Loeber/Elswick Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Loeber/Elswick Observatory clear sky chart from 2005-11-06 to 2026-03-03.

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	12% 8% 3 6% 4 4 4 3 5% 7% 43%	131160
	Night	13% 8% 3 7% 4 4 4 3 5% 6% 44%	130294
Transparency	Day	39% 4 11% 26% 17% 3	134759
	Night	40% 4 10% 25% 18% 3	134772
Seeing	Day	18% 12% 28% 25% 14% 4	17353
	Night	18% 12% 30% 28% 12% 1	27326

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	13% 12% 4 11% 4 4 4 2 4 5% 36%	4905
	11th to 20th	Day	7% 10% 3 9% 4 5% 4 3 4 7% 43%	5310
	21st to end	Day	16% 11% 5% 7% 4 3 3 3 4 5% 40%	5812
February	1st to 10th	Day	13% 13% 4 9% 5% 3 4 3 5% 5% 34%	1890
	11th to 20th	Day	17% 10% 3 6% 4 4 4 4 4 5% 40%	1933
	21st to end	Day	15% 10% 3 6% 4 4 3 4 5% 6% 40%	1730
March	1st to 10th	Day	16% 11% 2 5% 3 2 3 3 3 4 49%	4859
	11th to 20th	Day	10% 7% 2 5% 3 3 3 3 5% 6% 53%	4980
	21st to end	Day	13% 10% 3 8% 5% 5% 5% 4 6% 7% 33%	5571
April	1st to 10th	Day	14% 8% 2 6% 5% 4 4 4 4 7% 43%	2400
	11th to 20th	Day	17% 8% 2 5% 4 4 3 4 5% 7% 41%	2374
	21st to end	Day	19% 9% 4 8% 5% 4 4 3 5% 5% 34%	2400
May	1st to 10th	Day	16% 8% 3 7% 5% 4 5% 4 6% 9% 33%	5624
	11th to 20th	Day	14% 7% 2 7% 5% 5% 5% 4 6% 7% 38%	6126
	21st to end	Day	17% 7% 3 6% 4 4 4 3 5% 7% 40%	6935
June	1st to 10th	Day	9% 6% 2 6% 3 5% 4 4 8% 9% 44%	2800
	11th to 20th	Day	7% 5% 2 5% 4 4 5% 4 7% 10% 47%	2800
	21st to end	Day	6% 3 1 6% 4 4 5% 5% 7% 9% 51%	2800
July	1st to 10th	Day	11% 6% 2 6% 4 4 4 4 6% 9% 45%	6360
	11th to 20th	Day	6% 5% 2 7% 5% 6% 5% 4 7% 10% 41%	6096
	21st to end	Day	7% 4 2 6% 5% 4 6% 5% 8% 12% 42%	6422
August	1st to 10th	Day	5% 4 1 4 4 4 5% 4 7% 11% 51%	4234
	11th to 20th	Day	11% 6% 2 6% 3 5% 4 4 5% 8% 46%	3978
	21st to end	Day	7% 4 2 5% 4 4 4 4 6% 9% 51%	4312
September	1st to 10th	Day	11% 5% 2 5% 3 4 4 4 5% 8% 50%	2400
	11th to 20th	Day	11% 4 2 5% 4 4 4 3 6% 7% 50%	2400
	21st to end	Day	9% 5% 2 4 4 4 4 3 5% 7% 53%	2110
October	1st to 10th	Day	10% 5% 2 5% 4 3 3 3 4 6% 55%	2000
	11th to 20th	Day	16% 6% 2 4 2 2 2 2 4 5% 53%	2000
	21st to end	Day	19% 8% 2 5% 4 3 2 3 3 5% 46%	2200
November	1st to 10th	Day	11% 7% 2 5% 3 3 2 2 5% 5% 54%	1956
	11th to 20th	Day	15% 7% 3 5% 3 3 3 3 4 6% 47%	1890
	21st to end	Day	17% 11% 3 5% 2 3 3 3 3 6% 44%	1705
December	1st to 10th	Day	10% 10% 3 7% 3 3 3 3 4 5% 50%	2690
	11th to 20th	Day	11% 10% 4 6% 5% 4 3 3 4 6% 44%	3088
	21st to end	Day	21% 19% 4 10% 5% 3 3 3 3 4 24%	4070
January	1st to 10th	Night	13% 11% 6% 11% 5% 3 4 3 3 4 37%	8015
	11th to 20th	Night	9% 9% 3 12% 5% 5% 5% 3 4 3 42%	7680
	21st to end	Night	15% 12% 4 8% 5% 4 4 2 3 5% 39%	8402
February	1st to 10th	Night	14% 12% 3 8% 4 4 3 3 5% 5% 37%	2730
	11th to 20th	Night	15% 9% 3 8% 5% 4 3 3 4 6% 40%	2573
	21st to end	Night	15% 10% 3 6% 4 4 3 3 5% 4 42%	2076
