Creek Skies Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Creek Skies Observatory clear sky chart from 2005-11-06 to 2024-11-30.

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	12% 6% 2 6% 5% 4 5% 4 6% 8% 42%	101116
	Night	13% 7% 2 6% 4 4 4 4 5% 7% 44%	98452
Transparency	Day	38% 7% 12% 20% 18% 5%	104922
	Night	37% 6% 11% 20% 20% 6%	102772
Seeing	Day	15% 10% 22% 24% 19% 9%	14760
	Night	15% 8% 22% 30% 21% 4	24772

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	17% 10% 2 7% 5% 4 5% 4 4 5% 36%	2836
	11th to 20th	Day	16% 7% 3 7% 4 3 3 2 4 4 47%	2840
	21st to end	Day	23% 10% 2 6% 4 3 3 2 4 5% 40%	3416
February	1st to 10th	Day	18% 9% 3 6% 4 4 4 3 5% 6% 37%	1900
	11th to 20th	Day	21% 9% 3 6% 4 3 4 3 4 5% 39%	1848
	21st to end	Day	20% 8% 2 8% 4 5% 3 2 6% 4 38%	1570
March	1st to 10th	Day	23% 8% 3 8% 4 4 4 3 5% 7% 31%	3120
	11th to 20th	Day	13% 7% 3 6% 4 3 4 3 4 7% 45%	3442
	21st to end	Day	16% 6% 2 7% 5% 4 5% 3 6% 6% 38%	3830
April	1st to 10th	Day	12% 6% 2 5% 5% 4 4 4 5% 8% 46%	2280
	11th to 20th	Day	13% 6% 2 6% 4 4 4 3 5% 7% 46%	2254
	21st to end	Day	9% 5% 1 5% 4 4 5% 4 6% 7% 49%	2342
May	1st to 10th	Day	9% 6% 3 6% 4 5% 4 4 6% 9% 44%	4082
	11th to 20th	Day	15% 6% 2 7% 5% 4 4 4 5% 8% 39%	4081
	21st to end	Day	8% 5% 2 7% 4 4 5% 4 7% 10% 43%	4476
June	1st to 10th	Day	8% 6% 2 7% 6% 5% 5% 5% 7% 10% 36%	2470
	11th to 20th	Day	4 4 2 6% 4 5% 5% 5% 9% 11% 46%	2470
	21st to end	Day	7% 6% 2 6% 5% 5% 7% 6% 8% 10% 39%	2470
July	1st to 10th	Day	7% 5% 2 7% 7% 7% 8% 7% 10% 12% 29%	4120
	11th to 20th	Day	6% 5% 2 6% 6% 6% 6% 6% 9% 11% 36%	4120
	21st to end	Day	11% 10% 4 11% 7% 7% 7% 6% 8% 9% 21%	4466
August	1st to 10th	Day	4 3 1 5% 4 5% 6% 5% 9% 12% 47%	3928
	11th to 20th	Day	6% 4 2 5% 5% 4 5% 4 8% 12% 44%	3729
	21st to end	Day	7% 4 2 5% 4 4 5% 4 6% 9% 51%	4180
September	1st to 10th	Day	9% 5% 2 7% 5% 5% 6% 4 7% 8% 42%	2176
	11th to 20th	Day	13% 6% 2 6% 4 5% 5% 4 6% 7% 42%	2090
	21st to end	Day	11% 6% 2 5% 4 4 4 3 5% 7% 50%	2090
October	1st to 10th	Day	10% 4 2 5% 4 3 3 3 4 6% 55%	2090
	11th to 20th	Day	9% 6% 1 5% 3 3 3 3 4 7% 56%	2068
	21st to end	Day	12% 5% 2 5% 3 3 4 3 5% 5% 55%	1986
November	1st to 10th	Day	13% 5% 2 5% 4 3 3 2 4 5% 54%	1762
	11th to 20th	Day	13% 6% 2 5% 3 4 3 3 5% 6% 51%	1800
	21st to end	Day	15% 6% 2 5% 3 4 4 4 6% 7% 45%	1797
December	1st to 10th	Day	19% 9% 2 6% 3 4 4 3 5% 6% 39%	1710
	11th to 20th	Day	17% 8% 2 7% 5% 4 4 3 4 4 41%	2153
	21st to end	Day	19% 9% 3 6% 5% 5% 5% 3 4 7% 34%	3124
January	1st to 10th	Night	18% 9% 3 6% 4 3 4 3 5% 6% 39%	4109
	11th to 20th	Night	16% 9% 3 6% 4 3 3 3 4 5% 44%	4120
	21st to end	Night	22% 13% 2 5% 3 3 3 3 3 4 39%	4238
February	1st to 10th	Night	16% 9% 3 6% 4 4 3 2 5% 6% 42%	2280
	11th to 20th	Night	21% 8% 3 7% 4 3 3 3 4 4 42%	2218
	21st to end	Night	20% 8% 3 6% 5% 4 4 3 5% 6% 38%	1884
