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 2024-02-15.

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% 7% 3 6% 5% 3 4 4 5% 7% 42%	78443
	Night	13% 7% 3 6% 5% 3 4 4 5% 6% 45%	80671
Transparency	Day	41% 6% 13% 24% 14% 2	78162
	Night	39% 5% 12% 24% 16% 3	80473
Seeing	Day	14% 9% 26% 28% 18% 5%	14614
	Night	15% 8% 31% 33% 13% 1	24653

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	15% 9% 5% 10% 6% 3 4 4 4 6% 34%	2765
	11th to 20th	Day	12% 11% 4 9% 6% 5% 8% 4 3 4 35%	2850
	21st to end	Day	16% 16% 5% 10% 5% 4 4 4 3 5% 28%	3135
February	1st to 10th	Day	16% 11% 5% 7% 6% 3 4 3 4 7% 34%	1710
	11th to 20th	Day	13% 9% 4 6% 6% 2 4 4 5% 8% 38%	1610
	21st to end	Day	14% 9% 4 7% 6% 3 3 4 4 6% 40%	1505
March	1st to 10th	Day	12% 10% 4 6% 6% 3 3 4 4 6% 40%	1980
	11th to 20th	Day	19% 10% 4 6% 5% 3 4 3 5% 7% 33%	1980
	21st to end	Day	23% 10% 5% 7% 6% 3 4 5% 4 5% 28%	2178
April	1st to 10th	Day	15% 6% 3 6% 5% 3 5% 3 5% 7% 43%	2132
	11th to 20th	Day	16% 9% 3 5% 5% 2 4 5% 4 6% 40%	2134
	21st to end	Day	22% 6% 3 6% 5% 4 4 4 5% 6% 35%	2212
May	1st to 10th	Day	16% 8% 3 7% 6% 3 6% 5% 5% 6% 36%	2340
	11th to 20th	Day	17% 7% 3 6% 5% 3 3 4 6% 7% 38%	2306
	21st to end	Day	13% 6% 3 7% 6% 4 6% 5% 5% 8% 35%	2725
June	1st to 10th	Day	7% 3 2 4 5% 4 5% 5% 7% 10% 48%	2520
	11th to 20th	Day	8% 6% 3 5% 5% 3 5% 5% 6% 9% 46%	2520
	21st to end	Day	7% 4 2 5% 5% 3 5% 6% 6% 10% 48%	2520
July	1st to 10th	Day	9% 4 2 5% 4 3 5% 5% 7% 10% 46%	2499
	11th to 20th	Day	5% 4 2 4 4 3 5% 5% 6% 9% 54%	2340
	21st to end	Day	9% 5% 2 5% 5% 3 5% 5% 6% 9% 47%	2546
August	1st to 10th	Day	8% 4 2 6% 6% 3 4 5% 7% 9% 46%	2328
	11th to 20th	Day	9% 5% 3 4 4 3 5% 5% 5% 9% 48%	2301
	21st to end	Day	8% 3 2 3 4 3 4 5% 6% 8% 53%	2376
September	1st to 10th	Day	12% 4 2 3 4 2 4 4 5% 7% 53%	2160
	11th to 20th	Day	10% 4 2 4 4 2 4 4 5% 9% 52%	2087
	21st to end	Day	8% 5% 2 4 5% 2 4 4 4 6% 56%	1918
October	1st to 10th	Day	13% 5% 2 4 4 3 3 3 5% 7% 52%	1800
	11th to 20th	Day	14% 6% 2 4 4 2 3 3 4 5% 53%	1800
	21st to end	Day	18% 7% 3 5% 4 2 3 3 4 5% 45%	1980
November	1st to 10th	Day	11% 6% 2 4 4 2 3 4 4 5% 54%	1858
	11th to 20th	Day	15% 6% 3 4 5% 2 3 4 4 6% 49%	1587
	21st to end	Day	17% 8% 4 6% 4 2 2 3 4 5% 45%	1520
December	1st to 10th	Day	11% 8% 5% 8% 6% 3 4 3 5% 6% 43%	1520
	11th to 20th	Day	13% 10% 5% 6% 6% 3 4 4 4 5% 41%	1918
	21st to end	Day	17% 14% 8% 11% 5% 4 4 4 4 4 25%	2783
January	1st to 10th	Night	10% 9% 5% 12% 7% 3 5% 3 3 5% 36%	4172
	11th to 20th	Night	13% 10% 4 7% 6% 5% 7% 6% 5% 5% 33%	4120
	21st to end	Night	17% 12% 6% 9% 5% 3 4 4 3 5% 30%	4532
February	1st to 10th	Night	14% 9% 4 7% 5% 4 5% 4 5% 6% 37%	2470
	11th to 20th	Night	13% 8% 4 7% 5% 3 4 5% 5% 6% 42%	2332
	21st to end	Night	14% 9% 3 6% 4 1 3 4 5% 6% 43%	1763
March	1st to 10th	Night	14% 7% 3 5% 4 2 4 4 4 7% 47%	1980
