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 2025-01-07.

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% 3 8% 5% 5% 5% 4 6% 8% 33%	105211
	Night	15% 10% 4 8% 5% 4 4 4 5% 7% 34%	103702
Transparency	Day	27% 47% 8% 12% 6% 1	108855
	Night	28% 45% 7% 11% 7% 1	108199
Seeing	Day	16% 7% 22% 31% 20% 5%	15214
	Night	19% 8% 25% 30% 16% 3	24550

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% 15% 7% 15% 6% 5% 4 4 4 6% 17%	2645
	11th to 20th	Day	13% 18% 8% 15% 7% 7% 5% 4 5% 5% 13%	2840
	21st to end	Day	25% 19% 8% 11% 6% 3 4 3 3 4 14%	3124
February	1st to 10th	Day	15% 15% 5% 13% 7% 6% 4 4 5% 5% 21%	1710
	11th to 20th	Day	15% 12% 5% 12% 7% 5% 4 4 5% 7% 24%	1696
	21st to end	Day	17% 12% 5% 10% 6% 5% 5% 4 5% 6% 25%	1570
March	1st to 10th	Day	20% 11% 4 10% 6% 5% 4 3 5% 6% 27%	3330
	11th to 20th	Day	12% 12% 5% 9% 6% 5% 4 4 5% 7% 31%	3480
	21st to end	Day	17% 12% 4 8% 5% 5% 4 3 4 5% 33%	3815
April	1st to 10th	Day	15% 11% 4 8% 5% 4 4 4 5% 8% 31%	2140
	11th to 20th	Day	17% 10% 3 8% 4 4 4 4 7% 7% 33%	2442
	21st to end	Day	18% 10% 3 8% 5% 4 4 4 6% 6% 33%	2470
May	1st to 10th	Day	18% 7% 2 7% 5% 5% 5% 4 6% 7% 34%	4082
	11th to 20th	Day	16% 9% 3 7% 4 5% 4 4 5% 9% 33%	4081
	21st to end	Day	10% 5% 2 6% 4 4 4 4 7% 8% 46%	4711
June	1st to 10th	Day	10% 6% 2 7% 6% 4 6% 4 6% 9% 40%	2660
	11th to 20th	Day	9% 6% 2 6% 5% 5% 5% 5% 7% 9% 41%	2836
	21st to end	Day	10% 5% 2 6% 4 4 5% 4 8% 10% 41%	2850
July	1st to 10th	Day	10% 5% 2 6% 4 5% 5% 5% 7% 9% 42%	4618
	11th to 20th	Day	8% 5% 2 5% 4 4 4 5% 7% 10% 46%	4217
	21st to end	Day	8% 4 2 6% 5% 6% 6% 5% 7% 9% 43%	4466
August	1st to 10th	Day	15% 5% 2 6% 4 4 4 4 6% 10% 40%	4104
	11th to 20th	Day	8% 6% 2 6% 4 5% 7% 6% 8% 10% 38%	4044
	21st to end	Day	9% 6% 2 6% 4 5% 5% 4 6% 9% 44%	4500
September	1st to 10th	Day	10% 6% 2 6% 4 5% 5% 5% 7% 8% 43%	2190
	11th to 20th	Day	9% 5% 2 5% 4 4 4 4 6% 9% 48%	2090
	21st to end	Day	18% 6% 2 5% 5% 5% 5% 4 6% 7% 37%	2090
October	1st to 10th	Day	14% 6% 3 7% 3 4 5% 4 7% 7% 41%	1962
	11th to 20th	Day	17% 9% 3 7% 6% 5% 5% 5% 6% 6% 33%	1900
	21st to end	Day	20% 10% 3 8% 5% 5% 5% 4 5% 7% 27%	2041
November	1st to 10th	Day	13% 9% 3 7% 5% 5% 5% 4 6% 7% 35%	1762
	11th to 20th	Day	15% 10% 4 9% 6% 5% 5% 4 6% 8% 30%	1700
	21st to end	Day	19% 13% 5% 10% 5% 6% 5% 4 6% 6% 22%	1600
December	1st to 10th	Day	18% 13% 4 9% 5% 4 5% 4 6% 9% 24%	2600
	11th to 20th	Day	22% 16% 6% 9% 6% 4 4 4 6% 6% 18%	2990
	21st to end	Day	26% 19% 7% 13% 5% 4 4 3 4 5% 11%	3855
January	1st to 10th	Night	17% 13% 6% 11% 5% 5% 4 4 5% 6% 22%	4407
	11th to 20th	Night	14% 17% 7% 14% 6% 5% 5% 3 5% 6% 18%	4120
	21st to end	Night	24% 16% 7% 10% 5% 4 3 3 4 4 17%	4532
February	1st to 10th	Night	17% 15% 4 10% 7% 5% 5% 4 5% 5% 23%	2470
	11th to 20th	Night	16% 13% 5% 8% 6% 4 5% 4 5% 6% 27%	2368
