Lynchburg College Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lynchburg College Observatory clear sky chart from 2005-11-06 to 2024-12-24.

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% 6% 2 6% 4 4 5% 4 6% 8% 41%	101029
	Night	15% 6% 2 5% 4 4 4 3 5% 7% 44%	99030
Transparency	Day	39% 4 12% 24% 17% 4	104678
	Night	39% 3 11% 24% 18% 5%	103520
Seeing	Day	20% 9% 23% 25% 16% 7%	15237
	Night	18% 7% 22% 33% 18% 2	25644

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 4 4 4 4 4 5% 7% 46%	2836
	11th to 20th	Day	15% 7% 2 6% 4 5% 4 3 5% 6% 42%	2840
	21st to end	Day	21% 7% 3 7% 4 4 4 3 4 4 40%	3124
February	1st to 10th	Day	12% 7% 2 7% 5% 5% 6% 4 5% 6% 40%	1710
	11th to 20th	Day	18% 6% 2 5% 5% 4 4 3 5% 7% 41%	1667
	21st to end	Day	20% 6% 3 7% 5% 4 4 3 4 6% 38%	1670
March	1st to 10th	Day	22% 8% 2 5% 3 3 4 3 6% 7% 37%	3435
	11th to 20th	Day	10% 5% 2 5% 3 4 5% 4 5% 6% 51%	3480
	21st to end	Day	18% 7% 3 7% 4 4 4 4 5% 6% 38%	3815
April	1st to 10th	Day	12% 5% 2 4 5% 4 4 3 6% 7% 49%	2186
	11th to 20th	Day	15% 5% 2 4 4 4 4 4 5% 7% 45%	2254
	21st to end	Day	16% 6% 2 6% 5% 4 4 4 5% 6% 42%	2369
May	1st to 10th	Day	16% 6% 3 6% 5% 6% 7% 5% 7% 8% 31%	4082
	11th to 20th	Day	20% 7% 2 6% 5% 4 4 4 6% 7% 33%	4081
	21st to end	Day	9% 4 2 5% 4 5% 5% 4 7% 10% 44%	4476
June	1st to 10th	Day	10% 5% 2 4 5% 5% 5% 5% 7% 10% 43%	2470
	11th to 20th	Day	10% 5% 2 6% 4 5% 5% 5% 8% 10% 41%	2470
	21st to end	Day	7% 5% 2 6% 4 5% 6% 5% 8% 11% 41%	2470
July	1st to 10th	Day	6% 4 2 6% 5% 5% 5% 6% 9% 11% 40%	4120
	11th to 20th	Day	8% 5% 2 6% 5% 6% 6% 5% 8% 11% 36%	4120
	21st to end	Day	13% 8% 3 9% 6% 7% 7% 5% 8% 9% 27%	4466
August	1st to 10th	Day	14% 7% 2 7% 5% 5% 5% 5% 7% 12% 30%	4104
	11th to 20th	Day	9% 4 2 6% 5% 5% 6% 6% 7% 11% 39%	4044
	21st to end	Day	8% 4 2 5% 4 4 4 4 6% 10% 49%	4180
September	1st to 10th	Day	12% 5% 2 5% 4 4 4 4 5% 7% 48%	2280
	11th to 20th	Day	16% 6% 2 6% 4 5% 4 3 6% 7% 42%	2103
	21st to end	Day	24% 6% 2 6% 4 4 4 3 5% 5% 37%	2076
October	1st to 10th	Day	17% 6% 1 4 3 3 3 2 5% 6% 51%	1900
	11th to 20th	Day	15% 5% 2 4 3 2 3 2 5% 6% 54%	1900
	21st to end	Day	13% 6% 2 4 3 3 3 3 4 6% 51%	2090
November	1st to 10th	Day	13% 4 1 4 4 3 3 3 4 6% 54%	1957
	11th to 20th	Day	14% 5% 1 4 4 3 3 3 5% 7% 51%	1875
	21st to end	Day	14% 4 2 5% 4 3 3 4 5% 8% 48%	1633
December	1st to 10th	Day	17% 7% 2 7% 4 4 5% 4 6% 7% 38%	1600
	11th to 20th	Day	17% 4 2 4 3 2 3 3 4 7% 51%	1995
	21st to end	Day	20% 6% 2 5% 4 4 4 4 7% 8% 35%	3151
January	1st to 10th	Night	14% 6% 2 5% 3 4 3 3 5% 6% 49%	4109
	11th to 20th	Night	16% 6% 2 5% 3 3 4 3 5% 6% 47%	4120
	21st to end	Night	23% 6% 2 6% 3 3 4 3 4 5% 41%	4532
February	1st to 10th	Night	14% 6% 3 6% 4 4 4 4 6% 6% 44%	2470
	11th to 20th	Night	20% 6% 2 6% 4 4 3 3 4 6% 42%	2397
	21st to end	Night	16% 7% 2 5% 5% 4 4 4 5% 7% 41%	1781
