Lone Palm Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lone Palm Observatory clear sky chart from 2005-11-06 to 2025-11-18.

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	7% 5% 2 7% 5% 6% 6% 5% 8% 10% 38%	126404
	Night	8% 6% 2 7% 5% 5% 5% 4 7% 9% 42%	123981
Transparency	Day	35% 11% 18% 20% 12% 3	130073
	Night	35% 10% 18% 20% 12% 4	128368
Seeing	Day	8% 5% 19% 28% 24% 17%	17185
	Night	8% 4 18% 31% 29% 9%	27253

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	8% 5% 2 6% 4 4 4 3 5% 7% 52%	4056
	11th to 20th	Day	17% 9% 4 9% 5% 5% 4 3 6% 8% 30%	4060
	21st to end	Day	16% 6% 2 7% 3 5% 4 4 6% 8% 40%	4466
February	1st to 10th	Day	10% 7% 2 6% 5% 4 5% 4 6% 8% 43%	1991
	11th to 20th	Day	6% 4 2 6% 5% 5% 4 3 6% 7% 51%	1975
	21st to end	Day	9% 5% 2 5% 4 5% 5% 4 6% 7% 48%	1815
March	1st to 10th	Day	6% 5% 3 8% 5% 5% 5% 4 7% 9% 42%	4935
	11th to 20th	Day	3 2 1 4 3 3 4 3 6% 9% 61%	4980
	21st to end	Day	8% 5% 2 6% 5% 5% 6% 4 7% 9% 43%	5465
April	1st to 10th	Day	5% 4 1 5% 4 4 5% 5% 7% 10% 49%	2200
	11th to 20th	Day	7% 4 2 6% 5% 5% 5% 5% 8% 8% 43%	2274
	21st to end	Day	5% 3 2 6% 5% 5% 5% 4 7% 9% 49%	2400
May	1st to 10th	Day	3 2 1 4 4 5% 6% 5% 8% 12% 50%	5445
	11th to 20th	Day	7% 5% 3 6% 5% 5% 5% 4 7% 9% 44%	5861
	21st to end	Day	4 4 2 5% 5% 6% 6% 6% 8% 10% 44%	6433
June	1st to 10th	Day	12% 7% 3 8% 6% 7% 8% 6% 8% 11% 24%	2600
	11th to 20th	Day	6% 5% 2 8% 7% 7% 9% 7% 10% 11% 27%	2600
	21st to end	Day	8% 6% 3 8% 7% 8% 8% 6% 10% 11% 25%	2600
July	1st to 10th	Day	6% 6% 3 8% 6% 7% 8% 6% 10% 14% 25%	5900
	11th to 20th	Day	5% 5% 2 7% 6% 6% 7% 6% 10% 14% 33%	5900
	21st to end	Day	4 4 2 7% 6% 6% 7% 6% 9% 14% 34%	6424
August	1st to 10th	Day	4 4 2 9% 6% 8% 9% 7% 11% 15% 26%	4234
	11th to 20th	Day	4 4 2 7% 6% 6% 8% 7% 10% 14% 33%	3944
	21st to end	Day	7% 5% 2 8% 7% 7% 8% 7% 11% 14% 24%	4033
September	1st to 10th	Day	7% 7% 3 9% 9% 7% 10% 7% 9% 11% 22%	2200
	11th to 20th	Day	9% 7% 3 9% 7% 7% 7% 7% 9% 11% 24%	2200
	21st to end	Day	9% 7% 3 9% 7% 8% 8% 6% 9% 9% 25%	2200
October	1st to 10th	Day	11% 6% 3 9% 6% 7% 6% 6% 8% 10% 28%	2117
	11th to 20th	Day	7% 5% 3 6% 6% 5% 6% 5% 8% 9% 42%	2000
	21st to end	Day	9% 4 2 6% 5% 5% 5% 3 7% 10% 45%	2200
November	1st to 10th	Day	8% 5% 3 6% 6% 5% 5% 5% 8% 9% 39%	2057
	11th to 20th	Day	9% 6% 3 6% 5% 5% 5% 5% 7% 8% 40%	2070
	21st to end	Day	9% 6% 2 7% 5% 5% 5% 5% 6% 9% 41%	2000
December	1st to 10th	Day	5% 4 2 5% 3 4 4 4 5% 8% 55%	2930
	11th to 20th	Day	9% 7% 2 7% 5% 6% 6% 5% 7% 11% 34%	3373
	21st to end	Day	10% 6% 3 8% 6% 7% 7% 5% 7% 8% 33%	4466
January	1st to 10th	Night	8% 5% 2 6% 4 3 4 4 6% 8% 52%	5889
	11th to 20th	Night	15% 11% 4 9% 5% 5% 4 4 6% 8% 30%	5900
	21st to end	Night	15% 7% 2 6% 4 4 4 4 6% 8% 42%	6490
February	1st to 10th	Night	10% 6% 3 6% 4 4 4 3 5% 8% 46%	2405
	11th to 20th	Night	10% 4 2 5% 4 3 4 4 6% 7% 51%	2308
