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 2024-11-01.

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% 6% 2 6% 4 4 4 4 6% 8% 44%	101118
	Night	15% 7% 2 6% 4 4 4 3 5% 7% 42%	97793
Transparency	Day	37% 7% 14% 24% 15% 3	100912
	Night	40% 6% 12% 23% 16% 3	97669
Seeing	Day	16% 11% 28% 26% 15% 5%	15127
	Night	17% 10% 28% 31% 14% 2	24539

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% 2 5% 4 3 3 3 5% 8% 46%	2517
	11th to 20th	Day	16% 7% 2 7% 5% 4 4 3 5% 6% 41%	2808
	21st to end	Day	16% 9% 3 6% 5% 4 5% 3 5% 7% 38%	3124
February	1st to 10th	Day	14% 7% 3 7% 3 5% 5% 4 7% 7% 39%	1710
	11th to 20th	Day	18% 6% 2 5% 3 3 4 3 5% 7% 43%	1803
	21st to end	Day	19% 8% 2 6% 4 4 4 3 6% 6% 38%	1570
March	1st to 10th	Day	21% 6% 2 6% 4 4 3 3 5% 7% 38%	3237
	11th to 20th	Day	10% 4 2 3 3 3 4 4 5% 8% 55%	3480
	21st to end	Day	20% 7% 2 5% 4 3 3 3 4 6% 41%	3974
April	1st to 10th	Day	11% 6% 2 6% 3 4 4 4 5% 8% 47%	2280
	11th to 20th	Day	11% 5% 2 5% 4 4 4 4 5% 7% 51%	2254
	21st to end	Day	13% 7% 2 5% 3 3 4 3 5% 8% 46%	2280
May	1st to 10th	Day	20% 7% 3 6% 4 4 4 4 6% 9% 33%	3809
	11th to 20th	Day	17% 8% 2 7% 5% 4 5% 4 6% 8% 35%	4398
	21st to end	Day	9% 4 2 5% 4 3 4 4 6% 11% 49%	4823
June	1st to 10th	Day	9% 4 1 5% 4 5% 5% 4 8% 10% 46%	2660
	11th to 20th	Day	9% 4 1 5% 4 4 4 4 6% 10% 49%	2660
	21st to end	Day	7% 4 2 4 4 4 4 4 8% 11% 48%	2660
July	1st to 10th	Day	6% 4 2 5% 3 4 5% 5% 9% 14% 44%	4440
	11th to 20th	Day	10% 5% 2 6% 4 5% 5% 5% 8% 11% 39%	4440
	21st to end	Day	10% 5% 2 7% 6% 5% 6% 5% 8% 9% 37%	4471
August	1st to 10th	Day	14% 6% 2 7% 4 4 5% 4 8% 10% 35%	4087
	11th to 20th	Day	9% 5% 3 7% 5% 5% 6% 4 7% 9% 41%	3730
	21st to end	Day	8% 3 2 5% 4 4 4 3 6% 9% 52%	4180
September	1st to 10th	Day	12% 5% 1 5% 4 4 4 3 7% 8% 46%	2280
	11th to 20th	Day	10% 6% 3 6% 4 3 3 4 6% 7% 49%	2280
	21st to end	Day	18% 8% 3 6% 4 4 4 3 5% 5% 40%	2047
October	1st to 10th	Day	13% 6% 2 7% 4 4 3 3 5% 6% 47%	1900
	11th to 20th	Day	15% 5% 2 5% 3 3 3 2 4 6% 53%	1900
	21st to end	Day	13% 5% 2 5% 4 3 3 3 4 8% 49%	2090
November	1st to 10th	Day	12% 5% 1 4 5% 2 3 4 5% 6% 52%	1694
	11th to 20th	Day	13% 5% 2 5% 4 4 4 3 6% 6% 49%	1710
	21st to end	Day	15% 6% 2 5% 4 3 3 3 5% 6% 49%	1620
December	1st to 10th	Day	16% 7% 3 6% 4 4 5% 3 6% 7% 40%	1520
	11th to 20th	Day	15% 9% 3 5% 4 3 2 3 4 5% 48%	1910
