Baltimore Bend
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Baltimore Bend clear sky chart from 2005-11-06 to 2026-07-16.

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% 7% 3 6% 4 4 4 3 5% 7% 44%	138108
	Night	12% 7% 3 7% 4 4 4 3 5% 6% 46%	134863
Transparency	Day	39% 5% 12% 25% 16% 2	141716
	Night	38% 5% 12% 25% 18% 3	139335
Seeing	Day	14% 9% 27% 28% 17% 5%	18009
	Night	14% 8% 31% 32% 12% 1	27820

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	14% 10% 4 11% 4 4 4 3 4 6% 37%	5153
	11th to 20th	Day	6% 8% 3 9% 6% 7% 6% 4 5% 6% 41%	5310
	21st to end	Day	14% 13% 4 9% 4 4 3 2 3 4 37%	5812
February	1st to 10th	Day	15% 11% 3 8% 5% 4 3 3 4 8% 35%	1890
	11th to 20th	Day	14% 10% 4 6% 5% 4 3 3 5% 7% 38%	1844
	21st to end	Day	12% 8% 3 7% 4 4 3 3 5% 6% 44%	1760
March	1st to 10th	Day	16% 9% 3 5% 3 3 3 2 3 4 50%	5046
	11th to 20th	Day	10% 6% 2 5% 3 3 4 3 5% 6% 53%	5090
	21st to end	Day	15% 11% 3 8% 5% 4 4 4 5% 7% 33%	5583
April	1st to 10th	Day	16% 7% 3 7% 4 4 4 3 5% 6% 43%	2488
	11th to 20th	Day	16% 8% 3 6% 4 4 4 4 5% 6% 41%	2494
	21st to end	Day	21% 7% 3 7% 5% 5% 5% 3 6% 6% 33%	2581
May	1st to 10th	Day	14% 6% 2 6% 4 4 5% 3 5% 7% 42%	7617
	11th to 20th	Day	14% 6% 2 6% 4 4 4 3 6% 7% 45%	7645
	21st to end	Day	19% 7% 3 7% 4 4 4 3 5% 7% 38%	9047
June	1st to 10th	Day	8% 4 2 5% 4 5% 5% 4 7% 10% 46%	2940
	11th to 20th	Day	8% 6% 2 6% 5% 4 4 5% 7% 9% 45%	2940
	21st to end	Day	7% 4 2 6% 4 4 5% 4 7% 9% 47%	2940
July	1st to 10th	Day	10% 5% 2 6% 4 4 4 3 5% 8% 47%	6436
	11th to 20th	Day	9% 5% 2 6% 4 4 4 4 6% 9% 47%	5966
	21st to end	Day	8% 5% 2 6% 5% 4 5% 4 7% 11% 43%	6422
August	1st to 10th	Day	5% 3 2 5% 4 4 5% 4 6% 10% 53%	4234
	11th to 20th	Day	12% 4 2 5% 4 4 4 4 5% 8% 48%	4171
	21st to end	Day	6% 3 2 5% 4 4 5% 4 6% 8% 54%	4312
September	1st to 10th	Day	11% 4 2 4 3 3 5% 3 5% 7% 54%	2400
	11th to 20th	Day	10% 4 2 5% 4 3 4 3 6% 9% 50%	2318
	21st to end	Day	10% 5% 2 5% 4 3 4 3 4 6% 55%	2130
October	1st to 10th	Day	12% 5% 2 4 3 4 3 3 5% 6% 54%	2000
	11th to 20th	Day	13% 6% 2 4 3 3 3 2 4 5% 54%	2000
	21st to end	Day	18% 7% 3 6% 3 3 3 2 4 5% 46%	2200
November	1st to 10th	Day	11% 7% 1 5% 4 2 3 3 4 5% 54%	2058
	11th to 20th	Day	14% 6% 2 5% 4 3 3 3 4 5% 50%	1753
	21st to end	Day	18% 9% 4 7% 3 3 2 3 4 5% 43%	1680
December	1st to 10th	Day	7% 7% 3 7% 4 3 3 3 5% 6% 53%	2690
	11th to 20th	Day	12% 8% 4 7% 4 3 4 3 3 5% 46%	3088
	21st to end	Day	18% 18% 8% 12% 4 4 4 3 4 4 23%	4070
January	1st to 10th	Night	12% 10% 5% 13% 5% 4 4 2 3 4 37%	7752
	11th to 20th	Night	9% 8% 3 8% 4 5% 4 4 4 5% 45%	7680
	21st to end	Night	13% 11% 4 9% 5% 5% 4 3 4 5% 37%	8402
February	1st to 10th	Night	13% 10% 3 8% 5% 5% 4 3 5% 6% 38%	2730
	11th to 20th	Night	13% 9% 3 7% 5% 4 4 3 5% 6% 41%	2663
	21st to end	Night	13% 8% 3 6% 4 2 3 3 5% 5% 46%	2060
