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Smokey Jack Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Smokey Jack Observatory clear sky chart from 2005-11-06 to 2024-12-06.

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 4 2 4 3 4 4 4 6% 8% 57%	105344
	Night	2 4 2 4 3 3 3 3 6% 8% 62%	103086
Transparency	Day	22% 6% 11% 24% 25% 11%	105095
	Night	20% 6% 13% 27% 25% 9%	102926
Seeing	Day	9% 13% 29% 27% 16% 5%	15530
	Night	6% 10% 33% 33% 16% 2	25619

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	1 3 1 5% 5% 3 3 3 6% 9% 62%	2538
	11th to 20th	Day	3 1 4 2 3 3 4 6% 9% 66%	2793
	21st to end	Day	1 7% 4 5% 3 3 3 3 5% 8% 58%	3146
February	1st to 10th	Day	5% 3 6% 3 2 3 3 6% 7% 61%	1710
	11th to 20th	Day	1 3 2 4 2 2 3 3 5% 8% 67%	1843
	21st to end	Day	6% 3 6% 3 3 3 4 5% 8% 59%	1570
March	1st to 10th	Day	1 5% 4 5% 2 3 3 3 5% 8% 64%	3157
	11th to 20th	Day	3 13% 6% 4 4 3 4 4 6% 7% 46%	3490
	21st to end	Day	1 7% 2 5% 3 3 4 3 5% 8% 58%	4027
April	1st to 10th	Day	2 6% 1 4 3 4 4 4 6% 8% 58%	2280
	11th to 20th	Day	4 8% 2 5% 4 4 4 3 6% 7% 52%	2251
	21st to end	Day	4 8% 2 5% 5% 4 4 4 7% 9% 50%	2280
May	1st to 10th	Day	5% 11% 2 5% 4 4 4 4 5% 6% 50%	3857
	11th to 20th	Day	6% 6% 2 5% 4 4 5% 4 8% 9% 48%	4312
	21st to end	Day	3 3 1 3 3 3 4 5% 7% 10% 59%	4825
June	1st to 10th	Day	4 3 1 4 3 4 5% 5% 8% 11% 51%	2660
	11th to 20th	Day	3 3 1 3 3 4 5% 5% 7% 8% 59%	2660
	21st to end	Day	3 3 2 3 4 5% 6% 6% 9% 8% 51%	2660
July	1st to 10th	Day	4 3 1 4 3 4 4 5% 7% 9% 56%	4430
	11th to 20th	Day	3 2 1 5% 6% 7% 8% 6% 9% 8% 44%	4430
	21st to end	Day	5% 3 2 5% 5% 5% 6% 6% 7% 9% 47%	4500
August	1st to 10th	Day	4 3 2 6% 6% 7% 7% 7% 9% 10% 39%	4045
	11th to 20th	Day	3 3 1 3 4 4 6% 6% 9% 10% 51%	3726
	21st to end	Day	5% 5% 2 5% 5% 4 6% 6% 8% 11% 44%	4180
September	1st to 10th	Day	5% 4 1 4 4 4 5% 5% 7% 8% 53%	2280
	11th to 20th	Day	5% 2 1 3 2 4 3 3 6% 7% 63%	2275
	21st to end	Day	5% 3 1 3 3 3 3 3 4 5% 68%	2085
October	1st to 10th	Day	3 2 1 2 2 2 3 2 4 4 75%	3170
	11th to 20th	Day	2 3 1 3 2 2 3 3 5% 9% 67%	3150
	21st to end	Day	2 3 1 2 1 2 2 2 3 6% 76%	3421
November	1st to 10th	Day	1 4 2 2 2 2 2 3 4 7% 71%	1763
	11th to 20th	Day	3 1 3 2 2 3 2 4 8% 73%	1800
	21st to end	Day	1 5% 1 4 3 3 2 2 5% 6% 68%	1750
December	1st to 10th	Day	3 1 3 2 2 3 3 6% 6% 70%	1560
	11th to 20th	Day	1 4 2 4 2 2 2 3 6% 9% 65%	1926
	21st to end	Day	1 4 3 6% 3 3 4 4 6% 6% 62%	2794
January	1st to 10th	Night	4 3 7% 4 3 3 3 5% 7% 61%	4417
	11th to 20th	Night	2 1 2 2 3 3 3 6% 7% 69%	4206
	21st to end	Night	4 2 5% 3 3 3 3 5% 7% 63%	4521
February	1st to 10th	Night	5% 3 6% 3 2 2 3 4 6% 66%	2470
	11th to 20th	Night	1 5% 1 4 3 3 3 4 5% 7% 65%	2223
	21st to end	Night	4 2 5% 3 3 3 3 4 7% 66%	1884
March	1st to 10th	Night	1 6% 2 4 2 2 2 3 5% 7% 68%	3703
