Fort Lancaster Scenic Overlook
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fort Lancaster Scenic Overlook clear sky chart from 2005-11-06 to 2024-11-05.

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	7% 4 2 4 3 3 3 3 5% 6% 60%	104922
	Night	7% 4 1 4 3 3 3 3 4 7% 62%	102789
Transparency	Day	25% 5% 8% 21% 24% 17%	104698
	Night	23% 5% 9% 22% 24% 17%	102603
Seeing	Day	9% 7% 26% 36% 19% 3	14816
	Night	9% 7% 33% 39% 12% 1	24783

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% 5% 2 4 3 2 2 2 4 5% 66%	2879
	11th to 20th	Day	6% 3 1 3 2 2 2 2 3 5% 71%	3170
	21st to end	Day	8% 5% 2 5% 4 3 4 3 4 6% 56%	3487
February	1st to 10th	Day	5% 7% 2 4 3 3 3 2 4 7% 59%	1900
	11th to 20th	Day	9% 5% 2 5% 3 3 2 3 5% 5% 57%	1849
	21st to end	Day	8% 5% 1 3 3 3 3 2 5% 5% 60%	1570
March	1st to 10th	Day	8% 6% 2 5% 4 3 3 3 5% 6% 54%	3130
	11th to 20th	Day	18% 7% 3 5% 3 3 3 3 4 6% 45%	3372
	21st to end	Day	4 5% 2 5% 4 4 4 3 5% 7% 56%	3927
April	1st to 10th	Day	6% 4 1 4 3 2 4 3 4 6% 62%	2280
	11th to 20th	Day	10% 5% 2 5% 3 2 3 3 4 6% 58%	2251
	21st to end	Day	7% 5% 1 4 3 3 3 3 4 5% 61%	2280
May	1st to 10th	Day	11% 5% 2 5% 3 3 3 3 5% 6% 55%	3894
	11th to 20th	Day	10% 5% 2 4 3 3 3 3 5% 6% 56%	4082
	21st to end	Day	8% 4 2 4 3 3 3 3 6% 8% 56%	4489
June	1st to 10th	Day	4 3 1 2 3 3 4 3 7% 8% 62%	2470
	11th to 20th	Day	5% 3 1 4 3 3 4 4 5% 9% 59%	2470
	21st to end	Day	6% 4 2 4 3 3 4 3 5% 8% 58%	2470
July	1st to 10th	Day	6% 3 1 4 4 3 4 3 5% 8% 59%	4120
	11th to 20th	Day	2 2 1 3 3 3 3 3 5% 9% 66%	4089
	21st to end	Day	6% 3 1 4 3 3 4 3 5% 7% 60%	4118
August	1st to 10th	Day	1 1 1 2 2 3 3 5% 7% 75%	3784
	11th to 20th	Day	4 2 1 3 2 3 3 3 5% 8% 67%	3726
	21st to end	Day	5% 4 1 5% 4 5% 5% 4 7% 10% 51%	4180
September	1st to 10th	Day	10% 5% 2 6% 3 5% 5% 4 6% 7% 47%	2222
	11th to 20th	Day	9% 5% 2 7% 4 5% 5% 4 5% 7% 46%	2090
	21st to end	Day	8% 4 1 5% 3 4 4 3 5% 6% 55%	2090
October	1st to 10th	Day	4 2 1 3 2 2 2 2 3 5% 74%	3480
	11th to 20th	Day	12% 5% 1 4 2 3 2 2 3 4 62%	3458
	21st to end	Day	7% 3 1 2 2 2 2 1 3 4 72%	3460
November	1st to 10th	Day	10% 4 2 4 2 2 3 2 3 6% 60%	1709
	11th to 20th	Day	7% 4 2 4 3 3 3 3 5% 5% 61%	1710
	21st to end	Day	9% 6% 2 6% 3 2 3 3 5% 5% 56%	1710
December	1st to 10th	Day	11% 7% 2 5% 3 3 3 2 4 5% 55%	1710
	11th to 20th	Day	7% 5% 2 5% 3 4 4 3 5% 7% 55%	2161
	21st to end	Day	10% 6% 1 3 2 2 2 2 3 4 66%	3135
January	1st to 10th	Night	5% 4 2 4 3 3 3 2 4 6% 66%	4104
	11th to 20th	Night	5% 6% 1 3 2 2 2 2 4 5% 68%	3800
	21st to end	Night	10% 7% 2 5% 3 2 3 3 4 7% 56%	4180
February	1st to 10th	Night	7% 6% 3 4 3 3 3 2 4 6% 60%	2280
	11th to 20th	Night	10% 6% 2 5% 4 3 2 3 4 5% 56%	2218
	21st to end	Night	8% 4 2 3 3 3 3 3 5% 7% 59%	1884
March	1st to 10th	Night	6% 5% 1 5% 3 3 4 3 5% 6% 59%	3734