	21st to end	Day	15% 7% 2 6% 4 4 5% 4 6% 6% 42%	2772
January	1st to 10th	Night	15% 8% 3 5% 4 3 4 3 5% 7% 43%	4429
	11th to 20th	Night	16% 7% 2 7% 4 4 4 2 4 5% 44%	4148
	21st to end	Night	18% 10% 3 7% 4 3 3 3 4 5% 40%	4532
February	1st to 10th	Night	16% 8% 3 5% 4 3 3 3 6% 6% 43%	2470
	11th to 20th	Night	19% 7% 2 5% 3 4 3 3 5% 7% 41%	2261
	21st to end	Night	18% 9% 2 5% 3 2 3 3 5% 7% 44%	1884
March	1st to 10th	Night	22% 9% 3 7% 4 4 4 4 4 5% 37%	3613
	11th to 20th	Night	14% 6% 2 5% 3 3 4 3 5% 7% 49%	3480
	21st to end	Night	17% 8% 2 5% 4 4 3 3 4 6% 44%	3658
April	1st to 10th	Night	15% 6% 2 6% 5% 4 4 4 5% 6% 41%	1900
	11th to 20th	Night	11% 6% 2 6% 4 3 4 3 5% 7% 48%	1875
	21st to end	Night	16% 4 2 5% 4 4 5% 3 6% 6% 44%	1900
May	1st to 10th	Night	18% 7% 2 8% 4 5% 5% 4 6% 7% 33%	3112
	11th to 20th	Night	21% 8% 2 6% 4 4 5% 4 5% 7% 33%	2495
	21st to end	Night	10% 5% 2 6% 4 4 4 4 7% 10% 42%	2732
June	1st to 10th	Night	11% 6% 1 6% 5% 5% 5% 5% 6% 7% 43%	1520
	11th to 20th	Night	8% 6% 2 7% 5% 5% 4 4 7% 10% 43%	1520
	21st to end	Night	8% 5% 2 5% 5% 5% 5% 5% 8% 10% 42%	1520
July	1st to 10th	Night	8% 5% 2 7% 4 5% 6% 4 8% 10% 39%	2520
	11th to 20th	Night	10% 5% 2 6% 4 4 5% 5% 8% 11% 40%	2520
	21st to end	Night	13% 7% 3 8% 5% 5% 5% 4 7% 8% 35%	3078
August	1st to 10th	Night	17% 8% 2 7% 5% 4 4 3 6% 9% 34%	2825
	11th to 20th	Night	12% 6% 2 7% 5% 4 5% 4 7% 8% 39%	3081
	21st to end	Night	8% 5% 2 5% 4 4 4 4 5% 8% 51%	3476
September	1st to 10th	Night	13% 7% 2 5% 4 4 3 3 5% 7% 48%	1900
	11th to 20th	Night	9% 4 2 5% 3 4 4 4 6% 9% 50%	1900
	21st to end	Night	19% 7% 3 6% 4 5% 4 3 5% 7% 37%	2130
October	1st to 10th	Night	16% 6% 2 6% 4 3 4 4 4 6% 44%	2280
	11th to 20th	Night	16% 6% 2 4 4 4 3 3 4 5% 50%	2280
	21st to end	Night	16% 6% 1 5% 3 3 3 3 5% 7% 48%	2508
November	1st to 10th	Night	13% 5% 3 5% 4 3 3 3 4 5% 52%	2389
	11th to 20th	Night	15% 7% 2 5% 4 3 3 3 4 7% 46%	2470
	21st to end	Night	12% 6% 2 4 4 3 4 3 5% 8% 49%	2558
December	1st to 10th	Night	18% 8% 2 6% 4 3 4 4 5% 7% 39%	2660
	11th to 20th	Night	18% 7% 2 7% 5% 3 3 3 5% 6% 42%	3285
	21st to end	Night	15% 8% 2 6% 5% 4 4 4 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	44% 6% 11% 21% 14% 4	3237
	11th to 20th	Day	27% 5% 10% 31% 23% 4	3480
	21st to end	Day	44% 5% 9% 20% 17% 4	3974
April	1st to 10th	Day	34% 7% 12% 23% 18% 5%	2280
