Rodney
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rodney clear sky chart from 2005-11-06 to 2026-05-02.

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	14% 9% 4 9% 5% 5% 5% 4 6% 7% 33%	132100
	Night	14% 10% 4 8% 5% 4 5% 4 5% 7% 34%	130310
Transparency	Day	31% 39% 9% 13% 7% 1	135700
	Night	32% 37% 8% 13% 8% 1	134782
Seeing	Day	16% 7% 22% 31% 20% 5%	16936
	Night	19% 8% 25% 30% 15% 3	26270

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	14% 13% 6% 16% 7% 5% 4 3 4 6% 22%	4839
	11th to 20th	Day	12% 18% 9% 17% 7% 7% 5% 4 5% 5% 13%	5280
	21st to end	Day	17% 15% 6% 12% 7% 5% 5% 4 4 6% 19%	5780
February	1st to 10th	Day	15% 15% 4 14% 7% 5% 4 4 4 5% 22%	1890
	11th to 20th	Day	15% 12% 5% 13% 7% 5% 4 4 5% 7% 23%	1880
	21st to end	Day	16% 13% 6% 11% 6% 6% 5% 4 5% 6% 24%	1730
March	1st to 10th	Day	17% 10% 5% 12% 6% 5% 4 3 5% 6% 27%	4880
	11th to 20th	Day	12% 11% 4 10% 5% 5% 5% 4 5% 7% 33%	5090
	21st to end	Day	18% 13% 4 9% 5% 5% 4 3 5% 5% 29%	5586
April	1st to 10th	Day	16% 11% 4 9% 5% 4 4 4 5% 7% 30%	2365
	11th to 20th	Day	17% 10% 3 8% 4 4 4 4 6% 7% 33%	2702
	21st to end	Day	17% 10% 3 7% 5% 4 4 4 5% 6% 34%	2730
May	1st to 10th	Day	19% 10% 3 7% 4 5% 4 3 5% 6% 33%	5875
	11th to 20th	Day	16% 8% 2 7% 4 4 5% 4 5% 9% 35%	5861
	21st to end	Day	15% 7% 2 7% 4 4 4 4 6% 8% 39%	6766
June	1st to 10th	Day	11% 6% 2 7% 6% 4 5% 4 6% 9% 40%	2800
	11th to 20th	Day	9% 6% 2 6% 5% 5% 5% 5% 7% 9% 40%	2985
	21st to end	Day	10% 5% 2 6% 4 4 5% 4 8% 10% 42%	3000
July	1st to 10th	Day	9% 5% 2 6% 4 5% 5% 4 7% 10% 44%	6622
	11th to 20th	Day	8% 5% 2 6% 4 4 4 4 6% 9% 46%	6039
	21st to end	Day	8% 5% 2 6% 4 5% 5% 4 6% 8% 46%	6424
August	1st to 10th	Day	14% 5% 2 5% 4 4 4 4 6% 10% 41%	4234
	11th to 20th	Day	8% 6% 2 6% 4 5% 7% 6% 8% 10% 38%	4174
	21st to end	Day	9% 6% 2 6% 4 5% 5% 4 6% 9% 44%	4642
September	1st to 10th	Day	9% 6% 2 6% 4 4 5% 5% 7% 8% 44%	2305
	11th to 20th	Day	9% 5% 2 5% 4 4 4 4 5% 9% 50%	2200
	21st to end	Day	18% 6% 2 5% 5% 5% 5% 4 6% 7% 38%	2200
October	1st to 10th	Day	13% 6% 3 7% 3 4 5% 3 7% 7% 42%	2065
	11th to 20th	Day	16% 8% 3 7% 5% 5% 5% 5% 6% 6% 34%	2000
	21st to end	Day	20% 9% 3 8% 5% 5% 5% 4 5% 7% 28%	2148
November	1st to 10th	Day	13% 9% 3 7% 5% 5% 5% 4 6% 7% 35%	1852
	11th to 20th	Day	14% 10% 4 9% 6% 5% 5% 4 5% 8% 31%	1785
	21st to end	Day	18% 13% 6% 10% 5% 6% 5% 4 6% 6% 22%	1680
December	1st to 10th	Day	18% 13% 4 9% 5% 4 5% 4 6% 9% 24%	2680
	11th to 20th	Day	22% 16% 6% 9% 6% 4 4 4 6% 6% 18%	3070
	21st to end	Day	26% 19% 7% 13% 5% 4 4 3 4 5% 11%	3941
January	1st to 10th	Night	15% 13% 5% 12% 5% 5% 4 4 5% 6% 26%	8014
	11th to 20th	Night	9% 16% 7% 13% 7% 6% 5% 4 5% 6% 20%	7680
	21st to end	Night	16% 14% 7% 10% 6% 4 4 4 4 5% 26%	8401
February	1st to 10th	Night	16% 15% 4 11% 7% 5% 5% 4 5% 5% 25%	2730
	11th to 20th	Night	16% 13% 5% 8% 5% 4 5% 4 5% 6% 27%	2624
