Cobblestone Creek Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cobblestone Creek 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	15% 10% 4 8% 5% 5% 5% 4 5% 7% 32%	102113
	Night	16% 11% 4 8% 5% 4 4 3 5% 6% 34%	97455
Transparency	Day	48% 6% 11% 21% 12% 1	105785
	Night	48% 6% 11% 21% 13% 2	101922
Seeing	Day	19% 10% 26% 23% 16% 7%	15421
	Night	19% 8% 27% 30% 14% 2	24954

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	20% 19% 7% 14% 5% 5% 4 3 4 4 14%	2836
	11th to 20th	Day	17% 21% 6% 12% 5% 6% 8% 3 3 5% 14%	2840
	21st to end	Day	28% 19% 10% 11% 6% 5% 3 2 3 3 10%	3124
February	1st to 10th	Day	18% 16% 6% 10% 7% 6% 4 2 5% 4 22%	1710
	11th to 20th	Day	15% 12% 7% 14% 7% 5% 4 3 4 6% 23%	1829
	21st to end	Day	18% 14% 4 10% 5% 5% 4 3 5% 6% 27%	1570
March	1st to 10th	Day	22% 15% 6% 10% 6% 4 4 3 4 5% 21%	3238
	11th to 20th	Day	13% 12% 4 8% 6% 4 4 3 5% 7% 35%	3480
	21st to end	Day	21% 11% 5% 9% 5% 4 4 3 5% 6% 28%	3815
April	1st to 10th	Day	15% 13% 3 8% 6% 5% 4 4 5% 7% 30%	2161
	11th to 20th	Day	18% 10% 2 7% 5% 4 4 4 6% 7% 35%	2392
	21st to end	Day	19% 9% 3 7% 5% 4 5% 3 5% 7% 33%	2470
May	1st to 10th	Day	20% 10% 3 7% 5% 5% 6% 4 5% 7% 29%	4082
	11th to 20th	Day	20% 8% 2 7% 5% 4 4 3 5% 7% 34%	4081
	21st to end	Day	11% 6% 2 7% 5% 5% 6% 5% 7% 9% 38%	4476
June	1st to 10th	Day	12% 6% 2 7% 6% 5% 5% 4 6% 9% 37%	2470
	11th to 20th	Day	11% 7% 3 6% 5% 5% 5% 5% 7% 9% 38%	2609
	21st to end	Day	11% 4 2 6% 4 5% 5% 5% 7% 11% 39%	2660
July	1st to 10th	Day	10% 6% 3 7% 5% 5% 5% 4 6% 10% 38%	4440
	11th to 20th	Day	8% 5% 2 5% 4 4 5% 5% 7% 11% 44%	4189
	21st to end	Day	9% 6% 2 7% 5% 5% 6% 5% 8% 10% 39%	4466
August	1st to 10th	Day	9% 6% 2 8% 5% 5% 5% 5% 7% 9% 39%	4104
	11th to 20th	Day	8% 5% 2 7% 4 5% 6% 4 9% 10% 40%	4044
	21st to end	Day	7% 5% 2 6% 5% 5% 5% 4 6% 11% 44%	4443
September	1st to 10th	Day	12% 6% 2 6% 4 4 4 2 5% 7% 48%	2114
	11th to 20th	Day	10% 5% 2 6% 4 5% 5% 4 5% 9% 45%	2090
	21st to end	Day	18% 7% 2 5% 4 4 4 3 4 6% 42%	2090
October	1st to 10th	Day	14% 7% 2 6% 4 4 3 4 5% 7% 43%	2043
	11th to 20th	Day	15% 8% 2 7% 4 4 4 4 5% 7% 40%	1900
	21st to end	Day	20% 10% 3 7% 5% 5% 4 3 5% 7% 30%	2001
November	1st to 10th	Day	12% 8% 3 6% 5% 4 4 3 4 7% 44%	1762
	11th to 20th	Day	17% 14% 4 6% 4 5% 4 3 4 6% 32%	1800
	21st to end	Day	19% 15% 6% 8% 5% 3 3 3 4 6% 28%	1797
December	1st to 10th	Day	18% 19% 7% 11% 7% 4 3 3 4 5% 19%	1710
	11th to 20th	Day	16% 15% 7% 9% 6% 5% 5% 4 6% 6% 21%	2153
	21st to end	Day	25% 23% 7% 10% 6% 4 4 3 4 4 9%	3124
January	1st to 10th	Night	17% 19% 8% 14% 5% 5% 5% 3 4 4 17%	4109
	11th to 20th	Night	16% 20% 7% 15% 6% 5% 6% 4 4 4 14%	4120
	21st to end	Night	29% 20% 7% 10% 6% 3 3 3 3 4 13%	4532
February	1st to 10th	Night	21% 15% 4 9% 5% 5% 4 3 4 5% 25%	2470
	11th to 20th	Night	16% 13% 5% 9% 6% 5% 5% 4 5% 5% 27%	2234
