Harrisonburg
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Harrisonburg clear sky chart from 2005-11-06 to 2024-11-10.

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% 5% 5% 5% 4 6% 8% 40%	101070
	Night	13% 7% 2 6% 4 4 4 4 6% 7% 42%	98016
Transparency	Day	39% 8% 12% 22% 15% 4	104720
	Night	38% 8% 12% 23% 16% 3	102505
Seeing	Day	18% 14% 26% 24% 14% 5%	15001
	Night	16% 11% 25% 32% 14% 2	24746

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% 3 8% 4 4 3 3 4 6% 42%	2836
	11th to 20th	Day	12% 10% 3 9% 6% 4 4 4 4 5% 39%	2840
	21st to end	Day	16% 9% 3 7% 4 4 4 4 5% 5% 40%	3124
February	1st to 10th	Day	12% 9% 3 8% 5% 4 4 3 6% 6% 40%	1710
	11th to 20th	Day	15% 8% 3 6% 4 4 5% 4 5% 6% 41%	1663
	21st to end	Day	16% 8% 2 6% 4 4 5% 3 5% 6% 40%	1626
March	1st to 10th	Day	18% 9% 3 7% 4 4 5% 3 5% 6% 36%	3435
	11th to 20th	Day	9% 6% 2 6% 3 3 4 3 5% 7% 51%	3480
	21st to end	Day	16% 9% 3 7% 5% 5% 4 4 4 6% 38%	3815
April	1st to 10th	Day	10% 7% 2 7% 5% 5% 4 4 5% 7% 45%	2228
	11th to 20th	Day	13% 6% 2 5% 5% 4 4 3 5% 6% 46%	2254
	21st to end	Day	16% 7% 2 7% 5% 4 5% 3 5% 6% 41%	2350
May	1st to 10th	Day	17% 7% 3 8% 6% 5% 6% 4 6% 8% 29%	4082
	11th to 20th	Day	20% 7% 2 7% 5% 4 5% 4 5% 8% 32%	4081
	21st to end	Day	9% 5% 2 7% 5% 5% 5% 5% 7% 10% 40%	4686
June	1st to 10th	Day	11% 5% 2 6% 4 5% 5% 5% 6% 9% 42%	2660
	11th to 20th	Day	9% 5% 3 8% 5% 5% 6% 5% 7% 10% 37%	2660
	21st to end	Day	8% 5% 2 5% 5% 4 5% 5% 8% 12% 41%	2660
July	1st to 10th	Day	6% 4 2 6% 5% 5% 6% 5% 8% 10% 41%	4217
	11th to 20th	Day	9% 5% 2 7% 5% 6% 6% 6% 8% 12% 34%	4120
	21st to end	Day	12% 8% 3 9% 6% 6% 6% 5% 7% 9% 30%	4466
August	1st to 10th	Day	13% 6% 3 7% 6% 6% 6% 6% 8% 10% 30%	4104
	11th to 20th	Day	8% 5% 2 7% 6% 6% 6% 5% 8% 9% 38%	4014
	21st to end	Day	8% 4 2 5% 4 5% 5% 5% 7% 10% 45%	4180
September	1st to 10th	Day	13% 6% 2 5% 4 5% 5% 4 5% 6% 46%	2280
	11th to 20th	Day	12% 5% 2 6% 4 5% 5% 3 6% 7% 45%	2173
	21st to end	Day	21% 6% 2 6% 5% 4 5% 3 5% 6% 36%	2041
October	1st to 10th	Day	15% 6% 2 5% 5% 4 3 2 5% 7% 46%	1900
	11th to 20th	Day	13% 6% 2 5% 4 3 3 3 5% 7% 49%	1900
	21st to end	Day	13% 5% 2 5% 3 3 4 4 5% 6% 50%	2090
November	1st to 10th	Day	11% 6% 1 4 3 3 3 3 5% 6% 54%	1947
	11th to 20th	Day	13% 6% 2 4 4 3 4 3 5% 7% 49%	1663
	21st to end	Day	14% 4 2 5% 3 4 4 4 4 6% 49%	1520
December	1st to 10th	Day	16% 7% 2 6% 4 5% 5% 4 6% 7% 38%	1520
	11th to 20th	Day	14% 6% 2 5% 3 3 3 2 4 7% 51%	1910
	21st to end	Day	19% 6% 3 6% 5% 5% 5% 5% 7% 8% 32%	2835
January	1st to 10th	Night	11% 8% 3 6% 4 4 5% 4 5% 6% 44%	4109
	11th to 20th	Night	15% 9% 2 4 4 3 3 2 5% 5% 47%	4120
	21st to end	Night	19% 9% 3 6% 3 3 3 3 4 5% 41%	4532
February	1st to 10th	Night	12% 9% 2 6% 4 4 5% 4 5% 6% 43%	2470
	11th to 20th	Night	18% 7% 2 6% 4 3 4 4 5% 6% 40%	2403
	21st to end	Night	14% 8% 3 6% 5% 3 4 4 6% 7% 41%	1823
