Johnson City
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Johnson City clear sky chart from 2005-11-06 to 2024-01-31.

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	11% 5% 2 4 4 3 4 5% 5% 7% 49%	75046
	Night	11% 5% 2 4 4 2 4 4 5% 7% 53%	75111
Transparency	Day	34% 6% 10% 20% 20% 10%	74771
	Night	31% 6% 11% 20% 20% 12%	74906
Seeing	Day	13% 7% 23% 32% 20% 5%	13773
	Night	13% 7% 29% 36% 14% 1	23861

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	12% 5% 2 3 4 2 3 3 4 6% 56%	1707
	11th to 20th	Day	17% 5% 2 3 4 2 3 3 4 6% 51%	1710
	21st to end	Day	13% 5% 3 4 4 2 4 3 4 6% 53%	2021
February	1st to 10th	Day	16% 6% 3 6% 4 2 4 3 4 6% 49%	1800
	11th to 20th	Day	16% 6% 2 5% 4 2 3 4 4 7% 46%	1749
	21st to end	Day	17% 5% 2 4 3 2 3 3 5% 5% 51%	1480
March	1st to 10th	Day	16% 8% 3 6% 5% 2 4 4 5% 6% 42%	1934
	11th to 20th	Day	14% 5% 2 6% 4 2 4 5% 5% 6% 47%	1980
	21st to end	Day	12% 5% 2 5% 4 2 4 5% 4 7% 49%	2178
April	1st to 10th	Day	13% 7% 3 5% 5% 3 4 3 5% 7% 45%	1980
	11th to 20th	Day	18% 6% 2 4 4 2 4 4 4 6% 45%	1987
	21st to end	Day	13% 5% 2 5% 4 3 4 5% 4 6% 49%	2281
May	1st to 10th	Day	13% 5% 3 6% 5% 3 5% 5% 7% 8% 41%	2340
	11th to 20th	Day	15% 8% 3 6% 5% 4 5% 4 4 6% 40%	2302
	21st to end	Day	15% 5% 3 5% 5% 4 6% 6% 7% 8% 35%	2531
June	1st to 10th	Day	5% 3 2 4 5% 3 6% 6% 7% 9% 50%	2340
	11th to 20th	Day	7% 3 2 4 4 3 5% 5% 7% 10% 50%	2340
	21st to end	Day	7% 4 2 5% 6% 4 6% 7% 7% 10% 42%	2340
July	1st to 10th	Day	10% 5% 3 5% 7% 4 6% 6% 6% 10% 38%	2340
	11th to 20th	Day	5% 2 2 3 4 3 5% 6% 7% 11% 53%	2340
	21st to end	Day	5% 2 2 4 3 2 4 5% 7% 11% 55%	2546
August	1st to 10th	Day	1 2 1 3 3 3 4 4 5% 9% 65%	2303
	11th to 20th	Day	6% 4 2 4 5% 3 4 5% 5% 10% 51%	2123
	21st to end	Day	5% 3 2 5% 6% 4 6% 6% 7% 10% 45%	2300
September	1st to 10th	Day	10% 6% 2 6% 5% 3 6% 4 5% 7% 47%	1980
	11th to 20th	Day	11% 6% 2 5% 5% 4 6% 5% 6% 8% 40%	1980
	21st to end	Day	9% 4 2 4 4 3 5% 5% 6% 7% 52%	1980
October	1st to 10th	Day	8% 4 2 3 4 3 5% 5% 5% 6% 56%	1980
	11th to 20th	Day	12% 5% 2 4 4 3 4 4 4 6% 53%	1876
	21st to end	Day	11% 4 2 3 4 3 3 4 4 5% 58%	1980
November	1st to 10th	Day	13% 6% 2 5% 4 2 3 4 6% 6% 48%	1858
	11th to 20th	Day	10% 5% 2 5% 4 2 4 5% 5% 5% 52%	1744
	21st to end	Day	15% 7% 2 5% 3 2 4 4 3 6% 49%	1710
December	1st to 10th	Day	13% 6% 3 4 3 3 3 4 5% 6% 50%	1710
	11th to 20th	Day	13% 7% 3 4 5% 3 4 4 5% 6% 46%	2161
	21st to end	Day	13% 6% 2 3 3 2 3 3 3 4 57%	3135
January	1st to 10th	Night	14% 4 2 4 2 2 3 3 4 6% 56%	2458
	11th to 20th	Night	14% 5% 2 3 3 2 3 3 4 6% 55%	2470
	21st to end	Night	15% 5% 2 4 4 3 3 4 4 6% 50%	2578
February	1st to 10th	Night	14% 6% 3 5% 3 2 3 3 4 6% 51%	2160
	11th to 20th	Night	16% 5% 2 4 3 1 3 4 3 6% 52%	2098
	21st to end	Night	16% 6% 2 6% 4 3 3 3 4 6% 48%	1776