	11th to 20th	Night	2 10% 4 4 2 3 3 3 5% 6% 57%	3490
	21st to end	Night	1 6% 2 4 3 3 4 3 5% 7% 63%	3619
April	1st to 10th	Night	1 5% 2 3 2 2 3 2 6% 8% 66%	1900
	11th to 20th	Night	4 7% 2 5% 3 2 3 3 5% 7% 59%	1877
	21st to end	Night	3 6% 2 5% 3 3 4 3 5% 7% 58%	1900
May	1st to 10th	Night	5% 7% 2 6% 3 3 3 2 4 5% 61%	3111
	11th to 20th	Night	8% 8% 2 4 3 3 3 4 6% 8% 53%	2589
	21st to end	Night	4 3 1 2 2 2 3 3 5% 6% 68%	2762
June	1st to 10th	Night	4 3 1 3 3 3 4 3 6% 8% 62%	1520
	11th to 20th	Night	2 3 1 3 2 3 3 2 4 8% 69%	1520
	21st to end	Night	3 4 1 4 4 4 4 6% 8% 8% 54%	1520
July	1st to 10th	Night	5% 3 1 4 4 4 5% 4 7% 8% 54%	2540
	11th to 20th	Night	3 2 1 3 3 4 5% 6% 10% 14% 48%	2540
	21st to end	Night	3 3 2 5% 4 5% 5% 4 8% 9% 51%	3045
August	1st to 10th	Night	4 4 2 7% 5% 5% 6% 6% 10% 13% 37%	2891
	11th to 20th	Night	3 2 1 3 3 3 5% 5% 9% 14% 51%	3113
	21st to end	Night	3 5% 2 6% 4 4 6% 6% 8% 12% 44%	3487
September	1st to 10th	Night	4 5% 2 4 4 4 5% 3 6% 9% 55%	1900
	11th to 20th	Night	5% 4 1 3 2 3 3 3 5% 8% 64%	1905
	21st to end	Night	4 3 1 3 2 3 3 3 5% 6% 67%	2090
October	1st to 10th	Night	3 2 1 2 2 2 2 2 3 4 77%	3800
	11th to 20th	Night	3 2 1 3 3 2 3 3 6% 7% 68%	3778
	21st to end	Night	2 3 1 2 2 2 2 2 3 4 78%	4120
November	1st to 10th	Night	1 3 1 3 2 2 2 2 5% 6% 73%	2518
	11th to 20th	Night	1 2 1 2 1 2 3 3 5% 5% 76%	2600
	21st to end	Night	1 5% 2 2 2 2 2 2 5% 7% 69%	2646
December	1st to 10th	Night	1 2 1 4 2 3 3 3 4 7% 70%	2737
	11th to 20th	Night	1 3 2 4 2 2 3 3 7% 9% 63%	3271
	21st to end	Night	4 2 5% 3 3 4 3 6% 8% 61%	4873

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	16% 6% 15% 30% 26% 6%	2539
	11th to 20th	Day	15% 4 16% 35% 26% 4	2793
	21st to end	Day	25% 4 11% 31% 23% 6%	3146
February	1st to 10th	Day	21% 4 13% 30% 22% 9%	1710
	11th to 20th	Day	17% 3 11% 27% 31% 10%	1853
	21st to end	Day	23% 3 8% 24% 28% 14%	1570
March	1st to 10th	Day	18% 4 7% 21% 38% 13%	3157
	11th to 20th	Day	35% 6% 8% 32% 16% 4	3490
	21st to end	Day	23% 6% 10% 34% 23% 3	4027
April	1st to 10th	Day	23% 5% 12% 25% 24% 12%	2280
	11th to 20th	Day	30% 3 8% 27% 22% 9%	2254
	21st to end	Day	29% 5% 10% 28% 22% 5%	2280
May	1st to 10th	Day	32% 5% 9% 20% 22% 13%	3857
	11th to 20th	Day	30% 7% 13% 25% 19% 7%	4316
	21st to end	Day	18% 6% 9% 21% 32% 15%	4825
June	1st to 10th	Day	22% 8% 14% 23% 22% 10%	2660
	11th to 20th	Day	20% 6% 9% 17% 25% 23%	2660
	21st to end	Day	24% 8% 11% 23% 22% 13%	2660
July	1st to 10th	Day	21% 7% 11% 15% 22% 24%	4361
	11th to 20th	Day	27% 10% 15% 28% 14% 6%	4355
	21st to end	Day	27% 9% 16% 19% 16% 14%	4358
August	1st to 10th	Day	33% 12% 21% 19% 12% 4	4031
	11th to 20th	Day	22% 11% 17% 17% 22% 11%	3762
	21st to end	Day	27% 10% 17% 21% 21% 4	4179
September	1st to 10th	Day	26% 6% 11% 21% 23% 12%	2280
	11th to 20th	Day	19% 5% 12% 17% 31% 15%	2275
