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 2024-01-31.

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% 11% 5% 8% 6% 3 5% 5% 5% 7% 30%	74760
	Night	16% 11% 5% 8% 6% 3 5% 4 5% 6% 31%	75368
Transparency	Day	53% 6% 11% 18% 10% 1	74481
	Night	54% 6% 11% 18% 10% 1	75166
Seeing	Day	23% 17% 28% 19% 10% 3	13512
	Night	23% 14% 27% 24% 11% 1	23387

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% 17% 10% 11% 8% 3 4 4 4 5% 16%	1706
	11th to 20th	Day	17% 19% 9% 13% 8% 4 4 4 4 5% 14%	1710
	21st to end	Day	15% 19% 11% 16% 9% 3 3 3 4 4 12%	1872
February	1st to 10th	Day	17% 18% 8% 12% 10% 3 4 3 4 4 18%	1620
	11th to 20th	Day	15% 14% 9% 13% 9% 4 5% 4 4 5% 17%	1596
	21st to end	Day	18% 16% 5% 13% 6% 3 4 4 4 4 22%	1480
March	1st to 10th	Day	18% 12% 8% 8% 5% 3 4 4 5% 7% 27%	1946
	11th to 20th	Day	17% 14% 5% 8% 7% 3 4 4 3 6% 29%	1980
	21st to end	Day	21% 12% 6% 8% 6% 3 3 4 4 5% 28%	2178
April	1st to 10th	Day	14% 12% 5% 7% 6% 3 4 4 4 7% 32%	2034
	11th to 20th	Day	19% 11% 3 6% 6% 4 4 4 4 6% 32%	2259
	21st to end	Day	21% 11% 4 6% 5% 3 4 4 3 6% 34%	2340
May	1st to 10th	Day	17% 10% 3 7% 7% 4 6% 5% 5% 6% 30%	2340
	11th to 20th	Day	19% 8% 4 6% 5% 3 5% 5% 6% 7% 33%	2301
	21st to end	Day	11% 6% 2 6% 6% 4 6% 5% 6% 8% 38%	2621
June	1st to 10th	Day	15% 6% 3 6% 6% 4 5% 6% 6% 8% 37%	2520
	11th to 20th	Day	15% 6% 2 6% 6% 3 5% 4 6% 9% 38%	2520
	21st to end	Day	13% 5% 3 5% 5% 3 4 5% 6% 10% 40%	2520
July	1st to 10th	Day	11% 6% 2 6% 6% 3 5% 5% 6% 9% 42%	2398
	11th to 20th	Day	12% 5% 2 5% 6% 4 6% 4 6% 10% 39%	2340
	21st to end	Day	10% 5% 3 5% 6% 3 6% 6% 7% 10% 39%	2547
August	1st to 10th	Day	10% 5% 3 5% 6% 4 6% 6% 6% 10% 39%	2327
	11th to 20th	Day	11% 6% 3 7% 7% 4 6% 7% 7% 8% 35%	2303
	21st to end	Day	12% 5% 2 5% 6% 4 6% 6% 7% 9% 38%	2520
September	1st to 10th	Day	17% 4 3 5% 6% 3 4 4 6% 8% 39%	2095
	11th to 20th	Day	12% 5% 3 6% 5% 3 4 5% 7% 9% 41%	1980
	21st to end	Day	19% 8% 2 5% 5% 3 4 4 4 8% 38%	1980
October	1st to 10th	Day	17% 6% 3 7% 5% 3 5% 5% 6% 7% 37%	1843
	11th to 20th	Day	23% 11% 3 6% 6% 3 4 4 5% 5% 31%	1800
	21st to end	Day	24% 12% 4 7% 6% 3 4 3 6% 6% 25%	1980
November	1st to 10th	Day	12% 12% 4 6% 6% 4 4 5% 5% 7% 35%	1686
	11th to 20th	Day	18% 17% 4 6% 6% 2 5% 4 4 7% 26%	1635
	21st to end	Day	18% 18% 7% 8% 7% 3 4 5% 5% 6% 19%	1520
December	1st to 10th	Day	16% 21% 11% 12% 7% 4 4 4 3 4 15%	1520
	11th to 20th	Day	18% 17% 8% 15% 6% 3 4 5% 5% 5% 15%	1910
	21st to end	Day	25% 24% 8% 10% 7% 3 3 3 3 4 9%	2833
January	1st to 10th	Night	17% 18% 8% 13% 6% 4 4 5% 3 5% 17%	2459
	11th to 20th	Night	19% 17% 9% 13% 7% 4 4 3 4 4 16%	2470
	21st to end	Night	16% 17% 10% 14% 9% 4 4 3 4 4 15%	2711
February	1st to 10th	Night	20% 15% 6% 12% 9% 4 4 4 4 5% 18%	2340
	11th to 20th	Night	16% 14% 7% 12% 9% 4 5% 5% 3 5% 20%	2246