March	1st to 10th	Night	19% 9% 3 7% 5% 4 4 3 5% 6% 35%	3418
	11th to 20th	Night	10% 5% 2 7% 4 4 3 3 5% 6% 50%	3480
	21st to end	Night	14% 7% 3 6% 4 3 3 2 4 6% 47%	3817
April	1st to 10th	Night	14% 7% 3 5% 5% 4 4 3 6% 6% 43%	1950
	11th to 20th	Night	11% 6% 2 5% 4 3 4 4 6% 8% 46%	1875
	21st to end	Night	16% 5% 2 5% 3 4 4 4 6% 7% 44%	1845
May	1st to 10th	Night	19% 8% 3 8% 5% 5% 5% 4 6% 7% 32%	2813
	11th to 20th	Night	21% 7% 3 7% 4 4 5% 4 4 6% 35%	2812
	21st to end	Night	10% 6% 2 5% 5% 4 5% 4 7% 10% 42%	2867
June	1st to 10th	Night	8% 6% 2 6% 5% 3 5% 4 6% 11% 44%	1520
	11th to 20th	Night	9% 6% 2 7% 3 4 6% 4 7% 9% 43%	1520
	21st to end	Night	8% 4 2 6% 4 4 5% 6% 7% 9% 44%	1520
July	1st to 10th	Night	6% 4 2 6% 5% 6% 6% 5% 8% 10% 42%	2737
	11th to 20th	Night	7% 7% 3 7% 5% 5% 5% 5% 8% 10% 36%	2840
	21st to end	Night	10% 8% 4 9% 6% 6% 6% 5% 7% 8% 32%	3087
August	1st to 10th	Night	14% 7% 2 7% 6% 6% 5% 5% 7% 10% 32%	2825
	11th to 20th	Night	9% 7% 3 9% 5% 6% 6% 5% 7% 7% 35%	2785
	21st to end	Night	9% 5% 2 5% 4 5% 5% 4 6% 10% 45%	3472
September	1st to 10th	Night	12% 6% 2 5% 4 4 4 4 5% 8% 46%	1900
	11th to 20th	Night	11% 6% 2 7% 4 4 5% 4 6% 6% 45%	2003
	21st to end	Night	19% 8% 3 5% 4 4 3 3 4 5% 41%	2137
October	1st to 10th	Night	16% 6% 2 6% 3 4 4 3 5% 7% 44%	2280
	11th to 20th	Night	12% 6% 2 5% 4 4 4 3 5% 6% 49%	2280
	21st to end	Night	13% 5% 2 5% 4 3 4 3 5% 5% 51%	2508
November	1st to 10th	Night	11% 6% 2 5% 3 3 4 3 5% 5% 52%	2336
	11th to 20th	Night	12% 7% 2 5% 4 3 4 3 5% 6% 49%	2510
	21st to end	Night	13% 6% 2 5% 4 4 4 3 4 6% 48%	2660
December	1st to 10th	Night	15% 7% 2 7% 5% 4 5% 4 4 5% 42%	2660
	11th to 20th	Night	14% 7% 3 6% 4 4 4 3 4 6% 45%	3285
	21st to end	Night	15% 6% 2 6% 5% 5% 6% 5% 7% 6% 37%	4817

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	42% 5% 8% 24% 17% 4	2837
	11th to 20th	Day	46% 6% 8% 18% 17% 6%	2840
	21st to end	Day	46% 5% 9% 21% 16% 2	3124
February	1st to 10th	Day	43% 6% 11% 21% 15% 3	1710
	11th to 20th	Day	43% 6% 10% 21% 17% 4	1672
	21st to end	Day	44% 7% 11% 16% 16% 5%	1626
March	1st to 10th	Day	48% 7% 9% 19% 13% 5%	3435
	11th to 20th	Day	32% 6% 9% 27% 21% 6%	3480
	21st to end	Day	47% 8% 10% 18% 15% 3	3815
April	1st to 10th	Day	38% 7% 11% 19% 17% 7%	2228
	11th to 20th	Day	37% 7% 10% 20% 20% 5%	2254
	21st to end	Day	43% 7% 11% 22% 13% 4	2350
May	1st to 10th	Day	49% 11% 11% 18% 10% 1	4120
	11th to 20th	Day	48% 10% 12% 20% 9% 1	4085
	21st to end	Day	33% 12% 16% 20% 15% 3	4700
June	1st to 10th	Day	37% 10% 15% 23% 14% 1	2660
	11th to 20th	Day	40% 11% 15% 21% 12% 2	2660
	21st to end	Day	33% 12% 17% 24% 13% 1	2660
July	1st to 10th	Day	34% 13% 18% 20% 9% 5%	4152
	11th to 20th	Day	37% 12% 18% 25% 7% 1	4051
	21st to end	Day	48% 9% 11% 22% 10% 1	4324
August	1st to 10th	Day	44% 11% 18% 20% 6%	4091
	11th to 20th	Day	37% 11% 13% 26% 13% 1	4053
	21st to end	Day	33% 10% 17% 27% 12% 1	4180
