Lane
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lane clear sky chart from 2005-11-06 to 2024-11-28.

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	10% 7% 3 6% 4 4 4 4 5% 7% 45%	105242
	Night	9% 7% 3 7% 4 4 4 4 5% 7% 47%	102919
Transparency	Day	38% 6% 14% 26% 14% 2	104988
	Night	36% 6% 15% 25% 16% 2	102763
Seeing	Day	13% 10% 32% 30% 13% 2	16032
	Night	12% 9% 35% 34% 10% 1	25963

By Month

Percentage Cloud Cover SW (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	6% 12% 6% 12% 9% 6% 7% 4 4 4 29%	2538
	11th to 20th	Day	4 9% 5% 13% 7% 6% 8% 3 5% 8% 31%	2540
	21st to end	Day	6% 11% 6% 11% 7% 5% 5% 4 5% 6% 35%	2925
February	1st to 10th	Day	9% 13% 3 9% 6% 6% 6% 4 5% 7% 33%	1710
	11th to 20th	Day	8% 9% 4 10% 6% 5% 5% 3 6% 7% 37%	1762
	21st to end	Day	8% 10% 4 8% 5% 5% 5% 5% 6% 7% 36%	1570
March	1st to 10th	Day	9% 11% 3 7% 4 4 3 3 4 7% 45%	3185
	11th to 20th	Day	8% 7% 3 6% 4 3 4 4 5% 8% 47%	3480
	21st to end	Day	22% 12% 3 11% 5% 4 4 3 5% 6% 25%	3814
April	1st to 10th	Day	15% 6% 2 5% 4 4 4 4 6% 8% 41%	2213
	11th to 20th	Day	18% 8% 3 7% 4 4 4 3 4 7% 38%	2425
	21st to end	Day	18% 9% 2 6% 5% 4 4 3 5% 6% 39%	2470
May	1st to 10th	Day	16% 6% 2 5% 5% 4 4 4 5% 7% 41%	4120
	11th to 20th	Day	11% 5% 2 6% 3 4 4 3 5% 7% 51%	4082
	21st to end	Day	16% 6% 2 5% 4 4 4 3 6% 7% 43%	4790
June	1st to 10th	Day	10% 6% 2 5% 4 4 4 4 5% 8% 48%	2850
	11th to 20th	Day	12% 4 2 5% 4 4 4 4 6% 7% 47%	2850
	21st to end	Day	8% 4 1 4 4 3 5% 4 6% 7% 52%	2850
July	1st to 10th	Day	11% 5% 2 5% 4 4 5% 4 6% 9% 46%	4530
	11th to 20th	Day	5% 3 1 4 3 4 4 3 6% 8% 60%	4430
	21st to end	Day	4 3 1 5% 4 4 5% 5% 7% 11% 53%	4683
August	1st to 10th	Day	8% 5% 2 6% 4 4 4 4 6% 9% 48%	4103
	11th to 20th	Day	16% 7% 3 5% 4 5% 5% 4 6% 8% 37%	4041
	21st to end	Day	6% 4 2 5% 4 3 4 3 5% 8% 55%	4532
September	1st to 10th	Day	10% 5% 1 4 3 3 3 3 4 7% 56%	2187
	11th to 20th	Day	9% 4 2 4 3 3 2 3 4 6% 59%	2090
	21st to end	Day	11% 4 2 5% 3 2 3 2 4 6% 58%	2090
October	1st to 10th	Day	8% 4 1 3 2 2 2 3 4 6% 65%	3362
	11th to 20th	Day	8% 5% 2 5% 4 3 4 3 4 6% 56%	3140
	21st to end	Day	11% 7% 2 6% 5% 4 5% 4 5% 7% 44%	3108
November	1st to 10th	Day	10% 7% 3 5% 4 4 5% 4 5% 7% 47%	1763
	11th to 20th	Day	6% 8% 2 8% 5% 3 4 4 5% 7% 48%	1766
