Fort Hunt Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fort Hunt Park clear sky chart from 2005-11-06 to 2026-02-16.

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	13% 6% 2 6% 4 4 4 4 6% 8% 42%	130912
	Night	14% 7% 2 6% 4 4 4 4 5% 7% 43%	129919
Transparency	Day	39% 6% 11% 24% 17% 4	134505
	Night	39% 5% 10% 23% 18% 4	134397
Seeing	Day	18% 12% 27% 25% 13% 4	16601
	Night	17% 10% 30% 29% 12% 1	26238

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% 4 2 6% 5% 4 4 3 5% 6% 47%	4818
	11th to 20th	Day	15% 8% 2 5% 3 3 3 2 4 4 51%	5280
	21st to end	Day	13% 6% 2 7% 4 4 4 3 5% 7% 43%	5780
February	1st to 10th	Day	14% 7% 2 6% 5% 4 5% 4 5% 6% 42%	1890
	11th to 20th	Day	19% 7% 2 5% 4 4 3 2 6% 7% 41%	1868
	21st to end	Day	18% 8% 3 6% 5% 4 3 3 4 6% 41%	1650
March	1st to 10th	Day	18% 6% 2 5% 4 5% 4 3 5% 7% 42%	4838
	11th to 20th	Day	11% 6% 2 5% 4 4 4 3 4 7% 51%	4980
	21st to end	Day	16% 6% 2 6% 5% 4 4 3 5% 6% 41%	5573
April	1st to 10th	Day	13% 7% 2 6% 5% 4 4 3 5% 6% 44%	2400
	11th to 20th	Day	12% 6% 2 6% 5% 4 4 4 4 6% 48%	2374
	21st to end	Day	16% 6% 2 6% 4 3 5% 4 6% 6% 42%	2400
May	1st to 10th	Day	19% 8% 2 7% 4 4 5% 4 7% 9% 31%	5716
	11th to 20th	Day	20% 7% 2 6% 4 4 5% 4 6% 10% 31%	6152
	21st to end	Day	15% 5% 2 6% 4 4 5% 4 6% 8% 39%	6934
June	1st to 10th	Day	10% 5% 2 6% 5% 4 5% 4 6% 10% 43%	2800
	11th to 20th	Day	11% 5% 2 6% 4 4 5% 5% 7% 9% 43%	2800
	21st to end	Day	8% 4 2 5% 4 5% 5% 6% 7% 10% 44%	2800
July	1st to 10th	Day	7% 4 2 6% 4 5% 5% 5% 7% 12% 43%	6360
	11th to 20th	Day	9% 6% 3 7% 5% 5% 6% 6% 10% 13% 30%	6142
	21st to end	Day	8% 6% 2 6% 5% 5% 5% 5% 8% 11% 39%	6424
August	1st to 10th	Day	15% 7% 2 7% 4 5% 6% 5% 8% 10% 33%	4234
	11th to 20th	Day	10% 5% 2 7% 5% 5% 7% 5% 8% 10% 38%	3963
	21st to end	Day	9% 4 2 5% 4 4 5% 4 6% 9% 48%	4312
September	1st to 10th	Day	13% 5% 2 5% 4 5% 4 3 5% 7% 46%	2400
	11th to 20th	Day	11% 6% 2 5% 3 4 4 4 6% 9% 47%	2400
	21st to end	Day	19% 8% 3 7% 4 4 4 4 6% 6% 36%	2108
October	1st to 10th	Day	15% 5% 2 5% 4 3 3 4 6% 5% 48%	2000
	11th to 20th	Day	16% 5% 2 5% 3 3 3 3 4 7% 51%	2000
	21st to end	Day	13% 5% 2 6% 3 3 4 2 5% 6% 49%	2200
November	1st to 10th	Day	11% 5% 2 3 4 4 4 3 5% 8% 52%	1947
	11th to 20th	Day	13% 6% 1 4 3 3 4 3 5% 7% 50%	1890
	21st to end	Day	15% 6% 2 5% 4 3 3 4 4 5% 49%	1681
December	1st to 10th	Day	11% 5% 2 7% 4 4 4 4 5% 7% 48%	2680
	11th to 20th	Day	17% 8% 2 5% 3 2 3 3 4 7% 45%	3070
	21st to end	Day	15% 8% 3 6% 4 4 4 4 6% 7% 39%	4048
January	1st to 10th	Night	12% 7% 2 6% 4 4 5% 4 5% 6% 45%	8071
	11th to 20th	Night	13% 7% 2 5% 3 3 3 2 4 5% 52%	7680
	21st to end	Night	13% 7% 3 5% 3 4 4 3 4 6% 48%	8401
February	1st to 10th	Night	15% 7% 2 6% 4 3 4 3 6% 6% 42%	2730
	11th to 20th	Night	20% 7% 3 5% 3 3 3 2 4 6% 43%	2527
	21st to end	Night	16% 8% 2 5% 3 3 3 4 4 7% 43%	1980
