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 2026-09-14.

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%	148792
	Night	14% 6% 2 6% 4 4 4 4 5% 7% 43%	142315
Transparency	Day	37% 6% 14% 24% 16% 3	152381
	Night	39% 5% 12% 23% 17% 3	146797
Seeing	Day	16% 12% 28% 26% 14% 4	17555
	Night	17% 10% 28% 30% 13% 1	26937

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	13% 5% 2 5% 4 3 4 3 6% 7% 47%	4661
	11th to 20th	Day	14% 6% 2 6% 3 3 3 2 3 4 51%	5220
	21st to end	Day	13% 7% 2 6% 4 4 4 3 5% 6% 45%	5780
February	1st to 10th	Day	13% 7% 3 7% 4 5% 5% 4 7% 7% 40%	1890
	11th to 20th	Day	19% 7% 2 5% 3 3 4 3 5% 7% 42%	1999
	21st to end	Day	19% 8% 2 6% 4 4 4 3 5% 6% 40%	1730
March	1st to 10th	Day	17% 5% 2 5% 3 4 4 4 6% 8% 43%	4756
	11th to 20th	Day	10% 5% 2 5% 3 3 4 3 4 7% 54%	5090
	21st to end	Day	16% 7% 2 6% 5% 3 3 3 4 7% 45%	5820
April	1st to 10th	Day	11% 6% 2 6% 3 3 4 4 6% 8% 47%	2520
	11th to 20th	Day	11% 5% 1 5% 4 4 4 4 5% 7% 50%	2494
	21st to end	Day	12% 7% 2 5% 4 3 4 4 6% 8% 46%	2520
May	1st to 10th	Day	17% 6% 2 6% 4 4 4 3 6% 8% 40%	7092
	11th to 20th	Day	15% 6% 2 6% 4 3 4 3 5% 8% 43%	8221
	21st to end	Day	19% 6% 3 6% 4 3 4 3 5% 8% 40%	9045
June	1st to 10th	Day	8% 4 1 6% 4 5% 5% 4 7% 9% 46%	2940
	11th to 20th	Day	9% 5% 1 5% 4 3 4 4 7% 10% 48%	2940
	21st to end	Day	8% 4 2 4 4 4 4 4 7% 11% 48%	2940
July	1st to 10th	Day	7% 4 2 5% 3 4 5% 4 7% 12% 46%	8280
	11th to 20th	Day	9% 6% 2 6% 5% 5% 6% 6% 9% 12% 34%	8280
	21st to end	Day	9% 5% 2 7% 5% 5% 6% 5% 8% 10% 39%	8345
August	1st to 10th	Day	12% 6% 2 7% 4 4 6% 5% 8% 11% 34%	5997
	11th to 20th	Day	9% 5% 3 7% 5% 5% 6% 5% 8% 9% 39%	5488
	21st to end	Day	8% 4 2 5% 4 4 4 4 6% 10% 49%	6080
September	1st to 10th	Day	12% 5% 1 5% 3 4 4 3 6% 8% 48%	2520
	11th to 20th	Day	11% 7% 3 6% 4 4 3 4 6% 6% 48%	2436
	21st to end	Day	18% 8% 3 7% 4 4 4 3 5% 6% 39%	2154
October	1st to 10th	Day	13% 5% 2 7% 4 4 4 3 5% 6% 48%	2000
	11th to 20th	Day	15% 5% 2 5% 3 2 3 2 4 6% 53%	2000
	21st to end	Day	13% 6% 2 5% 4 3 3 3 5% 7% 49%	2200
November	1st to 10th	Day	12% 5% 2 4 5% 2 3 4 5% 7% 53%	1876
	11th to 20th	Day	12% 5% 2 5% 5% 4 4 3 6% 6% 49%	1890
	21st to end	Day	15% 6% 2 6% 4 3 3 3 5% 5% 50%	1790
December	1st to 10th	Day	11% 6% 2 6% 4 4 4 3 5% 6% 50%	2680
	11th to 20th	Day	18% 9% 3 5% 4 3 2 2 4 5% 47%	3070
	21st to end	Day	12% 6% 2 6% 4 4 4 4 5% 7% 46%	4048
January	1st to 10th	Night	12% 7% 2 5% 4 4 5% 4 6% 7% 45%	8233
	11th to 20th	Night	13% 6% 2 6% 4 3 3 2 3 4 52%	7722
	21st to end	Night	14% 7% 2 6% 3 4 4 3 5% 6% 46%	8401
February	1st to 10th	Night	16% 7% 2 5% 4 3 4 3 6% 6% 43%	2730
	11th to 20th	Night	19% 7% 2 5% 3 4 3 3 5% 7% 41%	2505
	21st to end	Night	17% 8% 2 5% 3 3 4 3 5% 7% 44%	2076
March	1st to 10th	Night	16% 7% 2 6% 3 3 4 4 4 5% 46%	5313
	11th to 20th	Night	12% 6% 2 5% 3 3 4 3 6% 7% 49%	5090
