Piney Mountain
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Piney Mountain clear sky chart from 2005-11-06 to 2024-03-18.

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	14% 6% 3 6% 5% 3 5% 5% 6% 8% 39%	78682
	Night	15% 6% 3 5% 5% 3 4 5% 5% 7% 41%	81105
Transparency	Day	43% 7% 13% 22% 14% 2	78392
	Night	42% 6% 13% 23% 14% 2	80914
Seeing	Day	20% 17% 27% 21% 12% 4	13957
	Night	18% 16% 29% 27% 11% 1	23568

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% 7% 3 7% 6% 3 4 5% 5% 6% 40%	2517
	11th to 20th	Day	13% 12% 5% 7% 7% 5% 5% 5% 6% 6% 29%	2836
	21st to end	Day	16% 12% 4 7% 6% 4 4 4 5% 6% 31%	3124
February	1st to 10th	Day	15% 9% 3 6% 6% 3 7% 5% 4 6% 36%	1710
	11th to 20th	Day	13% 8% 4 6% 6% 4 6% 5% 4 7% 36%	1689
	21st to end	Day	20% 7% 4 8% 5% 3 4 4 4 6% 36%	1570
March	1st to 10th	Day	13% 6% 3 5% 5% 3 5% 5% 5% 6% 45%	2043
	11th to 20th	Day	15% 7% 2 6% 6% 3 5% 5% 5% 8% 38%	2058
	21st to end	Day	18% 8% 3 5% 5% 4 5% 3 5% 7% 37%	2212
April	1st to 10th	Day	13% 7% 3 7% 7% 4 4 5% 5% 7% 38%	2160
	11th to 20th	Day	14% 7% 2 5% 6% 3 4 5% 4 8% 42%	2134
	21st to end	Day	19% 7% 2 5% 5% 3 5% 5% 6% 6% 38%	2161
May	1st to 10th	Day	18% 6% 3 6% 5% 3 5% 5% 6% 8% 34%	2340
	11th to 20th	Day	21% 6% 3 6% 5% 3 5% 5% 5% 6% 35%	2450
	21st to end	Day	14% 6% 2 6% 6% 4 5% 5% 6% 8% 39%	2725
June	1st to 10th	Day	13% 5% 2 5% 5% 3 5% 5% 7% 10% 39%	2520
	11th to 20th	Day	13% 5% 2 7% 6% 3 6% 6% 7% 9% 37%	2520
	21st to end	Day	10% 3 2 4 5% 3 5% 6% 7% 11% 43%	2520
July	1st to 10th	Day	9% 5% 2 6% 6% 3 6% 6% 6% 9% 41%	2520
	11th to 20th	Day	6% 4 3 5% 5% 4 6% 6% 7% 10% 43%	2502
	21st to end	Day	10% 5% 3 6% 6% 4 7% 7% 7% 10% 36%	2547
August	1st to 10th	Day	9% 5% 3 6% 6% 4 7% 7% 8% 9% 37%	2327
	11th to 20th	Day	13% 5% 3 5% 5% 3 5% 6% 7% 9% 39%	2236
	21st to end	Day	13% 4 2 5% 5% 3 5% 6% 6% 9% 40%	2376
September	1st to 10th	Day	17% 5% 2 5% 3 3 5% 4 6% 6% 43%	2160
	11th to 20th	Day	14% 4 2 4 4 3 4 5% 6% 7% 47%	2160
	21st to end	Day	19% 6% 2 5% 5% 3 4 4 4 6% 41%	1890
October	1st to 10th	Day	16% 6% 2 4 5% 3 5% 5% 5% 6% 44%	1800
	11th to 20th	Day	17% 5% 3 5% 4 2 5% 4 5% 7% 44%	1800
	21st to end	Day	15% 7% 2 5% 6% 3 4 5% 4 7% 42%	1980
November	1st to 10th	Day	12% 6% 2 4 3 2 4 4 5% 8% 50%	1732
	11th to 20th	Day	16% 5% 3 3 5% 2 4 5% 5% 7% 44%	1641
	21st to end	Day	16% 6% 2 4 6% 4 4 5% 5% 8% 41%	1520
December	1st to 10th	Day	17% 7% 3 6% 6% 3 5% 6% 6% 8% 33%	1520
	11th to 20th	Day	16% 6% 3 6% 6% 4 6% 5% 6% 8% 35%	1910
	21st to end	Day	18% 7% 3 8% 6% 3 5% 6% 6% 7% 30%	2772
January	1st to 10th	Night	13% 7% 3 6% 7% 3 4 5% 5% 8% 38%	4429
	11th to 20th	Night	16% 8% 3 6% 5% 3 4 4 5% 6% 39%	4120
	21st to end	Night	19% 10% 4 6% 5% 4 4 3 5% 6% 33%	4532
February	1st to 10th	Night	16% 7% 3 6% 5% 3 5% 4 5% 6% 39%	2470
	11th to 20th	Night	15% 8% 3 6% 6% 3 4 5% 5% 6% 38%	2375
	21st to end	Night	17% 8% 3 6% 5% 3 5% 5% 5% 6% 37%	1884