March	1st to 10th	Night	24% 9% 2 7% 5% 3 4 3 4 5% 33%	3733
	11th to 20th	Night	11% 6% 2 5% 4 3 4 4 5% 8% 48%	3517
	21st to end	Night	17% 8% 2 7% 4 4 4 3 5% 5% 40%	3817
April	1st to 10th	Night	11% 5% 2 4 4 3 4 3 7% 8% 47%	1912
	11th to 20th	Night	13% 6% 2 6% 3 3 3 3 4 6% 50%	1875
	21st to end	Night	9% 5% 2 6% 4 3 4 4 4 6% 53%	1838
May	1st to 10th	Night	11% 6% 2 7% 5% 5% 5% 4 6% 8% 41%	2813
	11th to 20th	Night	15% 6% 3 7% 4 5% 4 4 6% 8% 39%	2812
	21st to end	Night	6% 4 1 5% 4 4 6% 5% 7% 12% 46%	3079
June	1st to 10th	Night	6% 5% 2 6% 6% 5% 7% 5% 8% 10% 39%	1710
	11th to 20th	Night	3 3 2 5% 4 4 5% 4 7% 11% 52%	1710
	21st to end	Night	5% 4 2 5% 4 5% 5% 5% 7% 11% 47%	1710
July	1st to 10th	Night	7% 6% 3 8% 6% 6% 6% 5% 9% 12% 33%	2840
	11th to 20th	Night	6% 4 2 5% 5% 5% 6% 6% 9% 13% 40%	2840
	21st to end	Night	9% 10% 4 10% 7% 6% 7% 6% 8% 9% 24%	3087
August	1st to 10th	Night	3 3 2 5% 4 4 5% 4 8% 12% 50%	2983
	11th to 20th	Night	6% 5% 2 6% 4 4 5% 4 6% 9% 49%	3100
	21st to end	Night	8% 5% 2 5% 3 3 4 3 5% 8% 55%	3476
September	1st to 10th	Night	7% 5% 2 6% 4 6% 6% 5% 6% 9% 44%	1985
	11th to 20th	Night	12% 6% 3 6% 4 4 5% 3 6% 8% 43%	2090
	21st to end	Night	9% 6% 2 5% 3 3 4 3 5% 7% 52%	2090
October	1st to 10th	Night	9% 4 2 5% 3 3 3 2 4 6% 60%	2090
	11th to 20th	Night	11% 5% 2 5% 3 3 3 3 3 6% 56%	2109
	21st to end	Night	12% 6% 2 5% 4 4 3 3 4 4 55%	2608
November	1st to 10th	Night	11% 5% 2 4 3 4 3 3 5% 5% 54%	2536
	11th to 20th	Night	13% 6% 2 4 3 3 3 2 4 7% 54%	2600
	21st to end	Night	14% 7% 2 5% 3 3 4 4 4 6% 48%	2599
December	1st to 10th	Night	18% 8% 3 7% 4 3 4 3 5% 6% 38%	2470
	11th to 20th	Night	16% 7% 2 6% 3 3 3 3 4 5% 47%	3042
	21st to end	Night	18% 9% 3 7% 5% 4 5% 3 6% 8% 32%	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	49% 5% 7% 14% 21% 3	2837
	11th to 20th	Day	41% 4 7% 23% 23% 2	2840
	21st to end	Day	49% 3 8% 18% 19% 5%	3416
February	1st to 10th	Day	47% 5% 8% 18% 19% 3	1900
	11th to 20th	Day	48% 4 5% 19% 19% 5%	1858
	21st to end	Day	49% 5% 7% 13% 20% 6%	1570
March	1st to 10th	Day	52% 6% 9% 11% 14% 9%	3120
	11th to 20th	Day	40% 5% 7% 19% 23% 6%	3442
	21st to end	Day	44% 6% 11% 16% 18% 4	3830
April	1st to 10th	Day	38% 5% 12% 21% 19% 6%	2280
	11th to 20th	Day	38% 6% 8% 17% 24% 7%	2254
	21st to end	Day	31% 7% 12% 25% 21% 3	2342
May	1st to 10th	Day	36% 8% 13% 25% 16% 2	4120
	11th to 20th	Day	41% 8% 14% 25% 12% 1	4085
	21st to end	Day	33% 9% 13% 25% 18% 2	4489
June	1st to 10th	Day	40% 11% 16% 19% 12% 2	2470
	11th to 20th	Day	29% 10% 19% 24% 16% 1	2470
	21st to end	Day	36% 12% 16% 22% 12% 3	2470
July	1st to 10th	Day	40% 15% 21% 17% 6% 1	4055
	11th to 20th	Day	38% 12% 23% 19% 7% 1	4051
	21st to end	Day	56% 12% 14% 13% 5%	4324
August	1st to 10th	Day	24% 10% 16% 36% 13%	3915
	11th to 20th	Day	30% 9% 18% 26% 14% 3	3765
	21st to end	Day	30% 9% 14% 19% 24% 4	4179