	21st to end	Night	20% 15% 5% 10% 4 4 3 3 4 4 27%	1884
March	1st to 10th	Night	21% 14% 4 7% 4 3 4 3 4 5% 31%	3614
	11th to 20th	Night	13% 9% 2 6% 4 4 4 3 5% 7% 42%	3480
	21st to end	Night	19% 9% 3 7% 5% 4 3 3 4 5% 38%	3817
April	1st to 10th	Night	16% 10% 3 6% 5% 4 4 3 6% 7% 35%	2033
	11th to 20th	Night	17% 8% 3 6% 4 4 4 4 6% 7% 36%	1735
	21st to end	Night	16% 7% 2 8% 4 4 5% 3 6% 7% 36%	1710
May	1st to 10th	Night	22% 10% 3 8% 5% 5% 5% 4 5% 6% 28%	2813
	11th to 20th	Night	18% 8% 3 6% 3 3 4 3 6% 7% 39%	2812
	21st to end	Night	9% 5% 1 6% 4 4 5% 4 7% 10% 45%	3079
June	1st to 10th	Night	9% 7% 2 7% 4 4 4 4 6% 8% 44%	1710
	11th to 20th	Night	9% 5% 2 4 4 4 5% 4 8% 10% 45%	1564
	21st to end	Night	9% 4 2 5% 5% 4 5% 5% 7% 10% 45%	1520
July	1st to 10th	Night	11% 5% 2 5% 3 4 5% 4 7% 8% 45%	2530
	11th to 20th	Night	7% 4 2 5% 4 3 5% 5% 7% 9% 51%	2768
	21st to end	Night	7% 6% 2 7% 5% 5% 6% 4 6% 8% 43%	3087
August	1st to 10th	Night	10% 7% 3 7% 5% 4 5% 5% 8% 9% 37%	2825
	11th to 20th	Night	7% 8% 3 8% 5% 5% 4 4 6% 7% 43%	2785
	21st to end	Night	4 4 2 6% 5% 5% 5% 5% 7% 8% 49%	3210
September	1st to 10th	Night	11% 6% 2 5% 4 3 4 4 4 6% 51%	2046
	11th to 20th	Night	9% 5% 2 4 3 2 3 3 5% 6% 56%	2090
	21st to end	Night	14% 6% 3 6% 4 4 4 3 4 6% 45%	2090
October	1st to 10th	Night	10% 5% 1 6% 4 4 4 3 6% 7% 49%	2136
	11th to 20th	Night	17% 7% 3 6% 4 5% 3 3 5% 6% 42%	2280
	21st to end	Night	20% 8% 3 6% 4 4 4 3 5% 7% 36%	2593
November	1st to 10th	Night	13% 7% 3 6% 4 4 4 3 5% 6% 45%	2536
	11th to 20th	Night	16% 13% 3 7% 3 4 4 3 6% 6% 35%	2600
	21st to end	Night	19% 14% 4 8% 5% 4 4 3 5% 6% 28%	2599
December	1st to 10th	Night	20% 16% 5% 10% 5% 4 4 4 4 6% 23%	2470
	11th to 20th	Night	19% 15% 5% 11% 5% 4 3 4 5% 5% 24%	3042
	21st to end	Night	25% 21% 7% 10% 4 4 3 3 4 5% 14%	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	72% 5% 7% 11% 4	2837
	11th to 20th	Day	75% 4 9% 8% 4	2840
	21st to end	Day	82% 3 5% 7% 3	3124
February	1st to 10th	Day	66% 5% 9% 12% 7%	1710
	11th to 20th	Day	65% 4 7% 15% 8% 1	1839
	21st to end	Day	58% 5% 13% 15% 7% 2	1570
March	1st to 10th	Day	65% 6% 9% 16% 4	3238
	11th to 20th	Day	49% 5% 10% 26% 9% 1	3480
	21st to end	Day	57% 5% 12% 20% 6%	3815
April	1st to 10th	Day	52% 6% 12% 17% 11% 1	2161
	11th to 20th	Day	49% 6% 12% 19% 13% 2	2392
	21st to end	Day	50% 6% 10% 20% 11% 2	2470
May	1st to 10th	Day	53% 7% 12% 21% 6% 1	4120
	11th to 20th	Day	48% 7% 14% 23% 8% 1	4085
	21st to end	Day	38% 9% 14% 21% 14% 3	4489
June	1st to 10th	Day	42% 7% 10% 25% 14% 1	2470
	11th to 20th	Day	40% 8% 15% 22% 15% 1	2609
	21st to end	Day	37% 10% 15% 21% 15% 3	2660
July	1st to 10th	Day	42% 6% 11% 22% 16% 2	4371
	11th to 20th	Day	33% 7% 13% 26% 20% 1	4117
	21st to end	Day	38% 8% 13% 19% 18% 4	4324
August	1st to 10th	Day	38% 8% 15% 24% 14% 1	4091
	11th to 20th	Day	36% 7% 12% 29% 16% 1	4083
