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 2024-11-28.

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 7% 5% 4 5% 4 6% 7% 40%	105437
	Night	9% 8% 3 8% 5% 5% 5% 4 6% 7% 41%	102753
Transparency	Day	41% 6% 14% 26% 11% 1	105173
	Night	40% 6% 14% 25% 13% 1	102607
Seeing	Day	13% 11% 33% 29% 12% 2	16154
	Night	12% 10% 36% 32% 9% 1	26103

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% 12% 5% 16% 12% 7% 6% 4 5% 6% 23%	2414
	11th to 20th	Day	3 7% 4 11% 9% 6% 8% 13% 10% 9% 18%	2540
	21st to end	Day	5% 12% 5% 15% 9% 7% 5% 4 6% 6% 26%	2794
February	1st to 10th	Day	7% 15% 4 9% 6% 6% 8% 5% 7% 7% 26%	1632
	11th to 20th	Day	6% 12% 3 12% 8% 5% 9% 5% 6% 8% 24%	1753
	21st to end	Day	6% 12% 6% 14% 6% 5% 6% 4 7% 6% 28%	1570
March	1st to 10th	Day	9% 12% 5% 13% 6% 5% 4 3 4 6% 33%	3130
	11th to 20th	Day	6% 11% 4 9% 6% 6% 6% 5% 7% 9% 32%	3449
	21st to end	Day	18% 15% 5% 12% 8% 5% 4 3 5% 6% 20%	3839
April	1st to 10th	Day	10% 10% 3 8% 6% 4 5% 3 6% 6% 38%	2280
	11th to 20th	Day	17% 12% 4 7% 4 4 4 4 5% 5% 34%	2419
	21st to end	Day	16% 13% 3 6% 4 4 4 4 6% 6% 33%	2470
May	1st to 10th	Day	17% 9% 3 6% 4 4 4 4 5% 7% 38%	4120
	11th to 20th	Day	13% 7% 2 6% 4 4 5% 4 6% 7% 43%	4233
	21st to end	Day	14% 9% 2 6% 5% 4 4 4 6% 7% 39%	5133
June	1st to 10th	Day	12% 6% 2 5% 5% 4 4 4 6% 8% 42%	2850
	11th to 20th	Day	12% 6% 2 6% 4 5% 5% 4 6% 8% 42%	2850
	21st to end	Day	9% 4 2 5% 5% 4 4 4 7% 7% 48%	2850
July	1st to 10th	Day	8% 5% 2 6% 4 4 5% 5% 8% 9% 44%	4750
	11th to 20th	Day	4 3 1 3 3 3 4 4 6% 8% 59%	4438
	21st to end	Day	5% 4 2 5% 4 4 5% 4 7% 9% 51%	4802
August	1st to 10th	Day	11% 5% 2 5% 3 4 4 4 6% 9% 49%	4236
	11th to 20th	Day	15% 6% 2 5% 4 4 5% 3 6% 9% 42%	4041
	21st to end	Day	9% 5% 2 5% 4 3 4 3 5% 6% 54%	4512
September	1st to 10th	Day	10% 5% 1 4 3 4 4 3 4 7% 54%	2242
	11th to 20th	Day	10% 5% 2 6% 4 3 4 3 5% 6% 53%	2090
	21st to end	Day	12% 6% 2 4 3 3 3 4 5% 7% 51%	2090
October	1st to 10th	Day	10% 6% 1 4 3 3 3 2 5% 6% 57%	3394
	11th to 20th	Day	11% 7% 2 4 3 3 3 3 4 7% 53%	2998
	21st to end	Day	11% 9% 2 6% 5% 4 5% 5% 6% 8% 39%	3091
November	1st to 10th	Day	12% 11% 3 9% 5% 5% 4 3 5% 6% 37%	1763
	11th to 20th	Day	6% 11% 4 11% 8% 5% 5% 4 4 7% 35%	1695
	21st to end	Day	6% 12% 5% 11% 7% 6% 4 3 6% 7% 34%	1514
December	1st to 10th	Day	6% 11% 4 13% 7% 7% 6% 6% 6% 6% 27%	1330
	11th to 20th	Day	7% 12% 5% 10% 6% 6% 6% 2 6% 9% 30%	1683
	21st to end	Day	13% 14% 4 11% 7% 4 4 3 6% 6% 27%	2442
January	1st to 10th	Night	6% 12% 4 11% 9% 6% 6% 4 8% 7% 26%	4537
	11th to 20th	Night	3 8% 3 10% 7% 8% 11% 8% 9% 8% 23%	4430
	21st to end	Night	4 11% 4 14% 10% 7% 5% 4 5% 5% 31%	4873
February	1st to 10th	Night	7% 12% 5% 10% 8% 6% 7% 6% 6% 7% 27%	2546
	11th to 20th	Night	6% 10% 4 9% 7% 6% 5% 4 6% 7% 37%	2328
	21st to end	Night	8% 10% 4 9% 7% 6% 5% 4 6% 6% 35%	1884
