Elliott Island road
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Elliott Island road clear sky chart from 2005-11-06 to 2024-03-01.

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	13% 5% 2 5% 5% 3 4 4 6% 8% 45%	78518
	Night	15% 6% 3 5% 5% 3 4 4 5% 7% 43%	80893
Transparency	Day	37% 7% 13% 24% 16% 3	78227
	Night	39% 6% 12% 23% 16% 3	80703
Seeing	Day	16% 11% 28% 26% 15% 5%	14147
	Night	17% 10% 28% 31% 14% 2	23723

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	16% 6% 3 4 4 2 3 3 5% 8% 46%	2517
	11th to 20th	Day	16% 7% 2 7% 5% 3 5% 4 5% 6% 41%	2808
	21st to end	Day	16% 9% 3 6% 5% 3 5% 4 4 7% 38%	3124
February	1st to 10th	Day	14% 7% 3 6% 4 3 5% 5% 6% 8% 39%	1710
	11th to 20th	Day	19% 6% 2 4 4 2 4 4 5% 7% 44%	1803
	21st to end	Day	19% 7% 2 5% 4 4 4 4 6% 6% 38%	1570
March	1st to 10th	Day	14% 5% 2 5% 3 3 3 3 5% 6% 50%	1862
	11th to 20th	Day	18% 6% 2 4 4 3 4 4 5% 6% 46%	1980
	21st to end	Day	18% 6% 3 5% 5% 3 4 4 4 6% 42%	2268
April	1st to 10th	Day	11% 6% 3 5% 4 2 4 5% 5% 8% 48%	2160
	11th to 20th	Day	11% 5% 1 4 4 3 5% 4 4 7% 51%	2134
	21st to end	Day	13% 6% 2 5% 4 3 3 5% 5% 8% 46%	2160
May	1st to 10th	Day	13% 5% 2 5% 5% 3 4 5% 6% 9% 44%	2176
	11th to 20th	Day	15% 5% 2 4 5% 3 4 4 6% 8% 44%	2478
	21st to end	Day	11% 4 2 4 5% 2 4 5% 6% 9% 47%	2725
June	1st to 10th	Day	10% 3 1 4 4 3 5% 5% 8% 10% 46%	2520
	11th to 20th	Day	9% 4 2 5% 5% 3 4 5% 6% 10% 47%	2520
	21st to end	Day	8% 3 2 3 5% 3 4 5% 8% 11% 48%	2520
July	1st to 10th	Day	8% 4 3 5% 5% 3 5% 5% 6% 10% 46%	2520
	11th to 20th	Day	5% 3 2 4 4 3 5% 7% 8% 12% 47%	2520
	21st to end	Day	8% 3 2 5% 6% 4 6% 7% 8% 11% 41%	2552
August	1st to 10th	Day	9% 4 2 6% 5% 3 5% 6% 7% 10% 43%	2323
	11th to 20th	Day	10% 5% 2 6% 6% 3 5% 5% 6% 8% 44%	2126
	21st to end	Day	10% 4 2 5% 5% 3 5% 5% 5% 10% 46%	2376
September	1st to 10th	Day	13% 5% 1 4 4 3 4 5% 6% 9% 46%	2160
	11th to 20th	Day	10% 6% 2 5% 4 2 3 4 5% 7% 50%	2160
	21st to end	Day	17% 7% 3 5% 4 3 4 4 5% 6% 41%	1940
October	1st to 10th	Day	14% 5% 2 6% 5% 3 4 4 5% 6% 47%	1800
	11th to 20th	Day	16% 5% 2 4 4 2 3 3 4 6% 52%	1800
	21st to end	Day	14% 5% 2 4 5% 3 3 4 4 8% 47%	1980
November	1st to 10th	Day	12% 5% 2 3 5% 2 3 5% 5% 6% 52%	1694
	11th to 20th	Day	13% 5% 2 4 5% 3 4 4 5% 6% 49%	1710
	21st to end	Day	15% 5% 3 4 5% 2 3 3 4 6% 50%	1620
December	1st to 10th	Day	16% 7% 2 6% 4 3 5% 4 6% 7% 40%	1520
	11th to 20th	Day	15% 9% 3 4 5% 2 3 3 4 5% 48%	1910
	21st to end	Day	15% 7% 2 5% 5% 3 5% 5% 6% 6% 42%	2772
January	1st to 10th	Night	15% 7% 3 4 4 2 4 4 5% 8% 43%	4429
	11th to 20th	Night	16% 7% 3 6% 5% 3 4 3 3 5% 44%	4148
	21st to end	Night	18% 9% 3 6% 4 3 4 3 4 5% 40%	4532
February	1st to 10th	Night	16% 7% 3 4 5% 3 3 4 6% 6% 43%	2470
	11th to 20th	Night	19% 7% 3 4 4 3 3 4 4 8% 41%	2261
	21st to end	Night	18% 8% 2 4 4 2 4 3 5% 7% 44%	1884
