Red Oak observing site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Red Oak observing site clear sky chart from 2005-11-06 to 2025-05-11.

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	12% 7% 2 6% 4 4 4 3 5% 7% 45%	113827
	Night	12% 7% 3 6% 4 3 3 3 5% 6% 49%	115306
Transparency	Day	37% 5% 11% 25% 18% 4	117479
	Night	35% 4 10% 25% 20% 5%	119796
Seeing	Day	15% 9% 27% 28% 17% 5%	16158
	Night	15% 9% 32% 31% 13% 1	26118

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	17% 10% 4 6% 4 4 4 2 3 5% 41%	4077
	11th to 20th	Day	8% 9% 4 7% 6% 4 4 3 4 5% 45%	4080
	21st to end	Day	17% 11% 3 6% 3 3 3 3 4 5% 43%	4488
February	1st to 10th	Day	16% 13% 3 7% 5% 3 4 4 4 4 38%	1800
	11th to 20th	Day	14% 10% 3 8% 4 4 3 3 5% 5% 42%	1754
	21st to end	Day	16% 9% 2 7% 4 3 3 3 6% 6% 41%	1759
March	1st to 10th	Day	13% 8% 2 5% 3 3 4 3 4 5% 49%	4936
	11th to 20th	Day	10% 7% 2 4 3 3 3 3 4 6% 55%	4980
	21st to end	Day	14% 10% 3 7% 5% 5% 5% 4 5% 7% 35%	5462
April	1st to 10th	Day	13% 8% 2 6% 4 5% 3 4 5% 7% 44%	2330
	11th to 20th	Day	16% 8% 2 6% 4 4 4 3 5% 6% 41%	2374
	21st to end	Day	21% 8% 3 6% 4 4 4 4 5% 6% 36%	2422
May	1st to 10th	Day	20% 8% 2 7% 4 3 4 4 6% 6% 35%	4212
	11th to 20th	Day	14% 6% 3 7% 4 5% 5% 4 5% 8% 40%	4083
	21st to end	Day	14% 6% 2 6% 6% 5% 5% 4 6% 8% 38%	4477
June	1st to 10th	Day	7% 5% 2 6% 4 4 6% 4 6% 9% 46%	2612
	11th to 20th	Day	8% 4 2 5% 4 4 6% 3 6% 9% 48%	2660
	21st to end	Day	6% 2 1 4 3 4 4 4 6% 10% 56%	2521
July	1st to 10th	Day	11% 5% 3 6% 4 5% 5% 4 7% 9% 42%	4120
	11th to 20th	Day	5% 4 1 5% 4 4 5% 5% 6% 9% 50%	4120
	21st to end	Day	7% 4 1 5% 4 5% 6% 5% 8% 11% 44%	4465
August	1st to 10th	Day	5% 3 1 4 3 3 4 3 6% 9% 57%	4104
	11th to 20th	Day	8% 5% 2 7% 4 5% 6% 4 7% 8% 44%	4012
	21st to end	Day	6% 3 2 4 3 4 4 4 5% 8% 57%	4180
September	1st to 10th	Day	12% 5% 2 5% 4 3 3 3 4 5% 54%	2280
	11th to 20th	Day	10% 7% 2 6% 4 5% 4 3 6% 7% 47%	2150
	21st to end	Day	8% 5% 2 5% 4 4 4 4 5% 7% 53%	2050
October	1st to 10th	Day	11% 4 2 4 3 4 3 3 5% 6% 55%	1900
	11th to 20th	Day	14% 5% 2 5% 2 2 3 2 4 6% 55%	1900
	21st to end	Day	18% 7% 2 4 3 3 3 2 4 5% 49%	2090
November	1st to 10th	Day	12% 5% 2 6% 2 2 3 2 4 6% 56%	1958
	11th to 20th	Day	14% 7% 2 4 3 3 3 2 5% 6% 52%	1886
	21st to end	Day	15% 9% 2 4 4 2 2 2 4 7% 49%	1600
December	1st to 10th	Day	10% 8% 2 6% 3 3 2 3 4 5% 53%	2610
	11th to 20th	Day	10% 10% 2 6% 4 3 3 2 4 6% 51%	3008
	21st to end	Day	19% 21% 5% 9% 4 3 3 2 4 4 26%	4367
January	1st to 10th	Night	14% 9% 4 10% 5% 4 3 2 4 5% 39%	5888
	11th to 20th	Night	8% 7% 3 9% 6% 5% 4 3 3 5% 47%	5900
	21st to end	Night	17% 10% 4 6% 3 2 2 2 3 4 45%	6490
February	1st to 10th	Night	16% 11% 3 6% 3 3 3 3 5% 5% 42%	2600
	11th to 20th	Night	15% 10% 3 7% 3 3 3 3 3 6% 44%	2533
	21st to end	Night	14% 8% 3 6% 4 4 3 3 4 5% 46%	1885
