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 2024-11-02.

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% 9% 3 7% 5% 5% 5% 4 6% 7% 35%	101129
	Night	15% 9% 3 7% 4 4 4 4 5% 7% 37%	97793
Transparency	Day	46% 8% 12% 20% 12% 2	100942
	Night	45% 8% 12% 20% 13% 2	97650
Seeing	Day	18% 14% 22% 23% 16% 6%	15037
	Night	18% 11% 21% 30% 17% 2	25082

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	15% 15% 10% 11% 3 3 3 3 5% 5% 27%	2836
	11th to 20th	Day	14% 18% 8% 11% 7% 5% 3 2 4 4 25%	2840
	21st to end	Day	18% 18% 4 7% 4 4 4 3 5% 4 29%	3124
February	1st to 10th	Day	18% 12% 4 9% 5% 4 4 3 5% 5% 31%	1754
	11th to 20th	Day	21% 14% 5% 8% 4 4 2 3 4 6% 29%	1848
	21st to end	Day	22% 12% 3 7% 4 4 2 3 4 6% 33%	1570
March	1st to 10th	Day	19% 13% 3 6% 4 4 3 3 4 6% 34%	3367
	11th to 20th	Day	15% 8% 3 5% 4 3 4 3 4 5% 46%	3480
	21st to end	Day	18% 10% 2 6% 4 4 4 3 6% 6% 37%	3815
April	1st to 10th	Day	13% 9% 2 5% 5% 4 4 4 7% 8% 38%	2090
	11th to 20th	Day	16% 8% 2 6% 4 3 5% 4 5% 6% 41%	2296
	21st to end	Day	17% 7% 2 6% 5% 5% 5% 4 5% 6% 39%	2470
May	1st to 10th	Day	21% 9% 3 7% 5% 5% 5% 4 6% 7% 29%	4082
	11th to 20th	Day	19% 8% 3 8% 5% 5% 5% 4 5% 6% 30%	4081
	21st to end	Day	11% 6% 2 6% 5% 5% 5% 4 8% 11% 37%	4476
June	1st to 10th	Day	12% 6% 2 6% 5% 6% 6% 5% 7% 8% 35%	2470
	11th to 20th	Day	9% 5% 2 8% 5% 7% 7% 5% 9% 10% 33%	2470
	21st to end	Day	11% 7% 2 6% 5% 5% 7% 6% 8% 9% 34%	2470
July	1st to 10th	Day	8% 4 2 6% 6% 6% 6% 6% 9% 12% 34%	4120
	11th to 20th	Day	12% 6% 3 6% 6% 5% 6% 5% 7% 9% 37%	4120
	21st to end	Day	18% 9% 4 10% 8% 7% 7% 5% 7% 7% 18%	4466
August	1st to 10th	Day	13% 6% 3 7% 6% 6% 7% 6% 8% 11% 28%	4104
	11th to 20th	Day	13% 5% 2 7% 5% 6% 6% 5% 8% 10% 33%	4044
	21st to end	Day	7% 4 1 4 4 4 4 5% 6% 7% 53%	4259
September	1st to 10th	Day	11% 5% 2 7% 5% 5% 5% 5% 6% 7% 42%	2090
	11th to 20th	Day	15% 6% 2 6% 5% 5% 5% 3 6% 6% 40%	2090
	21st to end	Day	15% 6% 2 5% 5% 4 5% 4 6% 8% 39%	2090
October	1st to 10th	Day	14% 5% 2 5% 4 3 4 3 4 7% 48%	2039
	11th to 20th	Day	15% 6% 2 4 3 3 3 3 5% 7% 49%	1900
	21st to end	Day	17% 9% 2 4 3 3 3 2 4 6% 47%	2090
November	1st to 10th	Day	13% 6% 3 5% 4 3 3 2 4 6% 52%	1771
	11th to 20th	Day	11% 9% 3 5% 4 5% 4 3 5% 7% 44%	1710
	21st to end	Day	15% 8% 4 6% 4 3 3 4 5% 6% 43%	1710
December	1st to 10th	Day	19% 14% 3 7% 5% 4 4 3 4 5% 31%	1710
	11th to 20th	Day	16% 15% 3 7% 3 3 4 4 5% 8% 33%	2153
	21st to end	Day	14% 15% 5% 7% 5% 5% 5% 4 5% 5% 28%	3124
January	1st to 10th	Night	19% 17% 6% 9% 4 3 3 3 4 5% 27%	4109
	11th to 20th	Night	18% 13% 4 9% 6% 4 4 3 4 4 32%	4120
	21st to end	Night	21% 11% 4 7% 5% 4 4 3 4 5% 32%	4532
February	1st to 10th	Night	17% 12% 3 7% 3 4 5% 3 4 6% 36%	2423
	11th to 20th	Night	20% 12% 4 9% 5% 3 4 3 4 5% 30%	2218
	21st to end	Night	21% 12% 4 9% 3 3 3 3 4 6% 31%	1884
March	1st to 10th	Night	24% 14% 2 6% 4 4 4 2 4 5% 32%	3484
