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 2024-11-11.

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%	105125
	Night	1 6% 3 9% 5% 4 4 4 6% 7% 50%	102770
Transparency	Day	40% 3 7% 21% 19% 10%	104890
	Night	35% 3 9% 23% 21% 9%	102594
Seeing	Day	16% 29% 28% 17% 7% 2	15372
	Night	10% 20% 28% 27% 13% 2	25585

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	7% 8% 19% 9% 7% 5% 3 4 6% 32%	2858
	11th to 20th	Day	10% 7% 16% 10% 8% 4 3 5% 5% 32%	2860
	21st to end	Day	12% 5% 13% 6% 4 3 3 4 6% 44%	3146
February	1st to 10th	Day	1 13% 5% 14% 9% 6% 4 4 5% 6% 33%	1710
	11th to 20th	Day	10% 7% 16% 8% 4 4 4 4 7% 36%	1665
	21st to end	Day	9% 7% 16% 11% 7% 4 3 7% 6% 31%	1556
March	1st to 10th	Day	6% 8% 17% 9% 6% 5% 3 5% 6% 33%	3439
	11th to 20th	Day	9% 5% 15% 4 4 3 3 4 7% 46%	3490
	21st to end	Day	1 13% 9% 22% 8% 5% 5% 4 6% 6% 21%	3825
April	1st to 10th	Day	2 14% 6% 12% 6% 4 4 3 6% 7% 37%	2166
	11th to 20th	Day	2 17% 6% 13% 6% 4 4 3 5% 6% 34%	2319
	21st to end	Day	3 16% 6% 11% 5% 4 4 4 5% 7% 36%	2470
May	1st to 10th	Day	3 14% 9% 14% 5% 4 4 4 5% 6% 30%	4110
	11th to 20th	Day	4 11% 3 6% 5% 4 5% 4 7% 9% 43%	4071
	21st to end	Day	3 11% 4 7% 5% 5% 4 4 6% 8% 42%	4668
June	1st to 10th	Day	5% 7% 2 6% 5% 5% 5% 4 7% 7% 47%	2660
	11th to 20th	Day	5% 7% 2 5% 4 3 4 3 5% 8% 53%	2660
	21st to end	Day	4 5% 1 4 4 4 4 4 6% 8% 57%	2660
July	1st to 10th	Day	3 3 1 4 3 4 4 3 4 6% 64%	4221
	11th to 20th	Day	4 5% 2 7% 6% 6% 7% 5% 7% 8% 42%	4110
	21st to end	Day	6% 5% 2 6% 5% 5% 5% 4 6% 8% 49%	4454
August	1st to 10th	Day	6% 5% 2 8% 5% 5% 6% 4 6% 7% 45%	4092
	11th to 20th	Day	3 3 2 6% 5% 5% 6% 4 7% 8% 50%	4028
	21st to end	Day	3 3 2 5% 4 4 4 4 6% 6% 59%	4402
September	1st to 10th	Day	6% 5% 2 6% 4 5% 4 3 5% 5% 55%	2240
	11th to 20th	Day	5% 6% 2 5% 4 4 4 4 5% 7% 56%	2090
	21st to end	Day	6% 8% 2 6% 3 3 3 3 4 5% 60%	2090
October	1st to 10th	Day	3 8% 2 4 3 3 3 3 4 5% 63%	3239
	11th to 20th	Day	5% 10% 3 7% 4 3 4 3 5% 5% 50%	3150
	21st to end	Day	1 7% 3 8% 3 3 3 3 5% 7% 55%	3438
November	1st to 10th	Day	2 9% 4 10% 4 3 4 3 8% 7% 48%	1822
	11th to 20th	Day	1 12% 4 6% 4 3 4 3 6% 7% 48%	1616
	21st to end	Day	1 7% 3 12% 7% 6% 5% 4 5% 7% 44%	1520
December	1st to 10th	Day	1 8% 5% 11% 5% 6% 4 4 5% 8% 41%	1520
	11th to 20th	Day	10% 4 12% 7% 5% 5% 5% 7% 9% 36%	1926
	21st to end	Day	7% 6% 13% 7% 5% 4 4 5% 7% 41%	2834
January	1st to 10th	Night	6% 4 17% 12% 6% 4 3 5% 6% 36%	4097
	11th to 20th	Night	8% 7% 17% 8% 10% 4 3 5% 6% 32%	4110
	21st to end	Night	7% 6% 15% 6% 5% 4 4 6% 8% 39%	4521
February	1st to 10th	Night	10% 6% 12% 6% 5% 5% 4 6% 8% 37%	2470
	11th to 20th	Night	6% 5% 13% 8% 5% 5% 4 7% 8% 40%	2402
	21st to end	Night	6% 4 14% 11% 5% 5% 3 5% 7% 39%	1894
March	1st to 10th	Night	4 4 10% 8% 6% 5% 5% 8% 9% 40%	3435