March	1st to 10th	Night	17% 10% 3 5% 3 3 3 2 3 5% 46%	5029
	11th to 20th	Night	11% 6% 2 4 3 3 3 3 4 6% 55%	5090
	21st to end	Night	15% 9% 4 8% 5% 4 4 4 6% 7% 35%	5588
April	1st to 10th	Night	12% 7% 2 5% 5% 4 3 3 5% 6% 49%	2132
	11th to 20th	Night	14% 7% 3 6% 3 4 4 3 4 6% 47%	2075
	21st to end	Night	18% 8% 3 6% 3 4 3 3 4 6% 40%	2035
May	1st to 10th	Night	15% 6% 2 7% 4 3 5% 4 5% 7% 43%	5266
	11th to 20th	Night	13% 6% 2 5% 4 3 4 3 5% 9% 47%	5231
	21st to end	Night	16% 6% 2 7% 4 4 4 4 5% 6% 41%	5139
June	1st to 10th	Night	7% 3 2 3 4 4 4 4 6% 10% 54%	1680
	11th to 20th	Night	6% 4 2 5% 4 4 5% 3 7% 10% 51%	1680
	21st to end	Night	5% 3 1 4 3 5% 4 3 6% 8% 57%	1680
July	1st to 10th	Night	10% 5% 2 5% 3 3 3 3 6% 8% 51%	3744
	11th to 20th	Night	7% 4 2 6% 4 4 5% 3 6% 9% 51%	4122
	21st to end	Night	8% 3 2 6% 4 4 5% 5% 8% 11% 45%	4449
August	1st to 10th	Night	3 2 1 3 3 3 3 4 6% 10% 61%	2926
	11th to 20th	Night	11% 6% 1 4 4 3 3 3 4 6% 53%	2888
	21st to end	Night	4 3 2 5% 3 4 5% 3 5% 8% 58%	3584
September	1st to 10th	Night	10% 5% 2 5% 4 2 4 2 4 6% 56%	2000
	11th to 20th	Night	9% 5% 1 4 3 3 4 4 5% 8% 54%	2078
	21st to end	Night	8% 5% 2 5% 3 4 4 3 5% 6% 57%	2250
October	1st to 10th	Night	10% 5% 2 4 3 3 3 3 5% 5% 58%	2400
	11th to 20th	Night	14% 4 2 5% 3 3 3 2 4 5% 55%	2400
	21st to end	Night	16% 8% 2 5% 3 2 3 3 3 5% 51%	2640
November	1st to 10th	Night	11% 5% 2 4 3 3 3 3 4 6% 58%	2460
	11th to 20th	Night	12% 6% 2 5% 4 3 4 3 4 6% 52%	2861
	21st to end	Night	16% 8% 3 5% 3 3 3 2 4 5% 47%	2940
December	1st to 10th	Night	8% 6% 3 6% 4 4 4 4 5% 6% 52%	4720
	11th to 20th	Night	14% 7% 4 7% 4 4 3 3 5% 6% 44%	5339
	21st to end	Night	22% 15% 4 9% 4 3 3 2 4 4 28%	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	49% 4 11% 24% 11% 2	5154
	11th to 20th	Day	45% 3 12% 23% 14% 5%	5310
	21st to end	Day	51% 3 12% 17% 15% 2	5812
February	1st to 10th	Day	49% 5% 13% 22% 10% 1	1890
	11th to 20th	Day	46% 6% 11% 21% 13% 3	1853
	21st to end	Day	41% 4 12% 23% 17% 2	1760
March	1st to 10th	Day	40% 3 7% 25% 22% 4	5046
	11th to 20th	Day	33% 4 9% 22% 26% 6%	5090
	21st to end	Day	49% 6% 16% 23% 5% 1	5585
April	1st to 10th	Day	42% 6% 12% 24% 14% 1	2488
	11th to 20th	Day	44% 5% 12% 23% 14% 2	2494
	21st to end	Day	49% 7% 11% 22% 10% 1	2581
May	1st to 10th	Day	41% 7% 13% 26% 13%	7655
	11th to 20th	Day	38% 5% 14% 25% 17% 2	7649
	21st to end	Day	46% 6% 9% 26% 13% 1	9061
June	1st to 10th	Day	30% 8% 17% 29% 14% 1	2940
	11th to 20th	Day	33% 8% 14% 27% 16% 2	2940
	21st to end	Day	31% 8% 16% 28% 14% 4	2940
July	1st to 10th	Day	35% 6% 13% 26% 18% 2	6368
	11th to 20th	Day	34% 6% 15% 29% 14% 2	5897
	21st to end	Day	32% 8% 17% 33% 10%	6240
August	1st to 10th	Day	26% 7% 18% 31% 18% 1	4220
	11th to 20th	Day	34% 6% 15% 28% 16% 1	4210
	21st to end	Day	27% 6% 14% 34% 14% 5%	4311
