Little Piney Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Little Piney Observatory clear sky chart from 2005-11-06 to 2024-01-22.

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	15% 6% 2 5% 4 3 4 4 5% 7% 45%	74498
	Night	15% 5% 2 4 4 2 3 4 5% 7% 50%	75454
Transparency	Day	38% 7% 11% 22% 17% 4	74221
	Night	34% 6% 11% 23% 20% 5%	75251
Seeing	Day	16% 9% 21% 27% 21% 6%	14279
	Night	16% 8% 22% 33% 19% 2	24238

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	19% 8% 2 4 3 2 3 2 3 5% 50%	1707
	11th to 20th	Day	18% 7% 3 5% 4 2 3 3 4 5% 46%	1710
	21st to end	Day	17% 6% 2 4 4 2 3 3 3 5% 51%	1791
February	1st to 10th	Day	23% 8% 3 4 3 2 2 2 3 4 46%	1620
	11th to 20th	Day	22% 6% 3 4 4 2 3 3 4 5% 43%	1625
	21st to end	Day	22% 9% 3 5% 4 2 3 2 4 5% 40%	1581
March	1st to 10th	Day	20% 6% 2 4 3 2 3 4 4 6% 46%	1980
	11th to 20th	Day	23% 7% 3 5% 4 2 3 4 3 5% 41%	1980
	21st to end	Day	23% 7% 3 5% 5% 3 4 3 4 5% 38%	2178
April	1st to 10th	Day	19% 6% 2 5% 4 3 4 4 5% 6% 42%	2117
	11th to 20th	Day	20% 6% 2 5% 4 2 4 4 5% 6% 42%	2134
	21st to end	Day	22% 6% 2 5% 5% 3 5% 4 4 5% 40%	2160
May	1st to 10th	Day	20% 6% 3 5% 5% 3 4 4 5% 6% 38%	2237
	11th to 20th	Day	16% 6% 2 5% 6% 3 5% 5% 5% 8% 39%	2302
	21st to end	Day	13% 6% 3 7% 6% 4 4 7% 6% 8% 38%	2531
June	1st to 10th	Day	10% 6% 3 5% 4 3 5% 6% 6% 9% 42%	2340
	11th to 20th	Day	7% 4 2 4 6% 4 6% 6% 8% 10% 43%	2340
	21st to end	Day	6% 3 2 4 4 3 5% 6% 6% 9% 51%	2340
July	1st to 10th	Day	8% 5% 2 5% 6% 4 6% 6% 7% 12% 38%	2340
	11th to 20th	Day	6% 4 2 4 6% 4 6% 6% 6% 9% 48%	2340
	21st to end	Day	6% 4 2 5% 6% 4 6% 7% 7% 10% 44%	2546
August	1st to 10th	Day	7% 5% 2 5% 6% 4 6% 5% 7% 10% 42%	2328
	11th to 20th	Day	12% 5% 2 4 5% 3 5% 5% 6% 8% 44%	2208
	21st to end	Day	8% 4 2 4 5% 4 5% 5% 5% 8% 49%	2376
September	1st to 10th	Day	11% 4 3 4 3 3 5% 4 5% 7% 50%	2160
	11th to 20th	Day	13% 3 2 3 4 3 4 5% 6% 8% 49%	2087
	21st to end	Day	10% 4 2 4 4 2 4 4 4 6% 55%	1913
October	1st to 10th	Day	10% 4 2 3 4 3 4 4 4 5% 56%	1800
	11th to 20th	Day	16% 4 2 3 3 2 3 3 4 5% 55%	1800
	21st to end	Day	21% 6% 1 3 3 2 3 4 3 4 49%	1980
November	1st to 10th	Day	14% 5% 2 4 4 2 3 2 4 5% 56%	1858
	11th to 20th	Day	14% 5% 2 3 3 2 3 4 4 5% 55%	1900
	21st to end	Day	22% 6% 3 4 2 2 3 3 3 5% 47%	1580
December	1st to 10th	Day	20% 5% 2 4 3 2 2 3 5% 6% 48%	1520
	11th to 20th	Day	17% 8% 3 5% 5% 3 4 3 3 5% 44%	1954
	21st to end	Day	20% 11% 4 7% 5% 3 3 3 4 5% 36%	3135
January	1st to 10th	Night	19% 5% 2 3 3 2 3 3 4 5% 50%	2458
	11th to 20th	Night	18% 6% 2 4 4 2 3 3 4 5% 51%	2470
	21st to end	Night	17% 5% 2 3 3 2 2 3 3 4 54%	2600
February	1st to 10th	Night	21% 8% 3 4 3 2 3 3 4 5% 44%	2340
	11th to 20th	Night	19% 6% 3 5% 3 2 3 3 5% 5% 45%	2220
	21st to end	Night	22% 5% 2 5% 3 2 2 3 4 5% 47%	1690
March	1st to 10th	Night	19% 5% 1 4 4 2 4 4 4 6% 46%	1980
