West Columbia
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the West Columbia clear sky chart from 2005-11-06 to 2024-03-23.

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	13% 5% 2 5% 5% 3 5% 5% 6% 8% 44%	79126
	Night	13% 5% 2 5% 5% 3 4 5% 5% 7% 45%	80768
Transparency	Day	37% 8% 12% 19% 18% 5%	78849
	Night	37% 8% 11% 18% 19% 7%	80564
Seeing	Day	15% 8% 22% 24% 20% 11%	14427
	Night	15% 6% 23% 33% 21% 3	24605

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	16% 5% 2 4 3 2 3 3 6% 8% 48%	2836
	11th to 20th	Day	13% 5% 1 4 4 2 3 3 4 5% 54%	2840
	21st to end	Day	18% 8% 3 6% 5% 3 3 3 3 4 45%	3124
February	1st to 10th	Day	15% 6% 2 5% 5% 3 5% 4 5% 7% 42%	1727
	11th to 20th	Day	19% 6% 2 5% 5% 2 3 4 4 6% 45%	1848
	21st to end	Day	19% 5% 3 5% 5% 3 4 3 4 6% 43%	1628
March	1st to 10th	Day	14% 6% 2 4 3 2 4 3 4 6% 51%	2090
	11th to 20th	Day	15% 6% 3 5% 5% 3 4 4 6% 7% 43%	2090
	21st to end	Day	15% 6% 2 6% 4 3 4 5% 6% 7% 42%	2200
April	1st to 10th	Day	10% 4 2 4 4 3 5% 4 6% 6% 53%	1980
	11th to 20th	Day	11% 4 3 5% 4 2 4 5% 6% 8% 48%	2106
	21st to end	Day	8% 5% 2 3 4 3 4 4 6% 8% 53%	2268
May	1st to 10th	Day	7% 4 2 4 5% 3 5% 4 6% 8% 51%	2340
	11th to 20th	Day	12% 5% 2 5% 5% 4 5% 5% 6% 8% 43%	2301
	21st to end	Day	11% 5% 2 5% 6% 4 5% 5% 6% 9% 40%	2531
June	1st to 10th	Day	10% 6% 3 6% 6% 3 6% 6% 7% 10% 38%	2340
	11th to 20th	Day	8% 4 2 4 4 4 6% 6% 7% 10% 44%	2340
	21st to end	Day	5% 4 2 5% 6% 4 6% 8% 8% 11% 40%	2340
July	1st to 10th	Day	8% 4 3 6% 7% 5% 7% 8% 8% 11% 34%	2340
	11th to 20th	Day	8% 5% 2 7% 7% 5% 7% 8% 8% 11% 34%	2340
	21st to end	Day	7% 4 2 6% 7% 4 6% 8% 10% 12% 33%	2547
August	1st to 10th	Day	10% 5% 3 7% 6% 4 6% 8% 9% 10% 32%	2327
	11th to 20th	Day	13% 6% 2 6% 6% 4 7% 7% 7% 9% 31%	2303
	21st to end	Day	12% 6% 3 7% 7% 4 6% 7% 8% 11% 30%	2388
September	1st to 10th	Day	8% 4 2 5% 7% 4 6% 6% 7% 8% 42%	1980
	11th to 20th	Day	13% 5% 3 5% 6% 3 5% 4 5% 8% 42%	1980
	21st to end	Day	17% 6% 2 4 4 3 4 4 5% 7% 43%	1980
October	1st to 10th	Day	15% 5% 2 4 5% 3 3 4 4 6% 50%	1882
	11th to 20th	Day	11% 4 2 4 5% 3 3 3 4 5% 57%	1800
	21st to end	Day	11% 4 2 4 4 2 4 3 3 4 58%	1980
November	1st to 10th	Day	12% 6% 1 3 4 3 4 3 4 5% 55%	1857
	11th to 20th	Day	15% 4 2 4 4 2 3 3 5% 5% 53%	1796
	21st to end	Day	14% 5% 3 5% 4 3 4 4 4 6% 49%	1710
December	1st to 10th	Day	19% 6% 2 5% 5% 3 5% 4 5% 7% 39%	1710
	11th to 20th	Day	16% 4 2 4 4 2 3 4 4 6% 52%	2153
	21st to end	Day	19% 7% 3 5% 3 2 3 3 5% 6% 44%	3124
January	1st to 10th	Night	16% 6% 2 5% 4 3 3 4 4 6% 47%	4109
	11th to 20th	Night	11% 6% 2 5% 6% 3 5% 5% 5% 7% 45%	4120
	21st to end	Night	18% 7% 2 5% 4 2 3 4 4 5% 45%	4532
February	1st to 10th	Night	16% 6% 2 4 5% 3 4 4 5% 6% 45%	2451
	11th to 20th	Night	19% 5% 3 5% 4 2 4 4 4 4 46%	2218
	21st to end	Night	16% 5% 2 5% 5% 3 4 4 5% 6% 45%	1824
March	1st to 10th	Night	14% 5% 3 4 5% 2 4 4 4 6% 49%	2090