March	1st to 10th	Night	17% 11% 3 5% 3 3 3 3 4 5% 44%	5082
	11th to 20th	Night	11% 9% 2 5% 3 2 3 3 5% 7% 50%	4980
	21st to end	Night	15% 10% 3 8% 5% 5% 5% 4 5% 6% 34%	5343
April	1st to 10th	Night	12% 7% 3 6% 3 3 3 3 5% 6% 49%	2000
	11th to 20th	Night	16% 9% 2 5% 3 3 3 3 5% 6% 47%	1975
	21st to end	Night	18% 7% 3 6% 4 4 4 4 4 8% 39%	2000
May	1st to 10th	Night	16% 9% 3 6% 4 3 4 3 6% 8% 37%	4278
	11th to 20th	Night	12% 8% 3 7% 4 4 4 4 6% 8% 41%	3785
	21st to end	Night	15% 7% 2 7% 5% 3 4 3 6% 8% 40%	3942
June	1st to 10th	Night	9% 4 2 5% 5% 4 4 4 6% 7% 50%	1600
	11th to 20th	Night	7% 3 2 5% 4 3 5% 4 7% 11% 51%	1600
	21st to end	Night	4 3 1 4 3 3 3 4 7% 10% 59%	1600
July	1st to 10th	Night	10% 5% 2 6% 4 4 4 4 5% 9% 47%	3618
	11th to 20th	Night	5% 4 2 7% 4 5% 4 4 6% 9% 51%	3863
	21st to end	Night	5% 4 2 6% 4 4 5% 5% 7% 10% 47%	4449
August	1st to 10th	Night	4 2 1 4 3 3 4 3 5% 9% 62%	2926
	11th to 20th	Night	10% 5% 2 6% 3 3 4 3 5% 8% 50%	3074
	21st to end	Night	5% 4 1 4 3 3 3 3 6% 9% 59%	3586
September	1st to 10th	Night	12% 4 1 6% 3 3 3 3 5% 6% 55%	2000
	11th to 20th	Night	9% 5% 2 5% 4 4 4 4 5% 8% 51%	2000
	21st to end	Night	9% 5% 2 5% 4 3 3 3 4 6% 56%	2265
October	1st to 10th	Night	7% 4 1 5% 3 3 3 3 4 7% 61%	2400
	11th to 20th	Night	14% 6% 2 5% 3 3 3 2 4 5% 53%	2400
	21st to end	Night	18% 8% 2 4 3 3 3 2 3 4 49%	2640
November	1st to 10th	Night	11% 6% 2 5% 3 3 2 3 4 6% 55%	2560
	11th to 20th	Night	13% 6% 3 6% 4 3 3 3 4 6% 51%	2730
	21st to end	Night	17% 10% 3 5% 3 3 3 2 4 4 45%	2913
December	1st to 10th	Night	10% 9% 3 7% 3 3 3 3 5% 6% 47%	4720
	11th to 20th	Night	15% 10% 3 6% 4 4 4 3 4 5% 43%	5339
	21st to end	Night	22% 18% 5% 9% 4 4 3 3 3 4 25%	7150

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	51% 3 10% 23% 11% 2	4906
	11th to 20th	Day	42% 3 9% 25% 17% 4	5310
	21st to end	Day	48% 3 9% 18% 17% 5%	5812
February	1st to 10th	Day	53% 3 9% 22% 12% 1	1890
	11th to 20th	Day	48% 3 10% 20% 15% 4	1942
	21st to end	Day	46% 3 7% 24% 15% 4	1730
March	1st to 10th	Day	42% 2 6% 22% 22% 6%	4859
	11th to 20th	Day	32% 3 8% 24% 25% 7%	4980
	21st to end	Day	48% 6% 12% 26% 7%	5573
April	1st to 10th	Day	40% 4 11% 25% 18% 2	2400
	11th to 20th	Day	44% 4 10% 24% 16% 3	2374
	21st to end	Day	52% 4 10% 20% 13% 1	2400
May	1st to 10th	Day	46% 6% 12% 22% 13% 1	5659
	11th to 20th	Day	44% 6% 10% 24% 14% 3	6130
	21st to end	Day	44% 5% 8% 25% 17% 1	6949
June	1st to 10th	Day	34% 7% 15% 27% 16% 2	2800
	11th to 20th	Day	31% 6% 13% 29% 18% 4	2800
	21st to end	Day	27% 6% 17% 30% 15% 5%	2800
July	1st to 10th	Day	36% 5% 11% 27% 19% 2	6291
	11th to 20th	Day	36% 6% 15% 30% 12% 1	6022
	21st to end	Day	33% 7% 17% 32% 9% 1	6240
August	1st to 10th	Day	26% 6% 17% 35% 16%	4220
	11th to 20th	Day	37% 5% 13% 27% 16% 1	4017
	21st to end	Day	29% 6% 14% 35% 14% 3	4311