	11th to 20th	Night	21% 6% 2 4 4 3 4 3 4 5% 44%	1980
	21st to end	Night	21% 7% 2 5% 4 3 3 3 3 5% 43%	2178
April	1st to 10th	Night	16% 4 3 3 4 2 4 4 4 7% 49%	1841
	11th to 20th	Night	15% 5% 2 5% 5% 2 4 4 5% 6% 47%	1775
	21st to end	Night	19% 5% 2 4 4 3 4 4 5% 7% 43%	1800
May	1st to 10th	Night	17% 4 2 4 4 2 5% 3 5% 8% 45%	1719
	11th to 20th	Night	15% 4 2 4 4 2 4 4 5% 8% 48%	1593
	21st to end	Night	11% 6% 3 4 5% 3 4 5% 5% 10% 44%	1745
June	1st to 10th	Night	7% 3 2 3 4 3 4 5% 6% 10% 53%	1620
	11th to 20th	Night	5% 3 1 2 3 2 4 4 6% 12% 57%	1620
	21st to end	Night	5% 3 2 3 3 2 3 4 6% 9% 60%	1620
July	1st to 10th	Night	5% 3 2 5% 4 4 5% 5% 8% 10% 49%	1620
	11th to 20th	Night	4 3 1 3 4 3 4 5% 6% 11% 55%	1620
	21st to end	Night	5% 3 1 4 4 3 6% 6% 7% 10% 52%	1772
August	1st to 10th	Night	4 3 1 5% 6% 3 6% 5% 7% 11% 49%	1611
	11th to 20th	Night	8% 4 2 4 4 2 4 5% 5% 9% 51%	1690
	21st to end	Night	6% 4 2 4 5% 3 4 5% 6% 9% 53%	1980
September	1st to 10th	Night	8% 4 2 3 3 3 3 5% 5% 8% 57%	1800
	11th to 20th	Night	9% 4 2 4 4 3 4 4 5% 8% 51%	1869
	21st to end	Night	8% 4 1 3 3 3 4 4 6% 6% 59%	2027
October	1st to 10th	Night	9% 3 1 3 2 2 3 5% 6% 7% 59%	2160
	11th to 20th	Night	16% 4 1 3 3 2 2 2 3 4 58%	2160
	21st to end	Night	20% 5% 2 4 3 1 2 3 3 4 53%	2376
November	1st to 10th	Night	13% 5% 2 4 3 2 3 2 3 5% 57%	2220
	11th to 20th	Night	15% 4 1 3 3 2 3 3 4 5% 57%	2280
	21st to end	Night	21% 5% 2 3 2 2 3 3 3 6% 50%	2590
December	1st to 10th	Night	20% 5% 2 4 4 3 3 3 3 5% 49%	2660
	11th to 20th	Night	19% 6% 3 6% 4 2 3 3 3 4 47%	3238
	21st to end	Night	21% 8% 3 7% 5% 3 4 4 4 5% 37%	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 8% 23% 19% 5%	1708
	11th to 20th	Day	42% 5% 8% 24% 19% 2	1710
	21st to end	Day	38% 4 8% 26% 20% 4	1791
February	1st to 10th	Day	45% 3 11% 21% 16% 4	1620
	11th to 20th	Day	43% 6% 9% 21% 18% 3	1634
	21st to end	Day	50% 3 8% 15% 17% 8%	1581
March	1st to 10th	Day	40% 5% 8% 19% 19% 9%	1980
	11th to 20th	Day	47% 5% 7% 21% 15% 5%	1980
	21st to end	Day	48% 6% 10% 22% 12% 2	2178
April	1st to 10th	Day	42% 6% 9% 19% 21% 3	2117
	11th to 20th	Day	42% 6% 9% 21% 17% 5%	2134
	21st to end	Day	46% 6% 8% 20% 17% 2	2160
May	1st to 10th	Day	46% 7% 10% 18% 17% 2	2237
	11th to 20th	Day	41% 9% 14% 22% 12% 1	2306
	21st to end	Day	42% 11% 12% 21% 13% 1	2531
June	1st to 10th	Day	35% 10% 14% 26% 14% 1	2340
	11th to 20th	Day	33% 10% 16% 22% 17% 2	2340
	21st to end	Day	26% 9% 15% 27% 18% 4	2340
July	1st to 10th	Day	35% 12% 17% 23% 13% 1	2276
	11th to 20th	Day	29% 9% 16% 26% 17% 2	2271
	21st to end	Day	30% 11% 19% 28% 11% 1	2405
August	1st to 10th	Day	33% 11% 20% 25% 11% 1	2314
	11th to 20th	Day	35% 9% 14% 24% 16% 2	2208
	21st to end	Day	31% 9% 17% 23% 15% 5%	2376
September	1st to 10th	Day	32% 8% 12% 23% 19% 7%	2160
