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 2026-06-16.

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	15% 11% 4 10% 5% 5% 4 4 5% 7% 30%	137293
	Night	15% 13% 5% 10% 5% 4 4 3 5% 6% 29%	134690
Transparency	Day	53% 5% 10% 19% 11% 1	140925
	Night	55% 5% 10% 18% 11% 1	139128
Seeing	Day	24% 17% 28% 18% 9% 3	16620
	Night	23% 15% 27% 24% 10% 1	26417

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% 20% 8% 26% 6% 3 3 2 3 4 10%	5258
	11th to 20th	Day	10% 20% 8% 22% 10% 8% 4 2 3 3 10%	5280
	21st to end	Day	17% 17% 8% 15% 9% 7% 4 3 3 4 13%	5780
February	1st to 10th	Day	15% 19% 6% 13% 8% 5% 4 3 4 4 20%	1890
	11th to 20th	Day	14% 16% 8% 16% 8% 5% 4 3 4 5% 18%	1871
	21st to end	Day	16% 16% 5% 14% 5% 4 5% 3 4 5% 22%	1730
March	1st to 10th	Day	17% 10% 9% 12% 5% 3 3 3 4 6% 28%	4969
	11th to 20th	Day	12% 12% 5% 10% 5% 5% 4 3 4 5% 34%	5090
	21st to end	Day	18% 13% 6% 11% 5% 4 4 3 4 5% 28%	5586
April	1st to 10th	Day	16% 14% 4 9% 5% 3 4 4 5% 7% 30%	2373
	11th to 20th	Day	18% 12% 3 7% 5% 4 4 3 5% 6% 32%	2641
	21st to end	Day	19% 12% 4 7% 4 4 3 4 3 6% 34%	2730
May	1st to 10th	Day	20% 10% 3 8% 5% 5% 5% 4 5% 6% 29%	7616
	11th to 20th	Day	17% 9% 3 7% 4 4 4 4 6% 8% 33%	7626
	21st to end	Day	19% 7% 2 6% 4 5% 5% 3 6% 6% 37%	8690
June	1st to 10th	Day	14% 6% 2 7% 5% 4 5% 4 6% 8% 38%	2940
	11th to 20th	Day	15% 7% 2 7% 5% 4 5% 4 6% 8% 37%	2870
	21st to end	Day	12% 5% 2 6% 4 4 5% 4 7% 11% 40%	2800
July	1st to 10th	Day	9% 6% 2 7% 5% 5% 5% 4 6% 9% 43%	6042
	11th to 20th	Day	10% 5% 2 7% 5% 5% 5% 4 7% 9% 38%	5900
	21st to end	Day	11% 6% 3 6% 5% 5% 4 4 6% 9% 42%	6424
August	1st to 10th	Day	14% 6% 3 7% 5% 5% 6% 5% 7% 9% 33%	4234
	11th to 20th	Day	12% 6% 3 7% 5% 5% 6% 5% 7% 8% 35%	4174
	21st to end	Day	10% 5% 2 6% 5% 5% 6% 4 7% 10% 40%	4562
September	1st to 10th	Day	16% 4 2 6% 5% 4 4 3 6% 7% 42%	2327
	11th to 20th	Day	11% 5% 2 6% 4 4 4 4 7% 8% 44%	2200
	21st to end	Day	20% 9% 2 5% 5% 4 4 3 4 7% 36%	2200
October	1st to 10th	Day	16% 6% 3 7% 4 4 4 4 6% 7% 40%	2047
	11th to 20th	Day	21% 10% 3 7% 5% 4 4 3 5% 5% 33%	2000
	21st to end	Day	22% 12% 3 8% 5% 5% 4 3 6% 6% 27%	2200
November	1st to 10th	Day	12% 13% 3 7% 6% 4 4 4 5% 7% 35%	1867
	11th to 20th	Day	17% 19% 4 8% 5% 4 4 3 4 7% 25%	1807
	21st to end	Day	18% 20% 6% 9% 6% 4 4 3 5% 5% 17%	1680
December	1st to 10th	Day	16% 19% 11% 15% 5% 5% 4 3 4 4 14%	2680
	11th to 20th	Day	22% 21% 7% 12% 6% 3 3 3 4 5% 13%	3070
	21st to end	Day	24% 24% 6% 15% 6% 4 4 2 3 4 9%	4139
January	1st to 10th	Night	14% 20% 9% 25% 5% 4 3 3 3 4 10%	7635
	11th to 20th	Night	10% 18% 10% 20% 10% 6% 6% 3 4 3 10%	7680
	21st to end	Night	16% 17% 8% 13% 7% 6% 5% 3 4 5% 17%	8401
February	1st to 10th	Night	18% 16% 5% 14% 8% 5% 4 3 4 5% 19%	2730
	11th to 20th	Night	15% 14% 7% 15% 8% 5% 4 3 4 5% 19%	2631
