Elizabeth Ridge
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Elizabeth Ridge clear sky chart from 2005-11-06 to 2025-12-18.

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	3 8% 4 10% 6% 5% 4 4 5% 7% 45%	135809
	Night	1 6% 3 9% 5% 4 4 4 6% 7% 51%	132721
Transparency	Day	41% 2 7% 21% 21% 9%	130579
	Night	35% 2 8% 23% 22% 9%	128954
Seeing	Day	17% 29% 28% 17% 7% 2	16842
	Night	10% 20% 29% 26% 12% 2	27112

By Month

Percentage Cloud Cover SW (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	6% 7% 20% 8% 5% 4 3 5% 7% 35%	4098
	11th to 20th	Day	7% 5% 15% 11% 10% 4 2 4 4 38%	4100
	21st to end	Day	9% 4 12% 7% 4 3 3 3 6% 48%	4510
February	1st to 10th	Day	1 13% 5% 14% 9% 6% 4 4 6% 6% 33%	1800
	11th to 20th	Day	10% 7% 17% 8% 5% 4 4 4 7% 34%	1755
	21st to end	Day	9% 7% 16% 10% 6% 4 3 6% 6% 33%	1636
March	1st to 10th	Day	7% 9% 17% 8% 5% 4 3 4 5% 37%	4949
	11th to 20th	Day	6% 4 19% 4 4 4 3 6% 7% 42%	5000
	21st to end	Day	12% 9% 20% 8% 5% 5% 4 5% 6% 26%	5486
April	1st to 10th	Day	2 13% 5% 12% 6% 4 3 3 6% 7% 38%	2280
	11th to 20th	Day	2 16% 6% 13% 6% 4 4 3 5% 6% 35%	2443
	21st to end	Day	3 16% 6% 11% 5% 4 4 4 5% 7% 36%	2600
May	1st to 10th	Day	4 12% 7% 12% 5% 5% 5% 4 6% 6% 34%	5880
	11th to 20th	Day	3 14% 4 8% 5% 4 4 4 6% 9% 39%	5841
	21st to end	Day	3 9% 3 7% 5% 5% 5% 5% 6% 8% 45%	6698
June	1st to 10th	Day	5% 6% 2 6% 5% 5% 5% 4 7% 7% 48%	2800
	11th to 20th	Day	5% 6% 2 5% 4 3 4 3 5% 8% 54%	2800
	21st to end	Day	4 4 1 4 4 4 4 4 6% 8% 56%	2800
July	1st to 10th	Day	3 4 2 5% 4 4 5% 3 5% 6% 58%	6046
	11th to 20th	Day	3 4 2 7% 6% 6% 7% 5% 7% 8% 45%	5880
	21st to end	Day	5% 5% 2 6% 5% 6% 5% 5% 6% 8% 46%	6401
August	1st to 10th	Day	4 4 2 6% 4 5% 5% 4 6% 7% 52%	5779
	11th to 20th	Day	4 4 2 7% 5% 5% 6% 5% 7% 7% 51%	5798
	21st to end	Day	6% 5% 2 7% 5% 5% 5% 4 6% 6% 48%	6297
September	1st to 10th	Day	6% 5% 2 6% 4 4 4 3 5% 6% 54%	2358
	11th to 20th	Day	5% 6% 2 5% 4 4 4 4 5% 7% 55%	2200
	21st to end	Day	6% 8% 2 6% 3 3 3 3 4 5% 59%	2200
October	1st to 10th	Day	3 8% 2 4 3 3 3 3 4 5% 63%	3341
	11th to 20th	Day	5% 10% 3 7% 4 3 4 3 5% 5% 51%	3250
	21st to end	Day	1 7% 3 8% 3 3 3 3 6% 7% 55%	3548
November	1st to 10th	Day	2 8% 4 9% 3 3 4 4 8% 7% 49%	1915
	11th to 20th	Day	1 12% 4 7% 4 3 4 4 6% 7% 48%	1786
