Lake Somerville State Park - Birch Creek Unit
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lake Somerville State Park - Birch Creek Unit clear sky chart from 2005-11-06 to 2024-01-13.

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	11% 6% 2 5% 5% 3 5% 5% 6% 8% 45%	74927
	Night	11% 5% 2 4 4 2 4 4 5% 7% 51%	74844
Transparency	Day	38% 6% 11% 20% 18% 8%	74652
	Night	33% 5% 12% 21% 19% 10%	74639
Seeing	Day	12% 6% 19% 27% 26% 10%	13747
	Night	13% 7% 25% 36% 18% 2	23758

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	18% 6% 2 4 4 3 3 4 4 5% 48%	1707
	11th to 20th	Day	18% 7% 2 4 4 2 4 2 5% 6% 45%	1643
	21st to end	Day	16% 6% 3 5% 5% 2 3 3 4 5% 48%	1782
February	1st to 10th	Day	21% 9% 4 5% 4 2 3 3 3 5% 41%	1796
	11th to 20th	Day	20% 9% 3 5% 4 3 3 3 4 5% 42%	1749
	21st to end	Day	18% 8% 2 6% 4 3 4 4 4 5% 42%	1552
March	1st to 10th	Day	20% 8% 3 6% 5% 3 5% 4 4 6% 37%	1980
	11th to 20th	Day	16% 8% 4 6% 5% 3 4 3 4 6% 42%	1980
	21st to end	Day	16% 6% 3 6% 4 2 3 4 4 5% 46%	2178
April	1st to 10th	Day	14% 7% 3 7% 5% 3 4 5% 4 8% 39%	1980
	11th to 20th	Day	14% 7% 3 7% 6% 3 5% 4 5% 5% 42%	2020
	21st to end	Day	13% 5% 3 5% 5% 3 5% 4 5% 7% 46%	2173
May	1st to 10th	Day	12% 6% 3 5% 6% 3 5% 5% 6% 9% 40%	2340
	11th to 20th	Day	11% 6% 3 6% 6% 3 5% 5% 6% 7% 43%	2302
	21st to end	Day	11% 6% 3 6% 7% 4 6% 5% 8% 9% 35%	2531
June	1st to 10th	Day	5% 4 2 4 5% 4 6% 6% 8% 10% 46%	2340
	11th to 20th	Day	5% 3 2 4 5% 3 6% 7% 7% 10% 47%	2340
	21st to end	Day	6% 5% 3 6% 7% 5% 8% 7% 9% 10% 36%	2340
July	1st to 10th	Day	9% 5% 3 6% 8% 4 6% 6% 8% 11% 34%	2340
	11th to 20th	Day	4 3 2 5% 5% 4 7% 7% 8% 12% 44%	2340
	21st to end	Day	3 3 2 5% 6% 4 6% 6% 7% 13% 45%	2546
August	1st to 10th	Day	3 2 1 4 4 3 5% 6% 5% 10% 57%	2328
	11th to 20th	Day	5% 3 2 5% 4 4 5% 6% 7% 10% 48%	2301
	21st to end	Day	5% 4 2 5% 6% 5% 5% 6% 8% 11% 43%	2198
September	1st to 10th	Day	5% 5% 2 6% 6% 4 6% 6% 6% 10% 44%	1980
	11th to 20th	Day	12% 6% 2 5% 6% 4 6% 5% 5% 8% 41%	1980
	21st to end	Day	6% 4 2 4 6% 4 6% 6% 6% 7% 49%	1980
October	1st to 10th	Day	6% 4 2 3 4 3 4 5% 6% 8% 56%	1942
	11th to 20th	Day	13% 5% 2 4 4 2 4 4 5% 5% 54%	1800
	21st to end	Day	13% 5% 1 4 3 2 3 3 4 6% 56%	1980
November	1st to 10th	Day	12% 6% 2 5% 4 3 4 5% 5% 7% 48%	1858
	11th to 20th	Day	11% 7% 2 5% 4 2 4 3 4 7% 52%	1900
	21st to end	Day	18% 7% 2 5% 5% 3 4 4 4 5% 42%	1715
December	1st to 10th	Day	15% 8% 2 5% 6% 2 3 4 4 6% 45%	1710
	11th to 20th	Day	18% 7% 2 5% 5% 3 4 3 4 6% 43%	2161
	21st to end	Day	16% 8% 3 5% 4 2 3 3 4 5% 48%	3135
January	1st to 10th	Night	17% 6% 2 4 3 2 3 3 4 6% 50%	2458
	11th to 20th	Night	17% 7% 2 4 3 2 3 3 3 5% 50%	2379
	21st to end	Night	16% 6% 3 4 4 2 3 3 4 5% 50%	2574
February	1st to 10th	Night	17% 8% 3 6% 4 2 3 3 3 5% 45%	2179
	11th to 20th	Night	20% 7% 3 5% 4 2 3 3 3 5% 48%	2098
