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 2024-01-22.

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% 8% 4 7% 6% 4 5% 5% 6% 8% 33%	75047
	Night	15% 9% 4 7% 6% 3 5% 5% 5% 7% 35%	74841
Transparency	Day	32% 39% 9% 13% 7% 1	74759
	Night	33% 38% 8% 13% 7% 1	74650
Seeing	Day	16% 7% 22% 31% 20% 5%	13935
	Night	19% 8% 25% 30% 16% 3	23328

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% 13% 6% 10% 7% 5% 6% 4 4 7% 21%	1564
	11th to 20th	Day	17% 15% 8% 12% 9% 4 5% 5% 4 5% 17%	1710
	21st to end	Day	16% 15% 7% 11% 9% 3 5% 6% 5% 6% 18%	1791
February	1st to 10th	Day	17% 14% 5% 11% 9% 4 4 5% 4 5% 21%	1620
	11th to 20th	Day	15% 11% 6% 11% 9% 4 4 5% 5% 7% 23%	1605
	21st to end	Day	18% 11% 6% 9% 7% 4 5% 4 5% 6% 25%	1480
March	1st to 10th	Day	17% 9% 5% 8% 7% 5% 5% 5% 5% 6% 28%	1912
	11th to 20th	Day	15% 11% 5% 8% 6% 4 4 5% 5% 6% 31%	1980
	21st to end	Day	19% 11% 6% 8% 6% 3 5% 4 3 6% 30%	2178
April	1st to 10th	Day	15% 10% 5% 7% 6% 3 4 5% 5% 8% 31%	2026
	11th to 20th	Day	17% 10% 4 7% 5% 3 4 5% 6% 7% 33%	2312
	21st to end	Day	18% 9% 4 7% 6% 3 5% 4 5% 6% 33%	2340
May	1st to 10th	Day	17% 7% 3 6% 7% 5% 4 5% 6% 7% 34%	2340
	11th to 20th	Day	15% 8% 4 6% 5% 4 5% 5% 4 8% 36%	2301
	21st to end	Day	10% 5% 3 6% 5% 3 5% 5% 8% 9% 42%	2655
June	1st to 10th	Day	11% 6% 3 6% 6% 3 5% 5% 5% 9% 41%	2520
	11th to 20th	Day	10% 6% 2 5% 6% 3 5% 6% 7% 9% 41%	2686
	21st to end	Day	10% 4 2 5% 5% 3 5% 5% 8% 10% 43%	2700
July	1st to 10th	Day	8% 5% 2 4 4 3 5% 6% 7% 9% 46%	2628
	11th to 20th	Day	9% 6% 3 5% 5% 3 5% 6% 7% 10% 42%	2395
	21st to end	Day	7% 5% 2 5% 5% 5% 6% 6% 8% 10% 41%	2547
August	1st to 10th	Day	8% 4 3 5% 6% 3 6% 6% 8% 11% 42%	2327
	11th to 20th	Day	8% 5% 3 5% 5% 4 6% 7% 7% 10% 38%	2303
	21st to end	Day	10% 6% 3 6% 5% 3 5% 5% 6% 8% 43%	2556
September	1st to 10th	Day	10% 6% 2 6% 5% 3 6% 6% 7% 8% 41%	2075
	11th to 20th	Day	10% 5% 2 5% 5% 3 4 5% 6% 9% 47%	1980
	21st to end	Day	18% 6% 2 5% 5% 4 5% 5% 6% 8% 39%	1980
October	1st to 10th	Day	14% 6% 3 6% 4 3 5% 5% 6% 7% 40%	1859
	11th to 20th	Day	17% 9% 3 6% 7% 4 5% 6% 6% 6% 32%	1800
	21st to end	Day	21% 9% 3 7% 7% 4 5% 5% 5% 6% 27%	1934
November	1st to 10th	Day	13% 8% 4 6% 6% 4 6% 5% 6% 8% 35%	1672
	11th to 20th	Day	15% 9% 4 8% 7% 3 5% 5% 6% 8% 31%	1615
	21st to end	Day	19% 12% 5% 8% 6% 4 5% 5% 6% 7% 23%	1520
December	1st to 10th	Day	17% 14% 6% 9% 6% 3 5% 5% 5% 8% 22%	1520
	11th to 20th	Day	19% 13% 7% 9% 7% 3 5% 5% 6% 6% 20%	1910
	21st to end	Day	28% 18% 7% 10% 6% 3 4 3 4 5% 11%	2706
