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 2024-02-15.

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	11% 6% 3 6% 6% 4 5% 6% 6% 8% 39%	78729
	Night	11% 6% 3 5% 5% 3 5% 5% 6% 8% 44%	80359
Transparency	Day	28% 37% 8% 11% 11% 5%	78452
	Night	26% 36% 9% 12% 12% 6%	80155
Seeing	Day	12% 9% 23% 25% 21% 11%	14291
	Night	12% 7% 23% 32% 22% 4	24432

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	13% 7% 2 6% 5% 2 3 4 4 7% 48%	2836
	11th to 20th	Day	16% 7% 3 6% 5% 3 4 4 5% 6% 41%	2840
	21st to end	Day	12% 6% 2 5% 5% 3 4 4 6% 7% 45%	3197
February	1st to 10th	Day	16% 7% 3 5% 5% 3 4 4 5% 6% 43%	1900
	11th to 20th	Day	13% 5% 2 5% 5% 2 4 5% 4 6% 48%	1788
	21st to end	Day	13% 6% 3 5% 5% 3 4 4 4 6% 46%	1500
March	1st to 10th	Day	10% 4 2 4 4 3 3 4 5% 8% 53%	1980
	11th to 20th	Day	10% 4 3 5% 6% 3 4 6% 6% 7% 46%	1980
	21st to end	Day	11% 4 3 5% 5% 3 3 4 5% 8% 50%	2178
April	1st to 10th	Day	9% 5% 2 5% 6% 3 5% 6% 5% 8% 46%	1980
	11th to 20th	Day	11% 5% 2 7% 7% 4 6% 5% 5% 7% 42%	1978
	21st to end	Day	7% 4 2 3 5% 4 6% 5% 5% 7% 53%	2278
May	1st to 10th	Day	6% 3 2 4 5% 3 5% 4 5% 8% 53%	2340
	11th to 20th	Day	8% 4 3 7% 7% 4 7% 6% 7% 9% 38%	2301
	21st to end	Day	9% 5% 3 7% 7% 5% 6% 5% 7% 9% 37%	2531
June	1st to 10th	Day	11% 6% 3 7% 8% 6% 6% 7% 7% 10% 29%	2340
	11th to 20th	Day	6% 5% 3 7% 8% 6% 8% 8% 9% 10% 30%	2340
	21st to end	Day	9% 6% 3 7% 9% 5% 8% 7% 8% 10% 28%	2340
July	1st to 10th	Day	8% 7% 3 8% 9% 5% 8% 7% 9% 11% 25%	2340
	11th to 20th	Day	8% 6% 4 9% 9% 6% 7% 8% 10% 10% 22%	2340
	21st to end	Day	9% 5% 4 8% 8% 6% 7% 7% 7% 10% 29%	2547
August	1st to 10th	Day	11% 7% 3 7% 8% 6% 8% 9% 9% 9% 24%	2327
	11th to 20th	Day	10% 8% 4 6% 9% 5% 9% 8% 9% 11% 22%	2239
	21st to end	Day	13% 7% 4 8% 9% 5% 8% 7% 7% 9% 23%	2219
September	1st to 10th	Day	9% 6% 3 9% 10% 6% 8% 7% 9% 9% 25%	1980
	11th to 20th	Day	13% 8% 3 8% 8% 5% 7% 7% 8% 8% 25%	1980
	21st to end	Day	13% 6% 3 6% 8% 3 5% 5% 5% 7% 38%	1980
October	1st to 10th	Day	12% 6% 3 6% 6% 4 5% 5% 5% 7% 40%	1980
	11th to 20th	Day	7% 4 2 4 4 3 5% 4 4 7% 55%	1805
	21st to end	Day	9% 4 1 6% 6% 3 5% 5% 6% 7% 49%	1980
November	1st to 10th	Day	11% 5% 3 5% 5% 2 4 4 4 7% 52%	1857
	11th to 20th	Day	9% 7% 2 4 5% 3 4 4 5% 6% 52%	1831
	21st to end	Day	12% 6% 3 5% 4 3 5% 5% 4 6% 47%	1710
December	1st to 10th	Day	10% 7% 2 6% 6% 3 4 5% 6% 7% 44%	1710
	11th to 20th	Day	17% 6% 3 5% 5% 3 3 4 5% 6% 45%	2153
	21st to end	Day	16% 9% 4 6% 6% 3 4 4 3 5% 41%	3124
January	1st to 10th	Night	14% 8% 3 5% 4 2 3 5% 5% 6% 44%	4109
	11th to 20th	Night	11% 7% 3 6% 5% 4 6% 5% 6% 8% 40%	4120
	21st to end	Night	15% 7% 3 5% 5% 3 4 5% 6% 7% 41%	4455
February	1st to 10th	Night	14% 7% 2 6% 5% 3 4 4 4 7% 45%	2280
	11th to 20th	Night	13% 6% 3 5% 4 2 3 4 4 6% 49%	2153
	21st to end	Night	13% 6% 3 6% 5% 2 4 4 5% 6% 47%	1754