	21st to end	Day	19% 4 7% 25% 34% 11%	2085
October	1st to 10th	Day	13% 3 5% 18% 36% 23%	3170
	11th to 20th	Day	14% 5% 9% 32% 32% 9%	3150
	21st to end	Day	12% 1 5% 21% 43% 17%	3421
November	1st to 10th	Day	13% 3 9% 23% 39% 13%	1763
	11th to 20th	Day	12% 4 8% 34% 32% 11%	1800
	21st to end	Day	18% 3 7% 25% 32% 14%	1750
December	1st to 10th	Day	14% 4 15% 33% 26% 8%	1560
	11th to 20th	Day	15% 4 15% 29% 28% 9%	1924
	21st to end	Day	19% 7% 11% 24% 25% 13%	2794
January	1st to 10th	Night	21% 5% 11% 30% 27% 6%	4417
	11th to 20th	Night	14% 3 12% 41% 25% 5%	4206
	21st to end	Night	20% 5% 15% 32% 23% 5%	4521
February	1st to 10th	Night	21% 3 13% 31% 22% 10%	2470
	11th to 20th	Night	20% 3 12% 29% 28% 8%	2223
	21st to end	Night	18% 3 8% 27% 32% 12%	1884
March	1st to 10th	Night	18% 2 7% 25% 38% 10%	3703
	11th to 20th	Night	27% 5% 12% 33% 20% 4	3490
	21st to end	Night	22% 4 16% 35% 21% 2	3619
April	1st to 10th	Night	18% 4 13% 30% 27% 8%	1900
	11th to 20th	Night	26% 4 10% 27% 26% 6%	1877
	21st to end	Night	26% 4 13% 32% 20% 5%	1900
May	1st to 10th	Night	24% 5% 10% 25% 25% 11%	3111
	11th to 20th	Night	29% 6% 14% 28% 17% 6%	2590
	21st to end	Night	16% 5% 12% 26% 29% 11%	2762
June	1st to 10th	Night	21% 6% 17% 23% 19% 14%	1520
	11th to 20th	Night	16% 4 11% 23% 25% 21%	1520
	21st to end	Night	24% 7% 13% 21% 22% 13%	1520
July	1st to 10th	Night	25% 10% 12% 19% 19% 15%	2500
	11th to 20th	Night	21% 9% 28% 28% 10% 4	2492
	21st to end	Night	22% 13% 22% 20% 16% 7%	2950
August	1st to 10th	Night	33% 15% 24% 15% 9% 5%	2882
	11th to 20th	Night	19% 11% 29% 17% 19% 6%	3143
	21st to end	Night	28% 11% 19% 24% 14% 3	3487
September	1st to 10th	Night	26% 5% 14% 25% 21% 8%	1900
	11th to 20th	Night	20% 6% 12% 21% 27% 15%	1905
	21st to end	Night	18% 4 10% 25% 34% 8%	2090
October	1st to 10th	Night	13% 4 8% 25% 34% 16%	3800
	11th to 20th	Night	14% 6% 12% 30% 29% 9%	3778
	21st to end	Night	12% 3 5% 26% 39% 15%	4120
November	1st to 10th	Night	12% 3 9% 28% 35% 13%	2518
	11th to 20th	Night	10% 3 8% 34% 31% 14%	2600
	21st to end	Night	16% 3 9% 24% 33% 13%	2646
December	1st to 10th	Night	16% 4 15% 32% 25% 8%	2737
	11th to 20th	Night	16% 5% 14% 26% 30% 8%	3272
	21st to end	Night	19% 7% 12% 25% 25% 12%	4873

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	14% 17% 34% 20% 10% 4	270
	11th to 20th	Day	15% 17% 37% 24% 5% 1	270
	21st to end	Day	4 15% 41% 27% 10% 3	297
February	1st to 10th	Day	11% 23% 46% 16% 3 1	270
	11th to 20th	Day	10% 30% 39% 16% 3 1	270
	21st to end	Day	18% 21% 40% 16% 5%	225
March	1st to 10th	Day	14% 20% 38% 20% 7% 1	284
	11th to 20th	Day	13% 21% 35% 22% 8% 2	460
	21st to end	Day	16% 27% 36% 17% 4	506
April	1st to 10th	Day	16% 23% 34% 20% 5% 1	460
	11th to 20th	Day	18% 26% 35% 15% 5% 1	452
	21st to end	Day	15% 23% 38% 16% 7% 1	460
May	1st to 10th	Day	15% 19% 36% 20% 8% 2	494