	11th to 20th	Night	13% 8% 2 4 3 3 3 3 4 6% 50%	3590
	21st to end	Night	5% 4 2 5% 3 3 3 3 5% 7% 61%	3704
April	1st to 10th	Night	6% 4 1 3 3 3 4 4 5% 7% 61%	1900
	11th to 20th	Night	9% 5% 1 3 3 3 3 3 5% 6% 58%	1877
	21st to end	Night	8% 6% 1 3 2 2 2 3 4 5% 64%	1900
May	1st to 10th	Night	14% 5% 1 4 3 3 3 2 4 6% 55%	3074
	11th to 20th	Night	8% 5% 1 4 3 3 3 3 4 6% 61%	2823
	21st to end	Night	6% 3 1 3 3 3 3 3 6% 8% 59%	3098
June	1st to 10th	Night	3 1 1 2 3 3 4 4 7% 10% 64%	1710
	11th to 20th	Night	2 2 1 3 3 3 4 4 6% 11% 60%	1710
	21st to end	Night	4 3 1 4 3 3 3 3 7% 8% 62%	1710
July	1st to 10th	Night	5% 2 1 4 3 3 3 3 5% 8% 64%	2850
	11th to 20th	Night	1 1 2 2 2 2 3 5% 9% 72%	2875
	21st to end	Night	5% 3 1 3 3 3 3 3 5% 8% 64%	3445
August	1st to 10th	Night	1 1 1 2 2 2 2 2 4 8% 74%	3155
	11th to 20th	Night	3 1 1 2 3 2 3 3 6% 10% 67%	3113
	21st to end	Night	4 3 1 5% 3 4 4 4 6% 10% 54%	3487
September	1st to 10th	Night	8% 5% 1 4 4 4 3 3 5% 8% 54%	1957
	11th to 20th	Night	6% 4 2 5% 4 4 5% 3 6% 9% 52%	2090
	21st to end	Night	8% 3 2 3 3 3 3 3 7% 8% 57%	2090
October	1st to 10th	Night	3 2 1 2 2 2 2 2 3 5% 77%	3480
	11th to 20th	Night	11% 4 1 4 2 2 2 2 3 3 66%	3460
	21st to end	Night	6% 2 1 2 1 2 2 2 3 4 75%	4043
November	1st to 10th	Night	9% 5% 1 3 3 3 3 2 3 5% 63%	2470
	11th to 20th	Night	5% 4 2 4 3 3 3 3 4 6% 63%	2470
	21st to end	Night	9% 6% 2 4 2 3 3 3 4 6% 58%	2470
December	1st to 10th	Night	10% 5% 1 3 3 2 3 3 4 6% 60%	2470
	11th to 20th	Night	8% 6% 2 6% 4 3 3 3 4 5% 56%	3036
	21st to end	Night	8% 7% 2 4 2 2 2 2 3 5% 61%	4532

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	22% 3 4 13% 29% 29%	2880
	11th to 20th	Day	19% 3 6% 19% 32% 22%	3170
	21st to end	Day	29% 4 6% 21% 29% 12%	3487
February	1st to 10th	Day	27% 3 5% 15% 24% 25%	1900
	11th to 20th	Day	30% 4 5% 19% 22% 20%	1859
	21st to end	Day	26% 4 3 12% 30% 24%	1570
March	1st to 10th	Day	31% 4 4 10% 25% 25%	3130
	11th to 20th	Day	41% 4 6% 12% 18% 19%	3372
	21st to end	Day	26% 5% 6% 15% 20% 27%	3927
April	1st to 10th	Day	25% 3 6% 19% 22% 26%	2280
	11th to 20th	Day	28% 4 5% 17% 23% 22%	2254
	21st to end	Day	26% 4 6% 20% 25% 19%	2280
May	1st to 10th	Day	30% 5% 6% 12% 18% 28%	3894
	11th to 20th	Day	29% 6% 6% 18% 23% 18%	4086
	21st to end	Day	26% 7% 10% 20% 16% 21%	4489
June	1st to 10th	Day	18% 6% 11% 32% 25% 8%	2470
	11th to 20th	Day	23% 5% 11% 23% 27% 12%	2470
	21st to end	Day	25% 7% 11% 24% 24% 9%	2470
July	1st to 10th	Day	23% 7% 14% 38% 18% 1	4056
	11th to 20th	Day	17% 5% 15% 35% 25% 4	4020
	21st to end	Day	22% 5% 13% 28% 27% 5%	3988
August	1st to 10th	Day	10% 4 11% 34% 35% 5%	3772
	11th to 20th	Day	17% 5% 14% 39% 24% 2	3762
	21st to end	Day	26% 7% 16% 24% 22% 4	4179
September	1st to 10th	Day	35% 7% 11% 21% 18% 10%	2222