	21st to end	Night	22% 11% 6% 10% 7% 4 5% 4 3 4 23%	1776
March	1st to 10th	Night	16% 11% 7% 8% 6% 3 4 5% 5% 5% 30%	2012
	11th to 20th	Night	17% 10% 4 7% 6% 3 4 4 5% 6% 33%	1980
	21st to end	Night	19% 11% 5% 7% 6% 3 4 4 5% 5% 31%	2178
April	1st to 10th	Night	17% 12% 5% 7% 6% 3 5% 4 4 6% 32%	1926
	11th to 20th	Night	16% 10% 3 7% 5% 4 5% 5% 6% 6% 35%	1665
	21st to end	Night	15% 9% 4 6% 6% 3 4 5% 6% 7% 35%	1620
May	1st to 10th	Night	17% 8% 4 7% 6% 3 5% 5% 5% 6% 32%	1620
	11th to 20th	Night	15% 8% 3 6% 5% 4 5% 4 6% 8% 36%	1592
	21st to end	Night	11% 5% 2 5% 5% 4 5% 5% 6% 11% 43%	1650
June	1st to 10th	Night	10% 6% 3 5% 5% 3 6% 6% 6% 7% 42%	1440
	11th to 20th	Night	11% 5% 3 6% 5% 4 6% 5% 6% 8% 43%	1440
	21st to end	Night	12% 4 2 5% 4 3 5% 5% 6% 10% 43%	1440
July	1st to 10th	Night	7% 5% 2 5% 5% 3 5% 5% 4 9% 50%	1556
	11th to 20th	Night	9% 4 2 5% 5% 3 4 4 6% 9% 48%	1620
	21st to end	Night	8% 6% 2 5% 5% 4 5% 5% 6% 9% 44%	1771
August	1st to 10th	Night	7% 4 2 5% 5% 3 5% 5% 6% 8% 49%	1611
	11th to 20th	Night	10% 6% 2 6% 5% 3 5% 4 5% 9% 45%	1598
	21st to end	Night	10% 5% 2 5% 4 3 5% 4 6% 8% 47%	1818
September	1st to 10th	Night	13% 5% 2 5% 5% 3 4 5% 6% 7% 45%	1862
	11th to 20th	Night	12% 4 2 4 4 3 4 4 5% 7% 51%	1980
	21st to end	Night	16% 6% 2 6% 6% 3 5% 5% 4 6% 41%	1980
October	1st to 10th	Night	14% 6% 3 5% 5% 3 4 5% 6% 7% 42%	2116
	11th to 20th	Night	19% 9% 3 6% 6% 3 5% 5% 5% 7% 33%	2160
	21st to end	Night	26% 9% 3 5% 6% 3 4 4 5% 7% 28%	2376
November	1st to 10th	Night	14% 9% 3 7% 6% 3 4 4 6% 6% 38%	2389
	11th to 20th	Night	16% 17% 5% 8% 6% 3 4 4 5% 6% 27%	2541
	21st to end	Night	18% 17% 5% 7% 6% 3 5% 4 5% 6% 22%	2660
December	1st to 10th	Night	20% 19% 9% 9% 7% 3 5% 3 4 5% 17%	2660
	11th to 20th	Night	17% 19% 8% 11% 6% 3 4 4 4 5% 19%	3285
	21st to end	Night	25% 21% 9% 9% 7% 3 4 4 4 4 10%	4820

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	72% 5% 11% 9% 4	1707
	11th to 20th	Day	74% 5% 11% 8% 2	1710
	21st to end	Day	78% 4 8% 8% 3	1872
February	1st to 10th	Day	71% 4 9% 11% 5%	1620
	11th to 20th	Day	70% 4 8% 11% 6%	1605
	21st to end	Day	65% 5% 11% 12% 6% 2	1480
March	1st to 10th	Day	58% 5% 13% 19% 6%	1946
	11th to 20th	Day	58% 5% 9% 16% 10% 1	1980
	21st to end	Day	60% 4 8% 17% 10% 2	2178
April	1st to 10th	Day	52% 6% 12% 17% 13% 1	2034
	11th to 20th	Day	53% 6% 10% 16% 13% 2	2259
	21st to end	Day	53% 4 10% 20% 10% 2	2340
May	1st to 10th	Day	53% 8% 10% 18% 9% 2	2340
	11th to 20th	Day	50% 7% 10% 17% 14% 2	2305
	21st to end	Day	43% 8% 12% 23% 12% 2	2621
June	1st to 10th	Day	44% 8% 11% 24% 12% 1	2520
	11th to 20th	Day	43% 9% 13% 20% 14% 1	2520
	21st to end	Day	38% 9% 12% 24% 15% 2	2520
July	1st to 10th	Day	40% 7% 11% 24% 16% 3	2333
	11th to 20th	Day	40% 8% 13% 23% 15% 1	2271
	21st to end	Day	38% 9% 14% 21% 16% 2	2405
August	1st to 10th	Day	38% 10% 13% 26% 13%	2314