March	1st to 10th	Night	13% 5% 2 4 5% 3 4 4 5% 7% 46%	2133
	11th to 20th	Night	17% 6% 3 5% 5% 3 4 4 5% 7% 43%	2068
	21st to end	Night	17% 7% 3 6% 5% 3 5% 4 5% 7% 39%	2142
April	1st to 10th	Night	16% 7% 3 6% 7% 4 5% 6% 5% 7% 35%	1800
	11th to 20th	Night	14% 6% 2 6% 4 3 4 4 5% 9% 43%	1775
	21st to end	Night	20% 5% 2 4 4 2 4 5% 6% 7% 42%	1800
May	1st to 10th	Night	18% 7% 2 6% 5% 3 4 4 5% 6% 39%	1634
	11th to 20th	Night	19% 7% 3 5% 5% 2 4 6% 5% 7% 38%	1443
	21st to end	Night	14% 6% 2 4 4 4 5% 5% 5% 10% 40%	1550
June	1st to 10th	Night	13% 5% 3 4 3 2 6% 4 5% 8% 48%	1440
	11th to 20th	Night	12% 5% 3 5% 5% 5% 6% 5% 6% 10% 39%	1440
	21st to end	Night	10% 4 2 4 4 4 5% 5% 7% 10% 45%	1440
July	1st to 10th	Night	10% 5% 2 5% 6% 4 5% 5% 8% 10% 41%	1440
	11th to 20th	Night	6% 4 2 4 5% 4 5% 5% 6% 11% 48%	1454
	21st to end	Night	9% 4 2 4 5% 3 5% 4 7% 12% 44%	1771
August	1st to 10th	Night	9% 4 2 6% 5% 4 4 7% 6% 10% 43%	1611
	11th to 20th	Night	10% 6% 2 6% 7% 4 4 3 5% 9% 43%	1645
	21st to end	Night	13% 4 2 4 5% 4 4 4 6% 10% 45%	1980
September	1st to 10th	Night	16% 4 3 6% 4 3 4 3 4 7% 47%	1800
	11th to 20th	Night	13% 4 2 4 3 3 3 3 4 7% 54%	1800
	21st to end	Night	18% 6% 3 4 4 3 4 5% 5% 6% 43%	2065
October	1st to 10th	Night	18% 7% 2 4 4 2 4 4 4 6% 44%	2160
	11th to 20th	Night	15% 5% 2 4 5% 2 4 4 4 6% 48%	2160
	21st to end	Night	16% 6% 2 4 4 3 5% 4 5% 6% 44%	2376
November	1st to 10th	Night	11% 5% 2 5% 4 3 4 4 5% 6% 51%	2343
	11th to 20th	Night	14% 7% 2 5% 5% 2 4 4 5% 7% 46%	2536
	21st to end	Night	14% 4 3 5% 5% 4 4 5% 6% 7% 44%	2660
December	1st to 10th	Night	16% 7% 3 6% 6% 4 5% 6% 5% 7% 36%	2660
	11th to 20th	Night	17% 6% 2 5% 5% 3 4 5% 6% 7% 39%	3285
	21st to end	Night	16% 7% 3 6% 6% 4 6% 6% 6% 8% 31%	4884

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	44% 5% 14% 24% 9% 4	2518
	11th to 20th	Day	53% 6% 11% 16% 11% 3	2836
	21st to end	Day	54% 5% 10% 22% 7% 1	3124
February	1st to 10th	Day	49% 5% 13% 21% 10% 2	1710
	11th to 20th	Day	47% 6% 11% 23% 11% 2	1698
	21st to end	Day	49% 5% 11% 20% 11% 4	1570
March	1st to 10th	Day	40% 6% 12% 25% 15% 2	2043
	11th to 20th	Day	44% 5% 13% 19% 14% 5%	2058
	21st to end	Day	49% 5% 10% 19% 15% 2	2212
April	1st to 10th	Day	45% 6% 13% 18% 16% 3	2160
	11th to 20th	Day	41% 6% 11% 21% 17% 4	2134
	21st to end	Day	45% 6% 10% 21% 15% 3	2161
May	1st to 10th	Day	45% 7% 12% 20% 15% 2	2340
	11th to 20th	Day	50% 7% 10% 18% 13% 2	2454
	21st to end	Day	42% 7% 16% 21% 11% 2	2725
June	1st to 10th	Day	39% 8% 15% 23% 15% 1	2520
	11th to 20th	Day	41% 9% 15% 21% 13% 2	2520
	21st to end	Day	33% 9% 15% 28% 14% 1	2520
July	1st to 10th	Day	37% 10% 13% 21% 16% 3	2450
	11th to 20th	Day	32% 9% 14% 26% 16% 3	2427
	21st to end	Day	39% 10% 12% 20% 16% 2	2405
August	1st to 10th	Day	39% 10% 16% 23% 11%	2314
	11th to 20th	Day	39% 8% 14% 22% 15% 1	2236
