Pine Cone Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pine Cone Observatory 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	15% 6% 3 5% 5% 3 5% 5% 5% 7% 41%	74760
	Night	15% 6% 3 5% 5% 3 4 4 5% 7% 43%	74980
Transparency	Day	40% 7% 12% 22% 16% 3	74465
	Night	40% 6% 12% 22% 17% 3	74809
Seeing	Day	19% 12% 29% 23% 12% 4	13925
	Night	18% 10% 31% 30% 10% 1	23263

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	13% 7% 3 5% 4 4 4 5% 5% 5% 44%	1517
	11th to 20th	Day	15% 7% 3 5% 5% 3 5% 5% 5% 6% 41%	1463
	21st to end	Day	17% 7% 3 5% 4 3 4 3 7% 6% 42%	1782
February	1st to 10th	Day	16% 7% 3 7% 5% 3 4 3 5% 7% 39%	1623
	11th to 20th	Day	18% 7% 2 4 5% 3 5% 4 5% 6% 41%	1748
	21st to end	Day	17% 9% 3 6% 5% 3 3 4 4 6% 40%	1480
March	1st to 10th	Day	14% 6% 2 5% 5% 3 4 3 4 6% 47%	1797
	11th to 20th	Day	16% 7% 3 5% 5% 4 4 5% 5% 7% 41%	1931
	21st to end	Day	19% 8% 2 4 4 3 5% 5% 4 5% 40%	2334
April	1st to 10th	Day	16% 7% 3 5% 4 3 5% 4 5% 6% 42%	2160
	11th to 20th	Day	15% 4 3 4 5% 2 4 5% 6% 8% 44%	2134
	21st to end	Day	18% 5% 3 5% 5% 3 5% 6% 5% 7% 40%	2160
May	1st to 10th	Day	20% 6% 3 6% 5% 3 4 4 6% 7% 36%	2308
	11th to 20th	Day	19% 6% 2 5% 4 3 5% 4 5% 8% 37%	2455
	21st to end	Day	14% 7% 3 5% 5% 3 4 5% 5% 8% 41%	2725
June	1st to 10th	Day	13% 6% 2 5% 6% 4 5% 5% 6% 10% 39%	2520
	11th to 20th	Day	13% 6% 3 5% 6% 3 6% 5% 6% 9% 39%	2520
	21st to end	Day	11% 4 2 6% 5% 4 5% 6% 6% 9% 40%	2520
July	1st to 10th	Day	11% 6% 2 5% 6% 4 6% 5% 7% 9% 39%	2520
	11th to 20th	Day	7% 5% 3 5% 6% 4 6% 7% 7% 10% 40%	2520
	21st to end	Day	10% 6% 3 6% 7% 4 6% 7% 7% 9% 35%	2744
August	1st to 10th	Day	10% 6% 3 7% 7% 4 6% 5% 7% 8% 37%	2296
	11th to 20th	Day	12% 6% 2 4 7% 4 6% 6% 6% 8% 39%	2126
	21st to end	Day	13% 6% 3 6% 4 3 5% 6% 7% 9% 38%	2376
September	1st to 10th	Day	14% 6% 2 4 5% 4 5% 4 5% 8% 43%	2160
	11th to 20th	Day	13% 5% 2 5% 4 3 4 4 4 8% 48%	2102
	21st to end	Day	17% 6% 3 6% 4 3 4 5% 5% 6% 41%	1980
October	1st to 10th	Day	20% 6% 2 5% 3 2 3 4 4 6% 44%	1854
	11th to 20th	Day	17% 5% 3 3 4 2 4 4 4 6% 48%	1800
	21st to end	Day	18% 6% 2 5% 4 2 4 4 4 6% 45%	1882
November	1st to 10th	Day	14% 5% 2 4 4 2 3 4 4 6% 52%	1671
	11th to 20th	Day	16% 6% 2 5% 4 3 3 4 4 6% 47%	1710
	21st to end	Day	14% 5% 2 5% 4 4 3 5% 5% 7% 46%	1644
December	1st to 10th	Day	18% 7% 3 5% 5% 3 4 4 4 8% 40%	1520
	11th to 20th	Day	19% 8% 3 5% 4 2 3 3 4 5% 45%	1906
	21st to end	Day	16% 7% 2 4 5% 3 5% 6% 6% 7% 38%	2772
January	1st to 10th	Night	16% 6% 3 4 4 2 4 4 5% 6% 46%	2649
	11th to 20th	Night	19% 6% 2 5% 4 3 4 5% 5% 7% 39%	2556
	21st to end	Night	15% 7% 3 4 5% 3 5% 4 5% 6% 44%	2574
February	1st to 10th	Night	17% 9% 3 5% 5% 2 4 4 4 6% 41%	2336
	11th to 20th	Night	18% 8% 3 5% 4 2 4 4 5% 6% 41%	2098
	21st to end	Night	18% 7% 3 6% 4 2 3 4 5% 4 43%	1776
March	1st to 10th	Night	15% 5% 2 5% 5% 3 4 3 4 7% 47%	2150