	21st to end	Day	1 6% 3 12% 7% 5% 4 3 5% 7% 46%	1680
December	1st to 10th	Day	1 5% 3 8% 7% 4 3 2 4 6% 58%	2700
	11th to 20th	Day	6% 4 13% 6% 4 5% 5% 8% 9% 40%	3082
	21st to end	Day	11% 6% 14% 6% 5% 5% 4 5% 6% 37%	4072
January	1st to 10th	Night	6% 5% 18% 10% 6% 4 3 5% 7% 36%	5867
	11th to 20th	Night	6% 6% 15% 12% 10% 4 3 4 5% 35%	5880
	21st to end	Night	5% 4 12% 6% 5% 4 3 5% 7% 48%	6468
February	1st to 10th	Night	10% 5% 12% 6% 5% 4 4 7% 8% 38%	2600
	11th to 20th	Night	6% 5% 13% 8% 5% 5% 4 6% 8% 40%	2532
	21st to end	Night	6% 4 14% 10% 5% 5% 3 5% 7% 40%	1990
March	1st to 10th	Night	5% 5% 11% 8% 6% 6% 4 7% 8% 41%	4945
	11th to 20th	Night	4 4 13% 6% 4 4 4 6% 9% 45%	5000
	21st to end	Night	8% 5% 14% 6% 5% 6% 4 6% 6% 40%	5489
April	1st to 10th	Night	2 10% 5% 9% 5% 5% 5% 4 4 6% 46%	2119
	11th to 20th	Night	1 12% 4 8% 6% 4 4 4 7% 8% 43%	1900
	21st to end	Night	2 12% 5% 9% 4 4 4 4 6% 8% 43%	1800
May	1st to 10th	Night	2 8% 5% 9% 4 4 6% 5% 6% 8% 44%	4100
	11th to 20th	Night	2 8% 4 5% 4 4 4 4 6% 8% 52%	4074
	21st to end	Night	2 6% 2 6% 4 4 4 4 7% 8% 52%	4181
June	1st to 10th	Night	3 4 2 4 4 4 4 5% 7% 10% 54%	1600
	11th to 20th	Night	3 3 1 4 3 3 3 3 4 8% 64%	1600
	21st to end	Night	1 2 1 3 2 2 3 3 5% 8% 70%	1600
July	1st to 10th	Night	1 2 1 3 3 3 4 3 5% 6% 70%	3914
	11th to 20th	Night	2 3 1 5% 4 4 5% 4 7% 9% 57%	4100
	21st to end	Night	2 2 1 4 3 4 5% 4 6% 7% 61%	4472
August	1st to 10th	Night	2 2 1 3 3 3 5% 4 6% 8% 64%	4033
	11th to 20th	Night	2 3 1 4 3 3 4 3 5% 5% 64%	4051
	21st to end	Night	2 2 1 4 4 5% 5% 4 6% 7% 60%	4680
September	1st to 10th	Night	2 3 1 3 3 2 4 4 6% 8% 66%	2038
	11th to 20th	Night	2 3 1 4 2 2 3 4 7% 6% 65%	2200
	21st to end	Night	3 5% 1 4 3 2 3 3 5% 5% 67%	2200
October	1st to 10th	Night	1 4 2 4 2 3 2 2 4 5% 71%	3851
	11th to 20th	Night	2 7% 3 5% 3 4 4 3 5% 6% 58%	3898
	21st to end	Night	1 7% 3 7% 3 3 4 4 6% 8% 54%	4252
November	1st to 10th	Night	1 8% 3 7% 4 4 4 4 7% 8% 52%	2600
	11th to 20th	Night	1 8% 4 7% 4 4 4 4 7% 9% 49%	2809
	21st to end	Night	1 6% 3 10% 5% 5% 5% 3 6% 6% 49%	2940
December	1st to 10th	Night	5% 3 8% 7% 3 3 2 4 6% 58%	4710
	11th to 20th	Night	6% 3 9% 5% 5% 4 4 7% 10% 47%	5280
	21st to end	Night	8% 6% 14% 8% 6% 5% 4 6% 8% 35%	6948