March	1st to 10th	Night	15% 5% 2 5% 4 3 4 5% 4 6% 48%	2102
	11th to 20th	Night	18% 6% 2 5% 4 2 4 4 5% 7% 43%	1980
	21st to end	Night	16% 8% 3 6% 4 3 4 3 4 7% 41%	2088
April	1st to 10th	Night	15% 6% 3 6% 5% 3 4 5% 5% 7% 42%	1800
	11th to 20th	Night	12% 6% 3 5% 5% 2 4 4 5% 7% 48%	1775
	21st to end	Night	17% 4 2 4 5% 3 5% 4 6% 6% 44%	1800
May	1st to 10th	Night	15% 5% 2 5% 5% 3 5% 5% 7% 10% 39%	1796
	11th to 20th	Night	15% 5% 2 5% 5% 3 5% 6% 6% 8% 40%	1415
	21st to end	Night	12% 6% 2 6% 6% 3 5% 5% 6% 8% 42%	1550
June	1st to 10th	Night	11% 5% 2 5% 5% 3 5% 6% 6% 8% 44%	1440
	11th to 20th	Night	8% 5% 3 6% 6% 3 5% 5% 7% 10% 42%	1440
	21st to end	Night	9% 4 3 5% 5% 3 6% 6% 7% 10% 41%	1440
July	1st to 10th	Night	10% 6% 2 6% 4 3 5% 5% 7% 10% 43%	1440
	11th to 20th	Night	5% 3 3 5% 5% 3 6% 6% 8% 10% 46%	1440
	21st to end	Night	7% 3 3 6% 5% 4 6% 6% 7% 11% 41%	1762
August	1st to 10th	Night	8% 5% 2 6% 7% 4 5% 6% 7% 10% 41%	1611
	11th to 20th	Night	10% 5% 3 6% 6% 3 5% 6% 7% 9% 39%	1758
	21st to end	Night	9% 5% 3 5% 5% 4 4 6% 6% 9% 44%	1980
September	1st to 10th	Night	13% 6% 2 4 4 3 3 4 5% 7% 48%	1800
	11th to 20th	Night	9% 4 2 5% 4 3 4 4 5% 9% 52%	1800
	21st to end	Night	18% 6% 3 5% 4 4 5% 5% 5% 7% 38%	2017
October	1st to 10th	Night	16% 6% 2 5% 4 3 4 5% 4 7% 44%	2160
	11th to 20th	Night	17% 6% 2 4 4 3 3 3 4 5% 49%	2160
	21st to end	Night	17% 6% 2 5% 4 2 4 4 5% 7% 46%	2376
November	1st to 10th	Night	13% 5% 3 5% 5% 2 4 3 4 6% 52%	2382
	11th to 20th	Night	16% 6% 3 5% 4 2 4 3 4 7% 47%	2470
	21st to end	Night	12% 5% 2 4 4 3 4 4 5% 8% 49%	2558
December	1st to 10th	Night	18% 8% 3 5% 4 2 4 4 5% 7% 39%	2660
	11th to 20th	Night	19% 6% 3 6% 5% 2 3 3 4 6% 43%	3285
	21st to end	Night	15% 8% 2 5% 5% 3 4 5% 6% 8% 39%	4884

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	36% 5% 9% 30% 16% 3	2518
	11th to 20th	Day	43% 4 11% 20% 17% 4	2808
	21st to end	Day	46% 7% 12% 22% 12% 2	3124
February	1st to 10th	Day	42% 6% 12% 25% 13% 2	1710
	11th to 20th	Day	40% 4 10% 24% 18% 4	1812
	21st to end	Day	46% 6% 12% 17% 16% 4	1570
March	1st to 10th	Day	35% 5% 12% 25% 20% 3	1862
	11th to 20th	Day	40% 5% 11% 22% 18% 4	1980
	21st to end	Day	44% 6% 9% 21% 16% 4	2268
April	1st to 10th	Day	34% 6% 12% 23% 18% 6%	2160
	11th to 20th	Day	33% 6% 12% 23% 21% 5%	2134
	21st to end	Day	36% 6% 12% 23% 18% 5%	2160
May	1st to 10th	Day	36% 9% 14% 21% 16% 3	2176
	11th to 20th	Day	37% 8% 16% 22% 14% 3	2482
	21st to end	Day	34% 9% 15% 29% 12% 1	2725
June	1st to 10th	Day	32% 9% 16% 26% 15% 2	2520
	11th to 20th	Day	32% 9% 17% 23% 17% 3	2520
	21st to end	Day	29% 9% 16% 26% 19% 1	2520
July	1st to 10th	Day	33% 9% 16% 23% 17% 2	2450
	11th to 20th	Day	27% 10% 20% 29% 12% 2	2445
	21st to end	Day	33% 11% 17% 22% 15% 2	2409
August	1st to 10th	Day	33% 11% 17% 27% 12% 1	2310
	11th to 20th	Day	37% 10% 15% 22% 15% 1	2126
	21st to end	Day	35% 9% 15% 22% 15% 4	2376