	11th to 20th	Night	16% 7% 4 5% 3 3 4 3 5% 6% 45%	3480
	21st to end	Night	15% 7% 2 5% 5% 4 5% 4 6% 7% 42%	3817
April	1st to 10th	Night	14% 9% 3 5% 4 4 4 3 4 8% 41%	2090
	11th to 20th	Night	15% 8% 2 6% 4 4 4 4 6% 6% 42%	1846
	21st to end	Night	15% 7% 3 6% 5% 5% 4 3 5% 6% 42%	1710
May	1st to 10th	Night	18% 8% 3 7% 6% 5% 4 4 6% 7% 31%	2813
	11th to 20th	Night	20% 7% 3 6% 5% 4 4 4 6% 8% 33%	2812
	21st to end	Night	13% 7% 2 6% 4 5% 5% 4 7% 9% 38%	3079
June	1st to 10th	Night	11% 6% 2 7% 6% 5% 5% 4 7% 10% 38%	1710
	11th to 20th	Night	7% 5% 2 7% 5% 5% 6% 5% 9% 12% 39%	1710
	21st to end	Night	10% 6% 2 6% 5% 6% 5% 5% 7% 11% 38%	1710
July	1st to 10th	Night	11% 6% 3 6% 5% 5% 6% 6% 8% 12% 33%	2840
	11th to 20th	Night	9% 6% 3 6% 4 4 5% 5% 7% 10% 40%	2840
	21st to end	Night	14% 10% 5% 11% 7% 5% 5% 5% 7% 8% 22%	3087
August	1st to 10th	Night	12% 6% 3 7% 5% 5% 6% 5% 8% 11% 34%	2825
	11th to 20th	Night	14% 7% 3 6% 5% 5% 5% 4 6% 7% 38%	2785
	21st to end	Night	7% 3 1 4 3 4 4 4 8% 10% 52%	3359
September	1st to 10th	Night	12% 6% 2 6% 5% 5% 4 3 5% 7% 44%	2090
	11th to 20th	Night	16% 5% 2 6% 4 4 4 3 6% 8% 42%	2090
	21st to end	Night	14% 6% 2 5% 4 4 3 2 5% 6% 47%	2090
October	1st to 10th	Night	16% 6% 2 5% 3 3 3 3 4 6% 50%	2139
	11th to 20th	Night	16% 7% 2 4 2 3 3 3 4 6% 49%	2280
	21st to end	Night	15% 7% 2 5% 3 2 4 3 5% 7% 48%	2508
November	1st to 10th	Night	15% 7% 2 4 3 3 3 3 5% 5% 50%	2329
	11th to 20th	Night	14% 9% 2 5% 4 4 3 3 6% 6% 45%	2470
	21st to end	Night	13% 10% 2 5% 3 3 4 3 5% 6% 46%	2470
December	1st to 10th	Night	19% 12% 5% 9% 4 4 4 3 5% 6% 30%	2470
	11th to 20th	Night	18% 12% 4 10% 4 3 4 3 4 5% 34%	3042
	21st to end	Night	15% 16% 6% 8% 5% 3 5% 4 6% 7% 24%	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	56% 7% 6% 16% 12% 2	2837
	11th to 20th	Day	63% 5% 7% 13% 11% 1	2840
	21st to end	Day	59% 5% 7% 15% 15%	3124
February	1st to 10th	Day	55% 6% 7% 16% 15% 1	1754
	11th to 20th	Day	58% 5% 7% 15% 13% 2	1858
	21st to end	Day	54% 5% 8% 15% 14% 5%	1570
March	1st to 10th	Day	50% 6% 8% 18% 15% 3	3367
	11th to 20th	Day	40% 6% 8% 23% 19% 4	3480
	21st to end	Day	45% 7% 10% 24% 12% 2	3815
April	1st to 10th	Day	42% 7% 12% 22% 14% 3	2090
	11th to 20th	Day	41% 7% 10% 19% 19% 4	2296
	21st to end	Day	45% 8% 10% 23% 11% 2	2470
May	1st to 10th	Day	52% 10% 12% 18% 8% 1	4120
	11th to 20th	Day	52% 9% 12% 21% 5% 1	4085
	21st to end	Day	36% 12% 18% 20% 12% 2	4489
June	1st to 10th	Day	42% 12% 16% 18% 11% 1	2470
	11th to 20th	Day	42% 13% 15% 16% 13% 1	2470
	21st to end	Day	42% 11% 15% 18% 13% 2	2470
July	1st to 10th	Day	38% 12% 22% 18% 9% 1	4055
	11th to 20th	Day	42% 9% 18% 24% 6% 1	4051
	21st to end	Day	61% 10% 10% 12% 6%	4324
August	1st to 10th	Day	47% 9% 18% 20% 6%	4091
	11th to 20th	Day	42% 9% 17% 22% 9% 1	4083
	21st to end	Day	28% 7% 16% 36% 11% 1	4259