	21st to end	Night	20% 5% 4 5% 3 3 4 4 4 6% 43%	1703
March	1st to 10th	Night	16% 8% 2 5% 4 2 4 4 5% 8% 42%	1980
	11th to 20th	Night	14% 7% 3 5% 5% 3 4 4 5% 6% 43%	1980
	21st to end	Night	14% 5% 2 4 4 2 4 4 4 6% 51%	2178
April	1st to 10th	Night	11% 6% 3 4 5% 3 4 4 6% 8% 47%	1980
	11th to 20th	Night	13% 6% 3 5% 4 3 4 4 5% 8% 45%	1888
	21st to end	Night	13% 6% 2 4 5% 3 3 4 5% 6% 49%	1782
May	1st to 10th	Night	11% 4 3 6% 5% 3 5% 4 7% 9% 44%	1620
	11th to 20th	Night	9% 5% 2 4 4 3 4 4 6% 8% 49%	1593
	21st to end	Night	6% 5% 2 4 5% 3 6% 5% 6% 9% 49%	1745
June	1st to 10th	Night	4 2 2 4 4 2 3 5% 6% 10% 59%	1620
	11th to 20th	Night	4 2 1 3 3 1 4 6% 6% 10% 60%	1620
	21st to end	Night	4 3 2 5% 5% 3 5% 6% 8% 11% 49%	1620
July	1st to 10th	Night	6% 3 2 3 4 3 5% 6% 7% 12% 48%	1620
	11th to 20th	Night	2 2 1 3 3 2 5% 5% 6% 10% 61%	1620
	21st to end	Night	3 2 1 3 3 3 5% 5% 7% 13% 56%	1772
August	1st to 10th	Night	1 1 1 2 2 2 3 4 5% 12% 68%	1611
	11th to 20th	Night	3 3 1 4 4 3 5% 5% 7% 13% 51%	1600
	21st to end	Night	4 3 2 4 4 3 6% 6% 8% 12% 49%	2151
September	1st to 10th	Night	6% 3 2 4 4 3 5% 6% 6% 9% 53%	1980
	11th to 20th	Night	10% 5% 2 5% 5% 3 4 4 5% 9% 46%	1980
	21st to end	Night	7% 3 2 4 4 3 3 6% 6% 9% 55%	1980
October	1st to 10th	Night	4 3 1 3 4 2 3 5% 5% 7% 63%	1998
	11th to 20th	Night	11% 4 2 3 3 2 3 3 4 6% 58%	2160
	21st to end	Night	12% 5% 2 3 3 2 3 3 4 4 60%	2376
November	1st to 10th	Night	11% 5% 2 3 4 3 3 4 4 6% 54%	2220
	11th to 20th	Night	10% 6% 2 4 4 3 4 4 4 6% 52%	2280
	21st to end	Night	16% 6% 3 5% 4 3 4 4 4 7% 46%	2461
December	1st to 10th	Night	16% 7% 3 4 4 2 4 3 4 6% 47%	2470
	11th to 20th	Night	16% 8% 3 4 5% 2 4 4 4 6% 44%	3036
	21st to end	Night	16% 7% 2 4 4 2 3 3 4 5% 52%	4532

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	40% 4 6% 18% 22% 11%	1708
	11th to 20th	Day	41% 4 5% 17% 21% 11%	1643
	21st to end	Day	40% 3 5% 14% 23% 14%	1782
February	1st to 10th	Day	47% 4 5% 12% 19% 13%	1796
	11th to 20th	Day	47% 3 7% 15% 18% 9%	1759
	21st to end	Day	45% 4 8% 15% 16% 13%	1552
March	1st to 10th	Day	49% 4 8% 12% 20% 7%	1980
	11th to 20th	Day	46% 4 6% 12% 21% 11%	1980
	21st to end	Day	41% 5% 7% 17% 22% 8%	2178
April	1st to 10th	Day	45% 6% 6% 19% 15% 10%	1980
	11th to 20th	Day	45% 4 8% 15% 19% 10%	2020
	21st to end	Day	39% 4 7% 20% 22% 8%	2173
May	1st to 10th	Day	41% 6% 10% 18% 16% 9%	2340
	11th to 20th	Day	40% 5% 12% 22% 19% 3	2306
	21st to end	Day	43% 8% 12% 22% 13% 2	2531
June	1st to 10th	Day	32% 7% 14% 28% 17% 3	2340
	11th to 20th	Day	29% 8% 15% 27% 18% 4	2340
	21st to end	Day	40% 10% 13% 24% 11% 2	2340
July	1st to 10th	Day	41% 9% 18% 23% 8% 1	2276
	11th to 20th	Day	30% 9% 21% 22% 17% 1	2271
	21st to end	Day	26% 9% 24% 31% 9% 1	2405
August	1st to 10th	Day	23% 8% 18% 34% 15% 1	2314
	11th to 20th	Day	30% 9% 21% 26% 11% 3	2301