	21st to end	Day	8% 8% 4 7% 5% 4 4 3 6% 6% 45%	1576
December	1st to 10th	Day	8% 9% 2 8% 6% 6% 5% 5% 5% 8% 37%	1478
	11th to 20th	Day	6% 10% 5% 9% 5% 6% 6% 3 6% 7% 37%	1683
	21st to end	Day	18% 11% 5% 11% 6% 3 4 3 4 5% 30%	2506
January	1st to 10th	Night	6% 11% 4 11% 9% 7% 6% 5% 6% 6% 29%	4417
	11th to 20th	Night	3 8% 4 10% 6% 6% 8% 4 9% 8% 33%	4430
	21st to end	Night	5% 9% 6% 13% 5% 4 4 4 6% 6% 38%	4740
February	1st to 10th	Night	8% 12% 4 8% 6% 5% 6% 4 5% 7% 36%	2470
	11th to 20th	Night	7% 9% 4 8% 5% 6% 5% 4 5% 6% 41%	2323
	21st to end	Night	8% 9% 2 7% 5% 4 5% 5% 6% 7% 42%	1884
March	1st to 10th	Night	8% 9% 3 7% 5% 4 4 3 4 6% 47%	3675
	11th to 20th	Night	9% 6% 2 5% 4 3 4 3 5% 8% 51%	3480
	21st to end	Night	20% 12% 3 7% 5% 4 5% 3 5% 5% 31%	3817
April	1st to 10th	Night	14% 7% 2 6% 4 4 4 3 6% 6% 42%	1965
	11th to 20th	Night	16% 8% 2 5% 4 3 3 4 6% 7% 42%	1702
	21st to end	Night	15% 8% 3 6% 4 4 4 4 5% 6% 42%	1710
May	1st to 10th	Night	14% 6% 1 6% 3 4 3 4 6% 8% 45%	2850
	11th to 20th	Night	10% 5% 1 4 3 2 3 3 5% 8% 56%	2823
	21st to end	Night	13% 5% 2 6% 4 3 4 4 5% 9% 45%	2779
June	1st to 10th	Night	8% 4 2 4 3 3 4 3 5% 8% 55%	1330
	11th to 20th	Night	9% 5% 2 4 5% 4 4 3 6% 9% 49%	1330
	21st to end	Night	6% 2 2 3 3 3 4 4 6% 9% 58%	1330
July	1st to 10th	Night	8% 5% 2 4 4 4 4 4 7% 10% 49%	2434
	11th to 20th	Night	2 2 1 4 4 3 3 3 5% 8% 65%	2540
	21st to end	Night	2 2 1 5% 4 4 4 4 7% 10% 58%	2877
August	1st to 10th	Night	9% 3 2 5% 4 4 4 4 7% 9% 49%	2836
	11th to 20th	Night	11% 6% 2 5% 3 4 4 3 5% 8% 50%	2798
	21st to end	Night	6% 3 2 5% 4 4 4 3 6% 8% 55%	3135
September	1st to 10th	Night	9% 4 1 3 3 3 4 3 3 5% 62%	1989
	11th to 20th	Night	7% 4 2 4 4 3 4 3 4 7% 60%	2090
	21st to end	Night	10% 4 2 4 4 3 3 2 3 5% 60%	2090
October	1st to 10th	Night	8% 3 1 3 3 2 2 2 4 5% 68%	3564
	11th to 20th	Night	8% 4 1 4 2 3 3 3 5% 7% 59%	3779
	21st to end	Night	9% 6% 2 6% 5% 4 4 4 5% 8% 48%	4436
November	1st to 10th	Night	7% 6% 2 5% 4 4 5% 4 6% 7% 51%	2535
	11th to 20th	Night	7% 7% 3 7% 5% 4 4 4 5% 6% 48%	2630
	21st to end	Night	7% 8% 2 5% 4 4 4 4 6% 8% 49%	2759
December	1st to 10th	Night	7% 8% 4 9% 6% 4 4 4 5% 7% 43%	2700
	11th to 20th	Night	7% 9% 3 7% 5% 4 4 3 5% 8% 45%	3514
	21st to end	Night	18% 12% 3 10% 4 3 4 3 4 6% 33%	5158