March	1st to 10th	Night	14% 10% 3 7% 4 3 3 2 4 4 47%	4919
	11th to 20th	Night	10% 6% 2 4 3 3 3 3 5% 6% 55%	4980
	21st to end	Night	10% 6% 3 6% 5% 4 5% 4 6% 8% 44%	5467
April	1st to 10th	Night	11% 6% 2 5% 4 3 3 3 5% 7% 51%	2070
	11th to 20th	Night	13% 7% 2 6% 3 3 3 3 5% 7% 47%	1975
	21st to end	Night	17% 8% 3 6% 3 4 4 3 5% 5% 41%	1974
May	1st to 10th	Night	13% 8% 2 5% 4 3 4 3 5% 8% 44%	2913
	11th to 20th	Night	14% 7% 3 6% 4 4 4 3 5% 7% 42%	2828
	21st to end	Night	10% 6% 3 6% 4 4 3 4 6% 9% 45%	3090
June	1st to 10th	Night	6% 4 2 4 4 4 4 4 7% 9% 52%	1558
	11th to 20th	Night	5% 3 1 4 3 4 4 3 7% 10% 55%	1520
	21st to end	Night	4 3 1 3 3 3 3 2 7% 10% 60%	1648
July	1st to 10th	Night	10% 4 2 5% 3 4 4 4 6% 9% 49%	2850
	11th to 20th	Night	3 2 1 4 3 4 4 3 5% 9% 60%	2850
	21st to end	Night	6% 4 2 4 4 3 3 4 6% 11% 53%	3098
August	1st to 10th	Night	3 3 1 3 3 3 4 4 6% 8% 63%	2836
	11th to 20th	Night	9% 4 1 5% 4 4 4 4 6% 8% 51%	2824
	21st to end	Night	3 3 2 4 3 3 3 3 5% 8% 62%	3476
September	1st to 10th	Night	9% 4 2 4 3 3 4 3 4 7% 56%	1900
	11th to 20th	Night	10% 5% 2 7% 4 3 4 2 5% 8% 52%	2026
	21st to end	Night	8% 4 2 5% 4 3 4 3 5% 6% 57%	2109
October	1st to 10th	Night	8% 4 1 4 2 2 3 2 4 7% 62%	2280
	11th to 20th	Night	14% 5% 1 4 3 2 3 3 4 5% 57%	2280
	21st to end	Night	15% 6% 2 4 3 3 2 2 4 5% 52%	2508
November	1st to 10th	Night	13% 5% 2 4 3 2 3 2 3 5% 61%	2340
	11th to 20th	Night	12% 6% 2 5% 4 2 3 3 4 5% 54%	2507
	21st to end	Night	15% 8% 2 4 3 3 3 3 4 5% 51%	2800
December	1st to 10th	Night	9% 9% 2 5% 4 3 3 3 4 6% 51%	4580
	11th to 20th	Night	17% 7% 3 6% 3 3 2 2 3 5% 48%	5199
	21st to end	Night	19% 16% 5% 8% 4 4 3 3 4 4 30%	6605

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	48% 2 8% 23% 16% 2	4078
	11th to 20th	Day	41% 3 8% 25% 17% 5%	4080
	21st to end	Day	45% 3 8% 19% 18% 8%	4488
February	1st to 10th	Day	50% 4 10% 22% 12% 2	1800
	11th to 20th	Day	45% 4 10% 21% 16% 4	1763
	21st to end	Day	45% 3 6% 22% 17% 7%	1759
March	1st to 10th	Day	37% 4 7% 22% 18% 12%	4936
	11th to 20th	Day	31% 4 8% 22% 23% 12%	4980
	21st to end	Day	47% 6% 14% 25% 7%	5464
April	1st to 10th	Day	40% 5% 11% 24% 18% 2	2330
	11th to 20th	Day	44% 5% 12% 20% 16% 2	2374
	21st to end	Day	50% 5% 10% 24% 11% 1	2422
May	1st to 10th	Day	47% 7% 11% 20% 13% 1	4250
	11th to 20th	Day	40% 9% 13% 25% 13%	4087
	21st to end	Day	42% 8% 14% 23% 13% 1	4489
June	1st to 10th	Day	32% 9% 15% 28% 15% 1	2612
	11th to 20th	Day	31% 6% 14% 30% 16% 2	2660
	21st to end	Day	23% 7% 16% 31% 18% 4	2521
July	1st to 10th	Day	36% 8% 16% 23% 15% 3	4056
	11th to 20th	Day	28% 8% 11% 35% 17% 2	4051
	21st to end	Day	29% 9% 23% 28% 10%	4325
August	1st to 10th	Day	25% 6% 17% 28% 24% 1	4090
	11th to 20th	Day	36% 7% 15% 27% 15% 1	4051
	21st to end	Day	26% 6% 11% 39% 15% 4	4179