	21st to end	Day	34% 7% 13% 30% 13% 3	4442
September	1st to 10th	Day	36% 6% 11% 23% 19% 4	2114
	11th to 20th	Day	36% 6% 11% 25% 19% 3	2090
	21st to end	Day	43% 5% 11% 21% 20% 1	2090
October	1st to 10th	Day	28% 5% 11% 34% 22% 1	3394
	11th to 20th	Day	36% 4 11% 25% 22% 2	3140
	21st to end	Day	42% 4 10% 23% 18% 1	3277
November	1st to 10th	Day	40% 5% 10% 25% 17% 2	1762
	11th to 20th	Day	53% 4 11% 19% 11% 2	1800
	21st to end	Day	59% 4 10% 17% 9% 1	1797
December	1st to 10th	Day	68% 5% 10% 14% 4	1710
	11th to 20th	Day	61% 6% 11% 16% 6%	2150
	21st to end	Day	79% 4 8% 6% 3	3124
January	1st to 10th	Night	70% 5% 8% 12% 5%	4109
	11th to 20th	Night	75% 5% 8% 10% 2	4120
	21st to end	Night	76% 3 8% 9% 3 1	4532
February	1st to 10th	Night	62% 5% 11% 14% 7% 1	2470
	11th to 20th	Night	58% 5% 10% 16% 10% 1	2235
	21st to end	Night	62% 4 9% 14% 9% 2	1884
March	1st to 10th	Night	54% 6% 11% 19% 9% 1	3614
	11th to 20th	Night	40% 6% 13% 28% 12% 2	3480
	21st to end	Night	49% 5% 10% 26% 10% 1	3817
April	1st to 10th	Night	47% 5% 13% 19% 14% 2	2033
	11th to 20th	Night	46% 5% 12% 18% 17% 3	1735
	21st to end	Night	46% 6% 12% 19% 15% 2	1710
May	1st to 10th	Night	55% 7% 10% 18% 9% 1	2840
	11th to 20th	Night	42% 8% 12% 25% 12% 1	2813
	21st to end	Night	31% 9% 14% 27% 16% 2	3087
June	1st to 10th	Night	37% 7% 12% 22% 20% 2	1710
	11th to 20th	Night	32% 9% 13% 27% 16% 3	1564
	21st to end	Night	33% 8% 15% 24% 16% 4	1520
July	1st to 10th	Night	36% 6% 11% 25% 17% 6%	2490
	11th to 20th	Night	28% 7% 13% 32% 19% 1	2717
	21st to end	Night	36% 7% 14% 20% 18% 4	2988
August	1st to 10th	Night	40% 8% 15% 22% 14% 1	2814
	11th to 20th	Night	39% 6% 10% 26% 18%	2812
	21st to end	Night	30% 7% 14% 29% 17% 3	3210
September	1st to 10th	Night	34% 6% 11% 25% 18% 6%	2046
	11th to 20th	Night	28% 5% 10% 28% 25% 4	2090
	21st to end	Night	39% 6% 10% 20% 22% 2	2090
October	1st to 10th	Night	25% 4 8% 30% 32% 1	3565
	11th to 20th	Night	33% 4 10% 28% 22% 3	3779
	21st to end	Night	36% 3 9% 27% 20% 4	4267
November	1st to 10th	Night	40% 4 12% 23% 18% 2	2536
	11th to 20th	Night	50% 4 9% 22% 13% 3	2600
	21st to end	Night	57% 4 12% 19% 7% 1	2599
December	1st to 10th	Night	64% 5% 9% 16% 6%	2470
	11th to 20th	Night	60% 5% 12% 18% 5%	3044
	21st to end	Night	74% 5% 9% 9% 3	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	30% 13% 33% 16% 7% 1	270
	11th to 20th	Day	26% 18% 38% 14% 4	270
	21st to end	Day	31% 15% 31% 16% 6%	297
February	1st to 10th	Day	32% 16% 32% 17% 3 1	270
	11th to 20th	Day	26% 19% 33% 17% 5%	270
	21st to end	Day	25% 18% 41% 13% 2	225
March	1st to 10th	Day	25% 17% 34% 19% 6%	336
	11th to 20th	Day	25% 15% 33% 20% 5% 2	460
	21st to end	Day	30% 14% 28% 22% 5%	506
April	1st to 10th	Day	22% 14% 30% 22% 8% 2	460
	11th to 20th	Day	21% 16% 28% 20% 9% 6%	452
	21st to end	Day	24% 12% 31% 23% 8% 2	460