	21st to end	Night	18% 11% 4 9% 6% 4 6% 4 5% 6% 27%	2076
March	1st to 10th	Night	16% 10% 3 9% 5% 5% 5% 4 5% 6% 33%	5178
	11th to 20th	Night	10% 7% 3 7% 5% 5% 6% 4 6% 8% 41%	5090
	21st to end	Night	16% 10% 4 8% 5% 4 4 4 4 5% 37%	5588
April	1st to 10th	Night	17% 12% 4 6% 5% 4 4 4 5% 6% 33%	2258
	11th to 20th	Night	16% 6% 3 7% 6% 4 4 3 6% 8% 36%	1880
	21st to end	Night	15% 8% 2 7% 5% 4 5% 3 5% 7% 38%	1890
May	1st to 10th	Night	21% 9% 3 7% 5% 4 4 3 5% 6% 33%	4042
	11th to 20th	Night	14% 9% 4 8% 5% 5% 5% 4 5% 7% 35%	4032
	21st to end	Night	16% 7% 3 5% 3 4 4 4 5% 7% 42%	4084
June	1st to 10th	Night	11% 5% 2 6% 5% 5% 3 3 6% 9% 45%	1600
	11th to 20th	Night	10% 5% 2 6% 4 4 5% 5% 7% 10% 43%	1410
	21st to end	Night	9% 6% 2 5% 3 4 5% 4 6% 9% 48%	1400
July	1st to 10th	Night	7% 4 2 5% 5% 5% 5% 4 6% 10% 47%	3337
	11th to 20th	Night	8% 4 2 6% 3 4 4 4 7% 9% 50%	3920
	21st to end	Night	7% 4 2 6% 4 4 4 4 6% 7% 52%	4427
August	1st to 10th	Night	11% 5% 2 5% 4 4 4 4 6% 8% 46%	2915
	11th to 20th	Night	8% 5% 2 6% 4 4 4 4 5% 7% 51%	2875
	21st to end	Night	8% 4 2 5% 4 4 4 4 7% 8% 49%	3223
September	1st to 10th	Night	8% 6% 3 6% 4 4 5% 4 5% 6% 49%	2091
	11th to 20th	Night	8% 5% 1 5% 3 3 4 3 4 6% 57%	2200
	21st to end	Night	15% 7% 3 7% 4 4 5% 2 5% 5% 42%	2200
October	1st to 10th	Night	13% 5% 2 6% 4 4 4 3 5% 7% 47%	2335
	11th to 20th	Night	17% 8% 3 7% 4 4 4 4 4 6% 39%	2400
	21st to end	Night	19% 9% 3 8% 5% 5% 4 3 6% 6% 33%	2690
November	1st to 10th	Night	13% 7% 2 6% 5% 4 4 4 5% 8% 41%	2666
	11th to 20th	Night	16% 10% 3 7% 5% 4 5% 5% 5% 7% 33%	2831
	21st to end	Night	21% 11% 3 9% 5% 5% 4 3 5% 7% 27%	2940
December	1st to 10th	Night	15% 13% 5% 11% 6% 5% 5% 5% 6% 7% 23%	4720
	11th to 20th	Night	18% 16% 5% 10% 6% 4 4 3 5% 5% 23%	5345
	21st to end	Night	25% 16% 6% 13% 5% 5% 4 3 4 5% 14%	7218

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	51% 24% 9% 9% 6%	4840
	11th to 20th	Day	60% 25% 6% 4 4	5280
	21st to end	Day	50% 27% 8% 9% 5%	5780
February	1st to 10th	Day	25% 60% 5% 7% 3	1890
	11th to 20th	Day	25% 59% 4 9% 3 1	1889
	21st to end	Day	23% 60% 5% 7% 4 1	1730
March	1st to 10th	Day	42% 30% 11% 13% 4	4880
	11th to 20th	Day	34% 31% 14% 16% 5%	5090
	21st to end	Day	37% 32% 10% 13% 7% 1	5586
April	1st to 10th	Day	24% 60% 5% 7% 3	2365
	11th to 20th	Day	21% 60% 5% 8% 6% 1	2702
	21st to end	Day	19% 60% 6% 9% 5% 1	2730
May	1st to 10th	Day	37% 31% 10% 12% 8% 3	5910
	11th to 20th	Day	34% 33% 12% 16% 5% 1	5865
	21st to end	Day	32% 31% 8% 13% 11% 5%	6781
June	1st to 10th	Day	15% 63% 4 11% 6% 1	2800
	11th to 20th	Day	17% 63% 6% 7% 6% 1	2985
	21st to end	Day	12% 62% 7% 11% 8%	3000
July	1st to 10th	Day	25% 28% 11% 23% 12% 2	6552
	11th to 20th	Day	23% 28% 12% 21% 14% 1	5966
	21st to end	Day	23% 28% 13% 19% 16% 1	6240
August	1st to 10th	Day	25% 38% 11% 15% 11%	4221