	21st to end	Day	34% 9% 17% 25% 12% 3	2198
September	1st to 10th	Day	36% 9% 12% 21% 16% 6%	1980
	11th to 20th	Day	41% 8% 13% 17% 17% 4	1980
	21st to end	Day	34% 6% 9% 22% 17% 12%	1980
October	1st to 10th	Day	26% 5% 10% 23% 23% 13%	1942
	11th to 20th	Day	34% 4 7% 17% 21% 17%	1800
	21st to end	Day	33% 3 5% 16% 24% 19%	1980
November	1st to 10th	Day	35% 6% 8% 19% 21% 10%	1858
	11th to 20th	Day	33% 4 10% 18% 21% 13%	1900
	21st to end	Day	43% 4 8% 16% 18% 11%	1715
December	1st to 10th	Day	42% 3 10% 18% 19% 7%	1710
	11th to 20th	Day	44% 3 8% 12% 23% 10%	2159
	21st to end	Day	41% 3 5% 14% 26% 11%	3135
January	1st to 10th	Night	38% 3 5% 17% 21% 14%	2458
	11th to 20th	Night	38% 3 6% 17% 22% 14%	2379
	21st to end	Night	39% 3 4 16% 21% 17%	2574
February	1st to 10th	Night	45% 3 6% 12% 19% 15%	2179
	11th to 20th	Night	42% 4 6% 16% 19% 14%	2098
	21st to end	Night	45% 4 6% 14% 15% 15%	1703
March	1st to 10th	Night	42% 6% 10% 15% 18% 10%	1980
	11th to 20th	Night	41% 6% 9% 14% 19% 11%	1980
	21st to end	Night	35% 5% 11% 16% 21% 12%	2178
April	1st to 10th	Night	36% 5% 11% 20% 17% 11%	1980
	11th to 20th	Night	39% 5% 11% 16% 17% 14%	1888
	21st to end	Night	37% 4 9% 22% 20% 8%	1782
May	1st to 10th	Night	37% 6% 11% 20% 18% 8%	1620
	11th to 20th	Night	33% 6% 13% 26% 18% 4	1594
	21st to end	Night	32% 7% 15% 31% 14% 1	1746
June	1st to 10th	Night	23% 6% 17% 31% 22% 2	1620
	11th to 20th	Night	19% 7% 17% 33% 18% 5%	1620
	21st to end	Night	28% 9% 17% 29% 14% 2	1620
July	1st to 10th	Night	28% 10% 22% 31% 9%	1575
	11th to 20th	Night	18% 8% 27% 32% 15% 1	1566
	21st to end	Night	17% 9% 31% 32% 10%	1673
August	1st to 10th	Night	11% 6% 26% 37% 18% 2	1601
	11th to 20th	Night	24% 7% 23% 34% 10% 2	1600
	21st to end	Night	26% 11% 24% 28% 10% 3	2151
September	1st to 10th	Night	26% 9% 19% 25% 15% 7%	1980
	11th to 20th	Night	36% 6% 15% 22% 13% 6%	1980
	21st to end	Night	26% 7% 16% 20% 19% 13%	1980
October	1st to 10th	Night	21% 5% 12% 27% 21% 14%	1998
	11th to 20th	Night	29% 3 7% 20% 24% 17%	2160
	21st to end	Night	29% 3 6% 18% 22% 22%	2376
November	1st to 10th	Night	32% 5% 9% 20% 21% 12%	2220
	11th to 20th	Night	34% 4 9% 19% 20% 13%	2280
	21st to end	Night	39% 4 9% 17% 19% 13%	2461
December	1st to 10th	Night	39% 4 7% 22% 17% 10%	2470
	11th to 20th	Night	42% 4 6% 12% 20% 15%	3037
	21st to end	Night	38% 3 5% 15% 29% 11%	4532

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	23% 7% 37% 24% 7% 2	270
	11th to 20th	Day	19% 13% 29% 28% 8% 2	248
	21st to end	Day	19% 16% 36% 22% 6%	264
February	1st to 10th	Day	31% 11% 30% 21% 6%	240
	11th to 20th	Day	28% 17% 29% 19% 7%	240
	21st to end	Day	26% 19% 35% 16% 4 1	198
March	1st to 10th	Day	20% 18% 33% 21% 8%	240
	11th to 20th	Day	18% 16% 39% 20% 6% 1	240
	21st to end	Day	17% 14% 36% 24% 7% 1	264
April	1st to 10th	Day	16% 14% 42% 21% 6% 1	240
