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 2026-01-02.

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	16% 7% 2 6% 4 4 4 4 6% 7% 40%	127286
	Night	16% 7% 2 6% 4 4 4 3 5% 7% 43%	124082
Transparency	Day	41% 6% 12% 22% 16% 3	130826
	Night	40% 6% 11% 22% 17% 4	128629
Seeing	Day	19% 13% 30% 23% 12% 4	16501
	Night	18% 10% 31% 29% 10% 1	25781

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% 8% 2 4 3 3 3 3 4 4 52%	3605
	11th to 20th	Day	14% 7% 2 8% 5% 4 4 3 4 5% 44%	3585
	21st to end	Day	19% 9% 3 6% 4 3 3 3 4 5% 41%	4466
February	1st to 10th	Day	14% 8% 3 8% 4 4 3 3 5% 7% 40%	1804
	11th to 20th	Day	18% 8% 2 5% 5% 4 5% 3 5% 6% 41%	1948
	21st to end	Day	16% 9% 3 7% 4 3 4 3 4 6% 41%	1650
March	1st to 10th	Day	21% 6% 2 4 3 3 3 2 3 5% 46%	4476
	11th to 20th	Day	11% 8% 2 6% 4 4 4 4 5% 6% 45%	4875
	21st to end	Day	17% 7% 2 6% 4 4 5% 3 4 6% 44%	5872
April	1st to 10th	Day	17% 7% 3 6% 4 4 4 3 5% 6% 40%	2400
	11th to 20th	Day	15% 6% 3 5% 5% 3 4 4 6% 7% 42%	2374
	21st to end	Day	17% 5% 2 6% 4 4 4 5% 5% 7% 41%	2400
May	1st to 10th	Day	24% 8% 3 6% 4 4 4 4 6% 7% 29%	5812
	11th to 20th	Day	26% 8% 2 6% 3 3 3 3 4 7% 34%	6267
	21st to end	Day	20% 6% 2 5% 4 4 5% 4 6% 8% 35%	6949
June	1st to 10th	Day	13% 6% 2 6% 6% 5% 4 4 6% 9% 39%	2800
	11th to 20th	Day	14% 7% 2 5% 5% 4 5% 3 6% 9% 39%	2800
	21st to end	Day	11% 5% 2 7% 4 5% 6% 5% 6% 9% 40%	2800
July	1st to 10th	Day	9% 6% 2 7% 5% 6% 6% 5% 8% 10% 36%	6360
	11th to 20th	Day	11% 8% 3 8% 6% 5% 6% 6% 8% 10% 30%	6360
	21st to end	Day	10% 7% 3 7% 5% 5% 5% 5% 7% 9% 38%	6926
August	1st to 10th	Day	18% 7% 3 8% 5% 5% 5% 4 7% 8% 30%	4160
	11th to 20th	Day	13% 7% 2 6% 5% 5% 6% 4 7% 8% 37%	3850
	21st to end	Day	10% 5% 2 5% 4 4 6% 5% 8% 10% 42%	4312
September	1st to 10th	Day	13% 6% 2 6% 4 5% 4 4 5% 7% 44%	2400
	11th to 20th	Day	12% 5% 2 6% 3 4 4 3 5% 8% 48%	2334
	21st to end	Day	18% 7% 3 8% 4 4 4 3 5% 6% 39%	2200
October	1st to 10th	Day	19% 6% 2 5% 3 3 3 3 4 7% 46%	2060
	11th to 20th	Day	16% 6% 2 4 3 3 4 3 4 6% 50%	2000
	21st to end	Day	17% 5% 2 5% 3 3 4 3 4 6% 47%	2090
November	1st to 10th	Day	13% 6% 2 4 4 3 3 3 4 6% 53%	1851
	11th to 20th	Day	15% 6% 2 6% 4 4 3 3 5% 6% 47%	1890
	21st to end	Day	15% 6% 1 5% 4 4 4 4 5% 6% 46%	1816
December	1st to 10th	Day	13% 7% 2 5% 4 4 4 3 5% 8% 46%	2680
	11th to 20th	Day	20% 9% 3 5% 3 2 3 2 3 4 46%	3066
	21st to end	Day	15% 6% 2 5% 4 4 5% 4 6% 7% 42%	4048
January	1st to 10th	Night	13% 6% 2 5% 3 3 3 3 4 6% 52%	6364
	11th to 20th	Night	15% 7% 2 6% 4 3 3 3 4 5% 49%	6297
	21st to end	Night	17% 8% 2 6% 4 3 4 3 5% 6% 42%	6490
February	1st to 10th	Night	16% 9% 3 5% 4 4 4 3 4 6% 42%	2595
	11th to 20th	Night	18% 9% 2 5% 3 4 3 3 6% 5% 42%	2338
	21st to end	Night	18% 8% 3 7% 3 2 3 3 5% 5% 43%	1980
March	1st to 10th	Night	18% 10% 2 5% 3 3 3 2 4 5% 46%	5364