	11th to 20th	Night	4 3 11% 4 4 4 4 6% 9% 51%	3490
	21st to end	Night	9% 6% 17% 6% 5% 5% 4 6% 6% 36%	3828
April	1st to 10th	Night	2 11% 5% 9% 5% 5% 5% 3 4 6% 45%	2013
	11th to 20th	Night	1 12% 4 9% 6% 4 4 3 7% 8% 43%	1804
	21st to end	Night	2 12% 5% 9% 4 4 4 4 5% 8% 42%	1710
May	1st to 10th	Night	2 9% 7% 12% 5% 4 6% 5% 6% 8% 36%	2860
	11th to 20th	Night	3 5% 2 4 4 4 4 3 7% 8% 55%	2834
	21st to end	Night	3 7% 3 6% 4 4 4 4 7% 9% 49%	2901
June	1st to 10th	Night	3 4 2 4 4 4 4 5% 7% 10% 52%	1520
	11th to 20th	Night	3 3 1 4 3 3 4 3 4 8% 64%	1520
	21st to end	Night	1 2 1 3 2 2 3 3 5% 8% 69%	1520
July	1st to 10th	Night	2 2 1 3 3 3 3 2 5% 5% 72%	2730
	11th to 20th	Night	2 3 1 5% 4 4 5% 5% 8% 10% 53%	2860
	21st to end	Night	2 2 1 4 4 4 6% 5% 7% 7% 58%	3109
August	1st to 10th	Night	2 3 1 4 4 4 6% 4 6% 8% 58%	2847
	11th to 20th	Night	3 3 2 5% 4 4 4 3 6% 6% 60%	2811
	21st to end	Night	1 1 1 2 2 2 3 3 4 7% 74%	3265
September	1st to 10th	Night	2 3 1 3 3 2 3 4 5% 7% 66%	1936
	11th to 20th	Night	2 3 1 4 2 2 3 4 6% 7% 65%	2090
	21st to end	Night	3 5% 1 4 3 2 3 3 5% 5% 68%	2090
October	1st to 10th	Night	1 4 2 4 2 3 2 2 4 4 71%	3733
	11th to 20th	Night	2 7% 3 5% 3 4 3 3 5% 6% 58%	3778
	21st to end	Night	1 8% 3 7% 3 3 4 4 6% 8% 53%	4120
November	1st to 10th	Night	1 9% 3 7% 4 3 4 4 7% 8% 51%	2473
	11th to 20th	Night	1 8% 4 7% 4 4 4 4 7% 8% 49%	2547
	21st to end	Night	1 7% 3 10% 6% 5% 5% 3 6% 6% 49%	2660
December	1st to 10th	Night	1 8% 5% 10% 7% 4 5% 3 6% 7% 44%	2660
	11th to 20th	Night	8% 3 11% 6% 5% 4 4 7% 11% 40%	3271
	21st to end	Night	7% 4 12% 10% 6% 5% 5% 6% 8% 37%	4861

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	56% 3 8% 16% 15% 2	2859
	11th to 20th	Day	55% 3 13% 18% 8% 4	2860
	21st to end	Day	45% 2 12% 23% 13% 5%	3146
February	1st to 10th	Day	54% 6% 7% 16% 14% 3	1710
	11th to 20th	Day	50% 4 9% 19% 13% 5%	1674
	21st to end	Day	55% 5% 8% 16% 12% 3	1556
March	1st to 10th	Day	56% 2 6% 17% 11% 8%	3439
	11th to 20th	Day	43% 3 11% 31% 9% 4	3490
	21st to end	Day	67% 3 7% 16% 6% 2	3825
April	1st to 10th	Day	49% 4 11% 19% 13% 4	2166
	11th to 20th	Day	54% 3 9% 22% 11% 2	2322
	21st to end	Day	48% 4 11% 26% 10% 1	2470
May	1st to 10th	Day	57% 2 5% 19% 13% 3	4110
	11th to 20th	Day	39% 2 7% 34% 17% 1	4074
	21st to end	Day	41% 2 7% 28% 19% 1	4668
June	1st to 10th	Day	35% 4 10% 29% 17% 4	2660
	11th to 20th	Day	31% 3 7% 22% 28% 10%	2660
	21st to end	Day	26% 3 4 19% 31% 17%	2660
July	1st to 10th	Day	22% 2 3 9% 17% 46%	4157
	11th to 20th	Day	38% 2 4 15% 22% 19%	4041
	21st to end	Day	33% 2 5% 10% 27% 22%	4314
August	1st to 10th	Day	37% 3 6% 19% 22% 13%	4078
	11th to 20th	Day	31% 2 5% 18% 28% 15%	4067
	21st to end	Day	26% 3 6% 16% 31% 18%	4401
September	1st to 10th	Day	31% 3 5% 15% 28% 17%	2240
	11th to 20th	Day	30% 3 7% 23% 24% 13%	2090
