Luckey
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Luckey clear sky chart from 2005-11-06 to 2024-08-15.

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% 10% 3 8% 5% 5% 5% 4 5% 7% 33%	95404
	Night	15% 10% 4 8% 5% 4 4 4 5% 6% 34%	93298
Transparency	Day	50% 4 11% 21% 12% 2	95168
	Night	50% 4 11% 21% 12% 2	93139
Seeing	Day	18% 10% 27% 24% 14% 6%	15235
	Night	19% 9% 28% 29% 13% 1	25022

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	18% 19% 6% 12% 6% 5% 4 3 4 5% 18%	2527
	11th to 20th	Day	15% 21% 7% 11% 6% 7% 8% 4 4 4 12%	2601
	21st to end	Day	27% 20% 9% 12% 4 4 4 2 3 3 11%	3124
February	1st to 10th	Day	16% 16% 5% 11% 7% 6% 5% 4 5% 5% 21%	1710
	11th to 20th	Day	15% 12% 5% 12% 8% 6% 5% 4 5% 5% 24%	1824
	21st to end	Day	17% 13% 4 9% 6% 5% 4 3 5% 7% 26%	1570
March	1st to 10th	Day	21% 16% 4 10% 5% 4 3 3 5% 5% 24%	3204
	11th to 20th	Day	13% 11% 4 8% 5% 5% 5% 4 5% 6% 35%	3480
	21st to end	Day	20% 11% 5% 10% 5% 4 5% 3 5% 6% 26%	3815
April	1st to 10th	Day	13% 12% 4 8% 6% 5% 5% 5% 6% 7% 30%	2199
	11th to 20th	Day	17% 8% 3 6% 5% 5% 4 4 6% 7% 35%	2390
	21st to end	Day	19% 8% 3 7% 4 4 4 3 5% 6% 35%	2470
May	1st to 10th	Day	18% 9% 3 8% 5% 5% 5% 4 6% 7% 31%	4082
	11th to 20th	Day	17% 8% 2 7% 5% 5% 5% 4 6% 7% 35%	4081
	21st to end	Day	11% 5% 2 7% 5% 5% 5% 4 6% 8% 42%	4476
June	1st to 10th	Day	12% 6% 2 6% 5% 6% 6% 5% 6% 8% 39%	2566
	11th to 20th	Day	9% 6% 2 6% 5% 5% 4 4 6% 9% 43%	2660
	21st to end	Day	10% 6% 2 7% 6% 5% 5% 5% 7% 9% 37%	2660
July	1st to 10th	Day	11% 6% 3 7% 5% 5% 5% 4 7% 10% 38%	4440
	11th to 20th	Day	7% 4 2 6% 4 5% 6% 4 7% 10% 44%	4408
	21st to end	Day	7% 6% 2 7% 5% 5% 6% 5% 7% 9% 41%	4466
August	1st to 10th	Day	9% 4 1 6% 5% 4 6% 5% 7% 9% 44%	2457
	11th to 20th	Day	9% 5% 2 6% 5% 4 7% 5% 8% 11% 39%	2357
	21st to end	Day	10% 6% 2 5% 5% 4 5% 4 7% 9% 43%	2522
September	1st to 10th	Day	14% 6% 2 6% 5% 3 5% 4 5% 9% 42%	2028
	11th to 20th	Day	9% 6% 2 5% 4 4 5% 4 5% 9% 46%	1980
	21st to end	Day	16% 6% 2 6% 3 4 5% 3 5% 7% 43%	1980
October	1st to 10th	Day	13% 7% 2 6% 4 5% 5% 3 6% 7% 41%	1944
	11th to 20th	Day	18% 8% 2 7% 5% 4 4 3 5% 7% 37%	1800
	21st to end	Day	19% 9% 3 7% 6% 4 4 4 6% 7% 30%	1854
November	1st to 10th	Day	11% 10% 3 6% 5% 4 4 4 6% 7% 41%	1672
	11th to 20th	Day	16% 13% 3 8% 4 4 4 3 4 6% 34%	1710
	21st to end	Day	18% 14% 4 9% 5% 4 4 4 6% 6% 27%	1710
December	1st to 10th	Day	17% 18% 7% 11% 6% 5% 5% 3 3 5% 20%	1710
	11th to 20th	Day	14% 15% 6% 11% 6% 6% 5% 3 5% 6% 23%	2144
	21st to end	Day	23% 21% 7% 13% 5% 5% 3 3 3 4 12%	2783
January	1st to 10th	Night	16% 17% 7% 10% 5% 5% 4 3 5% 5% 22%	4428
	11th to 20th	Night	16% 18% 8% 13% 5% 5% 6% 5% 4 5% 14%	4363
	21st to end	Night	27% 18% 8% 12% 4 4 3 2 3 4 15%	4532
February	1st to 10th	Night	17% 15% 5% 10% 7% 5% 4 4 5% 5% 24%	2470
	11th to 20th	Night	14% 14% 4 9% 6% 6% 4 4 5% 6% 27%	2237