March	1st to 10th	Night	14% 7% 2 5% 5% 2 3 4 5% 9% 45%	2026
	11th to 20th	Night	13% 6% 2 5% 4 3 4 3 5% 7% 48%	1980
	21st to end	Night	11% 5% 3 4 4 2 4 5% 5% 7% 52%	2178
April	1st to 10th	Night	8% 5% 2 4 5% 4 4 4 6% 8% 48%	1980
	11th to 20th	Night	15% 5% 2 5% 4 4 4 4 4 6% 47%	1917
	21st to end	Night	13% 6% 3 5% 3 2 4 3 4 6% 51%	1675
May	1st to 10th	Night	11% 4 2 5% 5% 3 4 4 5% 7% 50%	1620
	11th to 20th	Night	11% 5% 2 5% 5% 2 5% 4 5% 8% 49%	1593
	21st to end	Night	11% 5% 2 4 4 2 5% 5% 6% 11% 45%	1745
June	1st to 10th	Night	4 3 2 3 3 2 4 4 5% 9% 62%	1620
	11th to 20th	Night	4 2 1 2 3 2 4 4 5% 11% 62%	1620
	21st to end	Night	6% 3 2 3 4 2 4 5% 5% 10% 55%	1620
July	1st to 10th	Night	8% 3 2 3 4 2 4 5% 7% 11% 48%	1620
	11th to 20th	Night	3 2 1 3 2 2 3 4 5% 10% 66%	1620
	21st to end	Night	3 2 1 2 3 2 3 5% 6% 11% 61%	1772
August	1st to 10th	Night	1 1 2 2 2 3 3 5% 9% 72%	1631
	11th to 20th	Night	5% 3 2 4 4 2 3 5% 6% 10% 55%	1778
	21st to end	Night	6% 3 2 4 5% 2 5% 5% 6% 10% 52%	2055
September	1st to 10th	Night	7% 4 2 4 3 3 5% 5% 5% 8% 54%	1980
	11th to 20th	Night	10% 5% 3 4 4 3 4 5% 6% 8% 47%	1980
	21st to end	Night	8% 3 2 3 5% 3 4 5% 6% 8% 53%	1980
October	1st to 10th	Night	5% 3 1 3 3 3 3 4 4 7% 63%	1980
	11th to 20th	Night	12% 4 1 4 4 2 3 4 5% 7% 55%	2065
	21st to end	Night	13% 4 1 3 3 2 2 3 3 4 61%	2376
November	1st to 10th	Night	12% 5% 2 4 4 2 3 3 4 6% 56%	2220
	11th to 20th	Night	8% 6% 2 3 3 2 4 4 5% 6% 57%	2432
	21st to end	Night	15% 4 2 4 4 3 4 4 4 6% 48%	2470
December	1st to 10th	Night	12% 5% 2 4 3 2 3 4 5% 6% 54%	2470
	11th to 20th	Night	13% 9% 2 5% 4 2 4 3 4 6% 48%	3036
	21st to end	Night	15% 7% 2 3 3 2 2 3 3 5% 56%	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	32% 3 5% 21% 23% 16%	1708
	11th to 20th	Day	36% 4 6% 15% 22% 17%	1710
	21st to end	Day	34% 4 6% 12% 26% 17%	2021
February	1st to 10th	Day	39% 4 5% 13% 22% 17%	1800
	11th to 20th	Day	38% 4 7% 19% 18% 14%	1759
	21st to end	Day	37% 3 7% 16% 20% 17%	1480
March	1st to 10th	Day	43% 5% 9% 14% 18% 12%	1934
	11th to 20th	Day	38% 7% 7% 13% 19% 17%	1980
	21st to end	Day	35% 4 11% 17% 20% 13%	2178
April	1st to 10th	Day	40% 5% 9% 18% 17% 12%	1980
	11th to 20th	Day	41% 5% 7% 16% 20% 12%	1987
	21st to end	Day	37% 5% 6% 21% 20% 10%	2281
May	1st to 10th	Day	41% 7% 9% 16% 20% 7%	2340
	11th to 20th	Day	45% 6% 9% 17% 19% 4	2306
	21st to end	Day	43% 8% 13% 20% 15% 1	2531
June	1st to 10th	Day	27% 9% 13% 27% 20% 4	2340
	11th to 20th	Day	29% 6% 14% 26% 19% 6%	2340
	21st to end	Day	36% 9% 12% 23% 17% 4	2340
July	1st to 10th	Day	39% 9% 15% 25% 11% 1	2276
	11th to 20th	Day	24% 8% 18% 26% 21% 3	2271
	21st to end	Day	20% 9% 21% 34% 16% 1	2405
August	1st to 10th	Day	18% 6% 15% 38% 22% 1	2289
	11th to 20th	Day	29% 7% 16% 30% 13% 4	2123
	21st to end	Day	30% 11% 17% 26% 12% 4	2300