January	1st to 10th	Night	19% 10% 6% 9% 7% 4 5% 5% 5% 7% 23%	2581
	11th to 20th	Night	19% 16% 6% 10% 7% 4 4 4 5% 5% 20%	2470
	21st to end	Night	13% 15% 7% 10% 9% 4 5% 5% 5% 6% 22%	2599
February	1st to 10th	Night	18% 14% 5% 9% 8% 3 6% 4 5% 6% 23%	2340
	11th to 20th	Night	17% 12% 6% 7% 7% 3 5% 5% 5% 6% 27%	2240
	21st to end	Night	20% 10% 4 7% 7% 3 6% 4 5% 6% 27%	1776
March	1st to 10th	Night	16% 9% 3 7% 5% 4 6% 5% 5% 6% 33%	2047
	11th to 20th	Night	15% 8% 3 6% 6% 3 5% 4 6% 7% 38%	1980
	21st to end	Night	19% 9% 3 7% 6% 3 4 5% 5% 5% 34%	2178
April	1st to 10th	Night	16% 10% 4 6% 5% 3 4 5% 5% 6% 36%	1936
	11th to 20th	Night	17% 6% 3 7% 7% 3 4 3 6% 7% 37%	1609
	21st to end	Night	15% 8% 3 7% 6% 4 4 4 5% 7% 37%	1620
May	1st to 10th	Night	16% 8% 4 5% 6% 3 5% 6% 6% 8% 34%	1620
	11th to 20th	Night	14% 6% 3 6% 6% 4 6% 5% 5% 7% 39%	1592
	21st to end	Night	10% 5% 2 4 4 3 4 6% 6% 8% 48%	1616
June	1st to 10th	Night	10% 5% 2 5% 5% 3 4 4 6% 10% 46%	1440
	11th to 20th	Night	10% 5% 2 5% 5% 3 5% 6% 6% 10% 44%	1270
	21st to end	Night	9% 6% 2 4 3 2 5% 5% 5% 10% 48%	1260
July	1st to 10th	Night	6% 3 2 4 5% 4 3 4 5% 8% 55%	1327
	11th to 20th	Night	8% 4 2 5% 4 3 4 4 6% 9% 50%	1561
	21st to end	Night	6% 4 2 5% 5% 3 5% 6% 7% 9% 48%	1771
August	1st to 10th	Night	7% 3 1 4 5% 3 5% 7% 6% 10% 49%	1611
	11th to 20th	Night	6% 4 2 4 6% 3 5% 6% 7% 8% 49%	1598
	21st to end	Night	9% 4 2 4 4 3 5% 4 7% 8% 50%	1782
September	1st to 10th	Night	9% 6% 3 6% 5% 3 5% 5% 5% 6% 47%	1881
	11th to 20th	Night	9% 4 2 4 4 3 4 3 4 6% 55%	1980
	21st to end	Night	14% 7% 3 5% 5% 3 5% 3 5% 6% 43%	1980
October	1st to 10th	Night	13% 6% 3 5% 5% 3 4 4 5% 7% 45%	2101
	11th to 20th	Night	17% 7% 3 6% 5% 3 4 5% 4 7% 38%	2160
	21st to end	Night	21% 9% 4 7% 6% 3 5% 4 5% 6% 30%	2420
November	1st to 10th	Night	14% 6% 3 5% 6% 2 4 5% 6% 8% 42%	2406
	11th to 20th	Night	16% 9% 4 6% 6% 3 6% 5% 5% 7% 33%	2561
	21st to end	Night	21% 10% 4 7% 5% 4 4 4 5% 7% 29%	2660
December	1st to 10th	Night	18% 13% 6% 9% 6% 3 5% 4 6% 7% 23%	2660
	11th to 20th	Night	16% 14% 5% 9% 6% 3 4 5% 5% 6% 26%	3285
	21st to end	Night	27% 16% 6% 10% 6% 4 5% 4 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	42% 41% 9% 6% 2	1565
	11th to 20th	Day	46% 40% 7% 5% 2	1710
	21st to end	Day	45% 39% 7% 6% 3	1791
February	1st to 10th	Day	42% 38% 8% 9% 3	1620
	11th to 20th	Day	40% 39% 9% 7% 5%	1614
	21st to end	Day	42% 38% 7% 9% 3 1	1480
March	1st to 10th	Day	35% 38% 9% 13% 4	1912
	11th to 20th	Day	36% 37% 8% 11% 7% 1	1980
	21st to end	Day	37% 38% 8% 13% 4 1	2178