March	1st to 10th	Night	22% 8% 3 7% 4 4 4 3 5% 6% 34%	3418
	11th to 20th	Night	11% 3 2 4 3 4 4 4 5% 7% 53%	3480
	21st to end	Night	16% 6% 2 5% 4 3 3 3 5% 5% 48%	3817
April	1st to 10th	Night	15% 6% 2 5% 4 3 4 3 5% 7% 45%	1992
	11th to 20th	Night	14% 4 2 5% 3 4 4 4 5% 8% 49%	1875
	21st to end	Night	15% 5% 2 5% 4 3 5% 4 5% 7% 45%	1826
May	1st to 10th	Night	17% 8% 3 7% 5% 4 4 3 6% 8% 35%	2813
	11th to 20th	Night	24% 8% 3 5% 4 4 3 3 4 6% 36%	2812
	21st to end	Night	10% 4 2 5% 4 4 4 4 7% 10% 45%	3079
June	1st to 10th	Night	9% 5% 2 5% 4 4 4 4 8% 11% 44%	1710
	11th to 20th	Night	11% 4 2 6% 4 4 4 4 7% 10% 44%	1710
	21st to end	Night	8% 4 2 5% 4 5% 5% 5% 7% 11% 45%	1710
July	1st to 10th	Night	6% 5% 2 5% 5% 6% 5% 5% 8% 10% 42%	2840
	11th to 20th	Night	9% 5% 2 6% 5% 6% 5% 5% 8% 11% 38%	2840
	21st to end	Night	11% 8% 3 9% 7% 5% 5% 4 7% 9% 31%	3087
August	1st to 10th	Night	16% 7% 3 7% 4 5% 5% 4 7% 11% 32%	2825
	11th to 20th	Night	9% 6% 2 6% 4 6% 6% 5% 7% 9% 39%	2785
	21st to end	Night	8% 5% 2 6% 5% 4 5% 3 6% 9% 47%	3444
September	1st to 10th	Night	11% 6% 2 5% 4 5% 5% 4 6% 6% 47%	1900
	11th to 20th	Night	16% 5% 2 6% 5% 4 4 4 5% 6% 42%	2073
	21st to end	Night	23% 7% 3 6% 4 3 4 3 5% 5% 37%	2102
October	1st to 10th	Night	17% 5% 2 5% 4 3 3 3 4 6% 49%	2280
	11th to 20th	Night	14% 5% 1 5% 4 3 3 2 4 6% 52%	2280
	21st to end	Night	14% 3 2 4 3 2 3 3 4 6% 55%	2508
November	1st to 10th	Night	14% 6% 3 5% 3 3 4 2 4 5% 53%	2341
	11th to 20th	Night	14% 4 2 5% 3 3 4 3 4 5% 52%	2523
	21st to end	Night	13% 4 1 5% 4 4 4 3 5% 7% 50%	2762
December	1st to 10th	Night	18% 7% 2 5% 4 4 3 3 4 5% 44%	2800
	11th to 20th	Night	16% 7% 2 5% 4 4 3 3 5% 5% 46%	3411
	21st to end	Night	18% 6% 2 5% 4 4 5% 4 7% 8% 38%	4578

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	37% 2 7% 29% 18% 6%	2837
	11th to 20th	Day	43% 3 6% 20% 23% 5%	2840
	21st to end	Day	49% 2 6% 23% 17% 3	3124
February	1st to 10th	Day	42% 4 11% 24% 17% 3	1710
	11th to 20th	Day	44% 2 9% 23% 18% 4	1676
	21st to end	Day	48% 3 10% 17% 17% 5%	1670
March	1st to 10th	Day	47% 3 8% 21% 15% 5%	3435
	11th to 20th	Day	33% 3 8% 26% 20% 9%	3480
	21st to end	Day	47% 3 10% 21% 16% 3	3815
April	1st to 10th	Day	34% 3 11% 24% 19% 8%	2186
	11th to 20th	Day	38% 3 11% 23% 20% 5%	2254
	21st to end	Day	43% 4 11% 24% 14% 4	2369
May	1st to 10th	Day	48% 4 13% 20% 13% 2	4120
	11th to 20th	Day	50% 4 10% 24% 11% 1	4085
	21st to end	Day	34% 4 18% 23% 18% 3	4489
June	1st to 10th	Day	35% 6% 17% 27% 14% 1	2470
	11th to 20th	Day	36% 6% 17% 22% 17% 2	2470
	21st to end	Day	34% 8% 16% 26% 14% 2	2470
July	1st to 10th	Day	35% 8% 23% 19% 10% 5%	4055
	11th to 20th	Day	39% 5% 20% 26% 10% 1	4051
	21st to end	Day	51% 6% 13% 20% 9%	4324
August	1st to 10th	Day	46% 4 18% 25% 6%	4091
	11th to 20th	Day	37% 6% 15% 30% 12% 1	4083
	21st to end	Day	31% 4 21% 28% 15% 1	4180