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	53% 2 8% 18% 17% 3	4099
	11th to 20th	Day	53% 2 9% 16% 14% 7%	4100
	21st to end	Day	41% 1 8% 18% 21% 11%	4510
February	1st to 10th	Day	53% 6% 7% 16% 14% 4	1800
	11th to 20th	Day	52% 4 8% 19% 12% 5%	1764
	21st to end	Day	53% 5% 8% 16% 13% 5%	1636
March	1st to 10th	Day	54% 2 4 16% 14% 10%	4949
	11th to 20th	Day	44% 2 8% 28% 15% 3	5000
	21st to end	Day	63% 2 9% 19% 6% 1	5486
April	1st to 10th	Day	48% 3 11% 20% 14% 3	2280
	11th to 20th	Day	53% 3 8% 22% 12% 2	2446
	21st to end	Day	48% 3 11% 26% 11% 1	2600
May	1st to 10th	Day	52% 1 6% 23% 15% 3	5880
	11th to 20th	Day	44% 1 7% 28% 19% 1	5844
	21st to end	Day	38% 2 7% 29% 23% 1	6699
June	1st to 10th	Day	34% 4 10% 29% 19% 4	2800
	11th to 20th	Day	30% 3 7% 21% 29% 11%	2800
	21st to end	Day	26% 3 4 19% 32% 17%	2800
July	1st to 10th	Day	26% 2 2 8% 21% 41%	5983
	11th to 20th	Day	37% 2 3 14% 28% 17%	5811
	21st to end	Day	34% 2 4 10% 30% 20%	6217
August	1st to 10th	Day	37% 3 6% 19% 22% 13%	4208
	11th to 20th	Day	31% 2 5% 19% 28% 15%	4197
	21st to end	Day	27% 3 6% 16% 30% 17%	4540
September	1st to 10th	Day	32% 3 5% 16% 28% 16%	2358
	11th to 20th	Day	30% 3 6% 23% 25% 13%	2200
	21st to end	Day	30% 3 5% 26% 28% 8%	2200
October	1st to 10th	Day	27% 2 3 25% 32% 10%	3341
	11th to 20th	Day	37% 2 5% 30% 22% 4	3250
	21st to end	Day	31% 2 8% 31% 24% 4	3548
November	1st to 10th	Day	34% 5% 10% 26% 20% 5%	1915
	11th to 20th	Day	36% 3 14% 23% 19% 4	1786
	21st to end	Day	39% 5% 9% 23% 18% 7%	1680
December	1st to 10th	Day	31% 3 10% 34% 19% 4	2700
	11th to 20th	Day	42% 3 14% 20% 19% 2	3080
	21st to end	Day	50% 2 4 16% 17% 10%	4072
January	1st to 10th	Night	52% 1 8% 14% 18% 6%	5867
	11th to 20th	Night	55% 2 7% 15% 17% 4	5880
	21st to end	Night	40% 1 7% 19% 21% 12%	6468
February	1st to 10th	Night	45% 5% 10% 21% 16% 4	2600
	11th to 20th	Night	43% 3 9% 20% 18% 6%	2533
	21st to end	Night	46% 4 8% 18% 16% 8%	1990
March	1st to 10th	Night	46% 2 5% 19% 17% 11%	4945
	11th to 20th	Night	37% 1 10% 33% 16% 2	5000
	21st to end	Night	47% 2 14% 25% 12% 1	5489
April	1st to 10th	Night	41% 4 11% 22% 15% 6%	2119
	11th to 20th	Night	39% 4 12% 26% 16% 2	1900
	21st to end	Night	41% 3 14% 28% 13% 1	1800
May	1st to 10th	Night	39% 2 10% 24% 23% 3	4097
	11th to 20th	Night	31% 2 8% 38% 19% 2	4075
	21st to end	Night	31% 2 8% 39% 18% 2	4181
June	1st to 10th	Night	25% 4 14% 31% 22% 4	1600
	11th to 20th	Night	22% 2 9% 24% 33% 10%	1600
	21st to end	Night	15% 3 4 21% 42% 16%	1600
July	1st to 10th	Night	18% 2 3 9% 24% 43%	3869
	11th to 20th	Night	24% 2 4 14% 37% 19%	4046
	21st to end	Night	23% 2 5% 16% 38% 16%	4344
August	1st to 10th	Night	24% 3 7% 22% 27% 17%	2928
	11th to 20th	Night	27% 2 7% 19% 28% 16%	2928
	21st to end	Night	14% 2 8% 23% 34% 20%	3368
September	1st to 10th	Night	18% 3 7% 24% 30% 18%	2038
	11th to 20th	Night	20% 2 11% 26% 29% 13%	2200
	21st to end	Night	20% 3 7% 28% 34% 8%	2200
October	1st to 10th	Night	20% 2 6% 27% 36% 10%	3851
	11th to 20th	Night	28% 2 7% 32% 25% 6%	3898
	21st to end	Night	30% 2 7% 31% 24% 7%	4252
November	1st to 10th	Night	32% 4 11% 24% 22% 6%	2600
	11th to 20th	Night	33% 4 15% 26% 18% 5%	2809
	21st to end	Night	36% 4 10% 22% 19% 9%	2940
December	1st to 10th	Night	32% 3 9% 31% 20% 5%	4710
	11th to 20th	Night	35% 3 13% 29% 18% 2	5281
	21st to end	Night	50% 2 6% 18% 13% 10%	6948