September	1st to 10th	Day	35% 9% 16% 20% 16% 4	2160
	11th to 20th	Day	33% 8% 10% 25% 21% 3	2160
	21st to end	Day	44% 5% 10% 20% 18% 3	1940
October	1st to 10th	Day	40% 5% 10% 24% 18% 3	1800
	11th to 20th	Day	36% 4 8% 28% 21% 3	1800
	21st to end	Day	36% 6% 9% 25% 21% 4	1980
November	1st to 10th	Day	33% 4 11% 29% 19% 4	1694
	11th to 20th	Day	37% 5% 12% 21% 21% 4	1710
	21st to end	Day	38% 3 10% 29% 17% 3	1620
December	1st to 10th	Day	43% 5% 15% 22% 12% 3	1520
	11th to 20th	Day	40% 3 10% 29% 14% 4	1906
	21st to end	Day	40% 8% 14% 26% 12%	2772
January	1st to 10th	Night	40% 4 10% 25% 17% 4	4429
	11th to 20th	Night	43% 4 10% 25% 16% 2	4148
	21st to end	Night	47% 4 8% 25% 15% 2	4532
February	1st to 10th	Night	41% 5% 12% 24% 16% 2	2470
	11th to 20th	Night	43% 5% 8% 20% 20% 5%	2263
	21st to end	Night	41% 5% 9% 23% 18% 4	1884
March	1st to 10th	Night	37% 5% 10% 26% 19% 3	2102
	11th to 20th	Night	41% 5% 10% 23% 18% 3	1980
	21st to end	Night	44% 5% 10% 20% 16% 6%	2088
April	1st to 10th	Night	41% 7% 11% 18% 19% 5%	1800
	11th to 20th	Night	35% 5% 13% 20% 21% 6%	1775
	21st to end	Night	40% 6% 11% 23% 16% 4	1800
May	1st to 10th	Night	39% 8% 13% 22% 14% 3	1796
	11th to 20th	Night	41% 9% 15% 17% 16% 2	1416
	21st to end	Night	40% 8% 15% 23% 13% 1	1551
June	1st to 10th	Night	37% 9% 13% 24% 16% 2	1440
	11th to 20th	Night	36% 9% 15% 24% 14% 2	1440
	21st to end	Night	35% 10% 16% 21% 16% 2	1440
July	1st to 10th	Night	36% 10% 17% 21% 13% 3	1400
	11th to 20th	Night	29% 11% 20% 27% 13% 1	1392
	21st to end	Night	33% 10% 17% 25% 15%	1664
August	1st to 10th	Night	36% 9% 19% 22% 14%	1600
	11th to 20th	Night	38% 10% 17% 22% 13% 1	1758
	21st to end	Night	36% 8% 16% 20% 17% 3	1980
September	1st to 10th	Night	36% 7% 16% 21% 16% 4	1800
	11th to 20th	Night	30% 6% 11% 28% 22% 3	1800
	21st to end	Night	44% 8% 9% 19% 17% 3	2017
October	1st to 10th	Night	41% 6% 9% 24% 18% 3	2160
	11th to 20th	Night	38% 4 9% 25% 21% 3	2160
	21st to end	Night	38% 4 10% 24% 20% 3	2376
November	1st to 10th	Night	36% 4 10% 27% 18% 5%	2382
	11th to 20th	Night	39% 4 10% 21% 20% 6%	2470
	21st to end	Night	34% 5% 10% 27% 20% 4	2558
December	1st to 10th	Night	45% 5% 12% 23% 13% 3	2660
	11th to 20th	Night	43% 3 10% 23% 17% 3	3288
	21st to end	Night	40% 7% 16% 25% 10% 1	4884

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% 23% 32% 15% 7%	180
	11th to 20th	Day	24% 28% 30% 16% 2	261
	21st to end	Day	20% 22% 41% 14% 4	297
February	1st to 10th	Day	21% 20% 40% 13% 4	270
	11th to 20th	Day	27% 19% 37% 13% 3	411
	21st to end	Day	25% 21% 33% 17% 4	382
March	1st to 10th	Day	20% 19% 34% 22% 4	420
	11th to 20th	Day	23% 19% 33% 20% 4 2	420
	21st to end	Day	21% 14% 38% 20% 6% 1	462
April	1st to 10th	Day	16% 16% 43% 17% 7% 2	420
	11th to 20th	Day	13% 15% 34% 25% 10% 3	412
	21st to end	Day	20% 13% 33% 23% 10% 1	420