	11th to 20th	Day	42% 11% 14% 21% 10% 2	2303
	21st to end	Day	40% 9% 14% 21% 13% 3	2520
September	1st to 10th	Day	43% 7% 14% 19% 14% 3	2095
	11th to 20th	Day	39% 8% 13% 24% 15% 1	1980
	21st to end	Day	46% 5% 10% 24% 14% 1	1980
October	1st to 10th	Day	46% 6% 12% 21% 14% 1	1843
	11th to 20th	Day	56% 5% 11% 20% 8% 1	1800
	21st to end	Day	60% 5% 12% 12% 9% 1	1980
November	1st to 10th	Day	47% 5% 13% 20% 13% 1	1686
	11th to 20th	Day	58% 6% 11% 15% 7% 3	1635
	21st to end	Day	67% 5% 10% 12% 6%	1520
December	1st to 10th	Day	75% 5% 8% 10% 3	1520
	11th to 20th	Day	72% 6% 8% 12% 3	1906
	21st to end	Day	82% 4 8% 6% 1	2833
January	1st to 10th	Night	70% 5% 9% 12% 4	2459
	11th to 20th	Night	72% 5% 10% 10% 3	2470
	21st to end	Night	73% 4 9% 10% 3 1	2711
February	1st to 10th	Night	69% 5% 9% 12% 4	2340
	11th to 20th	Night	68% 4 9% 14% 6%	2248
	21st to end	Night	65% 5% 8% 14% 7% 1	1776
March	1st to 10th	Night	56% 5% 10% 20% 9%	2012
	11th to 20th	Night	52% 5% 11% 19% 11% 2	1980
	21st to end	Night	56% 5% 8% 18% 12% 2	2178
April	1st to 10th	Night	53% 6% 11% 16% 12% 2	1926
	11th to 20th	Night	49% 5% 11% 19% 14% 2	1665
	21st to end	Night	48% 5% 12% 20% 13% 3	1620
May	1st to 10th	Night	51% 6% 10% 17% 12% 3	1620
	11th to 20th	Night	46% 7% 10% 19% 14% 4	1593
	21st to end	Night	35% 8% 16% 25% 15% 2	1651
June	1st to 10th	Night	39% 10% 10% 24% 15% 2	1440
	11th to 20th	Night	38% 8% 13% 22% 18% 2	1440
	21st to end	Night	35% 10% 12% 24% 18% 1	1440
July	1st to 10th	Night	34% 7% 11% 24% 19% 4	1511
	11th to 20th	Night	31% 9% 12% 25% 19% 3	1566
	21st to end	Night	37% 8% 13% 23% 17% 3	1672
August	1st to 10th	Night	31% 9% 14% 28% 17% 1	1600
	11th to 20th	Night	36% 9% 14% 26% 13% 2	1598
	21st to end	Night	33% 7% 13% 25% 17% 3	1818
September	1st to 10th	Night	37% 7% 13% 24% 16% 3	1862
	11th to 20th	Night	32% 6% 14% 26% 20% 2	1980
	21st to end	Night	43% 6% 11% 22% 17% 1	1980
October	1st to 10th	Night	39% 7% 14% 21% 18% 1	2116
	11th to 20th	Night	50% 6% 11% 21% 11% 1	2160
	21st to end	Night	55% 5% 12% 17% 9% 1	2376
November	1st to 10th	Night	44% 6% 13% 22% 12% 3	2389
	11th to 20th	Night	59% 4 11% 16% 7% 3	2541
	21st to end	Night	63% 6% 11% 15% 5%	2660
December	1st to 10th	Night	70% 4 11% 10% 4	2660
	11th to 20th	Night	68% 4 12% 13% 2	3288
	21st to end	Night	78% 5% 9% 7% 1	4820

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	34% 24% 30% 8% 3	270
	11th to 20th	Day	32% 33% 26% 8% 2	270
	21st to end	Day	32% 32% 26% 7% 2	294
February	1st to 10th	Day	38% 23% 35% 3	240
	11th to 20th	Day	38% 32% 27% 4	240
	21st to end	Day	38% 31% 27% 4	198
March	1st to 10th	Day	28% 25% 31% 13% 3	386
	11th to 20th	Day	30% 22% 32% 12% 4 1	420
	21st to end	Day	34% 24% 24% 14% 3	462
April	1st to 10th	Day	26% 25% 28% 14% 6% 1	420
	11th to 20th	Day	30% 19% 27% 14% 9% 2	412