	11th to 20th	Day	19% 18% 28% 24% 9% 1	298
	21st to end	Day	14% 12% 36% 26% 11% 1	433
May	1st to 10th	Day	12% 10% 35% 32% 11% 1	603
	11th to 20th	Day	13% 6% 25% 34% 17% 4	625
	21st to end	Day	11% 6% 24% 36% 20% 3	679
June	1st to 10th	Day	5% 2 12% 40% 33% 9%	630
	11th to 20th	Day	6% 1 13% 41% 32% 7%	630
	21st to end	Day	6% 3 12% 30% 37% 13%	630
July	1st to 10th	Day	6% 2 8% 29% 38% 17%	621
	11th to 20th	Day	2 3 30% 46% 19%	618
	21st to end	Day	3 1 4 24% 49% 18%	684
August	1st to 10th	Day	3 3 24% 50% 20%	626
	11th to 20th	Day	5% 3 22% 50% 20%	615
	21st to end	Day	6% 1 3 18% 31% 40%	317
September	1st to 10th	Day	6% 1 3 20% 38% 32%	270
	11th to 20th	Day	7% 2 5% 19% 39% 29%	270
	21st to end	Day	8% 1 7% 21% 41% 22%	270
October	1st to 10th	Day	3 2 11% 30% 40% 14%	270
	11th to 20th	Day	12% 4 18% 31% 25% 10%	270
	21st to end	Day	20% 11% 23% 22% 19% 6%	297
November	1st to 10th	Day	16% 6% 17% 34% 20% 7%	270
	11th to 20th	Day	19% 9% 23% 29% 16% 5%	270
	21st to end	Day	22% 16% 32% 19% 9% 3	270
December	1st to 10th	Day	19% 7% 31% 24% 14% 6%	270
	11th to 20th	Day	23% 15% 27% 25% 7% 2	270
	21st to end	Day	23% 7% 38% 23% 6% 2	297
January	1st to 10th	Night	20% 9% 32% 31% 8%	950
	11th to 20th	Night	21% 11% 29% 31% 8%	915
	21st to end	Night	18% 12% 32% 31% 6%	990
February	1st to 10th	Night	23% 12% 34% 27% 4	739
	11th to 20th	Night	23% 11% 35% 26% 5%	704
	21st to end	Night	25% 13% 41% 18% 3	519
March	1st to 10th	Night	18% 13% 40% 26% 3	540
	11th to 20th	Night	15% 12% 37% 31% 5%	540
	21st to end	Night	14% 10% 41% 29% 5%	594
April	1st to 10th	Night	12% 10% 44% 31% 4	540
	11th to 20th	Night	13% 14% 37% 29% 6%	533
	21st to end	Night	12% 11% 40% 27% 8% 1	540
May	1st to 10th	Night	12% 10% 43% 30% 5%	540
	11th to 20th	Night	9% 7% 34% 37% 13% 1	531
	21st to end	Night	5% 4 31% 43% 16% 1	584
June	1st to 10th	Night	4 2 15% 51% 26% 2	540
	11th to 20th	Night	3 1 24% 50% 21% 1	540
	21st to end	Night	4 1 11% 47% 33% 4	540
July	1st to 10th	Night	5% 1 9% 46% 34% 3	525
	11th to 20th	Night	2 1 7% 51% 36% 3	522
	21st to end	Night	3 5% 52% 36% 3	591
August	1st to 10th	Night	1 4 56% 36% 3	537
	11th to 20th	Night	4 5% 51% 35% 5%	534
	21st to end	Night	4 1 5% 36% 48% 6%	594
September	1st to 10th	Night	6% 1 7% 33% 47% 6%	540
	11th to 20th	Night	10% 1 7% 34% 44% 4	540
	21st to end	Night	9% 1 13% 33% 40% 4	540
October	1st to 10th	Night	4 1 12% 44% 34% 5%	558
	11th to 20th	Night	12% 4 21% 40% 21% 2	720
	21st to end	Night	13% 8% 27% 32% 19% 2	792
November	1st to 10th	Night	12% 4 22% 41% 20% 1	740
	11th to 20th	Night	11% 9% 24% 38% 15% 1	760
	21st to end	Night	17% 11% 29% 29% 14% 1	941
December	1st to 10th	Night	18% 8% 27% 33% 12% 1	950
	11th to 20th	Night	23% 11% 28% 30% 7% 1	950
	21st to end	Night	19% 9% 31% 31% 9%	1045

Page generated at 2024-01-10 18:35:24. Version ac07

Copyright 2024 Attilla Danko