	21st to end	Night	20% 13% 5% 8% 5% 5% 4 2 5% 5% 28%	1884
March	1st to 10th	Night	19% 13% 4 7% 4 4 3 2 4 5% 35%	3648
	11th to 20th	Night	12% 8% 2 6% 5% 5% 5% 3 5% 7% 43%	3480
	21st to end	Night	17% 10% 4 8% 5% 4 4 3 4 6% 35%	3817
April	1st to 10th	Night	16% 11% 3 7% 5% 5% 4 4 5% 7% 34%	1995
	11th to 20th	Night	18% 8% 2 6% 5% 5% 4 4 5% 7% 37%	1739
	21st to end	Night	16% 8% 2 6% 5% 4 5% 4 5% 7% 38%	1710
May	1st to 10th	Night	19% 8% 3 8% 5% 4 5% 4 6% 7% 31%	2813
	11th to 20th	Night	18% 7% 3 7% 4 4 4 3 5% 7% 40%	2812
	21st to end	Night	10% 5% 2 6% 4 5% 4 4 6% 9% 47%	3079
June	1st to 10th	Night	11% 6% 2 6% 5% 4 5% 4 6% 7% 45%	1609
	11th to 20th	Night	10% 5% 2 6% 5% 4 4 4 8% 8% 44%	1520
	21st to end	Night	10% 5% 2 5% 4 4 4 5% 7% 9% 45%	1520
July	1st to 10th	Night	10% 4 1 5% 4 5% 4 4 5% 9% 48%	2530
	11th to 20th	Night	8% 3 2 4 4 4 5% 4 7% 9% 50%	2557
	21st to end	Night	7% 5% 2 6% 5% 4 6% 5% 7% 9% 45%	3087
August	1st to 10th	Night	7% 3 2 6% 4 4 4 4 7% 9% 50%	1701
	11th to 20th	Night	8% 5% 2 5% 5% 4 5% 5% 5% 9% 48%	1643
	21st to end	Night	8% 4 2 5% 5% 4 5% 3 6% 7% 50%	1830
September	1st to 10th	Night	11% 7% 2 5% 4 4 4 3 6% 7% 48%	1912
	11th to 20th	Night	9% 5% 2 5% 4 4 3 3 5% 7% 53%	1980
	21st to end	Night	13% 5% 2 6% 4 4 4 3 5% 6% 46%	1980
October	1st to 10th	Night	13% 6% 2 6% 4 4 4 4 5% 7% 46%	2016
	11th to 20th	Night	18% 8% 3 7% 4 4 4 3 5% 6% 38%	2160
	21st to end	Night	21% 8% 3 7% 4 4 4 3 4 6% 35%	2500
November	1st to 10th	Night	13% 9% 3 6% 4 4 5% 3 5% 6% 42%	2406
	11th to 20th	Night	16% 11% 3 8% 5% 4 4 4 5% 6% 33%	2470
	21st to end	Night	19% 14% 3 8% 5% 5% 4 3 5% 6% 27%	2470
December	1st to 10th	Night	17% 13% 5% 10% 6% 5% 4 3 5% 7% 23%	2470
	11th to 20th	Night	16% 16% 6% 9% 5% 4 4 4 5% 6% 26%	3046
	21st to end	Night	26% 19% 6% 10% 5% 4 4 3 4 5% 12%	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	70% 3 10% 12% 4	2528
	11th to 20th	Day	77% 3 8% 8% 4	2601
	21st to end	Day	81% 2 7% 7% 3	3124
February	1st to 10th	Day	65% 4 10% 14% 6%	1710
	11th to 20th	Day	60% 5% 9% 18% 7% 1	1834
	21st to end	Day	57% 4 15% 16% 7% 2	1570
March	1st to 10th	Day	64% 3 9% 18% 5%	3204
	11th to 20th	Day	50% 3 14% 24% 9% 1	3480
	21st to end	Day	59% 3 12% 18% 7%	3815
April	1st to 10th	Day	53% 5% 11% 18% 12% 1	2199
	11th to 20th	Day	48% 5% 12% 21% 13% 2	2390
	21st to end	Day	50% 5% 11% 22% 11% 2	2470
May	1st to 10th	Day	52% 4 10% 23% 10% 1	4120
	11th to 20th	Day	48% 4 12% 24% 10% 1	4085
	21st to end	Day	39% 4 11% 21% 20% 4	4489
June	1st to 10th	Day	41% 5% 11% 27% 13% 3	2566
	11th to 20th	Day	38% 5% 13% 23% 18% 3	2660
	21st to end	Day	41% 6% 13% 21% 15% 4	2660
July	1st to 10th	Day	43% 3 11% 23% 18% 3	4371
	11th to 20th	Day	34% 4 11% 30% 20% 2	4333
	21st to end	Day	40% 4 13% 18% 22% 3	4324
August	1st to 10th	Day	33% 7% 14% 30% 16%	2444
	11th to 20th	Day	37% 7% 14% 27% 13% 2	2357