	11th to 20th	Day	31% 8% 12% 22% 22% 5%	2087
	21st to end	Day	29% 7% 10% 20% 28% 6%	1913
October	1st to 10th	Day	30% 6% 10% 21% 26% 8%	1800
	11th to 20th	Day	32% 5% 7% 22% 25% 10%	1800
	21st to end	Day	39% 5% 7% 22% 18% 8%	1980
November	1st to 10th	Day	32% 5% 9% 25% 21% 8%	1858
	11th to 20th	Day	32% 4 9% 23% 24% 8%	1900
	21st to end	Day	41% 4 8% 19% 23% 5%	1580
December	1st to 10th	Day	37% 5% 10% 25% 19% 4	1520
	11th to 20th	Day	42% 5% 7% 20% 22% 4	1951
	21st to end	Day	48% 8% 10% 17% 13% 4	3135
January	1st to 10th	Night	36% 5% 9% 21% 24% 5%	2458
	11th to 20th	Night	38% 4 11% 23% 21% 3	2470
	21st to end	Night	34% 3 8% 25% 23% 6%	2600
February	1st to 10th	Night	44% 4 8% 22% 17% 4	2340
	11th to 20th	Night	41% 4 9% 23% 18% 5%	2221
	21st to end	Night	42% 4 7% 20% 19% 8%	1690
March	1st to 10th	Night	39% 4 10% 16% 21% 10%	1980
	11th to 20th	Night	43% 5% 10% 19% 16% 5%	1980
	21st to end	Night	44% 6% 8% 22% 16% 4	2178
April	1st to 10th	Night	35% 6% 11% 22% 20% 6%	1841
	11th to 20th	Night	36% 6% 9% 22% 19% 8%	1775
	21st to end	Night	40% 6% 10% 23% 19% 2	1800
May	1st to 10th	Night	37% 8% 13% 19% 19% 4	1719
	11th to 20th	Night	35% 8% 14% 25% 16% 3	1594
	21st to end	Night	34% 10% 16% 24% 14% 1	1746
June	1st to 10th	Night	25% 8% 15% 30% 18% 3	1620
	11th to 20th	Night	20% 7% 16% 34% 21% 2	1620
	21st to end	Night	20% 6% 18% 26% 23% 7%	1620
July	1st to 10th	Night	26% 10% 21% 24% 19% 1	1575
	11th to 20th	Night	19% 10% 18% 29% 21% 3	1566
	21st to end	Night	22% 11% 18% 31% 16% 1	1673
August	1st to 10th	Night	26% 10% 21% 30% 13%	1601
	11th to 20th	Night	28% 8% 18% 24% 20% 2	1690
	21st to end	Night	26% 9% 17% 25% 19% 4	1980
September	1st to 10th	Night	24% 8% 11% 31% 18% 8%	1800
	11th to 20th	Night	30% 8% 12% 20% 24% 7%	1869
	21st to end	Night	24% 7% 10% 22% 29% 8%	2027
October	1st to 10th	Night	23% 6% 14% 23% 23% 10%	2160
	11th to 20th	Night	31% 4 6% 18% 31% 10%	2160
	21st to end	Night	36% 4 7% 20% 23% 10%	2376
November	1st to 10th	Night	30% 5% 9% 24% 24% 9%	2220
	11th to 20th	Night	30% 4 8% 24% 26% 8%	2280
	21st to end	Night	37% 4 8% 20% 26% 5%	2590
December	1st to 10th	Night	40% 4 9% 21% 21% 6%	2660
	11th to 20th	Night	41% 5% 8% 20% 21% 5%	3240
	21st to end	Night	43% 8% 12% 20% 13% 3	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	27% 16% 29% 23% 5%	270
	11th to 20th	Day	27% 23% 32% 13% 4 1	270
	21st to end	Day	19% 24% 32% 19% 6%	267
February	1st to 10th	Day	28% 18% 35% 14% 4 1	240
	11th to 20th	Day	28% 23% 33% 13% 3	240
	21st to end	Day	38% 20% 29% 11% 3	198
March	1st to 10th	Day	26% 20% 34% 15% 5%	240
	11th to 20th	Day	30% 23% 32% 13% 2	240
	21st to end	Day	25% 22% 38% 11% 4	264
April	1st to 10th	Day	20% 17% 34% 19% 10% 1	377
	11th to 20th	Day	26% 13% 31% 21% 8% 1	412
	21st to end	Day	21% 16% 34% 20% 8% 1	420