September	1st to 10th	Day	39% 11% 13% 19% 14% 4	2090
	11th to 20th	Day	42% 9% 10% 21% 15% 2	2090
	21st to end	Day	42% 8% 14% 18% 14% 4	2090
October	1st to 10th	Day	35% 6% 10% 21% 22% 5%	2039
	11th to 20th	Day	35% 6% 10% 24% 19% 6%	1900
	21st to end	Day	39% 5% 8% 24% 19% 6%	2090
November	1st to 10th	Day	35% 5% 8% 19% 28% 5%	1771
	11th to 20th	Day	40% 5% 8% 20% 22% 5%	1710
	21st to end	Day	42% 6% 8% 21% 19% 4	1710
December	1st to 10th	Day	55% 6% 9% 17% 11% 2	1710
	11th to 20th	Day	48% 5% 11% 16% 16% 3	2150
	21st to end	Day	55% 7% 9% 21% 8% 1	3124
January	1st to 10th	Night	59% 7% 7% 14% 11% 3	4109
	11th to 20th	Night	53% 7% 8% 14% 17% 2	4120
	21st to end	Night	55% 6% 9% 14% 15% 1	4532
February	1st to 10th	Night	50% 5% 10% 19% 14% 2	2423
	11th to 20th	Night	56% 6% 8% 16% 11% 4	2219
	21st to end	Night	54% 6% 9% 17% 11% 4	1884
March	1st to 10th	Night	54% 7% 9% 15% 13% 2	3484
	11th to 20th	Night	38% 7% 12% 22% 14% 8%	3480
	21st to end	Night	40% 8% 10% 25% 14% 2	3817
April	1st to 10th	Night	41% 8% 13% 21% 14% 3	2090
	11th to 20th	Night	40% 8% 10% 20% 17% 5%	1846
	21st to end	Night	42% 6% 13% 25% 12% 1	1710
May	1st to 10th	Night	50% 11% 13% 18% 7% 1	2840
	11th to 20th	Night	47% 11% 15% 22% 5% 1	2813
	21st to end	Night	36% 14% 18% 21% 10% 1	3087
June	1st to 10th	Night	39% 12% 17% 19% 12% 1	1710
	11th to 20th	Night	34% 13% 19% 22% 10% 1	1710
	21st to end	Night	38% 13% 15% 19% 12% 3	1710
July	1st to 10th	Night	42% 10% 20% 19% 8% 1	2795
	11th to 20th	Night	36% 9% 22% 25% 5% 2	2786
	21st to end	Night	56% 10% 13% 16% 5%	2988
August	1st to 10th	Night	43% 8% 21% 21% 5%	2814
	11th to 20th	Night	43% 7% 18% 24% 8%	2812
	21st to end	Night	26% 7% 15% 39% 11% 1	3359
September	1st to 10th	Night	39% 9% 14% 20% 15% 4	2090
	11th to 20th	Night	40% 9% 14% 20% 16% 1	2090
	21st to end	Night	38% 7% 13% 22% 18% 2	2090
October	1st to 10th	Night	37% 6% 10% 20% 23% 4	2139
	11th to 20th	Night	36% 6% 10% 25% 19% 5%	2280
	21st to end	Night	36% 6% 6% 23% 22% 7%	2508
November	1st to 10th	Night	36% 5% 10% 19% 24% 6%	2329
	11th to 20th	Night	39% 5% 7% 20% 22% 6%	2470
	21st to end	Night	40% 6% 7% 25% 19% 3	2470
December	1st to 10th	Night	56% 6% 9% 16% 10% 3	2470
	11th to 20th	Night	52% 6% 7% 16% 16% 3	3044
	21st to end	Night	56% 9% 10% 15% 10% 1	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	26% 31% 27% 13% 2	270
	11th to 20th	Day	34% 28% 23% 15% 1	270
	21st to end	Day	25% 31% 30% 11% 2	297
February	1st to 10th	Day	27% 25% 32% 13% 3	270
	11th to 20th	Day	39% 32% 21% 6% 1	270
	21st to end	Day	40% 21% 30% 8% 1	225
March	1st to 10th	Day	23% 24% 27% 18% 7% 1	414
	11th to 20th	Day	25% 26% 27% 17% 3 1	460
	21st to end	Day	25% 24% 24% 19% 7%	506
April	1st to 10th	Day	22% 22% 27% 18% 9% 2	460
	11th to 20th	Day	21% 18% 26% 22% 10% 2	452
	21st to end	Day	22% 15% 29% 18% 12% 3	460