September	1st to 10th	Day	34% 4 11% 27% 20% 5%	2400
	11th to 20th	Day	33% 4 9% 28% 24% 3	2400
	21st to end	Day	31% 5% 8% 28% 26% 3	2110
October	1st to 10th	Day	19% 2 5% 19% 42% 13%	3260
	11th to 20th	Day	23% 2 4 23% 37% 11%	3240
	21st to end	Day	34% 2 7% 28% 27% 2	3538
November	1st to 10th	Day	34% 2 12% 26% 22% 5%	1956
	11th to 20th	Day	39% 3 8% 24% 22% 5%	1890
	21st to end	Day	44% 3 8% 28% 15% 1	1705
December	1st to 10th	Day	39% 2 9% 34% 15% 1	2690
	11th to 20th	Day	44% 2 10% 26% 16% 1	3085
	21st to end	Day	65% 4 11% 13% 7% 1	4070
January	1st to 10th	Night	53% 3 11% 24% 9% 1	8016
	11th to 20th	Night	48% 3 6% 25% 16% 3	7680
	21st to end	Night	51% 2 10% 20% 14% 2	8402
February	1st to 10th	Night	50% 3 10% 21% 14% 2	2730
	11th to 20th	Night	46% 3 9% 23% 16% 3	2574
	21st to end	Night	45% 3 9% 22% 17% 4	2076
March	1st to 10th	Night	45% 2 7% 22% 20% 3	5082
	11th to 20th	Night	35% 3 8% 23% 23% 7%	4980
	21st to end	Night	50% 6% 11% 23% 10% 1	5343
April	1st to 10th	Night	36% 4 12% 26% 19% 4	2000
	11th to 20th	Night	39% 3 10% 25% 17% 6%	1975
	21st to end	Night	46% 3 10% 24% 16% 1	2000
May	1st to 10th	Night	45% 7% 13% 20% 14% 1	4308
	11th to 20th	Night	41% 6% 11% 22% 16% 5%	3786
	21st to end	Night	43% 6% 11% 22% 16% 2	3950
June	1st to 10th	Night	32% 5% 14% 29% 17% 3	1600
	11th to 20th	Night	27% 5% 12% 28% 24% 4	1600
	21st to end	Night	21% 5% 17% 29% 20% 7%	1600
July	1st to 10th	Night	36% 4 11% 25% 22% 2	3580
	11th to 20th	Night	30% 6% 13% 35% 15% 1	3817
	21st to end	Night	29% 7% 18% 33% 12%	4320
August	1st to 10th	Night	20% 5% 20% 32% 22% 1	2916
	11th to 20th	Night	33% 4 15% 29% 17% 3	3101
	21st to end	Night	22% 5% 16% 36% 17% 4	3586
September	1st to 10th	Night	31% 4 11% 25% 24% 6%	2000
	11th to 20th	Night	31% 5% 10% 24% 26% 4	2000
	21st to end	Night	30% 4 8% 26% 28% 4	2265
October	1st to 10th	Night	15% 2 5% 21% 46% 10%	3920
	11th to 20th	Night	24% 2 6% 21% 32% 14%	3899
	21st to end	Night	34% 3 7% 27% 26% 3	4252
November	1st to 10th	Night	31% 3 11% 29% 20% 6%	2560
	11th to 20th	Night	36% 2 7% 26% 24% 4	2730
	21st to end	Night	44% 3 9% 26% 17% 2	2913
December	1st to 10th	Night	39% 3 9% 34% 14% 1	4720
	11th to 20th	Night	46% 2 11% 23% 17% 1	5341
	21st to end	Night	64% 4 11% 15% 6% 1	7150

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	25% 22% 37% 14% 2	330
	11th to 20th	Day	33% 20% 38% 8% 1	330
	21st to end	Day	23% 26% 37% 12% 2	363
February	1st to 10th	Day	28% 20% 35% 15% 1	330
	11th to 20th	Day	34% 24% 29% 11% 3	330
	21st to end	Day	32% 21% 34% 11% 1	273
March	1st to 10th	Day	25% 24% 40% 10% 1	306
	11th to 20th	Day	33% 18% 34% 12% 2 1	300
	21st to end	Day	36% 22% 28% 13% 1	375
April	1st to 10th	Day	27% 15% 35% 18% 5% 1	500
	11th to 20th	Day	30% 19% 29% 16% 5% 1	492
	21st to end	Day	27% 15% 34% 19% 5%	500
