Frostburg
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Frostburg clear sky chart from 2005-11-06 to 2024-11-05.

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	14% 7% 3 7% 5% 5% 5% 4 6% 8% 36%	101134
	Night	14% 7% 3 6% 5% 4 5% 4 6% 7% 39%	97826
Transparency	Day	45% 3 11% 25% 14% 2	104780
	Night	43% 3 12% 26% 14% 2	102319
Seeing	Day	26% 14% 26% 20% 10% 4	14845
	Night	24% 13% 23% 27% 12% 1	24469

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% 9% 3 8% 5% 5% 6% 4 5% 6% 34%	2754
	11th to 20th	Day	10% 13% 5% 13% 8% 6% 6% 4 6% 5% 24%	2840
	21st to end	Day	15% 13% 6% 10% 6% 6% 4 4 5% 6% 26%	3124
February	1st to 10th	Day	13% 13% 4 7% 6% 6% 5% 4 5% 7% 31%	1710
	11th to 20th	Day	12% 9% 3 10% 6% 6% 5% 4 7% 7% 31%	1663
	21st to end	Day	15% 10% 4 9% 6% 4 4 3 6% 6% 34%	1584
March	1st to 10th	Day	16% 12% 3 6% 5% 5% 5% 4 5% 7% 31%	3435
	11th to 20th	Day	9% 6% 3 7% 5% 4 4 4 7% 9% 43%	3480
	21st to end	Day	14% 9% 3 7% 5% 4 4 4 6% 6% 38%	3815
April	1st to 10th	Day	12% 9% 3 8% 5% 6% 5% 4 6% 6% 35%	2236
	11th to 20th	Day	13% 7% 3 7% 5% 5% 4 4 6% 7% 40%	2254
	21st to end	Day	19% 7% 2 8% 5% 4 4 3 6% 6% 35%	2394
May	1st to 10th	Day	23% 7% 3 8% 5% 5% 5% 4 6% 6% 29%	4082
	11th to 20th	Day	24% 8% 2 6% 4 4 4 4 6% 8% 31%	4081
	21st to end	Day	12% 5% 2 5% 5% 5% 5% 5% 8% 10% 38%	4822
June	1st to 10th	Day	12% 6% 2 5% 6% 5% 5% 5% 8% 9% 38%	2660
	11th to 20th	Day	12% 5% 2 6% 6% 6% 6% 5% 7% 10% 35%	2660
	21st to end	Day	10% 4 2 5% 5% 5% 6% 5% 7% 10% 41%	2660
July	1st to 10th	Day	7% 4 2 6% 5% 6% 6% 5% 8% 8% 44%	4390
	11th to 20th	Day	7% 5% 2 6% 5% 6% 6% 4 8% 10% 40%	4120
	21st to end	Day	11% 8% 3 8% 5% 5% 5% 5% 6% 7% 36%	4466
August	1st to 10th	Day	16% 5% 2 7% 5% 6% 6% 5% 7% 9% 30%	4104
	11th to 20th	Day	8% 4 2 7% 5% 6% 7% 5% 8% 9% 38%	4044
	21st to end	Day	10% 4 2 5% 4 6% 5% 4 7% 9% 44%	4190
September	1st to 10th	Day	16% 5% 2 6% 4 4 4 4 5% 6% 44%	2280
	11th to 20th	Day	14% 6% 1 6% 4 4 4 3 5% 8% 46%	2178
	21st to end	Day	21% 7% 2 6% 5% 5% 5% 3 5% 6% 36%	2040
October	1st to 10th	Day	15% 7% 2 5% 4 4 5% 4 5% 6% 44%	1900
	11th to 20th	Day	16% 7% 3 6% 4 4 4 4 5% 6% 41%	1900
	21st to end	Day	15% 6% 2 6% 4 4 5% 3 6% 6% 43%	2090
November	1st to 10th	Day	9% 6% 2 5% 4 4 3 4 6% 7% 49%	1898
	11th to 20th	Day	13% 9% 3 6% 5% 4 4 4 5% 8% 40%	1558
	21st to end	Day	14% 8% 2 7% 6% 5% 6% 3 6% 6% 37%	1520
December	1st to 10th	Day	15% 10% 4 9% 5% 6% 7% 5% 6% 6% 28%	1520
	11th to 20th	Day	14% 10% 3 8% 5% 4 4 5% 7% 6% 34%	1910
	21st to end	Day	17% 9% 4 9% 6% 6% 5% 4 5% 7% 26%	2772
January	1st to 10th	Night	10% 9% 5% 10% 6% 6% 6% 5% 6% 6% 31%	4173
	11th to 20th	Night	12% 12% 5% 8% 5% 5% 4 4 6% 7% 33%	4120
	21st to end	Night	18% 10% 4 8% 5% 5% 5% 4 6% 6% 30%	4532
February	1st to 10th	Night	11% 8% 3 7% 5% 5% 5% 4 6% 7% 38%	2470
	11th to 20th	Night	12% 10% 2 8% 6% 5% 6% 4 5% 6% 34%	2403