	21st to end	Day	32% 17% 29% 15% 5% 1	420
May	1st to 10th	Day	27% 22% 28% 16% 5% 3	423
	11th to 20th	Day	25% 13% 30% 21% 7% 3	447
	21st to end	Day	14% 11% 31% 25% 14% 5%	485
June	1st to 10th	Day	15% 12% 38% 23% 10% 2	450
	11th to 20th	Day	18% 14% 27% 25% 13% 3	450
	21st to end	Day	14% 12% 34% 24% 12% 4	450
July	1st to 10th	Day	12% 7% 23% 29% 21% 7%	445
	11th to 20th	Day	13% 8% 29% 27% 16% 7%	444
	21st to end	Day	10% 8% 33% 28% 15% 7%	488
August	1st to 10th	Day	12% 8% 23% 29% 20% 8%	446
	11th to 20th	Day	15% 9% 26% 25% 15% 9%	439
	21st to end	Day	12% 7% 26% 29% 18% 8%	495
September	1st to 10th	Day	15% 10% 23% 26% 20% 7%	450
	11th to 20th	Day	12% 6% 22% 29% 22% 10%	450
	21st to end	Day	22% 13% 26% 20% 14% 5%	450
October	1st to 10th	Day	14% 14% 30% 20% 18% 4	450
	11th to 20th	Day	26% 20% 32% 17% 4 1	450
	21st to end	Day	33% 19% 29% 16% 3	495
November	1st to 10th	Day	26% 20% 27% 16% 9% 2	284
	11th to 20th	Day	35% 20% 27% 13% 5%	234
	21st to end	Day	29% 22% 41% 8% 1	180
December	1st to 10th	Day	31% 27% 26% 12% 2 2	180
	11th to 20th	Day	31% 28% 32% 8% 1	180
	21st to end	Day	36% 27% 27% 10%	215
January	1st to 10th	Night	30% 25% 31% 11% 3	760
	11th to 20th	Night	32% 23% 29% 13% 2	760
	21st to end	Night	27% 24% 30% 17% 2	835
February	1st to 10th	Night	33% 20% 30% 16% 1	720
	11th to 20th	Night	29% 21% 33% 15% 1	703
	21st to end	Night	33% 23% 30% 13% 2	592
March	1st to 10th	Night	25% 21% 32% 19% 3	720
	11th to 20th	Night	26% 19% 28% 19% 6% 1	720
	21st to end	Night	26% 17% 29% 21% 6%	792
April	1st to 10th	Night	25% 15% 33% 21% 5%	720
	11th to 20th	Night	23% 14% 34% 19% 8% 1	601
	21st to end	Night	19% 13% 36% 26% 6%	540
May	1st to 10th	Night	23% 11% 26% 29% 10%	540
	11th to 20th	Night	18% 9% 29% 32% 10% 2	531
	21st to end	Night	13% 4 28% 34% 19% 2	490
June	1st to 10th	Night	11% 5% 33% 39% 12% 1	360
	11th to 20th	Night	13% 5% 26% 40% 14% 1	360
	21st to end	Night	11% 8% 29% 35% 17%	360
July	1st to 10th	Night	7% 3 19% 38% 28% 4	461
	11th to 20th	Night	10% 3 23% 36% 25% 3	522
	21st to end	Night	10% 4 18% 41% 24% 2	591
August	1st to 10th	Night	8% 3 19% 40% 28% 3	537
	11th to 20th	Night	11% 5% 16% 35% 30% 3	534
	21st to end	Night	11% 4 21% 31% 28% 4	630
September	1st to 10th	Night	16% 6% 19% 31% 25% 3	720
	11th to 20th	Night	13% 4 18% 35% 26% 4	720
	21st to end	Night	18% 9% 24% 28% 17% 4	720
October	1st to 10th	Night	19% 10% 26% 25% 18% 2	720
	11th to 20th	Night	24% 15% 29% 24% 8% 1	720
	21st to end	Night	31% 15% 30% 21% 4	792
November	1st to 10th	Night	21% 16% 27% 26% 10% 1	740
	11th to 20th	Night	28% 20% 27% 17% 6% 1	760
	21st to end	Night	32% 18% 31% 14% 5%	760
December	1st to 10th	Night	33% 21% 27% 14% 4	760
	11th to 20th	Night	29% 24% 29% 15% 3	760
	21st to end	Night	33% 19% 32% 15% 1	836

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