	11th to 20th	Day	36% 7% 10% 21% 20% 6%	2090
	21st to end	Day	28% 6% 11% 18% 22% 14%	2090
October	1st to 10th	Day	15% 3 5% 15% 22% 39%	3480
	11th to 20th	Day	29% 3 6% 14% 17% 31%	3458
	21st to end	Day	19% 2 3 19% 41% 16%	3460
November	1st to 10th	Day	28% 4 8% 20% 24% 17%	1709
	11th to 20th	Day	25% 3 10% 17% 24% 20%	1710
	21st to end	Day	31% 4 6% 15% 27% 17%	1710
December	1st to 10th	Day	33% 4 6% 18% 26% 14%	1710
	11th to 20th	Day	29% 4 7% 19% 22% 20%	2159
	21st to end	Day	25% 3 2 16% 30% 25%	3135
January	1st to 10th	Night	20% 5% 3 14% 31% 27%	4104
	11th to 20th	Night	21% 2 3 19% 28% 26%	3800
	21st to end	Night	29% 4 5% 18% 28% 15%	4180
February	1st to 10th	Night	26% 3 6% 16% 26% 24%	2280
	11th to 20th	Night	32% 4 5% 16% 23% 21%	2218
	21st to end	Night	26% 4 5% 13% 27% 25%	1884
March	1st to 10th	Night	25% 5% 5% 14% 27% 23%	3734
	11th to 20th	Night	36% 5% 7% 14% 21% 17%	3590
	21st to end	Night	24% 6% 10% 17% 16% 27%	3704
April	1st to 10th	Night	22% 6% 8% 20% 19% 24%	1900
	11th to 20th	Night	26% 5% 8% 20% 19% 23%	1877
	21st to end	Night	23% 5% 9% 23% 22% 17%	1900
May	1st to 10th	Night	30% 6% 8% 18% 19% 20%	3074
	11th to 20th	Night	25% 5% 10% 21% 21% 18%	2824
	21st to end	Night	22% 8% 12% 24% 17% 16%	3099
June	1st to 10th	Night	16% 7% 16% 34% 24% 5%	1710
	11th to 20th	Night	16% 7% 14% 27% 26% 9%	1710
	21st to end	Night	20% 6% 13% 27% 25% 9%	1710
July	1st to 10th	Night	20% 5% 17% 40% 16% 2	2805
	11th to 20th	Night	11% 5% 14% 41% 23% 6%	2821
	21st to end	Night	19% 4 14% 32% 26% 5%	3336
August	1st to 10th	Night	10% 4 11% 32% 38% 5%	3144
	11th to 20th	Night	13% 5% 18% 43% 19% 3	3143
	21st to end	Night	24% 7% 17% 26% 22% 4	3487
September	1st to 10th	Night	28% 6% 13% 22% 20% 10%	1957
	11th to 20th	Night	29% 9% 16% 20% 21% 6%	2090
	21st to end	Night	24% 5% 12% 24% 19% 16%	2090
October	1st to 10th	Night	12% 3 8% 15% 22% 40%	3480
	11th to 20th	Night	26% 3 6% 13% 22% 31%	3460
	21st to end	Night	16% 2 5% 26% 34% 16%	4043
November	1st to 10th	Night	26% 4 6% 20% 26% 17%	2470
	11th to 20th	Night	24% 3 8% 21% 24% 21%	2470
	21st to end	Night	28% 4 7% 17% 24% 20%	2470
December	1st to 10th	Night	26% 3 7% 21% 24% 17%	2470
	11th to 20th	Night	32% 4 5% 17% 23% 20%	3037
	21st to end	Night	27% 3 4 14% 30% 21%	4532

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	10% 13% 35% 34% 7% 1	270
	11th to 20th	Day	16% 10% 29% 35% 9% 1	270
	21st to end	Day	12% 10% 39% 29% 8% 1	297
February	1st to 10th	Day	17% 10% 33% 28% 11% 1	270
	11th to 20th	Day	15% 11% 40% 26% 6% 1	270
	21st to end	Day	17% 12% 44% 24% 3	225
March	1st to 10th	Day	12% 13% 48% 22% 5%	270
	11th to 20th	Day	19% 10% 39% 26% 6%	270
	21st to end	Day	8% 18% 46% 25% 3 1	359
April	1st to 10th	Day	8% 16% 46% 25% 4	460
	11th to 20th	Day	12% 20% 41% 24% 2	452