	11th to 20th	Night	12% 10% 3 6% 3 3 3 2 4 5% 47%	5081
	21st to end	Night	16% 8% 2 7% 3 4 4 3 5% 5% 42%	5059
April	1st to 10th	Night	17% 8% 3 7% 4 3 4 3 4 6% 41%	2000
	11th to 20th	Night	15% 8% 3 7% 4 4 4 3 4 7% 42%	1975
	21st to end	Night	17% 6% 2 5% 3 3 4 3 6% 8% 43%	2000
May	1st to 10th	Night	21% 10% 3 7% 5% 4 4 4 6% 8% 28%	4113
	11th to 20th	Night	23% 8% 3 7% 4 3 3 4 5% 7% 33%	3668
	21st to end	Night	20% 8% 2 6% 4 4 4 4 4 8% 36%	3926
June	1st to 10th	Night	14% 6% 2 6% 3 3 4 5% 6% 8% 42%	1600
	11th to 20th	Night	11% 8% 2 6% 6% 4 5% 4 5% 7% 42%	1600
	21st to end	Night	9% 5% 2 5% 5% 5% 5% 6% 8% 10% 40%	1600
July	1st to 10th	Night	8% 7% 3 8% 6% 6% 6% 5% 7% 10% 35%	3600
	11th to 20th	Night	11% 9% 3 8% 5% 5% 5% 4 7% 10% 33%	3600
	21st to end	Night	11% 7% 2 7% 4 4 5% 4 6% 9% 41%	3926
August	1st to 10th	Night	21% 7% 3 6% 4 4 5% 4 6% 8% 32%	2955
	11th to 20th	Night	12% 7% 2 7% 4 4 4 3 6% 7% 44%	3197
	21st to end	Night	9% 4 2 6% 4 4 4 4 6% 7% 51%	3586
September	1st to 10th	Night	14% 6% 2 6% 4 5% 4 3 4 6% 46%	2000
	11th to 20th	Night	11% 6% 2 4 3 3 4 3 5% 7% 52%	2065
	21st to end	Night	19% 8% 2 5% 4 3 4 3 6% 7% 39%	2200
October	1st to 10th	Night	17% 6% 3 5% 3 3 4 3 4 6% 46%	2336
	11th to 20th	Night	16% 5% 2 5% 3 3 3 2 4 6% 51%	2400
	21st to end	Night	17% 7% 2 5% 3 3 3 3 4 6% 48%	2750
November	1st to 10th	Night	11% 5% 2 6% 3 4 3 2 5% 7% 52%	2667
	11th to 20th	Night	16% 6% 2 6% 4 3 4 3 4 5% 48%	2730
	21st to end	Night	13% 6% 2 5% 5% 4 4 4 5% 7% 46%	2802
December	1st to 10th	Night	13% 7% 2 5% 3 4 3 3 5% 6% 49%	4720
	11th to 20th	Night	22% 7% 2 5% 3 3 3 2 4 6% 42%	5348
	21st to end	Night	17% 8% 3 5% 4 4 4 3 4 6% 42%	7150

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	34% 4 9% 26% 24% 3	3606
	11th to 20th	Day	41% 4 9% 23% 18% 6%	3615
	21st to end	Day	46% 5% 9% 24% 13% 2	4466
February	1st to 10th	Day	43% 5% 14% 24% 13% 1	1804
	11th to 20th	Day	44% 6% 10% 22% 16% 3	1957
	21st to end	Day	45% 5% 8% 22% 14% 5%	1650
March	1st to 10th	Day	40% 4 10% 23% 16% 8%	4479
	11th to 20th	Day	36% 5% 10% 27% 16% 5%	4875
	21st to end	Day	42% 5% 9% 16% 23% 6%	5872
April	1st to 10th	Day	43% 7% 10% 20% 15% 5%	2400
	11th to 20th	Day	39% 7% 14% 21% 16% 3	2374
	21st to end	Day	40% 7% 10% 19% 18% 4	2400
May	1st to 10th	Day	52% 8% 14% 17% 9% 1	5823
	11th to 20th	Day	50% 6% 10% 22% 11% 1	6271
	21st to end	Day	44% 8% 12% 21% 14% 1	6949
June	1st to 10th	Day	40% 9% 13% 21% 15% 2	2800
	11th to 20th	Day	40% 8% 13% 24% 12% 3	2800
	21st to end	Day	38% 10% 13% 22% 16% 2	2800
July	1st to 10th	Day	41% 10% 15% 20% 13% 1	6290
	11th to 20th	Day	45% 9% 18% 18% 9% 1	6285
	21st to end	Day	40% 8% 11% 21% 20% 1	6728
August	1st to 10th	Day	49% 8% 14% 20% 9% 1	4146
	11th to 20th	Day	41% 8% 13% 24% 13% 1	3886
	21st to end	Day	34% 7% 13% 26% 18% 2	4312
September	1st to 10th	Day	38% 7% 13% 19% 20% 3	2400