	21st to end	Night	19% 13% 5% 12% 6% 5% 5% 3 4 4 23%	2076
March	1st to 10th	Night	19% 14% 5% 9% 5% 4 3 3 4 5% 30%	5102
	11th to 20th	Night	13% 10% 6% 8% 5% 4 4 3 5% 6% 37%	5090
	21st to end	Night	18% 12% 5% 9% 5% 4 4 3 4 5% 32%	5588
April	1st to 10th	Night	18% 15% 4 8% 5% 4 4 3 4 5% 30%	2247
	11th to 20th	Night	16% 10% 2 8% 5% 5% 5% 4 6% 6% 33%	1945
	21st to end	Night	14% 10% 3 7% 5% 4 4 4 5% 7% 36%	1890
May	1st to 10th	Night	24% 9% 3 7% 5% 4 5% 4 5% 5% 30%	5237
	11th to 20th	Night	17% 10% 3 6% 4 4 4 3 6% 7% 38%	5234
	21st to end	Night	20% 7% 2 5% 4 4 4 3 5% 8% 38%	5446
June	1st to 10th	Night	10% 7% 3 6% 5% 5% 5% 4 6% 7% 43%	1680
	11th to 20th	Night	10% 5% 2 8% 4 5% 5% 5% 6% 7% 42%	1640
	21st to end	Night	11% 5% 2 5% 4 5% 5% 4 6% 10% 42%	1600
July	1st to 10th	Night	9% 6% 2 6% 4 5% 4 4 5% 10% 45%	3910
	11th to 20th	Night	10% 6% 2 6% 4 5% 5% 4 6% 9% 44%	4057
	21st to end	Night	8% 6% 2 6% 4 4 4 4 5% 8% 48%	4427
August	1st to 10th	Night	12% 8% 3 7% 4 4 5% 4 6% 7% 41%	2915
	11th to 20th	Night	14% 8% 2 7% 4 4 4 3 4 7% 44%	2875
	21st to end	Night	8% 5% 2 6% 5% 5% 5% 4 7% 7% 44%	3289
September	1st to 10th	Night	12% 6% 2 6% 4 4 4 4 6% 7% 47%	2070
	11th to 20th	Night	11% 4 1 5% 4 4 4 3 5% 6% 53%	2200
	21st to end	Night	18% 7% 2 6% 5% 5% 4 3 5% 5% 39%	2200
October	1st to 10th	Night	14% 6% 3 5% 4 4 4 3 6% 7% 45%	2352
	11th to 20th	Night	18% 9% 3 7% 5% 4 4 4 5% 6% 35%	2400
	21st to end	Night	24% 10% 3 6% 5% 4 4 3 5% 6% 31%	2640
November	1st to 10th	Night	13% 10% 3 7% 5% 4 4 3 5% 6% 38%	2647
	11th to 20th	Night	15% 19% 4 9% 5% 4 4 3 5% 6% 26%	2809
	21st to end	Night	18% 19% 5% 8% 5% 4 5% 3 5% 6% 21%	2940
December	1st to 10th	Night	14% 19% 8% 13% 7% 6% 5% 3 5% 5% 16%	4720
	11th to 20th	Night	19% 21% 9% 12% 5% 3 3 3 3 4 17%	5345
	21st to end	Night	23% 22% 7% 12% 5% 4 4 3 4 4 12%	7042

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	80% 3 8% 6% 2 1	5259
	11th to 20th	Day	81% 3 6% 7% 3	5280
	21st to end	Day	78% 3 6% 10% 3	5780
February	1st to 10th	Day	68% 4 9% 13% 6%	1890
	11th to 20th	Day	69% 4 9% 13% 6%	1880
	21st to end	Day	64% 4 11% 13% 6% 2	1730
March	1st to 10th	Day	58% 5% 11% 20% 6%	4969
	11th to 20th	Day	52% 5% 14% 22% 6% 2	5090
	21st to end	Day	58% 4 8% 17% 12% 1	5586
April	1st to 10th	Day	53% 6% 12% 16% 12% 1	2373
	11th to 20th	Day	53% 6% 10% 17% 12% 2	2641
	21st to end	Day	52% 4 10% 21% 11% 2	2730
May	1st to 10th	Day	55% 6% 9% 19% 9% 3	7651
	11th to 20th	Day	49% 6% 10% 22% 11% 1	7630
	21st to end	Day	47% 6% 9% 17% 18% 3	8705
June	1st to 10th	Day	43% 7% 10% 25% 14% 1	2940
	11th to 20th	Day	43% 8% 13% 20% 14% 1	2870
	21st to end	Day	38% 8% 13% 24% 16% 2	2800
July	1st to 10th	Day	37% 6% 12% 27% 16% 2	5977
	11th to 20th	Day	40% 7% 13% 24% 15% 1	5831
	21st to end	Day	38% 7% 12% 22% 20% 1	6240
August	1st to 10th	Day	44% 8% 14% 23% 11%	4221
