Dulaney Springs Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dulaney Springs Park clear sky chart from 2005-11-06 to 2024-11-02.

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	15% 6% 2 6% 4 4 5% 4 6% 8% 40%	101238
	Night	16% 7% 2 6% 4 4 4 3 5% 7% 42%	97692
Transparency	Day	41% 6% 12% 24% 15% 3	101036
	Night	41% 5% 11% 24% 16% 3	97565
Seeing	Day	21% 14% 29% 23% 11% 3	14969
	Night	19% 12% 28% 27% 11% 1	24374

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	16% 6% 2 5% 3 3 4 4 5% 5% 47%	2517
	11th to 20th	Day	14% 10% 4 8% 6% 5% 4 3 5% 5% 37%	2789
	21st to end	Day	20% 8% 2 7% 5% 4 4 3 5% 6% 36%	3124
February	1st to 10th	Day	14% 8% 3 6% 5% 4 5% 4 7% 6% 39%	1710
	11th to 20th	Day	17% 7% 2 5% 4 4 4 3 6% 7% 40%	1740
	21st to end	Day	19% 10% 2 6% 4 4 4 3 4 5% 39%	1570
March	1st to 10th	Day	23% 5% 2 6% 3 3 4 4 5% 7% 38%	3300
	11th to 20th	Day	10% 6% 2 6% 4 4 5% 4 6% 7% 47%	3480
	21st to end	Day	20% 8% 2 6% 4 3 3 2 5% 5% 41%	3932
April	1st to 10th	Day	15% 7% 2 5% 5% 6% 5% 4 6% 7% 39%	2280
	11th to 20th	Day	14% 6% 2 6% 5% 3 4 3 6% 6% 45%	2254
	21st to end	Day	19% 5% 2 5% 4 4 4 3 6% 8% 40%	2280
May	1st to 10th	Day	28% 7% 2 6% 4 4 4 4 5% 7% 30%	3974
	11th to 20th	Day	23% 7% 3 7% 5% 4 4 4 6% 7% 29%	4398
	21st to end	Day	12% 4 2 5% 4 5% 5% 4 6% 9% 44%	4823
June	1st to 10th	Day	13% 6% 2 5% 5% 4 5% 5% 7% 10% 39%	2660
	11th to 20th	Day	12% 5% 2 5% 5% 5% 5% 4 6% 9% 40%	2660
	21st to end	Day	10% 4 2 5% 4 5% 5% 5% 7% 10% 44%	2660
July	1st to 10th	Day	6% 5% 2 5% 5% 5% 7% 6% 8% 11% 41%	4440
	11th to 20th	Day	9% 5% 2 6% 5% 5% 5% 6% 8% 11% 38%	4440
	21st to end	Day	11% 7% 3 7% 6% 5% 6% 5% 7% 9% 34%	4477
August	1st to 10th	Day	18% 5% 2 6% 5% 5% 6% 5% 7% 8% 32%	4104
	11th to 20th	Day	11% 5% 2 6% 5% 5% 6% 5% 6% 9% 39%	3831
	21st to end	Day	11% 5% 2 5% 4 5% 5% 4 6% 9% 46%	4180
September	1st to 10th	Day	15% 5% 2 6% 4 3 4 3 5% 7% 45%	2280
	11th to 20th	Day	12% 5% 2 5% 4 4 4 3 5% 9% 47%	2280
	21st to end	Day	21% 7% 2 6% 4 4 4 4 5% 7% 35%	2019
October	1st to 10th	Day	18% 5% 2 5% 3 3 4 3 5% 6% 45%	1900
	11th to 20th	Day	17% 4 2 4 4 3 4 3 4 6% 48%	1900
	21st to end	Day	15% 6% 2 6% 4 3 4 3 4 5% 48%	2090
November	1st to 10th	Day	13% 6% 1 5% 4 3 3 3 5% 7% 51%	1714
	11th to 20th	Day	15% 6% 2 4 3 4 4 4 5% 5% 49%	1710
	21st to end	Day	16% 6% 2 5% 4 5% 3 3 4 6% 46%	1520
December	1st to 10th	Day	18% 7% 2 6% 4 3 5% 4 5% 7% 40%	1520
	11th to 20th	Day	18% 6% 2 5% 4 4 4 3 5% 7% 42%	1910
	21st to end	Day	17% 7% 2 7% 4 5% 5% 4 5% 7% 38%	2772
January	1st to 10th	Night	16% 7% 2 6% 3 4 4 3 5% 7% 42%	4429
	11th to 20th	Night	19% 8% 2 5% 3 3 3 3 4 5% 45%	4156
	21st to end	Night	22% 8% 2 6% 3 3 4 3 5% 5% 39%	4532
February	1st to 10th	Night	16% 8% 2 6% 4 4 4 3 5% 7% 40%	2470
	11th to 20th	Night	17% 8% 2 6% 4 3 4 3 4 6% 42%	2324
	21st to end	Night	16% 8% 3 6% 5% 4 4 3 4 5% 42%	1884
