Eldon Russell Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Eldon Russell Park clear sky chart from 2005-11-06 to 2025-02-21.

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	16% 12% 4 10% 5% 4 4 4 5% 7% 29%	108635
	Night	16% 13% 5% 10% 5% 4 4 3 5% 6% 29%	109909
Transparency	Day	53% 6% 11% 19% 10% 1	112311
	Night	55% 5% 11% 18% 10% 1	114372
Seeing	Day	23% 17% 29% 19% 10% 3	14874
	Night	23% 15% 27% 24% 11% 1	24756

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	13% 21% 9% 26% 5% 3 3 2 3 4 13%	4056
	11th to 20th	Day	11% 21% 7% 22% 9% 7% 4 2 3 4 11%	4060
	21st to end	Day	20% 19% 10% 15% 7% 5% 3 3 3 3 12%	4466
February	1st to 10th	Day	15% 20% 6% 13% 8% 4 3 2 4 4 19%	1800
	11th to 20th	Day	14% 16% 8% 15% 8% 5% 4 3 4 5% 19%	1779
	21st to end	Day	18% 16% 4 13% 6% 4 5% 3 4 4 22%	1570
March	1st to 10th	Day	22% 12% 8% 8% 5% 4 3 3 4 6% 25%	3389
	11th to 20th	Day	13% 15% 6% 9% 6% 4 4 3 3 5% 32%	3480
	21st to end	Day	20% 12% 5% 10% 5% 4 4 3 4 5% 29%	3815
April	1st to 10th	Day	14% 14% 4 8% 5% 4 4 4 5% 7% 31%	2147
	11th to 20th	Day	19% 12% 3 7% 5% 4 4 3 5% 6% 33%	2387
	21st to end	Day	20% 12% 4 7% 4 4 3 4 3 6% 33%	2470
May	1st to 10th	Day	20% 9% 3 8% 5% 5% 5% 4 5% 6% 30%	4082
	11th to 20th	Day	20% 9% 3 7% 4 4 4 3 6% 7% 33%	4081
	21st to end	Day	12% 6% 2 7% 5% 5% 6% 4 6% 7% 40%	4635
June	1st to 10th	Day	14% 6% 2 7% 6% 5% 6% 4 6% 8% 36%	2660
	11th to 20th	Day	14% 7% 2 6% 5% 4 5% 4 6% 9% 38%	2660
	21st to end	Day	13% 5% 2 6% 4 4 5% 4 6% 10% 39%	2660
July	1st to 10th	Day	9% 6% 2 7% 5% 5% 5% 5% 7% 9% 39%	4220
	11th to 20th	Day	9% 5% 2 6% 5% 5% 5% 4 7% 10% 42%	4120
	21st to end	Day	10% 6% 3 7% 5% 5% 5% 5% 6% 9% 39%	4466
August	1st to 10th	Day	15% 7% 3 7% 5% 5% 6% 5% 7% 9% 33%	4104
	11th to 20th	Day	12% 6% 3 7% 5% 5% 6% 5% 7% 8% 35%	4044
	21st to end	Day	10% 5% 2 6% 5% 5% 6% 4 6% 10% 40%	4422
September	1st to 10th	Day	17% 5% 2 6% 5% 4 4 3 6% 7% 41%	2211
	11th to 20th	Day	11% 6% 2 6% 4 4 4 4 7% 8% 43%	2090
	21st to end	Day	21% 9% 2 6% 4 3 4 3 4 7% 36%	2090
October	1st to 10th	Day	16% 6% 3 7% 4 4 4 4 6% 7% 38%	1945
	11th to 20th	Day	22% 11% 3 7% 5% 4 4 2 5% 5% 33%	1900
	21st to end	Day	22% 13% 3 8% 5% 5% 4 2 6% 6% 26%	2090
November	1st to 10th	Day	12% 13% 3 7% 6% 4 4 4 5% 7% 35%	1776
	11th to 20th	Day	18% 18% 4 8% 5% 4 4 3 4 7% 26%	1721
	21st to end	Day	18% 20% 6% 10% 7% 4 4 3 5% 6% 18%	1600
December	1st to 10th	Day	16% 19% 11% 15% 5% 5% 4 3 4 4 15%	2600
	11th to 20th	Day	23% 22% 7% 11% 6% 3 3 3 4 5% 13%	2990
	21st to end	Day	24% 24% 6% 15% 6% 4 3 3 3 4 9%	4049
January	1st to 10th	Night	14% 19% 10% 26% 4 4 3 3 3 4 11%	5889
	11th to 20th	Night	12% 18% 10% 20% 9% 6% 5% 3 4 3 10%	5900
	21st to end	Night	19% 17% 9% 15% 7% 4 4 3 3 4 14%	6490
February	1st to 10th	Night	18% 16% 5% 14% 8% 4 4 3 4 5% 18%	2600
	11th to 20th	Night	15% 15% 6% 14% 8% 6% 5% 4 4 5% 19%	2503