	11th to 20th	Night	14% 4 2 4 5% 3 5% 4 6% 7% 45%	2090
	21st to end	Night	13% 5% 3 5% 5% 3 4 4 5% 8% 45%	2201
April	1st to 10th	Night	10% 5% 2 4 3 3 5% 4 5% 7% 53%	1980
	11th to 20th	Night	12% 4 2 5% 4 3 3 4 5% 5% 53%	1802
	21st to end	Night	9% 4 2 3 4 2 4 4 5% 8% 54%	1706
May	1st to 10th	Night	8% 4 3 4 5% 3 5% 4 7% 8% 50%	1620
	11th to 20th	Night	10% 5% 2 6% 6% 4 7% 5% 6% 10% 40%	1592
	21st to end	Night	10% 4 2 5% 7% 4 5% 6% 6% 10% 43%	1744
June	1st to 10th	Night	13% 5% 2 6% 6% 4 6% 5% 8% 11% 34%	1620
	11th to 20th	Night	8% 5% 2 5% 6% 4 6% 6% 8% 11% 39%	1620
	21st to end	Night	7% 4 3 5% 7% 4 7% 8% 10% 13% 33%	1620
July	1st to 10th	Night	8% 5% 3 6% 6% 5% 6% 7% 8% 11% 35%	1620
	11th to 20th	Night	8% 5% 2 6% 6% 4 6% 7% 8% 13% 35%	1620
	21st to end	Night	6% 4 3 7% 7% 4 7% 6% 9% 11% 36%	1771
August	1st to 10th	Night	9% 5% 3 5% 7% 4 8% 8% 9% 9% 32%	1611
	11th to 20th	Night	12% 7% 3 5% 6% 5% 6% 7% 7% 10% 33%	1598
	21st to end	Night	11% 6% 2 7% 7% 4 5% 6% 8% 11% 34%	1943
September	1st to 10th	Night	9% 4 2 6% 5% 4 5% 5% 8% 9% 41%	1980
	11th to 20th	Night	12% 6% 2 7% 7% 3 5% 4 5% 6% 43%	1980
	21st to end	Night	16% 6% 3 5% 4 3 5% 5% 5% 7% 42%	1980
October	1st to 10th	Night	14% 5% 2 6% 3 2 3 3 3 6% 53%	2076
	11th to 20th	Night	13% 4 3 3 4 2 3 3 4 6% 54%	2160
	21st to end	Night	11% 5% 2 4 4 2 3 4 5% 5% 56%	2376
November	1st to 10th	Night	13% 5% 2 3 3 2 3 3 4 5% 57%	2221
	11th to 20th	Night	14% 6% 2 4 3 3 3 4 3 5% 53%	2379
	21st to end	Night	14% 4 3 4 4 3 4 4 5% 6% 49%	2470
December	1st to 10th	Night	18% 5% 3 4 5% 3 4 4 5% 6% 43%	2470
	11th to 20th	Night	17% 5% 2 4 4 2 3 3 3 5% 52%	3042
	21st to end	Night	20% 7% 2 5% 4 3 4 5% 4 7% 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	33% 6% 9% 23% 22% 7%	2837
	11th to 20th	Day	33% 5% 6% 17% 30% 10%	2840
	21st to end	Day	44% 4 4 16% 24% 8%	3124
February	1st to 10th	Day	41% 5% 10% 19% 19% 6%	1727
	11th to 20th	Day	42% 5% 5% 18% 24% 6%	1858
	21st to end	Day	43% 5% 8% 15% 20% 8%	1628
March	1st to 10th	Day	36% 5% 8% 21% 20% 11%	2090
	11th to 20th	Day	39% 8% 10% 18% 18% 7%	2090
	21st to end	Day	41% 7% 10% 18% 19% 5%	2200
April	1st to 10th	Day	31% 6% 11% 19% 25% 7%	1980
	11th to 20th	Day	33% 7% 11% 19% 20% 10%	2106
	21st to end	Day	29% 7% 11% 26% 23% 4	2268
May	1st to 10th	Day	31% 8% 14% 22% 22% 4	2340
	11th to 20th	Day	39% 9% 15% 19% 17% 2	2305
	21st to end	Day	39% 10% 13% 23% 15% 1	2531
June	1st to 10th	Day	38% 11% 16% 22% 11% 1	2340
	11th to 20th	Day	32% 10% 19% 25% 12% 1	2340
	21st to end	Day	34% 12% 19% 21% 12% 2	2340
July	1st to 10th	Day	39% 14% 19% 16% 9% 3	2275
	11th to 20th	Day	39% 15% 22% 16% 6% 1	2271
	21st to end	Day	37% 13% 22% 20% 7% 1	2405
August	1st to 10th	Day	41% 14% 18% 18% 7% 1	2314
	11th to 20th	Day	45% 14% 17% 16% 8% 1	2303
	21st to end	Day	44% 14% 17% 16% 8% 2	2388