	21st to end	Night	19% 10% 3 9% 6% 4 6% 4 5% 6% 27%	1884
March	1st to 10th	Night	19% 11% 3 8% 5% 5% 4 3 5% 5% 32%	3522
	11th to 20th	Night	10% 7% 3 7% 6% 5% 6% 4 6% 7% 40%	3480
	21st to end	Night	16% 9% 3 7% 4 4 4 3 5% 5% 38%	3817
April	1st to 10th	Night	16% 11% 4 6% 5% 4 4 4 5% 6% 35%	2043
	11th to 20th	Night	17% 6% 3 7% 6% 4 4 3 6% 8% 36%	1699
	21st to end	Night	15% 9% 2 7% 5% 4 5% 4 5% 7% 37%	1710
May	1st to 10th	Night	19% 8% 3 5% 4 4 4 4 5% 7% 36%	2813
	11th to 20th	Night	11% 9% 3 8% 6% 6% 6% 4 6% 7% 33%	2812
	21st to end	Night	11% 5% 2 5% 3 3 4 4 5% 8% 49%	2840
June	1st to 10th	Night	11% 5% 2 6% 5% 5% 3 3 6% 10% 44%	1520
	11th to 20th	Night	9% 5% 2 6% 4 4 5% 5% 6% 10% 44%	1340
	21st to end	Night	9% 6% 2 5% 3 4 5% 4 5% 9% 48%	1330
July	1st to 10th	Night	7% 4 2 4 4 4 4 4 6% 11% 51%	2333
	11th to 20th	Night	8% 4 2 5% 3 4 3 4 6% 8% 53%	2742
	21st to end	Night	6% 4 2 6% 4 4 5% 5% 7% 9% 49%	3087
August	1st to 10th	Night	12% 6% 2 5% 4 4 4 4 6% 8% 45%	2825
	11th to 20th	Night	8% 5% 2 6% 4 4 4 4 5% 7% 51%	2785
	21st to end	Night	9% 4 2 5% 4 5% 5% 3 7% 8% 49%	3124
September	1st to 10th	Night	8% 6% 3 6% 4 4 4 4 5% 6% 49%	1986
	11th to 20th	Night	9% 5% 1 5% 3 3 4 3 4 6% 56%	2090
	21st to end	Night	15% 7% 3 7% 5% 4 5% 2 5% 6% 42%	2090
October	1st to 10th	Night	13% 6% 2 6% 4 4 4 3 5% 7% 45%	2218
	11th to 20th	Night	17% 8% 3 7% 4 4 4 4 4 6% 38%	2280
	21st to end	Night	20% 9% 3 8% 5% 5% 5% 3 6% 6% 31%	2555
November	1st to 10th	Night	13% 7% 2 6% 5% 3 4 4 6% 8% 42%	2536
	11th to 20th	Night	16% 10% 3 7% 5% 4 5% 4 5% 7% 32%	2696
	21st to end	Night	21% 11% 3 9% 5% 5% 4 4 5% 7% 28%	2800
December	1st to 10th	Night	15% 13% 5% 11% 6% 5% 5% 5% 7% 7% 23%	4580
	11th to 20th	Night	18% 17% 5% 10% 6% 4 4 3 5% 5% 22%	5205
	21st to end	Night	25% 16% 6% 13% 5% 5% 4 3 4 5% 14%	7063

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	46% 42% 5% 5% 3	2646
	11th to 20th	Day	50% 40% 6% 3 1	2840
	21st to end	Day	48% 42% 4 4 2	3124
February	1st to 10th	Day	22% 66% 4 5% 2 1	1710
	11th to 20th	Day	20% 64% 3 8% 3 1	1705
	21st to end	Day	18% 66% 5% 7% 4 1	1570
March	1st to 10th	Day	37% 41% 6% 13% 2	3330
	11th to 20th	Day	30% 43% 13% 11% 3	3480
	21st to end	Day	28% 43% 9% 11% 8% 1	3815
April	1st to 10th	Day	20% 66% 5% 6% 3	2140
	11th to 20th	Day	18% 66% 4 7% 5% 1	2442
	21st to end	Day	17% 65% 6% 7% 4 1	2470
May	1st to 10th	Day	28% 42% 11% 12% 6% 2	4120
	11th to 20th	Day	29% 44% 14% 12% 2	4085
	21st to end	Day	21% 42% 7% 11% 13% 6%	4725
June	1st to 10th	Day	14% 66% 4 10% 5%	2660
	11th to 20th	Day	15% 66% 5% 7% 6% 1	2836
	21st to end	Day	12% 64% 6% 10% 7%	2850
July	1st to 10th	Day	24% 38% 9% 18% 9% 2	4548
	11th to 20th	Day	18% 38% 11% 22% 11%	4144
	21st to end	Day	21% 38% 13% 13% 13% 2	4324
August	1st to 10th	Day	25% 39% 10% 15% 10%	4091
	11th to 20th	Day	23% 41% 11% 22% 4	4083