March	1st to 10th	Night	16% 5% 2 6% 4 3 3 3 4 5% 47%	5012
	11th to 20th	Night	11% 5% 2 5% 3 3 4 4 6% 7% 50%	4980
	21st to end	Night	13% 7% 2 6% 4 4 4 3 5% 6% 44%	5358
April	1st to 10th	Night	16% 7% 2 6% 5% 4 5% 4 5% 7% 41%	2000
	11th to 20th	Night	13% 6% 2 6% 4 3 4 3 5% 8% 47%	1975
	21st to end	Night	16% 6% 1 4 3 4 4 5% 5% 7% 43%	2000
May	1st to 10th	Night	18% 9% 3 8% 5% 5% 5% 4 6% 8% 30%	4220
	11th to 20th	Night	21% 8% 2 6% 4 4 4 4 6% 8% 32%	3727
	21st to end	Night	17% 7% 2 6% 4 5% 5% 4 7% 8% 35%	3920
June	1st to 10th	Night	10% 5% 2 5% 5% 5% 5% 5% 8% 8% 43%	1600
	11th to 20th	Night	12% 6% 2 6% 5% 5% 5% 4 7% 10% 40%	1600
	21st to end	Night	9% 4 2 6% 5% 5% 5% 5% 8% 9% 43%	1600
July	1st to 10th	Night	8% 6% 2 8% 5% 5% 6% 4 7% 9% 40%	3598
	11th to 20th	Night	9% 8% 3 9% 6% 5% 6% 5% 8% 10% 30%	3797
	21st to end	Night	8% 6% 2 6% 5% 5% 6% 5% 8% 9% 39%	4427
August	1st to 10th	Night	16% 6% 2 8% 5% 5% 5% 4 6% 10% 33%	2915
	11th to 20th	Night	11% 7% 2 9% 5% 5% 6% 5% 7% 8% 34%	3039
	21st to end	Night	10% 5% 2 5% 3 4 4 4 5% 8% 50%	3586
September	1st to 10th	Night	12% 6% 2 6% 4 5% 4 4 6% 7% 45%	2000
	11th to 20th	Night	9% 7% 2 5% 3 4 4 3 6% 8% 48%	2000
	21st to end	Night	18% 8% 3 6% 5% 3 4 4 5% 6% 36%	2288
October	1st to 10th	Night	17% 7% 2 5% 3 3 3 3 4 6% 47%	2400
	11th to 20th	Night	15% 5% 2 5% 3 3 3 3 4 6% 52%	2400
	21st to end	Night	14% 5% 1 5% 3 3 4 3 5% 7% 50%	2640
November	1st to 10th	Night	12% 5% 2 5% 3 3 4 3 5% 6% 53%	2568
	11th to 20th	Night	15% 7% 2 4 4 3 3 3 5% 7% 49%	2730
	21st to end	Night	12% 5% 1 5% 4 4 4 4 6% 7% 49%	2935
December	1st to 10th	Night	10% 6% 2 5% 4 3 3 3 5% 6% 53%	4720
	11th to 20th	Night	20% 6% 2 6% 3 4 4 3 5% 7% 40%	5345
	21st to end	Night	16% 7% 2 6% 4 4 4 4 6% 7% 39%	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	39% 4 7% 26% 19% 5%	4819
	11th to 20th	Day	38% 3 5% 22% 23% 9%	5280
	21st to end	Day	41% 4 8% 32% 13% 3	5780
February	1st to 10th	Day	43% 5% 12% 25% 14% 2	1890
	11th to 20th	Day	43% 4 8% 24% 18% 3	1877
	21st to end	Day	45% 5% 11% 20% 16% 4	1650
March	1st to 10th	Day	41% 5% 8% 22% 16% 8%	4838
	11th to 20th	Day	33% 5% 8% 26% 21% 6%	4980
	21st to end	Day	43% 5% 10% 19% 17% 7%	5573
April	1st to 10th	Day	40% 5% 10% 20% 19% 6%	2400
	11th to 20th	Day	37% 6% 9% 22% 20% 7%	2374
	21st to end	Day	40% 6% 10% 22% 17% 4	2400
May	1st to 10th	Day	48% 7% 14% 19% 11% 1	5749
	11th to 20th	Day	47% 8% 11% 24% 9% 1	6156
	21st to end	Day	41% 8% 12% 22% 16% 2	6949
June	1st to 10th	Day	35% 7% 14% 26% 16% 2	2800
	11th to 20th	Day	35% 10% 13% 24% 16% 2	2800
	21st to end	Day	32% 9% 15% 24% 18% 2	2800
July	1st to 10th	Day	33% 9% 20% 20% 14% 4	6290
	11th to 20th	Day	43% 10% 17% 21% 7% 1	6067
	21st to end	Day	37% 7% 11% 22% 22% 1	6240
August	1st to 10th	Day	44% 7% 16% 25% 8%	4221
	11th to 20th	Day	39% 8% 13% 26% 14% 1	4002
	21st to end	Day	32% 6% 14% 28% 18% 2	4312