September	1st to 10th	Day	33% 5% 11% 26% 16% 9%	2280
	11th to 20th	Day	35% 6% 10% 23% 24% 2	2150
	21st to end	Day	30% 8% 9% 26% 23% 4	2050
October	1st to 10th	Day	18% 2 6% 19% 37% 18%	3160
	11th to 20th	Day	20% 2 5% 25% 34% 14%	3140
	21st to end	Day	29% 3 7% 30% 26% 4	3428
November	1st to 10th	Day	30% 4 9% 28% 22% 6%	1958
	11th to 20th	Day	36% 4 7% 22% 23% 8%	1886
	21st to end	Day	38% 5% 8% 25% 23% 2	1600
December	1st to 10th	Day	35% 3 7% 35% 19% 1	2610
	11th to 20th	Day	37% 3 6% 27% 24% 2	3005
	21st to end	Day	63% 4 6% 18% 8% 1	4367
January	1st to 10th	Night	49% 3 10% 22% 14% 2	5888
	11th to 20th	Night	40% 4 8% 22% 23% 3	5900
	21st to end	Night	45% 2 8% 20% 20% 5%	6490
February	1st to 10th	Night	44% 4 11% 23% 14% 4	2600
	11th to 20th	Night	44% 3 9% 24% 17% 3	2534
	21st to end	Night	41% 3 8% 21% 21% 6%	1885
March	1st to 10th	Night	42% 4 7% 17% 24% 6%	4919
	11th to 20th	Night	31% 4 7% 23% 24% 11%	4980
	21st to end	Night	37% 6% 13% 28% 14% 1	5467
April	1st to 10th	Night	33% 4 13% 23% 21% 5%	2070
	11th to 20th	Night	36% 5% 9% 23% 20% 6%	1975
	21st to end	Night	43% 6% 12% 22% 17% 1	1974
May	1st to 10th	Night	39% 7% 12% 23% 15% 4	2940
	11th to 20th	Night	40% 7% 12% 26% 13% 1	2829
	21st to end	Night	35% 9% 13% 30% 12%	3099
June	1st to 10th	Night	26% 7% 17% 30% 17% 4	1558
	11th to 20th	Night	24% 7% 15% 31% 22% 3	1520
	21st to end	Night	20% 5% 16% 33% 21% 5%	1648
July	1st to 10th	Night	31% 7% 16% 25% 17% 5%	2805
	11th to 20th	Night	20% 5% 12% 38% 24% 2	2796
	21st to end	Night	25% 7% 19% 35% 14%	2999
August	1st to 10th	Night	19% 6% 16% 33% 24% 2	2826
	11th to 20th	Night	30% 7% 15% 29% 19% 1	2851
	21st to end	Night	20% 6% 13% 37% 20% 4	3476
September	1st to 10th	Night	28% 5% 10% 27% 21% 9%	1900
	11th to 20th	Night	32% 5% 9% 23% 26% 5%	2026
	21st to end	Night	27% 5% 9% 25% 30% 4	2109
October	1st to 10th	Night	14% 3 6% 17% 40% 20%	3800
	11th to 20th	Night	22% 3 4 20% 32% 19%	3779
	21st to end	Night	29% 3 6% 32% 25% 5%	4120
November	1st to 10th	Night	29% 3 9% 26% 26% 8%	2340
	11th to 20th	Night	33% 3 6% 24% 26% 7%	2507
	21st to end	Night	37% 4 8% 23% 24% 4	2800
December	1st to 10th	Night	35% 4 9% 34% 18% 1	4580
	11th to 20th	Night	41% 2 6% 24% 23% 3	5201
	21st to end	Night	58% 4 8% 20% 8% 2	6605

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% 38% 22% 5%	300
	11th to 20th	Day	24% 17% 41% 15% 2	300
	21st to end	Day	18% 13% 47% 17% 4	330
February	1st to 10th	Day	25% 16% 40% 16% 3	300
	11th to 20th	Day	23% 19% 42% 13% 3	300
	21st to end	Day	25% 18% 38% 16% 2	249
March	1st to 10th	Day	23% 14% 36% 21% 5%	300
	11th to 20th	Day	26% 16% 35% 20% 3	300
	21st to end	Day	26% 17% 41% 11% 5%	330
April	1st to 10th	Day	18% 20% 35% 22% 3 1	430
	11th to 20th	Day	20% 17% 39% 18% 6%	492
	21st to end	Day	24% 12% 32% 25% 6% 1	522
