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 2024-08-15.

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 8% 5% 5% 5% 4 6% 7% 33%	95676
	Night	15% 10% 4 8% 5% 4 4 4 5% 7% 35%	92927
Transparency	Day	24% 52% 7% 10% 5% 1	95440
	Night	26% 52% 6% 9% 6% 1	92769
Seeing	Day	16% 7% 22% 31% 20% 5%	14751
	Night	19% 8% 25% 30% 16% 3	23981

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% 16% 7% 14% 6% 5% 4 4 4 6% 17%	2597
	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	9% 4 2 6% 5% 5% 5% 5% 8% 11% 41%	2457
	11th to 20th	Day	8% 5% 2 6% 5% 5% 7% 6% 7% 10% 39%	2357
	21st to end	Day	10% 7% 2 6% 4 5% 5% 4 6% 8% 43%	2556
September	1st to 10th	Day	10% 6% 2 7% 4 5% 5% 5% 7% 8% 41%	2075
	11th to 20th	Day	9% 6% 2 5% 4 4 4 4 6% 9% 47%	1980
	21st to end	Day	18% 6% 2 5% 4 5% 5% 3 6% 7% 38%	1980
October	1st to 10th	Day	14% 6% 3 7% 3 4 5% 3 6% 7% 40%	1859
	11th to 20th	Day	17% 9% 3 7% 6% 5% 5% 5% 6% 6% 32%	1800
	21st to end	Day	21% 10% 3 9% 5% 5% 5% 4 5% 6% 27%	1934
November	1st to 10th	Day	13% 9% 3 7% 5% 5% 5% 4 6% 8% 35%	1672
	11th to 20th	Day	14% 10% 4 9% 6% 5% 5% 3 6% 8% 31%	1615
	21st to end	Day	19% 12% 5% 9% 5% 5% 5% 4 6% 6% 23%	1520
December	1st to 10th	Day	17% 16% 5% 10% 6% 4 5% 4 6% 7% 22%	1520
	11th to 20th	Day	18% 14% 6% 10% 6% 4 4 5% 6% 6% 20%	1910
	21st to end	Day	28% 19% 7% 11% 5% 4 4 3 4 5% 11%	2706
January	1st to 10th	Night	17% 14% 6% 11% 5% 5% 4 4 5% 6% 22%	4322
	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	7% 4 2 5% 5% 4 5% 5% 6% 10% 48%	1701
	11th to 20th	Night	6% 4 2 6% 4 5% 5% 4 6% 8% 51%	1643
	21st to end	Night	9% 4 2 5% 4 4 5% 3 7% 8% 50%	1782
September	1st to 10th	Night	9% 6% 3 7% 4 5% 5% 4 5% 6% 47%	1881
	11th to 20th	Night	9% 5% 1 6% 4 4 4 3 4 6% 54%	1980
	21st to end	Night	14% 7% 3 6% 4 4 5% 2 5% 6% 43%	1980
October	1st to 10th	Night	13% 6% 2 6% 4 4 4 3 5% 7% 44%	2101
	11th to 20th	Night	17% 8% 3 7% 4 4 4 4 4 7% 38%	2160
	21st to end	Night	21% 9% 3 8% 5% 4 5% 3 6% 6% 30%	2420
November	1st to 10th	Night	13% 7% 2 6% 5% 3 4 4 6% 8% 42%	2406
	11th to 20th	Night	16% 10% 3 7% 5% 4 5% 4 5% 7% 33%	2561
	21st to end	Night	21% 11% 3 8% 5% 5% 4 3 5% 7% 28%	2660
December	1st to 10th	Night	18% 15% 5% 9% 6% 4 5% 3 6% 7% 22%	2660
	11th to 20th	Night	16% 15% 5% 10% 5% 4 4 4 6% 5% 25%	3285
	21st to end	Night	27% 17% 6% 11% 5% 5% 4 3 3 4 14%	4923