September	1st to 10th	Day	36% 7% 13% 19% 21% 4	2400
	11th to 20th	Day	34% 6% 11% 26% 20% 4	2400
	21st to end	Day	47% 6% 10% 18% 17% 2	2108
October	1st to 10th	Day	37% 4 7% 17% 29% 5%	3260
	11th to 20th	Day	25% 3 6% 29% 26% 10%	3240
	21st to end	Day	23% 2 8% 30% 27% 10%	3538
November	1st to 10th	Day	32% 4 11% 27% 21% 5%	1947
	11th to 20th	Day	34% 4 11% 25% 22% 5%	1890
	21st to end	Day	38% 4 9% 27% 18% 3	1681
December	1st to 10th	Day	36% 4 12% 27% 17% 4	2680
	11th to 20th	Day	41% 4 13% 29% 11% 3	3066
	21st to end	Day	43% 6% 12% 23% 16% 1	4048
January	1st to 10th	Night	39% 4 9% 25% 20% 4	8072
	11th to 20th	Night	36% 3 6% 23% 24% 8%	7680
	21st to end	Night	38% 3 6% 30% 19% 3	8401
February	1st to 10th	Night	42% 5% 11% 24% 17% 2	2730
	11th to 20th	Night	43% 3 8% 22% 18% 5%	2529
	21st to end	Night	41% 4 10% 22% 17% 6%	1980
March	1st to 10th	Night	39% 4 7% 24% 17% 9%	5012
	11th to 20th	Night	32% 5% 10% 25% 21% 7%	4980
	21st to end	Night	40% 5% 8% 22% 20% 6%	5358
April	1st to 10th	Night	42% 5% 9% 19% 21% 4	2000
	11th to 20th	Night	37% 6% 11% 21% 20% 6%	1975
	21st to end	Night	39% 6% 10% 24% 16% 5%	2000
May	1st to 10th	Night	52% 7% 12% 17% 9% 3	4250
	11th to 20th	Night	48% 8% 11% 21% 11% 1	3728
	21st to end	Night	43% 8% 13% 22% 11% 2	3927
June	1st to 10th	Night	35% 9% 11% 26% 17% 2	1600
	11th to 20th	Night	37% 9% 13% 25% 13% 2	1600
	21st to end	Night	34% 7% 15% 21% 19% 3	1600
July	1st to 10th	Night	39% 10% 17% 19% 14% 2	3560
	11th to 20th	Night	46% 11% 19% 17% 7% 1	3752
	21st to end	Night	37% 9% 14% 22% 18%	4297
August	1st to 10th	Night	45% 9% 16% 21% 8% 1	2904
	11th to 20th	Night	44% 7% 12% 24% 12% 1	3066
	21st to end	Night	32% 5% 11% 30% 20% 2	3586
September	1st to 10th	Night	38% 7% 10% 22% 18% 6%	2000
	11th to 20th	Night	33% 6% 9% 27% 21% 3	2000
	21st to end	Night	47% 6% 10% 18% 16% 3	2288
October	1st to 10th	Night	40% 4 9% 21% 19% 7%	3920
	11th to 20th	Night	24% 3 10% 22% 32% 8%	3899
	21st to end	Night	23% 4 9% 31% 26% 8%	4252
November	1st to 10th	Night	33% 5% 9% 26% 22% 6%	2568
	11th to 20th	Night	37% 4 9% 22% 22% 7%	2730
	21st to end	Night	34% 5% 10% 26% 22% 3	2935
December	1st to 10th	Night	33% 4 12% 27% 21% 3	4720
	11th to 20th	Night	45% 4 11% 20% 16% 5%	5348
	21st to end	Night	43% 6% 14% 22% 15% 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	31% 18% 31% 15% 5%	248
	11th to 20th	Day	30% 24% 30% 13% 2	330
	21st to end	Day	21% 26% 35% 13% 4	363
February	1st to 10th	Day	25% 24% 35% 13% 4	330
	11th to 20th	Day	35% 21% 33% 10% 1	385
	21st to end	Day	28% 21% 31% 18% 2	414
March	1st to 10th	Day	23% 23% 31% 20% 3	500
	11th to 20th	Day	27% 19% 32% 16% 5% 1	500
	21st to end	Day	23% 17% 34% 21% 4 1	550
April	1st to 10th	Day	22% 23% 31% 18% 5% 1	500
	11th to 20th	Day	17% 19% 32% 20% 9% 3	492
	21st to end	Day	24% 12% 32% 23% 7% 1	500
