Owl Creek Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Owl Creek Observatory clear sky chart from 2005-11-06 to 2024-11-28.

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	10% 5% 2 5% 3 3 4 3 5% 7% 53%	101391
	Night	10% 5% 2 4 3 3 3 3 5% 6% 57%	98227
Transparency	Day	31% 5% 10% 25% 23% 7%	105134
	Night	27% 4 9% 25% 26% 9%	102611
Seeing	Day	12% 8% 25% 30% 20% 5%	15401
	Night	11% 8% 31% 34% 14% 1	25292

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	11% 8% 2 6% 3 3 3 3 5% 6% 50%	2847
	11th to 20th	Day	8% 6% 1 3 2 2 3 2 3 5% 63%	2850
	21st to end	Day	17% 9% 3 6% 2 3 3 2 3 4 48%	3135
February	1st to 10th	Day	12% 8% 3 7% 4 3 3 3 4 6% 47%	1793
	11th to 20th	Day	13% 6% 2 6% 3 4 3 3 5% 6% 51%	1849
	21st to end	Day	16% 8% 2 5% 3 3 3 3 4 4 49%	1570
March	1st to 10th	Day	13% 6% 2 4 3 3 2 2 4 6% 55%	3400
	11th to 20th	Day	11% 5% 2 6% 4 4 4 3 4 6% 50%	3480
	21st to end	Day	14% 9% 4 7% 4 4 4 3 4 6% 40%	3814
April	1st to 10th	Day	10% 6% 1 4 4 4 4 3 4 7% 52%	2090
	11th to 20th	Day	14% 5% 2 6% 3 3 4 3 4 5% 50%	2215
	21st to end	Day	14% 6% 2 6% 3 4 4 3 5% 6% 47%	2470
May	1st to 10th	Day	19% 7% 2 6% 4 4 3 3 4 5% 43%	4082
	11th to 20th	Day	12% 6% 2 6% 4 4 4 3 5% 6% 47%	4082
	21st to end	Day	16% 6% 2 6% 4 4 4 4 6% 7% 42%	4477
June	1st to 10th	Day	8% 4 2 5% 4 4 4 4 7% 9% 48%	2470
	11th to 20th	Day	6% 4 1 5% 3 4 4 5% 7% 9% 53%	2470
	21st to end	Day	5% 3 1 3 4 4 4 4 6% 8% 59%	2470
July	1st to 10th	Day	7% 4 1 5% 5% 4 5% 4 7% 9% 48%	4120
	11th to 20th	Day	5% 3 1 5% 3 3 4 4 5% 8% 58%	4120
	21st to end	Day	4 3 2 4 4 4 4 4 6% 9% 57%	4465
August	1st to 10th	Day	4 3 1 4 4 3 4 4 6% 8% 59%	4104
	11th to 20th	Day	5% 3 2 4 3 4 4 4 6% 9% 56%	4041
	21st to end	Day	3 2 1 4 3 4 4 4 5% 8% 61%	4178
September	1st to 10th	Day	9% 4 1 5% 3 3 3 4 5% 7% 57%	2090
	11th to 20th	Day	12% 5% 2 6% 4 3 4 3 6% 7% 49%	2090
	21st to end	Day	9% 3 1 4 4 2 4 3 4 6% 61%	2090
October	1st to 10th	Day	8% 4 2 4 3 3 3 3 4 5% 61%	2047
	11th to 20th	Day	10% 3 1 4 3 2 2 2 3 3 67%	1900
	21st to end	Day	13% 6% 2 4 2 2 3 2 3 4 59%	2090
November	1st to 10th	Day	10% 4 2 5% 3 3 3 2 4 6% 58%	1913
	11th to 20th	Day	8% 4 1 3 3 2 2 2 4 6% 65%	1800
	21st to end	Day	14% 5% 1 4 3 2 3 2 3 5% 59%	1773
December	1st to 10th	Day	11% 6% 2 5% 3 4 4 4 5% 7% 52%	1710
	11th to 20th	Day	14% 7% 2 5% 3 4 3 3 4 5% 50%	2161
	21st to end	Day	17% 7% 2 6% 4 3 3 3 5% 5% 45%	3135
January	1st to 10th	Night	13% 7% 2 4 3 3 3 3 4 5% 52%	4108
	11th to 20th	Night	6% 4 2 4 3 2 4 3 5% 6% 62%	4120
	21st to end	Night	18% 8% 2 4 2 2 3 2 3 4 51%	4532
February	1st to 10th	Night	12% 8% 3 4 4 3 3 3 4 5% 51%	2403
	11th to 20th	Night	13% 8% 2 4 3 2 3 3 3 7% 53%	2218
	21st to end	Night	11% 7% 3 5% 3 4 3 3 4 5% 52%	1884
March	1st to 10th	Night	12% 7% 3 5% 3 3 3 3 4 6% 51%	3454
