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 2025-01-22.

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% 10% 3 8% 5% 5% 5% 4 6% 7% 33%	105364
	Night	15% 11% 4 8% 5% 4 4 4 5% 6% 34%	104013
Transparency	Day	50% 4 11% 22% 12% 1	109007
	Night	50% 3 11% 22% 13% 2	108496
Seeing	Day	18% 10% 27% 24% 15% 6%	15785
	Night	19% 9% 28% 29% 13% 1	25669

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% 7% 13% 6% 5% 4 3 4 5% 18%	2607
	11th to 20th	Day	15% 21% 7% 11% 7% 7% 8% 4 4 4 13%	2684
	21st to end	Day	27% 20% 9% 12% 4 4 4 2 3 3 11%	3133
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	11% 5% 2 6% 4 4 6% 5% 7% 9% 42%	4104
	11th to 20th	Day	9% 5% 2 6% 5% 5% 7% 6% 8% 10% 38%	4044
	21st to end	Day	8% 5% 2 6% 5% 5% 6% 4 7% 10% 42%	4438
September	1st to 10th	Day	13% 6% 2 6% 5% 3 5% 4 5% 8% 44%	2140
	11th to 20th	Day	9% 6% 2 5% 4 4 5% 4 5% 9% 47%	2090
	21st to end	Day	17% 7% 3 6% 3 4 5% 3 5% 7% 41%	2090
October	1st to 10th	Day	12% 7% 2 6% 4 5% 5% 3 6% 8% 43%	2051
	11th to 20th	Day	17% 8% 2 7% 5% 4 4 3 5% 6% 38%	1900
	21st to end	Day	18% 9% 3 7% 6% 4 5% 4 6% 7% 31%	1957
November	1st to 10th	Day	11% 10% 3 6% 5% 4 4 4 6% 6% 42%	1762
	11th to 20th	Day	17% 13% 3 8% 5% 4 4 3 4 6% 33%	1800
	21st to end	Day	18% 14% 4 9% 5% 4 4 3 5% 7% 27%	1800
December	1st to 10th	Day	14% 15% 7% 11% 6% 5% 5% 4 4 6% 23%	2930
	11th to 20th	Day	19% 17% 7% 10% 5% 5% 4 3 4 5% 21%	3351
	21st to end	Day	26% 20% 6% 12% 5% 4 3 2 3 4 14%	3982
January	1st to 10th	Night	16% 17% 7% 11% 5% 5% 4 3 5% 5% 22%	4568
	11th to 20th	Night	16% 18% 8% 13% 5% 5% 6% 5% 4 5% 15%	4500
	21st to end	Night	27% 17% 8% 12% 4 4 3 2 3 4 15%	4546
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	13% 5% 2 7% 4 4 4 4 5% 8% 44%	2825
	11th to 20th	Night	9% 5% 2 5% 4 4 5% 5% 5% 8% 47%	2785
	21st to end	Night	8% 4 2 6% 5% 4 5% 4 6% 7% 48%	3214
September	1st to 10th	Night	11% 6% 2 5% 4 3 4 3 6% 6% 50%	2019
	11th to 20th	Night	9% 5% 2 5% 4 4 3 3 4 7% 55%	2090
	21st to end	Night	14% 6% 3 6% 4 4 4 3 5% 6% 44%	2090
October	1st to 10th	Night	12% 5% 2 6% 4 4 4 4 5% 7% 48%	2128
	11th to 20th	Night	17% 8% 3 7% 4 4 4 3 5% 6% 39%	2280
	21st to end	Night	20% 8% 3 7% 4 4 4 3 5% 7% 36%	2639
November	1st to 10th	Night	13% 8% 3 6% 4 4 4 3 5% 6% 43%	2536
	11th to 20th	Night	16% 11% 3 8% 5% 4 4 4 5% 6% 33%	2600
	21st to end	Night	19% 14% 3 8% 5% 5% 4 4 5% 6% 27%	2600
December	1st to 10th	Night	13% 12% 6% 11% 6% 5% 5% 4 5% 7% 26%	4250
	11th to 20th	Night	16% 18% 7% 11% 5% 4 4 4 4 5% 23%	4840
	21st to end	Night	26% 18% 6% 10% 5% 4 4 3 4 5% 14%	6996