	21st to end	Day	29% 3 5% 26% 29% 8%	2090
October	1st to 10th	Day	27% 2 3 25% 32% 10%	3239
	11th to 20th	Day	37% 2 5% 30% 22% 4	3150
	21st to end	Day	31% 2 8% 31% 24% 4	3438
November	1st to 10th	Day	36% 5% 10% 25% 19% 5%	1822
	11th to 20th	Day	35% 4 13% 23% 20% 5%	1616
	21st to end	Day	40% 5% 10% 21% 17% 7%	1520
December	1st to 10th	Day	42% 6% 15% 18% 13% 7%	1520
	11th to 20th	Day	46% 3 11% 22% 17% 1	1924
	21st to end	Day	45% 3 5% 17% 16% 15%	2834
January	1st to 10th	Night	52% 2 9% 15% 18% 4	4097
	11th to 20th	Night	56% 3 9% 16% 11% 4	4110
	21st to end	Night	47% 2 10% 21% 14% 7%	4521
February	1st to 10th	Night	46% 6% 10% 20% 16% 3	2470
	11th to 20th	Night	43% 4 9% 20% 19% 6%	2403
	21st to end	Night	47% 4 9% 18% 16% 6%	1894
March	1st to 10th	Night	45% 3 7% 22% 15% 9%	3435
	11th to 20th	Night	31% 2 14% 36% 13% 3	3490
	21st to end	Night	51% 3 10% 23% 11% 2	3828
April	1st to 10th	Night	42% 5% 11% 22% 14% 7%	2013
	11th to 20th	Night	40% 4 13% 27% 14% 2	1804
	21st to end	Night	42% 3 14% 28% 13% 1	1710
May	1st to 10th	Night	45% 2 9% 22% 17% 4	2860
	11th to 20th	Night	26% 2 10% 41% 17% 3	2835
	21st to end	Night	34% 2 10% 33% 19% 3	2901
June	1st to 10th	Night	26% 4 15% 30% 21% 4	1520
	11th to 20th	Night	22% 2 10% 24% 32% 9%	1520
	21st to end	Night	15% 3 4 21% 41% 16%	1520
July	1st to 10th	Night	16% 2 4 10% 21% 46%	2685
	11th to 20th	Night	24% 2 5% 17% 32% 19%	2806
	21st to end	Night	24% 3 8% 17% 30% 18%	3011
August	1st to 10th	Night	24% 3 8% 22% 27% 16%	2838
	11th to 20th	Night	27% 2 7% 19% 28% 16%	2838
	21st to end	Night	13% 2 8% 23% 35% 20%	3265
September	1st to 10th	Night	18% 3 7% 23% 30% 18%	1936
	11th to 20th	Night	19% 2 11% 26% 28% 14%	2090
	21st to end	Night	20% 3 6% 28% 36% 7%	2090
October	1st to 10th	Night	20% 2 6% 27% 36% 10%	3733
	11th to 20th	Night	28% 2 7% 32% 25% 6%	3778
	21st to end	Night	30% 2 8% 30% 23% 7%	4120
November	1st to 10th	Night	33% 4 12% 23% 22% 7%	2473
	11th to 20th	Night	33% 4 15% 25% 18% 5%	2547
	21st to end	Night	36% 4 10% 21% 19% 9%	2660
December	1st to 10th	Night	41% 5% 14% 20% 14% 7%	2660
	11th to 20th	Night	40% 4 12% 26% 15% 3	3272
	21st to end	Night	47% 3 6% 18% 12% 12%	4861

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% 25% 25% 16% 10% 1	270
	11th to 20th	Day	18% 32% 25% 17% 9%	270
	21st to end	Day	10% 30% 34% 21% 4 1	297
February	1st to 10th	Day	27% 38% 23% 9% 3	270
	11th to 20th	Day	23% 35% 24% 12% 6%	270
	21st to end	Day	21% 43% 27% 7% 2	368
March	1st to 10th	Day	19% 44% 24% 10% 2	460
	11th to 20th	Day	16% 35% 31% 14% 3	460
	21st to end	Day	21% 41% 29% 8% 1	506
April	1st to 10th	Day	24% 38% 21% 12% 5% 1	460
	11th to 20th	Day	27% 39% 23% 6% 3 1	452
	21st to end	Day	23% 37% 22% 13% 5%	460
May	1st to 10th	Day	24% 31% 29% 11% 4 1	463
	11th to 20th	Day	20% 27% 29% 16% 6% 1	488