September	1st to 10th	Day	37% 10% 16% 15% 16% 6%	2176
	11th to 20th	Day	40% 8% 11% 20% 18% 3	2090
	21st to end	Day	35% 6% 13% 18% 22% 7%	2090
October	1st to 10th	Day	24% 5% 6% 11% 37% 16%	3480
	11th to 20th	Day	21% 3 5% 16% 30% 24%	3412
	21st to end	Day	24% 4 7% 23% 32% 10%	3249
November	1st to 10th	Day	34% 4 7% 17% 29% 9%	1762
	11th to 20th	Day	34% 4 8% 18% 27% 9%	1800
	21st to end	Day	37% 5% 8% 18% 26% 5%	1797
December	1st to 10th	Day	46% 5% 8% 17% 19% 5%	1710
	11th to 20th	Day	46% 3 7% 18% 20% 6%	2150
	21st to end	Day	49% 5% 10% 18% 16% 2	3124
January	1st to 10th	Night	45% 4 7% 18% 23% 3	4109
	11th to 20th	Night	42% 5% 7% 22% 18% 6%	4120
	21st to end	Night	51% 3 5% 15% 22% 4	4238
February	1st to 10th	Night	44% 3 7% 19% 20% 6%	2280
	11th to 20th	Night	47% 3 6% 17% 19% 8%	2219
	21st to end	Night	47% 5% 8% 14% 18% 8%	1884
March	1st to 10th	Night	52% 6% 9% 12% 15% 6%	3733
	11th to 20th	Night	33% 5% 10% 19% 24% 9%	3517
	21st to end	Night	45% 4 7% 20% 20% 4	3817
April	1st to 10th	Night	33% 7% 12% 21% 21% 6%	1912
	11th to 20th	Night	35% 5% 6% 21% 22% 11%	1875
	21st to end	Night	32% 5% 11% 27% 20% 5%	1838
May	1st to 10th	Night	36% 10% 14% 20% 18% 2	2840
	11th to 20th	Night	40% 8% 15% 25% 12% 1	2813
	21st to end	Night	27% 10% 16% 27% 18% 2	3087
June	1st to 10th	Night	35% 11% 15% 21% 15% 2	1710
	11th to 20th	Night	23% 10% 24% 23% 18% 2	1710
	21st to end	Night	29% 10% 19% 21% 16% 5%	1710
July	1st to 10th	Night	40% 12% 21% 19% 7% 1	2795
	11th to 20th	Night	30% 13% 24% 24% 7% 2	2786
	21st to end	Night	51% 14% 14% 14% 6% 1	2988
August	1st to 10th	Night	24% 9% 15% 38% 12% 1	2972
	11th to 20th	Night	30% 8% 17% 28% 16% 2	3130
	21st to end	Night	28% 7% 14% 17% 28% 5%	3476
September	1st to 10th	Night	34% 11% 16% 17% 15% 6%	1985
	11th to 20th	Night	38% 9% 11% 19% 20% 3	2090
	21st to end	Night	31% 5% 12% 21% 22% 8%	2090
October	1st to 10th	Night	23% 4 6% 16% 33% 17%	3480
	11th to 20th	Night	19% 3 4 17% 29% 27%	3492
	21st to end	Night	22% 4 5% 24% 31% 13%	4295
November	1st to 10th	Night	32% 5% 9% 19% 24% 11%	2536
	11th to 20th	Night	32% 4 6% 20% 28% 10%	2600
	21st to end	Night	37% 4 8% 21% 23% 7%	2599
December	1st to 10th	Night	46% 6% 9% 17% 19% 3	2470
	11th to 20th	Night	40% 4 8% 16% 28% 4	3044
	21st to end	Night	48% 5% 11% 19% 16% 2	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	21% 27% 36% 14% 2	270
	11th to 20th	Day	23% 26% 30% 16% 5%	270
	21st to end	Day	23% 24% 40% 10% 3 1	297
February	1st to 10th	Day	29% 18% 32% 18% 4	270
	11th to 20th	Day	36% 22% 29% 11% 2	270
	21st to end	Day	28% 26% 36% 10%	225
March	1st to 10th	Day	25% 21% 33% 16% 4 2	270
	11th to 20th	Day	21% 19% 34% 18% 7% 1	435
	21st to end	Day	20% 17% 36% 21% 6%	506
April	1st to 10th	Day	20% 16% 30% 18% 14% 1	460
	11th to 20th	Day	18% 14% 31% 23% 13% 1	452
	21st to end	Day	16% 11% 31% 26% 15% 2	460