May	1st to 10th	Day	22% 20% 25% 18% 11% 4	463
	11th to 20th	Day	19% 10% 23% 28% 15% 6%	487
	21st to end	Day	14% 9% 21% 24% 22% 11%	529
June	1st to 10th	Day	13% 6% 23% 28% 22% 8%	490
	11th to 20th	Day	9% 7% 18% 29% 26% 11%	490
	21st to end	Day	14% 8% 21% 25% 23% 9%	490
July	1st to 10th	Day	12% 5% 15% 23% 29% 15%	485
	11th to 20th	Day	9% 4 14% 32% 28% 13%	484
	21st to end	Day	14% 4 14% 30% 26% 12%	532
August	1st to 10th	Day	15% 5% 17% 26% 24% 13%	486
	11th to 20th	Day	13% 3 17% 29% 26% 11%	479
	21st to end	Day	12% 3 10% 26% 29% 21%	539
September	1st to 10th	Day	9% 5% 14% 28% 30% 14%	490
	11th to 20th	Day	15% 4 14% 25% 30% 13%	490
	21st to end	Day	16% 8% 18% 29% 23% 5%	490
October	1st to 10th	Day	16% 7% 20% 29% 20% 8%	490
	11th to 20th	Day	15% 17% 20% 27% 18% 3	490
	21st to end	Day	20% 12% 22% 29% 14% 3	539
November	1st to 10th	Day	16% 18% 24% 26% 12% 4	363
	11th to 20th	Day	17% 25% 26% 25% 7%	270
	21st to end	Day	19% 19% 30% 25% 6% 1	270
December	1st to 10th	Day	27% 22% 34% 14% 3	270
	11th to 20th	Day	24% 19% 30% 21% 5%	270
	21st to end	Day	23% 24% 34% 13% 7%	297
January	1st to 10th	Night	24% 22% 26% 25% 4	760
	11th to 20th	Night	27% 19% 26% 24% 4	760
	21st to end	Night	22% 19% 33% 23% 3	836
February	1st to 10th	Night	22% 17% 30% 28% 3	760
	11th to 20th	Night	28% 23% 30% 18% 1	743
	21st to end	Night	26% 24% 28% 19% 2	628
March	1st to 10th	Night	22% 17% 29% 27% 4	760
	11th to 20th	Night	24% 19% 28% 21% 7% 1	760
	21st to end	Night	21% 13% 31% 27% 8%	836
April	1st to 10th	Night	19% 19% 26% 28% 8%	760
	11th to 20th	Night	16% 16% 28% 28% 11% 1	655
	21st to end	Night	17% 9% 27% 36% 9% 1	570
May	1st to 10th	Night	17% 11% 26% 30% 15% 1	570
	11th to 20th	Night	16% 7% 22% 34% 20% 2	561
	21st to end	Night	10% 3 17% 35% 31% 4	617
June	1st to 10th	Night	10% 4 13% 41% 29% 4	570
	11th to 20th	Night	6% 3 13% 42% 31% 4	570
	21st to end	Night	12% 3 11% 39% 32% 3	570
July	1st to 10th	Night	12% 3 8% 29% 43% 5%	555
	11th to 20th	Night	11% 2 7% 30% 42% 7%	552
	21st to end	Night	10% 4 6% 36% 36% 8%	624
August	1st to 10th	Night	10% 3 8% 34% 40% 5%	567
	11th to 20th	Night	12% 3 8% 36% 36% 4	564
	21st to end	Night	12% 2 7% 33% 39% 7%	677
September	1st to 10th	Night	13% 3 9% 34% 35% 6%	760
	11th to 20th	Night	16% 4 11% 30% 34% 5%	760
	21st to end	Night	16% 5% 16% 36% 25% 3	760
October	1st to 10th	Night	17% 5% 16% 30% 26% 6%	760
	11th to 20th	Night	18% 8% 21% 33% 16% 2	760
	21st to end	Night	18% 10% 20% 35% 14% 2	836
November	1st to 10th	Night	17% 7% 21% 36% 17% 2	745
	11th to 20th	Night	18% 14% 21% 34% 11% 1	760
	21st to end	Night	18% 15% 24% 31% 11% 1	760
December	1st to 10th	Night	25% 16% 26% 27% 6%	760
	11th to 20th	Night	24% 14% 26% 30% 6% 1	760
	21st to end	Night	25% 17% 26% 28% 4	836

Page generated at 2024-10-30 01:22:58. Version ac07

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