March	1st to 10th	Night	9% 5% 2 4 4 3 3 4 5% 6% 54%	1980
	11th to 20th	Night	10% 6% 2 5% 4 2 4 4 6% 7% 49%	1980
	21st to end	Night	10% 4 2 4 4 3 4 4 4 6% 55%	2178
April	1st to 10th	Night	11% 5% 2 3 5% 3 4 5% 5% 7% 50%	1980
	11th to 20th	Night	9% 5% 3 5% 5% 3 4 4 5% 7% 51%	1931
	21st to end	Night	6% 5% 2 3 3 2 4 5% 6% 8% 57%	1695
May	1st to 10th	Night	5% 3 2 3 4 3 5% 4 5% 7% 60%	1620
	11th to 20th	Night	7% 4 2 5% 5% 3 5% 6% 6% 10% 46%	1592
	21st to end	Night	8% 4 2 4 5% 3 5% 4 7% 11% 47%	1744
June	1st to 10th	Night	10% 6% 3 5% 6% 3 6% 7% 9% 9% 35%	1620
	11th to 20th	Night	6% 3 2 6% 7% 4 7% 8% 9% 12% 37%	1620
	21st to end	Night	7% 4 2 6% 6% 3 7% 7% 8% 13% 36%	1620
July	1st to 10th	Night	6% 4 2 7% 7% 3 6% 8% 9% 14% 33%	1620
	11th to 20th	Night	6% 6% 3 6% 6% 4 6% 7% 10% 13% 32%	1620
	21st to end	Night	4 4 3 5% 6% 4 7% 6% 9% 14% 38%	1771
August	1st to 10th	Night	7% 3 3 7% 6% 3 7% 9% 9% 12% 35%	1611
	11th to 20th	Night	6% 5% 2 6% 7% 4 7% 8% 9% 14% 32%	1657
	21st to end	Night	11% 7% 3 7% 7% 5% 7% 7% 7% 10% 30%	2118
September	1st to 10th	Night	9% 6% 3 7% 7% 5% 6% 6% 7% 12% 31%	1980
	11th to 20th	Night	13% 6% 3 8% 7% 4 7% 7% 6% 9% 31%	1980
	21st to end	Night	8% 7% 3 6% 6% 4 5% 5% 6% 9% 42%	1980
October	1st to 10th	Night	11% 6% 2 5% 5% 2 5% 4 4 9% 46%	1980
	11th to 20th	Night	7% 5% 2 4 5% 3 3 4 4 7% 57%	2154
	21st to end	Night	7% 4 2 5% 5% 3 5% 5% 6% 7% 51%	2376
November	1st to 10th	Night	11% 4 1 4 4 2 4 5% 6% 8% 52%	2221
	11th to 20th	Night	12% 6% 3 4 4 2 4 3 4 6% 52%	2346
	21st to end	Night	13% 6% 3 6% 4 3 3 4 5% 6% 47%	2470
December	1st to 10th	Night	13% 6% 2 5% 4 2 4 5% 5% 8% 45%	2470
	11th to 20th	Night	16% 6% 2 5% 4 3 3 4 3 7% 47%	3042
	21st to end	Night	16% 8% 3 6% 5% 3 4 4 5% 6% 40%	4532

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	28% 25% 4 13% 19% 11%	2837
	11th to 20th	Day	35% 25% 5% 10% 11% 13%	2840
	21st to end	Day	29% 25% 9% 10% 16% 11%	3197
February	1st to 10th	Day	29% 35% 5% 10% 14% 8%	1900
	11th to 20th	Day	26% 37% 5% 8% 14% 10%	1798
	21st to end	Day	25% 35% 6% 13% 12% 9%	1500
March	1st to 10th	Day	20% 36% 4 14% 17% 8%	1980
	11th to 20th	Day	22% 37% 8% 13% 13% 7%	1980
	21st to end	Day	22% 37% 9% 14% 14% 4	2178
April	1st to 10th	Day	23% 38% 6% 11% 14% 8%	1980
	11th to 20th	Day	26% 37% 6% 11% 14% 6%	1978
	21st to end	Day	19% 37% 7% 15% 16% 7%	2278
May	1st to 10th	Day	20% 38% 8% 15% 15% 4	2340
	11th to 20th	Day	24% 40% 10% 14% 10% 1	2305
	21st to end	Day	28% 39% 9% 12% 11% 1	2531
June	1st to 10th	Day	30% 40% 11% 11% 8% 1	2340
	11th to 20th	Day	28% 41% 13% 13% 5%	2340
	21st to end	Day	33% 42% 11% 9% 5%	2340
July	1st to 10th	Day	35% 44% 12% 6% 2	2275
	11th to 20th	Day	35% 43% 12% 7% 3	2271
	21st to end	Day	31% 43% 13% 10% 2	2405
August	1st to 10th	Day	31% 43% 14% 10% 2	2314
	11th to 20th	Day	35% 42% 13% 8% 2	2239
	21st to end	Day	40% 42% 10% 7% 2 1	2219