May	1st to 10th	Day	15% 10% 29% 26% 15% 6%	463
	11th to 20th	Day	10% 7% 22% 32% 20% 9%	487
	21st to end	Day	9% 6% 19% 27% 24% 14%	529
June	1st to 10th	Day	12% 4 19% 29% 23% 13%	490
	11th to 20th	Day	5% 5% 15% 25% 28% 23%	490
	21st to end	Day	9% 4 14% 26% 28% 19%	490
July	1st to 10th	Day	7% 2 10% 28% 28% 24%	485
	11th to 20th	Day	7% 4 7% 21% 32% 29%	484
	21st to end	Day	8% 3 10% 19% 36% 23%	532
August	1st to 10th	Day	9% 1 10% 25% 34% 21%	486
	11th to 20th	Day	8% 3 10% 31% 31% 17%	479
	21st to end	Day	13% 3 9% 24% 31% 20%	539
September	1st to 10th	Day	8% 3 10% 30% 32% 15%	490
	11th to 20th	Day	13% 6% 12% 26% 31% 12%	490
	21st to end	Day	14% 5% 15% 26% 32% 9%	490
October	1st to 10th	Day	12% 4 21% 32% 22% 9%	490
	11th to 20th	Day	10% 10% 24% 32% 22% 3	490
	21st to end	Day	16% 12% 19% 30% 20% 3	435
November	1st to 10th	Day	18% 11% 28% 29% 12% 2	300
	11th to 20th	Day	16% 14% 36% 25% 8%	300
	21st to end	Day	17% 12% 36% 24% 10% 1	299
December	1st to 10th	Day	26% 22% 30% 17% 3 1	270
	11th to 20th	Day	23% 20% 27% 24% 5% 1	270
	21st to end	Day	27% 20% 32% 16% 5%	297
January	1st to 10th	Night	22% 16% 32% 24% 5%	760
	11th to 20th	Night	21% 16% 31% 26% 7%	760
	21st to end	Night	20% 17% 35% 25% 3	836
February	1st to 10th	Night	21% 13% 29% 33% 5%	760
	11th to 20th	Night	24% 16% 31% 25% 3	743
	21st to end	Night	23% 16% 35% 23% 3	628
March	1st to 10th	Night	20% 13% 32% 30% 5%	760
	11th to 20th	Night	18% 13% 33% 28% 8% 1	760
	21st to end	Night	19% 13% 28% 31% 9%	836
April	1st to 10th	Night	13% 12% 34% 27% 14% 1	582
	11th to 20th	Night	16% 9% 32% 29% 13% 1	563
	21st to end	Night	11% 9% 25% 39% 16% 1	570
May	1st to 10th	Night	11% 5% 25% 34% 23% 2	570
	11th to 20th	Night	9% 5% 19% 34% 27% 6%	561
	21st to end	Night	8% 3 12% 36% 35% 6%	617
June	1st to 10th	Night	7% 3 13% 38% 35% 5%	570
	11th to 20th	Night	2 1 11% 34% 38% 14%	570
	21st to end	Night	7% 2 8% 31% 43% 9%	570
July	1st to 10th	Night	8% 2 7% 25% 46% 12%	555
	11th to 20th	Night	5% 1 5% 27% 46% 17%	552
	21st to end	Night	6% 2 9% 27% 44% 12%	624
August	1st to 10th	Night	5% 1 7% 28% 48% 11%	567
	11th to 20th	Night	12% 1 7% 30% 42% 8%	564
	21st to end	Night	14% 3 8% 25% 39% 10%	627
September	1st to 10th	Night	8% 3 9% 29% 40% 10%	655
	11th to 20th	Night	14% 3 12% 30% 37% 5%	760
	21st to end	Night	12% 3 16% 33% 35% 2	760
October	1st to 10th	Night	10% 4 20% 34% 26% 6%	760
	11th to 20th	Night	13% 6% 24% 34% 22% 2	760
	21st to end	Night	15% 8% 21% 37% 18% 2	836
November	1st to 10th	Night	13% 8% 21% 37% 20% 2	780
	11th to 20th	Night	15% 8% 31% 33% 12% 1	800
	21st to end	Night	17% 10% 28% 33% 11%	800
December	1st to 10th	Night	21% 14% 29% 27% 9% 1	760
	11th to 20th	Night	22% 11% 29% 28% 9%	760
	21st to end	Night	26% 12% 28% 27% 6%	836

Page generated at 2024-11-27 16:30:50. Version ac07

Copyright © 2024 Attilla Danko.