	11th to 20th	Day	23% 40% 11% 23% 4	4213
	21st to end	Day	22% 38% 10% 22% 7%	4642
September	1st to 10th	Day	13% 59% 8% 13% 6%	2305
	11th to 20th	Day	13% 57% 6% 15% 9%	2200
	21st to end	Day	19% 58% 6% 11% 7%	2200
October	1st to 10th	Day	18% 38% 11% 19% 15% 1	3364
	11th to 20th	Day	24% 37% 7% 18% 14%	3240
	21st to end	Day	26% 37% 12% 19% 6%	3450
November	1st to 10th	Day	27% 55% 5% 9% 4 1	1852
	11th to 20th	Day	24% 56% 6% 8% 5%	1785
	21st to end	Day	31% 56% 6% 5% 2	1680
December	1st to 10th	Day	39% 39% 10% 9% 3	2680
	11th to 20th	Day	49% 33% 8% 6% 4	3066
	21st to end	Day	57% 29% 7% 5% 1	3941
January	1st to 10th	Night	47% 24% 9% 13% 6% 1	8015
	11th to 20th	Night	53% 24% 9% 8% 5% 1	7680
	21st to end	Night	45% 26% 8% 14% 7%	8401
February	1st to 10th	Night	25% 60% 4 7% 3 1	2730
	11th to 20th	Night	22% 59% 5% 8% 5%	2626
	21st to end	Night	24% 59% 5% 7% 4	2076
March	1st to 10th	Night	38% 29% 11% 13% 7% 1	5178
	11th to 20th	Night	28% 30% 13% 18% 10% 1	5090
	21st to end	Night	35% 30% 9% 13% 14% 1	5588
April	1st to 10th	Night	26% 59% 4 6% 4 1	2258
	11th to 20th	Night	20% 61% 4 8% 6% 1	1880
	21st to end	Night	16% 60% 6% 11% 6% 1	1890
May	1st to 10th	Night	39% 30% 7% 9% 9% 6%	4069
	11th to 20th	Night	36% 32% 8% 17% 6% 1	4033
	21st to end	Night	32% 31% 9% 14% 13% 2	4091
June	1st to 10th	Night	14% 62% 4 12% 7% 2	1600
	11th to 20th	Night	16% 62% 4 12% 5% 1	1410
	21st to end	Night	14% 61% 5% 10% 10%	1400
July	1st to 10th	Night	23% 28% 13% 20% 12% 3	3301
	11th to 20th	Night	23% 28% 11% 22% 15% 1	3873
	21st to end	Night	23% 27% 10% 15% 22% 2	4297
August	1st to 10th	Night	25% 38% 9% 15% 12% 2	2904
	11th to 20th	Night	22% 39% 9% 20% 9%	2902
	21st to end	Night	22% 38% 9% 22% 10%	3223
September	1st to 10th	Night	13% 58% 6% 13% 8% 1	2091
	11th to 20th	Night	12% 58% 5% 14% 11% 1	2200
	21st to end	Night	20% 57% 4 12% 7% 1	2200
October	1st to 10th	Night	14% 37% 5% 23% 21% 1	3816
	11th to 20th	Night	27% 37% 6% 15% 14%	3899
	21st to end	Night	22% 37% 11% 19% 11%	4338
November	1st to 10th	Night	24% 55% 6% 9% 6%	2666
	11th to 20th	Night	22% 56% 5% 10% 6%	2831
	21st to end	Night	29% 56% 6% 6% 3	2940
December	1st to 10th	Night	38% 38% 13% 10% 2	4720
	11th to 20th	Night	44% 34% 8% 10% 4	5348
	21st to end	Night	56% 28% 8% 6% 2	7218

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	23% 12% 33% 23% 7% 2	327
	11th to 20th	Day	20% 17% 35% 21% 5% 1	330
	21st to end	Day	22% 10% 35% 26% 7% 1	363
February	1st to 10th	Day	17% 12% 31% 32% 6% 1	330
	11th to 20th	Day	20% 11% 34% 30% 5% 1	330
	21st to end	Day	20% 14% 36% 25% 5%	273
March	1st to 10th	Day	19% 8% 32% 31% 9%	461
	11th to 20th	Day	17% 10% 32% 32% 7% 1	540
	21st to end	Day	21% 8% 31% 32% 8%	594
April	1st to 10th	Day	17% 6% 32% 34% 10% 1	540
	11th to 20th	Day	22% 7% 27% 28% 12% 4	532
	21st to end	Day	21% 4 24% 35% 15% 1	540
