Tryon
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tryon clear sky chart from 2005-11-06 to 2024-10-25.

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	8% 6% 2 5% 4 3 4 3 5% 7% 53%	101114
	Night	8% 6% 2 6% 4 4 4 3 5% 7% 51%	97872
Transparency	Day	29% 6% 13% 28% 19% 4	100860
	Night	31% 6% 14% 27% 18% 4	97717
Seeing	Day	10% 7% 31% 32% 16% 3	15766
	Night	10% 8% 37% 36% 9%	25652

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	5% 9% 4 7% 4 3 3 2 4 6% 52%	2538
	11th to 20th	Day	4 9% 3 6% 4 4 5% 5% 7% 8% 44%	2540
	21st to end	Day	5% 5% 3 6% 3 4 4 3 6% 8% 53%	2803
February	1st to 10th	Day	7% 9% 4 9% 5% 5% 4 3 5% 7% 41%	1833
	11th to 20th	Day	6% 9% 3 7% 5% 4 4 4 4 7% 47%	1849
	21st to end	Day	8% 7% 3 5% 3 2 3 2 5% 6% 55%	1570
March	1st to 10th	Day	8% 5% 2 5% 3 3 3 4 5% 7% 57%	3130
	11th to 20th	Day	8% 7% 1 4 3 3 3 3 4 6% 58%	3375
	21st to end	Day	11% 9% 3 7% 4 4 3 3 6% 7% 43%	3941
April	1st to 10th	Day	11% 7% 2 4 3 4 3 4 5% 6% 51%	2280
	11th to 20th	Day	13% 9% 3 6% 4 4 4 3 5% 6% 44%	2270
	21st to end	Day	14% 6% 2 5% 4 3 4 4 5% 6% 47%	2470
May	1st to 10th	Day	12% 5% 2 5% 4 4 4 4 6% 7% 47%	4120
	11th to 20th	Day	11% 5% 2 5% 3 4 4 3 5% 8% 51%	4082
	21st to end	Day	13% 5% 1 5% 4 4 4 4 5% 7% 47%	4734
June	1st to 10th	Day	7% 4 1 4 3 3 4 3 7% 9% 56%	2660
	11th to 20th	Day	8% 5% 2 4 4 3 4 4 6% 7% 54%	2660
	21st to end	Day	4 2 1 4 3 3 3 4 6% 8% 61%	2660
July	1st to 10th	Day	7% 3 2 5% 4 3 4 4 6% 8% 54%	4430
	11th to 20th	Day	4 3 1 5% 4 4 5% 5% 7% 10% 52%	4430
	21st to end	Day	3 3 1 4 3 4 4 4 7% 9% 58%	4777
August	1st to 10th	Day	10% 5% 2 5% 4 3 4 4 7% 9% 48%	4103
	11th to 20th	Day	11% 5% 2 6% 4 4 5% 4 6% 8% 46%	3986
	21st to end	Day	4 3 1 5% 3 4 4 3 5% 7% 62%	4180
September	1st to 10th	Day	8% 4 1 3 3 3 3 3 6% 7% 60%	2271
	11th to 20th	Day	7% 4 1 4 3 2 3 3 6% 6% 60%	2090
	21st to end	Day	8% 5% 1 4 2 2 3 2 4 4 63%	2090
October	1st to 10th	Day	11% 6% 1 4 2 2 2 2 3 6% 60%	2090
	11th to 20th	Day	8% 5% 1 4 3 3 3 2 5% 5% 60%	1886
	21st to end	Day	10% 6% 2 5% 3 3 3 2 4 6% 55%	1823
November	1st to 10th	Day	4 6% 1 4 3 3 4 4 7% 7% 57%	1673
	11th to 20th	Day	4 5% 2 5% 4 3 3 3 5% 6% 59%	1710
	21st to end	Day	7% 7% 2 4 2 3 3 4 5% 5% 58%	1710
December	1st to 10th	Day	6% 8% 2 6% 5% 4 3 4 5% 7% 51%	1630
	11th to 20th	Day	5% 6% 2 5% 4 3 3 3 5% 7% 57%	1926
	21st to end	Day	10% 11% 4 7% 4 4 4 3 4 6% 42%	2794
January	1st to 10th	Night	5% 10% 2 10% 6% 4 5% 4 6% 7% 42%	4417
	11th to 20th	Night	3 8% 4 8% 4 3 4 4 5% 6% 52%	4430
	21st to end	Night	3 5% 3 8% 5% 5% 5% 3 5% 6% 51%	4863
February	1st to 10th	Night	8% 10% 3 8% 5% 3 4 4 4 7% 43%	2365
	11th to 20th	Night	4 8% 3 7% 6% 5% 4 4 6% 8% 45%	2218
	21st to end	Night	4 7% 2 6% 5% 4 4 4 6% 7% 52%	1884
March	1st to 10th	Night	8% 7% 2 5% 3 3 4 2 5% 5% 55%	3734