September	1st to 10th	Day	37% 7% 11% 21% 17% 8%	1980
	11th to 20th	Day	38% 10% 11% 19% 16% 5%	1980
	21st to end	Day	30% 6% 12% 21% 19% 12%	1980
October	1st to 10th	Day	27% 6% 11% 21% 24% 11%	1980
	11th to 20th	Day	33% 5% 8% 15% 21% 17%	1876
	21st to end	Day	29% 5% 5% 16% 24% 21%	1980
November	1st to 10th	Day	36% 5% 9% 19% 20% 11%	1858
	11th to 20th	Day	33% 5% 8% 18% 21% 15%	1744
	21st to end	Day	39% 4 7% 15% 22% 14%	1710
December	1st to 10th	Day	36% 4 9% 19% 23% 9%	1710
	11th to 20th	Day	38% 6% 8% 11% 22% 15%	2159
	21st to end	Day	33% 4 5% 14% 28% 17%	3135
January	1st to 10th	Night	31% 3 6% 17% 24% 19%	2458
	11th to 20th	Night	34% 3 6% 16% 23% 17%	2470
	21st to end	Night	36% 5% 4 14% 21% 19%	2578
February	1st to 10th	Night	37% 4 7% 13% 21% 18%	2160
	11th to 20th	Night	36% 4 7% 17% 19% 17%	2098
	21st to end	Night	39% 4 6% 13% 18% 18%	1776
March	1st to 10th	Night	38% 5% 9% 16% 21% 11%	2026
	11th to 20th	Night	38% 6% 10% 12% 19% 16%	1980
	21st to end	Night	33% 6% 11% 17% 18% 15%	2178
April	1st to 10th	Night	33% 6% 10% 19% 17% 14%	1980
	11th to 20th	Night	38% 5% 10% 13% 19% 15%	1917
	21st to end	Night	36% 6% 8% 20% 20% 10%	1675
May	1st to 10th	Night	34% 7% 11% 20% 19% 10%	1620
	11th to 20th	Night	34% 6% 13% 24% 18% 4	1594
	21st to end	Night	33% 8% 16% 27% 15% 1	1746
June	1st to 10th	Night	19% 7% 17% 31% 22% 4	1620
	11th to 20th	Night	18% 6% 16% 32% 22% 5%	1620
	21st to end	Night	25% 6% 19% 29% 16% 4	1620
July	1st to 10th	Night	29% 9% 22% 28% 11% 1	1575
	11th to 20th	Night	15% 8% 22% 32% 22% 2	1566
	21st to end	Night	15% 8% 27% 37% 12% 1	1673
August	1st to 10th	Night	10% 7% 21% 40% 21% 1	1621
	11th to 20th	Night	23% 9% 21% 30% 13% 4	1778
	21st to end	Night	26% 9% 21% 28% 13% 3	2055
September	1st to 10th	Night	27% 8% 14% 24% 19% 7%	1980
	11th to 20th	Night	34% 9% 14% 23% 15% 5%	1980
	21st to end	Night	28% 7% 15% 20% 19% 12%	1980
October	1st to 10th	Night	22% 5% 14% 26% 22% 12%	1980
	11th to 20th	Night	31% 5% 10% 15% 20% 19%	2065
	21st to end	Night	29% 3 6% 17% 23% 22%	2376
November	1st to 10th	Night	31% 5% 9% 19% 22% 14%	2220
	11th to 20th	Night	29% 4 9% 21% 20% 16%	2432
	21st to end	Night	37% 5% 8% 15% 20% 15%	2470
December	1st to 10th	Night	32% 4 10% 19% 23% 12%	2470
	11th to 20th	Night	40% 4 5% 11% 21% 19%	3037
	21st to end	Night	34% 3 5% 14% 29% 15%	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	18% 17% 38% 21% 5% 1	270
	11th to 20th	Day	24% 14% 30% 26% 6%	270
	21st to end	Day	16% 17% 38% 22% 6%	294
February	1st to 10th	Day	25% 15% 32% 23% 5%	240
	11th to 20th	Day	24% 18% 38% 18% 3	240
	21st to end	Day	26% 18% 38% 18% 1	198
March	1st to 10th	Day	20% 13% 44% 20% 3	240
	11th to 20th	Day	19% 17% 35% 24% 5%	240
	21st to end	Day	16% 17% 45% 17% 5%	264
April	1st to 10th	Day	17% 16% 46% 17% 4	240
	11th to 20th	Day	22% 16% 35% 21% 6%	265
