North Smoke Tower Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the North Smoke Tower Site clear sky chart from 2005-11-06 to 2026-07-31.

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% 6% 2 7% 5% 5% 5% 4 7% 9% 40%	138143
	Night	11% 6% 2 6% 4 4 5% 4 6% 8% 43%	134883
Transparency	Day	39% 8% 14% 17% 15% 7%	141880
	Night	37% 8% 14% 18% 16% 8%	139218
Seeing	Day	12% 9% 23% 25% 20% 10%	17660
	Night	12% 7% 23% 32% 21% 4	27678

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	9% 7% 2 6% 4 3 3 3 5% 7% 51%	5258
	11th to 20th	Day	18% 7% 3 7% 4 4 4 3 5% 6% 40%	5280
	21st to end	Day	9% 6% 2 6% 4 4 4 4 6% 9% 46%	5937
February	1st to 10th	Day	14% 7% 2 5% 4 4 4 4 5% 6% 45%	2100
	11th to 20th	Day	14% 6% 2 6% 4 3 4 4 4 6% 47%	2048
	21st to end	Day	12% 6% 3 6% 4 4 3 3 4 6% 49%	1754
March	1st to 10th	Day	16% 7% 2 6% 4 4 4 3 5% 7% 40%	5045
	11th to 20th	Day	8% 3 2 4 4 3 4 4 6% 8% 54%	5090
	21st to end	Day	13% 4 2 5% 4 4 4 4 5% 7% 48%	5586
April	1st to 10th	Day	9% 5% 2 6% 5% 4 5% 4 5% 8% 46%	2310
	11th to 20th	Day	10% 5% 2 7% 5% 5% 4 4 5% 7% 46%	2312
	21st to end	Day	6% 4 2 4 4 5% 5% 4 6% 8% 51%	2659
May	1st to 10th	Day	10% 7% 2 7% 5% 5% 6% 4 6% 8% 39%	7616
	11th to 20th	Day	11% 6% 2 6% 4 4 5% 3 6% 9% 43%	7626
	21st to end	Day	5% 4 2 6% 6% 6% 6% 5% 8% 12% 39%	8391
June	1st to 10th	Day	10% 6% 2 8% 7% 7% 6% 6% 8% 10% 30%	2730
	11th to 20th	Day	6% 6% 3 8% 7% 7% 8% 7% 9% 10% 29%	2730
	21st to end	Day	8% 6% 2 8% 8% 7% 6% 6% 9% 10% 29%	2730
July	1st to 10th	Day	7% 8% 4 11% 8% 8% 9% 7% 10% 11% 17%	6030
	11th to 20th	Day	4 4 2 7% 6% 6% 7% 7% 10% 15% 33%	6030
	21st to end	Day	5% 5% 2 7% 6% 7% 8% 6% 9% 14% 31%	6554
August	1st to 10th	Day	14% 6% 2 8% 6% 7% 7% 7% 9% 10% 22%	4234
	11th to 20th	Day	7% 5% 2 6% 6% 6% 8% 6% 8% 11% 35%	4050
	21st to end	Day	10% 7% 3 9% 7% 7% 7% 6% 8% 11% 25%	4020
September	1st to 10th	Day	10% 8% 3 10% 8% 7% 7% 6% 8% 8% 25%	2200
	11th to 20th	Day	13% 8% 3 9% 7% 6% 6% 5% 8% 9% 25%	2200
	21st to end	Day	12% 6% 3 8% 6% 4 5% 4 6% 8% 37%	2200
October	1st to 10th	Day	12% 7% 2 8% 5% 5% 5% 4 6% 7% 39%	2200
	11th to 20th	Day	6% 4 2 5% 3 4 5% 3 4 7% 57%	2005
	21st to end	Day	9% 4 1 6% 5% 4 4 4 6% 6% 51%	2200
November	1st to 10th	Day	10% 5% 2 5% 4 3 4 3 5% 7% 51%	2057
	11th to 20th	Day	9% 7% 2 5% 4 4 3 3 5% 6% 53%	2023
	21st to end	Day	11% 6% 3 5% 4 5% 4 4 5% 6% 48%	1890
December	1st to 10th	Day	7% 5% 2 6% 4 4 4 4 5% 6% 53%	3020
	11th to 20th	Day	14% 8% 3 7% 4 4 4 3 6% 6% 42%	3463
	21st to end	Day	15% 9% 3 7% 5% 4 4 3 4 6% 42%	4565
January	1st to 10th	Night	10% 7% 2 4 3 3 3 3 5% 7% 54%	7635
	11th to 20th	Night	14% 7% 2 6% 5% 5% 5% 4 6% 7% 40%	7680
	21st to end	Night	15% 8% 2 6% 3 3 3 3 6% 7% 43%	8240
February	1st to 10th	Night	13% 7% 2 6% 4 3 4 3 4 7% 47%	2520
	11th to 20th	Night	14% 7% 2 6% 4 3 3 3 4 6% 48%	2458
	21st to end	Night	12% 6% 2 6% 4 3 4 3 4 6% 50%	2050