	21st to end	Day	38% 8% 13% 24% 14% 3	2376
September	1st to 10th	Day	40% 7% 13% 19% 18% 4	2160
	11th to 20th	Day	33% 6% 12% 25% 20% 3	2160
	21st to end	Day	43% 5% 10% 19% 20% 3	1890
October	1st to 10th	Day	41% 6% 12% 23% 16% 2	1800
	11th to 20th	Day	39% 6% 12% 24% 18% 1	1800
	21st to end	Day	41% 6% 10% 25% 16% 2	1980
November	1st to 10th	Day	33% 6% 14% 24% 19% 5%	1732
	11th to 20th	Day	39% 6% 12% 22% 18% 3	1641
	21st to end	Day	41% 6% 12% 29% 10% 2	1520
December	1st to 10th	Day	48% 8% 15% 19% 9% 1	1520
	11th to 20th	Day	47% 5% 13% 26% 7% 1	1906
	21st to end	Day	51% 9% 16% 16% 8%	2772
January	1st to 10th	Night	45% 7% 13% 24% 10% 2	4429
	11th to 20th	Night	46% 5% 15% 23% 10% 2	4120
	21st to end	Night	53% 5% 9% 23% 8% 2	4532
February	1st to 10th	Night	45% 6% 13% 23% 11% 1	2470
	11th to 20th	Night	46% 5% 12% 19% 17% 2	2377
	21st to end	Night	47% 5% 11% 19% 14% 4	1884
March	1st to 10th	Night	37% 6% 12% 26% 16% 2	2133
	11th to 20th	Night	42% 6% 11% 23% 15% 3	2068
	21st to end	Night	44% 6% 12% 19% 16% 4	2142
April	1st to 10th	Night	48% 6% 11% 17% 15% 3	1800
	11th to 20th	Night	38% 7% 11% 21% 18% 5%	1775
	21st to end	Night	41% 6% 12% 21% 16% 5%	1800
May	1st to 10th	Night	45% 7% 10% 21% 13% 4	1634
	11th to 20th	Night	44% 7% 12% 18% 17% 2	1444
	21st to end	Night	40% 8% 15% 23% 12% 2	1551
June	1st to 10th	Night	35% 8% 11% 26% 17% 3	1440
	11th to 20th	Night	39% 10% 13% 21% 15% 2	1440
	21st to end	Night	33% 9% 14% 26% 17% 1	1440
July	1st to 10th	Night	38% 10% 15% 20% 14% 3	1400
	11th to 20th	Night	29% 10% 17% 24% 17% 3	1406
	21st to end	Night	30% 9% 20% 22% 17% 2	1672
August	1st to 10th	Night	34% 9% 17% 25% 13% 1	1600
	11th to 20th	Night	39% 7% 14% 21% 18% 1	1645
	21st to end	Night	36% 8% 14% 23% 16% 3	1980
September	1st to 10th	Night	38% 5% 13% 21% 19% 4	1800
	11th to 20th	Night	31% 5% 10% 28% 23% 3	1800
	21st to end	Night	42% 6% 10% 21% 19% 2	2065
October	1st to 10th	Night	41% 5% 12% 24% 16% 2	2160
	11th to 20th	Night	36% 7% 10% 28% 17% 2	2160
	21st to end	Night	40% 5% 9% 27% 17% 2	2376
November	1st to 10th	Night	33% 5% 12% 25% 20% 5%	2343
	11th to 20th	Night	38% 5% 10% 25% 18% 4	2536
	21st to end	Night	39% 6% 14% 25% 15% 2	2660
December	1st to 10th	Night	47% 7% 13% 22% 11%	2660
	11th to 20th	Night	42% 7% 14% 21% 14% 2	3288
	21st to end	Night	48% 9% 15% 19% 8%	4884

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	26% 33% 27% 12% 2 1	180
	11th to 20th	Day	31% 28% 31% 9% 2	268
	21st to end	Day	22% 36% 30% 9% 3	297
February	1st to 10th	Day	27% 31% 31% 10% 1	270
	11th to 20th	Day	31% 33% 31% 3 1	296
	21st to end	Day	32% 24% 27% 15% 2	382
March	1st to 10th	Day	26% 26% 27% 18% 3	460
	11th to 20th	Day	24% 31% 27% 13% 4 1	449
	21st to end	Day	27% 23% 30% 14% 4 2	462
April	1st to 10th	Day	22% 26% 31% 14% 6% 1	420
	11th to 20th	Day	19% 23% 29% 15% 11% 2	412
	21st to end	Day	27% 20% 32% 14% 5% 2	420