	11th to 20th	Day	34% 5% 11% 23% 23% 3	2334
	21st to end	Day	47% 6% 9% 17% 19% 3	2200
October	1st to 10th	Day	36% 4 10% 18% 27% 5%	3359
	11th to 20th	Day	25% 4 9% 23% 31% 8%	3240
	21st to end	Day	26% 4 12% 26% 27% 5%	3354
November	1st to 10th	Day	33% 4 13% 26% 20% 3	1851
	11th to 20th	Day	38% 4 10% 22% 23% 3	1890
	21st to end	Day	38% 5% 12% 30% 12% 2	1816
December	1st to 10th	Day	37% 4 16% 26% 15% 2	2680
	11th to 20th	Day	42% 4 10% 30% 11% 3	3066
	21st to end	Day	39% 7% 12% 22% 18% 2	4048
January	1st to 10th	Night	34% 4 9% 24% 22% 7%	6364
	11th to 20th	Night	38% 4 10% 24% 17% 7%	6342
	21st to end	Night	43% 4 9% 23% 18% 3	6490
February	1st to 10th	Night	43% 6% 13% 23% 13% 2	2595
	11th to 20th	Night	44% 4 9% 20% 18% 5%	2340
	21st to end	Night	42% 5% 8% 21% 18% 6%	1980
March	1st to 10th	Night	41% 4 9% 23% 13% 10%	5374
	11th to 20th	Night	38% 6% 13% 24% 14% 5%	5082
	21st to end	Night	43% 5% 7% 16% 24% 5%	5059
April	1st to 10th	Night	45% 5% 10% 18% 18% 5%	2000
	11th to 20th	Night	42% 5% 10% 20% 19% 4	1975
	21st to end	Night	38% 7% 10% 19% 21% 5%	2000
May	1st to 10th	Night	52% 8% 12% 17% 9% 3	4119
	11th to 20th	Night	50% 6% 12% 17% 14% 1	3669
	21st to end	Night	45% 8% 12% 20% 13% 1	3927
June	1st to 10th	Night	40% 9% 11% 21% 19% 2	1600
	11th to 20th	Night	40% 10% 13% 23% 13% 2	1600
	21st to end	Night	35% 9% 17% 21% 16% 2	1600
July	1st to 10th	Night	43% 9% 15% 20% 12% 1	3560
	11th to 20th	Night	45% 8% 18% 20% 8% 1	3552
	21st to end	Night	39% 6% 15% 22% 18% 1	3809
August	1st to 10th	Night	49% 8% 18% 15% 9% 1	2945
	11th to 20th	Night	39% 6% 13% 30% 11% 1	3227
	21st to end	Night	32% 6% 12% 28% 22% 2	3586
September	1st to 10th	Night	39% 8% 12% 19% 20% 3	2000
	11th to 20th	Night	32% 5% 12% 23% 24% 4	2065
	21st to end	Night	43% 7% 9% 21% 19% 2	2200
October	1st to 10th	Night	36% 5% 11% 23% 22% 3	3817
	11th to 20th	Night	25% 3 10% 26% 30% 6%	3899
	21st to end	Night	26% 4 10% 31% 24% 4	4436
November	1st to 10th	Night	32% 5% 12% 24% 22% 5%	2667
	11th to 20th	Night	39% 5% 8% 22% 21% 5%	2730
	21st to end	Night	37% 5% 12% 26% 18% 2	2802
December	1st to 10th	Night	37% 4 12% 30% 15% 3	4720
	11th to 20th	Night	43% 4 11% 23% 14% 4	5348
	21st to end	Night	43% 6% 11% 19% 18% 3	7150

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	24% 22% 35% 14% 4 1	202
	11th to 20th	Day	27% 28% 30% 13% 1	202
	21st to end	Day	25% 22% 32% 15% 5% 1	330
February	1st to 10th	Day	24% 22% 38% 12% 4	304
	11th to 20th	Day	31% 21% 34% 13% 2	496
	21st to end	Day	26% 22% 32% 17% 3	414
March	1st to 10th	Day	23% 23% 32% 18% 4 1	500
	11th to 20th	Day	17% 26% 36% 14% 5% 2	500
	21st to end	Day	23% 21% 33% 18% 5%	550
April	1st to 10th	Day	24% 21% 35% 14% 5% 1	500
	11th to 20th	Day	20% 18% 34% 19% 8% 1	492
	21st to end	Day	24% 17% 34% 18% 6% 2	500