September	1st to 10th	Day	38% 9% 13% 16% 19% 4	2280
	11th to 20th	Day	38% 7% 9% 24% 18% 3	2173
	21st to end	Day	47% 7% 10% 18% 15% 3	2041
October	1st to 10th	Day	33% 5% 9% 20% 28% 5%	3160
	11th to 20th	Day	25% 5% 9% 29% 20% 13%	3140
	21st to end	Day	22% 4 10% 31% 23% 11%	3428
November	1st to 10th	Day	31% 5% 9% 26% 24% 4	1947
	11th to 20th	Day	35% 5% 12% 20% 22% 7%	1663
	21st to end	Day	35% 5% 10% 25% 22% 3	1520
December	1st to 10th	Day	44% 7% 11% 22% 13% 3	1520
	11th to 20th	Day	34% 4 11% 30% 16% 6%	1906
	21st to end	Day	44% 8% 14% 22% 11% 1	2835
January	1st to 10th	Night	36% 5% 11% 24% 19% 4	4109
	11th to 20th	Night	39% 4 10% 24% 18% 5%	4120
	21st to end	Night	45% 5% 8% 23% 17% 2	4532
February	1st to 10th	Night	41% 7% 12% 23% 15% 2	2470
	11th to 20th	Night	44% 6% 9% 20% 16% 6%	2405
	21st to end	Night	42% 7% 13% 19% 14% 5%	1823
March	1st to 10th	Night	47% 7% 9% 22% 13% 3	3418
	11th to 20th	Night	30% 6% 10% 25% 25% 3	3480
	21st to end	Night	38% 6% 11% 23% 19% 4	3817
April	1st to 10th	Night	40% 7% 11% 20% 18% 4	1950
	11th to 20th	Night	34% 8% 14% 20% 19% 4	1875
	21st to end	Night	38% 7% 13% 25% 14% 3	1845
May	1st to 10th	Night	48% 10% 12% 20% 8% 2	2840
	11th to 20th	Night	47% 9% 11% 24% 8% 1	2813
	21st to end	Night	33% 11% 18% 25% 10% 3	2874
June	1st to 10th	Night	34% 9% 17% 27% 13% 1	1520
	11th to 20th	Night	34% 12% 17% 24% 12% 1	1520
	21st to end	Night	32% 12% 17% 20% 18% 2	1520
July	1st to 10th	Night	33% 13% 23% 16% 13% 2	2692
	11th to 20th	Night	38% 12% 20% 22% 8% 1	2786
	21st to end	Night	44% 12% 17% 18% 9%	2988
August	1st to 10th	Night	43% 11% 18% 22% 6%	2814
	11th to 20th	Night	42% 10% 14% 23% 11%	2812
	21st to end	Night	32% 9% 17% 29% 11% 1	3472
September	1st to 10th	Night	35% 10% 15% 20% 17% 4	1900
	11th to 20th	Night	37% 7% 10% 26% 18% 3	2003
	21st to end	Night	46% 7% 9% 20% 16% 2	2137
October	1st to 10th	Night	40% 6% 10% 20% 20% 4	3800
	11th to 20th	Night	25% 6% 11% 20% 30% 8%	3779
	21st to end	Night	22% 4 11% 30% 26% 7%	4120
November	1st to 10th	Night	33% 6% 10% 22% 23% 6%	2336
	11th to 20th	Night	35% 6% 9% 22% 23% 6%	2510
	21st to end	Night	36% 5% 10% 24% 20% 4	2660
December	1st to 10th	Night	43% 7% 10% 23% 13% 3	2660
	11th to 20th	Night	39% 5% 9% 22% 19% 5%	3288
	21st to end	Night	41% 8% 14% 22% 14% 2	4817

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	29% 27% 28% 13% 3	270
	11th to 20th	Day	27% 31% 26% 14% 2	270
	21st to end	Day	24% 32% 30% 11% 2 1	297
February	1st to 10th	Day	25% 30% 31% 12% 2	270
	11th to 20th	Day	37% 28% 29% 6%	270
	21st to end	Day	32% 22% 28% 16% 2	348
March	1st to 10th	Day	22% 27% 27% 19% 5%	460
	11th to 20th	Day	23% 25% 28% 17% 5% 2	460
	21st to end	Day	23% 21% 30% 19% 6% 1	506
April	1st to 10th	Day	23% 23% 27% 18% 7% 1	460
	11th to 20th	Day	21% 16% 29% 19% 12% 4	452
	21st to end	Day	23% 18% 28% 20% 8% 3	460