April	1st to 10th	Day	30% 38% 9% 13% 10%	2026
	11th to 20th	Day	32% 38% 8% 12% 9% 1	2312
	21st to end	Day	33% 38% 8% 12% 8% 1	2340
May	1st to 10th	Day	31% 38% 8% 14% 8% 1	2340
	11th to 20th	Day	30% 37% 8% 11% 11% 2	2305
	21st to end	Day	22% 40% 10% 15% 11% 2	2655
June	1st to 10th	Day	25% 39% 9% 16% 8% 2	2520
	11th to 20th	Day	22% 38% 11% 17% 11% 1	2686
	21st to end	Day	23% 40% 10% 17% 10% 1	2700
July	1st to 10th	Day	21% 40% 8% 18% 12% 2	2558
	11th to 20th	Day	23% 40% 9% 16% 11% 1	2322
	21st to end	Day	22% 42% 12% 14% 9% 1	2405
August	1st to 10th	Day	23% 40% 10% 18% 8%	2314
	11th to 20th	Day	22% 39% 11% 16% 10% 2	2303
	21st to end	Day	23% 39% 9% 16% 12% 1	2556
September	1st to 10th	Day	25% 40% 9% 14% 10% 1	2075
	11th to 20th	Day	22% 38% 11% 21% 8%	1980
	21st to end	Day	31% 39% 8% 14% 7% 1	1980
October	1st to 10th	Day	28% 38% 9% 16% 9% 1	1859
	11th to 20th	Day	35% 39% 11% 11% 4 1	1800
	21st to end	Day	37% 40% 9% 9% 5%	1934
November	1st to 10th	Day	26% 43% 10% 14% 6% 1	1672
	11th to 20th	Day	32% 41% 11% 10% 6% 1	1615
	21st to end	Day	38% 41% 8% 10% 2	1520
December	1st to 10th	Day	39% 43% 9% 7% 1	1520
	11th to 20th	Day	45% 34% 11% 8% 3	1906
	21st to end	Day	62% 28% 6% 3	2706
January	1st to 10th	Night	42% 42% 6% 8% 2	2581
	11th to 20th	Night	44% 41% 7% 6% 2	2470
	21st to end	Night	43% 38% 8% 9% 3	2599
February	1st to 10th	Night	41% 38% 8% 9% 3 1	2340
	11th to 20th	Night	41% 38% 7% 9% 4	2242
	21st to end	Night	38% 37% 7% 13% 5% 1	1776
March	1st to 10th	Night	32% 38% 8% 16% 6%	2047
	11th to 20th	Night	30% 37% 8% 14% 8% 1	1980
	21st to end	Night	34% 38% 6% 15% 6% 1	2178
April	1st to 10th	Night	30% 37% 7% 14% 11% 1	1936
	11th to 20th	Night	30% 36% 8% 14% 11% 1	1609
	21st to end	Night	33% 36% 6% 11% 11% 2	1620
May	1st to 10th	Night	32% 38% 7% 12% 9% 3	1620
	11th to 20th	Night	28% 37% 6% 13% 12% 4	1593
	21st to end	Night	21% 40% 9% 16% 13% 2	1617
June	1st to 10th	Night	23% 38% 9% 16% 11% 2	1440
	11th to 20th	Night	21% 39% 8% 15% 15% 2	1270
	21st to end	Night	22% 38% 8% 19% 12% 1	1260
July	1st to 10th	Night	22% 38% 6% 17% 14% 3	1289
	11th to 20th	Night	21% 39% 8% 18% 12% 2	1511
	21st to end	Night	19% 41% 10% 15% 13% 2	1672
August	1st to 10th	Night	22% 40% 9% 21% 8%	1600
	11th to 20th	Night	20% 37% 9% 21% 11% 2	1598
	21st to end	Night	20% 39% 7% 20% 13% 2	1782
September	1st to 10th	Night	25% 39% 7% 17% 10% 2	1881
	11th to 20th	Night	21% 37% 10% 21% 11%	1980
	21st to end	Night	29% 38% 9% 15% 9% 1	1980