May	1st to 10th	Day	28% 17% 29% 16% 9% 2	503
	11th to 20th	Day	23% 11% 36% 20% 7% 3	527
	21st to end	Day	21% 9% 22% 27% 18% 4	573
June	1st to 10th	Day	15% 10% 30% 26% 15% 3	530
	11th to 20th	Day	16% 10% 29% 28% 14% 3	530
	21st to end	Day	13% 6% 28% 30% 18% 4	530
July	1st to 10th	Day	14% 3 23% 30% 23% 8%	525
	11th to 20th	Day	8% 2 25% 34% 24% 7%	524
	21st to end	Day	11% 6% 25% 32% 21% 5%	576
August	1st to 10th	Day	12% 5% 25% 32% 19% 7%	526
	11th to 20th	Day	14% 3 21% 31% 23% 8%	519
	21st to end	Day	11% 5% 24% 30% 19% 10%	583
September	1st to 10th	Day	15% 8% 26% 25% 18% 9%	530
	11th to 20th	Day	13% 4 26% 31% 17% 9%	530
	21st to end	Day	24% 7% 26% 26% 13% 5%	530
October	1st to 10th	Day	22% 7% 26% 24% 14% 8%	530
	11th to 20th	Day	18% 14% 29% 23% 12% 4	530
	21st to end	Day	18% 13% 33% 22% 12% 2	522
November	1st to 10th	Day	15% 12% 35% 24% 12% 2	425
	11th to 20th	Day	20% 18% 30% 24% 7%	430
	21st to end	Day	19% 17% 33% 23% 8% 1	356
December	1st to 10th	Day	23% 21% 38% 11% 7%	220
	11th to 20th	Day	30% 16% 36% 14% 4	220
	21st to end	Day	26% 17% 32% 18% 5% 2	242
January	1st to 10th	Night	19% 18% 37% 21% 4	805
	11th to 20th	Night	23% 16% 34% 24% 3	800
	21st to end	Night	19% 15% 41% 23% 2	880
February	1st to 10th	Night	21% 14% 38% 25% 2	800
	11th to 20th	Night	25% 19% 38% 16% 1	783
	21st to end	Night	22% 19% 35% 20% 3	660
March	1st to 10th	Night	20% 16% 38% 22% 4	800
	11th to 20th	Night	20% 17% 37% 21% 6% 1	800
	21st to end	Night	21% 11% 42% 20% 5%	880
April	1st to 10th	Night	21% 18% 37% 18% 6%	800
	11th to 20th	Night	19% 13% 37% 27% 5%	791
	21st to end	Night	19% 10% 37% 28% 6%	800
May	1st to 10th	Night	20% 12% 35% 26% 7%	633
	11th to 20th	Night	21% 9% 35% 29% 4	435
	21st to end	Night	19% 4 21% 41% 13% 2	433
June	1st to 10th	Night	17% 4 28% 40% 11% 1	400
	11th to 20th	Night	14% 4 25% 43% 15%	400
	21st to end	Night	9% 5% 26% 45% 15% 1	400
July	1st to 10th	Night	11% 4 19% 45% 20% 1	390
	11th to 20th	Night	8% 4 19% 45% 21% 2	388
	21st to end	Night	9% 3 23% 47% 18% 1	438
August	1st to 10th	Night	12% 2 14% 48% 22% 2	611
	11th to 20th	Night	13% 3 17% 39% 26% 1	790
	21st to end	Night	13% 3 17% 40% 24% 3	880
September	1st to 10th	Night	17% 2 21% 39% 18% 3	800
	11th to 20th	Night	14% 4 18% 37% 23% 5%	800
	21st to end	Night	23% 4 22% 34% 16% 1	800
October	1st to 10th	Night	20% 5% 25% 28% 18% 4	800
	11th to 20th	Night	18% 9% 26% 34% 13% 1	800
	21st to end	Night	19% 9% 35% 28% 9% 1	880
November	1st to 10th	Night	15% 8% 35% 31% 11% 1	820
	11th to 20th	Night	19% 14% 32% 27% 8%	840
	21st to end	Night	15% 14% 35% 27% 8% 1	840
December	1st to 10th	Night	23% 13% 36% 21% 6% 1	840
	11th to 20th	Night	20% 14% 36% 25% 5%	840
	21st to end	Night	21% 13% 36% 28% 3	924

Page generated at 2025-12-30 01:14:04. Version ac07

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