	11th to 20th	Night	10% 5% 2 4 2 2 2 2 4 6% 60%	3480
	21st to end	Night	12% 6% 2 5% 4 4 3 3 6% 7% 49%	3817
April	1st to 10th	Night	10% 5% 2 4 4 3 3 3 5% 6% 56%	2090
	11th to 20th	Night	13% 4 2 4 3 2 2 3 5% 6% 56%	1910
	21st to end	Night	13% 4 1 4 3 3 4 4 5% 6% 52%	1710
May	1st to 10th	Night	18% 7% 2 4 4 3 3 2 5% 6% 46%	2823
	11th to 20th	Night	13% 4 2 5% 3 4 4 4 5% 7% 49%	2823
	21st to end	Night	11% 5% 2 4 3 3 4 3 6% 7% 53%	3090
June	1st to 10th	Night	5% 3 1 4 3 3 4 4 5% 11% 58%	1710
	11th to 20th	Night	5% 3 2 4 3 2 4 3 5% 9% 59%	1710
	21st to end	Night	3 2 1 2 2 2 4 3 6% 8% 67%	1710
July	1st to 10th	Night	6% 4 2 6% 4 3 4 4 6% 9% 54%	2850
	11th to 20th	Night	2 1 2 2 3 3 3 5% 9% 69%	2850
	21st to end	Night	4 2 2 3 2 2 3 3 5% 8% 65%	3098
August	1st to 10th	Night	1 1 1 3 3 3 4 3 6% 8% 67%	2836
	11th to 20th	Night	4 2 1 3 3 3 4 4 7% 9% 59%	2798
	21st to end	Night	2 2 1 3 2 3 3 3 6% 9% 67%	3451
September	1st to 10th	Night	8% 4 2 4 2 2 4 3 5% 6% 60%	2090
	11th to 20th	Night	11% 5% 2 5% 3 3 4 3 5% 7% 52%	2090
	21st to end	Night	7% 3 1 3 3 3 3 3 5% 7% 62%	2090
October	1st to 10th	Night	8% 3 2 3 3 3 4 2 4 5% 64%	2114
	11th to 20th	Night	10% 4 1 4 3 3 2 2 3 4 65%	2280
	21st to end	Night	13% 4 2 3 2 2 3 2 4 5% 61%	2508
November	1st to 10th	Night	9% 4 1 3 2 3 3 3 3 5% 64%	2380
	11th to 20th	Night	7% 4 2 4 3 3 4 2 4 5% 63%	2600
	21st to end	Night	12% 5% 1 3 3 3 3 2 3 5% 58%	2562
December	1st to 10th	Night	10% 5% 2 5% 2 3 3 2 4 6% 58%	2470
	11th to 20th	Night	12% 5% 2 5% 4 3 3 3 4 5% 54%	3036
	21st to end	Night	16% 6% 2 4 3 3 4 2 4 5% 52%	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	36% 3 9% 24% 24% 4	2848
	11th to 20th	Day	26% 2 12% 24% 31% 4	2850
	21st to end	Day	42% 2 6% 22% 23% 5%	3135
February	1st to 10th	Day	39% 4 9% 22% 22% 5%	1793
	11th to 20th	Day	36% 3 7% 27% 21% 7%	1859
	21st to end	Day	40% 3 5% 16% 27% 10%	1570
March	1st to 10th	Day	33% 3 7% 17% 24% 16%	3400
	11th to 20th	Day	35% 5% 10% 25% 20% 5%	3480
	21st to end	Day	45% 5% 8% 23% 16% 4	3814
April	1st to 10th	Day	33% 4 10% 22% 21% 9%	2090
	11th to 20th	Day	36% 5% 9% 22% 20% 8%	2215
	21st to end	Day	38% 6% 9% 24% 19% 4	2470
May	1st to 10th	Day	43% 6% 9% 19% 17% 6%	4120
	11th to 20th	Day	36% 8% 13% 25% 17% 2	4086
	21st to end	Day	40% 8% 11% 20% 14% 7%	4489
June	1st to 10th	Day	31% 8% 16% 27% 15% 3	2470
	11th to 20th	Day	26% 8% 13% 28% 21% 4	2470
	21st to end	Day	23% 7% 14% 28% 22% 6%	2470
July	1st to 10th	Day	29% 7% 15% 30% 15% 3	4056
	11th to 20th	Day	23% 5% 9% 35% 25% 3	4051
	21st to end	Day	22% 7% 15% 32% 23% 1	4325
August	1st to 10th	Day	22% 6% 11% 25% 27% 9%	4090
	11th to 20th	Day	24% 7% 14% 34% 18% 4	4080
	21st to end	Day	19% 7% 12% 43% 15% 3	4177
September	1st to 10th	Day	27% 5% 10% 23% 23% 11%	2090