	11th to 20th	Night	18% 7% 3 5% 4 2 4 3 4 6% 43%	2025
	21st to end	Night	18% 7% 3 6% 4 3 4 4 3 6% 42%	2021
April	1st to 10th	Night	16% 8% 3 6% 4 2 4 4 4 6% 42%	1800
	11th to 20th	Night	14% 7% 3 6% 4 3 4 3 4 7% 44%	1775
	21st to end	Night	19% 6% 2 5% 3 3 4 4 6% 8% 42%	1800
May	1st to 10th	Night	18% 8% 4 6% 5% 3 4 4 6% 7% 36%	1651
	11th to 20th	Night	18% 7% 3 6% 4 2 4 5% 5% 8% 37%	1452
	21st to end	Night	14% 8% 3 5% 6% 3 5% 5% 4 7% 39%	1550
June	1st to 10th	Night	15% 5% 3 5% 4 2 4 6% 6% 8% 42%	1440
	11th to 20th	Night	11% 7% 2 5% 7% 3 6% 5% 5% 8% 41%	1440
	21st to end	Night	9% 5% 2 4 5% 3 5% 7% 8% 11% 41%	1440
July	1st to 10th	Night	10% 6% 4 5% 7% 3 6% 5% 8% 10% 37%	1440
	11th to 20th	Night	6% 5% 3 5% 5% 3 6% 5% 7% 9% 44%	1440
	21st to end	Night	8% 5% 3 5% 6% 4 5% 5% 7% 10% 43%	1574
August	1st to 10th	Night	8% 6% 2 6% 6% 4 5% 5% 7% 9% 41%	1622
	11th to 20th	Night	10% 7% 3 6% 6% 4 5% 4 7% 8% 41%	1774
	21st to end	Night	13% 5% 3 6% 5% 3 4 5% 6% 8% 42%	1980
September	1st to 10th	Night	15% 6% 2 5% 5% 4 5% 4 4 6% 45%	1800
	11th to 20th	Night	10% 6% 2 3 4 2 4 4 5% 7% 53%	1858
	21st to end	Night	17% 7% 2 5% 5% 2 3 4 5% 8% 42%	1980
October	1st to 10th	Night	18% 6% 3 5% 4 2 4 4 4 6% 44%	2102
	11th to 20th	Night	15% 5% 2 4 4 2 4 4 4 6% 50%	2160
	21st to end	Night	18% 7% 2 4 4 2 3 4 4 5% 47%	2474
November	1st to 10th	Night	12% 5% 2 5% 4 3 3 3 5% 7% 52%	2407
	11th to 20th	Night	17% 5% 3 5% 4 2 4 3 4 5% 48%	2470
	21st to end	Night	13% 6% 2 4 5% 3 5% 4 5% 7% 46%	2534
December	1st to 10th	Night	20% 7% 3 5% 4 3 4 5% 5% 6% 40%	2660
	11th to 20th	Night	17% 6% 2 5% 5% 3 4 4 5% 7% 42%	3288
	21st to end	Night	17% 8% 3 5% 5% 3 4 5% 5% 6% 39%	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	40% 5% 12% 21% 15% 5%	1518
	11th to 20th	Day	42% 6% 13% 22% 13% 3	1463
	21st to end	Day	41% 5% 11% 25% 15% 4	1782
February	1st to 10th	Day	45% 5% 13% 24% 12% 1	1623
	11th to 20th	Day	43% 6% 10% 23% 15% 3	1757
	21st to end	Day	47% 5% 8% 21% 13% 5%	1480
March	1st to 10th	Day	39% 5% 12% 25% 15% 3	1800
	11th to 20th	Day	42% 5% 11% 22% 16% 4	1931
	21st to end	Day	45% 7% 8% 20% 16% 4	2334
April	1st to 10th	Day	42% 7% 10% 20% 16% 6%	2160
	11th to 20th	Day	37% 7% 14% 22% 17% 3	2134
	21st to end	Day	42% 7% 11% 18% 17% 5%	2160
May	1st to 10th	Day	46% 7% 12% 19% 14% 2	2308
	11th to 20th	Day	44% 7% 13% 21% 14% 2	2459
	21st to end	Day	39% 9% 15% 21% 13% 2	2725
June	1st to 10th	Day	41% 9% 13% 22% 13% 2	2520
	11th to 20th	Day	41% 9% 13% 23% 12% 2	2520
	21st to end	Day	38% 10% 12% 22% 16% 1	2520
July	1st to 10th	Day	40% 11% 14% 20% 14% 2	2450
	11th to 20th	Day	34% 10% 16% 24% 14% 2	2445
	21st to end	Day	40% 10% 13% 21% 14% 2	2591
August	1st to 10th	Day	41% 9% 15% 21% 13% 1	2282
	11th to 20th	Day	39% 11% 15% 18% 15% 2	2126
	21st to end	Day	39% 10% 13% 19% 15% 3	2376