	21st to end	Day	35% 6% 12% 25% 19% 3	2522
September	1st to 10th	Day	40% 5% 12% 23% 16% 3	2028
	11th to 20th	Day	35% 4 12% 29% 19% 1	1980
	21st to end	Day	41% 4 12% 25% 17% 1	1980
October	1st to 10th	Day	42% 5% 10% 27% 14% 2	1944
	11th to 20th	Day	47% 3 11% 23% 15% 1	1800
	21st to end	Day	52% 5% 12% 20% 11% 1	1854
November	1st to 10th	Day	42% 5% 11% 25% 17% 1	1672
	11th to 20th	Day	52% 4 11% 20% 12% 1	1710
	21st to end	Day	56% 4 12% 20% 8%	1710
December	1st to 10th	Day	69% 4 10% 14% 4	1710
	11th to 20th	Day	62% 4 12% 18% 5%	2141
	21st to end	Day	77% 3 8% 8% 3	2783
January	1st to 10th	Night	66% 3 9% 16% 6%	4428
	11th to 20th	Night	74% 3 9% 11% 3	4363
	21st to end	Night	75% 2 9% 10% 4	4532
February	1st to 10th	Night	61% 5% 11% 16% 5% 1	2470
	11th to 20th	Night	57% 4 9% 20% 8% 1	2238
	21st to end	Night	58% 4 11% 17% 9% 2	1884
March	1st to 10th	Night	54% 3 10% 25% 8% 1	3648
	11th to 20th	Night	40% 5% 14% 23% 17% 1	3480
	21st to end	Night	50% 4 10% 26% 9% 1	3817
April	1st to 10th	Night	49% 4 11% 20% 14% 2	1995
	11th to 20th	Night	47% 4 10% 20% 17% 2	1739
	21st to end	Night	46% 5% 10% 22% 15% 3	1710
May	1st to 10th	Night	53% 4 9% 19% 13% 2	2840
	11th to 20th	Night	45% 4 11% 27% 12% 1	2813
	21st to end	Night	34% 5% 10% 28% 20% 3	3087
June	1st to 10th	Night	38% 4 11% 27% 17% 3	1609
	11th to 20th	Night	35% 6% 13% 27% 16% 3	1520
	21st to end	Night	33% 6% 14% 26% 18% 2	1520
July	1st to 10th	Night	34% 3 12% 26% 18% 6%	2490
	11th to 20th	Night	31% 3 16% 30% 19% 2	2509
	21st to end	Night	34% 4 16% 21% 19% 5%	2988
August	1st to 10th	Night	31% 5% 13% 32% 18% 1	1690
	11th to 20th	Night	32% 6% 14% 29% 16% 2	1643
	21st to end	Night	32% 6% 13% 24% 22% 3	1830
September	1st to 10th	Night	36% 5% 12% 25% 17% 5%	1912
	11th to 20th	Night	32% 4 10% 28% 25% 1	1980
	21st to end	Night	39% 5% 10% 24% 20% 2	1980
October	1st to 10th	Night	39% 4 11% 25% 20% 1	2016
	11th to 20th	Night	47% 4 10% 23% 16% 1	2160
	21st to end	Night	50% 4 9% 24% 11% 2	2500
November	1st to 10th	Night	42% 4 11% 25% 17% 2	2406
	11th to 20th	Night	50% 4 11% 22% 11% 1	2470
	21st to end	Night	58% 4 12% 19% 7%	2470
December	1st to 10th	Night	61% 4 12% 16% 7%	2470
	11th to 20th	Night	59% 5% 13% 16% 6% 1	3048
	21st to end	Night	75% 3 11% 8% 3	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	23% 21% 29% 20% 6% 1	270
	11th to 20th	Day	23% 18% 40% 13% 6% 1	270
	21st to end	Day	29% 13% 32% 21% 4 1	297
February	1st to 10th	Day	26% 16% 40% 13% 4 1	270
	11th to 20th	Day	22% 19% 37% 19% 3	270
	21st to end	Day	27% 18% 42% 10% 3	225
March	1st to 10th	Day	22% 17% 36% 19% 6% 1	315
	11th to 20th	Day	22% 13% 38% 20% 6% 2	460
	21st to end	Day	30% 14% 31% 18% 7%	506
April	1st to 10th	Day	20% 15% 32% 20% 12% 1	460
	11th to 20th	Day	21% 17% 30% 20% 8% 4	452
	21st to end	Day	24% 12% 31% 23% 8% 2	460