	21st to end	Night	14% 7% 2 6% 4 4 4 3 4 6% 45%	5354
April	1st to 10th	Night	15% 6% 2 6% 5% 4 4 4 6% 7% 41%	2100
	11th to 20th	Night	11% 6% 2 6% 4 3 4 3 5% 7% 48%	2075
	21st to end	Night	15% 4 2 5% 4 4 5% 3 6% 7% 45%	2100
May	1st to 10th	Night	14% 6% 2 7% 4 5% 5% 5% 7% 9% 36%	5815
	11th to 20th	Night	16% 7% 2 5% 4 4 5% 4 5% 8% 41%	4639
	21st to end	Night	22% 7% 3 7% 4 3 4 4 5% 7% 34%	5108
June	1st to 10th	Night	10% 6% 1 6% 5% 5% 5% 5% 6% 7% 44%	1680
	11th to 20th	Night	8% 6% 2 7% 6% 5% 4 4 7% 10% 42%	1680
	21st to end	Night	8% 4 2 5% 5% 5% 5% 5% 8% 10% 42%	1680
July	1st to 10th	Night	11% 6% 2 8% 5% 5% 5% 4 7% 9% 38%	4678
	11th to 20th	Night	11% 6% 2 8% 5% 5% 5% 5% 8% 12% 33%	4677
	21st to end	Night	12% 6% 3 8% 5% 5% 5% 5% 7% 9% 36%	5727
August	1st to 10th	Night	15% 8% 3 9% 5% 5% 5% 4 6% 9% 32%	4135
	11th to 20th	Night	12% 6% 2 7% 6% 4 5% 4 6% 9% 38%	4526
	21st to end	Night	8% 5% 3 6% 5% 5% 5% 4 6% 8% 45%	5045
September	1st to 10th	Night	12% 6% 2 5% 4 4 3 3 5% 7% 49%	2100
	11th to 20th	Night	10% 5% 2 5% 3 4 4 4 6% 8% 49%	2031
	21st to end	Night	19% 8% 3 6% 4 5% 4 4 5% 7% 36%	2242
October	1st to 10th	Night	15% 6% 2 6% 3 3 4 4 4 6% 46%	2400
	11th to 20th	Night	17% 6% 2 4 3 4 3 3 4 5% 50%	2400
	21st to end	Night	16% 5% 1 5% 3 3 3 3 5% 6% 48%	2640
November	1st to 10th	Night	12% 5% 3 5% 4 3 3 3 4 6% 52%	2640
	11th to 20th	Night	15% 7% 2 5% 4 3 3 3 5% 7% 46%	2730
	21st to end	Night	12% 6% 2 4 4 3 4 3 5% 7% 49%	2828
December	1st to 10th	Night	11% 6% 2 5% 3 3 3 3 5% 7% 52%	4720
	11th to 20th	Night	21% 7% 2 6% 4 3 3 3 5% 6% 39%	5345
	21st to end	Night	13% 8% 2 6% 4 4 4 4 6% 7% 42%	7150

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% 4 9% 26% 22% 3	4662
	11th to 20th	Day	38% 3 7% 21% 25% 6%	5220
	21st to end	Day	40% 5% 9% 31% 13% 2	5780
February	1st to 10th	Day	41% 6% 13% 24% 14% 2	1890
	11th to 20th	Day	42% 4 10% 23% 18% 3	2008
	21st to end	Day	45% 5% 11% 19% 16% 4	1730
March	1st to 10th	Day	39% 5% 10% 20% 19% 7%	4756
	11th to 20th	Day	31% 4 11% 28% 21% 6%	5090
	21st to end	Day	41% 5% 10% 19% 19% 7%	5820
April	1st to 10th	Day	34% 7% 13% 22% 19% 5%	2520
	11th to 20th	Day	33% 6% 13% 24% 20% 5%	2494
	21st to end	Day	36% 6% 12% 24% 18% 4	2520
May	1st to 10th	Day	42% 7% 14% 22% 14% 2	7124
	11th to 20th	Day	38% 8% 14% 25% 14% 1	8225
	21st to end	Day	43% 6% 12% 21% 14% 3	9061
June	1st to 10th	Day	32% 9% 15% 26% 16% 2	2940
	11th to 20th	Day	30% 9% 17% 25% 16% 3	2940
	21st to end	Day	29% 9% 16% 26% 18% 2	2940
July	1st to 10th	Day	31% 9% 23% 23% 12% 2	8210
	11th to 20th	Day	41% 9% 18% 23% 7% 1	8205
	21st to end	Day	37% 9% 15% 23% 16% 1	8160
August	1st to 10th	Day	41% 10% 21% 21% 5%	5984
	11th to 20th	Day	38% 9% 19% 23% 11%	5524
	21st to end	Day	31% 7% 17% 28% 16% 2	6080
September	1st to 10th	Day	34% 8% 16% 22% 17% 4	2520
