Lion's Head Dark Sky Viewing Platform
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lion's Head Dark Sky Viewing Platform clear sky chart from 2005-11-06 to 2024-02-20.

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% 10% 4 8% 7% 4 5% 5% 5% 6% 32%	78138
	Night	16% 12% 6% 10% 8% 4 5% 4 5% 6% 25%	81051
Transparency	Day	52% 8% 11% 18% 9% 1	77844
	Night	60% 7% 10% 14% 7% 1	80881
Seeing	Day	19% 13% 29% 25% 12% 3	14152
	Night	22% 13% 26% 26% 12% 2	23574

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	17% 20% 13% 17% 11% 4 4 4 3 2 5%	2208
	11th to 20th	Day	11% 18% 12% 22% 15% 5% 6% 3 2 1 3	2534
	21st to end	Day	18% 19% 9% 15% 10% 5% 5% 4 4 4 7%	3124
February	1st to 10th	Day	13% 16% 8% 15% 12% 5% 5% 4 5% 4 14%	1710
	11th to 20th	Day	10% 14% 7% 14% 11% 6% 6% 6% 5% 5% 16%	1654
	21st to end	Day	14% 13% 6% 10% 8% 7% 7% 5% 5% 5% 20%	1441
March	1st to 10th	Day	12% 10% 5% 8% 8% 4 5% 4 5% 7% 32%	1907
	11th to 20th	Day	11% 9% 5% 11% 7% 4 6% 4 6% 5% 32%	1980
	21st to end	Day	15% 8% 4 7% 8% 3 5% 5% 5% 6% 35%	2178
April	1st to 10th	Day	18% 9% 4 6% 6% 4 5% 5% 5% 7% 31%	2083
	11th to 20th	Day	17% 8% 3 6% 5% 3 4 4 4 6% 40%	2312
	21st to end	Day	18% 8% 3 5% 4 3 4 5% 5% 8% 36%	2340
May	1st to 10th	Day	16% 6% 3 6% 5% 2 5% 4 5% 8% 39%	2340
	11th to 20th	Day	15% 7% 3 5% 5% 2 4 4 4 6% 44%	2402
	21st to end	Day	10% 4 3 5% 4 3 4 4 5% 8% 49%	2725
June	1st to 10th	Day	13% 5% 2 5% 5% 4 5% 6% 6% 8% 42%	2684
	11th to 20th	Day	10% 5% 2 5% 5% 3 5% 5% 6% 8% 46%	2700
	21st to end	Day	11% 6% 2 4 5% 3 4 5% 6% 8% 45%	2700
July	1st to 10th	Day	8% 4 2 4 4 3 5% 5% 5% 9% 52%	2700
	11th to 20th	Day	9% 5% 2 6% 4 3 4 4 6% 8% 48%	2666
	21st to end	Day	8% 4 2 5% 5% 2 6% 4 6% 8% 49%	2570
August	1st to 10th	Day	11% 4 2 4 4 2 4 4 6% 8% 50%	2327
	11th to 20th	Day	9% 4 2 5% 5% 3 5% 5% 6% 9% 46%	2303
	21st to end	Day	12% 6% 2 5% 5% 4 5% 5% 6% 8% 42%	2569
September	1st to 10th	Day	13% 6% 2 6% 5% 2 4 4 5% 8% 43%	2134
	11th to 20th	Day	13% 4 2 5% 5% 2 4 6% 6% 7% 44%	1980
	21st to end	Day	17% 6% 2 6% 6% 4 4 4 5% 7% 38%	1980
October	1st to 10th	Day	18% 10% 3 5% 6% 3 4 5% 5% 7% 34%	1828
	11th to 20th	Day	23% 12% 4 8% 7% 4 5% 5% 5% 6% 22%	1800
	21st to end	Day	26% 14% 5% 9% 6% 3 5% 5% 5% 5% 17%	1896
November	1st to 10th	Day	15% 15% 4 8% 8% 4 6% 5% 6% 5% 23%	1625
	11th to 20th	Day	18% 14% 5% 9% 9% 5% 7% 5% 5% 6% 17%	1520
	21st to end	Day	18% 22% 8% 12% 8% 4 5% 4 4 4 11%	1520
December	1st to 10th	Day	15% 23% 9% 15% 10% 5% 6% 5% 2 2 7%	1520
	11th to 20th	Day	18% 20% 8% 16% 10% 5% 5% 4 4 4 7%	1747
	21st to end	Day	26% 21% 7% 18% 7% 3 4 3 2 3 5%	2431
January	1st to 10th	Night	17% 20% 9% 18% 10% 4 5% 4 3 4 7%	4744
	11th to 20th	Night	14% 16% 10% 22% 15% 5% 4 3 3 2 5%	4432
	21st to end	Night	16% 18% 10% 14% 12% 6% 6% 4 3 3 8%	4532
February	1st to 10th	Night	11% 17% 8% 15% 10% 5% 5% 5% 4 5% 15%	2470