	21st to end	Day	16% 16% 40% 23% 5%	541
May	1st to 10th	Day	12% 13% 41% 26% 7%	603
	11th to 20th	Day	19% 8% 29% 32% 11% 1	625
	21st to end	Day	15% 7% 26% 36% 15% 1	679
June	1st to 10th	Day	5% 3 18% 44% 25% 4	630
	11th to 20th	Day	7% 1 18% 52% 19% 2	630
	21st to end	Day	8% 2 12% 42% 29% 7%	630
July	1st to 10th	Day	8% 3 10% 38% 32% 10%	621
	11th to 20th	Day	3 6% 44% 39% 8%	618
	21st to end	Day	3 4 38% 45% 10%	684
August	1st to 10th	Day	2 4 42% 40% 11%	601
	11th to 20th	Day	8% 1 5% 36% 38% 12%	437
	21st to end	Day	5% 1 4 30% 39% 20%	419
September	1st to 10th	Day	10% 1 4 23% 43% 20%	270
	11th to 20th	Day	7% 1 5% 29% 43% 15%	270
	21st to end	Day	13% 1 5% 31% 37% 13%	270
October	1st to 10th	Day	6% 2 17% 34% 31% 10%	270
	11th to 20th	Day	13% 4 25% 34% 20% 4	270
	21st to end	Day	21% 9% 28% 25% 13% 4	297
November	1st to 10th	Day	20% 4 27% 34% 11% 4	270
	11th to 20th	Day	19% 8% 29% 33% 9% 3	270
	21st to end	Day	24% 17% 30% 19% 8% 2	270
December	1st to 10th	Day	15% 10% 35% 27% 10% 3	270
	11th to 20th	Day	18% 16% 34% 24% 8% 1	270
	21st to end	Day	15% 13% 39% 26% 5% 1	297
January	1st to 10th	Night	17% 10% 35% 31% 6% 1	950
	11th to 20th	Night	18% 12% 34% 31% 5%	950
	21st to end	Night	19% 10% 35% 30% 6%	910
February	1st to 10th	Night	18% 12% 37% 27% 6%	720
	11th to 20th	Night	20% 12% 41% 25% 3	704
	21st to end	Night	21% 13% 45% 20% 1	592
March	1st to 10th	Night	18% 11% 39% 29% 3	586
	11th to 20th	Night	17% 11% 38% 30% 4	540
	21st to end	Night	14% 12% 44% 26% 3	594
April	1st to 10th	Night	10% 11% 48% 28% 3	540
	11th to 20th	Night	15% 12% 43% 27% 3	533
	21st to end	Night	16% 9% 45% 23% 7%	540
May	1st to 10th	Night	12% 11% 43% 29% 5%	540
	11th to 20th	Night	12% 6% 38% 33% 11%	531
	21st to end	Night	12% 4 35% 38% 11%	584
June	1st to 10th	Night	4 2 24% 49% 20% 1	540
	11th to 20th	Night	4 1 34% 47% 13% 1	540
	21st to end	Night	7% 19% 48% 22% 3	540
July	1st to 10th	Night	9% 2 12% 50% 25% 3	525
	11th to 20th	Night	4 12% 57% 25% 3	522
	21st to end	Night	4 1 8% 57% 28% 3	591
August	1st to 10th	Night	1 8% 58% 29% 4	537
	11th to 20th	Night	6% 1 6% 53% 30% 4	534
	21st to end	Night	6% 1 5% 46% 36% 6%	594
September	1st to 10th	Night	9% 2 8% 43% 32% 6%	540
	11th to 20th	Night	12% 2 8% 39% 36% 4	540
	21st to end	Night	10% 1 12% 40% 33% 3	540
October	1st to 10th	Night	6% 2 15% 47% 28% 3	540
	11th to 20th	Night	12% 4 24% 40% 17% 2	625
	21st to end	Night	14% 8% 29% 29% 19% 1	792
November	1st to 10th	Night	12% 5% 24% 41% 16% 1	740
	11th to 20th	Night	12% 7% 29% 37% 13% 1	912
	21st to end	Night	17% 10% 33% 29% 10%	950
December	1st to 10th	Night	16% 8% 30% 37% 9%	950
	11th to 20th	Night	21% 9% 31% 33% 7%	950
	21st to end	Night	17% 11% 32% 33% 6%	1045

Page generated at 2024-01-28 04:26:33. Version ac07

Copyright 2024 Attilla Danko