	11th to 20th	Day	35% 8% 10% 24% 21% 3	2436
	21st to end	Day	46% 5% 10% 19% 16% 3	2154
October	1st to 10th	Day	34% 5% 8% 22% 25% 6%	3260
	11th to 20th	Day	27% 3 6% 27% 28% 10%	3240
	21st to end	Day	23% 4 9% 30% 26% 9%	3538
November	1st to 10th	Day	32% 4 11% 29% 20% 4	1876
	11th to 20th	Day	36% 4 12% 22% 21% 4	1890
	21st to end	Day	38% 3 10% 29% 17% 3	1790
December	1st to 10th	Day	35% 4 15% 27% 15% 3	2680
	11th to 20th	Day	43% 2 13% 26% 14% 3	3066
	21st to end	Day	36% 6% 15% 27% 16% 1	4048
January	1st to 10th	Night	37% 3 12% 23% 20% 4	8234
	11th to 20th	Night	37% 3 6% 26% 21% 7%	7722
	21st to end	Night	40% 3 9% 28% 17% 3	8401
February	1st to 10th	Night	41% 5% 12% 24% 17% 2	2730
	11th to 20th	Night	44% 4 8% 20% 19% 4	2507
	21st to end	Night	41% 4 9% 23% 18% 5%	2076
March	1st to 10th	Night	40% 5% 9% 22% 17% 8%	5313
	11th to 20th	Night	34% 5% 11% 24% 20% 6%	5090
	21st to end	Night	41% 4 10% 21% 18% 6%	5354
April	1st to 10th	Night	41% 6% 11% 18% 19% 5%	2100
	11th to 20th	Night	35% 5% 13% 21% 21% 5%	2075
	21st to end	Night	38% 6% 12% 24% 17% 4	2100
May	1st to 10th	Night	42% 7% 15% 24% 10% 1	5845
	11th to 20th	Night	41% 7% 15% 23% 13% 1	4640
	21st to end	Night	49% 6% 12% 18% 15% 1	5115
June	1st to 10th	Night	37% 8% 13% 23% 17% 2	1680
	11th to 20th	Night	37% 9% 14% 25% 14% 2	1680
	21st to end	Night	34% 9% 16% 22% 17% 2	1680
July	1st to 10th	Night	42% 9% 15% 20% 12% 2	4640
	11th to 20th	Night	41% 10% 20% 21% 7%	4632
	21st to end	Night	42% 8% 16% 21% 14%	5598
August	1st to 10th	Night	49% 7% 19% 18% 6%	4124
	11th to 20th	Night	41% 8% 18% 25% 8%	4556
	21st to end	Night	36% 7% 13% 25% 19% 1	5045
September	1st to 10th	Night	36% 6% 15% 22% 17% 4	2100
	11th to 20th	Night	33% 6% 11% 28% 20% 3	2031
	21st to end	Night	47% 7% 10% 18% 15% 3	2242
October	1st to 10th	Night	36% 5% 10% 23% 22% 4	3920
	11th to 20th	Night	26% 3 10% 22% 28% 10%	3899
	21st to end	Night	23% 2 10% 30% 26% 8%	4252
November	1st to 10th	Night	35% 4 9% 26% 21% 5%	2640
	11th to 20th	Night	39% 4 10% 22% 20% 6%	2730
	21st to end	Night	34% 4 11% 27% 20% 3	2828
December	1st to 10th	Night	33% 4 13% 27% 20% 3	4720
	11th to 20th	Night	47% 3 12% 21% 13% 4	5348
	21st to end	Night	39% 6% 14% 24% 16% 1	7150

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	25% 22% 32% 15% 6%	220
	11th to 20th	Day	23% 29% 32% 14% 2	319
	21st to end	Day	19% 23% 41% 14% 3	363
February	1st to 10th	Day	21% 22% 41% 12% 4	330
	11th to 20th	Day	29% 21% 36% 12% 2	487
	21st to end	Day	24% 21% 33% 18% 4	446
March	1st to 10th	Day	21% 19% 33% 21% 6% 1	540
	11th to 20th	Day	23% 19% 34% 18% 4 2	540
	21st to end	Day	20% 15% 41% 18% 5% 1	594
April	1st to 10th	Day	17% 18% 39% 17% 7% 2	540
	11th to 20th	Day	14% 16% 35% 24% 9% 2	532
	21st to end	Day	18% 14% 32% 26% 10% 1	540
May	1st to 10th	Day	18% 18% 33% 19% 9% 2	543
