Rural Logan County Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rural Logan County Observatory clear sky chart from 2005-11-06 to 2026-02-01.

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	10% 8% 3 8% 5% 4 5% 4 6% 7% 40%	136162
	Night	8% 8% 3 8% 6% 5% 5% 4 6% 7% 41%	133205
Transparency	Day	42% 5% 14% 26% 12% 1	130786
	Night	42% 5% 14% 25% 13% 1	129601
Seeing	Day	14% 11% 33% 29% 12% 2	17747
	Night	12% 10% 36% 32% 9% 1	27800

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	4 10% 5% 18% 14% 8% 9% 5% 6% 5% 16%	3548
	11th to 20th	Day	3 7% 3 11% 8% 6% 11% 12% 13% 9% 18%	3720
	21st to end	Day	3 9% 5% 16% 10% 8% 5% 3 6% 6% 30%	4092
February	1st to 10th	Day	8% 15% 4 9% 5% 6% 8% 5% 7% 7% 26%	1718
	11th to 20th	Day	6% 12% 3 12% 8% 5% 9% 5% 6% 8% 26%	1848
	21st to end	Day	6% 12% 6% 14% 6% 5% 6% 4 7% 6% 28%	1650
March	1st to 10th	Day	8% 10% 4 13% 6% 4 4 3 4 6% 38%	4500
	11th to 20th	Day	6% 10% 4 10% 6% 5% 6% 4 7% 9% 33%	4936
	21st to end	Day	16% 14% 6% 12% 8% 5% 4 3 5% 6% 22%	5503
April	1st to 10th	Day	11% 10% 3 8% 6% 4 4 4 6% 6% 38%	2400
	11th to 20th	Day	17% 11% 4 7% 4 4 5% 3 5% 5% 34%	2548
	21st to end	Day	17% 13% 3 6% 4 4 4 4 6% 6% 34%	2600
May	1st to 10th	Day	12% 7% 2 5% 3 3 4 3 5% 7% 49%	5900
	11th to 20th	Day	20% 9% 2 5% 4 3 4 3 4 6% 39%	6078
	21st to end	Day	14% 8% 2 6% 4 4 4 4 6% 7% 42%	7373
June	1st to 10th	Day	13% 6% 2 5% 5% 4 4 4 6% 8% 42%	3000
	11th to 20th	Day	13% 6% 2 5% 4 5% 5% 4 6% 8% 41%	3000
	21st to end	Day	10% 4 2 5% 5% 4 4 4 7% 7% 47%	3000
July	1st to 10th	Day	7% 4 2 6% 4 4 5% 5% 7% 9% 47%	6799
	11th to 20th	Day	9% 4 2 4 3 3 4 3 5% 8% 53%	6348
	21st to end	Day	8% 5% 2 6% 4 4 5% 4 7% 9% 45%	6903
August	1st to 10th	Day	13% 6% 2 6% 4 4 4 4 6% 8% 45%	5985
	11th to 20th	Day	13% 6% 2 5% 4 4 5% 4 6% 9% 43%	5821
	21st to end	Day	7% 4 2 5% 4 4 4 3 5% 6% 57%	6456
September	1st to 10th	Day	10% 4 1 4 3 4 4 3 4 7% 54%	2360
	11th to 20th	Day	11% 6% 2 5% 4 3 4 3 5% 7% 51%	2200
	21st to end	Day	11% 6% 2 4 3 3 3 3 5% 7% 53%	2200
October	1st to 10th	Day	9% 6% 1 4 3 3 3 2 5% 6% 58%	3501
	11th to 20th	Day	11% 7% 2 4 3 3 3 3 4 7% 53%	3093
	21st to end	Day	11% 9% 2 6% 5% 4 5% 4 6% 8% 40%	3190
November	1st to 10th	Day	11% 11% 4 9% 5% 5% 4 3 5% 6% 37%	1853
	11th to 20th	Day	6% 11% 4 11% 7% 5% 5% 4 4 7% 35%	1779
	21st to end	Day	6% 12% 5% 11% 7% 6% 4 3 6% 7% 34%	1612
December	1st to 10th	Day	6% 10% 6% 15% 7% 8% 7% 5% 6% 6% 24%	2360
	11th to 20th	Day	5% 11% 5% 17% 7% 7% 7% 4 6% 7% 24%	2713
	21st to end	Day	10% 13% 4 10% 9% 5% 5% 4 6% 6% 28%	3575
January	1st to 10th	Night	5% 11% 4 14% 12% 7% 8% 5% 8% 6% 20%	6632
	11th to 20th	Night	3 7% 3 9% 7% 8% 11% 8% 11% 8% 24%	6480
	21st to end	Night	3 9% 4 14% 8% 6% 5% 4 5% 6% 36%	7128
February	1st to 10th	Night	7% 12% 5% 10% 7% 6% 6% 6% 6% 7% 27%	2681
	11th to 20th	Night	5% 9% 4 8% 7% 6% 5% 4 6% 7% 38%	2454