May	1st to 10th	Day	26% 21% 27% 17% 7% 3	423
	11th to 20th	Day	21% 19% 28% 20% 10% 2	447
	21st to end	Day	16% 9% 26% 25% 17% 6%	485
June	1st to 10th	Day	15% 15% 30% 19% 17% 4	450
	11th to 20th	Day	18% 12% 29% 23% 13% 4	450
	21st to end	Day	10% 11% 31% 28% 16% 4	450
July	1st to 10th	Day	12% 5% 24% 30% 20% 10%	445
	11th to 20th	Day	5% 6% 26% 31% 24% 9%	444
	21st to end	Day	11% 6% 25% 32% 20% 5%	488
August	1st to 10th	Day	10% 5% 21% 31% 24% 9%	446
	11th to 20th	Day	13% 7% 21% 31% 19% 9%	439
	21st to end	Day	11% 5% 23% 32% 18% 10%	495
September	1st to 10th	Day	20% 7% 20% 23% 19% 11%	450
	11th to 20th	Day	15% 5% 19% 31% 21% 8%	450
	21st to end	Day	23% 14% 24% 22% 13% 5%	450
October	1st to 10th	Day	20% 10% 24% 23% 17% 5%	450
	11th to 20th	Day	18% 20% 27% 22% 11% 2	450
	21st to end	Day	18% 19% 36% 18% 9% 1	495
November	1st to 10th	Day	18% 17% 27% 23% 13% 2	395
	11th to 20th	Day	22% 25% 26% 20% 7% 1	301
	21st to end	Day	22% 24% 34% 14% 6%	180
December	1st to 10th	Day	25% 29% 28% 13% 4 1	180
	11th to 20th	Day	26% 28% 28% 13% 4	180
	21st to end	Day	22% 27% 28% 18% 5% 1	198
January	1st to 10th	Night	17% 29% 33% 19% 2	760
	11th to 20th	Night	22% 21% 31% 23% 3	760
	21st to end	Night	18% 25% 36% 20% 2	836
February	1st to 10th	Night	20% 23% 31% 24% 2	760
	11th to 20th	Night	22% 29% 36% 13% 1	743
	21st to end	Night	24% 25% 33% 15% 2	628
March	1st to 10th	Night	20% 22% 36% 19% 4	760
	11th to 20th	Night	22% 22% 31% 18% 6%	752
	21st to end	Night	20% 18% 39% 17% 5% 1	792
April	1st to 10th	Night	21% 27% 31% 17% 5%	720
	11th to 20th	Night	17% 18% 32% 24% 8% 1	711
	21st to end	Night	23% 15% 31% 24% 7%	720
May	1st to 10th	Night	21% 12% 28% 27% 11% 1	554
	11th to 20th	Night	19% 9% 34% 30% 8%	382
	21st to end	Night	15% 8% 22% 39% 15% 1	389
June	1st to 10th	Night	14% 3 28% 35% 19% 1	360
	11th to 20th	Night	14% 8% 26% 35% 17% 1	360
	21st to end	Night	10% 3 26% 48% 13%	360
July	1st to 10th	Night	11% 4 21% 36% 25% 3	350
	11th to 20th	Night	6% 2 19% 46% 25% 1	362
	21st to end	Night	10% 3 20% 42% 24% 2	591
August	1st to 10th	Night	11% 2 15% 45% 25% 3	537
	11th to 20th	Night	12% 6% 15% 39% 25% 4	581
	21st to end	Night	14% 3 17% 36% 26% 3	792
September	1st to 10th	Night	16% 4 21% 33% 23% 3	720
	11th to 20th	Night	13% 5% 19% 34% 26% 4	720
	21st to end	Night	20% 8% 21% 29% 20% 2	720
October	1st to 10th	Night	21% 8% 22% 28% 18% 3	720
	11th to 20th	Night	18% 14% 28% 30% 9% 1	720
	21st to end	Night	20% 16% 30% 26% 9% 1	792
November	1st to 10th	Night	14% 15% 33% 28% 10% 1	740
	11th to 20th	Night	18% 23% 29% 23% 7% 1	760
	21st to end	Night	17% 22% 31% 25% 5%	760
December	1st to 10th	Night	21% 20% 34% 19% 5% 1	760
	11th to 20th	Night	19% 20% 35% 23% 4	760
	21st to end	Night	18% 21% 34% 25% 3	836

Page generated at 2024-03-15 14:01:44. Version ac07

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