May	1st to 10th	Day	21% 7% 22% 32% 17% 2	507
	11th to 20th	Day	17% 4 18% 32% 24% 4	527
	21st to end	Day	12% 3 16% 34% 28% 8%	573
June	1st to 10th	Day	13% 3 18% 39% 23% 4	530
	11th to 20th	Day	10% 3 17% 37% 30% 3	715
	21st to end	Day	10% 3 15% 39% 29% 5%	730
July	1st to 10th	Day	8% 3 10% 35% 34% 10%	721
	11th to 20th	Day	12% 2 11% 37% 29% 9%	581
	21st to end	Day	8% 1 8% 35% 39% 9%	576
August	1st to 10th	Day	8% 3 9% 32% 33% 14%	526
	11th to 20th	Day	8% 4 11% 30% 35% 12%	519
	21st to end	Day	9% 3 11% 32% 35% 11%	583
September	1st to 10th	Day	11% 4 14% 29% 29% 14%	530
	11th to 20th	Day	8% 3 11% 25% 36% 18%	530
	21st to end	Day	20% 5% 18% 25% 23% 9%	530
October	1st to 10th	Day	14% 5% 23% 25% 25% 9%	530
	11th to 20th	Day	17% 10% 28% 29% 13% 3	530
	21st to end	Day	24% 12% 27% 25% 12%	531
November	1st to 10th	Day	17% 12% 26% 31% 12% 2	330
	11th to 20th	Day	20% 15% 32% 23% 9% 1	275
	21st to end	Day	20% 14% 37% 25% 5%	220
December	1st to 10th	Day	22% 15% 34% 22% 7%	220
	11th to 20th	Day	28% 19% 30% 19% 4	220
	21st to end	Day	28% 15% 30% 24% 4	242
January	1st to 10th	Night	25% 14% 35% 19% 6% 1	975
	11th to 20th	Night	28% 15% 30% 22% 5%	840
	21st to end	Night	20% 9% 36% 28% 7%	924
February	1st to 10th	Night	24% 9% 32% 28% 6%	840
	11th to 20th	Night	23% 8% 32% 30% 6%	823
	21st to end	Night	24% 9% 37% 27% 4	692
March	1st to 10th	Night	20% 6% 33% 33% 8%	840
	11th to 20th	Night	18% 8% 34% 29% 10% 1	840
	21st to end	Night	21% 7% 28% 32% 10% 2	924
April	1st to 10th	Night	21% 9% 28% 34% 7% 1	840
	11th to 20th	Night	18% 4 30% 33% 12% 2	636
	21st to end	Night	18% 4 26% 39% 12% 1	630
May	1st to 10th	Night	19% 2 23% 35% 18% 3	603
	11th to 20th	Night	16% 2 21% 35% 22% 4	591
	21st to end	Night	13% 2 12% 40% 28% 5%	507
June	1st to 10th	Night	13% 3 18% 38% 25% 3	400
	11th to 20th	Night	12% 2 14% 42% 28% 3	400
	21st to end	Night	9% 2 17% 40% 30% 3	400
July	1st to 10th	Night	6% 3 9% 38% 37% 7%	462
	11th to 20th	Night	10% 3 12% 36% 32% 7%	582
	21st to end	Night	9% 1 11% 38% 36% 4	657
August	1st to 10th	Night	9% 2 10% 37% 35% 8%	597
	11th to 20th	Night	7% 2 12% 33% 39% 8%	594
	21st to end	Night	11% 3 13% 35% 31% 7%	660
September	1st to 10th	Night	10% 4 16% 29% 30% 11%	800
	11th to 20th	Night	9% 5% 11% 28% 35% 11%	800
	21st to end	Night	17% 6% 17% 31% 22% 7%	800
October	1st to 10th	Night	16% 5% 22% 29% 21% 7%	800
	11th to 20th	Night	22% 9% 27% 27% 13% 3	800
	21st to end	Night	25% 12% 26% 30% 8%	880
November	1st to 10th	Night	17% 12% 28% 29% 13% 2	820
	11th to 20th	Night	22% 15% 32% 22% 7% 1	840
	21st to end	Night	28% 12% 29% 23% 7%	840
December	1st to 10th	Night	27% 15% 32% 19% 6% 1	840
	11th to 20th	Night	24% 16% 35% 20% 5%	840
	21st to end	Night	31% 11% 30% 25% 3	953

Page generated at 2026-04-29 02:21:44. Version ac07

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