	21st to end	Night	7% 5% 2 4 3 3 4 4 7% 7% 54%	1815
March	1st to 10th	Night	8% 6% 2 7% 5% 4 5% 4 6% 7% 46%	4918
	11th to 20th	Night	5% 3 1 4 3 2 3 4 6% 10% 59%	4980
	21st to end	Night	7% 5% 2 6% 5% 5% 5% 4 7% 8% 47%	5467
April	1st to 10th	Night	6% 3 2 5% 3 3 5% 4 7% 9% 55%	2200
	11th to 20th	Night	5% 4 3 6% 4 4 4 5% 7% 9% 50%	2074
	21st to end	Night	5% 3 2 5% 4 4 5% 4 6% 8% 54%	2000
May	1st to 10th	Night	3 3 1 4 4 4 5% 4 7% 11% 53%	4490
	11th to 20th	Night	8% 5% 2 6% 4 5% 4 4 7% 9% 46%	4032
	21st to end	Night	5% 5% 2 6% 4 5% 5% 5% 8% 10% 46%	4421
June	1st to 10th	Night	10% 8% 3 8% 6% 6% 7% 7% 8% 10% 29%	1800
	11th to 20th	Night	6% 6% 2 8% 5% 6% 7% 6% 9% 14% 31%	1800
	21st to end	Night	6% 6% 2 9% 7% 5% 7% 5% 8% 12% 34%	1800
July	1st to 10th	Night	9% 8% 3 8% 6% 6% 6% 5% 8% 12% 28%	4058
	11th to 20th	Night	4 4 2 7% 5% 5% 6% 5% 9% 14% 40%	4057
	21st to end	Night	3 4 2 7% 6% 6% 6% 5% 8% 12% 40%	4427
August	1st to 10th	Night	4 5% 2 9% 6% 6% 8% 5% 9% 12% 35%	2915
	11th to 20th	Night	4 5% 2 7% 6% 6% 7% 6% 9% 12% 37%	3067
	21st to end	Night	6% 6% 3 7% 6% 6% 7% 7% 9% 15% 29%	3845
September	1st to 10th	Night	7% 7% 3 9% 7% 6% 8% 6% 8% 12% 27%	2200
	11th to 20th	Night	8% 8% 4 10% 7% 7% 6% 6% 8% 11% 27%	2200
	21st to end	Night	10% 7% 3 9% 6% 7% 5% 6% 8% 9% 31%	2200
October	1st to 10th	Night	12% 6% 3 8% 4 5% 5% 4 7% 10% 34%	2280
	11th to 20th	Night	7% 6% 2 7% 5% 5% 5% 4 6% 9% 45%	2400
	21st to end	Night	8% 6% 2 6% 4 4 4 4 6% 8% 47%	2640
November	1st to 10th	Night	8% 5% 3 7% 5% 5% 5% 4 6% 7% 44%	2461
	11th to 20th	Night	8% 6% 2 7% 5% 6% 4 4 6% 9% 44%	2485
	21st to end	Night	10% 6% 2 7% 5% 5% 5% 4 7% 8% 41%	2400
December	1st to 10th	Night	4 3 1 4 4 4 4 4 6% 9% 57%	4245
	11th to 20th	Night	12% 8% 3 7% 4 5% 5% 4 6% 8% 38%	4822
	21st to end	Night	10% 8% 3 9% 6% 5% 5% 4 6% 7% 37%	6490

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	31% 5% 10% 20% 27% 7%	4057
	11th to 20th	Day	52% 6% 7% 18% 14% 3	4060
	21st to end	Day	41% 6% 7% 24% 16% 5%	4466
February	1st to 10th	Day	37% 6% 11% 17% 22% 7%	1991
	11th to 20th	Day	29% 6% 12% 24% 21% 8%	1985
	21st to end	Day	32% 5% 13% 17% 25% 7%	1815
March	1st to 10th	Day	35% 9% 13% 17% 21% 5%	4935
	11th to 20th	Day	20% 5% 12% 29% 19% 15%	4980
	21st to end	Day	32% 8% 11% 27% 15% 6%	5465
April	1st to 10th	Day	27% 9% 15% 26% 17% 5%	2200
	11th to 20th	Day	34% 9% 12% 19% 20% 6%	2274
	21st to end	Day	27% 7% 14% 23% 24% 5%	2400
May	1st to 10th	Day	20% 11% 21% 29% 15% 3	5477
	11th to 20th	Day	33% 9% 19% 26% 12%	5865
	21st to end	Day	28% 12% 18% 30% 11%	6447
June	1st to 10th	Day	48% 12% 20% 15% 4	2600
	11th to 20th	Day	41% 14% 22% 20% 2	2600
	21st to end	Day	44% 16% 25% 13% 3	2600
July	1st to 10th	Day	40% 17% 31% 11% 3	5835
	11th to 20th	Day	32% 16% 38% 12% 1	5831
	21st to end	Day	32% 17% 27% 23% 1	6240
August	1st to 10th	Day	36% 20% 32% 11% 1	4221
	11th to 20th	Day	30% 18% 30% 14% 8%	3983