March	1st to 10th	Night	18% 9% 2 6% 4 3 3 3 4 5% 41%	5028
	11th to 20th	Night	7% 4 2 4 2 3 3 3 7% 10% 54%	5090
	21st to end	Night	11% 6% 2 5% 4 4 4 3 5% 7% 51%	5588
April	1st to 10th	Night	10% 6% 2 4 4 4 4 4 6% 7% 48%	2310
	11th to 20th	Night	8% 5% 2 5% 4 3 3 3 5% 7% 55%	2256
	21st to end	Night	5% 5% 2 4 3 4 4 4 6% 8% 54%	1977
May	1st to 10th	Night	9% 7% 3 7% 5% 5% 5% 4 6% 8% 41%	5237
	11th to 20th	Night	12% 6% 2 6% 4 4 4 3 6% 9% 43%	5234
	21st to end	Night	7% 5% 2 7% 5% 5% 5% 4 7% 11% 41%	5761
June	1st to 10th	Night	10% 7% 3 6% 6% 5% 6% 6% 9% 9% 34%	1890
	11th to 20th	Night	6% 5% 2 7% 6% 6% 7% 6% 8% 12% 35%	1890
	21st to end	Night	7% 4 2 6% 5% 5% 7% 6% 8% 13% 36%	1890
July	1st to 10th	Night	9% 9% 3 12% 7% 7% 7% 6% 8% 11% 20%	4148
	11th to 20th	Night	4 5% 2 7% 6% 6% 7% 6% 11% 14% 31%	4147
	21st to end	Night	6% 6% 3 8% 6% 6% 7% 5% 10% 11% 32%	4517
August	1st to 10th	Night	13% 5% 3 8% 5% 6% 8% 6% 9% 10% 27%	2915
	11th to 20th	Night	5% 4 2 6% 4 4 6% 6% 8% 13% 42%	2994
	21st to end	Night	10% 7% 2 8% 5% 5% 6% 5% 7% 12% 34%	3844
September	1st to 10th	Night	11% 7% 3 9% 6% 6% 6% 4 7% 11% 31%	2200
	11th to 20th	Night	13% 7% 3 9% 6% 5% 6% 5% 7% 8% 32%	2200
	21st to end	Night	8% 7% 3 7% 5% 5% 4 4 6% 9% 43%	2200
October	1st to 10th	Night	12% 6% 3 7% 5% 4 5% 3 4 8% 44%	2200
	11th to 20th	Night	7% 5% 2 5% 4 3 3 3 4 6% 58%	2394
	21st to end	Night	8% 4 2 6% 4 4 4 4 6% 7% 53%	2640
November	1st to 10th	Night	10% 4 2 5% 3 3 4 4 7% 7% 51%	2461
	11th to 20th	Night	11% 6% 2 4 4 3 3 3 4 6% 53%	2594
	21st to end	Night	12% 6% 2 6% 4 4 3 3 5% 6% 48%	2730
December	1st to 10th	Night	11% 6% 2 5% 3 3 4 3 4 6% 54%	4380
	11th to 20th	Night	13% 10% 3 6% 4 3 3 3 3 6% 45%	4952
	21st to end	Night	14% 9% 3 7% 4 4 4 3 5% 5% 42%	6633

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	33% 4 9% 15% 28% 11%	5259
	11th to 20th	Day	45% 4 5% 14% 16% 16%	5280
	21st to end	Day	35% 5% 9% 21% 18% 12%	5937
February	1st to 10th	Day	40% 4 9% 14% 21% 12%	2100
	11th to 20th	Day	39% 4 8% 15% 21% 12%	2058
	21st to end	Day	37% 4 9% 17% 18% 15%	1754
March	1st to 10th	Day	43% 6% 9% 14% 17% 11%	5045
	11th to 20th	Day	27% 5% 11% 16% 18% 22%	5090
	21st to end	Day	34% 5% 9% 21% 18% 13%	5586
April	1st to 10th	Day	35% 7% 10% 18% 17% 12%	2310
	11th to 20th	Day	37% 5% 8% 17% 22% 11%	2312
	21st to end	Day	28% 7% 12% 23% 21% 9%	2659
May	1st to 10th	Day	40% 9% 13% 22% 14% 4	7651
	11th to 20th	Day	35% 7% 13% 30% 13% 2	7630
	21st to end	Day	34% 11% 21% 20% 14% 1	8405
June	1st to 10th	Day	46% 10% 17% 14% 11% 1	2730
	11th to 20th	Day	43% 13% 19% 18% 6%	2730
	21st to end	Day	45% 14% 19% 15% 6%	2730
July	1st to 10th	Day	53% 16% 23% 6% 1	5965
	11th to 20th	Day	34% 15% 36% 13% 2	5961
	21st to end	Day	39% 14% 25% 20% 2	6370
August	1st to 10th	Day	50% 14% 24% 11% 2	4221
	11th to 20th	Day	38% 13% 20% 20% 9%	4089
	21st to end	Day	48% 13% 17% 19% 2	4020
