34% 32% 11% 12% 10% 1	5129
	21st to end	Night	42% 30% 3 6% 14% 4	5224
April	1st to 10th	Night	22% 62% 3 6% 6% 2	2000
	11th to 20th	Night	17% 63% 4 8% 7% 1	1933
	21st to end	Night	19% 62% 4 7% 8% 1	1800
May	1st to 10th	Night	45% 32% 10% 8% 4 1	4060
	11th to 20th	Night	39% 34% 12% 10% 5%	4034
	21st to end	Night	41% 32% 8% 12% 7% 1	3931
June	1st to 10th	Night	16% 63% 4 9% 7%	1600
	11th to 20th	Night	15% 64% 5% 10% 6%	1600
	21st to end	Night	16% 61% 3 10% 8% 1	1600
July	1st to 10th	Night	32% 28% 9% 16% 15%	3560
	11th to 20th	Night	30% 29% 14% 14% 11% 1	3552
	21st to end	Night	29% 27% 9% 23% 11% 1	3809
August	1st to 10th	Night	35% 38% 8% 12% 7% 1	2866
	11th to 20th	Night	29% 40% 10% 15% 5%	2899
	21st to end	Night	16% 38% 11% 17% 17%	3573
September	1st to 10th	Night	14% 58% 5% 14% 8% 1	2025
	11th to 20th	Night	17% 57% 3 10% 12% 1	2200
	21st to end	Night	19% 58% 4 11% 8%	2200
October	1st to 10th	Night	25% 37% 9% 17% 10% 2	3590
	11th to 20th	Night	13% 36% 7% 19% 23% 2	3974
	21st to end	Night	19% 36% 7% 23% 13% 1	4610
November	1st to 10th	Night	19% 55% 4 13% 9% 1	2667
	11th to 20th	Night	17% 54% 5% 10% 13% 2	2730
	21st to end	Night	17% 55% 7% 13% 7% 1	2730
December	1st to 10th	Night	29% 35% 6% 21% 9%	4613
	11th to 20th	Night	32% 32% 9% 10% 16% 1	5307
	21st to end	Night	34% 28% 10% 15% 12% 1	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	24% 13% 31% 27% 6% 1	200
	11th to 20th	Day	17% 18% 34% 25% 7%	200
	21st to end	Day	21% 9% 38% 23% 9%	220
February	1st to 10th	Day	24% 13% 36% 24% 3	416
	11th to 20th	Day	22% 11% 43% 21% 2	496
	21st to end	Day	17% 11% 35% 29% 7% 1	414
March	1st to 10th	Day	21% 12% 33% 27% 7%	500
	11th to 20th	Day	17% 9% 35% 33% 5%	500
	21st to end	Day	24% 9% 33% 25% 7% 2	550
April	1st to 10th	Day	24% 10% 31% 23% 9% 1	500
	11th to 20th	Day	21% 6% 29% 34% 9%	492
	21st to end	Day	21% 6% 24% 38% 10% 1	500
May	1st to 10th	Day	26% 5% 26% 31% 10% 1	503
	11th to 20th	Day	15% 5% 24% 39% 14% 3	527
	21st to end	Day	17% 3 16% 40% 20% 3	573
June	1st to 10th	Day	18% 4 16% 37% 22% 3	530
	11th to 20th	Day	14% 4 18% 43% 18% 3	530
	21st to end	Day	15% 5% 16% 39% 22% 4	530
July	1st to 10th	Day	17% 2 12% 36% 28% 6%	525
	11th to 20th	Day	10% 3 14% 38% 29% 6%	524
	21st to end	Day	11% 2 11% 43% 30% 2	576
August	1st to 10th	Day	10% 3 13% 37% 32% 5%	526
	11th to 20th	Day	12% 3 12% 37% 29% 8%	519
	21st to end	Day	12% 3 13% 39% 26% 8%	583
September	1st to 10th	Day	15% 3 19% 31% 24% 8%	530
	11th to 20th	Day	17% 3 17% 32% 22% 9%	530
	21st to end	Day	19% 3 21% 34% 17% 6%	530
October	1st to 10th	Day	22% 3 21% 29% 21% 4	530
	11th to 20th	Day	18% 7% 27% 29% 18% 3	455
	21st to end	Day	25% 6% 28% 29% 11% 1	462
November	1st to 10th	Day	16% 11% 29% 30% 13% 2	425
	11th to 20th	Day	21% 13% 34% 25% 7%	430
	21st to end	Day	23% 14% 29% 24% 9% 1	430
December	1st to 10th	Day	20% 9% 39% 25% 6%	283
	11th to 20th	Day	21% 13% 40% 23% 3	214
	21st to end	Day	23% 11% 32% 26% 5% 2	220
January	1st to 10th	Night	21% 15% 40% 20% 4	800
	11th to 20th	Night	25% 15% 37% 19% 4	800
	21st to end	Night	18% 16% 40% 22% 4	880
February	1st to 10th	Night	22% 14% 38% 24% 2	800
	11th to 20th	Night	21% 13% 47% 16% 3	783
	21st to end	Night	21% 13% 39% 22% 6%	660
March	1st to 10th	Night	23% 12% 37% 24% 4	800
	11th to 20th	Night	20% 9% 39% 24% 7% 1	800
	21st to end	Night	23% 8% 35% 25% 8%	880
April	1st to 10th	Night	24% 8% 32% 29% 7%	800
	11th to 20th	Night	20% 6% 32% 32% 9%	749
	21st to end	Night	22% 5% 28% 35% 10% 1	600
May	1st to 10th	Night	25% 5% 26% 31% 11% 2	600
	11th to 20th	Night	22% 2 25% 37% 13% 2	592
	21st to end	Night	21% 4 16% 41% 17% 1	437
June	1st to 10th	Night	21% 3 17% 39% 17% 3	400
	11th to 20th	Night	18% 3 20% 40% 18% 2	400
	21st to end	Night	19% 2 15% 46% 17% 2	400
July	1st to 10th	Night	13% 3 12% 43% 25% 3	390
	11th to 20th	Night	12% 3 10% 46% 26% 3	388
	21st to end	Night	14% 3 11% 44% 27% 1	438
August	1st to 10th	Night	10% 3 12% 46% 28% 2	571
	11th to 20th	Night	12% 2 13% 43% 27% 3	592
	21st to end	Night	13% 3 15% 34% 29% 5%	867
September	1st to 10th	Night	13% 3 17% 38% 26% 3	800
	11th to 20th	Night	15% 4 19% 31% 24% 7%	800
	21st to end	Night	19% 2 19% 34% 22% 4	800
October	1st to 10th	Night	22% 5% 22% 30% 18% 4	800
	11th to 20th	Night	18% 6% 29% 31% 14% 2	800
	21st to end	Night	24% 9% 31% 27% 9% 1	880
November	1st to 10th	Night	17% 9% 32% 30% 10% 1	820
	11th to 20th	Night	20% 13% 36% 23% 7% 1	840
	21st to end	Night	19% 17% 34% 24% 5% 1	840
December	1st to 10th	Night	24% 13% 39% 19% 5%	840
	11th to 20th	Night	23% 16% 38% 20% 4	829
	21st to end	Night	23% 14% 38% 22% 3	880

Page generated at 2025-12-15 01:13:50. Version ac07

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