September	1st to 10th	Day	39% 8% 14% 18% 19% 3	2160
	11th to 20th	Day	34% 5% 11% 22% 24% 3	2102
	21st to end	Day	44% 6% 8% 18% 20% 3	1980
October	1st to 10th	Day	41% 6% 13% 21% 18% 2	1854
	11th to 20th	Day	36% 6% 9% 24% 22% 2	1800
	21st to end	Day	40% 6% 9% 23% 20% 2	1882
November	1st to 10th	Day	34% 4 13% 27% 19% 3	1671
	11th to 20th	Day	38% 5% 9% 22% 23% 3	1710
	21st to end	Day	37% 6% 12% 30% 13% 2	1644
December	1st to 10th	Day	44% 5% 15% 22% 14% 1	1520
	11th to 20th	Day	41% 5% 12% 27% 13% 2	1906
	21st to end	Day	42% 8% 14% 23% 13% 1	2772
January	1st to 10th	Night	39% 5% 11% 23% 18% 4	2649
	11th to 20th	Night	43% 6% 14% 22% 12% 2	2556
	21st to end	Night	40% 5% 10% 25% 18% 3	2574
February	1st to 10th	Night	44% 6% 13% 22% 13% 2	2336
	11th to 20th	Night	44% 5% 9% 20% 17% 5%	2100
	21st to end	Night	42% 5% 8% 22% 18% 5%	1776
March	1st to 10th	Night	37% 4 12% 24% 18% 4	2160
	11th to 20th	Night	43% 5% 9% 21% 17% 4	2026
	21st to end	Night	45% 5% 10% 18% 18% 6%	2021
April	1st to 10th	Night	43% 5% 10% 19% 18% 5%	1800
	11th to 20th	Night	41% 5% 10% 21% 19% 3	1775
	21st to end	Night	40% 7% 10% 18% 20% 5%	1800
May	1st to 10th	Night	47% 8% 9% 19% 16% 2	1651
	11th to 20th	Night	45% 7% 13% 15% 17% 3	1453
	21st to end	Night	44% 9% 14% 18% 13% 2	1551
June	1st to 10th	Night	40% 9% 11% 21% 18% 2	1440
	11th to 20th	Night	41% 10% 13% 22% 13% 2	1440
	21st to end	Night	33% 9% 17% 22% 16% 2	1440
July	1st to 10th	Night	40% 12% 16% 18% 11% 2	1400
	11th to 20th	Night	33% 11% 15% 25% 14% 2	1392
	21st to end	Night	33% 9% 17% 26% 13% 2	1486
August	1st to 10th	Night	37% 10% 18% 19% 15% 1	1612
	11th to 20th	Night	40% 8% 16% 20% 15% 1	1774
	21st to end	Night	38% 8% 15% 17% 19% 3	1980
September	1st to 10th	Night	40% 8% 12% 19% 18% 3	1800
	11th to 20th	Night	31% 6% 13% 22% 24% 4	1858
	21st to end	Night	40% 7% 8% 22% 20% 3	1980
October	1st to 10th	Night	41% 7% 12% 21% 17% 2	2102
	11th to 20th	Night	35% 5% 12% 28% 18% 3	2160
	21st to end	Night	40% 6% 9% 24% 20% 2	2474
November	1st to 10th	Night	33% 5% 12% 24% 20% 5%	2407
	11th to 20th	Night	40% 5% 8% 22% 20% 5%	2470
	21st to end	Night	36% 5% 13% 26% 18% 2	2534
December	1st to 10th	Night	45% 5% 12% 23% 14% 2	2660
	11th to 20th	Night	41% 5% 13% 19% 18% 4	3288
	21st to end	Night	43% 8% 13% 24% 11% 1	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	21% 22% 36% 16% 4 1	180
	11th to 20th	Day	26% 29% 28% 15% 2	167
	21st to end	Day	23% 25% 31% 14% 5% 2	264
February	1st to 10th	Day	25% 24% 37% 11% 3	243
	11th to 20th	Day	28% 20% 37% 13% 2	416
	21st to end	Day	29% 21% 30% 17% 2	346
March	1st to 10th	Day	20% 23% 33% 20% 4	420
	11th to 20th	Day	18% 24% 38% 13% 5% 2	420
	21st to end	Day	24% 19% 32% 19% 6%	462
April	1st to 10th	Day	21% 21% 35% 15% 6% 1	420
	11th to 20th	Day	18% 17% 34% 20% 8% 2	412
	21st to end	Day	26% 17% 34% 15% 6% 2	420