	21st to end	Day	21% 39% 10% 22% 7%	4500
September	1st to 10th	Day	13% 61% 8% 11% 6%	2190
	11th to 20th	Day	13% 60% 6% 12% 9%	2090
	21st to end	Day	18% 60% 5% 10% 6%	2090
October	1st to 10th	Day	18% 39% 11% 17% 14% 1	3261
	11th to 20th	Day	24% 38% 7% 17% 14%	3140
	21st to end	Day	26% 38% 12% 19% 5%	3343
November	1st to 10th	Day	25% 57% 5% 8% 4 1	1762
	11th to 20th	Day	23% 59% 6% 7% 5%	1700
	21st to end	Day	30% 59% 5% 4 2	1600
December	1st to 10th	Day	38% 40% 10% 9% 3	2600
	11th to 20th	Day	49% 34% 8% 6% 4	2986
	21st to end	Day	57% 30% 7% 5% 1	3855
January	1st to 10th	Night	41% 41% 7% 8% 3	4407
	11th to 20th	Night	46% 41% 9% 3 1	4120
	21st to end	Night	45% 42% 5% 6% 1	4532
February	1st to 10th	Night	23% 66% 3 5% 2	2470
	11th to 20th	Night	18% 65% 4 8% 5%	2370
	21st to end	Night	21% 65% 4 7% 4	1884
March	1st to 10th	Night	34% 41% 9% 12% 3	3522
	11th to 20th	Night	24% 42% 12% 11% 10% 1	3480
	21st to end	Night	26% 42% 7% 12% 11% 1	3817
April	1st to 10th	Night	21% 65% 4 6% 3 1	2043
	11th to 20th	Night	17% 67% 4 7% 5% 1	1699
	21st to end	Night	15% 65% 5% 9% 5% 1	1710
May	1st to 10th	Night	28% 42% 7% 10% 10% 3	2840
	11th to 20th	Night	30% 44% 8% 13% 4	2813
	21st to end	Night	20% 43% 6% 12% 15% 3	2847
June	1st to 10th	Night	12% 65% 3 12% 6% 1	1520
	11th to 20th	Night	15% 65% 4 10% 6% 1	1340
	21st to end	Night	13% 64% 5% 10% 8%	1330
July	1st to 10th	Night	17% 38% 9% 19% 12% 5%	2295
	11th to 20th	Night	17% 37% 11% 21% 14% 1	2692
	21st to end	Night	20% 38% 12% 13% 15% 2	2988
August	1st to 10th	Night	25% 39% 8% 15% 11% 2	2814
	11th to 20th	Night	22% 40% 9% 20% 9%	2812
	21st to end	Night	22% 39% 9% 21% 10%	3124
September	1st to 10th	Night	13% 61% 6% 11% 9% 1	1986
	11th to 20th	Night	12% 61% 4 11% 10% 1	2090
	21st to end	Night	19% 60% 3 11% 6%	2090
October	1st to 10th	Night	13% 38% 5% 22% 21% 1	3699
	11th to 20th	Night	27% 38% 6% 15% 13%	3779
	21st to end	Night	22% 38% 11% 19% 10%	4203
November	1st to 10th	Night	23% 58% 5% 8% 6%	2536
	11th to 20th	Night	21% 59% 4 10% 6%	2696
	21st to end	Night	27% 59% 6% 5% 3	2800
December	1st to 10th	Night	37% 39% 13% 9% 2	4580
	11th to 20th	Night	44% 35% 7% 9% 4	5208
	21st to end	Night	55% 29% 8% 6% 2	7063

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	24% 14% 31% 20% 8% 2	285
	11th to 20th	Day	23% 14% 34% 21% 6% 1	270
	21st to end	Day	24% 11% 32% 26% 6% 1	297
February	1st to 10th	Day	19% 14% 31% 30% 6%	270
	11th to 20th	Day	19% 13% 35% 29% 4	270
	21st to end	Day	22% 14% 36% 23% 5%	225
March	1st to 10th	Day	19% 8% 32% 31% 9% 1	389
	11th to 20th	Day	18% 10% 30% 33% 8% 1	460
	21st to end	Day	22% 7% 31% 32% 8%	506
April	1st to 10th	Day	15% 7% 31% 35% 11% 1	460
	11th to 20th	Day	23% 8% 26% 28% 11% 5%	452
	21st to end	Day	22% 4 25% 35% 13% 1	460
May	1st to 10th	Day	20% 6% 23% 32% 18% 2	463