	21st to end	Night	20% 12% 5% 12% 6% 5% 5% 3 4 4 23%	1885
March	1st to 10th	Night	21% 14% 4 7% 4 3 3 3 4 4 32%	3462
	11th to 20th	Night	15% 12% 7% 9% 5% 4 4 4 4 5% 32%	3480
	21st to end	Night	19% 12% 5% 8% 5% 4 4 3 4 4 33%	3817
April	1st to 10th	Night	17% 15% 3 8% 5% 4 4 3 4 5% 31%	2033
	11th to 20th	Night	17% 10% 2 8% 4 4 4 4 6% 6% 34%	1758
	21st to end	Night	15% 10% 3 7% 5% 4 4 4 5% 7% 36%	1710
May	1st to 10th	Night	24% 9% 3 7% 4 3 4 4 5% 6% 30%	2813
	11th to 20th	Night	16% 10% 3 5% 4 4 4 3 6% 8% 36%	2812
	21st to end	Night	12% 4 2 4 4 4 4 4 6% 11% 45%	2902
June	1st to 10th	Night	11% 7% 3 6% 5% 5% 5% 4 6% 7% 41%	1520
	11th to 20th	Night	10% 5% 2 7% 4 5% 5% 5% 7% 7% 43%	1520
	21st to end	Night	11% 5% 2 5% 4 5% 5% 4 6% 10% 42%	1520
July	1st to 10th	Night	10% 6% 2 6% 4 4 4 3 5% 10% 46%	2734
	11th to 20th	Night	10% 5% 2 5% 4 5% 4 3 6% 8% 49%	2840
	21st to end	Night	7% 6% 2 7% 5% 5% 4 4 6% 9% 45%	3087
August	1st to 10th	Night	12% 8% 3 7% 4 4 5% 4 6% 7% 40%	2825
	11th to 20th	Night	14% 9% 3 7% 4 4 4 3 4 7% 43%	2785
	21st to end	Night	8% 5% 2 6% 5% 5% 5% 4 7% 7% 45%	3188
September	1st to 10th	Night	13% 6% 2 6% 4 4 4 4 6% 7% 46%	1966
	11th to 20th	Night	11% 4 2 5% 4 4 4 3 5% 6% 52%	2090
	21st to end	Night	18% 7% 2 7% 5% 5% 4 3 4 5% 39%	2090
October	1st to 10th	Night	14% 6% 3 5% 4 4 4 4 6% 7% 43%	2234
	11th to 20th	Night	18% 9% 3 7% 5% 4 4 4 6% 6% 34%	2280
	21st to end	Night	24% 10% 2 6% 5% 4 4 3 5% 7% 30%	2508
November	1st to 10th	Night	14% 10% 3 7% 5% 4 4 3 5% 6% 38%	2518
	11th to 20th	Night	16% 19% 4 9% 5% 4 4 3 5% 6% 26%	2675
	21st to end	Night	18% 19% 5% 8% 5% 4 6% 3 5% 6% 21%	2800
December	1st to 10th	Night	14% 18% 8% 13% 7% 6% 5% 3 5% 5% 16%	4580
	11th to 20th	Night	19% 22% 9% 12% 5% 3 3 3 3 4 16%	5205
	21st to end	Night	23% 22% 7% 12% 5% 4 4 3 4 4 12%	6890

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	79% 3 8% 7% 3 1	4057
	11th to 20th	Day	81% 3 8% 7% 2	4060
	21st to end	Day	79% 3 6% 9% 3	4466
February	1st to 10th	Day	69% 4 9% 12% 5%	1800
	11th to 20th	Day	69% 4 9% 13% 6%	1788
	21st to end	Day	64% 5% 11% 12% 7% 2	1570
March	1st to 10th	Day	59% 6% 9% 21% 4	3389
	11th to 20th	Day	54% 6% 14% 19% 6% 1	3480
	21st to end	Day	57% 4 10% 16% 11% 1	3815
April	1st to 10th	Day	52% 6% 12% 16% 13% 1	2147
	11th to 20th	Day	52% 6% 10% 17% 13% 2	2387
	21st to end	Day	53% 4 10% 20% 10% 2	2470
May	1st to 10th	Day	53% 8% 9% 20% 9% 1	4120
	11th to 20th	Day	49% 8% 10% 22% 9% 1	4085
	21st to end	Day	40% 9% 12% 20% 15% 5%	4649
June	1st to 10th	Day	44% 8% 11% 24% 12% 1	2660
	11th to 20th	Day	42% 8% 13% 21% 15% 1	2660
	21st to end	Day	38% 8% 12% 24% 15% 2	2660
July	1st to 10th	Day	40% 6% 12% 23% 15% 3	4155
	11th to 20th	Day	35% 7% 12% 26% 18% 1	4051
	21st to end	Day	40% 8% 14% 18% 18% 1	4324
August	1st to 10th	Day	45% 8% 13% 23% 11%	4091