September	1st to 10th	Day	35% 11% 14% 17% 18% 4	1980
	11th to 20th	Day	40% 8% 11% 17% 21% 3	1980
	21st to end	Day	41% 7% 9% 20% 17% 7%	1980
October	1st to 10th	Day	36% 5% 7% 21% 23% 7%	1882
	11th to 20th	Day	29% 5% 9% 24% 26% 8%	1800
	21st to end	Day	30% 5% 6% 17% 30% 12%	1980
November	1st to 10th	Day	32% 4 7% 18% 27% 13%	1857
	11th to 20th	Day	34% 4 8% 20% 24% 11%	1796
	21st to end	Day	37% 5% 8% 19% 22% 9%	1710
December	1st to 10th	Day	44% 7% 9% 18% 16% 6%	1710
	11th to 20th	Day	34% 5% 7% 20% 24% 10%	2150
	21st to end	Day	41% 6% 8% 20% 23% 3	3124
January	1st to 10th	Night	37% 5% 8% 18% 24% 8%	4109
	11th to 20th	Night	36% 7% 8% 19% 23% 7%	4120
	21st to end	Night	42% 6% 5% 14% 26% 8%	4532
February	1st to 10th	Night	40% 5% 8% 19% 20% 9%	2451
	11th to 20th	Night	42% 5% 7% 17% 21% 8%	2219
	21st to end	Night	39% 6% 9% 17% 18% 11%	1824
March	1st to 10th	Night	37% 6% 8% 16% 22% 11%	2090
	11th to 20th	Night	38% 8% 11% 15% 21% 8%	2090
	21st to end	Night	37% 6% 11% 21% 18% 6%	2201
April	1st to 10th	Night	31% 6% 13% 18% 23% 9%	1980
	11th to 20th	Night	32% 6% 10% 20% 21% 11%	1802
	21st to end	Night	29% 6% 11% 25% 23% 5%	1706
May	1st to 10th	Night	30% 9% 14% 24% 20% 5%	1620
	11th to 20th	Night	39% 11% 16% 18% 16% 1	1593
	21st to end	Night	34% 11% 13% 25% 15% 2	1745
June	1st to 10th	Night	40% 12% 18% 19% 11% 1	1620
	11th to 20th	Night	36% 11% 18% 23% 9% 3	1620
	21st to end	Night	36% 15% 19% 18% 10% 2	1620
July	1st to 10th	Night	38% 13% 21% 14% 9% 4	1575
	11th to 20th	Night	37% 15% 24% 16% 7% 2	1566
	21st to end	Night	38% 14% 23% 17% 8% 1	1672
August	1st to 10th	Night	40% 17% 21% 16% 5% 1	1600
	11th to 20th	Night	44% 12% 20% 16% 8% 1	1598
	21st to end	Night	41% 13% 19% 16% 9% 1	1943
September	1st to 10th	Night	36% 10% 17% 18% 14% 5%	1980
	11th to 20th	Night	41% 9% 10% 17% 19% 4	1980
	21st to end	Night	41% 8% 12% 17% 17% 5%	1980
October	1st to 10th	Night	34% 6% 10% 17% 28% 6%	2076
	11th to 20th	Night	30% 5% 10% 22% 23% 11%	2160
	21st to end	Night	29% 6% 7% 19% 27% 13%	2376
November	1st to 10th	Night	31% 5% 8% 15% 27% 15%	2221
	11th to 20th	Night	34% 5% 7% 16% 25% 13%	2379
	21st to end	Night	35% 5% 9% 18% 24% 10%	2470
December	1st to 10th	Night	42% 7% 9% 17% 19% 7%	2470
	11th to 20th	Night	36% 3 7% 18% 25% 10%	3044
	21st to end	Night	43% 5% 8% 20% 19% 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	17% 16% 45% 17% 4	270
	11th to 20th	Day	20% 17% 36% 19% 7%	270
	21st to end	Day	22% 21% 38% 16% 3	297
February	1st to 10th	Day	19% 19% 37% 20% 6%	270
	11th to 20th	Day	29% 16% 37% 16% 2	270
	21st to end	Day	23% 15% 39% 18% 5%	283
March	1st to 10th	Day	19% 15% 28% 27% 11%	460
	11th to 20th	Day	17% 13% 42% 21% 6% 1	460
	21st to end	Day	19% 13% 33% 24% 10% 1	470
April	1st to 10th	Day	15% 16% 29% 26% 13% 1	420
	11th to 20th	Day	11% 15% 29% 23% 18% 5%	412
	21st to end	Day	12% 9% 27% 27% 18% 7%	420