	11th to 20th	Day	18% 4 18% 32% 24% 5%	487
	21st to end	Day	11% 2 16% 32% 30% 9%	529
June	1st to 10th	Day	12% 3 18% 39% 23% 5%	490
	11th to 20th	Day	10% 3 17% 37% 29% 4	666
	21st to end	Day	11% 3 16% 39% 27% 4	680
July	1st to 10th	Day	8% 3 11% 34% 34% 11%	671
	11th to 20th	Day	12% 2 11% 36% 30% 9%	538
	21st to end	Day	8% 1 8% 36% 38% 9%	532
August	1st to 10th	Day	9% 3 10% 33% 30% 14%	486
	11th to 20th	Day	9% 4 11% 31% 34% 11%	479
	21st to end	Day	9% 2 12% 32% 34% 11%	539
September	1st to 10th	Day	11% 3 14% 30% 29% 13%	490
	11th to 20th	Day	8% 3 12% 26% 35% 17%	490
	21st to end	Day	20% 6% 19% 25% 22% 8%	490
October	1st to 10th	Day	14% 5% 24% 25% 24% 8%	490
	11th to 20th	Day	17% 10% 29% 28% 12% 3	490
	21st to end	Day	25% 12% 26% 25% 11%	490
November	1st to 10th	Day	15% 12% 26% 32% 12% 3	300
	11th to 20th	Day	21% 15% 30% 23% 9% 1	250
	21st to end	Day	21% 14% 37% 26% 4	200
December	1st to 10th	Day	22% 15% 34% 22% 8%	200
	11th to 20th	Day	29% 19% 29% 20% 4	200
	21st to end	Day	26% 15% 30% 24% 4	220
January	1st to 10th	Night	25% 15% 36% 17% 6% 1	914
	11th to 20th	Night	29% 15% 28% 23% 5%	760
	21st to end	Night	21% 8% 34% 28% 8%	836
February	1st to 10th	Night	26% 10% 32% 27% 6%	760
	11th to 20th	Night	23% 8% 32% 30% 6% 1	743
	21st to end	Night	25% 9% 36% 27% 4	628
March	1st to 10th	Night	21% 6% 32% 33% 9%	760
	11th to 20th	Night	18% 8% 33% 29% 11% 1	760
	21st to end	Night	21% 7% 28% 32% 10% 2	836
April	1st to 10th	Night	21% 8% 28% 34% 8% 1	760
	11th to 20th	Night	19% 5% 30% 33% 11% 2	575
	21st to end	Night	18% 4 26% 39% 12% 1	570
May	1st to 10th	Night	19% 2 23% 35% 19% 3	570
	11th to 20th	Night	16% 2 20% 36% 22% 3	561
	21st to end	Night	12% 2 12% 39% 30% 5%	481
June	1st to 10th	Night	13% 3 19% 37% 25% 3	380
	11th to 20th	Night	12% 2 14% 43% 27% 3	380
	21st to end	Night	9% 2 18% 41% 28% 3	380
July	1st to 10th	Night	6% 3 9% 38% 37% 7%	438
	11th to 20th	Night	11% 3 12% 36% 32% 7%	552
	21st to end	Night	9% 1 11% 39% 35% 4	624
August	1st to 10th	Night	9% 2 11% 37% 33% 8%	567
	11th to 20th	Night	7% 2 12% 34% 38% 7%	564
	21st to end	Night	12% 3 14% 34% 31% 7%	627
September	1st to 10th	Night	11% 5% 16% 30% 29% 10%	760
	11th to 20th	Night	10% 6% 12% 29% 34% 10%	760
	21st to end	Night	18% 6% 18% 31% 21% 7%	760
October	1st to 10th	Night	17% 5% 23% 29% 20% 6%	760
	11th to 20th	Night	22% 9% 27% 26% 14% 3	760
	21st to end	Night	25% 12% 25% 29% 8%	836
November	1st to 10th	Night	17% 12% 28% 28% 14% 2	780
	11th to 20th	Night	23% 15% 32% 22% 7% 2	800
	21st to end	Night	28% 13% 29% 24% 7%	800
December	1st to 10th	Night	27% 16% 32% 19% 6% 1	800
	11th to 20th	Night	25% 16% 34% 20% 5%	800
	21st to end	Night	31% 11% 30% 25% 3	908

Page generated at 2025-01-04 03:23:58. Version ac07

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