May	1st to 10th	Day	20% 16% 34% 24% 5% 1	592
	11th to 20th	Day	21% 14% 27% 25% 11% 2	725
	21st to end	Day	16% 11% 30% 24% 13% 5%	789
June	1st to 10th	Day	10% 7% 24% 33% 19% 7%	730
	11th to 20th	Day	9% 5% 23% 40% 20% 3	730
	21st to end	Day	6% 7% 32% 35% 15% 4	730
July	1st to 10th	Day	13% 3 17% 29% 29% 9%	721
	11th to 20th	Day	6% 5% 21% 38% 25% 5%	718
	21st to end	Day	9% 4 17% 36% 28% 7%	794
August	1st to 10th	Day	9% 4 18% 39% 25% 5%	726
	11th to 20th	Day	10% 4 19% 35% 26% 7%	600
	21st to end	Day	9% 3 19% 31% 28% 10%	583
September	1st to 10th	Day	13% 4 15% 34% 26% 7%	530
	11th to 20th	Day	9% 2 20% 31% 28% 10%	530
	21st to end	Day	13% 9% 22% 32% 19% 5%	390
October	1st to 10th	Day	13% 8% 34% 28% 14% 4	330
	11th to 20th	Day	22% 18% 33% 18% 8% 1	330
	21st to end	Day	34% 18% 31% 15% 1	363
November	1st to 10th	Day	17% 14% 42% 19% 7% 2	330
	11th to 20th	Day	27% 18% 30% 18% 5% 2	330
	21st to end	Day	30% 17% 29% 18% 5% 1	330
December	1st to 10th	Day	20% 25% 34% 15% 6% 1	330
	11th to 20th	Day	26% 19% 38% 14% 4	330
	21st to end	Day	27% 25% 35% 11% 2	363
January	1st to 10th	Night	20% 19% 36% 21% 4	1050
	11th to 20th	Night	24% 21% 34% 17% 3	1050
	21st to end	Night	20% 20% 37% 22% 1	1155
February	1st to 10th	Night	22% 18% 38% 20% 2	1050
	11th to 20th	Night	24% 19% 36% 20% 2	939
	21st to end	Night	26% 17% 37% 18% 2	692
March	1st to 10th	Night	22% 19% 36% 21% 3	674
	11th to 20th	Night	24% 13% 35% 25% 4	600
	21st to end	Night	28% 15% 36% 19% 3	660
April	1st to 10th	Night	18% 19% 35% 25% 4	600
	11th to 20th	Night	23% 13% 33% 26% 5%	593
	21st to end	Night	22% 11% 38% 23% 6%	600
May	1st to 10th	Night	17% 6% 37% 31% 8% 1	600
	11th to 20th	Night	16% 9% 28% 32% 14% 1	591
	21st to end	Night	13% 6% 28% 33% 19% 1	650
June	1st to 10th	Night	11% 4 20% 39% 25% 2	600
	11th to 20th	Night	7% 3 24% 45% 20% 1	600
	21st to end	Night	4 3 27% 46% 18% 2	600
July	1st to 10th	Night	11% 3 13% 34% 33% 6%	585
	11th to 20th	Night	3 4 16% 45% 30% 2	582
	21st to end	Night	6% 2 15% 41% 32% 3	657
August	1st to 10th	Night	6% 3 14% 43% 32% 2	597
	11th to 20th	Night	8% 2 13% 41% 32% 3	594
	21st to end	Night	7% 2 13% 40% 35% 3	660
September	1st to 10th	Night	13% 2 16% 39% 27% 5%	600
	11th to 20th	Night	11% 3 15% 38% 29% 4	600
	21st to end	Night	11% 6% 23% 33% 24% 3	729
October	1st to 10th	Night	9% 7% 26% 34% 22% 3	800
	11th to 20th	Night	16% 11% 35% 27% 10% 1	800
	21st to end	Night	24% 13% 32% 24% 6%	880
November	1st to 10th	Night	14% 13% 37% 28% 8%	820
	11th to 20th	Night	19% 15% 33% 26% 7%	840
	21st to end	Night	25% 15% 32% 22% 5%	1023
December	1st to 10th	Night	23% 15% 35% 22% 4 1	1050
	11th to 20th	Night	24% 15% 34% 23% 4	1050
	21st to end	Night	27% 18% 32% 20% 2	1155

Page generated at 2026-02-28 00:40:20. Version ac07

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