	11th to 20th	Night	8% 7% 2 5% 3 3 3 3 4 6% 56%	3586
	21st to end	Night	10% 9% 2 8% 4 4 5% 4 5% 8% 41%	3677
April	1st to 10th	Night	11% 8% 2 5% 4 4 4 3 6% 7% 46%	1900
	11th to 20th	Night	13% 8% 2 4 4 4 3 4 5% 7% 47%	1858
	21st to end	Night	13% 7% 2 7% 4 3 4 4 5% 7% 45%	1710
May	1st to 10th	Night	16% 6% 2 6% 4 3 5% 4 5% 7% 43%	2850
	11th to 20th	Night	10% 5% 2 5% 4 4 4 4 7% 8% 48%	2823
	21st to end	Night	13% 6% 2 5% 4 4 4 4 6% 8% 44%	2837
June	1st to 10th	Night	7% 5% 2 4 3 3 5% 4 6% 10% 51%	1520
	11th to 20th	Night	9% 6% 2 5% 3 3 4 5% 7% 9% 47%	1520
	21st to end	Night	4 3 1 6% 5% 5% 5% 5% 7% 11% 49%	1520
July	1st to 10th	Night	10% 4 1 5% 4 3 3 3 5% 6% 55%	2540
	11th to 20th	Night	5% 4 2 5% 4 4 5% 3 8% 9% 51%	2540
	21st to end	Night	3 3 1 4 4 4 4 4 7% 9% 57%	2783
August	1st to 10th	Night	7% 5% 3 7% 4 4 5% 4 8% 10% 43%	2836
	11th to 20th	Night	11% 5% 2 6% 4 4 5% 4 6% 8% 45%	2850
	21st to end	Night	4 4 1 5% 3 4 4 4 7% 9% 54%	3487
September	1st to 10th	Night	8% 4 1 4 3 3 3 3 6% 6% 60%	1909
	11th to 20th	Night	6% 4 1 4 3 4 3 3 5% 7% 59%	2090
	21st to end	Night	9% 3 1 4 3 2 2 3 4 6% 62%	2090
October	1st to 10th	Night	12% 4 1 4 3 3 2 3 4 5% 58%	2090
	11th to 20th	Night	8% 4 1 3 2 3 3 3 4 6% 62%	2271
	21st to end	Night	9% 6% 2 4 3 2 3 3 4 5% 59%	2639
November	1st to 10th	Night	4 5% 2 3 4 3 3 4 5% 7% 59%	2405
	11th to 20th	Night	5% 4 1 4 4 4 5% 3 6% 7% 55%	2470
	21st to end	Night	6% 6% 1 4 4 3 4 3 5% 8% 56%	2470
December	1st to 10th	Night	5% 7% 2 6% 4 3 3 3 5% 8% 55%	2546
	11th to 20th	Night	5% 5% 2 5% 4 3 4 3 5% 7% 56%	3271
	21st to end	Night	12% 11% 3 5% 4 3 4 3 4 6% 45%	4873

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	35% 4 10% 33% 17% 1	2539
	11th to 20th	Day	33% 10% 12% 26% 16% 4	2540
	21st to end	Day	28% 6% 18% 29% 15% 3	2803
February	1st to 10th	Day	42% 5% 14% 22% 13% 4	1833
	11th to 20th	Day	37% 6% 11% 24% 18% 4	1859
	21st to end	Day	29% 4 13% 31% 18% 5%	1570
March	1st to 10th	Day	25% 6% 9% 28% 27% 5%	3130
	11th to 20th	Day	27% 5% 14% 33% 19% 1	3375
	21st to end	Day	38% 8% 21% 26% 7% 1	3941
April	1st to 10th	Day	33% 5% 16% 28% 15% 3	2280
	11th to 20th	Day	39% 7% 13% 22% 16% 3	2273
	21st to end	Day	36% 6% 13% 27% 16% 1	2470
May	1st to 10th	Day	31% 9% 15% 22% 17% 6%	4120
	11th to 20th	Day	30% 8% 16% 28% 16% 1	4086
	21st to end	Day	34% 8% 16% 28% 11% 3	4734
June	1st to 10th	Day	24% 7% 21% 33% 13% 2	2660
	11th to 20th	Day	29% 6% 14% 27% 18% 6%	2660
	21st to end	Day	18% 7% 14% 33% 23% 5%	2660
July	1st to 10th	Day	26% 6% 11% 26% 27% 4	4361
	11th to 20th	Day	25% 7% 12% 31% 21% 5%	4355
	21st to end	Day	19% 7% 14% 26% 25% 10%	4626
August	1st to 10th	Day	31% 7% 14% 27% 18% 3	4090
	11th to 20th	Day	36% 7% 14% 23% 19% 2	4025
	21st to end	Day	22% 5% 16% 22% 23% 12%	4179
September	1st to 10th	Day	24% 4 10% 28% 24% 10%	2271