September	1st to 10th	Day	30% 6% 13% 26% 19% 6%	2400
	11th to 20th	Day	30% 6% 13% 25% 22% 3	2318
	21st to end	Day	30% 6% 9% 29% 23% 3	2130
October	1st to 10th	Day	20% 3 7% 21% 40% 10%	3260
	11th to 20th	Day	22% 2 5% 22% 40% 8%	3240
	21st to end	Day	36% 4 8% 25% 25% 3	3538
November	1st to 10th	Day	33% 4 14% 26% 19% 4	2058
	11th to 20th	Day	37% 3 10% 27% 20% 3	1753
	21st to end	Day	45% 3 9% 27% 15% 1	1680
December	1st to 10th	Day	33% 4 16% 30% 17%	2690
	11th to 20th	Day	41% 4 14% 30% 10% 1	3085
	21st to end	Day	66% 4 11% 12% 5% 1	4070
January	1st to 10th	Night	52% 3 12% 22% 10% 1	7753
	11th to 20th	Night	42% 3 10% 24% 17% 4	7680
	21st to end	Night	50% 4 12% 17% 14% 3	8402
February	1st to 10th	Night	47% 5% 11% 21% 13% 2	2730
	11th to 20th	Night	44% 5% 11% 21% 16% 3	2664
	21st to end	Night	39% 5% 10% 22% 20% 4	2060
March	1st to 10th	Night	42% 4 7% 21% 23% 3	5029
	11th to 20th	Night	31% 3 6% 26% 27% 6%	5090
	21st to end	Night	47% 6% 14% 23% 8% 2	5588
April	1st to 10th	Night	36% 6% 10% 25% 20% 4	2132
	11th to 20th	Night	38% 5% 10% 26% 17% 4	2075
	21st to end	Night	44% 5% 11% 23% 16% 1	2035
May	1st to 10th	Night	40% 6% 13% 25% 15% 1	5293
	11th to 20th	Night	35% 6% 12% 23% 19% 5%	5232
	21st to end	Night	43% 7% 9% 21% 19% 1	5149
June	1st to 10th	Night	25% 7% 16% 31% 17% 3	1680
	11th to 20th	Night	28% 7% 12% 28% 20% 4	1680
	21st to end	Night	23% 6% 16% 31% 19% 5%	1680
July	1st to 10th	Night	31% 5% 12% 26% 23% 2	3706
	11th to 20th	Night	29% 6% 17% 30% 17% 2	4071
	21st to end	Night	29% 7% 18% 36% 10% 1	4320
August	1st to 10th	Night	17% 6% 22% 28% 25% 2	2916
	11th to 20th	Night	33% 4 10% 29% 22% 1	2915
	21st to end	Night	24% 6% 14% 35% 17% 4	3584
September	1st to 10th	Night	29% 6% 10% 23% 25% 7%	2000
	11th to 20th	Night	28% 5% 12% 26% 23% 5%	2078
	21st to end	Night	28% 6% 9% 26% 28% 4	2250
October	1st to 10th	Night	17% 3 6% 20% 45% 9%	3920
	11th to 20th	Night	23% 3 6% 24% 30% 14%	3899
	21st to end	Night	35% 3 7% 28% 25% 3	4252
November	1st to 10th	Night	29% 5% 12% 27% 22% 5%	2460
	11th to 20th	Night	33% 4 10% 25% 23% 4	2861
	21st to end	Night	41% 4 10% 27% 16% 2	2940
December	1st to 10th	Night	32% 4 14% 34% 15% 1	4720
	11th to 20th	Night	41% 4 14% 26% 14% 1	5341
	21st to end	Night	61% 4 12% 16% 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	20% 14% 36% 23% 6%	330
	11th to 20th	Day	24% 17% 39% 18% 2	330
	21st to end	Day	15% 14% 43% 23% 4	363
February	1st to 10th	Day	22% 14% 42% 18% 4	330
	11th to 20th	Day	20% 18% 38% 17% 6%	330
	21st to end	Day	13% 22% 42% 20% 4	273
March	1st to 10th	Day	18% 18% 43% 19% 3	330
	11th to 20th	Day	28% 11% 32% 23% 5%	330
	21st to end	Day	30% 22% 31% 13% 4	363
April	1st to 10th	Day	21% 19% 32% 22% 6% 1	508
	11th to 20th	Day	21% 15% 36% 21% 6% 1	532
	21st to end	Day	21% 13% 34% 22% 9% 1	601