	11th to 20th	Day	42% 9% 11% 29% 9% 1	4213
	21st to end	Day	38% 7% 14% 28% 11% 2	4562
September	1st to 10th	Day	40% 6% 14% 21% 15% 3	2327
	11th to 20th	Day	36% 7% 13% 26% 16% 1	2200
	21st to end	Day	48% 5% 10% 23% 13% 1	2200
October	1st to 10th	Day	34% 5% 13% 27% 20% 1	3333
	11th to 20th	Day	48% 4 10% 20% 15% 3	3240
	21st to end	Day	45% 4 14% 23% 14% 1	3538
November	1st to 10th	Day	48% 5% 12% 21% 13% 1	1867
	11th to 20th	Day	60% 5% 11% 15% 7% 2	1807
	21st to end	Day	68% 5% 9% 12% 6%	1680
December	1st to 10th	Day	73% 4 11% 10% 2	2680
	11th to 20th	Day	74% 5% 7% 12% 2	3066
	21st to end	Day	82% 3 7% 6% 1	4139
January	1st to 10th	Night	80% 3 6% 8% 3	7636
	11th to 20th	Night	79% 4 7% 7% 3	7680
	21st to end	Night	71% 3 8% 13% 5%	8401
February	1st to 10th	Night	68% 5% 8% 14% 5%	2730
	11th to 20th	Night	68% 4 9% 14% 5%	2633
	21st to end	Night	64% 5% 8% 14% 8% 1	2076
March	1st to 10th	Night	57% 4 12% 18% 9%	5102
	11th to 20th	Night	48% 4 14% 23% 10% 1	5090
	21st to end	Night	55% 4 10% 17% 13% 1	5588
April	1st to 10th	Night	56% 5% 11% 15% 12% 2	2247
	11th to 20th	Night	50% 6% 11% 19% 13% 2	1945
	21st to end	Night	47% 5% 11% 21% 13% 3	1890
May	1st to 10th	Night	55% 5% 8% 16% 11% 4	5264
	11th to 20th	Night	45% 6% 10% 25% 13% 1	5235
	21st to end	Night	45% 5% 11% 22% 15% 2	5453
June	1st to 10th	Night	39% 9% 10% 23% 17% 3	1680
	11th to 20th	Night	38% 7% 13% 22% 17% 2	1640
	21st to end	Night	36% 10% 12% 24% 18% 1	1600
July	1st to 10th	Night	36% 5% 12% 25% 18% 3	3867
	11th to 20th	Night	37% 7% 13% 27% 15% 2	4006
	21st to end	Night	34% 6% 12% 20% 27% 2	4297
August	1st to 10th	Night	41% 7% 12% 24% 14% 1	2904
	11th to 20th	Night	41% 7% 10% 30% 12% 1	2902
	21st to end	Night	36% 7% 12% 29% 14% 2	3289
September	1st to 10th	Night	36% 6% 12% 27% 16% 3	2070
	11th to 20th	Night	30% 6% 14% 27% 21% 2	2200
	21st to end	Night	46% 6% 10% 20% 17% 1	2200
October	1st to 10th	Night	34% 5% 9% 27% 23% 1	3846
	11th to 20th	Night	43% 5% 11% 21% 17% 3	3899
	21st to end	Night	41% 5% 13% 25% 15% 1	4252
November	1st to 10th	Night	44% 6% 13% 22% 13% 2	2647
	11th to 20th	Night	59% 5% 11% 16% 7% 3	2809
	21st to end	Night	64% 6% 11% 15% 4	2940
December	1st to 10th	Night	69% 5% 12% 10% 3	4720
	11th to 20th	Night	73% 3 9% 13% 2	5348
	21st to end	Night	76% 5% 9% 9% 1	7042

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% 31% 7% 3	330
	11th to 20th	Day	36% 32% 24% 6% 2	330
	21st to end	Day	34% 31% 25% 7% 1	363
February	1st to 10th	Day	35% 25% 33% 7% 1	330
	11th to 20th	Day	37% 29% 28% 5%	330
	21st to end	Day	35% 32% 29% 4	273
March	1st to 10th	Day	29% 26% 30% 12% 3	501
	11th to 20th	Day	32% 23% 31% 11% 3 1	540
	21st to end	Day	34% 25% 25% 12% 3	594
April	1st to 10th	Day	30% 24% 28% 12% 5% 1	540
	11th to 20th	Day	31% 20% 26% 14% 7% 2	532
	21st to end	Day	29% 18% 30% 16% 5% 1	540