	11th to 20th	Night	10% 14% 8% 14% 10% 5% 6% 5% 5% 5% 19%	2397
	21st to end	Night	15% 12% 7% 9% 9% 3 7% 6% 4 5% 23%	1812
March	1st to 10th	Night	12% 11% 5% 9% 7% 4 5% 4 4 6% 33%	2038
	11th to 20th	Night	12% 11% 6% 8% 7% 3 5% 5% 5% 5% 34%	1979
	21st to end	Night	15% 9% 4 7% 6% 4 5% 5% 5% 6% 36%	2178
April	1st to 10th	Night	20% 9% 4 6% 4 3 5% 5% 4 6% 34%	1891
	11th to 20th	Night	18% 7% 3 6% 5% 3 3 5% 5% 6% 39%	1597
	21st to end	Night	19% 9% 3 7% 5% 3 4 5% 5% 6% 33%	1620
May	1st to 10th	Night	15% 6% 3 6% 6% 3 6% 5% 5% 7% 38%	1620
	11th to 20th	Night	15% 5% 3 5% 6% 3 5% 4 6% 6% 42%	1487
	21st to end	Night	10% 5% 2 6% 5% 2 4 5% 6% 8% 46%	1550
June	1st to 10th	Night	12% 6% 3 7% 6% 4 4 4 5% 8% 40%	1272
	11th to 20th	Night	10% 6% 2 4 5% 3 5% 5% 6% 8% 45%	1260
	21st to end	Night	11% 6% 2 5% 6% 4 5% 5% 5% 8% 43%	1260
July	1st to 10th	Night	7% 5% 2 3 3 3 4 5% 5% 9% 53%	1260
	11th to 20th	Night	8% 5% 2 6% 5% 4 5% 4 6% 9% 46%	1290
	21st to end	Night	7% 4 3 4 5% 3 5% 6% 6% 8% 49%	1745
August	1st to 10th	Night	10% 4 3 4 4 2 4 4 6% 8% 51%	1611
	11th to 20th	Night	8% 5% 2 4 5% 4 5% 6% 6% 9% 47%	1598
	21st to end	Night	11% 6% 3 5% 4 3 5% 5% 6% 8% 44%	1782
September	1st to 10th	Night	10% 5% 2 5% 4 3 5% 5% 6% 8% 47%	1808
	11th to 20th	Night	12% 4 2 6% 4 3 4 5% 5% 7% 47%	1980
	21st to end	Night	17% 7% 3 6% 6% 4 4 4 5% 7% 36%	1980
October	1st to 10th	Night	20% 7% 3 7% 7% 3 5% 4 5% 6% 32%	2132
	11th to 20th	Night	23% 11% 4 8% 7% 4 5% 5% 5% 7% 22%	2160
	21st to end	Night	26% 14% 5% 7% 7% 5% 5% 4 5% 5% 17%	2456
November	1st to 10th	Night	17% 13% 4 8% 8% 4 5% 5% 5% 7% 24%	2450
	11th to 20th	Night	16% 16% 6% 10% 8% 5% 6% 5% 4 6% 17%	2660
	21st to end	Night	22% 19% 5% 11% 9% 4 5% 4 4 5% 11%	2660
December	1st to 10th	Night	19% 22% 8% 14% 9% 4 5% 4 4 4 7%	2660
	11th to 20th	Night	15% 21% 9% 17% 8% 4 5% 4 4 4 9%	3444
	21st to end	Night	24% 21% 10% 16% 6% 3 4 3 3 3 7%	5236

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	86% 6% 5% 2	2209
	11th to 20th	Day	90% 5% 3 2	2534
	21st to end	Day	80% 9% 7% 3 1	3124
February	1st to 10th	Day	73% 7% 8% 10% 1	1710
	11th to 20th	Day	68% 8% 9% 9% 5%	1663
	21st to end	Day	62% 8% 10% 15% 5%	1441
March	1st to 10th	Day	52% 7% 13% 18% 9% 1	1910
	11th to 20th	Day	52% 7% 10% 19% 9% 2	1980
	21st to end	Day	49% 6% 10% 19% 13% 2	2178
April	1st to 10th	Day	51% 8% 12% 18% 10% 1	2083
	11th to 20th	Day	46% 6% 9% 23% 15% 2	2312
	21st to end	Day	46% 7% 12% 20% 12% 3	2340
May	1st to 10th	Day	42% 6% 10% 24% 14% 4	2340
	11th to 20th	Day	40% 7% 9% 25% 17% 2	2406
	21st to end	Day	34% 7% 16% 24% 16% 2	2725
June	1st to 10th	Day	37% 8% 13% 25% 16% 1	2684
	11th to 20th	Day	35% 7% 12% 26% 18% 2	2700
	21st to end	Day	36% 8% 14% 27% 14% 2	2700
July	1st to 10th	Day	29% 7% 15% 28% 18% 2	2626
	11th to 20th	Day	32% 9% 13% 31% 12% 2	2585
	21st to end	Day	32% 9% 14% 28% 15% 1	2427