September	1st to 10th	Day	35% 6% 14% 21% 21% 4	2280
	11th to 20th	Day	41% 4 8% 26% 18% 3	2103
	21st to end	Day	49% 3 8% 19% 18% 2	2076
October	1st to 10th	Day	34% 2 7% 21% 28% 8%	3160
	11th to 20th	Day	25% 1 8% 24% 29% 13%	3140
	21st to end	Day	23% 2 11% 29% 23% 11%	3428
November	1st to 10th	Day	33% 2 9% 23% 28% 5%	1957
	11th to 20th	Day	34% 3 8% 24% 23% 8%	1875
	21st to end	Day	34% 3 9% 26% 24% 4	1633
December	1st to 10th	Day	45% 3 11% 20% 17% 4	1600
	11th to 20th	Day	35% 2 9% 25% 21% 7%	1991
	21st to end	Day	46% 3 9% 27% 13% 2	3151
January	1st to 10th	Night	37% 2 7% 25% 24% 4	4109
	11th to 20th	Night	40% 3 7% 22% 24% 5%	4120
	21st to end	Night	47% 2 7% 25% 15% 5%	4532
February	1st to 10th	Night	39% 3 11% 25% 20% 2	2470
	11th to 20th	Night	44% 3 9% 20% 19% 6%	2399
	21st to end	Night	43% 3 9% 24% 15% 5%	1781
March	1st to 10th	Night	52% 3 7% 20% 16% 3	3418
	11th to 20th	Night	31% 3 7% 23% 28% 8%	3480
	21st to end	Night	39% 3 10% 24% 19% 5%	3817
April	1st to 10th	Night	39% 3 11% 20% 22% 5%	1992
	11th to 20th	Night	34% 4 12% 23% 21% 6%	1875
	21st to end	Night	38% 4 11% 25% 17% 4	1826
May	1st to 10th	Night	47% 4 14% 20% 12% 2	2840
	11th to 20th	Night	50% 4 9% 24% 12% 1	2813
	21st to end	Night	34% 4 18% 27% 13% 4	3087
June	1st to 10th	Night	33% 7% 16% 28% 16% 1	1710
	11th to 20th	Night	35% 6% 17% 23% 16% 2	1710
	21st to end	Night	31% 8% 17% 23% 17% 4	1710
July	1st to 10th	Night	35% 8% 21% 19% 13% 3	2795
	11th to 20th	Night	39% 5% 22% 24% 8% 1	2786
	21st to end	Night	49% 5% 14% 23% 9%	2988
August	1st to 10th	Night	47% 5% 18% 23% 7% 1	2814
	11th to 20th	Night	39% 4 16% 28% 12% 1	2812
	21st to end	Night	34% 5% 15% 34% 10% 2	3444
September	1st to 10th	Night	37% 5% 13% 20% 18% 6%	1900
	11th to 20th	Night	41% 5% 8% 24% 19% 3	2073
	21st to end	Night	50% 4 7% 20% 15% 3	2102
October	1st to 10th	Night	38% 2 8% 19% 26% 7%	3800
	11th to 20th	Night	26% 2 7% 23% 29% 13%	3779
	21st to end	Night	21% 2 7% 30% 28% 12%	4120
November	1st to 10th	Night	36% 2 8% 23% 25% 7%	2341
	11th to 20th	Night	35% 2 8% 23% 25% 7%	2523
	21st to end	Night	34% 3 9% 27% 22% 6%	2762
December	1st to 10th	Night	44% 2 8% 25% 17% 3	2800
	11th to 20th	Night	40% 2 8% 22% 21% 6%	3414
	21st to end	Night	44% 2 10% 23% 20% 2	4578

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	30% 21% 27% 18% 3 1	270
	11th to 20th	Day	36% 12% 36% 16% 1	270
	21st to end	Day	30% 19% 36% 12% 4	297
February	1st to 10th	Day	24% 16% 39% 16% 5%	270
	11th to 20th	Day	41% 16% 32% 8% 3	270
	21st to end	Day	30% 18% 31% 18% 3	325
March	1st to 10th	Day	27% 13% 33% 22% 5%	460
	11th to 20th	Day	23% 21% 29% 21% 5% 1	460
	21st to end	Day	24% 12% 34% 22% 7% 1	506
April	1st to 10th	Day	22% 19% 28% 21% 8% 2	460
	11th to 20th	Day	20% 13% 28% 22% 13% 4	452
	21st to end	Day	24% 9% 30% 21% 13% 3	460