	11th to 20th	Day	15% 11% 31% 30% 10% 2	567
	21st to end	Day	18% 7% 26% 27% 17% 5%	617
June	1st to 10th	Day	11% 6% 29% 31% 18% 6%	570
	11th to 20th	Day	10% 8% 25% 32% 18% 7%	570
	21st to end	Day	9% 3 25% 39% 19% 4	570
July	1st to 10th	Day	9% 4 18% 37% 23% 9%	565
	11th to 20th	Day	7% 1 14% 39% 30% 10%	564
	21st to end	Day	10% 3 18% 36% 25% 8%	620
August	1st to 10th	Day	12% 3 17% 34% 26% 7%	566
	11th to 20th	Day	11% 2 16% 32% 31% 7%	559
	21st to end	Day	7% 4 19% 32% 27% 12%	627
September	1st to 10th	Day	13% 3 22% 30% 20% 12%	570
	11th to 20th	Day	13% 5% 22% 28% 22% 10%	542
	21st to end	Day	24% 10% 24% 25% 12% 4	530
October	1st to 10th	Day	16% 7% 22% 30% 16% 9%	530
	11th to 20th	Day	18% 12% 26% 24% 15% 3	530
	21st to end	Day	16% 13% 33% 22% 12% 4	583
November	1st to 10th	Day	16% 13% 31% 23% 14% 4	439
	11th to 20th	Day	17% 15% 35% 23% 9% 1	430
	21st to end	Day	19% 19% 28% 21% 8% 4	330
December	1st to 10th	Day	20% 21% 38% 14% 6%	220
	11th to 20th	Day	25% 20% 30% 18% 6%	220
	21st to end	Day	21% 18% 31% 21% 9%	242
January	1st to 10th	Night	19% 20% 35% 22% 4	840
	11th to 20th	Night	22% 16% 33% 25% 5%	840
	21st to end	Night	19% 16% 38% 24% 2	924
February	1st to 10th	Night	20% 12% 37% 26% 4	840
	11th to 20th	Night	23% 21% 35% 20% 1	823
	21st to end	Night	23% 14% 38% 21% 4	692
March	1st to 10th	Night	21% 16% 33% 25% 5%	840
	11th to 20th	Night	22% 15% 33% 23% 6% 1	840
	21st to end	Night	20% 12% 36% 27% 5%	924
April	1st to 10th	Night	18% 14% 40% 22% 5%	840
	11th to 20th	Night	14% 12% 36% 31% 7%	831
	21st to end	Night	17% 9% 33% 31% 8% 1	840
May	1st to 10th	Night	16% 12% 33% 30% 8% 1	835
	11th to 20th	Night	15% 6% 29% 39% 10%	414
	21st to end	Night	14% 6% 22% 38% 18% 2	455
June	1st to 10th	Night	10% 6% 23% 44% 16% 1	420
	11th to 20th	Night	10% 5% 21% 43% 19% 2	420
	21st to end	Night	10% 2 19% 45% 23% 1	420
July	1st to 10th	Night	11% 3 14% 41% 29% 2	410
	11th to 20th	Night	6% 1 12% 47% 31% 3	408
	21st to end	Night	8% 2 17% 39% 32% 2	681
August	1st to 10th	Night	11% 3 11% 41% 31% 3	627
	11th to 20th	Night	12% 4 13% 39% 29% 3	812
	21st to end	Night	10% 3 14% 38% 30% 5%	924
September	1st to 10th	Night	15% 4 14% 37% 26% 4	840
	11th to 20th	Night	12% 2 16% 36% 29% 5%	813
	21st to end	Night	23% 5% 18% 32% 20% 2	800
October	1st to 10th	Night	18% 5% 19% 31% 21% 6%	800
	11th to 20th	Night	18% 11% 25% 30% 16% 1	800
	21st to end	Night	18% 10% 28% 27% 15% 2	880
November	1st to 10th	Night	15% 9% 31% 29% 13% 3	820
	11th to 20th	Night	18% 14% 30% 29% 9% 1	840
	21st to end	Night	16% 17% 27% 29% 10% 1	840
December	1st to 10th	Night	22% 15% 32% 22% 8% 1	840
	11th to 20th	Night	20% 14% 35% 24% 6%	840
	21st to end	Night	18% 12% 33% 31% 5%	924

Page generated at 2026-09-11 04:11:55. Version ac07

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