September	1st to 10th	Day	52% 13% 15% 11% 7% 2	2200
	11th to 20th	Day	51% 12% 14% 14% 8% 1	2200
	21st to end	Day	44% 8% 12% 18% 15% 4	2200
October	1st to 10th	Day	50% 5% 8% 10% 15% 12%	3590
	11th to 20th	Day	19% 4 6% 16% 37% 18%	3245
	21st to end	Day	24% 4 7% 17% 36% 12%	3538
November	1st to 10th	Day	33% 5% 10% 19% 19% 14%	2057
	11th to 20th	Day	32% 4 9% 17% 25% 13%	2023
	21st to end	Day	36% 5% 9% 18% 22% 9%	1890
December	1st to 10th	Day	32% 4 9% 19% 24% 11%	3020
	11th to 20th	Day	41% 5% 8% 19% 20% 8%	3460
	21st to end	Day	45% 4 6% 17% 22% 5%	4565
January	1st to 10th	Night	30% 4 10% 16% 30% 11%	7636
	11th to 20th	Night	43% 4 6% 14% 20% 12%	7680
	21st to end	Night	40% 5% 8% 18% 18% 10%	8240
February	1st to 10th	Night	38% 5% 9% 15% 21% 13%	2520
	11th to 20th	Night	37% 5% 9% 17% 18% 13%	2459
	21st to end	Night	36% 5% 10% 18% 18% 13%	2050
March	1st to 10th	Night	46% 5% 9% 16% 14% 11%	5028
	11th to 20th	Night	25% 5% 12% 18% 21% 19%	5090
	21st to end	Night	33% 5% 11% 18% 20% 13%	5588
April	1st to 10th	Night	33% 7% 14% 17% 17% 11%	2310
	11th to 20th	Night	30% 5% 9% 22% 23% 11%	2256
	21st to end	Night	26% 7% 13% 25% 20% 8%	1977
May	1st to 10th	Night	38% 9% 17% 21% 11% 4	5264
	11th to 20th	Night	36% 7% 20% 24% 10% 3	5235
	21st to end	Night	35% 10% 19% 22% 13% 1	5771
June	1st to 10th	Night	39% 12% 20% 18% 10%	1890
	11th to 20th	Night	37% 14% 24% 18% 6%	1890
	21st to end	Night	36% 15% 24% 19% 5% 1	1890
July	1st to 10th	Night	53% 15% 24% 7% 1	4105
	11th to 20th	Night	37% 18% 33% 11% 2	4096
	21st to end	Night	40% 15% 25% 19% 1	4387
August	1st to 10th	Night	46% 14% 27% 10% 2	2904
	11th to 20th	Night	29% 14% 26% 22% 9%	3021
	21st to end	Night	41% 11% 24% 20% 3	3844
September	1st to 10th	Night	45% 13% 20% 14% 7% 2	2200
	11th to 20th	Night	46% 14% 14% 18% 7% 1	2200
	21st to end	Night	36% 8% 19% 21% 12% 4	2200
October	1st to 10th	Night	48% 7% 10% 13% 13% 10%	3590
	11th to 20th	Night	21% 4 6% 18% 33% 18%	3893
	21st to end	Night	23% 4 9% 19% 32% 13%	4252
November	1st to 10th	Night	30% 6% 10% 22% 18% 14%	2461
	11th to 20th	Night	33% 5% 8% 17% 24% 12%	2594
	21st to end	Night	36% 5% 11% 18% 19% 11%	2730
December	1st to 10th	Night	33% 4 9% 18% 20% 16%	4380
	11th to 20th	Night	41% 5% 8% 19% 18% 9%	4954
	21st to end	Night	43% 5% 9% 17% 20% 5%	6633

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	13% 19% 46% 17% 4	330
	11th to 20th	Day	15% 16% 42% 18% 7% 2	330
	21st to end	Day	21% 22% 40% 15% 3	363
February	1st to 10th	Day	20% 15% 36% 23% 5% 1	330
	11th to 20th	Day	22% 19% 40% 14% 4 1	330
	21st to end	Day	15% 18% 41% 23% 3	297
March	1st to 10th	Day	15% 16% 31% 27% 10% 1	540
	11th to 20th	Day	15% 16% 33% 23% 10% 3	540
	21st to end	Day	14% 15% 34% 24% 11% 2	594
April	1st to 10th	Day	14% 14% 32% 24% 14% 2	540
	11th to 20th	Day	9% 13% 32% 27% 13% 5%	532
	21st to end	Day	7% 10% 25% 33% 16% 8%	540