March	1st to 10th	Night	22% 8% 2 5% 4 4 4 3 4 6% 39%	3552
	11th to 20th	Night	11% 5% 2 5% 4 4 4 4 5% 6% 50%	3480
	21st to end	Night	15% 8% 2 6% 4 3 3 2 3 5% 47%	3700
April	1st to 10th	Night	16% 7% 2 6% 4 4 5% 4 5% 7% 40%	1900
	11th to 20th	Night	14% 7% 2 6% 4 3 4 3 5% 7% 45%	1875
	21st to end	Night	19% 6% 2 4 3 3 4 3 5% 7% 44%	1900
May	1st to 10th	Night	25% 8% 3 5% 4 4 3 3 6% 7% 32%	2950
	11th to 20th	Night	24% 11% 3 7% 4 4 4 3 5% 6% 29%	2495
	21st to end	Night	13% 5% 1 5% 4 4 4 4 7% 9% 43%	2732
June	1st to 10th	Night	11% 6% 2 5% 5% 4 4 4 6% 9% 45%	1520
	11th to 20th	Night	11% 6% 2 6% 5% 4 4 5% 7% 8% 41%	1520
	21st to end	Night	10% 5% 2 5% 4 5% 4 5% 8% 10% 43%	1520
July	1st to 10th	Night	6% 5% 3 8% 5% 5% 6% 6% 8% 10% 38%	2520
	11th to 20th	Night	9% 6% 2 6% 6% 5% 5% 5% 7% 10% 39%	2520
	21st to end	Night	12% 7% 3 7% 5% 5% 5% 4 5% 8% 39%	3073
August	1st to 10th	Night	19% 5% 2 6% 4 4 5% 5% 7% 10% 33%	2825
	11th to 20th	Night	12% 8% 3 7% 5% 5% 5% 4 6% 7% 37%	2965
	21st to end	Night	13% 5% 2 5% 3 4 4 3 6% 8% 48%	3476
September	1st to 10th	Night	14% 6% 2 6% 4 3 3 3 5% 7% 47%	1900
	11th to 20th	Night	11% 7% 2 5% 3 4 3 3 4 7% 52%	1900
	21st to end	Night	20% 7% 2 6% 4 4 4 2 5% 6% 40%	2157
October	1st to 10th	Night	20% 6% 2 6% 4 3 3 3 4 5% 43%	2280
	11th to 20th	Night	15% 4 2 4 3 3 3 2 4 7% 52%	2280
	21st to end	Night	17% 5% 2 4 3 3 4 3 4 6% 49%	2508
November	1st to 10th	Night	12% 5% 2 5% 4 4 3 2 4 5% 53%	2395
	11th to 20th	Night	14% 8% 2 6% 3 3 3 3 4 6% 49%	2470
	21st to end	Night	14% 5% 2 5% 4 4 4 4 5% 7% 48%	2655
December	1st to 10th	Night	18% 7% 3 6% 4 4 4 3 5% 6% 40%	2660
	11th to 20th	Night	18% 5% 2 5% 4 4 4 3 4 6% 43%	3285
	21st to end	Night	16% 7% 3 6% 4 5% 5% 5% 7% 8% 35%	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	38% 4 9% 31% 14% 4	2518
	11th to 20th	Day	50% 3 9% 21% 14% 4	2789
	21st to end	Day	50% 3 12% 22% 10% 2	3124
February	1st to 10th	Day	44% 4 13% 26% 12% 2	1710
	11th to 20th	Day	43% 3 9% 27% 14% 3	1749
	21st to end	Day	47% 3 10% 22% 13% 4	1570
March	1st to 10th	Day	45% 4 10% 25% 13% 3	3300
	11th to 20th	Day	34% 5% 9% 27% 20% 5%	3480
	21st to end	Day	47% 3 9% 20% 18% 4	3932
April	1st to 10th	Day	42% 5% 12% 20% 17% 4	2280
	11th to 20th	Day	39% 5% 11% 22% 18% 6%	2254
	21st to end	Day	42% 4 10% 21% 19% 3	2280
May	1st to 10th	Day	53% 6% 10% 19% 11% 2	4010
	11th to 20th	Day	51% 7% 15% 18% 8% 2	4402
	21st to end	Day	34% 7% 13% 26% 17% 2	4837
June	1st to 10th	Day	38% 7% 14% 24% 15% 2	2660
	11th to 20th	Day	39% 7% 13% 24% 14% 3	2660
	21st to end	Day	33% 7% 15% 25% 18% 2	2660
July	1st to 10th	Day	34% 11% 17% 21% 13% 5%	4370
	11th to 20th	Day	36% 8% 17% 27% 10% 1	4365
	21st to end	Day	43% 8% 12% 19% 17% 1	4334
August	1st to 10th	Day	47% 8% 12% 24% 8%	4091
	11th to 20th	Day	38% 7% 11% 29% 14% 1	3870
	21st to end	Day	34% 6% 12% 28% 17% 2	4180