	11th to 20th	Day	22% 5% 11% 30% 26% 6%	2090
	21st to end	Day	25% 3 8% 30% 28% 6%	2090
October	1st to 10th	Day	28% 3 9% 26% 27% 6%	2090
	11th to 20th	Day	27% 5% 10% 30% 21% 7%	1886
	21st to end	Day	30% 5% 9% 31% 19% 6%	1823
November	1st to 10th	Day	24% 6% 15% 29% 21% 5%	1673
	11th to 20th	Day	25% 4 11% 29% 26% 5%	1710
	21st to end	Day	27% 4 12% 30% 21% 5%	1710
December	1st to 10th	Day	32% 5% 12% 30% 18% 3	1630
	11th to 20th	Day	27% 4 15% 37% 16% 1	1924
	21st to end	Day	43% 5% 9% 28% 13% 2	2794
January	1st to 10th	Night	40% 5% 12% 27% 15% 1	4417
	11th to 20th	Night	31% 6% 16% 28% 17% 1	4430
	21st to end	Night	33% 6% 15% 29% 17% 1	4863
February	1st to 10th	Night	40% 7% 13% 23% 14% 3	2365
	11th to 20th	Night	35% 6% 14% 28% 14% 3	2218
	21st to end	Night	31% 5% 13% 26% 19% 6%	1884
March	1st to 10th	Night	30% 5% 10% 22% 29% 4	3734
	11th to 20th	Night	30% 4 11% 31% 22% 2	3586
	21st to end	Night	39% 10% 18% 25% 7% 1	3677
April	1st to 10th	Night	36% 6% 14% 24% 16% 4	1900
	11th to 20th	Night	37% 6% 13% 25% 16% 3	1858
	21st to end	Night	37% 7% 14% 27% 13% 1	1710
May	1st to 10th	Night	37% 8% 14% 23% 14% 4	2850
	11th to 20th	Night	30% 10% 17% 32% 9% 1	2824
	21st to end	Night	37% 9% 17% 27% 8% 2	2838
June	1st to 10th	Night	26% 10% 23% 27% 12% 2	1520
	11th to 20th	Night	32% 7% 18% 25% 12% 6%	1520
	21st to end	Night	27% 8% 17% 28% 19% 2	1520
July	1st to 10th	Night	30% 6% 14% 31% 18% 2	2500
	11th to 20th	Night	27% 7% 16% 27% 19% 3	2492
	21st to end	Night	21% 7% 15% 25% 24% 8%	2696
August	1st to 10th	Night	35% 7% 18% 26% 13% 2	2826
	11th to 20th	Night	36% 7% 14% 25% 15% 2	2877
	21st to end	Night	26% 6% 14% 25% 19% 10%	3487
September	1st to 10th	Night	24% 4 10% 25% 28% 8%	1909
	11th to 20th	Night	25% 6% 12% 28% 23% 7%	2090
	21st to end	Night	25% 4 8% 28% 28% 6%	2090
October	1st to 10th	Night	28% 5% 8% 27% 27% 5%	2090
	11th to 20th	Night	24% 4 9% 30% 24% 8%	2271
	21st to end	Night	28% 5% 12% 24% 23% 7%	2639
November	1st to 10th	Night	23% 5% 12% 29% 23% 7%	2405
	11th to 20th	Night	26% 5% 13% 27% 24% 5%	2470
	21st to end	Night	27% 5% 11% 29% 23% 4	2470
December	1st to 10th	Night	29% 4 15% 29% 19% 4	2546
	11th to 20th	Night	27% 4 12% 37% 18% 1	3272
	21st to end	Night	40% 5% 11% 29% 13% 2	4873

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	9% 6% 42% 28% 13% 2	270
	11th to 20th	Day	10% 12% 36% 33% 7% 1	270
	21st to end	Day	9% 9% 49% 19% 10% 4	297
February	1st to 10th	Day	10% 11% 50% 24% 5%	270
	11th to 20th	Day	12% 6% 48% 24% 7% 2	270
	21st to end	Day	11% 13% 50% 22% 4	225
March	1st to 10th	Day	10% 10% 40% 25% 13% 2	270
	11th to 20th	Day	15% 6% 33% 33% 11% 1	270
	21st to end	Day	21% 9% 39% 22% 7% 2	373
April	1st to 10th	Day	15% 14% 37% 25% 8%	460
	11th to 20th	Day	16% 15% 36% 26% 7%	471
	21st to end	Day	16% 12% 34% 25% 12% 2	650