	11th to 20th	Day	42% 9% 11% 29% 8% 1	4083
	21st to end	Day	38% 7% 14% 28% 11% 2	4422
September	1st to 10th	Day	41% 7% 14% 20% 15% 3	2211
	11th to 20th	Day	38% 7% 13% 24% 16% 1	2090
	21st to end	Day	48% 5% 10% 23% 13% 1	2090
October	1st to 10th	Day	35% 5% 14% 27% 19% 1	3231
	11th to 20th	Day	49% 4 10% 19% 14% 4	3140
	21st to end	Day	45% 4 14% 23% 13% 1	3428
November	1st to 10th	Day	47% 5% 13% 21% 13% 1	1776
	11th to 20th	Day	59% 6% 11% 15% 7% 3	1721
	21st to end	Day	68% 5% 9% 12% 6%	1600
December	1st to 10th	Day	73% 5% 11% 10% 2	2600
	11th to 20th	Day	74% 5% 7% 12% 2	2986
	21st to end	Day	82% 3 7% 7% 1	4049
January	1st to 10th	Night	78% 3 6% 9% 3	5889
	11th to 20th	Night	80% 4 7% 7% 2	5900
	21st to end	Night	75% 3 8% 9% 4	6490
February	1st to 10th	Night	69% 5% 9% 13% 5%	2600
	11th to 20th	Night	68% 4 9% 14% 5%	2505
	21st to end	Night	64% 5% 8% 14% 8% 1	1885
March	1st to 10th	Night	56% 5% 11% 20% 8%	3462
	11th to 20th	Night	53% 5% 16% 16% 8% 1	3480
	21st to end	Night	53% 4 11% 20% 11% 1	3817
April	1st to 10th	Night	54% 6% 11% 15% 12% 2	2033
	11th to 20th	Night	49% 6% 11% 19% 14% 2	1758
	21st to end	Night	47% 5% 11% 20% 13% 3	1710
May	1st to 10th	Night	54% 6% 9% 19% 9% 2	2840
	11th to 20th	Night	44% 8% 11% 23% 12% 2	2813
	21st to end	Night	31% 7% 15% 26% 18% 3	2909
June	1st to 10th	Night	39% 9% 10% 24% 15% 2	1520
	11th to 20th	Night	37% 8% 13% 22% 18% 2	1520
	21st to end	Night	36% 10% 12% 24% 17% 1	1520
July	1st to 10th	Night	38% 5% 11% 24% 18% 4	2689
	11th to 20th	Night	33% 7% 12% 29% 18% 2	2786
	21st to end	Night	36% 7% 13% 19% 24% 2	2988
August	1st to 10th	Night	42% 7% 12% 24% 13% 1	2814
	11th to 20th	Night	41% 7% 10% 30% 11% 1	2812
	21st to end	Night	36% 7% 12% 29% 15% 2	3188
September	1st to 10th	Night	36% 7% 12% 26% 16% 3	1966
	11th to 20th	Night	31% 6% 14% 26% 21% 2	2090
	21st to end	Night	45% 6% 11% 21% 16% 1	2090
October	1st to 10th	Night	34% 5% 9% 28% 22% 1	3728
	11th to 20th	Night	44% 6% 11% 21% 16% 3	3779
	21st to end	Night	41% 5% 13% 26% 15% 1	4120
November	1st to 10th	Night	44% 6% 13% 22% 13% 3	2518
	11th to 20th	Night	59% 5% 10% 16% 7% 3	2675
	21st to end	Night	63% 6% 11% 15% 4	2800
December	1st to 10th	Night	69% 5% 13% 10% 3	4580
	11th to 20th	Night	73% 3 9% 13% 2	5208
	21st to end	Night	76% 5% 9% 9% 1	6890

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	35% 25% 30% 7% 3	300
	11th to 20th	Day	33% 32% 26% 7% 2	300
	21st to end	Day	32% 32% 27% 7% 2	330
February	1st to 10th	Day	37% 24% 33% 5% 1	300
	11th to 20th	Day	37% 30% 27% 6%	300
	21st to end	Day	37% 31% 28% 4	225
March	1st to 10th	Day	29% 24% 30% 13% 4	425
	11th to 20th	Day	30% 22% 32% 12% 3 1	460
	21st to end	Day	34% 24% 24% 14% 3	506
April	1st to 10th	Day	27% 25% 28% 13% 5% 1	460
	11th to 20th	Day	31% 19% 27% 13% 8% 2	452
	21st to end	Day	30% 18% 30% 15% 5% 1	460