May	1st to 10th	Day	19% 17% 28% 26% 9% 1	500
	11th to 20th	Day	18% 8% 23% 30% 17% 3	625
	21st to end	Day	11% 7% 25% 35% 17% 5%	679
June	1st to 10th	Day	11% 5% 15% 30% 31% 8%	630
	11th to 20th	Day	8% 1 16% 35% 33% 7%	630
	21st to end	Day	5% 3 20% 36% 29% 8%	630
July	1st to 10th	Day	7% 2 11% 32% 37% 11%	621
	11th to 20th	Day	6% 2 10% 30% 36% 15%	618
	21st to end	Day	6% 2 7% 29% 41% 14%	684
August	1st to 10th	Day	7% 1 11% 34% 37% 9%	626
	11th to 20th	Day	14% 2 9% 29% 37% 10%	522
	21st to end	Day	11% 2 5% 25% 42% 15%	495
September	1st to 10th	Day	10% 2 6% 28% 42% 11%	450
	11th to 20th	Day	8% 2 13% 30% 36% 11%	377
	21st to end	Day	13% 4 16% 34% 25% 7%	270
October	1st to 10th	Day	7% 5% 27% 34% 24% 4	270
	11th to 20th	Day	14% 16% 26% 30% 14% 1	270
	21st to end	Day	30% 14% 25% 21% 9% 1	297
November	1st to 10th	Day	15% 11% 29% 30% 13% 2	270
	11th to 20th	Day	15% 16% 36% 27% 6% 1	270
	21st to end	Day	26% 16% 21% 26% 9% 2	270
December	1st to 10th	Day	24% 16% 31% 20% 7% 2	270
	11th to 20th	Day	26% 14% 30% 23% 7%	270
	21st to end	Day	26% 18% 35% 17% 3	297
January	1st to 10th	Night	22% 13% 28% 32% 6%	950
	11th to 20th	Night	22% 13% 31% 29% 4	950
	21st to end	Night	20% 11% 32% 32% 5%	1000
February	1st to 10th	Night	25% 12% 30% 29% 4	900
	11th to 20th	Night	23% 14% 36% 25% 3	826
	21st to end	Night	25% 15% 33% 25% 1	506
March	1st to 10th	Night	22% 10% 28% 36% 4	540
	11th to 20th	Night	24% 10% 25% 34% 5%	540
	21st to end	Night	22% 10% 32% 29% 7%	594
April	1st to 10th	Night	16% 11% 34% 30% 8%	540
	11th to 20th	Night	16% 11% 32% 32% 10%	533
	21st to end	Night	20% 9% 30% 30% 11%	540
May	1st to 10th	Night	17% 6% 25% 40% 11%	540
	11th to 20th	Night	15% 6% 23% 33% 23% 1	531
	21st to end	Night	10% 3 20% 40% 24% 4	584
June	1st to 10th	Night	6% 4 10% 34% 43% 2	540
	11th to 20th	Night	4 1 9% 44% 39% 3	540
	21st to end	Night	5% 1 11% 35% 43% 5%	540
July	1st to 10th	Night	4 1 9% 32% 46% 8%	525
	11th to 20th	Night	4 1 8% 31% 46% 11%	522
	21st to end	Night	6% 3 32% 48% 11%	591
August	1st to 10th	Night	5% 1 6% 32% 50% 7%	537
	11th to 20th	Night	10% 1 7% 36% 40% 6%	534
	21st to end	Night	7% 2 5% 32% 48% 7%	594
September	1st to 10th	Night	9% 2 6% 34% 45% 4	540
	11th to 20th	Night	11% 2 11% 35% 37% 4	540
	21st to end	Night	10% 2 11% 36% 35% 4	587
October	1st to 10th	Night	11% 3 16% 37% 29% 4	720
	11th to 20th	Night	16% 7% 25% 36% 17%	720
	21st to end	Night	21% 9% 22% 31% 15% 2	792
November	1st to 10th	Night	14% 8% 25% 36% 17% 1	740
	11th to 20th	Night	16% 10% 26% 38% 10%	760
	21st to end	Night	21% 11% 25% 29% 14%	897
December	1st to 10th	Night	23% 8% 29% 33% 7%	950
	11th to 20th	Night	24% 11% 24% 36% 6%	950
	21st to end	Night	22% 15% 25% 32% 5%	1045

Page generated at 2024-01-19 08:28:32. Version ac07

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