May	1st to 10th	Day	21% 21% 25% 18% 10% 4	463
	11th to 20th	Day	19% 14% 28% 22% 12% 4	487
	21st to end	Day	16% 8% 25% 26% 16% 8%	529
June	1st to 10th	Day	13% 9% 28% 27% 17% 5%	490
	11th to 20th	Day	12% 9% 26% 28% 18% 7%	490
	21st to end	Day	8% 6% 30% 33% 18% 5%	490
July	1st to 10th	Day	10% 4 20% 29% 26% 9%	485
	11th to 20th	Day	5% 3 18% 37% 27% 10%	484
	21st to end	Day	12% 4 20% 31% 24% 10%	532
August	1st to 10th	Day	13% 6% 22% 26% 21% 13%	486
	11th to 20th	Day	12% 5% 18% 29% 24% 11%	479
	21st to end	Day	9% 4 17% 32% 22% 16%	539
September	1st to 10th	Day	13% 7% 19% 26% 21% 15%	490
	11th to 20th	Day	13% 3 21% 29% 23% 10%	490
	21st to end	Day	27% 11% 20% 21% 17% 4	490
October	1st to 10th	Day	19% 7% 21% 30% 17% 6%	490
	11th to 20th	Day	14% 16% 25% 24% 17% 3	490
	21st to end	Day	18% 12% 33% 23% 10% 3	539
November	1st to 10th	Day	17% 12% 29% 28% 12% 2	491
	11th to 20th	Day	21% 15% 29% 24% 9% 1	288
	21st to end	Day	19% 18% 34% 21% 6% 1	180
December	1st to 10th	Day	22% 21% 38% 16% 3 1	180
	11th to 20th	Day	24% 19% 31% 19% 7% 1	180
	21st to end	Day	19% 26% 32% 17% 6%	216
January	1st to 10th	Night	19% 19% 34% 24% 4	760
	11th to 20th	Night	22% 16% 29% 30% 3	760
	21st to end	Night	17% 16% 39% 25% 3	836
February	1st to 10th	Night	17% 16% 34% 30% 2	760
	11th to 20th	Night	24% 22% 34% 20% 1	743
	21st to end	Night	21% 19% 36% 22% 2	628
March	1st to 10th	Night	19% 17% 34% 26% 4	760
	11th to 20th	Night	23% 18% 31% 22% 6% 1	760
	21st to end	Night	20% 17% 32% 26% 5% 1	836
April	1st to 10th	Night	17% 21% 32% 25% 5%	760
	11th to 20th	Night	15% 16% 30% 28% 11% 1	751
	21st to end	Night	20% 11% 27% 35% 7% 1	705
May	1st to 10th	Night	19% 8% 24% 32% 17% 1	570
	11th to 20th	Night	19% 4 23% 37% 15% 2	561
	21st to end	Night	14% 3 18% 38% 25% 2	495
June	1st to 10th	Night	10% 3 21% 42% 23% 2	380
	11th to 20th	Night	9% 5% 14% 45% 26% 2	380
	21st to end	Night	7% 3 17% 51% 21% 1	380
July	1st to 10th	Night	11% 3 11% 38% 32% 5%	491
	11th to 20th	Night	7% 2 10% 34% 42% 5%	552
	21st to end	Night	7% 2 12% 39% 35% 5%	624
August	1st to 10th	Night	10% 2 11% 40% 33% 4	567
	11th to 20th	Night	13% 3 12% 36% 34% 3	564
	21st to end	Night	11% 3 13% 36% 32% 4	832
September	1st to 10th	Night	14% 2 14% 34% 30% 5%	760
	11th to 20th	Night	12% 4 15% 35% 29% 5%	760
	21st to end	Night	24% 5% 19% 31% 20% 1	760
October	1st to 10th	Night	18% 7% 18% 31% 23% 4	760
	11th to 20th	Night	14% 10% 27% 33% 16% 1	760
	21st to end	Night	15% 10% 30% 32% 12% 1	836
November	1st to 10th	Night	15% 9% 26% 36% 12% 2	779
	11th to 20th	Night	16% 14% 28% 33% 9% 1	760
	21st to end	Night	16% 14% 30% 31% 8% 1	760
December	1st to 10th	Night	20% 13% 32% 29% 6%	760
	11th to 20th	Night	16% 12% 33% 34% 5%	760
	21st to end	Night	17% 14% 29% 36% 4	836

Page generated at 2024-11-07 06:55:42. Version ac07

Copyright © 2024 Attilla Danko.