September	1st to 10th	Day	39% 5% 12% 19% 21% 4	2280
	11th to 20th	Day	35% 5% 9% 27% 21% 4	2280
	21st to end	Day	48% 4 7% 20% 19% 2	2019
October	1st to 10th	Day	40% 4 11% 23% 20% 3	1900
	11th to 20th	Day	37% 4 11% 23% 21% 4	1900
	21st to end	Day	39% 3 8% 27% 20% 2	2090
November	1st to 10th	Day	33% 4 12% 26% 21% 4	1714
	11th to 20th	Day	36% 3 10% 24% 23% 3	1710
	21st to end	Day	40% 3 11% 31% 14% 3	1520
December	1st to 10th	Day	44% 3 15% 25% 11% 2	1520
	11th to 20th	Day	42% 3 11% 31% 11% 2	1906
	21st to end	Day	46% 5% 15% 21% 12% 1	2772
January	1st to 10th	Night	41% 4 11% 27% 14% 3	4429
	11th to 20th	Night	42% 3 10% 26% 16% 2	4156
	21st to end	Night	47% 3 8% 28% 13% 2	4532
February	1st to 10th	Night	45% 4 12% 24% 14% 1	2470
	11th to 20th	Night	44% 3 9% 21% 18% 4	2326
	21st to end	Night	45% 2 11% 21% 16% 5%	1884
March	1st to 10th	Night	46% 3 11% 26% 12% 2	3552
	11th to 20th	Night	34% 4 9% 33% 17% 3	3480
	21st to end	Night	41% 3 8% 20% 22% 5%	3700
April	1st to 10th	Night	43% 4 10% 20% 19% 4	1900
	11th to 20th	Night	39% 4 11% 21% 20% 6%	1875
	21st to end	Night	39% 5% 10% 22% 18% 5%	1900
May	1st to 10th	Night	52% 5% 10% 19% 12% 2	2980
	11th to 20th	Night	56% 6% 12% 14% 10% 2	2496
	21st to end	Night	35% 8% 16% 24% 14% 3	2739
June	1st to 10th	Night	36% 6% 12% 25% 18% 2	1520
	11th to 20th	Night	38% 7% 14% 24% 16% 2	1520
	21st to end	Night	34% 7% 13% 27% 17% 3	1520
July	1st to 10th	Night	39% 9% 20% 16% 12% 4	2480
	11th to 20th	Night	38% 9% 17% 25% 11% 2	2472
	21st to end	Night	42% 7% 13% 21% 16% 1	2975
August	1st to 10th	Night	44% 8% 18% 21% 8% 1	2814
	11th to 20th	Night	44% 6% 10% 26% 13% 1	2992
	21st to end	Night	35% 5% 11% 31% 17% 2	3476
September	1st to 10th	Night	37% 5% 11% 22% 20% 5%	1900
	11th to 20th	Night	34% 3 9% 26% 24% 4	1900
	21st to end	Night	46% 4 8% 19% 19% 3	2157
October	1st to 10th	Night	44% 4 11% 21% 18% 3	2280
	11th to 20th	Night	34% 4 10% 29% 20% 4	2280
	21st to end	Night	36% 3 9% 27% 21% 3	2508
November	1st to 10th	Night	33% 5% 8% 27% 21% 6%	2395
	11th to 20th	Night	38% 3 9% 24% 20% 5%	2470
	21st to end	Night	37% 4 11% 26% 20% 2	2655
December	1st to 10th	Night	45% 3 12% 24% 15% 1	2660
	11th to 20th	Night	42% 3 11% 22% 18% 4	3288
	21st to end	Night	44% 6% 15% 23% 11% 1	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	30% 23% 31% 11% 4 1	180
	11th to 20th	Day	33% 25% 29% 12% 1	258
	21st to end	Day	26% 27% 31% 12% 3	297
February	1st to 10th	Day	28% 24% 34% 11% 2	270
	11th to 20th	Day	35% 22% 37% 5% 1	347
	21st to end	Day	30% 23% 30% 14% 3	382
March	1st to 10th	Day	26% 24% 30% 17% 3	460
	11th to 20th	Day	29% 22% 31% 12% 4 1	460
	21st to end	Day	26% 20% 33% 15% 5% 1	506
April	1st to 10th	Day	23% 23% 35% 14% 4 2	460
	11th to 20th	Day	23% 19% 32% 16% 8% 3	452
	21st to end	Day	28% 16% 35% 14% 6% 2	460