May	1st to 10th	Day	8% 10% 27% 29% 19% 7%	543
	11th to 20th	Day	8% 7% 26% 27% 23% 10%	567
	21st to end	Day	10% 4 15% 29% 29% 13%	617
June	1st to 10th	Day	12% 4 15% 32% 22% 15%	570
	11th to 20th	Day	7% 4 15% 26% 28% 20%	570
	21st to end	Day	7% 3 9% 26% 32% 23%	570
July	1st to 10th	Day	7% 1 8% 23% 35% 27%	565
	11th to 20th	Day	6% 2 5% 21% 39% 27%	564
	21st to end	Day	7% 3 8% 25% 36% 21%	616
August	1st to 10th	Day	13% 3 9% 18% 33% 23%	526
	11th to 20th	Day	8% 2 4 19% 35% 32%	519
	21st to end	Day	11% 3 10% 24% 31% 21%	583
September	1st to 10th	Day	12% 4 12% 25% 26% 21%	530
	11th to 20th	Day	15% 4 12% 30% 28% 11%	530
	21st to end	Day	14% 3 12% 28% 32% 12%	530
October	1st to 10th	Day	14% 6% 28% 29% 18% 5%	530
	11th to 20th	Day	7% 6% 22% 35% 22% 7%	530
	21st to end	Day	9% 8% 29% 33% 18% 3	583
November	1st to 10th	Day	15% 6% 27% 29% 19% 3	535
	11th to 20th	Day	14% 12% 35% 26% 11% 2	463
	21st to end	Day	11% 20% 36% 24% 8% 2	330
December	1st to 10th	Day	14% 19% 33% 21% 9% 4	330
	11th to 20th	Day	18% 18% 34% 22% 7%	330
	21st to end	Day	16% 13% 34% 28% 8% 2	363
January	1st to 10th	Night	16% 14% 34% 30% 6%	840
	11th to 20th	Night	14% 12% 31% 33% 10%	840
	21st to end	Night	17% 15% 37% 27% 4	924
February	1st to 10th	Night	16% 12% 31% 32% 9%	840
	11th to 20th	Night	17% 16% 31% 29% 7%	823
	21st to end	Night	15% 13% 35% 34% 3	692
March	1st to 10th	Night	12% 13% 31% 36% 8%	840
	11th to 20th	Night	12% 11% 35% 30% 11% 1	840
	21st to end	Night	11% 12% 33% 33% 11%	924
April	1st to 10th	Night	12% 10% 33% 33% 11%	840
	11th to 20th	Night	11% 10% 33% 34% 11%	831
	21st to end	Night	7% 7% 27% 41% 17% 1	717
May	1st to 10th	Night	6% 3 29% 45% 16% 1	630
	11th to 20th	Night	9% 4 23% 40% 22% 2	621
	21st to end	Night	8% 2 14% 39% 33% 3	683
June	1st to 10th	Night	10% 2 16% 39% 28% 5%	630
	11th to 20th	Night	7% 3 10% 33% 36% 12%	630
	21st to end	Night	7% 3 8% 27% 43% 11%	630
July	1st to 10th	Night	6% 2 7% 24% 44% 17%	615
	11th to 20th	Night	7% 1 4 21% 49% 17%	612
	21st to end	Night	5% 1 8% 28% 48% 11%	687
August	1st to 10th	Night	9% 1 5% 25% 47% 12%	597
	11th to 20th	Night	7% 1 5% 20% 49% 19%	594
	21st to end	Night	13% 3 10% 26% 36% 13%	814
September	1st to 10th	Night	13% 2 12% 28% 33% 12%	800
	11th to 20th	Night	14% 3 14% 31% 32% 6%	800
	21st to end	Night	12% 3 13% 35% 32% 6%	800
October	1st to 10th	Night	15% 2 23% 36% 23% 3	800
	11th to 20th	Night	9% 5% 23% 36% 25% 2	800
	21st to end	Night	8% 6% 25% 38% 21% 2	880
November	1st to 10th	Night	11% 6% 27% 38% 17% 1	820
	11th to 20th	Night	13% 9% 29% 33% 15% 1	840
	21st to end	Night	14% 9% 30% 33% 14%	840
December	1st to 10th	Night	16% 9% 27% 33% 14%	840
	11th to 20th	Night	14% 10% 29% 33% 14%	840
	21st to end	Night	16% 12% 27% 32% 12%	924

Page generated at 2026-07-28 03:25:24. Version ac07

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