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	56% 6% 13% 17% 7%	2539
	11th to 20th	Day	52% 6% 14% 21% 7%	2540
	21st to end	Day	49% 9% 17% 18% 7%	2925
February	1st to 10th	Day	50% 9% 14% 16% 10%	1710
	11th to 20th	Day	47% 7% 15% 20% 11% 2	1771
	21st to end	Day	46% 8% 16% 18% 10% 2	1570
March	1st to 10th	Day	39% 7% 12% 25% 15% 1	3185
	11th to 20th	Day	34% 7% 11% 30% 15% 3	3480
	21st to end	Day	59% 9% 15% 14% 2 1	3814
April	1st to 10th	Day	41% 6% 15% 26% 12% 1	2213
	11th to 20th	Day	46% 7% 13% 21% 11% 3	2428
	21st to end	Day	44% 6% 13% 25% 11%	2470
May	1st to 10th	Day	40% 8% 11% 24% 17% 1	4120
	11th to 20th	Day	31% 8% 12% 27% 18% 3	4086
	21st to end	Day	38% 8% 14% 25% 14% 1	4790
June	1st to 10th	Day	33% 7% 16% 30% 11% 2	2850
	11th to 20th	Day	35% 8% 16% 24% 16% 2	2850
	21st to end	Day	28% 8% 16% 30% 14% 3	2850
July	1st to 10th	Day	35% 5% 19% 27% 13% 1	4461
	11th to 20th	Day	24% 4 13% 36% 20% 3	4355
	21st to end	Day	25% 6% 18% 29% 20% 3	4534
August	1st to 10th	Day	33% 5% 14% 30% 14% 3	4090
	11th to 20th	Day	45% 5% 15% 23% 10% 1	4080
	21st to end	Day	28% 5% 18% 29% 18% 2	4531
September	1st to 10th	Day	29% 5% 12% 31% 19% 3	2187
	11th to 20th	Day	27% 5% 15% 32% 18% 2	2090
	21st to end	Day	29% 5% 10% 32% 21% 3	2090
October	1st to 10th	Day	22% 4 9% 25% 36% 4	3362
	11th to 20th	Day	31% 4 12% 32% 19% 2	3140
	21st to end	Day	40% 3 14% 22% 19% 2	3108
November	1st to 10th	Day	35% 6% 17% 25% 13% 3	1763
	11th to 20th	Day	35% 6% 17% 26% 13% 2	1766
	21st to end	Day	39% 5% 17% 25% 13% 1	1576
December	1st to 10th	Day	43% 9% 16% 21% 9% 2	1478
	11th to 20th	Day	44% 8% 19% 23% 6% 1	1680
	21st to end	Day	56% 6% 11% 21% 5%	2506
January	1st to 10th	Night	53% 9% 13% 18% 7% 1	4417
	11th to 20th	Night	45% 8% 16% 22% 9% 1	4430
	21st to end	Night	45% 10% 18% 18% 9%	4740
February	1st to 10th	Night	47% 6% 15% 20% 11% 1	2470
	11th to 20th	Night	43% 6% 13% 22% 13% 3	2324
	21st to end	Night	38% 8% 16% 22% 12% 4	1884
March	1st to 10th	Night	38% 7% 13% 22% 19% 2	3675
	11th to 20th	Night	31% 6% 13% 32% 16% 2	3480
	21st to end	Night	53% 9% 14% 17% 7% 1	3817
April	1st to 10th	Night	40% 7% 14% 25% 13% 1	1965
	11th to 20th	Night	41% 7% 10% 22% 17% 3	1702
	21st to end	Night	42% 7% 12% 25% 13% 2	1710
May	1st to 10th	Night	34% 9% 15% 23% 14% 5%	2850
	11th to 20th	Night	26% 7% 12% 28% 24% 3	2824
	21st to end	Night	35% 10% 14% 27% 13% 1	2780
June	1st to 10th	Night	26% 7% 17% 27% 18% 4	1330
	11th to 20th	Night	31% 7% 16% 22% 21% 4	1330
	21st to end	Night	21% 7% 17% 32% 20% 3	1330
July	1st to 10th	Night	30% 5% 24% 23% 15% 3	2394
	11th to 20th	Night	19% 3 13% 37% 23% 4	2492
	21st to end	Night	21% 5% 19% 31% 21% 3	2787
August	1st to 10th	Night	31% 6% 18% 28% 14% 4	2826
	11th to 20th	Night	35% 5% 16% 30% 13% 1	2825
	21st to end	Night	28% 5% 17% 26% 20% 4	3135
September	1st to 10th	Night	25% 5% 12% 30% 22% 5%	1989
	11th to 20th	Night	24% 5% 16% 33% 19% 3	2090
	21st to end	Night	28% 4 8% 29% 27% 3	2090
October	1st to 10th	Night	21% 3 7% 21% 43% 6%	3564
	11th to 20th	Night	25% 3 10% 35% 22% 6%	3779
	21st to end	Night	36% 4 15% 24% 20% 2	4436
November	1st to 10th	Night	31% 7% 13% 25% 19% 5%	2535
	11th to 20th	Night	35% 7% 14% 24% 17% 3	2630
	21st to end	Night	34% 5% 18% 27% 16% 1	2759
December	1st to 10th	Night	42% 6% 17% 25% 10% 1	2700
	11th to 20th	Night	38% 6% 21% 27% 8%	3516
	21st to end	Night	53% 6% 12% 22% 7% 1	5158