September	1st to 10th	Day	34% 41% 11% 9% 5%	1980
	11th to 20th	Day	37% 42% 8% 7% 4 1	1980
	21st to end	Day	32% 37% 6% 9% 12% 4	1980
October	1st to 10th	Day	26% 37% 6% 11% 10% 10%	1980
	11th to 20th	Day	22% 36% 5% 12% 20% 6%	1805
	21st to end	Day	23% 37% 5% 10% 15% 9%	1980
November	1st to 10th	Day	18% 40% 5% 12% 15% 11%	1857
	11th to 20th	Day	21% 40% 5% 10% 16% 8%	1831
	21st to end	Day	26% 40% 4 11% 14% 5%	1710
December	1st to 10th	Day	24% 40% 6% 14% 11% 5%	1710
	11th to 20th	Day	30% 32% 6% 13% 15% 4	2150
	21st to end	Day	35% 25% 3 13% 18% 6%	3124
January	1st to 10th	Night	31% 25% 5% 9% 17% 12%	4109
	11th to 20th	Night	34% 26% 5% 10% 17% 8%	4120
	21st to end	Night	33% 26% 9% 9% 13% 10%	4455
February	1st to 10th	Night	29% 35% 5% 10% 13% 9%	2280
	11th to 20th	Night	27% 36% 5% 9% 12% 11%	2154
	21st to end	Night	25% 36% 6% 14% 12% 8%	1754
March	1st to 10th	Night	21% 37% 6% 13% 14% 10%	1980
	11th to 20th	Night	20% 37% 11% 13% 12% 7%	1980
	21st to end	Night	19% 37% 9% 16% 13% 6%	2178
April	1st to 10th	Night	22% 38% 9% 11% 13% 7%	1980
	11th to 20th	Night	22% 36% 7% 14% 16% 6%	1931
	21st to end	Night	16% 37% 9% 17% 16% 5%	1695
May	1st to 10th	Night	15% 39% 8% 21% 14% 4	1620
	11th to 20th	Night	20% 41% 16% 12% 10% 2	1593
	21st to end	Night	20% 40% 10% 17% 11% 2	1745
June	1st to 10th	Night	24% 42% 13% 14% 7%	1620
	11th to 20th	Night	24% 41% 17% 14% 4	1620
	21st to end	Night	26% 42% 16% 12% 4 1	1620
July	1st to 10th	Night	31% 44% 13% 9% 2 1	1575
	11th to 20th	Night	27% 44% 16% 8% 4	1566
	21st to end	Night	21% 46% 19% 12% 2	1672
August	1st to 10th	Night	22% 45% 19% 11% 3	1600
	11th to 20th	Night	25% 44% 18% 10% 2	1657
	21st to end	Night	35% 43% 11% 9% 2 1	2118
September	1st to 10th	Night	29% 42% 14% 11% 3 1	1980
	11th to 20th	Night	34% 42% 9% 9% 5%	1980
	21st to end	Night	27% 39% 10% 11% 10% 4	1980
October	1st to 10th	Night	23% 38% 8% 12% 10% 10%	1980
	11th to 20th	Night	21% 37% 6% 12% 18% 6%	2154
	21st to end	Night	22% 38% 7% 10% 14% 9%	2376
November	1st to 10th	Night	16% 41% 5% 13% 14% 12%	2221
	11th to 20th	Night	22% 39% 4 10% 16% 8%	2346
	21st to end	Night	26% 40% 6% 11% 11% 6%	2470
December	1st to 10th	Night	23% 40% 8% 13% 11% 5%	2470
	11th to 20th	Night	28% 34% 6% 11% 17% 4	3044
	21st to end	Night	33% 26% 6% 13% 17% 4	4532

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	14% 20% 46% 15% 4	270
	11th to 20th	Day	13% 15% 42% 19% 8% 2	270
	21st to end	Day	21% 22% 41% 13% 3	297
February	1st to 10th	Day	23% 15% 37% 18% 6% 1	270
	11th to 20th	Day	19% 18% 43% 14% 5% 1	252
	21st to end	Day	13% 17% 39% 26% 4	218
March	1st to 10th	Day	14% 16% 32% 28% 10%	420
	11th to 20th	Day	15% 17% 33% 19% 11% 4	420
	21st to end	Day	14% 15% 35% 23% 12% 2	462
April	1st to 10th	Day	14% 15% 31% 23% 15% 2	420
	11th to 20th	Day	10% 15% 32% 25% 13% 5%	412