May	1st to 10th	Day	21% 11% 32% 22% 10% 3	463
	11th to 20th	Day	22% 7% 22% 26% 17% 5%	487
	21st to end	Day	19% 2 19% 29% 21% 9%	529
June	1st to 10th	Day	12% 4 24% 33% 18% 9%	490
	11th to 20th	Day	12% 5% 17% 32% 21% 13%	490
	21st to end	Day	11% 4 20% 32% 23% 9%	490
July	1st to 10th	Day	12% 14% 28% 28% 16%	485
	11th to 20th	Day	6% 1 12% 35% 31% 15%	484
	21st to end	Day	12% 2 16% 30% 26% 13%	532
August	1st to 10th	Day	15% 4 16% 25% 24% 16%	486
	11th to 20th	Day	14% 1 15% 29% 24% 16%	479
	21st to end	Day	11% 1 9% 29% 26% 22%	539
September	1st to 10th	Day	13% 3 11% 26% 29% 18%	490
	11th to 20th	Day	19% 3 10% 26% 29% 13%	490
	21st to end	Day	29% 6% 17% 22% 19% 6%	490
October	1st to 10th	Day	23% 4 16% 30% 21% 6%	490
	11th to 20th	Day	16% 11% 20% 28% 19% 5%	490
	21st to end	Day	17% 9% 27% 30% 14% 3	539
November	1st to 10th	Day	18% 8% 27% 31% 13% 3	495
	11th to 20th	Day	20% 15% 26% 25% 12% 1	375
	21st to end	Day	21% 20% 26% 21% 10% 2	215
December	1st to 10th	Day	27% 14% 35% 18% 7%	200
	11th to 20th	Day	25% 11% 31% 26% 6% 1	203
	21st to end	Day	27% 13% 29% 20% 9% 1	306
January	1st to 10th	Night	21% 14% 32% 29% 3	760
	11th to 20th	Night	21% 14% 31% 33% 3	760
	21st to end	Night	21% 11% 37% 28% 3	836
February	1st to 10th	Night	18% 12% 36% 30% 4	760
	11th to 20th	Night	27% 13% 33% 25% 1	743
	21st to end	Night	21% 13% 34% 29% 3	628
March	1st to 10th	Night	18% 13% 30% 34% 5%	760
	11th to 20th	Night	23% 12% 31% 26% 7% 1	760
	21st to end	Night	19% 10% 31% 33% 6%	836
April	1st to 10th	Night	18% 16% 31% 28% 7%	760
	11th to 20th	Night	17% 11% 28% 31% 12% 1	751
	21st to end	Night	18% 5% 28% 38% 11%	686
May	1st to 10th	Night	17% 7% 25% 34% 16% 1	570
	11th to 20th	Night	20% 5% 16% 37% 19% 2	561
	21st to end	Night	18% 1 9% 33% 34% 5%	617
June	1st to 10th	Night	10% 1 12% 44% 30% 3	570
	11th to 20th	Night	12% 2 9% 35% 38% 4	570
	21st to end	Night	9% 2 10% 42% 32% 6%	570
July	1st to 10th	Night	10% 1 6% 33% 42% 6%	555
	11th to 20th	Night	7% 1 5% 31% 49% 8%	552
	21st to end	Night	10% 1 6% 41% 38% 4	624
August	1st to 10th	Night	16% 2 6% 35% 37% 4	567
	11th to 20th	Night	14% 2 8% 32% 39% 5%	564
	21st to end	Night	12% 2 7% 34% 39% 7%	817
September	1st to 10th	Night	14% 2 8% 32% 38% 7%	760
	11th to 20th	Night	17% 3 9% 33% 33% 6%	760
	21st to end	Night	27% 4 14% 30% 24% 2	760
October	1st to 10th	Night	19% 4 17% 30% 25% 4	760
	11th to 20th	Night	16% 6% 22% 36% 17% 2	760
	21st to end	Night	17% 6% 21% 40% 15% 2	836
November	1st to 10th	Night	17% 6% 23% 37% 13% 2	780
	11th to 20th	Night	18% 9% 27% 34% 12% 1	800
	21st to end	Night	17% 9% 27% 37% 11% 1	800
December	1st to 10th	Night	23% 10% 32% 29% 6%	800
	11th to 20th	Night	19% 8% 34% 34% 5%	800
	21st to end	Night	22% 11% 28% 34% 4	851

Page generated at 2024-12-21 04:13:47. Version ac07

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