August	1st to 10th	Day	31% 8% 18% 27% 14% 1	2314
	11th to 20th	Day	32% 10% 17% 28% 13%	2303
	21st to end	Day	37% 9% 17% 24% 12% 1	2569
September	1st to 10th	Day	38% 8% 14% 26% 12% 1	2134
	11th to 20th	Day	36% 9% 16% 29% 10%	1980
	21st to end	Day	46% 9% 15% 23% 7%	1980
October	1st to 10th	Day	50% 7% 13% 19% 10% 1	1828
	11th to 20th	Day	63% 7% 13% 12% 5% 1	1800
	21st to end	Day	68% 8% 10% 11% 3	1896
November	1st to 10th	Day	62% 8% 11% 14% 5%	1625
	11th to 20th	Day	68% 9% 11% 8% 4	1520
	21st to end	Day	77% 8% 9% 5% 1	1520
December	1st to 10th	Day	83% 7% 5% 3 1	1520
	11th to 20th	Day	81% 8% 6% 5%	1747
	21st to end	Day	86% 7% 5% 2	2431
January	1st to 10th	Night	84% 6% 7% 3	4744
	11th to 20th	Night	86% 7% 5% 2 1	4432
	21st to end	Night	79% 10% 6% 4 1	4532
February	1st to 10th	Night	71% 6% 9% 10% 3	2470
	11th to 20th	Night	67% 7% 9% 13% 4	2399
	21st to end	Night	62% 8% 11% 13% 6%	1812
March	1st to 10th	Night	52% 6% 12% 17% 11% 1	2048
	11th to 20th	Night	52% 7% 9% 18% 12% 2	1980
	21st to end	Night	48% 6% 10% 20% 14% 3	2178
April	1st to 10th	Night	51% 5% 10% 21% 11% 2	1891
	11th to 20th	Night	44% 5% 8% 22% 18% 2	1597
	21st to end	Night	51% 6% 10% 15% 15% 2	1620
May	1st to 10th	Night	43% 7% 10% 20% 15% 3	1620
	11th to 20th	Night	42% 5% 8% 22% 21% 3	1488
	21st to end	Night	35% 7% 15% 23% 16% 4	1551
June	1st to 10th	Night	42% 7% 9% 21% 18% 3	1272
	11th to 20th	Night	34% 6% 13% 26% 19% 1	1260
	21st to end	Night	38% 8% 13% 26% 13% 2	1260
July	1st to 10th	Night	27% 6% 13% 28% 22% 4	1225
	11th to 20th	Night	33% 8% 11% 30% 16% 2	1248
	21st to end	Night	31% 9% 15% 27% 18% 1	1648
August	1st to 10th	Night	30% 8% 19% 26% 15% 2	1600
	11th to 20th	Night	33% 8% 18% 24% 15% 1	1598
	21st to end	Night	38% 9% 15% 26% 12% 2	1782
September	1st to 10th	Night	33% 9% 14% 28% 15% 1	1808
	11th to 20th	Night	37% 9% 16% 28% 11%	1980
	21st to end	Night	47% 7% 15% 24% 7%	1980
October	1st to 10th	Night	52% 7% 10% 20% 10%	2132
	11th to 20th	Night	63% 8% 11% 14% 3	2160
	21st to end	Night	69% 7% 9% 10% 4	2456
November	1st to 10th	Night	60% 8% 10% 17% 4	2450
	11th to 20th	Night	68% 8% 13% 7% 3 1	2660
	21st to end	Night	76% 8% 10% 5% 1	2660
December	1st to 10th	Night	82% 7% 6% 4 1	2660
	11th to 20th	Night	80% 7% 8% 4 1	3444
	21st to end	Night	85% 6% 7% 2	5236

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	19% 26% 34% 13% 6% 2	180
	11th to 20th	Day	24% 20% 34% 17% 6%	270
	21st to end	Day	27% 14% 36% 18% 6%	297
February	1st to 10th	Day	25% 27% 30% 15% 2	270
	11th to 20th	Day	21% 25% 37% 15% 1	267
	21st to end	Day	27% 31% 35% 7% 1	198
March	1st to 10th	Day	22% 18% 36% 19% 5% 1	350
	11th to 20th	Day	21% 17% 35% 20% 5% 1	420
	21st to end	Day	26% 12% 31% 24% 5% 2	462
April	1st to 10th	Day	23% 13% 35% 20% 9% 1	420
	11th to 20th	Day	26% 14% 28% 16% 10% 5%	412
	21st to end	Day	26% 10% 35% 19% 8% 2	420