	11th to 20th	Day	33% 6% 12% 23% 20% 5%	2254
	21st to end	Day	36% 6% 12% 23% 18% 5%	2280
May	1st to 10th	Day	47% 10% 12% 19% 10% 2	3844
	11th to 20th	Day	45% 10% 16% 19% 8% 2	4402
	21st to end	Day	28% 9% 16% 27% 17% 2	4837
June	1st to 10th	Day	32% 9% 15% 27% 15% 2	2660
	11th to 20th	Day	30% 9% 16% 25% 17% 3	2660
	21st to end	Day	29% 9% 16% 26% 18% 2	2660
July	1st to 10th	Day	29% 10% 27% 18% 13% 3	4370
	11th to 20th	Day	38% 7% 21% 25% 7% 1	4365
	21st to end	Day	39% 10% 17% 20% 13% 1	4328
August	1st to 10th	Day	41% 8% 18% 25% 7%	4074
	11th to 20th	Day	37% 8% 15% 28% 12% 1	3766
	21st to end	Day	29% 7% 15% 28% 19% 2	4180
September	1st to 10th	Day	36% 8% 15% 19% 18% 4	2280
	11th to 20th	Day	34% 8% 10% 25% 21% 3	2280
	21st to end	Day	46% 5% 10% 19% 17% 3	2047
October	1st to 10th	Day	39% 5% 10% 24% 19% 4	1900
	11th to 20th	Day	35% 4 8% 27% 22% 4	1900
	21st to end	Day	35% 5% 9% 26% 21% 5%	2090
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% 4 9% 23% 18% 4	1884
March	1st to 10th	Night	48% 6% 10% 21% 14% 2	3613
	11th to 20th	Night	33% 5% 10% 28% 20% 3	3480
	21st to end	Night	43% 4 8% 21% 18% 6%	3658
April	1st to 10th	Night	42% 6% 11% 17% 19% 4	1900
	11th to 20th	Night	35% 6% 13% 20% 20% 6%	1875
	21st to end	Night	39% 6% 11% 23% 16% 4	1900
May	1st to 10th	Night	47% 9% 12% 21% 8% 2	3142
	11th to 20th	Night	48% 9% 13% 19% 9% 1	2496
	21st to end	Night	35% 8% 17% 23% 15% 2	2739
June	1st to 10th	Night	37% 9% 13% 23% 16% 2	1520
	11th to 20th	Night	35% 9% 14% 25% 14% 2	1520
	21st to end	Night	34% 9% 16% 23% 16% 3	1520
July	1st to 10th	Night	38% 11% 20% 19% 10% 2	2480
	11th to 20th	Night	35% 8% 24% 24% 7% 1	2472
	21st to end	Night	45% 8% 16% 19% 13%	2980
August	1st to 10th	Night	47% 7% 17% 21% 8%	2814
	11th to 20th	Night	40% 8% 15% 27% 9%	3111
	21st to end	Night	30% 6% 12% 26% 24% 2	3476
September	1st to 10th	Night	36% 6% 16% 20% 17% 5%	1900
	11th to 20th	Night	31% 6% 11% 28% 21% 3	1900
	21st to end	Night	46% 7% 9% 18% 16% 3	2130
October	1st to 10th	Night	40% 6% 9% 24% 19% 3	2280
	11th to 20th	Night	37% 4 9% 25% 21% 4	2280
	21st to end	Night	36% 4 10% 25% 21% 4	2508
November	1st to 10th	Night	36% 4 10% 27% 18% 5%	2389
	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	24% 22% 33% 17% 4	382
March	1st to 10th	Day	22% 18% 33% 22% 5% 1	460
	11th to 20th	Day	22% 20% 34% 19% 4 2	460