	11th to 20th	Day	34% 6% 10% 20% 23% 7%	2090
	21st to end	Day	26% 4 8% 24% 30% 9%	2090
October	1st to 10th	Day	17% 3 6% 14% 42% 19%	3398
	11th to 20th	Day	18% 2 6% 23% 34% 17%	3140
	21st to end	Day	24% 3 7% 28% 30% 8%	3428
November	1st to 10th	Day	28% 4 8% 22% 29% 10%	1913
	11th to 20th	Day	22% 2 8% 26% 30% 11%	1800
	21st to end	Day	31% 2 5% 24% 28% 9%	1773
December	1st to 10th	Day	33% 4 11% 24% 24% 4	1710
	11th to 20th	Day	37% 3 6% 18% 27% 8%	2159
	21st to end	Day	41% 3 8% 21% 24% 3	3135
January	1st to 10th	Night	35% 3 7% 21% 28% 6%	4108
	11th to 20th	Night	23% 4 17% 21% 28% 7%	4120
	21st to end	Night	39% 3 6% 19% 27% 7%	4532
February	1st to 10th	Night	37% 4 8% 20% 24% 7%	2403
	11th to 20th	Night	34% 4 7% 23% 24% 8%	2218
	21st to end	Night	35% 4 6% 17% 24% 15%	1884
March	1st to 10th	Night	34% 3 7% 17% 22% 16%	3454
	11th to 20th	Night	27% 4 9% 32% 21% 8%	3480
	21st to end	Night	34% 5% 11% 24% 23% 3	3817
April	1st to 10th	Night	30% 4 10% 22% 21% 14%	2090
	11th to 20th	Night	29% 5% 11% 24% 19% 12%	1910
	21st to end	Night	32% 6% 10% 26% 22% 5%	1710
May	1st to 10th	Night	39% 7% 10% 18% 19% 7%	2850
	11th to 20th	Night	33% 8% 13% 26% 17% 2	2824
	21st to end	Night	29% 7% 14% 24% 19% 7%	3099
June	1st to 10th	Night	20% 8% 16% 33% 20% 4	1710
	11th to 20th	Night	22% 6% 14% 28% 25% 5%	1710
	21st to end	Night	16% 5% 13% 30% 30% 8%	1710
July	1st to 10th	Night	27% 6% 13% 33% 18% 3	2805
	11th to 20th	Night	12% 4 9% 44% 27% 4	2796
	21st to end	Night	17% 5% 14% 35% 27% 2	2999
August	1st to 10th	Night	14% 5% 11% 25% 36% 9%	2826
	11th to 20th	Night	19% 6% 11% 36% 24% 4	2825
	21st to end	Night	15% 4 14% 43% 20% 4	3451
September	1st to 10th	Night	26% 5% 9% 22% 26% 12%	2090
	11th to 20th	Night	32% 5% 8% 21% 25% 10%	2090
	21st to end	Night	22% 3 7% 26% 31% 11%	2090
October	1st to 10th	Night	15% 3 7% 14% 38% 24%	3530
	11th to 20th	Night	18% 2 5% 17% 38% 20%	3779
	21st to end	Night	22% 3 5% 30% 30% 10%	4120
November	1st to 10th	Night	25% 3 7% 23% 29% 13%	2380
	11th to 20th	Night	26% 3 7% 23% 29% 12%	2600
	21st to end	Night	30% 3 7% 20% 29% 11%	2562
December	1st to 10th	Night	28% 4 9% 26% 24% 9%	2470
	11th to 20th	Night	34% 3 6% 19% 30% 8%	3037
	21st to end	Night	35% 4 8% 22% 23% 9%	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	18% 13% 35% 25% 8%	270
	11th to 20th	Day	17% 22% 34% 21% 5% 1	270
	21st to end	Day	15% 13% 36% 26% 8% 1	297
February	1st to 10th	Day	21% 15% 39% 20% 5%	270
	11th to 20th	Day	17% 22% 38% 20% 2	270
	21st to end	Day	27% 18% 38% 14% 3	225
March	1st to 10th	Day	18% 19% 38% 20% 6%	270
	11th to 20th	Day	19% 20% 40% 13% 7% 1	270
	21st to end	Day	19% 19% 38% 19% 5%	297
April	1st to 10th	Day	15% 24% 30% 25% 7%	270
	11th to 20th	Day	17% 19% 42% 19% 4	413
	21st to end	Day	18% 14% 37% 22% 7% 2	650