	21st to end	Night	7% 10% 4 9% 7% 6% 5% 4 6% 7% 36%	1980
March	1st to 10th	Night	7% 8% 3 9% 6% 4 5% 4 5% 6% 43%	5374
	11th to 20th	Night	9% 9% 3 9% 6% 5% 5% 4 5% 7% 37%	5026
	21st to end	Night	14% 12% 4 10% 6% 5% 5% 3 5% 7% 29%	5428
April	1st to 10th	Night	9% 8% 3 8% 5% 5% 4 4 6% 7% 42%	2000
	11th to 20th	Night	15% 10% 3 7% 4 4 4 3 5% 6% 39%	1799
	21st to end	Night	14% 11% 3 7% 4 5% 4 4 4 7% 38%	1800
May	1st to 10th	Night	9% 6% 2 4 3 3 4 4 5% 7% 53%	4080
	11th to 20th	Night	16% 9% 3 5% 4 3 3 3 5% 6% 43%	3821
	21st to end	Night	13% 7% 2 6% 4 4 4 3 5% 8% 45%	3521
June	1st to 10th	Night	9% 5% 2 3 4 4 4 3 7% 9% 51%	1400
	11th to 20th	Night	9% 5% 2 6% 5% 4 4 4 6% 8% 48%	1400
	21st to end	Night	6% 4 1 4 3 3 5% 3 6% 8% 57%	1400
July	1st to 10th	Night	5% 3 2 5% 4 5% 4 5% 7% 8% 52%	3180
	11th to 20th	Night	5% 3 2 4 2 3 3 3 5% 8% 60%	3629
	21st to end	Night	9% 5% 2 6% 4 4 5% 4 7% 10% 45%	3970
August	1st to 10th	Night	7% 5% 2 6% 4 4 4 4 6% 8% 51%	3825
	11th to 20th	Night	10% 6% 2 6% 3 4 4 3 4 6% 52%	4028
	21st to end	Night	6% 4 2 4 3 3 3 3 6% 6% 59%	4505
September	1st to 10th	Night	7% 4 1 4 2 3 4 3 5% 6% 60%	2040
	11th to 20th	Night	9% 4 1 4 3 4 4 3 5% 8% 55%	2200
	21st to end	Night	12% 6% 1 4 3 3 3 3 4 6% 56%	2200
October	1st to 10th	Night	9% 4 1 4 2 3 3 3 4 5% 61%	3646
	11th to 20th	Night	11% 7% 3 5% 4 3 3 4 6% 7% 46%	4047
	21st to end	Night	12% 8% 3 6% 5% 4 3 3 5% 7% 45%	4610
November	1st to 10th	Night	9% 10% 3 7% 5% 5% 5% 4 6% 6% 41%	2665
	11th to 20th	Night	7% 9% 4 11% 7% 5% 5% 3 5% 6% 38%	2840
	21st to end	Night	8% 8% 4 10% 5% 5% 5% 4 6% 8% 38%	3007
December	1st to 10th	Night	4 10% 5% 12% 7% 6% 7% 4 7% 7% 31%	5050
	11th to 20th	Night	7% 11% 4 14% 8% 7% 7% 4 6% 7% 25%	5714
	21st to end	Night	11% 11% 4 13% 7% 5% 5% 4 5% 7% 29%	7645

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	68% 4 9% 12% 6% 1	3549
	11th to 20th	Day	51% 6% 14% 16% 10% 1	3720
	21st to end	Day	55% 5% 14% 19% 6%	4092
February	1st to 10th	Day	54% 7% 11% 17% 10% 1	1718
	11th to 20th	Day	52% 8% 12% 18% 9% 2	1857
	21st to end	Day	54% 5% 14% 19% 8% 1	1650
March	1st to 10th	Day	47% 5% 13% 26% 10%	4500
	11th to 20th	Day	44% 6% 16% 24% 10%	4936
	21st to end	Day	63% 5% 14% 13% 5% 1	5503
April	1st to 10th	Day	44% 7% 14% 22% 12% 1	2400
	11th to 20th	Day	51% 5% 10% 21% 11% 1	2551
	21st to end	Day	49% 6% 15% 22% 7% 1	2600
May	1st to 10th	Day	34% 5% 11% 31% 18% 1	5900
	11th to 20th	Day	45% 6% 10% 22% 15% 2	6082
	21st to end	Day	39% 7% 13% 29% 11%	7374
June	1st to 10th	Day	38% 8% 16% 27% 10% 1	3000
	11th to 20th	Day	39% 8% 16% 25% 11% 1	3000
	21st to end	Day	33% 7% 19% 28% 12% 1	3000
July	1st to 10th	Day	33% 5% 19% 31% 10% 2	6726
	11th to 20th	Day	30% 4 11% 38% 15% 1	6272
	21st to end	Day	36% 4 21% 28% 11% 1	6705
August	1st to 10th	Day	33% 5% 15% 29% 15% 2	4355
	11th to 20th	Day	39% 5% 17% 31% 8% 1	4210