	21st to end	Night	14% 9% 3 7% 4 6% 5% 3 8% 7% 34%	1864
March	1st to 10th	Night	21% 10% 3 5% 4 3 4 3 5% 6% 35%	3418
	11th to 20th	Night	9% 6% 5% 7% 5% 4 4 4 6% 8% 42%	3480
	21st to end	Night	12% 7% 2 5% 4 4 5% 3 5% 6% 46%	3817
April	1st to 10th	Night	14% 8% 3 8% 5% 5% 4 5% 6% 6% 37%	1943
	11th to 20th	Night	12% 6% 2 7% 5% 4 4 4 6% 9% 41%	1875
	21st to end	Night	17% 5% 2 5% 4 4 3 3 5% 8% 42%	1800
May	1st to 10th	Night	25% 7% 2 7% 5% 3 5% 4 6% 7% 28%	2813
	11th to 20th	Night	26% 8% 2 5% 3 4 3 3 4 5% 35%	2812
	21st to end	Night	11% 4 2 5% 4 5% 5% 5% 8% 11% 42%	2732
June	1st to 10th	Night	11% 4 1 4 4 4 5% 5% 7% 8% 47%	1520
	11th to 20th	Night	12% 5% 1 6% 4 5% 6% 4 6% 9% 42%	1520
	21st to end	Night	10% 5% 1 4 5% 4 4 5% 8% 12% 44%	1520
July	1st to 10th	Night	7% 4 2 5% 5% 5% 6% 5% 7% 11% 44%	2552
	11th to 20th	Night	6% 4 2 6% 5% 5% 5% 5% 7% 10% 44%	2840
	21st to end	Night	8% 6% 2 7% 5% 4 5% 6% 8% 8% 42%	3087
August	1st to 10th	Night	15% 4 2 5% 4 5% 4 5% 7% 10% 39%	2825
	11th to 20th	Night	9% 5% 2 7% 5% 4 5% 4 7% 8% 44%	2785
	21st to end	Night	13% 5% 2 4 4 4 4 3 5% 8% 47%	3433
September	1st to 10th	Night	14% 5% 2 5% 3 3 4 3 5% 6% 48%	1900
	11th to 20th	Night	14% 6% 1 4 3 3 3 3 5% 6% 53%	2000
	21st to end	Night	22% 5% 2 5% 4 3 4 3 6% 7% 40%	2139
October	1st to 10th	Night	17% 6% 2 5% 4 3 3 3 5% 6% 45%	2280
	11th to 20th	Night	15% 5% 2 4 3 3 5% 3 5% 8% 47%	2280
	21st to end	Night	16% 5% 1 5% 4 4 4 4 5% 7% 45%	2508
November	1st to 10th	Night	10% 7% 2 5% 4 4 4 3 5% 6% 50%	2280
	11th to 20th	Night	14% 7% 3 6% 4 4 4 4 6% 7% 41%	2616
	21st to end	Night	14% 8% 2 7% 5% 5% 5% 4 6% 7% 38%	2660
December	1st to 10th	Night	15% 10% 3 7% 6% 5% 5% 4 5% 7% 32%	2660
	11th to 20th	Night	14% 7% 3 7% 4 5% 5% 5% 6% 7% 36%	3285
	21st to end	Night	16% 9% 5% 8% 6% 6% 6% 4 7% 7% 26%	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	51% 2 9% 27% 9% 2	2755
	11th to 20th	Day	62% 1 8% 15% 12% 1	2840
	21st to end	Day	61% 2 7% 21% 8% 1	3124
February	1st to 10th	Day	54% 2 12% 20% 11% 1	1710
	11th to 20th	Day	52% 3 11% 21% 12% 1	1672
	21st to end	Day	52% 2 12% 19% 13% 2	1584
March	1st to 10th	Day	54% 2 9% 24% 10% 2	3435
	11th to 20th	Day	39% 1 9% 32% 16% 2	3480
	21st to end	Day	47% 2 12% 23% 13% 2	3815
April	1st to 10th	Day	49% 3 11% 19% 15% 3	2236
	11th to 20th	Day	44% 2 11% 20% 18% 4	2254
	21st to end	Day	49% 3 8% 26% 12% 2	2394
May	1st to 10th	Day	56% 2 9% 22% 10% 1	4120
	11th to 20th	Day	53% 3 10% 26% 7% 1	4085
	21st to end	Day	40% 4 14% 27% 13% 3	4836
June	1st to 10th	Day	41% 5% 13% 26% 14% 1	2660
	11th to 20th	Day	43% 5% 14% 25% 13% 1	2660
	21st to end	Day	38% 5% 16% 27% 13% 1	2660
July	1st to 10th	Day	36% 5% 15% 29% 11% 4	4321
	11th to 20th	Day	38% 3 15% 29% 13% 1	4051
	21st to end	Day	46% 3 9% 25% 16% 1	4324
August	1st to 10th	Day	48% 4 15% 24% 8%	4091
	11th to 20th	Day	40% 3 11% 31% 14%	4083