May	1st to 10th	Day	29% 23% 28% 14% 4 2	543
	11th to 20th	Day	25% 14% 31% 20% 7% 3	567
	21st to end	Day	18% 13% 29% 24% 12% 4	617
June	1st to 10th	Day	15% 16% 36% 22% 10% 2	570
	11th to 20th	Day	19% 15% 28% 25% 11% 3	550
	21st to end	Day	14% 12% 33% 25% 12% 4	530
July	1st to 10th	Day	12% 7% 25% 30% 20% 7%	525
	11th to 20th	Day	12% 10% 29% 27% 16% 6%	524
	21st to end	Day	10% 8% 31% 28% 16% 7%	576
August	1st to 10th	Day	12% 9% 22% 30% 20% 7%	526
	11th to 20th	Day	14% 9% 28% 25% 15% 9%	519
	21st to end	Day	11% 8% 26% 29% 19% 8%	583
September	1st to 10th	Day	14% 11% 22% 25% 20% 8%	530
	11th to 20th	Day	10% 5% 20% 30% 23% 12%	530
	21st to end	Day	24% 12% 26% 20% 13% 5%	530
October	1st to 10th	Day	14% 13% 29% 21% 19% 4	530
	11th to 20th	Day	24% 19% 33% 17% 5% 2	530
	21st to end	Day	31% 20% 29% 17% 3	583
November	1st to 10th	Day	28% 21% 28% 14% 7% 1	345
	11th to 20th	Day	36% 20% 29% 12% 4	286
	21st to end	Day	34% 20% 39% 7%	220
December	1st to 10th	Day	30% 27% 28% 11% 2 1	220
	11th to 20th	Day	35% 26% 29% 8% 2	220
	21st to end	Day	38% 26% 26% 10%	263
January	1st to 10th	Night	30% 25% 31% 12% 3	840
	11th to 20th	Night	32% 25% 28% 12% 2	840
	21st to end	Night	28% 25% 29% 16% 2	924
February	1st to 10th	Night	31% 20% 30% 18% 1	840
	11th to 20th	Night	30% 22% 32% 15% 1	823
	21st to end	Night	32% 24% 30% 13% 2	692
March	1st to 10th	Night	26% 21% 31% 19% 3	840
	11th to 20th	Night	28% 19% 29% 18% 5% 1	840
	21st to end	Night	26% 19% 29% 20% 5%	924
April	1st to 10th	Night	28% 15% 33% 19% 5%	840
	11th to 20th	Night	24% 15% 34% 20% 7% 1	701
	21st to end	Night	19% 14% 34% 27% 6%	630
May	1st to 10th	Night	24% 11% 27% 28% 9%	630
	11th to 20th	Night	18% 11% 29% 31% 10% 2	621
	21st to end	Night	15% 5% 28% 34% 17% 1	573
June	1st to 10th	Night	11% 6% 32% 38% 12% 1	420
	11th to 20th	Night	14% 5% 28% 39% 13%	410
	21st to end	Night	10% 8% 28% 35% 18% 1	400
July	1st to 10th	Night	8% 3 20% 39% 27% 4	515
	11th to 20th	Night	10% 3 22% 36% 25% 3	582
	21st to end	Night	10% 4 18% 41% 25% 2	657
August	1st to 10th	Night	9% 4 19% 40% 27% 2	597
	11th to 20th	Night	11% 5% 16% 35% 30% 3	594
	21st to end	Night	11% 4 21% 33% 28% 3	700
September	1st to 10th	Night	15% 6% 19% 31% 26% 3	800
	11th to 20th	Night	12% 3 17% 36% 28% 4	800
	21st to end	Night	19% 9% 23% 28% 17% 4	800
October	1st to 10th	Night	18% 10% 26% 25% 20% 2	800
	11th to 20th	Night	23% 15% 29% 24% 8% 1	800
	21st to end	Night	29% 15% 30% 22% 4	880
November	1st to 10th	Night	21% 17% 27% 25% 9% 1	820
	11th to 20th	Night	29% 20% 27% 17% 5% 1	840
	21st to end	Night	33% 18% 30% 14% 4	840
December	1st to 10th	Night	33% 21% 28% 14% 4	840
	11th to 20th	Night	30% 25% 28% 15% 2	840
	21st to end	Night	33% 19% 32% 15% 1	924

Page generated at 2026-06-13 02:31:45. Version ac07

Copyright © 2026 Attilla Danko.