	11th to 20th	Day	12% 10% 27% 32% 16% 3	675
	21st to end	Day	8% 14% 30% 28% 16% 4	734
June	1st to 10th	Day	6% 9% 27% 30% 22% 7%	680
	11th to 20th	Day	5% 10% 32% 31% 16% 6%	680
	21st to end	Day	5% 7% 29% 30% 23% 6%	680
July	1st to 10th	Day	7% 3 18% 37% 26% 9%	671
	11th to 20th	Day	4 2 12% 36% 36% 11%	668
	21st to end	Day	7% 2 12% 33% 33% 13%	564
August	1st to 10th	Day	7% 3 16% 36% 26% 12%	487
	11th to 20th	Day	5% 1 22% 38% 25% 8%	477
	21st to end	Day	8% 3 20% 36% 24% 8%	539
September	1st to 10th	Day	6% 5% 22% 32% 25% 9%	490
	11th to 20th	Day	6% 9% 30% 33% 19% 4	485
	21st to end	Day	7% 7% 21% 29% 28% 8%	300
October	1st to 10th	Day	9% 10% 26% 23% 24% 8%	300
	11th to 20th	Day	8% 14% 30% 28% 14% 5%	300
	21st to end	Day	12% 14% 30% 28% 14% 3	330
November	1st to 10th	Day	8% 20% 31% 26% 12% 3	300
	11th to 20th	Day	5% 19% 40% 23% 8% 4	300
	21st to end	Day	6% 16% 38% 31% 7% 2	300
December	1st to 10th	Day	11% 20% 34% 23% 11% 1	285
	11th to 20th	Day	9% 22% 39% 18% 10% 2	270
	21st to end	Day	12% 24% 42% 18% 4 1	297
January	1st to 10th	Night	5% 18% 36% 29% 10% 2	950
	11th to 20th	Night	5% 19% 39% 26% 8% 2	817
	21st to end	Night	3 12% 45% 32% 8% 1	836
February	1st to 10th	Night	4 13% 52% 25% 5%	760
	11th to 20th	Night	5% 14% 51% 23% 7%	744
	21st to end	Night	4 14% 54% 26% 2	628
March	1st to 10th	Night	6% 17% 42% 28% 6% 1	760
	11th to 20th	Night	6% 8% 39% 35% 11% 1	760
	21st to end	Night	7% 13% 44% 31% 5%	717
April	1st to 10th	Night	8% 12% 45% 29% 6%	570
	11th to 20th	Night	10% 14% 39% 30% 7% 1	563
	21st to end	Night	8% 12% 35% 34% 10% 1	570
May	1st to 10th	Night	9% 9% 32% 39% 10% 1	570
	11th to 20th	Night	12% 6% 26% 37% 17% 2	561
	21st to end	Night	10% 10% 28% 35% 15% 3	617
June	1st to 10th	Night	6% 6% 21% 41% 24% 2	570
	11th to 20th	Night	3 6% 28% 45% 16% 2	570
	21st to end	Night	3 5% 19% 40% 30% 3	570
July	1st to 10th	Night	8% 2 9% 38% 38% 5%	555
	11th to 20th	Night	6% 1 5% 38% 42% 9%	552
	21st to end	Night	5% 2 3 32% 51% 7%	624
August	1st to 10th	Night	8% 2 7% 35% 40% 9%	567
	11th to 20th	Night	6% 1 10% 42% 34% 6%	564
	21st to end	Night	5% 2 11% 41% 35% 6%	627
September	1st to 10th	Night	5% 3 13% 42% 30% 7%	570
	11th to 20th	Night	6% 4 24% 38% 23% 5%	570
	21st to end	Night	5% 6% 26% 38% 22% 4	570
October	1st to 10th	Night	6% 7% 27% 40% 17% 3	760
	11th to 20th	Night	3 7% 34% 38% 16% 3	760
	21st to end	Night	5% 6% 37% 33% 15% 3	836
November	1st to 10th	Night	3 10% 38% 34% 13% 2	958
	11th to 20th	Night	4 11% 42% 30% 10% 2	1000
	21st to end	Night	6% 10% 38% 34% 10% 1	1000
December	1st to 10th	Night	3 15% 41% 32% 8% 1	978
	11th to 20th	Night	5% 15% 45% 26% 8% 1	950
	21st to end	Night	6% 19% 44% 24% 5% 1	1045

Page generated at 2024-12-03 04:45:10. Version ac07

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