	21st to end	Day	40% 18% 30% 11% 2	4033
September	1st to 10th	Day	45% 20% 21% 10% 3	2200
	11th to 20th	Day	45% 17% 22% 13% 3	2200
	21st to end	Day	47% 15% 15% 13% 9% 1	2200
October	1st to 10th	Day	50% 12% 18% 11% 6% 2	3442
	11th to 20th	Day	30% 9% 10% 23% 25% 4	3240
	21st to end	Day	28% 6% 11% 25% 25% 5%	3538
November	1st to 10th	Day	34% 9% 16% 17% 18% 7%	2057
	11th to 20th	Day	37% 8% 10% 21% 16% 7%	2070
	21st to end	Day	38% 8% 12% 19% 18% 7%	2000
December	1st to 10th	Day	26% 7% 18% 28% 14% 7%	2930
	11th to 20th	Day	39% 9% 13% 16% 17% 5%	3370
	21st to end	Day	43% 9% 13% 19% 12% 4	4466
January	1st to 10th	Night	30% 6% 10% 23% 23% 9%	5889
	11th to 20th	Night	51% 6% 11% 18% 11% 3	5900
	21st to end	Night	40% 6% 9% 23% 15% 6%	6490
February	1st to 10th	Night	36% 6% 13% 18% 19% 9%	2405
	11th to 20th	Night	31% 5% 12% 23% 20% 9%	2309
	21st to end	Night	27% 7% 15% 21% 24% 7%	1815
March	1st to 10th	Night	35% 8% 12% 21% 18% 6%	4918
	11th to 20th	Night	19% 7% 19% 25% 18% 12%	4980
	21st to end	Night	32% 7% 13% 25% 18% 4	5467
April	1st to 10th	Night	24% 7% 19% 27% 17% 7%	2200
	11th to 20th	Night	29% 9% 14% 22% 21% 5%	2074
	21st to end	Night	27% 6% 15% 23% 22% 6%	2000
May	1st to 10th	Night	22% 11% 23% 29% 13% 3	4520
	11th to 20th	Night	31% 9% 21% 30% 8% 1	4033
	21st to end	Night	29% 10% 21% 29% 10%	4429
June	1st to 10th	Night	45% 12% 23% 16% 4	1800
	11th to 20th	Night	40% 13% 21% 22% 3	1800
	21st to end	Night	41% 14% 25% 17% 4	1800
July	1st to 10th	Night	44% 15% 25% 14% 1	4015
	11th to 20th	Night	30% 16% 42% 11%	4006
	21st to end	Night	32% 15% 29% 22% 1	4297
August	1st to 10th	Night	38% 15% 34% 12% 1	2904
	11th to 20th	Night	33% 16% 29% 15% 7%	3094
	21st to end	Night	41% 16% 32% 10% 1	3845
September	1st to 10th	Night	45% 19% 20% 13% 2	2200
	11th to 20th	Night	48% 16% 20% 14% 2	2200
	21st to end	Night	47% 13% 16% 15% 8% 1	2200
October	1st to 10th	Night	55% 11% 14% 12% 6% 2	3722
	11th to 20th	Night	33% 8% 11% 24% 21% 4	3899
	21st to end	Night	30% 7% 12% 22% 23% 6%	4252
November	1st to 10th	Night	37% 8% 13% 16% 19% 7%	2461
	11th to 20th	Night	35% 8% 12% 22% 15% 7%	2485
	21st to end	Night	38% 8% 12% 18% 19% 5%	2400
December	1st to 10th	Night	24% 7% 18% 32% 11% 9%	4245
	11th to 20th	Night	41% 8% 15% 15% 13% 8%	4824
	21st to end	Night	43% 8% 14% 19% 11% 5%	6490

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	11% 9% 44% 23% 11% 2	300
	11th to 20th	Day	7% 12% 40% 24% 13% 3	300
	21st to end	Day	14% 12% 45% 22% 6%	330
February	1st to 10th	Day	11% 10% 32% 29% 15% 4	300
	11th to 20th	Day	7% 9% 33% 35% 12% 4	327
	21st to end	Day	8% 7% 29% 36% 18% 3	414
March	1st to 10th	Day	6% 11% 34% 35% 12% 2	500
	11th to 20th	Day	8% 8% 31% 32% 18% 3	500
	21st to end	Day	6% 6% 30% 34% 21% 4	550
April	1st to 10th	Day	6% 6% 34% 34% 16% 4	500
	11th to 20th	Day	6% 9% 28% 33% 20% 5%	492