May	1st to 10th	Day	18% 13% 34% 26% 8% 1	703
	11th to 20th	Day	15% 9% 31% 27% 14% 4	676
	21st to end	Day	13% 7% 29% 26% 17% 7%	734
June	1st to 10th	Day	7% 4 19% 35% 26% 9%	680
	11th to 20th	Day	7% 2 18% 38% 26% 8%	680
	21st to end	Day	5% 3 26% 37% 24% 5%	680
July	1st to 10th	Day	12% 1 14% 32% 28% 13%	671
	11th to 20th	Day	4 2 14% 36% 34% 10%	668
	21st to end	Day	9% 2 11% 31% 33% 15%	739
August	1st to 10th	Day	9% 2 13% 40% 29% 7%	676
	11th to 20th	Day	9% 2 14% 37% 31% 8%	649
	21st to end	Day	10% 1 9% 29% 37% 13%	539
September	1st to 10th	Day	10% 1 11% 36% 31% 11%	490
	11th to 20th	Day	7% 3 14% 38% 27% 11%	360
	21st to end	Day	10% 6% 19% 36% 21% 8%	300
October	1st to 10th	Day	11% 5% 24% 32% 23% 5%	300
	11th to 20th	Day	14% 11% 36% 27% 11% 1	300
	21st to end	Day	26% 11% 31% 26% 4 2	330
November	1st to 10th	Day	16% 9% 39% 24% 10% 2	300
	11th to 20th	Day	16% 16% 36% 21% 8% 2	300
	21st to end	Day	23% 14% 34% 21% 7%	300
December	1st to 10th	Day	17% 13% 44% 16% 9% 1	300
	11th to 20th	Day	20% 14% 42% 16% 6% 1	300
	21st to end	Day	19% 22% 36% 20% 3	330
January	1st to 10th	Night	17% 15% 39% 24% 5%	1000
	11th to 20th	Night	18% 15% 42% 21% 4 1	1000
	21st to end	Night	18% 14% 42% 24% 3	1100
February	1st to 10th	Night	22% 13% 42% 21% 3	1000
	11th to 20th	Night	19% 17% 41% 21% 2	979
	21st to end	Night	21% 18% 36% 22% 2	565
March	1st to 10th	Night	19% 12% 41% 24% 4	600
	11th to 20th	Night	21% 13% 39% 23% 4	600
	21st to end	Night	20% 13% 41% 21% 4 1	660
April	1st to 10th	Night	14% 14% 38% 30% 4	600
	11th to 20th	Night	17% 12% 36% 29% 6%	593
	21st to end	Night	20% 10% 39% 23% 7% 1	600
May	1st to 10th	Night	15% 6% 37% 34% 8%	600
	11th to 20th	Night	15% 5% 28% 34% 17% 1	563
	21st to end	Night	11% 5% 29% 35% 19% 1	617
June	1st to 10th	Night	8% 2 17% 43% 29% 1	570
	11th to 20th	Night	6% 2 24% 44% 25% 1	570
	21st to end	Night	3 3 22% 51% 21% 1	570
July	1st to 10th	Night	7% 1 13% 39% 35% 4	555
	11th to 20th	Night	3 2 11% 46% 34% 3	552
	21st to end	Night	7% 1 9% 44% 34% 4	624
August	1st to 10th	Night	6% 1 11% 46% 33% 2	567
	11th to 20th	Night	6% 2 13% 47% 28% 4	564
	21st to end	Night	4 1 13% 40% 38% 4	627
September	1st to 10th	Night	11% 1 12% 44% 31% 2	570
	11th to 20th	Night	11% 2 13% 44% 28% 3	570
	21st to end	Night	10% 4 19% 43% 20% 4	589
October	1st to 10th	Night	9% 3 26% 38% 21% 3	760
	11th to 20th	Night	16% 6% 38% 31% 8% 1	760
	21st to end	Night	19% 10% 32% 29% 9%	836
November	1st to 10th	Night	15% 8% 41% 27% 10% 1	780
	11th to 20th	Night	14% 13% 39% 26% 8%	877
	21st to end	Night	20% 11% 37% 24% 7%	1000
December	1st to 10th	Night	18% 13% 40% 24% 5%	1000
	11th to 20th	Night	22% 12% 34% 28% 4	1000
	21st to end	Night	20% 14% 39% 23% 3	1100

Page generated at 2025-05-08 08:33:58. Version ac07

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