May	1st to 10th	Day	31% 15% 30% 15% 7% 2	463
	11th to 20th	Day	24% 12% 32% 20% 9% 2	487
	21st to end	Day	19% 6% 28% 28% 16% 3	529
June	1st to 10th	Day	16% 12% 29% 25% 13% 4	490
	11th to 20th	Day	17% 7% 28% 31% 14% 3	490
	21st to end	Day	12% 11% 31% 29% 14% 3	490
July	1st to 10th	Day	13% 4 22% 33% 21% 8%	485
	11th to 20th	Day	6% 4 23% 38% 22% 7%	484
	21st to end	Day	13% 5% 29% 30% 19% 4	532
August	1st to 10th	Day	11% 6% 23% 34% 19% 7%	486
	11th to 20th	Day	12% 3 22% 35% 18% 9%	479
	21st to end	Day	10% 5% 27% 31% 18% 9%	539
September	1st to 10th	Day	16% 9% 19% 29% 17% 10%	490
	11th to 20th	Day	13% 6% 21% 34% 17% 8%	490
	21st to end	Day	29% 10% 21% 25% 12% 3	490
October	1st to 10th	Day	26% 8% 26% 22% 14% 5%	490
	11th to 20th	Day	18% 16% 28% 22% 14% 2	490
	21st to end	Day	18% 16% 35% 21% 8% 2	539
November	1st to 10th	Day	17% 13% 35% 22% 11% 3	386
	11th to 20th	Day	20% 19% 31% 19% 9% 1	370
	21st to end	Day	26% 17% 31% 21% 6%	180
December	1st to 10th	Day	25% 21% 36% 14% 3 1	180
	11th to 20th	Day	30% 21% 30% 16% 3	180
	21st to end	Day	28% 18% 31% 18% 6%	198
January	1st to 10th	Night	22% 18% 36% 21% 3	760
	11th to 20th	Night	25% 17% 32% 22% 4	760
	21st to end	Night	22% 19% 37% 21% 2	836
February	1st to 10th	Night	22% 16% 34% 24% 3	760
	11th to 20th	Night	28% 21% 34% 16% 1	743
	21st to end	Night	25% 19% 35% 18% 3	628
March	1st to 10th	Night	22% 19% 34% 22% 3	760
	11th to 20th	Night	23% 20% 31% 19% 6% 1	760
	21st to end	Night	21% 17% 38% 19% 4	836
April	1st to 10th	Night	22% 21% 34% 19% 4	760
	11th to 20th	Night	17% 17% 34% 24% 7%	751
	21st to end	Night	22% 15% 31% 24% 7%	760
May	1st to 10th	Night	23% 11% 28% 29% 8% 1	658
	11th to 20th	Night	22% 11% 27% 30% 9% 1	374
	21st to end	Night	17% 7% 21% 36% 17% 2	411
June	1st to 10th	Night	13% 4 26% 38% 19% 1	380
	11th to 20th	Night	12% 6% 23% 41% 18% 1	380
	21st to end	Night	11% 3 27% 43% 16%	380
July	1st to 10th	Night	10% 5% 16% 41% 25% 3	370
	11th to 20th	Night	8% 4 16% 40% 29% 2	368
	21st to end	Night	10% 3 18% 42% 24% 3	610
August	1st to 10th	Night	13% 2 14% 41% 26% 3	567
	11th to 20th	Night	15% 4 15% 37% 26% 3	666
	21st to end	Night	14% 4 17% 34% 26% 4	836
September	1st to 10th	Night	16% 4 21% 32% 23% 3	760
	11th to 20th	Night	13% 5% 17% 34% 27% 4	760
	21st to end	Night	24% 5% 22% 30% 18% 1	760
October	1st to 10th	Night	24% 8% 20% 27% 18% 4	760
	11th to 20th	Night	19% 11% 25% 31% 13% 1	760
	21st to end	Night	20% 14% 28% 26% 11% 1	836
November	1st to 10th	Night	15% 11% 32% 29% 10% 2	748
	11th to 20th	Night	20% 17% 28% 27% 7% 1	760
	21st to end	Night	17% 17% 32% 27% 6% 1	760
December	1st to 10th	Night	24% 16% 33% 19% 7% 1	760
	11th to 20th	Night	18% 15% 39% 21% 6%	760
	21st to end	Night	22% 15% 34% 26% 3	836

Page generated at 2024-10-30 13:19:24. Version ac07

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