	11th to 20th	Night	18% 7% 3 6% 5% 3 4 4 5% 6% 39%	1980
	21st to end	Night	22% 10% 4 6% 6% 3 4 4 5% 6% 31%	2178
April	1st to 10th	Night	11% 6% 2 5% 5% 3 4 4 5% 6% 50%	1828
	11th to 20th	Night	15% 7% 3 6% 3 3 3 4 4 5% 48%	1775
	21st to end	Night	18% 7% 3 6% 4 3 3 4 4 6% 42%	1745
May	1st to 10th	Night	16% 5% 2 6% 5% 3 4 6% 6% 8% 40%	1620
	11th to 20th	Night	14% 5% 2 5% 4 3 4 4 4 8% 46%	1587
	21st to end	Night	12% 5% 2 6% 5% 4 4 6% 6% 9% 42%	1551
June	1st to 10th	Night	6% 3 1 3 4 2 4 5% 6% 11% 55%	1440
	11th to 20th	Night	6% 3 2 5% 5% 3 5% 5% 7% 10% 51%	1440
	21st to end	Night	5% 2 1 4 3 3 4 4 6% 9% 59%	1440
July	1st to 10th	Night	9% 4 1 3 4 3 3 4 7% 9% 52%	1457
	11th to 20th	Night	4 3 1 3 4 3 4 4 6% 9% 60%	1620
	21st to end	Night	6% 2 2 5% 5% 3 4 6% 6% 10% 51%	1772
August	1st to 10th	Night	5% 3 2 4 4 3 5% 4 6% 10% 53%	1611
	11th to 20th	Night	6% 4 2 3 4 2 5% 4 5% 8% 57%	1600
	21st to end	Night	6% 3 1 3 4 2 5% 3 5% 8% 60%	1978
September	1st to 10th	Night	10% 4 2 4 4 2 4 3 4 7% 56%	1800
	11th to 20th	Night	10% 5% 1 4 3 2 3 4 5% 8% 55%	1870
	21st to end	Night	7% 4 2 4 4 3 4 4 4 6% 58%	2024
October	1st to 10th	Night	10% 5% 2 4 3 2 3 4 4 6% 56%	2160
	11th to 20th	Night	15% 4 2 4 4 2 3 3 4 5% 54%	2160
	21st to end	Night	16% 7% 2 4 3 2 3 3 3 4 51%	2376
November	1st to 10th	Night	11% 4 2 3 3 2 3 3 3 6% 59%	2220
	11th to 20th	Night	12% 5% 2 4 4 2 3 3 4 6% 53%	2587
	21st to end	Night	17% 8% 2 4 4 2 4 3 4 5% 48%	2660
December	1st to 10th	Night	13% 8% 4 5% 4 3 4 5% 4 6% 44%	2660
	11th to 20th	Night	14% 7% 4 6% 5% 2 4 4 4 6% 43%	3279
	21st to end	Night	21% 16% 5% 9% 5% 3 3 3 3 4 28%	4884

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	50% 5% 12% 23% 10% 1	2766
	11th to 20th	Day	54% 4 12% 20% 9%	2850
	21st to end	Day	58% 4 11% 15% 10% 1	3135
February	1st to 10th	Day	50% 5% 12% 20% 10% 1	1710
	11th to 20th	Day	46% 6% 13% 22% 11% 3	1619
	21st to end	Day	46% 4 12% 21% 14% 2	1505
March	1st to 10th	Day	45% 6% 11% 24% 12% 3	1980
	11th to 20th	Day	53% 5% 9% 21% 10% 2	1980
	21st to end	Day	58% 6% 12% 17% 6% 1	2178
April	1st to 10th	Day	41% 6% 13% 25% 14% 1	2132
	11th to 20th	Day	45% 6% 12% 23% 13% 1	2134
	21st to end	Day	49% 7% 12% 22% 10%	2212
May	1st to 10th	Day	49% 7% 12% 21% 11% 1	2340
	11th to 20th	Day	44% 7% 14% 23% 12%	2310
	21st to end	Day	45% 9% 13% 21% 10% 2	2725
June	1st to 10th	Day	29% 9% 17% 31% 13% 1	2520
	11th to 20th	Day	32% 9% 14% 27% 16% 2	2520
	21st to end	Day	29% 8% 16% 29% 13% 4	2520
July	1st to 10th	Day	32% 9% 16% 25% 15% 4	2431
	11th to 20th	Day	26% 9% 16% 28% 17% 3	2271
	21st to end	Day	31% 7% 15% 31% 15%	2405
August	1st to 10th	Day	32% 9% 19% 25% 13% 1	2314
	11th to 20th	Day	33% 7% 14% 30% 16% 1	2301
	21st to end	Day	27% 7% 14% 25% 21% 6%	2376
September	1st to 10th	Day	31% 6% 13% 27% 17% 6%	2160