May	1st to 10th	Day	14% 10% 31% 32% 12% 2	653
	11th to 20th	Day	19% 7% 29% 27% 16% 3	675
	21st to end	Day	16% 7% 31% 28% 17% 2	734
June	1st to 10th	Day	7% 4 23% 35% 22% 9%	680
	11th to 20th	Day	8% 7% 35% 33% 15% 2	680
	21st to end	Day	5% 6% 28% 39% 20% 3	680
July	1st to 10th	Day	8% 4 24% 35% 25% 5%	671
	11th to 20th	Day	5% 2 21% 42% 24% 6%	668
	21st to end	Day	6% 2 18% 43% 28% 4	739
August	1st to 10th	Day	8% 4 16% 42% 26% 4	676
	11th to 20th	Day	7% 3 24% 39% 24% 3	636
	21st to end	Day	6% 2 25% 39% 22% 7%	539
September	1st to 10th	Day	7% 4 24% 40% 19% 6%	481
	11th to 20th	Day	3 5% 20% 39% 24% 9%	300
	21st to end	Day	13% 8% 25% 32% 18% 4	300
October	1st to 10th	Day	14% 5% 22% 31% 21% 7%	300
	11th to 20th	Day	8% 11% 37% 29% 14% 2	300
	21st to end	Day	13% 14% 27% 28% 15% 3	311
November	1st to 10th	Day	7% 10% 39% 26% 14% 4	270
	11th to 20th	Day	7% 11% 37% 33% 9% 2	270
	21st to end	Day	15% 6% 39% 27% 9% 4	270
December	1st to 10th	Day	9% 9% 44% 27% 8% 3	270
	11th to 20th	Day	11% 11% 40% 28% 9% 1	270
	21st to end	Day	14% 14% 41% 26% 4 1	297
January	1st to 10th	Night	9% 11% 39% 31% 8% 1	950
	11th to 20th	Night	8% 13% 40% 32% 6% 1	950
	21st to end	Night	7% 10% 44% 30% 8% 1	1045
February	1st to 10th	Night	12% 10% 44% 27% 6%	845
	11th to 20th	Night	7% 9% 50% 29% 5%	744
	21st to end	Night	9% 10% 48% 28% 4	628
March	1st to 10th	Night	10% 11% 42% 32% 5%	760
	11th to 20th	Night	11% 8% 43% 32% 5% 1	637
	21st to end	Night	14% 7% 41% 31% 7%	627
April	1st to 10th	Night	14% 12% 44% 27% 2	570
	11th to 20th	Night	18% 12% 42% 26% 3	563
	21st to end	Night	15% 11% 35% 31% 8%	570
May	1st to 10th	Night	13% 7% 35% 36% 9%	570
	11th to 20th	Night	18% 7% 32% 32% 10%	561
	21st to end	Night	16% 6% 33% 35% 10%	617
June	1st to 10th	Night	8% 5% 31% 42% 13% 1	570
	11th to 20th	Night	11% 5% 41% 34% 8%	570
	21st to end	Night	4 4 31% 49% 11%	570
July	1st to 10th	Night	7% 4 25% 47% 17% 1	555
	11th to 20th	Night	5% 2 26% 54% 13% 1	552
	21st to end	Night	5% 3 24% 52% 17%	624
August	1st to 10th	Night	8% 2 21% 50% 19%	567
	11th to 20th	Night	7% 3 23% 54% 14%	564
	21st to end	Night	5% 3 29% 49% 14%	627
September	1st to 10th	Night	9% 3 31% 42% 14% 1	570
	11th to 20th	Night	8% 4 31% 41% 15% 1	570
	21st to end	Night	11% 5% 32% 38% 14% 1	570
October	1st to 10th	Night	14% 7% 27% 39% 12% 1	570
	11th to 20th	Night	10% 9% 32% 38% 10% 1	751
	21st to end	Night	12% 10% 33% 35% 9% 1	1015
November	1st to 10th	Night	7% 6% 39% 38% 9% 1	925
	11th to 20th	Night	7% 8% 42% 34% 9%	950
	21st to end	Night	9% 7% 37% 37% 9% 1	950
December	1st to 10th	Night	8% 12% 43% 30% 6% 1	950
	11th to 20th	Night	9% 9% 42% 32% 8%	950
	21st to end	Night	12% 12% 38% 32% 6%	1045

Page generated at 2024-10-22 19:21:01. Version ac07

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