	21st to end	Day	31% 5% 15% 34% 14% 2	4653
September	1st to 10th	Day	30% 5% 14% 36% 15% 1	2360
	11th to 20th	Day	34% 6% 16% 30% 13% 1	2200
	21st to end	Day	31% 6% 13% 32% 17% 2	2200
October	1st to 10th	Day	28% 3 9% 32% 23% 5%	3501
	11th to 20th	Day	33% 3 10% 37% 16% 1	3093
	21st to end	Day	42% 5% 14% 20% 18% 2	3190
November	1st to 10th	Day	47% 5% 12% 23% 12% 1	1853
	11th to 20th	Day	48% 6% 14% 22% 9% 1	1779
	21st to end	Day	49% 6% 15% 21% 8% 1	1612
December	1st to 10th	Day	59% 5% 15% 16% 4 1	2360
	11th to 20th	Day	59% 5% 14% 16% 5%	2710
	21st to end	Day	55% 3 12% 20% 9%	3575
January	1st to 10th	Night	60% 5% 10% 18% 6%	6632
	11th to 20th	Night	51% 5% 15% 16% 12% 1	6480
	21st to end	Night	49% 5% 15% 20% 11%	7128
February	1st to 10th	Night	53% 6% 12% 16% 11% 1	2681
	11th to 20th	Night	44% 6% 12% 22% 15% 2	2455
	21st to end	Night	46% 6% 14% 20% 12% 2	1980
March	1st to 10th	Night	40% 5% 13% 29% 13% 1	5374
	11th to 20th	Night	43% 7% 15% 23% 12% 1	5026
	21st to end	Night	53% 6% 13% 19% 8% 1	5428
April	1st to 10th	Night	40% 5% 13% 23% 16% 2	2000
	11th to 20th	Night	46% 5% 10% 23% 15% 2	1799
	21st to end	Night	47% 6% 12% 22% 12% 1	1800
May	1st to 10th	Night	29% 6% 13% 30% 20% 3	4080
	11th to 20th	Night	41% 6% 9% 23% 20% 1	3822
	21st to end	Night	35% 7% 14% 29% 14%	3521
June	1st to 10th	Night	29% 7% 19% 31% 11% 3	1400
	11th to 20th	Night	34% 8% 17% 25% 13% 3	1400
	21st to end	Night	24% 7% 21% 31% 15% 2	1400
July	1st to 10th	Night	29% 5% 20% 33% 11% 3	3145
	11th to 20th	Night	23% 3 15% 42% 15% 2	3582
	21st to end	Night	36% 4 21% 28% 10% 1	3856
August	1st to 10th	Night	27% 5% 16% 33% 16% 3	2779
	11th to 20th	Night	32% 4 16% 34% 12% 1	2915
	21st to end	Night	29% 4 15% 34% 16% 2	3252
September	1st to 10th	Night	25% 5% 14% 33% 21% 2	2040
	11th to 20th	Night	27% 6% 20% 29% 17% 1	2200
	21st to end	Night	30% 4 11% 32% 20% 3	2200
October	1st to 10th	Night	26% 4 8% 29% 30% 3	3646
	11th to 20th	Night	37% 3 11% 32% 16% 2	4047
	21st to end	Night	40% 4 11% 29% 15% 1	4610
November	1st to 10th	Night	42% 6% 11% 22% 17% 2	2665
	11th to 20th	Night	46% 5% 14% 21% 12% 2	2840
	21st to end	Night	43% 6% 16% 25% 8% 1	3007
December	1st to 10th	Night	51% 4 22% 16% 7%	5050
	11th to 20th	Night	57% 5% 15% 17% 5%	5716
	21st to end	Night	55% 4 11% 20% 9%	7645

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	10% 12% 39% 28% 8% 3	330
	11th to 20th	Day	8% 18% 41% 24% 7% 2	330
	21st to end	Day	10% 18% 35% 26% 9% 2	363
February	1st to 10th	Day	14% 15% 42% 24% 5%	300
	11th to 20th	Day	13% 11% 45% 24% 5% 2	300
	21st to end	Day	12% 11% 41% 32% 4	249
March	1st to 10th	Day	16% 11% 40% 21% 11% 2	300
	11th to 20th	Day	13% 14% 37% 26% 8% 2	300
	21st to end	Day	14% 10% 36% 24% 13% 3	344
April	1st to 10th	Day	16% 15% 38% 24% 7% 1	500
	11th to 20th	Day	25% 15% 29% 22% 8% 1	669
	21st to end	Day	23% 12% 28% 27% 9% 2	700