May	1st to 10th	Day	25% 10% 29% 24% 9% 3	463
	11th to 20th	Day	23% 7% 25% 23% 15% 7%	487
	21st to end	Day	12% 7% 24% 24% 22% 12%	529
June	1st to 10th	Day	12% 7% 22% 29% 23% 8%	490
	11th to 20th	Day	13% 7% 23% 28% 23% 7%	629
	21st to end	Day	13% 6% 28% 27% 19% 8%	680
July	1st to 10th	Day	13% 2 17% 27% 23% 18%	671
	11th to 20th	Day	11% 4 19% 24% 25% 16%	524
	21st to end	Day	11% 3 18% 23% 29% 17%	532
August	1st to 10th	Day	11% 3 14% 26% 30% 17%	486
	11th to 20th	Day	13% 2 18% 29% 25% 13%	479
	21st to end	Day	8% 4 15% 24% 30% 17%	539
September	1st to 10th	Day	13% 3 17% 26% 28% 13%	490
	11th to 20th	Day	9% 4 14% 23% 31% 21%	490
	21st to end	Day	20% 8% 19% 24% 18% 10%	490
October	1st to 10th	Day	12% 7% 23% 28% 19% 12%	490
	11th to 20th	Day	15% 12% 35% 19% 14% 4	490
	21st to end	Day	24% 15% 33% 20% 6% 1	450
November	1st to 10th	Day	14% 12% 36% 24% 10% 4	300
	11th to 20th	Day	24% 17% 28% 20% 10% 2	300
	21st to end	Day	28% 13% 39% 18% 2	299
December	1st to 10th	Day	25% 17% 34% 16% 7% 1	270
	11th to 20th	Day	23% 15% 41% 18% 4	270
	21st to end	Day	34% 16% 27% 20% 3	297
January	1st to 10th	Night	24% 14% 35% 23% 4	760
	11th to 20th	Night	31% 13% 33% 18% 4 1	760
	21st to end	Night	25% 13% 34% 25% 3	836
February	1st to 10th	Night	27% 10% 34% 26% 3	760
	11th to 20th	Night	25% 11% 34% 26% 3	743
	21st to end	Night	28% 11% 38% 19% 3	628
March	1st to 10th	Night	24% 9% 33% 27% 7% 1	760
	11th to 20th	Night	21% 13% 34% 27% 6% 1	760
	21st to end	Night	24% 10% 31% 28% 6%	836
April	1st to 10th	Night	21% 11% 35% 28% 5% 1	703
	11th to 20th	Night	20% 9% 35% 25% 9% 1	563
	21st to end	Night	19% 9% 37% 26% 8% 1	570
May	1st to 10th	Night	22% 7% 28% 31% 11% 1	570
	11th to 20th	Night	23% 4 25% 33% 14% 1	561
	21st to end	Night	10% 4 22% 39% 23% 2	617
June	1st to 10th	Night	9% 4 23% 41% 20% 1	570
	11th to 20th	Night	11% 2 18% 45% 22% 1	570
	21st to end	Night	11% 2 20% 41% 23% 2	570
July	1st to 10th	Night	12% 1 16% 35% 33% 4	555
	11th to 20th	Night	6% 4 14% 41% 30% 4	552
	21st to end	Night	9% 2 14% 39% 34% 2	624
August	1st to 10th	Night	9% 1 11% 44% 31% 4	567
	11th to 20th	Night	10% 2 12% 41% 31% 5%	564
	21st to end	Night	7% 2 13% 37% 37% 5%	627
September	1st to 10th	Night	13% 2 16% 35% 29% 6%	716
	11th to 20th	Night	12% 3 13% 34% 33% 6%	760
	21st to end	Night	17% 6% 19% 32% 24% 3	760
October	1st to 10th	Night	12% 5% 23% 33% 22% 4	760
	11th to 20th	Night	20% 9% 28% 29% 13% 1	760
	21st to end	Night	24% 10% 30% 26% 10%	836
November	1st to 10th	Night	18% 8% 29% 30% 13% 1	780
	11th to 20th	Night	22% 15% 28% 27% 8% 1	800
	21st to end	Night	26% 10% 30% 27% 7% 1	800
December	1st to 10th	Night	26% 12% 33% 24% 5%	760
	11th to 20th	Night	25% 10% 35% 25% 5%	760
	21st to end	Night	31% 12% 30% 23% 4	836

Page generated at 2024-11-27 17:30:52. Version ac07

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