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	2608
	11th to 20th	Day	77% 3 8% 8% 5%	2684
	21st to end	Day	80% 2 7% 7% 3	3133
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	38% 5% 13% 28% 16% 1	4091
	11th to 20th	Day	39% 5% 11% 31% 13% 1	4083
	21st to end	Day	37% 3 11% 33% 13% 2	4437
September	1st to 10th	Day	39% 5% 12% 24% 17% 3	2140
	11th to 20th	Day	34% 4 11% 29% 20% 2	2090
	21st to end	Day	43% 4 11% 24% 17% 1	2090
October	1st to 10th	Day	30% 3 12% 34% 20% 1	3402
	11th to 20th	Day	41% 2 9% 28% 20% 1	3140
	21st to end	Day	42% 3 11% 25% 18% 1	3207
November	1st to 10th	Day	42% 4 11% 26% 16% 1	1762
	11th to 20th	Day	53% 4 10% 19% 12% 1	1800
	21st to end	Day	57% 4 11% 20% 8%	1800
December	1st to 10th	Day	64% 2 15% 15% 3	2930
	11th to 20th	Day	67% 2 10% 16% 5%	3348
	21st to end	Day	77% 2 7% 9% 4	3982
January	1st to 10th	Night	66% 3 8% 16% 6%	4568
	11th to 20th	Night	73% 3 10% 11% 4	4500
	21st to end	Night	75% 2 9% 9% 4	4546
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	40% 4 11% 27% 15% 2	2814
	11th to 20th	Night	35% 4 12% 30% 18% 1	2812
	21st to end	Night	35% 4 12% 30% 17% 2	3214
September	1st to 10th	Night	35% 5% 12% 26% 18% 5%	2019
	11th to 20th	Night	30% 4 9% 28% 26% 2	2090
	21st to end	Night	41% 5% 10% 24% 19% 2	2090
October	1st to 10th	Night	26% 2 8% 31% 32% 1	3544
	11th to 20th	Night	38% 2 9% 29% 21% 1	3779
	21st to end	Night	38% 2 8% 34% 16% 3	4339
November	1st to 10th	Night	42% 3 11% 25% 17% 2	2536
	11th to 20th	Night	50% 4 11% 22% 11% 2	2600
	21st to end	Night	59% 3 12% 19% 6%	2600
December	1st to 10th	Night	59% 3 12% 19% 6% 1	4250
	11th to 20th	Night	65% 3 11% 13% 7% 1	4842
	21st to end	Night	74% 3 10% 9% 5%	6996

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	22% 21% 31% 20% 6% 1	300
	11th to 20th	Day	22% 19% 40% 13% 5% 1	300
	21st to end	Day	28% 14% 32% 21% 4 1	300
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% 24% 13%	479
	21st to end	Day	10% 2 17% 28% 28% 15%	539
September	1st to 10th	Day	16% 4 16% 28% 25% 12%	490
	11th to 20th	Day	9% 3 14% 26% 30% 18%	490
	21st to end	Day	21% 7% 22% 23% 17% 10%	490
October	1st to 10th	Day	13% 7% 24% 28% 20% 8%	490
	11th to 20th	Day	18% 15% 30% 24% 10% 3	490
	21st to end	Day	24% 11% 35% 23% 7% 1	406
November	1st to 10th	Day	14% 15% 33% 23% 12% 4	300
	11th to 20th	Day	26% 16% 30% 19% 8% 1	300
	21st to end	Day	26% 13% 37% 23% 2	300
December	1st to 10th	Day	22% 18% 33% 18% 8%	300
	11th to 20th	Day	21% 21% 34% 19% 5%	300
	21st to end	Day	28% 17% 32% 19% 4	330
January	1st to 10th	Night	24% 14% 35% 21% 6%	1000
	11th to 20th	Night	27% 14% 36% 18% 4 1	946
	21st to end	Night	24% 13% 35% 23% 5%	841
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	10% 1 15% 37% 33% 4	564
	21st to end	Night	9% 2 13% 38% 35% 4	627
September	1st to 10th	Night	14% 5% 14% 34% 28% 5%	689
	11th to 20th	Night	11% 3 14% 34% 34% 4	760
	21st to end	Night	17% 5% 21% 32% 22% 3	760
October	1st to 10th	Night	14% 6% 24% 32% 21% 2	760
	11th to 20th	Night	20% 12% 29% 28% 10% 2	760
	21st to end	Night	23% 12% 29% 27% 8%	836
November	1st to 10th	Night	16% 11% 32% 28% 11% 2	780
	11th to 20th	Night	23% 14% 31% 23% 8% 1	800
	21st to end	Night	26% 12% 32% 23% 6% 1	800
December	1st to 10th	Night	24% 14% 34% 22% 5%	800
	11th to 20th	Night	26% 12% 35% 23% 4	805
	21st to end	Night	30% 13% 32% 22% 3	1100

Page generated at 2025-01-19 03:06:43. Version ac07

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