	21st to end	Day	9% 12% 48% 27% 5% 1	460
May	1st to 10th	Day	8% 12% 43% 32% 5%	518
	11th to 20th	Day	13% 9% 35% 33% 9% 1	675
	21st to end	Day	14% 9% 37% 33% 7%	734
June	1st to 10th	Day	6% 3 24% 51% 15% 2	680
	11th to 20th	Day	6% 2 29% 45% 17% 1	680
	21st to end	Day	5% 3 16% 48% 24% 4	680
July	1st to 10th	Day	9% 1 8% 43% 33% 7%	671
	11th to 20th	Day	3 1 8% 46% 38% 5%	650
	21st to end	Day	1 6% 49% 38% 6%	531
August	1st to 10th	Day	2 1 7% 40% 44% 5%	487
	11th to 20th	Day	8% 1 9% 38% 35% 10%	477
	21st to end	Day	5% 1 6% 39% 40% 9%	539
September	1st to 10th	Day	10% 2 7% 40% 33% 8%	432
	11th to 20th	Day	5% 8% 37% 39% 9%	300
	21st to end	Day	9% 2 12% 34% 32% 11%	300
October	1st to 10th	Day	5% 3 19% 42% 25% 5%	300
	11th to 20th	Day	13% 5% 22% 38% 22% 1	300
	21st to end	Day	13% 8% 30% 28% 18% 3	330
November	1st to 10th	Day	17% 6% 30% 30% 14% 2	282
	11th to 20th	Day	16% 10% 25% 26% 17% 7%	270
	21st to end	Day	14% 15% 34% 24% 9% 3	270
December	1st to 10th	Day	13% 9% 27% 36% 13% 2	270
	11th to 20th	Day	10% 14% 38% 24% 13% 1	270
	21st to end	Day	13% 9% 37% 31% 9%	297
January	1st to 10th	Night	10% 6% 36% 40% 8%	946
	11th to 20th	Night	14% 7% 30% 39% 9%	760
	21st to end	Night	13% 8% 36% 36% 6%	836
February	1st to 10th	Night	11% 9% 40% 33% 7%	760
	11th to 20th	Night	15% 10% 42% 27% 6%	744
	21st to end	Night	11% 13% 49% 26% 1	628
March	1st to 10th	Night	13% 12% 45% 27% 3	760
	11th to 20th	Night	11% 14% 45% 26% 4	641
	21st to end	Night	8% 16% 49% 23% 3	627
April	1st to 10th	Night	8% 11% 57% 21% 3	570
	11th to 20th	Night	11% 13% 53% 20% 2	563
	21st to end	Night	9% 14% 52% 22% 3	570
May	1st to 10th	Night	9% 9% 54% 25% 3	570
	11th to 20th	Night	9% 9% 45% 31% 5%	561
	21st to end	Night	8% 7% 52% 27% 6%	617
June	1st to 10th	Night	3 4 38% 50% 6%	570
	11th to 20th	Night	3 3 48% 40% 6%	570
	21st to end	Night	5% 2 30% 46% 16% 1	570
July	1st to 10th	Night	8% 1 16% 52% 21% 2	555
	11th to 20th	Night	3 1 15% 59% 22% 1	552
	21st to end	Night	3 1 10% 64% 22%	624
August	1st to 10th	Night	2 9% 60% 28% 1	567
	11th to 20th	Night	5% 1 9% 55% 28% 2	564
	21st to end	Night	5% 1 8% 50% 33% 2	627
September	1st to 10th	Night	8% 2 9% 48% 32% 2	570
	11th to 20th	Night	8% 1 12% 50% 27% 1	570
	21st to end	Night	9% 1 16% 48% 24% 2	570
October	1st to 10th	Night	5% 2 26% 49% 18%	570
	11th to 20th	Night	13% 6% 23% 49% 8%	570
	21st to end	Night	11% 7% 28% 37% 16% 1	786
November	1st to 10th	Night	13% 6% 28% 40% 13% 1	950
	11th to 20th	Night	8% 6% 31% 40% 14% 1	950
	21st to end	Night	10% 8% 34% 36% 11% 1	950
December	1st to 10th	Night	12% 7% 27% 43% 11% 1	950
	11th to 20th	Night	13% 7% 35% 37% 7%	950
	21st to end	Night	10% 7% 35% 39% 9%	1045

Page generated at 2024-11-03 01:11:27. Version ac07

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