May	1st to 10th	Day	12% 13% 38% 30% 6% 1	653
	11th to 20th	Day	15% 9% 32% 27% 14% 3	675
	21st to end	Day	13% 8% 32% 28% 15% 4	734
June	1st to 10th	Day	8% 4 18% 38% 26% 7%	680
	11th to 20th	Day	6% 2 24% 41% 22% 4	680
	21st to end	Day	4 2 18% 41% 28% 7%	680
July	1st to 10th	Day	6% 1 12% 34% 34% 13%	671
	11th to 20th	Day	3 1 10% 39% 38% 10%	668
	21st to end	Day	6% 5% 32% 42% 15%	739
August	1st to 10th	Day	5% 1 8% 37% 41% 8%	676
	11th to 20th	Day	8% 2 10% 36% 36% 8%	665
	21st to end	Day	4 8% 34% 37% 17%	550
September	1st to 10th	Day	9% 2 7% 31% 35% 17%	300
	11th to 20th	Day	7% 3 10% 32% 34% 14%	300
	21st to end	Day	15% 3 13% 33% 26% 10%	300
October	1st to 10th	Day	6% 5% 26% 33% 20% 9%	300
	11th to 20th	Day	10% 10% 30% 36% 13% 2	300
	21st to end	Day	23% 11% 27% 24% 13% 3	330
November	1st to 10th	Day	16% 7% 38% 25% 12% 2	300
	11th to 20th	Day	15% 10% 35% 25% 13% 2	300
	21st to end	Day	20% 12% 37% 22% 9% 1	291
December	1st to 10th	Day	13% 13% 39% 24% 10% 1	270
	11th to 20th	Day	18% 13% 38% 24% 6%	270
	21st to end	Day	19% 16% 39% 21% 6%	297
January	1st to 10th	Night	12% 12% 39% 29% 7% 1	950
	11th to 20th	Night	13% 14% 36% 31% 6%	950
	21st to end	Night	12% 11% 38% 34% 5%	1045
February	1st to 10th	Night	17% 13% 39% 27% 4	883
	11th to 20th	Night	16% 15% 40% 25% 4	744
	21st to end	Night	16% 17% 41% 23% 3	628
March	1st to 10th	Night	14% 15% 35% 31% 4	594
	11th to 20th	Night	16% 15% 38% 28% 4	570
	21st to end	Night	15% 13% 43% 23% 5%	627
April	1st to 10th	Night	13% 16% 43% 23% 4	570
	11th to 20th	Night	14% 12% 45% 23% 6%	563
	21st to end	Night	14% 12% 41% 26% 6% 1	570
May	1st to 10th	Night	10% 9% 45% 29% 7%	570
	11th to 20th	Night	12% 7% 37% 30% 14% 1	561
	21st to end	Night	7% 6% 34% 36% 16% 2	617
June	1st to 10th	Night	4 4 22% 44% 23% 3	570
	11th to 20th	Night	5% 3 26% 52% 14%	570
	21st to end	Night	3 1 22% 48% 22% 4	570
July	1st to 10th	Night	5% 1 13% 45% 33% 3	555
	11th to 20th	Night	2 1 12% 49% 33% 2	552
	21st to end	Night	3 7% 50% 37% 2	624
August	1st to 10th	Night	1 1 9% 53% 33% 3	567
	11th to 20th	Night	5% 11% 47% 34% 3	564
	21st to end	Night	2 8% 46% 38% 5%	627
September	1st to 10th	Night	8% 2 11% 44% 32% 2	570
	11th to 20th	Night	13% 2 16% 37% 30% 3	570
	21st to end	Night	8% 2 19% 44% 21% 4	570
October	1st to 10th	Night	8% 3 29% 36% 22% 2	594
	11th to 20th	Night	11% 8% 34% 35% 12% 1	760
	21st to end	Night	16% 9% 30% 31% 12% 1	836
November	1st to 10th	Night	11% 7% 36% 32% 13% 1	820
	11th to 20th	Night	9% 13% 33% 36% 10% 1	1000
	21st to end	Night	15% 10% 38% 28% 9%	986
December	1st to 10th	Night	13% 10% 37% 32% 8%	950
	11th to 20th	Night	18% 10% 38% 29% 6%	950
	21st to end	Night	16% 11% 38% 29% 6%	1045

Page generated at 2024-11-24 23:22:21. Version ac07

Copyright © 2024 Attilla Danko.