May	1st to 10th	Day	27% 18% 29% 16% 8% 2	423
	11th to 20th	Day	22% 11% 36% 21% 8% 3	447
	21st to end	Day	20% 8% 21% 27% 20% 5%	485
June	1st to 10th	Day	15% 9% 30% 26% 16% 4	450
	11th to 20th	Day	15% 9% 31% 27% 15% 3	450
	21st to end	Day	13% 7% 27% 32% 17% 4	450
July	1st to 10th	Day	15% 2 21% 30% 24% 8%	445
	11th to 20th	Day	6% 2 25% 34% 26% 7%	444
	21st to end	Day	11% 5% 26% 32% 20% 6%	488
August	1st to 10th	Day	10% 4 26% 33% 21% 8%	446
	11th to 20th	Day	14% 1 21% 32% 23% 8%	439
	21st to end	Day	12% 5% 22% 30% 20% 11%	495
September	1st to 10th	Day	16% 7% 24% 24% 18% 11%	450
	11th to 20th	Day	13% 4 25% 30% 18% 10%	450
	21st to end	Day	22% 8% 26% 26% 14% 5%	450
October	1st to 10th	Day	24% 6% 25% 24% 15% 6%	450
	11th to 20th	Day	17% 13% 28% 26% 13% 3	450
	21st to end	Day	20% 12% 34% 22% 11% 2	446
November	1st to 10th	Day	16% 10% 35% 24% 13% 3	365
	11th to 20th	Day	19% 18% 31% 24% 8%	370
	21st to end	Day	17% 15% 33% 25% 9% 1	304
December	1st to 10th	Day	25% 20% 36% 9% 9% 1	180
	11th to 20th	Day	29% 16% 35% 15% 4 1	180
	21st to end	Day	26% 15% 33% 19% 6% 2	198
January	1st to 10th	Night	19% 16% 38% 23% 4	760
	11th to 20th	Night	23% 14% 34% 25% 4	732
	21st to end	Night	19% 15% 40% 24% 2	792
February	1st to 10th	Night	21% 15% 38% 24% 2	720
	11th to 20th	Night	24% 19% 39% 17% 2	703
	21st to end	Night	23% 20% 35% 19% 2	592
March	1st to 10th	Night	20% 15% 39% 23% 4	720
	11th to 20th	Night	21% 15% 37% 21% 6% 1	720
	21st to end	Night	21% 10% 41% 21% 6%	792
April	1st to 10th	Night	20% 18% 37% 19% 6%	720
	11th to 20th	Night	18% 12% 38% 28% 5%	711
	21st to end	Night	21% 10% 35% 28% 6%	720
May	1st to 10th	Night	20% 11% 35% 27% 8%	571
	11th to 20th	Night	21% 8% 36% 30% 5%	391
	21st to end	Night	19% 4 19% 42% 14% 2	389
June	1st to 10th	Night	17% 3 28% 39% 12% 1	360
	11th to 20th	Night	13% 3 25% 43% 15%	360
	21st to end	Night	8% 4 26% 47% 15%	360
July	1st to 10th	Night	11% 3 20% 44% 21% 1	350
	11th to 20th	Night	7% 3 18% 47% 22% 2	348
	21st to end	Night	8% 2 22% 49% 18% 1	394
August	1st to 10th	Night	10% 1 15% 49% 22% 3	548
	11th to 20th	Night	13% 3 17% 39% 27% 2	710
	21st to end	Night	13% 3 16% 41% 25% 3	792
September	1st to 10th	Night	17% 2 20% 39% 19% 3	720
	11th to 20th	Night	13% 3 18% 38% 23% 5%	720
	21st to end	Night	21% 4 23% 34% 17% 1	720
October	1st to 10th	Night	22% 5% 25% 28% 17% 3	720
	11th to 20th	Night	18% 8% 26% 36% 13% 1	720
	21st to end	Night	20% 9% 35% 26% 9% 1	792
November	1st to 10th	Night	15% 7% 35% 30% 12% 1	740
	11th to 20th	Night	19% 13% 31% 29% 8% 1	760
	21st to end	Night	15% 13% 36% 28% 9% 1	760
December	1st to 10th	Night	24% 13% 35% 21% 7% 1	760
	11th to 20th	Night	19% 13% 37% 25% 6%	760
	21st to end	Night	20% 12% 36% 29% 3	836

Page generated at 2024-01-10 19:35:25. Version ac07

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