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	15% 10% 30% 35% 9% 1	270
	11th to 20th	Day	12% 15% 35% 28% 9% 1	270
	21st to end	Day	15% 9% 38% 28% 9% 1	297
February	1st to 10th	Day	10% 14% 48% 25% 3	270
	11th to 20th	Day	14% 13% 40% 23% 9% 1	270
	21st to end	Day	15% 10% 42% 26% 6%	225
March	1st to 10th	Day	16% 14% 37% 27% 6%	270
	11th to 20th	Day	13% 9% 37% 27% 13% 1	270
	21st to end	Day	24% 12% 31% 21% 10% 3	297
April	1st to 10th	Day	22% 13% 37% 23% 5%	393
	11th to 20th	Day	22% 17% 32% 20% 8% 1	626
	21st to end	Day	20% 14% 29% 26% 8% 2	650
May	1st to 10th	Day	17% 13% 31% 29% 10% 1	653
	11th to 20th	Day	18% 9% 29% 26% 15% 2	675
	21st to end	Day	16% 9% 33% 27% 12% 3	734
June	1st to 10th	Day	10% 8% 26% 32% 19% 6%	680
	11th to 20th	Day	12% 9% 36% 27% 14% 2	680
	21st to end	Day	9% 8% 29% 38% 14% 1	680
July	1st to 10th	Day	8% 3 25% 39% 21% 5%	671
	11th to 20th	Day	6% 3 29% 41% 19% 2	668
	21st to end	Day	5% 3 24% 45% 20% 3	739
August	1st to 10th	Day	7% 4 24% 42% 22% 2	676
	11th to 20th	Day	11% 4 26% 38% 18% 3	665
	21st to end	Day	6% 5% 30% 34% 22% 3	748
September	1st to 10th	Day	11% 7% 31% 30% 17% 4	397
	11th to 20th	Day	9% 7% 34% 27% 19% 3	300
	21st to end	Day	14% 15% 30% 25% 12% 4	300
October	1st to 10th	Day	16% 8% 29% 29% 14% 5%	300
	11th to 20th	Day	16% 12% 37% 26% 9% 1	300
	21st to end	Day	16% 20% 33% 20% 10% 1	330
November	1st to 10th	Day	19% 11% 29% 31% 9% 1	300
	11th to 20th	Day	10% 19% 41% 23% 7% 1	300
	21st to end	Day	13% 15% 36% 29% 8%	291
December	1st to 10th	Day	11% 12% 39% 28% 8% 1	270
	11th to 20th	Day	12% 11% 43% 26% 7%	270
	21st to end	Day	21% 15% 31% 26% 6% 1	297
January	1st to 10th	Night	11% 10% 38% 32% 7% 1	950
	11th to 20th	Night	8% 13% 37% 34% 7% 1	950
	21st to end	Night	11% 11% 39% 30% 9%	1045
February	1st to 10th	Night	14% 10% 40% 31% 5%	950
	11th to 20th	Night	12% 10% 39% 31% 7% 1	849
	21st to end	Night	13% 10% 35% 31% 11% 1	628
March	1st to 10th	Night	10% 9% 43% 32% 6%	727
	11th to 20th	Night	14% 9% 38% 31% 7% 1	570
	21st to end	Night	18% 9% 32% 32% 9%	627
April	1st to 10th	Night	16% 11% 39% 29% 4	570
	11th to 20th	Night	19% 13% 33% 28% 6%	563
	21st to end	Night	17% 11% 33% 29% 9% 1	570
May	1st to 10th	Night	14% 9% 37% 30% 11%	570
	11th to 20th	Night	14% 7% 34% 33% 10% 1	561
	21st to end	Night	14% 7% 38% 29% 11% 1	617
June	1st to 10th	Night	10% 6% 28% 38% 18% 1	570
	11th to 20th	Night	9% 7% 36% 38% 10%	570
	21st to end	Night	6% 5% 30% 46% 13%	570
July	1st to 10th	Night	6% 3 25% 44% 22%	555
	11th to 20th	Night	3 2 29% 53% 13%	552
	21st to end	Night	4 2 26% 53% 14% 1	624
August	1st to 10th	Night	7% 3 25% 50% 15%	567
	11th to 20th	Night	8% 2 29% 41% 20% 1	564
	21st to end	Night	5% 3 30% 46% 15% 1	627
September	1st to 10th	Night	10% 6% 30% 36% 15% 2	570
	11th to 20th	Night	8% 4 36% 36% 15% 2	570
	21st to end	Night	11% 8% 34% 34% 13% 1	570
October	1st to 10th	Night	15% 8% 33% 33% 10% 1	615
	11th to 20th	Night	15% 10% 37% 28% 10%	760
	21st to end	Night	15% 12% 36% 30% 7%	1026
November	1st to 10th	Night	11% 8% 38% 34% 8% 1	975
	11th to 20th	Night	10% 12% 37% 32% 9%	1000
	21st to end	Night	9% 10% 39% 34% 8%	986
December	1st to 10th	Night	10% 12% 39% 31% 7%	950
	11th to 20th	Night	12% 10% 37% 32% 9%	950
	21st to end	Night	21% 10% 33% 29% 7%	1045

Page generated at 2024-11-24 23:22:19. Version ac07

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