October	1st to 10th	Night	27% 37% 8% 15% 13% 1	2101
	11th to 20th	Night	33% 38% 9% 13% 7%	2160
	21st to end	Night	36% 39% 8% 11% 6% 1	2420
November	1st to 10th	Night	23% 41% 8% 18% 9%	2406
	11th to 20th	Night	32% 42% 9% 11% 6% 1	2561
	21st to end	Night	36% 40% 10% 11% 2	2660
December	1st to 10th	Night	41% 42% 8% 8% 1	2660
	11th to 20th	Night	43% 35% 10% 9% 3	3288
	21st to end	Night	61% 27% 7% 3 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% 20% 6% 1	270
	21st to end	Day	22% 12% 34% 25% 6% 1	267
February	1st to 10th	Day	20% 14% 33% 30% 3	240
	11th to 20th	Day	20% 13% 37% 25% 5%	240
	21st to end	Day	23% 13% 38% 22% 4 1	198
March	1st to 10th	Day	18% 9% 33% 31% 8% 1	352
	11th to 20th	Day	18% 9% 30% 33% 8% 1	420
	21st to end	Day	22% 8% 31% 31% 8%	462
April	1st to 10th	Day	15% 6% 32% 34% 11% 1	420
	11th to 20th	Day	23% 7% 25% 28% 11% 5%	412
	21st to end	Day	23% 4 25% 34% 13% 1	420
May	1st to 10th	Day	21% 6% 23% 30% 17% 3	423
	11th to 20th	Day	18% 4 19% 32% 23% 4	447
	21st to end	Day	12% 2 16% 31% 31% 9%	485
June	1st to 10th	Day	12% 4 17% 40% 23% 5%	450
	11th to 20th	Day	10% 3 18% 36% 29% 3	616
	21st to end	Day	10% 3 15% 40% 27% 4	630
July	1st to 10th	Day	8% 3 10% 32% 35% 12%	621
	11th to 20th	Day	12% 2 12% 36% 30% 9%	495
	21st to end	Day	8% 1 9% 38% 36% 8%	488
August	1st to 10th	Day	8% 3 9% 34% 31% 15%	446
	11th to 20th	Day	9% 4 12% 30% 34% 12%	439
	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% 14% 28% 23% 5%	760
	21st to end	Night	20% 9% 35% 28% 8%	800
February	1st to 10th	Night	27% 10% 32% 26% 4	720
	11th to 20th	Night	24% 8% 32% 29% 6% 1	703
	21st to end	Night	25% 9% 36% 27% 3	592
March	1st to 10th	Night	20% 6% 33% 33% 8%	720
	11th to 20th	Night	19% 8% 32% 29% 11% 1	720
	21st to end	Night	22% 6% 27% 32% 11% 2	792
April	1st to 10th	Night	20% 7% 29% 35% 8% 1	720
	11th to 20th	Night	18% 5% 30% 32% 12% 2	545
	21st to end	Night	18% 4 26% 39% 12% 1	540
May	1st to 10th	Night	19% 2 22% 35% 18% 3	540
	11th to 20th	Night	17% 2 21% 36% 21% 3	531
	21st to end	Night	12% 2 12% 39% 30% 5%	456
June	1st to 10th	Night	13% 3 19% 37% 26% 3	360
	11th to 20th	Night	13% 2 14% 43% 26% 3	360
	21st to end	Night	9% 1 18% 41% 29% 3	360
July	1st to 10th	Night	7% 3 9% 36% 37% 8%	414
	11th to 20th	Night	11% 2 12% 36% 32% 7%	522
	21st to end	Night	9% 1 12% 39% 34% 4	591
August	1st to 10th	Night	8% 1 10% 37% 34% 9%	537
	11th to 20th	Night	7% 2 11% 33% 39% 8%	534
	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

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