May	1st to 10th	Day	19% 16% 31% 21% 11% 2	423
	11th to 20th	Day	16% 9% 32% 29% 11% 3	447
	21st to end	Day	16% 5% 23% 29% 20% 6%	485
June	1st to 10th	Day	12% 5% 26% 32% 18% 7%	450
	11th to 20th	Day	11% 6% 24% 31% 19% 8%	450
	21st to end	Day	9% 3 24% 40% 19% 4	450
July	1st to 10th	Day	10% 4 20% 34% 22% 10%	445
	11th to 20th	Day	5% 1 13% 38% 32% 11%	444
	21st to end	Day	10% 2 19% 36% 24% 9%	488
August	1st to 10th	Day	10% 3 16% 34% 28% 9%	446
	11th to 20th	Day	11% 2 16% 31% 32% 8%	439
	21st to end	Day	9% 4 16% 30% 28% 13%	495
September	1st to 10th	Day	14% 4 18% 27% 22% 15%	450
	11th to 20th	Day	12% 4 23% 27% 23% 11%	450
	21st to end	Day	22% 11% 24% 25% 13% 4	450
October	1st to 10th	Day	17% 6% 24% 28% 16% 8%	450
	11th to 20th	Day	18% 10% 26% 27% 16% 3	450
	21st to end	Day	17% 12% 34% 23% 11% 3	495
November	1st to 10th	Day	17% 11% 29% 23% 15% 5%	377
	11th to 20th	Day	18% 14% 35% 23% 10% 1	370
	21st to end	Day	19% 18% 28% 23% 9% 4	280
December	1st to 10th	Day	21% 21% 36% 14% 7% 1	180
	11th to 20th	Day	25% 20% 30% 18% 7% 1	180
	21st to end	Day	21% 18% 30% 22% 9%	198
January	1st to 10th	Night	19% 19% 36% 23% 4	760
	11th to 20th	Night	22% 13% 33% 26% 5%	760
	21st to end	Night	19% 15% 38% 25% 2	836
February	1st to 10th	Night	20% 12% 38% 27% 4	760
	11th to 20th	Night	22% 20% 36% 20% 2	743
	21st to end	Night	23% 14% 38% 21% 4	628
March	1st to 10th	Night	20% 16% 35% 24% 6%	723
	11th to 20th	Night	22% 13% 34% 23% 7% 1	720
	21st to end	Night	20% 10% 36% 29% 5% 1	792
April	1st to 10th	Night	17% 12% 41% 24% 5%	720
	11th to 20th	Night	14% 12% 34% 32% 7%	711
	21st to end	Night	19% 9% 32% 31% 9% 1	720
May	1st to 10th	Night	16% 10% 32% 31% 9% 1	716
	11th to 20th	Night	15% 6% 27% 40% 11%	354
	21st to end	Night	13% 4 20% 40% 21% 3	389
June	1st to 10th	Night	11% 5% 22% 44% 17% 1	360
	11th to 20th	Night	9% 4 21% 45% 20% 2	360
	21st to end	Night	10% 1 18% 46% 24% 1	360
July	1st to 10th	Night	11% 3 13% 42% 29% 2	350
	11th to 20th	Night	4 1 11% 47% 33% 4	348
	21st to end	Night	7% 2 16% 40% 33% 2	582
August	1st to 10th	Night	9% 2 10% 42% 34% 3	537
	11th to 20th	Night	12% 3 13% 39% 30% 3	694
	21st to end	Night	10% 3 13% 37% 31% 6%	792
September	1st to 10th	Night	15% 3 13% 35% 29% 5%	720
	11th to 20th	Night	10% 3 16% 36% 30% 5%	720
	21st to end	Night	22% 5% 18% 32% 21% 2	720
October	1st to 10th	Night	18% 5% 20% 31% 21% 5%	720
	11th to 20th	Night	18% 9% 25% 31% 17% 1	720
	21st to end	Night	19% 10% 28% 26% 14% 2	792
November	1st to 10th	Night	15% 8% 31% 28% 14% 3	740
	11th to 20th	Night	18% 13% 29% 29% 9% 1	760
	21st to end	Night	16% 15% 27% 30% 11% 1	760
December	1st to 10th	Night	22% 14% 32% 22% 9% 1	760
	11th to 20th	Night	20% 13% 36% 24% 6%	760
	21st to end	Night	18% 12% 33% 31% 5%	836

Page generated at 2024-02-27 06:30:19. Version ac07

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