	21st to end	Day	21% 23% 27% 16% 10% 2	642
June	1st to 10th	Day	11% 24% 30% 23% 11% 2	680
	11th to 20th	Day	14% 31% 30% 17% 7% 1	680
	21st to end	Day	9% 25% 35% 19% 10% 3	680
July	1st to 10th	Day	8% 22% 31% 25% 11% 3	558
	11th to 20th	Day	6% 23% 37% 21% 9% 3	484
	21st to end	Day	10% 15% 34% 25% 12% 4	531
August	1st to 10th	Day	10% 23% 30% 27% 8% 2	487
	11th to 20th	Day	8% 21% 36% 24% 9% 3	477
	21st to end	Day	9% 27% 29% 23% 10% 2	539
September	1st to 10th	Day	11% 23% 28% 24% 11% 3	490
	11th to 20th	Day	15% 32% 27% 14% 9% 3	490
	21st to end	Day	14% 25% 29% 21% 10% 2	490
October	1st to 10th	Day	15% 25% 28% 18% 12% 2	343
	11th to 20th	Day	18% 24% 24% 20% 13% 1	300
	21st to end	Day	22% 29% 24% 19% 5%	330
November	1st to 10th	Day	24% 32% 21% 16% 6% 1	300
	11th to 20th	Day	20% 29% 27% 14% 6% 3	270
	21st to end	Day	10% 26% 33% 22% 8% 2	270
December	1st to 10th	Day	18% 31% 24% 18% 8% 2	270
	11th to 20th	Day	19% 27% 32% 18% 4 1	270
	21st to end	Day	21% 35% 25% 12% 6% 1	297
January	1st to 10th	Night	12% 22% 25% 26% 13% 3	760
	11th to 20th	Night	13% 22% 27% 25% 12% 1	760
	21st to end	Night	7% 24% 31% 28% 9% 2	836
February	1st to 10th	Night	15% 26% 28% 21% 8% 2	760
	11th to 20th	Night	9% 30% 28% 23% 8% 1	744
	21st to end	Night	16% 26% 34% 20% 4	628
March	1st to 10th	Night	12% 29% 32% 19% 7% 2	760
	11th to 20th	Night	6% 25% 33% 25% 11% 1	760
	21st to end	Night	10% 31% 31% 21% 6%	836
April	1st to 10th	Night	14% 29% 29% 20% 7% 1	683
	11th to 20th	Night	15% 27% 32% 19% 6%	563
	21st to end	Night	12% 23% 27% 25% 11% 2	570
May	1st to 10th	Night	13% 17% 33% 25% 10% 1	570
	11th to 20th	Night	9% 12% 29% 33% 14% 3	561
	21st to end	Night	11% 17% 30% 27% 13% 2	617
June	1st to 10th	Night	6% 15% 33% 30% 15% 1	570
	11th to 20th	Night	7% 18% 32% 31% 11% 1	570
	21st to end	Night	3 10% 34% 31% 20% 3	570
July	1st to 10th	Night	4 7% 26% 33% 25% 4	555
	11th to 20th	Night	5% 6% 22% 44% 21% 3	552
	21st to end	Night	3 4 19% 39% 32% 3	624
August	1st to 10th	Night	5% 5% 26% 40% 22% 2	567
	11th to 20th	Night	4 6% 24% 37% 26% 2	564
	21st to end	Night	5% 7% 27% 30% 28% 3	627
September	1st to 10th	Night	4 11% 23% 35% 23% 4	606
	11th to 20th	Night	7% 13% 27% 27% 20% 6%	760
	21st to end	Night	7% 16% 25% 27% 18% 6%	760
October	1st to 10th	Night	8% 22% 24% 31% 13% 3	760
	11th to 20th	Night	9% 20% 26% 28% 14% 4	760
	21st to end	Night	12% 24% 24% 25% 11% 3	836
November	1st to 10th	Night	13% 22% 27% 24% 13% 2	780
	11th to 20th	Night	13% 24% 29% 23% 10% 2	833
	21st to end	Night	9% 27% 26% 24% 11% 3	950
December	1st to 10th	Night	13% 25% 28% 25% 8% 1	950
	11th to 20th	Night	10% 25% 34% 22% 7% 1	950
	21st to end	Night	15% 27% 30% 21% 6% 2	1033

Page generated at 2024-11-08 04:44:52. Version ac07

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