May	1st to 10th	Day	21% 9% 35% 22% 11% 2	423
	11th to 20th	Day	17% 10% 28% 28% 13% 4	447
	21st to end	Day	14% 6% 30% 29% 16% 5%	485
June	1st to 10th	Day	12% 6% 32% 34% 14% 2	614
	11th to 20th	Day	12% 8% 31% 33% 13% 3	630
	21st to end	Day	16% 6% 28% 34% 13% 3	630
July	1st to 10th	Day	9% 5% 25% 34% 24% 3	621
	11th to 20th	Day	13% 5% 26% 32% 17% 6%	618
	21st to end	Day	10% 5% 28% 34% 18% 5%	511
August	1st to 10th	Day	15% 4 20% 32% 22% 7%	446
	11th to 20th	Day	11% 5% 17% 38% 19% 9%	439
	21st to end	Day	13% 10% 26% 26% 19% 5%	495
September	1st to 10th	Day	15% 10% 23% 26% 19% 7%	450
	11th to 20th	Day	12% 7% 27% 26% 22% 6%	450
	21st to end	Day	18% 13% 22% 26% 16% 4	450
October	1st to 10th	Day	24% 15% 23% 22% 13% 3	450
	11th to 20th	Day	24% 22% 30% 19% 5% 1	450
	21st to end	Day	30% 20% 28% 18% 3 1	411
November	1st to 10th	Day	26% 22% 31% 16% 4	248
	11th to 20th	Day	21% 27% 32% 16% 4 1	180
	21st to end	Day	27% 26% 32% 13% 2	180
December	1st to 10th	Day	27% 25% 31% 13% 4	180
	11th to 20th	Day	30% 24% 32% 12% 3	180
	21st to end	Day	31% 27% 34% 5% 2 1	198
January	1st to 10th	Night	24% 20% 32% 19% 5% 1	950
	11th to 20th	Night	27% 21% 27% 19% 6% 1	942
	21st to end	Night	21% 15% 30% 25% 8% 1	836
February	1st to 10th	Night	22% 21% 32% 20% 5%	760
	11th to 20th	Night	20% 16% 35% 22% 8%	742
	21st to end	Night	22% 18% 34% 22% 4	592
March	1st to 10th	Night	18% 16% 33% 25% 8% 1	720
	11th to 20th	Night	18% 18% 33% 22% 8% 1	720
	21st to end	Night	19% 12% 28% 29% 11% 1	792
April	1st to 10th	Night	25% 13% 29% 27% 6% 1	716
	11th to 20th	Night	21% 13% 27% 25% 13% 2	533
	21st to end	Night	25% 10% 24% 27% 14% 1	540
May	1st to 10th	Night	18% 5% 25% 34% 16% 2	540
	11th to 20th	Night	17% 6% 22% 34% 20% 2	426
	21st to end	Night	14% 3 24% 37% 19% 3	389
June	1st to 10th	Night	16% 4 28% 35% 14% 2	360
	11th to 20th	Night	13% 5% 23% 39% 19% 1	360
	21st to end	Night	12% 5% 22% 36% 24% 1	360
July	1st to 10th	Night	9% 4 14% 50% 21% 2	350
	11th to 20th	Night	10% 3 22% 34% 26% 4	378
	21st to end	Night	9% 4 18% 43% 24% 2	591
August	1st to 10th	Night	10% 3 19% 38% 26% 4	537
	11th to 20th	Night	10% 6% 14% 32% 30% 7%	534
	21st to end	Night	14% 5% 23% 30% 25% 4	594
September	1st to 10th	Night	12% 6% 21% 33% 22% 7%	706
	11th to 20th	Night	13% 7% 21% 33% 21% 5%	720
	21st to end	Night	19% 9% 21% 26% 19% 6%	720
October	1st to 10th	Night	24% 9% 25% 24% 17% 2	720
	11th to 20th	Night	29% 15% 24% 22% 9% 2	720
	21st to end	Night	34% 12% 27% 22% 4 1	792
November	1st to 10th	Night	28% 15% 25% 23% 8% 1	740
	11th to 20th	Night	26% 21% 26% 19% 8% 1	760
	21st to end	Night	32% 18% 27% 18% 4	760
December	1st to 10th	Night	32% 21% 28% 13% 6%	760
	11th to 20th	Night	28% 22% 32% 14% 4	869
	21st to end	Night	34% 17% 29% 16% 4	1045

Page generated at 2024-02-17 06:28:40. Version ac07

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