	11th to 20th	Day	29% 6% 13% 25% 24% 3	2087
	21st to end	Day	29% 6% 10% 30% 22% 3	1918
October	1st to 10th	Day	33% 5% 11% 27% 21% 3	1800
	11th to 20th	Day	35% 4 8% 28% 22% 4	1800
	21st to end	Day	42% 5% 9% 21% 18% 4	1980
November	1st to 10th	Day	33% 4 14% 26% 19% 4	1858
	11th to 20th	Day	37% 3 11% 26% 20% 3	1587
	21st to end	Day	44% 3 9% 27% 16% 1	1520
December	1st to 10th	Day	43% 4 13% 25% 13% 1	1520
	11th to 20th	Day	46% 5% 15% 26% 8% 1	1915
	21st to end	Day	63% 5% 9% 15% 7% 1	2783
January	1st to 10th	Night	51% 5% 12% 22% 11% 1	4172
	11th to 20th	Night	52% 5% 13% 19% 11% 1	4120
	21st to end	Night	56% 5% 12% 18% 9% 1	4532
February	1st to 10th	Night	48% 6% 11% 20% 13% 2	2470
	11th to 20th	Night	44% 5% 11% 21% 16% 3	2333
	21st to end	Night	42% 5% 11% 20% 17% 4	1763
March	1st to 10th	Night	38% 5% 10% 25% 18% 3	1980
	11th to 20th	Night	46% 6% 9% 22% 14% 3	1980
	21st to end	Night	54% 5% 13% 18% 9% 1	2178
April	1st to 10th	Night	34% 6% 11% 25% 20% 4	1828
	11th to 20th	Night	38% 5% 10% 27% 16% 4	1775
	21st to end	Night	43% 5% 10% 23% 17% 1	1745
May	1st to 10th	Night	40% 7% 15% 22% 13% 2	1620
	11th to 20th	Night	37% 8% 14% 23% 17% 1	1588
	21st to end	Night	38% 8% 13% 25% 13% 2	1552
June	1st to 10th	Night	24% 8% 16% 31% 18% 3	1440
	11th to 20th	Night	27% 8% 13% 27% 20% 5%	1440
	21st to end	Night	21% 6% 16% 33% 19% 5%	1440
July	1st to 10th	Night	27% 7% 13% 31% 17% 4	1417
	11th to 20th	Night	20% 6% 16% 32% 22% 3	1566
	21st to end	Night	26% 7% 13% 37% 16% 1	1673
August	1st to 10th	Night	24% 8% 20% 28% 17% 2	1601
	11th to 20th	Night	26% 6% 10% 33% 24% 1	1600
	21st to end	Night	23% 7% 12% 26% 26% 6%	1978
September	1st to 10th	Night	29% 6% 11% 24% 24% 7%	1800
	11th to 20th	Night	27% 5% 12% 27% 24% 5%	1870
	21st to end	Night	27% 6% 9% 27% 27% 4	2024
October	1st to 10th	Night	29% 6% 10% 25% 25% 6%	2160
	11th to 20th	Night	34% 4 7% 28% 21% 8%	2160
	21st to end	Night	38% 4 10% 22% 23% 4	2376
November	1st to 10th	Night	28% 5% 13% 26% 22% 6%	2220
	11th to 20th	Night	33% 4 9% 26% 24% 4	2587
	21st to end	Night	41% 4 10% 26% 17% 3	2660
December	1st to 10th	Night	41% 5% 14% 26% 14% 1	2660
	11th to 20th	Night	42% 4 13% 28% 12% 1	3281
	21st to end	Night	61% 4 9% 16% 8% 2	4884

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	19% 16% 33% 24% 8%	270
	11th to 20th	Day	30% 13% 36% 18% 3	270
	21st to end	Day	15% 15% 42% 22% 5%	297
February	1st to 10th	Day	25% 13% 40% 18% 3	270
	11th to 20th	Day	19% 17% 38% 18% 7%	252
	21st to end	Day	17% 21% 40% 18% 5%	198
March	1st to 10th	Day	16% 18% 45% 19% 3	240
	11th to 20th	Day	31% 9% 30% 24% 5%	240
	21st to end	Day	35% 21% 28% 12% 3	264
April	1st to 10th	Day	18% 18% 32% 24% 7% 1	392
	11th to 20th	Day	20% 14% 34% 24% 7% 1	412
	21st to end	Day	22% 13% 32% 22% 10% 1	472