	21st to end	Day	22% 13% 40% 20% 6% 1	506
April	1st to 10th	Day	16% 18% 41% 17% 6% 2	460
	11th to 20th	Day	13% 15% 35% 25% 9% 3	452
	21st to end	Day	20% 13% 33% 23% 10% 1	460
May	1st to 10th	Day	19% 16% 31% 21% 10% 2	463
	11th to 20th	Day	16% 10% 32% 30% 11% 3	487
	21st to end	Day	16% 5% 25% 29% 19% 6%	529
June	1st to 10th	Day	11% 7% 27% 31% 18% 6%	490
	11th to 20th	Day	10% 6% 24% 32% 20% 8%	490
	21st to end	Day	9% 3 25% 40% 19% 4	490
July	1st to 10th	Day	9% 4 19% 36% 22% 9%	485
	11th to 20th	Day	6% 1 14% 38% 31% 10%	484
	21st to end	Day	11% 2 19% 36% 23% 8%	532
August	1st to 10th	Day	12% 3 17% 33% 27% 8%	486
	11th to 20th	Day	11% 2 17% 32% 31% 8%	479
	21st to end	Day	8% 4 16% 31% 28% 13%	539
September	1st to 10th	Day	13% 4 20% 28% 20% 14%	490
	11th to 20th	Day	11% 4 23% 28% 23% 10%	490
	21st to end	Day	24% 11% 23% 26% 13% 4	490
October	1st to 10th	Day	16% 7% 23% 29% 16% 8%	490
	11th to 20th	Day	17% 11% 26% 26% 16% 4	490
	21st to end	Day	15% 11% 33% 24% 13% 4	539
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	21% 16% 34% 24% 6%	760
	11th to 20th	Night	22% 14% 33% 23% 6% 1	760
	21st to end	Night	20% 11% 35% 29% 5%	836
April	1st to 10th	Night	18% 14% 41% 23% 5%	760
	11th to 20th	Night	14% 12% 34% 32% 7%	751
	21st to end	Night	18% 9% 32% 31% 9% 1	760
May	1st to 10th	Night	16% 11% 33% 31% 9% 1	755
	11th to 20th	Night	16% 6% 28% 40% 11%	374
	21st to end	Night	12% 4 21% 40% 20% 3	411
June	1st to 10th	Night	10% 6% 23% 44% 17% 1	380
	11th to 20th	Night	9% 4 21% 45% 20% 2	380
	21st to end	Night	10% 2 19% 46% 23% 1	380
July	1st to 10th	Night	11% 2 14% 42% 29% 2	370
	11th to 20th	Night	5% 1 11% 47% 32% 4	368
	21st to end	Night	8% 2 17% 40% 32% 2	615
August	1st to 10th	Night	11% 3 11% 41% 32% 3	567
	11th to 20th	Night	12% 3 13% 40% 29% 3	734
	21st to end	Night	10% 3 13% 38% 31% 6%	836
September	1st to 10th	Night	15% 3 14% 36% 28% 4	760
	11th to 20th	Night	11% 2 16% 36% 29% 5%	760
	21st to end	Night	23% 5% 18% 31% 21% 2	760
October	1st to 10th	Night	18% 5% 20% 31% 21% 5%	760
	11th to 20th	Night	17% 10% 26% 30% 17% 1	760
	21st to end	Night	18% 10% 28% 27% 15% 2	836
November	1st to 10th	Night	15% 8% 31% 28% 14% 3	743
	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 2024-10-29 11:20:45. Version ac07

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