May	1st to 10th	Day	16% 12% 36% 27% 9% 1	753
	11th to 20th	Day	18% 10% 29% 27% 14% 3	775
	21st to end	Day	15% 9% 26% 29% 17% 5%	844
June	1st to 10th	Day	8% 4 21% 33% 25% 9%	780
	11th to 20th	Day	10% 4 25% 34% 24% 4	780
	21st to end	Day	6% 5% 32% 37% 18% 3	780
July	1st to 10th	Day	10% 4 14% 28% 30% 14%	771
	11th to 20th	Day	5% 2 19% 35% 29% 10%	744
	21st to end	Day	7% 3 15% 32% 33% 10%	794
August	1st to 10th	Day	6% 2 17% 37% 31% 6%	726
	11th to 20th	Day	9% 3 16% 34% 30% 8%	715
	21st to end	Day	7% 2 13% 31% 33% 14%	583
September	1st to 10th	Day	11% 2 16% 34% 30% 8%	530
	11th to 20th	Day	8% 2 15% 32% 33% 9%	448
	21st to end	Day	11% 8% 21% 28% 25% 7%	330
October	1st to 10th	Day	13% 5% 28% 28% 18% 8%	330
	11th to 20th	Day	10% 17% 36% 26% 11% 1	330
	21st to end	Day	26% 16% 31% 20% 6%	363
November	1st to 10th	Day	18% 8% 38% 24% 8% 4	330
	11th to 20th	Day	16% 15% 33% 24% 9% 2	330
	21st to end	Day	24% 15% 28% 25% 8% 1	330
December	1st to 10th	Day	11% 17% 38% 24% 8% 2	330
	11th to 20th	Day	18% 16% 37% 20% 8% 1	330
	21st to end	Day	20% 19% 39% 20% 2	363
January	1st to 10th	Night	15% 11% 40% 28% 7%	1050
	11th to 20th	Night	17% 13% 41% 24% 5% 1	1050
	21st to end	Night	16% 12% 40% 29% 3	1155
February	1st to 10th	Night	17% 10% 44% 25% 4	1050
	11th to 20th	Night	17% 14% 37% 29% 4	1029
	21st to end	Night	17% 13% 45% 20% 3	676
March	1st to 10th	Night	18% 12% 41% 26% 3	630
	11th to 20th	Night	18% 10% 37% 28% 5% 1	630
	21st to end	Night	25% 12% 38% 20% 4	693
April	1st to 10th	Night	15% 14% 37% 29% 4	630
	11th to 20th	Night	17% 14% 35% 27% 7%	623
	21st to end	Night	19% 9% 37% 28% 7%	630
May	1st to 10th	Night	17% 7% 32% 36% 7% 1	630
	11th to 20th	Night	14% 8% 26% 36% 15% 1	621
	21st to end	Night	13% 6% 29% 33% 18% 2	683
June	1st to 10th	Night	8% 3 20% 45% 22% 3	630
	11th to 20th	Night	7% 3 24% 45% 19% 2	630
	21st to end	Night	6% 3 28% 46% 18% 1	630
July	1st to 10th	Night	9% 3 9% 43% 32% 4	615
	11th to 20th	Night	5% 2 15% 45% 32% 2	597
	21st to end	Night	7% 2 11% 43% 35% 2	657
August	1st to 10th	Night	5% 2 14% 46% 31% 2	597
	11th to 20th	Night	8% 2 11% 43% 32% 3	594
	21st to end	Night	5% 2 12% 43% 36% 3	660
September	1st to 10th	Night	11% 3 16% 40% 28% 4	600
	11th to 20th	Night	11% 1 17% 38% 29% 4	600
	21st to end	Night	8% 5% 22% 41% 22% 3	650
October	1st to 10th	Night	11% 4 28% 35% 19% 2	800
	11th to 20th	Night	15% 8% 36% 31% 10%	800
	21st to end	Night	20% 11% 34% 27% 8%	880
November	1st to 10th	Night	13% 9% 34% 34% 9%	820
	11th to 20th	Night	14% 11% 37% 29% 9%	975
	21st to end	Night	21% 11% 35% 28% 5%	1050
December	1st to 10th	Night	17% 10% 39% 28% 5% 1	1050
	11th to 20th	Night	18% 10% 37% 30% 4	1050
	21st to end	Night	21% 13% 36% 27% 3	1155

Page generated at 2026-07-13 02:14:50. Version ac07

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