May	1st to 10th	Day	23% 9% 32% 20% 12% 3	463
	11th to 20th	Day	19% 11% 26% 23% 13% 7%	487
	21st to end	Day	14% 7% 24% 27% 18% 11%	529
June	1st to 10th	Day	12% 6% 27% 32% 17% 5%	586
	11th to 20th	Day	12% 7% 28% 28% 20% 5%	680
	21st to end	Day	13% 6% 28% 30% 17% 6%	680
July	1st to 10th	Day	10% 4 20% 33% 19% 14%	671
	11th to 20th	Day	9% 5% 23% 31% 21% 12%	649
	21st to end	Day	10% 4 20% 27% 27% 12%	532
August	1st to 10th	Day	12% 2 14% 29% 28% 15%	486
	11th to 20th	Day	13% 3 16% 31% 23% 14%	456
	21st to end	Day	11% 3 18% 26% 28% 15%	495
September	1st to 10th	Day	16% 4 15% 28% 25% 12%	450
	11th to 20th	Day	10% 3 14% 27% 30% 16%	450
	21st to end	Day	17% 8% 22% 24% 19% 10%	450
October	1st to 10th	Day	14% 7% 25% 26% 20% 9%	450
	11th to 20th	Day	18% 16% 30% 24% 9% 2	450
	21st to end	Day	25% 11% 35% 22% 5% 1	369
November	1st to 10th	Day	14% 14% 33% 23% 13% 4	270
	11th to 20th	Day	24% 16% 30% 20% 8% 1	270
	21st to end	Day	25% 13% 36% 24% 2	270
December	1st to 10th	Day	22% 19% 33% 18% 8%	270
	11th to 20th	Day	19% 21% 35% 20% 4	270
	21st to end	Day	27% 17% 33% 20% 4	297
January	1st to 10th	Night	24% 14% 35% 21% 6%	950
	11th to 20th	Night	28% 13% 35% 18% 5% 1	899
	21st to end	Night	24% 13% 35% 23% 5%	836
February	1st to 10th	Night	27% 12% 34% 24% 4	760
	11th to 20th	Night	22% 14% 35% 26% 3	743
	21st to end	Night	26% 16% 36% 19% 2	628
March	1st to 10th	Night	21% 11% 33% 28% 7%	760
	11th to 20th	Night	18% 14% 35% 25% 6% 1	760
	21st to end	Night	24% 11% 30% 27% 8%	836
April	1st to 10th	Night	20% 14% 35% 26% 4 1	665
	11th to 20th	Night	22% 10% 33% 27% 8% 1	563
	21st to end	Night	21% 8% 34% 28% 9% 1	570
May	1st to 10th	Night	20% 6% 29% 34% 9% 1	570
	11th to 20th	Night	20% 6% 27% 30% 15% 1	561
	21st to end	Night	11% 3 24% 39% 21% 2	617
June	1st to 10th	Night	13% 5% 22% 43% 18%	570
	11th to 20th	Night	12% 4 21% 45% 18% 1	570
	21st to end	Night	12% 1 24% 40% 21% 2	570
July	1st to 10th	Night	11% 1 16% 40% 28% 3	555
	11th to 20th	Night	9% 3 18% 40% 24% 5%	552
	21st to end	Night	8% 2 13% 42% 33% 2	624
August	1st to 10th	Night	9% 1 12% 42% 32% 4	567
	11th to 20th	Night	9% 1 15% 36% 34% 5%	549
	21st to end	Night	9% 2 13% 37% 34% 4	594
September	1st to 10th	Night	15% 5% 13% 34% 28% 6%	652
	11th to 20th	Night	11% 3 14% 34% 33% 4	720
	21st to end	Night	14% 5% 21% 33% 23% 3	720
October	1st to 10th	Night	15% 6% 23% 32% 21% 2	720
	11th to 20th	Night	20% 12% 29% 28% 9% 2	720
	21st to end	Night	25% 12% 29% 27% 7%	792
November	1st to 10th	Night	16% 11% 31% 29% 11% 2	740
	11th to 20th	Night	23% 15% 31% 23% 8% 1	760
	21st to end	Night	26% 12% 32% 24% 6% 1	760
December	1st to 10th	Night	24% 14% 34% 22% 5%	760
	11th to 20th	Night	26% 12% 35% 23% 4	764
	21st to end	Night	30% 13% 32% 22% 3	1045

Page generated at 2024-08-12 09:52:54. Version ac07

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