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	45% 42% 5% 5% 2	2598
	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	13% 62% 7% 11% 6%	2444
	11th to 20th	Day	14% 65% 7% 12% 2	2357
	21st to end	Day	13% 64% 7% 9% 6% 1	2556
September	1st to 10th	Day	13% 65% 8% 10% 5%	2075
	11th to 20th	Day	13% 64% 5% 12% 7%	1980
	21st to end	Day	15% 63% 5% 11% 6%	1980
October	1st to 10th	Day	17% 63% 5% 9% 6%	1859
	11th to 20th	Day	18% 65% 5% 8% 4	1800
	21st to end	Day	23% 63% 5% 7% 3	1934
November	1st to 10th	Day	24% 60% 4 7% 4 1	1672
	11th to 20th	Day	21% 61% 6% 7% 4	1615
	21st to end	Day	27% 62% 5% 4 2	1520
December	1st to 10th	Day	27% 63% 3 5% 2	1520
	11th to 20th	Day	34% 50% 7% 6% 3	1906
	21st to end	Day	50% 40% 6% 4 1	2706
January	1st to 10th	Night	40% 41% 7% 8% 3	4322
	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	11% 61% 7% 13% 7% 1	1690
	11th to 20th	Night	12% 64% 6% 14% 4	1643
	21st to end	Night	13% 65% 6% 10% 6%	1782
September	1st to 10th	Night	13% 64% 6% 10% 7% 1	1881
	11th to 20th	Night	12% 64% 4 10% 9% 1	1980
	21st to end	Night	16% 63% 3 11% 6%	1980
October	1st to 10th	Night	15% 64% 5% 9% 7%	2101
	11th to 20th	Night	17% 64% 4 8% 6%	2160
	21st to end	Night	22% 63% 3 7% 5%	2420
November	1st to 10th	Night	22% 61% 5% 7% 5%	2406
	11th to 20th	Night	19% 62% 4 10% 5%	2561
	21st to end	Night	24% 62% 6% 5% 3	2660
December	1st to 10th	Night	26% 62% 5% 6% 2	2660
	11th to 20th	Night	30% 51% 7% 8% 3	3288
	21st to end	Night	49% 39% 6% 4 1	4923

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	26% 14% 30% 19% 9% 2	267
	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% 30% 35% 12%	456
	21st to end	Day	9% 2 13% 33% 32% 11%	495
September	1st to 10th	Day	11% 3 13% 31% 29% 12%	450
	11th to 20th	Day	9% 3 13% 27% 34% 15%	450
	21st to end	Day	19% 5% 20% 25% 22% 9%	450
October	1st to 10th	Day	16% 5% 24% 24% 24% 8%	450
	11th to 20th	Day	17% 11% 30% 28% 11% 2	450
	21st to end	Day	26% 13% 26% 26% 9%	449
November	1st to 10th	Day	15% 12% 27% 30% 13% 3	270
	11th to 20th	Day	21% 15% 30% 24% 9% 1	225
	21st to end	Day	21% 13% 36% 26% 3	180
December	1st to 10th	Day	22% 16% 34% 21% 7%	180
	11th to 20th	Day	28% 20% 29% 19% 3	180
	21st to end	Day	26% 17% 31% 22% 4	198
January	1st to 10th	Night	25% 14% 35% 17% 7% 1	883
	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 11% 33% 39% 7%	549
	21st to end	Night	12% 3 14% 34% 30% 7%	594
September	1st to 10th	Night	11% 4 15% 30% 29% 10%	720
	11th to 20th	Night	10% 6% 13% 30% 33% 8%	720
	21st to end	Night	17% 5% 18% 31% 22% 7%	720
October	1st to 10th	Night	17% 5% 22% 29% 20% 6%	720
	11th to 20th	Night	22% 9% 27% 27% 13% 2	720
	21st to end	Night	27% 13% 26% 28% 6%	792
November	1st to 10th	Night	16% 11% 27% 29% 14% 2	740
	11th to 20th	Night	23% 14% 33% 21% 7% 2	760
	21st to end	Night	28% 13% 28% 24% 7%	760
December	1st to 10th	Night	27% 15% 32% 19% 6% 1	760
	11th to 20th	Night	25% 16% 34% 21% 5%	760
	21st to end	Night	31% 11% 31% 24% 3	862

Page generated at 2024-08-12 09:52:50. Version ac07

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