	21st to end	Day	8% 10% 27% 30% 16% 9%	420
May	1st to 10th	Day	7% 10% 27% 29% 18% 8%	423
	11th to 20th	Day	7% 4 22% 28% 26% 13%	447
	21st to end	Day	11% 4 12% 27% 31% 15%	485
June	1st to 10th	Day	13% 3 14% 30% 22% 18%	450
	11th to 20th	Day	7% 5% 12% 24% 29% 22%	450
	21st to end	Day	9% 2 9% 24% 32% 24%	450
July	1st to 10th	Day	7% 1 7% 23% 35% 28%	445
	11th to 20th	Day	8% 2 5% 19% 37% 29%	444
	21st to end	Day	8% 3 7% 26% 35% 20%	488
August	1st to 10th	Day	12% 3 10% 17% 34% 25%	446
	11th to 20th	Day	8% 3 4 18% 35% 33%	439
	21st to end	Day	11% 3 9% 23% 32% 21%	495
September	1st to 10th	Day	10% 3 10% 25% 28% 24%	450
	11th to 20th	Day	15% 4 11% 30% 28% 12%	450
	21st to end	Day	14% 2 12% 27% 32% 13%	450
October	1st to 10th	Day	13% 5% 28% 29% 19% 6%	450
	11th to 20th	Day	8% 5% 21% 36% 23% 7%	450
	21st to end	Day	9% 7% 28% 34% 19% 3	495
November	1st to 10th	Day	16% 6% 28% 28% 19% 4	455
	11th to 20th	Day	16% 13% 34% 25% 10% 2	391
	21st to end	Day	13% 17% 37% 24% 9% 1	270
December	1st to 10th	Day	13% 18% 31% 24% 10% 4	270
	11th to 20th	Day	20% 18% 33% 23% 6%	270
	21st to end	Day	17% 12% 34% 27% 7% 2	297
January	1st to 10th	Night	17% 14% 34% 29% 7%	760
	11th to 20th	Night	13% 12% 30% 34% 11% 1	760
	21st to end	Night	17% 16% 36% 26% 5%	836
February	1st to 10th	Night	17% 12% 31% 31% 9% 1	760
	11th to 20th	Night	16% 16% 30% 31% 7%	722
	21st to end	Night	16% 12% 33% 36% 4	592
March	1st to 10th	Night	11% 13% 31% 38% 8%	720
	11th to 20th	Night	13% 9% 35% 30% 12% 1	720
	21st to end	Night	11% 12% 33% 32% 11%	792
April	1st to 10th	Night	12% 10% 33% 34% 11%	720
	11th to 20th	Night	12% 10% 34% 32% 11%	711
	21st to end	Night	7% 7% 28% 40% 17% 1	615
May	1st to 10th	Night	5% 3 29% 46% 16% 1	540
	11th to 20th	Night	8% 3 20% 40% 25% 2	531
	21st to end	Night	7% 2 12% 40% 35% 3	584
June	1st to 10th	Night	11% 1 14% 37% 31% 6%	540
	11th to 20th	Night	5% 2 9% 34% 36% 13%	540
	21st to end	Night	8% 2 8% 27% 43% 12%	540
July	1st to 10th	Night	6% 2 7% 24% 44% 18%	525
	11th to 20th	Night	8% 1 4 21% 48% 18%	522
	21st to end	Night	4 1 7% 29% 49% 10%	591
August	1st to 10th	Night	7% 1 5% 25% 49% 13%	537
	11th to 20th	Night	7% 1 4 21% 48% 18%	534
	21st to end	Night	12% 2 9% 26% 37% 14%	732
September	1st to 10th	Night	12% 2 11% 28% 35% 12%	720
	11th to 20th	Night	14% 3 14% 30% 33% 7%	720
	21st to end	Night	13% 2 13% 35% 33% 6%	720
October	1st to 10th	Night	14% 1 22% 36% 24% 3	720
	11th to 20th	Night	8% 5% 22% 37% 26% 2	720
	21st to end	Night	8% 6% 26% 37% 21% 2	792
November	1st to 10th	Night	11% 6% 29% 37% 16% 1	740
	11th to 20th	Night	13% 9% 30% 32% 15% 1	760
	21st to end	Night	14% 8% 30% 33% 15%	760
December	1st to 10th	Night	16% 9% 26% 32% 16% 1	760
	11th to 20th	Night	15% 10% 28% 32% 14%	760
	21st to end	Night	17% 12% 26% 32% 12%	836

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