	21st to end	Day	37% 4 14% 30% 14% 2	4190
September	1st to 10th	Day	41% 4 10% 20% 21% 4	2280
	11th to 20th	Day	38% 2 10% 29% 19% 2	2178
	21st to end	Day	50% 3 9% 21% 16% 1	2040
October	1st to 10th	Day	34% 2 9% 27% 24% 5%	3160
	11th to 20th	Day	37% 1 10% 26% 16% 9%	3140
	21st to end	Day	28% 1 11% 33% 24% 2	3428
November	1st to 10th	Day	35% 2 12% 25% 21% 5%	1898
	11th to 20th	Day	43% 2 10% 22% 20% 3	1558
	21st to end	Day	48% 2 12% 25% 12% 1	1520
December	1st to 10th	Day	56% 3 12% 19% 8% 1	1520
	11th to 20th	Day	50% 1 11% 27% 9% 1	1906
	21st to end	Day	58% 1 13% 16% 11%	2772
January	1st to 10th	Night	53% 2 8% 23% 14% 1	4173
	11th to 20th	Night	52% 2 12% 20% 13% 2	4120
	21st to end	Night	56% 2 9% 23% 10% 1	4532
February	1st to 10th	Night	45% 3 14% 25% 12% 1	2470
	11th to 20th	Night	51% 3 10% 21% 15% 1	2405
	21st to end	Night	49% 3 12% 22% 11% 4	1864
March	1st to 10th	Night	51% 2 9% 28% 9% 1	3418
	11th to 20th	Night	42% 2 9% 34% 12% 1	3480
	21st to end	Night	40% 3 10% 28% 17% 3	3817
April	1st to 10th	Night	47% 2 11% 20% 17% 3	1943
	11th to 20th	Night	41% 4 12% 24% 16% 4	1875
	21st to end	Night	42% 3 10% 28% 13% 3	1800
May	1st to 10th	Night	55% 3 10% 19% 10% 2	2840
	11th to 20th	Night	53% 2 10% 25% 9% 1	2813
	21st to end	Night	36% 4 17% 28% 10% 4	2739
June	1st to 10th	Night	35% 6% 13% 29% 16% 1	1520
	11th to 20th	Night	37% 5% 15% 29% 12% 1	1520
	21st to end	Night	33% 5% 17% 27% 16% 1	1520
July	1st to 10th	Night	35% 5% 17% 26% 12% 6%	2511
	11th to 20th	Night	35% 4 16% 30% 14% 1	2786
	21st to end	Night	38% 4 15% 24% 17% 1	2988
August	1st to 10th	Night	41% 5% 19% 26% 8%	2814
	11th to 20th	Night	37% 4 12% 29% 17% 1	2812
	21st to end	Night	37% 2 12% 33% 14% 2	3433
September	1st to 10th	Night	37% 3 15% 23% 19% 4	1900
	11th to 20th	Night	34% 2 10% 32% 20% 2	2000
	21st to end	Night	45% 3 10% 23% 18% 1	2139
October	1st to 10th	Night	36% 2 9% 30% 22% 2	3800
	11th to 20th	Night	28% 1 11% 27% 24% 9%	3779
	21st to end	Night	28% 1 10% 33% 23% 4	4120
November	1st to 10th	Night	37% 2 11% 25% 20% 5%	2280
	11th to 20th	Night	42% 3 8% 27% 16% 4	2616
	21st to end	Night	46% 2 12% 24% 14% 2	2660
December	1st to 10th	Night	52% 3 12% 23% 9% 1	2660
	11th to 20th	Night	46% 2 12% 24% 15% 1	3288
	21st to end	Night	57% 2 15% 17% 9%	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	43% 20% 24% 8% 4 1	249
	11th to 20th	Day	41% 23% 28% 6% 3	270
	21st to end	Day	36% 25% 24% 12% 3	297
February	1st to 10th	Day	39% 21% 29% 10% 2	270
	11th to 20th	Day	44% 22% 28% 4 1	270
	21st to end	Day	40% 18% 29% 12% 1	325
March	1st to 10th	Day	35% 18% 25% 18% 3	460
	11th to 20th	Day	36% 24% 23% 12% 4 1	460
	21st to end	Day	32% 21% 28% 13% 4 2	506
April	1st to 10th	Day	34% 21% 23% 15% 6%	460
	11th to 20th	Day	26% 19% 28% 16% 9% 3	452
	21st to end	Day	33% 16% 28% 15% 7% 1	460