May	1st to 10th	Day	16% 12% 31% 28% 12% 1	703
	11th to 20th	Day	21% 9% 30% 27% 11% 2	725
	21st to end	Day	15% 12% 27% 26% 16% 3	789
June	1st to 10th	Day	12% 9% 28% 32% 14% 5%	730
	11th to 20th	Day	13% 12% 41% 24% 9% 1	730
	21st to end	Day	13% 10% 29% 33% 12% 3	730
July	1st to 10th	Day	7% 5% 28% 37% 19% 4	721
	11th to 20th	Day	7% 7% 34% 35% 14% 2	718
	21st to end	Day	6% 4 28% 41% 16% 4	794
August	1st to 10th	Day	11% 4 23% 39% 19% 3	726
	11th to 20th	Day	13% 5% 25% 31% 20% 6%	715
	21st to end	Day	9% 7% 27% 34% 20% 3	795
September	1st to 10th	Day	11% 9% 31% 34% 13% 2	490
	11th to 20th	Day	17% 8% 30% 34% 10% 1	330
	21st to end	Day	17% 12% 32% 26% 11% 3	330
October	1st to 10th	Day	19% 11% 29% 25% 12% 3	330
	11th to 20th	Day	19% 15% 34% 26% 6%	330
	21st to end	Day	18% 19% 39% 17% 5% 1	363
November	1st to 10th	Day	19% 11% 39% 24% 6% 1	330
	11th to 20th	Day	10% 18% 39% 22% 9% 1	330
	21st to end	Day	13% 15% 46% 18% 8% 1	330
December	1st to 10th	Day	13% 13% 41% 25% 7% 1	330
	11th to 20th	Day	15% 17% 42% 23% 3	330
	21st to end	Day	15% 13% 43% 21% 6% 2	363
January	1st to 10th	Night	10% 13% 44% 25% 7% 1	1050
	11th to 20th	Night	11% 15% 41% 26% 6% 1	1050
	21st to end	Night	10% 12% 44% 27% 6%	1155
February	1st to 10th	Night	14% 12% 38% 30% 5% 1	1001
	11th to 20th	Night	10% 11% 42% 26% 9% 1	900
	21st to end	Night	10% 10% 38% 28% 10% 3	660
March	1st to 10th	Night	15% 11% 36% 28% 9% 1	800
	11th to 20th	Night	15% 13% 36% 26% 10%	620
	21st to end	Night	14% 7% 38% 29% 11% 1	660
April	1st to 10th	Night	13% 11% 37% 32% 7%	600
	11th to 20th	Night	18% 11% 31% 32% 8%	593
	21st to end	Night	18% 11% 29% 30% 12%	600
May	1st to 10th	Night	13% 7% 33% 37% 11%	600
	11th to 20th	Night	13% 7% 33% 34% 12%	591
	21st to end	Night	14% 8% 32% 35% 11%	650
June	1st to 10th	Night	12% 7% 27% 39% 15% 1	600
	11th to 20th	Night	11% 7% 40% 33% 9%	600
	21st to end	Night	7% 6% 30% 46% 11% 1	600
July	1st to 10th	Night	7% 3 26% 46% 17%	585
	11th to 20th	Night	4 2 32% 48% 13% 1	582
	21st to end	Night	5% 2 26% 50% 15% 1	657
August	1st to 10th	Night	6% 3 25% 50% 15% 1	597
	11th to 20th	Night	9% 3 27% 41% 18% 2	594
	21st to end	Night	8% 5% 27% 44% 15% 1	660
September	1st to 10th	Night	9% 4 29% 40% 16% 2	600
	11th to 20th	Night	10% 5% 33% 38% 14% 1	600
	21st to end	Night	12% 9% 33% 33% 13% 1	600
October	1st to 10th	Night	16% 11% 30% 35% 8%	630
	11th to 20th	Night	20% 12% 33% 27% 8%	885
	21st to end	Night	17% 12% 38% 25% 7% 1	1100
November	1st to 10th	Night	14% 13% 39% 27% 7%	1025
	11th to 20th	Night	11% 14% 42% 25% 7% 1	1050
	21st to end	Night	12% 14% 41% 28% 5%	1050
December	1st to 10th	Night	11% 11% 43% 27% 7%	1050
	11th to 20th	Night	15% 14% 38% 27% 5% 1	1050
	21st to end	Night	17% 12% 40% 25% 5% 1	1155

Page generated at 2026-01-29 00:21:41. Version ac07

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