May	1st to 10th	Day	18% 12% 36% 24% 9% 1	603
	11th to 20th	Day	20% 9% 28% 27% 13% 3	625
	21st to end	Day	14% 8% 26% 28% 19% 6%	679
June	1st to 10th	Day	7% 3 18% 33% 28% 11%	630
	11th to 20th	Day	9% 3 23% 35% 25% 5%	630
	21st to end	Day	5% 5% 31% 37% 18% 3	630
July	1st to 10th	Day	10% 4 12% 27% 31% 16%	621
	11th to 20th	Day	5% 2 19% 33% 32% 10%	618
	21st to end	Day	7% 3 14% 32% 35% 8%	684
August	1st to 10th	Day	6% 2 15% 37% 32% 7%	626
	11th to 20th	Day	8% 3 15% 35% 31% 9%	615
	21st to end	Day	8% 2 13% 29% 35% 14%	495
September	1st to 10th	Day	12% 2 15% 33% 30% 8%	450
	11th to 20th	Day	8% 2 16% 33% 33% 9%	377
	21st to end	Day	10% 7% 23% 29% 26% 5%	270
October	1st to 10th	Day	14% 7% 29% 27% 15% 8%	270
	11th to 20th	Day	10% 17% 39% 25% 9% 1	270
	21st to end	Day	25% 17% 31% 20% 7%	297
November	1st to 10th	Day	18% 6% 36% 25% 10% 4	270
	11th to 20th	Day	16% 17% 31% 24% 10% 3	270
	21st to end	Day	23% 14% 28% 27% 7%	270
December	1st to 10th	Day	11% 18% 36% 24% 8% 3	270
	11th to 20th	Day	20% 14% 34% 21% 9% 1	270
	21st to end	Day	19% 21% 40% 19% 1	297
January	1st to 10th	Night	14% 11% 39% 28% 7%	950
	11th to 20th	Night	18% 12% 39% 25% 6% 1	950
	21st to end	Night	16% 11% 39% 29% 4	1045
February	1st to 10th	Night	17% 10% 44% 25% 4	950
	11th to 20th	Night	16% 12% 37% 30% 4	902
	21st to end	Night	19% 14% 43% 20% 4 1	579
March	1st to 10th	Night	16% 12% 41% 27% 4	540
	11th to 20th	Night	19% 10% 34% 30% 6% 1	540
	21st to end	Night	27% 11% 36% 21% 5%	594
April	1st to 10th	Night	14% 13% 38% 30% 4	540
	11th to 20th	Night	18% 12% 34% 29% 8%	533
	21st to end	Night	19% 8% 37% 28% 7%	540
May	1st to 10th	Night	17% 7% 31% 36% 7% 1	540
	11th to 20th	Night	15% 7% 27% 37% 14% 1	531
	21st to end	Night	13% 6% 28% 31% 20% 2	584
June	1st to 10th	Night	7% 2 19% 45% 23% 4	540
	11th to 20th	Night	6% 2 23% 47% 20% 2	540
	21st to end	Night	5% 2 25% 49% 19% 1	540
July	1st to 10th	Night	9% 3 8% 42% 34% 4	525
	11th to 20th	Night	5% 2 14% 43% 34% 2	522
	21st to end	Night	7% 2 11% 44% 35% 1	591
August	1st to 10th	Night	4 2 13% 46% 33% 2	537
	11th to 20th	Night	7% 1 11% 45% 32% 3	534
	21st to end	Night	5% 2 12% 41% 37% 3	594
September	1st to 10th	Night	11% 2 15% 40% 28% 4	540
	11th to 20th	Night	12% 1 17% 36% 29% 4	540
	21st to end	Night	8% 5% 22% 41% 21% 3	584
October	1st to 10th	Night	12% 4 29% 34% 18% 2	720
	11th to 20th	Night	16% 9% 36% 30% 8%	720
	21st to end	Night	20% 10% 34% 27% 9% 1	792
November	1st to 10th	Night	13% 9% 34% 35% 10%	740
	11th to 20th	Night	14% 11% 36% 29% 9%	881
	21st to end	Night	20% 11% 35% 29% 5%	950
December	1st to 10th	Night	17% 9% 40% 28% 6% 1	950
	11th to 20th	Night	19% 9% 35% 32% 5%	950
	21st to end	Night	22% 14% 36% 25% 3	1045

Page generated at 2024-02-12 05:35:36. Version ac07

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