May	1st to 10th	Day	25% 15% 28% 20% 10% 2	503
	11th to 20th	Day	22% 12% 30% 23% 11% 2	527
	21st to end	Day	18% 9% 24% 25% 19% 5%	573
June	1st to 10th	Day	12% 9% 29% 25% 19% 6%	530
	11th to 20th	Day	14% 8% 25% 33% 16% 4	530
	21st to end	Day	10% 5% 27% 35% 19% 5%	530
July	1st to 10th	Day	11% 3 17% 36% 22% 11%	525
	11th to 20th	Day	5% 2 16% 41% 26% 10%	524
	21st to end	Day	9% 3 19% 39% 23% 7%	576
August	1st to 10th	Day	11% 5% 22% 31% 23% 8%	526
	11th to 20th	Day	12% 4 18% 33% 24% 9%	519
	21st to end	Day	9% 4 21% 31% 23% 12%	583
September	1st to 10th	Day	15% 6% 23% 25% 18% 12%	530
	11th to 20th	Day	14% 4 20% 35% 18% 10%	530
	21st to end	Day	25% 12% 23% 24% 12% 4	530
October	1st to 10th	Day	20% 6% 23% 25% 18% 8%	530
	11th to 20th	Day	17% 14% 27% 25% 13% 3	530
	21st to end	Day	17% 13% 33% 26% 8% 3	583
November	1st to 10th	Day	16% 13% 31% 27% 9% 3	477
	11th to 20th	Day	19% 15% 34% 23% 8% 1	430
	21st to end	Day	24% 21% 28% 19% 8% 1	221
December	1st to 10th	Day	20% 19% 40% 15% 5% 1	220
	11th to 20th	Day	24% 19% 30% 20% 6%	220
	21st to end	Day	27% 17% 31% 20% 5%	242
January	1st to 10th	Night	20% 19% 39% 19% 3	840
	11th to 20th	Night	22% 15% 35% 23% 5%	840
	21st to end	Night	19% 17% 38% 24% 2	924
February	1st to 10th	Night	20% 15% 35% 26% 3	840
	11th to 20th	Night	25% 19% 38% 16% 1	804
	21st to end	Night	25% 17% 35% 21% 2	660
March	1st to 10th	Night	20% 15% 39% 23% 3	800
	11th to 20th	Night	22% 15% 38% 20% 6% 1	800
	21st to end	Night	19% 14% 41% 22% 3	880
April	1st to 10th	Night	20% 18% 39% 21% 4	800
	11th to 20th	Night	16% 14% 34% 28% 6%	791
	21st to end	Night	21% 9% 34% 28% 8%	800
May	1st to 10th	Night	19% 10% 31% 30% 10%	686
	11th to 20th	Night	18% 7% 30% 35% 10%	468
	21st to end	Night	15% 4 26% 36% 18% 1	433
June	1st to 10th	Night	10% 4 27% 38% 20% 2	400
	11th to 20th	Night	14% 5% 21% 42% 18% 1	400
	21st to end	Night	10% 3 24% 44% 18% 1	400
July	1st to 10th	Night	9% 2 22% 38% 28% 2	390
	11th to 20th	Night	7% 2 13% 44% 31% 4	471
	21st to end	Night	8% 2 19% 39% 29% 3	657
August	1st to 10th	Night	10% 2 13% 44% 28% 3	597
	11th to 20th	Night	13% 3 17% 39% 25% 2	693
	21st to end	Night	12% 2 17% 36% 28% 4	880
September	1st to 10th	Night	15% 3 19% 34% 26% 4	800
	11th to 20th	Night	13% 3 15% 38% 28% 4	800
	21st to end	Night	21% 7% 22% 33% 17% 1	800
October	1st to 10th	Night	19% 6% 20% 30% 20% 5%	800
	11th to 20th	Night	17% 10% 27% 29% 16% 1	800
	21st to end	Night	16% 10% 32% 28% 13% 1	880
November	1st to 10th	Night	14% 9% 34% 30% 12% 2	820
	11th to 20th	Night	19% 14% 30% 28% 8%	840
	21st to end	Night	17% 14% 32% 27% 9%	840
December	1st to 10th	Night	20% 14% 35% 24% 7% 1	840
	11th to 20th	Night	19% 12% 39% 26% 5%	840
	21st to end	Night	21% 12% 34% 29% 3	924

Page generated at 2026-02-13 01:42:12. Version ac07

Copyright © 2026 Attilla Danko.