May	1st to 10th	Day	32% 17% 26% 13% 7% 4	463
	11th to 20th	Day	30% 15% 27% 18% 8% 2	487
	21st to end	Day	22% 10% 26% 22% 12% 9%	529
June	1st to 10th	Day	19% 12% 29% 24% 12% 4	490
	11th to 20th	Day	18% 14% 28% 22% 13% 5%	490
	21st to end	Day	13% 16% 31% 22% 13% 5%	490
July	1st to 10th	Day	15% 5% 30% 25% 16% 9%	485
	11th to 20th	Day	7% 7% 32% 30% 17% 8%	484
	21st to end	Day	15% 8% 25% 30% 16% 7%	532
August	1st to 10th	Day	14% 9% 22% 28% 19% 9%	486
	11th to 20th	Day	14% 6% 27% 29% 14% 10%	479
	21st to end	Day	15% 5% 24% 26% 18% 12%	539
September	1st to 10th	Day	21% 7% 21% 23% 18% 10%	490
	11th to 20th	Day	19% 4 21% 28% 22% 6%	490
	21st to end	Day	31% 8% 24% 20% 14% 3	490
October	1st to 10th	Day	24% 9% 24% 23% 17% 4	490
	11th to 20th	Day	26% 14% 26% 22% 11% 1	490
	21st to end	Day	24% 16% 30% 21% 8% 1	539
November	1st to 10th	Day	21% 15% 29% 22% 10% 1	472
	11th to 20th	Day	29% 18% 29% 19% 5%	213
	21st to end	Day	32% 22% 32% 11% 3 1	180
December	1st to 10th	Day	38% 19% 27% 9% 5% 1	180
	11th to 20th	Day	41% 15% 27% 14% 3	180
	21st to end	Day	35% 14% 26% 20% 5% 1	198
January	1st to 10th	Night	32% 19% 29% 16% 4	760
	11th to 20th	Night	32% 18% 29% 19% 1	760
	21st to end	Night	30% 22% 28% 18% 2	836
February	1st to 10th	Night	29% 18% 24% 27% 3	760
	11th to 20th	Night	32% 24% 28% 15% 1	743
	21st to end	Night	32% 16% 30% 19% 3	628
March	1st to 10th	Night	28% 18% 28% 23% 4	760
	11th to 20th	Night	33% 18% 24% 18% 6% 1	760
	21st to end	Night	26% 18% 29% 21% 5% 1	836
April	1st to 10th	Night	27% 21% 28% 19% 5%	760
	11th to 20th	Night	21% 17% 25% 28% 8% 1	751
	21st to end	Night	26% 13% 24% 28% 9%	660
May	1st to 10th	Night	25% 10% 21% 29% 15%	570
	11th to 20th	Night	26% 9% 21% 29% 14% 1	561
	21st to end	Night	12% 8% 18% 31% 27% 3	411
June	1st to 10th	Night	12% 6% 24% 38% 20% 1	380
	11th to 20th	Night	16% 6% 21% 35% 21% 2	380
	21st to end	Night	12% 5% 26% 38% 19% 1	380
July	1st to 10th	Night	11% 3 18% 40% 24% 4	388
	11th to 20th	Night	7% 5% 16% 35% 33% 4	552
	21st to end	Night	10% 3 21% 38% 26% 2	624
August	1st to 10th	Night	11% 3 13% 39% 31% 3	567
	11th to 20th	Night	12% 4 12% 41% 26% 5%	564
	21st to end	Night	14% 3 13% 38% 27% 4	806
September	1st to 10th	Night	18% 4 16% 31% 25% 6%	760
	11th to 20th	Night	18% 5% 12% 33% 27% 4	760
	21st to end	Night	26% 8% 15% 28% 19% 3	760
October	1st to 10th	Night	22% 10% 19% 26% 21% 3	760
	11th to 20th	Night	23% 11% 25% 28% 12% 1	760
	21st to end	Night	25% 15% 23% 25% 11% 1	836
November	1st to 10th	Night	19% 13% 22% 32% 12% 1	760
	11th to 20th	Night	29% 15% 21% 27% 8% 1	760
	21st to end	Night	28% 14% 25% 26% 6% 1	760
December	1st to 10th	Night	32% 18% 24% 20% 6% 1	760
	11th to 20th	Night	30% 18% 24% 24% 4	760
	21st to end	Night	29% 16% 27% 25% 3	836

Page generated at 2024-11-03 02:11:28. Version ac07

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