March	1st to 10th	Night	8% 9% 3 9% 6% 5% 6% 4 6% 6% 39%	3734
	11th to 20th	Night	8% 10% 3 9% 6% 5% 4 3 5% 7% 38%	3512
	21st to end	Night	16% 13% 4 10% 7% 5% 4 3 5% 6% 27%	3791
April	1st to 10th	Night	9% 8% 3 8% 5% 5% 5% 4 5% 7% 42%	1900
	11th to 20th	Night	15% 10% 3 7% 4 4 4 3 5% 6% 39%	1708
	21st to end	Night	14% 11% 3 7% 4 5% 4 4 4 7% 38%	1710
May	1st to 10th	Night	12% 7% 2 5% 4 4 4 4 6% 7% 47%	2850
	11th to 20th	Night	11% 6% 2 5% 5% 4 4 3 6% 8% 46%	2656
	21st to end	Night	12% 7% 2 6% 4 4 4 3 6% 9% 43%	2451
June	1st to 10th	Night	10% 5% 1 3 3 4 4 3 7% 9% 50%	1330
	11th to 20th	Night	9% 5% 2 5% 5% 4 4 4 6% 8% 49%	1330
	21st to end	Night	5% 3 1 3 3 3 6% 3 6% 8% 58%	1330
July	1st to 10th	Night	6% 3 2 5% 4 5% 5% 5% 7% 9% 49%	2220
	11th to 20th	Night	2 2 1 3 2 3 3 3 4 8% 68%	2529
	21st to end	Night	4 3 1 5% 4 4 5% 4 8% 10% 51%	2761
August	1st to 10th	Night	6% 4 2 5% 4 4 4 4 6% 8% 55%	2701
	11th to 20th	Night	9% 5% 2 5% 3 4 4 3 5% 7% 52%	2798
	21st to end	Night	9% 5% 2 5% 3 3 3 3 5% 6% 56%	3153
September	1st to 10th	Night	7% 4 1 4 2 3 4 3 5% 6% 61%	1938
	11th to 20th	Night	8% 3 1 4 3 4 3 3 5% 8% 56%	2090
	21st to end	Night	12% 6% 1 4 3 3 3 3 4 6% 55%	2090
October	1st to 10th	Night	9% 4 1 4 2 3 3 3 4 5% 61%	3534
	11th to 20th	Night	10% 7% 3 5% 4 3 3 4 6% 8% 47%	3923
	21st to end	Night	12% 7% 3 6% 5% 4 3 3 5% 7% 45%	4467
November	1st to 10th	Night	9% 10% 4 7% 5% 5% 5% 4 6% 6% 41%	2535
	11th to 20th	Night	7% 9% 4 11% 7% 5% 4 3 4 6% 39%	2705
	21st to end	Night	8% 8% 4 10% 5% 4 5% 4 6% 8% 39%	2820
December	1st to 10th	Night	7% 12% 4 10% 7% 5% 6% 5% 7% 6% 31%	2850
	11th to 20th	Night	8% 12% 4 11% 6% 6% 6% 4 6% 7% 30%	3514
	21st to end	Night	15% 12% 4 11% 6% 4 4 4 5% 6% 29%	5225

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	60% 6% 12% 15% 7% 1	2415
	11th to 20th	Day	51% 8% 15% 19% 7% 1	2540
	21st to end	Day	56% 7% 10% 19% 8%	2794
February	1st to 10th	Day	54% 7% 12% 17% 9% 1	1632
	11th to 20th	Day	54% 8% 12% 17% 7% 2	1762
	21st to end	Day	55% 5% 13% 18% 8% 1	1570
March	1st to 10th	Day	51% 6% 9% 25% 9%	3130
	11th to 20th	Day	44% 8% 16% 22% 9%	3449
	21st to end	Day	64% 6% 13% 10% 5% 1	3839
April	1st to 10th	Day	44% 7% 14% 22% 11% 1	2280
	11th to 20th	Day	51% 5% 10% 21% 11% 1	2422
	21st to end	Day	49% 6% 15% 22% 7% 1	2470
May	1st to 10th	Day	44% 7% 11% 25% 12% 1	4120
	11th to 20th	Day	37% 8% 14% 27% 12% 2	4237
	21st to end	Day	40% 9% 17% 28% 6%	5133
June	1st to 10th	Day	38% 8% 16% 27% 10% 1	2850
	11th to 20th	Day	38% 8% 16% 25% 12% 1	2850
	21st to end	Day	33% 7% 19% 29% 12% 1	2850
July	1st to 10th	Day	34% 7% 19% 31% 9% 1	4676
	11th to 20th	Day	22% 5% 13% 38% 20% 2	4362
	21st to end	Day	29% 5% 20% 31% 14% 1	4651
August	1st to 10th	Day	33% 5% 15% 29% 16% 2	4221
	11th to 20th	Day	39% 5% 17% 31% 8% 1	4080
	21st to end	Day	31% 5% 15% 34% 14% 2	4511