	21st to end	Day	5% 4 22% 35% 24% 9%	500
May	1st to 10th	Day	5% 3 21% 37% 25% 10%	503
	11th to 20th	Day	10% 4 16% 30% 26% 15%	527
	21st to end	Day	7% 3 12% 26% 32% 21%	573
June	1st to 10th	Day	13% 2 9% 28% 29% 19%	530
	11th to 20th	Day	6% 1 7% 24% 30% 32%	530
	21st to end	Day	5% 2 5% 18% 29% 41%	530
July	1st to 10th	Day	6% 2 4 12% 31% 45%	525
	11th to 20th	Day	6% 1 3 13% 35% 43%	524
	21st to end	Day	6% 1 5% 20% 28% 40%	576
August	1st to 10th	Day	4 2 5% 17% 32% 40%	526
	11th to 20th	Day	3 1 3 15% 32% 46%	519
	21st to end	Day	10% 2 5% 22% 29% 33%	583
September	1st to 10th	Day	8% 3 4 20% 29% 36%	530
	11th to 20th	Day	10% 1 8% 28% 27% 26%	530
	21st to end	Day	9% 2 9% 25% 33% 23%	530
October	1st to 10th	Day	15% 2 16% 35% 23% 9%	530
	11th to 20th	Day	7% 2 19% 36% 29% 8%	530
	21st to end	Day	7% 4 22% 36% 24% 7%	583
November	1st to 10th	Day	9% 8% 19% 36% 21% 7%	535
	11th to 20th	Day	10% 6% 25% 34% 22% 4	528
	21st to end	Day	8% 5% 25% 38% 21% 3	500
December	1st to 10th	Day	5% 8% 31% 38% 15% 4	300
	11th to 20th	Day	8% 9% 28% 36% 15% 3	300
	21st to end	Day	8% 8% 28% 37% 16% 2	330
January	1st to 10th	Night	12% 8% 29% 35% 15% 2	800
	11th to 20th	Night	11% 7% 29% 36% 15% 2	800
	21st to end	Night	13% 8% 33% 36% 11%	880
February	1st to 10th	Night	11% 8% 24% 40% 17% 1	800
	11th to 20th	Night	11% 7% 30% 36% 15% 2	783
	21st to end	Night	9% 4 29% 43% 15%	660
March	1st to 10th	Night	5% 7% 34% 41% 13% 1	800
	11th to 20th	Night	6% 6% 27% 40% 19% 2	800
	21st to end	Night	6% 5% 29% 40% 19% 1	880
April	1st to 10th	Night	5% 6% 28% 41% 19% 1	800
	11th to 20th	Night	6% 5% 24% 42% 22% 1	791
	21st to end	Night	6% 2 22% 44% 23% 3	800
May	1st to 10th	Night	6% 2 16% 48% 26% 2	800
	11th to 20th	Night	9% 2 13% 35% 36% 6%	591
	21st to end	Night	7% 1 7% 29% 46% 9%	650
June	1st to 10th	Night	11% 1 7% 27% 44% 9%	600
	11th to 20th	Night	7% 1 6% 19% 46% 22%	600
	21st to end	Night	5% 1 4 15% 47% 28%	600
July	1st to 10th	Night	8% 3 2 12% 49% 26%	585
	11th to 20th	Night	7% 1 2 10% 45% 34%	582
	21st to end	Night	5% 1 2 10% 50% 32%	657
August	1st to 10th	Night	5% 3 12% 49% 32%	597
	11th to 20th	Night	4 1 3 10% 48% 34%	708
	21st to end	Night	11% 2 5% 18% 41% 23%	880
September	1st to 10th	Night	7% 3 6% 18% 45% 22%	800
	11th to 20th	Night	12% 2 6% 23% 42% 17%	800
	21st to end	Night	12% 3 6% 22% 41% 16%	800
October	1st to 10th	Night	15% 1 13% 32% 33% 6%	800
	11th to 20th	Night	8% 4 12% 32% 38% 7%	800
	21st to end	Night	10% 2 20% 33% 30% 5%	880
November	1st to 10th	Night	10% 3 21% 34% 28% 5%	820
	11th to 20th	Night	8% 5% 24% 38% 23% 3	829
	21st to end	Night	11% 4 23% 41% 20% 2	800
December	1st to 10th	Night	5% 4 24% 38% 27% 3	800
	11th to 20th	Night	10% 6% 24% 35% 23% 3	800
	21st to end	Night	10% 5% 25% 37% 20% 2	880

Page generated at 2025-11-15 00:55:58. Version ac07

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