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	24% 26% 25% 15% 9% 1	300
	11th to 20th	Day	19% 31% 25% 16% 8%	300
	21st to end	Day	11% 29% 34% 20% 5% 1	330
February	1st to 10th	Day	31% 37% 21% 8% 3	300
	11th to 20th	Day	26% 35% 23% 12% 5%	300
	21st to end	Day	22% 41% 27% 8% 3	400
March	1st to 10th	Day	18% 43% 25% 10% 3 1	500
	11th to 20th	Day	18% 36% 30% 13% 3	500
	21st to end	Day	23% 40% 28% 9% 1	550
April	1st to 10th	Day	23% 38% 21% 12% 5% 1	500
	11th to 20th	Day	27% 39% 24% 7% 3 1	492
	21st to end	Day	23% 37% 23% 12% 5%	500
May	1st to 10th	Day	23% 30% 28% 13% 5% 1	503
	11th to 20th	Day	22% 29% 27% 15% 6% 1	528
	21st to end	Day	21% 22% 27% 17% 10% 2	692
June	1st to 10th	Day	12% 23% 30% 23% 10% 3	730
	11th to 20th	Day	15% 31% 30% 17% 7% 1	730
	21st to end	Day	10% 25% 35% 18% 9% 3	730
July	1st to 10th	Day	9% 22% 32% 24% 11% 2	602
	11th to 20th	Day	7% 23% 36% 21% 9% 3	524
	21st to end	Day	9% 16% 35% 25% 11% 3	575
August	1st to 10th	Day	12% 24% 29% 25% 8% 2	527
	11th to 20th	Day	8% 20% 36% 25% 9% 2	517
	21st to end	Day	11% 25% 30% 22% 11% 2	583
September	1st to 10th	Day	11% 22% 29% 24% 12% 3	530
	11th to 20th	Day	16% 30% 27% 14% 9% 3	530
	21st to end	Day	14% 24% 29% 22% 10% 2	530
October	1st to 10th	Day	15% 26% 28% 18% 11% 2	375
	11th to 20th	Day	22% 25% 22% 18% 12% 1	330
	21st to end	Day	22% 27% 26% 20% 5%	363
November	1st to 10th	Day	22% 33% 20% 17% 6% 1	330
	11th to 20th	Day	23% 27% 30% 13% 5% 3	330
	21st to end	Day	12% 26% 32% 21% 7% 2	330
December	1st to 10th	Day	21% 30% 22% 18% 8% 2	330
	11th to 20th	Day	21% 26% 33% 16% 3 1	321
	21st to end	Day	24% 32% 25% 11% 6% 1	330
January	1st to 10th	Night	13% 22% 26% 25% 12% 3	800
	11th to 20th	Night	13% 22% 28% 24% 12% 1	800
	21st to end	Night	7% 23% 33% 27% 8% 2	880
February	1st to 10th	Night	18% 26% 27% 20% 8% 2	800
	11th to 20th	Night	10% 30% 29% 22% 8% 1	784
	21st to end	Night	16% 25% 35% 20% 4	660
March	1st to 10th	Night	11% 28% 33% 19% 7% 2	800
	11th to 20th	Night	8% 25% 32% 24% 10% 1	800
	21st to end	Night	11% 31% 30% 21% 6%	880
April	1st to 10th	Night	14% 29% 29% 21% 7% 1	719
	11th to 20th	Night	15% 26% 34% 19% 6%	593
	21st to end	Night	12% 23% 28% 25% 11% 2	600
May	1st to 10th	Night	13% 17% 33% 27% 11% 1	600
	11th to 20th	Night	11% 13% 29% 31% 14% 3	591
	21st to end	Night	11% 16% 30% 28% 13% 2	650
June	1st to 10th	Night	6% 15% 33% 31% 15% 1	600
	11th to 20th	Night	7% 17% 33% 31% 11% 1	600
	21st to end	Night	3 10% 34% 31% 19% 3	600
July	1st to 10th	Night	4 8% 28% 33% 24% 4	585
	11th to 20th	Night	5% 6% 23% 44% 20% 3	582
	21st to end	Night	3 5% 20% 39% 31% 2	657
August	1st to 10th	Night	5% 6% 27% 40% 21% 2	597
	11th to 20th	Night	4 7% 24% 38% 25% 2	594
	21st to end	Night	5% 8% 27% 32% 27% 2	660
September	1st to 10th	Night	4 11% 25% 35% 22% 3	638
	11th to 20th	Night	7% 13% 29% 27% 19% 5%	800
	21st to end	Night	7% 16% 26% 28% 18% 6%	800
October	1st to 10th	Night	9% 22% 24% 30% 12% 3	800
	11th to 20th	Night	11% 20% 25% 27% 13% 4	800
	21st to end	Night	12% 23% 26% 25% 10% 3	880
November	1st to 10th	Night	13% 22% 29% 23% 12% 1	820
	11th to 20th	Night	14% 24% 30% 21% 9% 2	919
	21st to end	Night	11% 26% 29% 22% 10% 3	1050
December	1st to 10th	Night	14% 25% 28% 25% 7% 1	1050
	11th to 20th	Night	11% 25% 36% 21% 7% 1	1036
	21st to end	Night	16% 27% 30% 20% 6% 2	1087

Page generated at 2025-12-14 23:13:53. Version ac07

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