September	1st to 10th	Day	30% 5% 13% 36% 15% 2	2242
	11th to 20th	Day	32% 6% 16% 31% 14% 1	2090
	21st to end	Day	32% 6% 14% 31% 16% 2	2090
October	1st to 10th	Day	28% 3 9% 31% 22% 5%	3394
	11th to 20th	Day	32% 3 10% 37% 16% 1	2998
	21st to end	Day	42% 5% 14% 19% 18% 2	3091
November	1st to 10th	Day	47% 6% 12% 23% 12% 1	1763
	11th to 20th	Day	49% 6% 13% 21% 9% 1	1695
	21st to end	Day	49% 7% 15% 21% 8% 1	1514
December	1st to 10th	Day	53% 8% 14% 18% 7% 1	1330
	11th to 20th	Day	49% 7% 15% 20% 8%	1680
	21st to end	Day	56% 5% 11% 20% 8%	2442
January	1st to 10th	Night	53% 7% 11% 21% 8%	4537
	11th to 20th	Night	51% 7% 15% 18% 8% 1	4430
	21st to end	Night	53% 6% 10% 20% 11%	4873
February	1st to 10th	Night	53% 7% 13% 16% 11% 1	2546
	11th to 20th	Night	45% 6% 12% 22% 12% 2	2329
	21st to end	Night	48% 6% 14% 18% 12% 2	1884
March	1st to 10th	Night	42% 7% 11% 27% 11% 1	3734
	11th to 20th	Night	41% 9% 14% 25% 10% 1	3512
	21st to end	Night	56% 8% 13% 14% 9% 1	3791
April	1st to 10th	Night	40% 6% 12% 23% 17% 2	1900
	11th to 20th	Night	46% 5% 10% 23% 14% 2	1708
	21st to end	Night	46% 7% 12% 22% 12% 1	1710
May	1st to 10th	Night	34% 8% 16% 25% 14% 4	2850
	11th to 20th	Night	34% 7% 13% 31% 15% 1	2657
	21st to end	Night	35% 9% 19% 27% 10%	2451
June	1st to 10th	Night	29% 7% 19% 31% 11% 3	1330
	11th to 20th	Night	33% 8% 16% 26% 14% 3	1330
	21st to end	Night	22% 8% 22% 31% 16% 2	1330
July	1st to 10th	Night	30% 6% 21% 29% 12% 2	2185
	11th to 20th	Night	16% 4 14% 46% 17% 3	2482
	21st to end	Night	27% 4 22% 31% 15% 2	2674
August	1st to 10th	Night	27% 5% 15% 34% 17% 3	2693
	11th to 20th	Night	33% 4 16% 34% 12% 1	2825
	21st to end	Night	29% 4 14% 34% 16% 2	3153
September	1st to 10th	Night	25% 5% 14% 33% 22% 2	1938
	11th to 20th	Night	26% 6% 20% 30% 18% 1	2090
	21st to end	Night	31% 4 12% 31% 19% 3	2090
October	1st to 10th	Night	26% 4 8% 28% 30% 3	3534
	11th to 20th	Night	36% 3 11% 33% 16% 1	3923
	21st to end	Night	40% 4 11% 29% 15% 1	4467
November	1st to 10th	Night	42% 6% 11% 22% 17% 2	2535
	11th to 20th	Night	46% 5% 13% 21% 12% 2	2705
	21st to end	Night	41% 7% 17% 25% 9% 1	2820
December	1st to 10th	Night	50% 6% 17% 18% 8% 1	2850
	11th to 20th	Night	51% 7% 16% 18% 7% 1	3516
	21st to end	Night	55% 6% 10% 19% 11% 1	5225

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	11% 12% 38% 29% 8% 2	270
	11th to 20th	Day	9% 16% 41% 25% 7% 2	270
	21st to end	Day	10% 14% 36% 27% 10% 2	297
February	1st to 10th	Day	11% 15% 42% 26% 6%	270
	11th to 20th	Day	14% 12% 45% 23% 4 1	270
	21st to end	Day	12% 11% 43% 31% 4	225
March	1st to 10th	Day	17% 12% 39% 20% 11% 1	270
	11th to 20th	Day	13% 13% 35% 28% 9% 2	270
	21st to end	Day	13% 10% 35% 24% 14% 3	310
April	1st to 10th	Day	16% 15% 38% 23% 7% 1	460
	11th to 20th	Day	26% 15% 28% 22% 8% 1	620