May	1st to 10th	Day	27% 22% 28% 16% 5% 3	463
	11th to 20th	Day	24% 13% 30% 21% 8% 3	487
	21st to end	Day	14% 12% 30% 26% 13% 5%	529
June	1st to 10th	Day	15% 14% 37% 22% 11% 2	490
	11th to 20th	Day	17% 14% 28% 26% 12% 3	490
	21st to end	Day	14% 13% 34% 23% 11% 4	490
July	1st to 10th	Day	13% 7% 25% 29% 20% 7%	485
	11th to 20th	Day	12% 9% 29% 27% 16% 7%	484
	21st to end	Day	10% 8% 32% 27% 16% 7%	532
August	1st to 10th	Day	13% 9% 23% 29% 19% 7%	486
	11th to 20th	Day	15% 9% 28% 25% 15% 9%	479
	21st to end	Day	11% 7% 25% 29% 20% 8%	539
September	1st to 10th	Day	14% 10% 23% 26% 20% 7%	490
	11th to 20th	Day	11% 5% 21% 30% 22% 10%	490
	21st to end	Day	24% 12% 26% 20% 13% 5%	490
October	1st to 10th	Day	14% 14% 30% 20% 18% 3	490
	11th to 20th	Day	25% 19% 31% 17% 5% 2	490
	21st to end	Day	32% 19% 29% 17% 3	539
November	1st to 10th	Day	26% 20% 29% 15% 8% 2	314
	11th to 20th	Day	33% 20% 30% 12% 4	260
	21st to end	Day	31% 21% 41% 8% 1	200
December	1st to 10th	Day	31% 27% 28% 12% 2 2	200
	11th to 20th	Day	34% 26% 30% 8% 2	200
	21st to end	Day	36% 27% 26% 10%	239
January	1st to 10th	Night	30% 25% 31% 12% 3	800
	11th to 20th	Night	32% 25% 29% 13% 2	800
	21st to end	Night	27% 25% 30% 16% 2	880
February	1st to 10th	Night	32% 20% 30% 17% 1	800
	11th to 20th	Night	30% 22% 32% 15% 1	783
	21st to end	Night	32% 23% 29% 14% 2	629
March	1st to 10th	Night	25% 20% 31% 20% 4	760
	11th to 20th	Night	27% 20% 28% 19% 6% 1	760
	21st to end	Night	26% 17% 30% 21% 6%	836
April	1st to 10th	Night	26% 15% 33% 21% 5%	760
	11th to 20th	Night	24% 15% 34% 19% 8% 1	634
	21st to end	Night	19% 13% 35% 27% 6%	570
May	1st to 10th	Night	23% 11% 26% 30% 10%	570
	11th to 20th	Night	17% 10% 28% 33% 10% 2	561
	21st to end	Night	13% 4 28% 35% 18% 2	517
June	1st to 10th	Night	12% 5% 32% 38% 12% 1	380
	11th to 20th	Night	13% 5% 26% 41% 14% 1	380
	21st to end	Night	11% 8% 29% 35% 17%	380
July	1st to 10th	Night	8% 3 20% 38% 27% 4	488
	11th to 20th	Night	10% 3 23% 36% 25% 3	552
	21st to end	Night	10% 4 18% 42% 25% 2	624
August	1st to 10th	Night	9% 4 19% 39% 27% 2	567
	11th to 20th	Night	11% 5% 16% 35% 29% 3	564
	21st to end	Night	11% 4 21% 32% 28% 3	665
September	1st to 10th	Night	16% 6% 19% 31% 25% 3	760
	11th to 20th	Night	13% 3 17% 36% 27% 4	760
	21st to end	Night	19% 9% 24% 28% 16% 4	760
October	1st to 10th	Night	18% 10% 27% 25% 18% 2	760
	11th to 20th	Night	23% 15% 28% 23% 9% 1	760
	21st to end	Night	29% 15% 29% 22% 5%	836
November	1st to 10th	Night	21% 16% 27% 26% 9% 1	780
	11th to 20th	Night	29% 21% 27% 17% 5% 1	800
	21st to end	Night	33% 19% 30% 14% 4	800
December	1st to 10th	Night	33% 21% 27% 14% 4	800
	11th to 20th	Night	30% 24% 28% 15% 3	800
	21st to end	Night	33% 19% 31% 15% 1	880

Page generated at 2025-02-18 03:26:30. Version ac07

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