May	1st to 10th	Day	7% 11% 32% 24% 20% 5%	423
	11th to 20th	Day	15% 5% 18% 26% 23% 13%	447
	21st to end	Day	13% 4 12% 26% 26% 20%	485
June	1st to 10th	Day	9% 3 14% 28% 31% 15%	450
	11th to 20th	Day	11% 3 14% 25% 28% 20%	450
	21st to end	Day	8% 2 12% 30% 29% 19%	450
July	1st to 10th	Day	9% 2 7% 21% 31% 31%	445
	11th to 20th	Day	10% 2 6% 22% 35% 24%	444
	21st to end	Day	6% 1 9% 28% 35% 21%	488
August	1st to 10th	Day	13% 3 11% 24% 30% 19%	446
	11th to 20th	Day	14% 3 9% 20% 32% 22%	439
	21st to end	Day	13% 3 10% 20% 33% 22%	495
September	1st to 10th	Day	9% 3 8% 26% 34% 20%	450
	11th to 20th	Day	16% 2 12% 24% 30% 15%	450
	21st to end	Day	19% 2 14% 25% 27% 13%	450
October	1st to 10th	Day	17% 3 18% 32% 21% 10%	450
	11th to 20th	Day	11% 5% 21% 30% 23% 11%	450
	21st to end	Day	13% 6% 25% 28% 21% 6%	495
November	1st to 10th	Day	15% 6% 27% 27% 19% 6%	455
	11th to 20th	Day	19% 9% 32% 28% 10% 2	356
	21st to end	Day	13% 12% 31% 28% 14% 1	270
December	1st to 10th	Day	24% 14% 34% 21% 6% 1	270
	11th to 20th	Day	21% 10% 39% 20% 10% 1	270
	21st to end	Day	24% 15% 32% 19% 7% 3	297
January	1st to 10th	Night	21% 11% 31% 29% 8%	760
	11th to 20th	Night	18% 11% 34% 31% 7%	760
	21st to end	Night	18% 10% 36% 32% 3	836
February	1st to 10th	Night	19% 11% 30% 35% 5%	760
	11th to 20th	Night	22% 11% 34% 30% 2	743
	21st to end	Night	18% 14% 34% 29% 5%	628
March	1st to 10th	Night	17% 10% 32% 35% 6%	760
	11th to 20th	Night	16% 9% 37% 29% 8%	760
	21st to end	Night	15% 10% 35% 31% 9%	801
April	1st to 10th	Night	13% 13% 31% 31% 11%	720
	11th to 20th	Night	13% 10% 29% 32% 16%	711
	21st to end	Night	12% 6% 27% 39% 15%	626
May	1st to 10th	Night	9% 7% 29% 37% 17%	540
	11th to 20th	Night	11% 3 24% 38% 21% 3	531
	21st to end	Night	10% 2 12% 38% 34% 4	584
June	1st to 10th	Night	14% 2 12% 40% 28% 5%	540
	11th to 20th	Night	10% 1 13% 33% 31% 11%	540
	21st to end	Night	8% 2 11% 38% 35% 6%	540
July	1st to 10th	Night	10% 2 8% 33% 40% 8%	525
	11th to 20th	Night	10% 1 6% 29% 47% 7%	522
	21st to end	Night	6% 2 9% 34% 44% 6%	591
August	1st to 10th	Night	10% 1 8% 27% 46% 8%	537
	11th to 20th	Night	14% 2 5% 30% 42% 7%	534
	21st to end	Night	12% 1 10% 27% 42% 7%	748
September	1st to 10th	Night	9% 2 9% 29% 44% 6%	720
	11th to 20th	Night	14% 1 12% 29% 39% 4	720
	21st to end	Night	19% 2 12% 31% 32% 3	720
October	1st to 10th	Night	15% 3 18% 31% 28% 5%	720
	11th to 20th	Night	15% 5% 20% 33% 25% 3	720
	21st to end	Night	12% 5% 24% 32% 24% 2	792
November	1st to 10th	Night	15% 6% 22% 35% 19% 3	740
	11th to 20th	Night	16% 9% 27% 33% 14% 1	760
	21st to end	Night	14% 7% 25% 35% 17% 1	760
December	1st to 10th	Night	18% 8% 28% 34% 10% 1	760
	11th to 20th	Night	19% 7% 26% 35% 12% 1	760
	21st to end	Night	24% 11% 25% 30% 10%	836

Page generated at 2024-03-19 23:31:09. Version ac07

Copyright © 2024 Attilla Danko.