	21st to end	Day	22% 12% 28% 27% 9% 2	650
May	1st to 10th	Day	17% 13% 31% 27% 11% 1	653
	11th to 20th	Day	19% 9% 30% 27% 12% 3	675
	21st to end	Day	15% 13% 28% 26% 14% 2	734
June	1st to 10th	Day	10% 10% 28% 32% 14% 6%	680
	11th to 20th	Day	11% 12% 42% 25% 9% 1	680
	21st to end	Day	12% 9% 30% 34% 13% 3	680
July	1st to 10th	Day	7% 4 28% 38% 20% 4	671
	11th to 20th	Day	7% 6% 34% 36% 15% 2	668
	21st to end	Day	5% 4 27% 42% 18% 4	739
August	1st to 10th	Day	9% 4 23% 40% 20% 3	676
	11th to 20th	Day	13% 5% 24% 31% 20% 6%	665
	21st to end	Day	9% 7% 27% 34% 20% 3	741
September	1st to 10th	Day	11% 10% 30% 34% 13% 2	452
	11th to 20th	Day	15% 7% 32% 35% 10% 1	300
	21st to end	Day	18% 13% 33% 24% 9% 3	300
October	1st to 10th	Day	21% 12% 30% 24% 11% 3	300
	11th to 20th	Day	18% 13% 34% 28% 6%	300
	21st to end	Day	18% 18% 40% 17% 5% 2	330
November	1st to 10th	Day	20% 10% 36% 25% 7% 1	300
	11th to 20th	Day	11% 18% 40% 21% 8% 1	300
	21st to end	Day	13% 16% 44% 18% 8% 1	291
December	1st to 10th	Day	11% 14% 39% 26% 8% 1	270
	11th to 20th	Day	13% 14% 46% 24% 3	270
	21st to end	Day	17% 14% 40% 21% 6% 1	297
January	1st to 10th	Night	11% 13% 44% 25% 7% 1	950
	11th to 20th	Night	11% 14% 39% 27% 7% 1	950
	21st to end	Night	11% 12% 43% 27% 7%	1045
February	1st to 10th	Night	14% 12% 38% 30% 6% 1	950
	11th to 20th	Night	11% 11% 42% 26% 9% 2	854
	21st to end	Night	11% 9% 38% 29% 10% 3	628
March	1st to 10th	Night	16% 11% 35% 28% 9% 1	760
	11th to 20th	Night	15% 13% 36% 26% 10% 1	589
	21st to end	Night	14% 7% 37% 30% 11% 1	627
April	1st to 10th	Night	12% 12% 37% 32% 7%	570
	11th to 20th	Night	19% 10% 30% 32% 8%	563
	21st to end	Night	17% 11% 28% 31% 12%	570
May	1st to 10th	Night	13% 7% 34% 35% 11%	570
	11th to 20th	Night	12% 7% 33% 35% 12%	561
	21st to end	Night	14% 8% 33% 35% 9%	617
June	1st to 10th	Night	12% 6% 27% 39% 15% 1	570
	11th to 20th	Night	10% 8% 40% 34% 9%	570
	21st to end	Night	5% 6% 31% 46% 12% 1	570
July	1st to 10th	Night	7% 3 26% 47% 17%	555
	11th to 20th	Night	4 2 31% 48% 13% 1	552
	21st to end	Night	4 2 26% 51% 15% 1	624
August	1st to 10th	Night	5% 3 25% 50% 16% 1	567
	11th to 20th	Night	9% 3 27% 41% 17% 2	564
	21st to end	Night	8% 5% 27% 44% 15% 1	627
September	1st to 10th	Night	9% 5% 30% 40% 15% 2	570
	11th to 20th	Night	8% 5% 33% 39% 14% 1	570
	21st to end	Night	13% 9% 34% 32% 11% 1	570
October	1st to 10th	Night	17% 11% 29% 35% 8%	598
	11th to 20th	Night	19% 11% 33% 28% 9%	841
	21st to end	Night	17% 12% 38% 25% 7% 1	1045
November	1st to 10th	Night	14% 13% 38% 28% 7%	975
	11th to 20th	Night	11% 14% 42% 25% 8% 1	1000
	21st to end	Night	12% 14% 41% 27% 5%	986
December	1st to 10th	Night	11% 11% 43% 27% 7% 1	950
	11th to 20th	Night	15% 14% 37% 28% 6% 1	950
	21st to end	Night	18% 12% 38% 25% 5% 1	1045

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