Burris Fork Creek Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Burris Fork Creek Observatory clear sky chart from 2005-11-06 to 2025-10-04.

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% 8% 3 6% 4 4 4 3 5% 7% 43%	126435
	Night	12% 8% 3 6% 4 4 4 3 5% 6% 45%	123221
Transparency	Day	39% 4 11% 26% 17% 3	130038
	Night	39% 4 10% 25% 18% 4	127694
Seeing	Day	17% 8% 26% 27% 17% 5%	16918
	Night	17% 8% 29% 31% 14% 1	26656

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	15% 12% 4 9% 5% 4 4 3 5% 5% 34%	3865
	11th to 20th	Day	8% 12% 4 7% 5% 6% 4 3 4 5% 41%	4080
	21st to end	Day	15% 12% 4 7% 4 3 4 3 4 5% 38%	4488
February	1st to 10th	Day	16% 11% 4 9% 5% 4 4 3 4 5% 34%	1800
	11th to 20th	Day	16% 11% 3 5% 5% 4 4 3 5% 5% 40%	1797
	21st to end	Day	16% 10% 3 6% 4 3 4 3 5% 6% 39%	1650
March	1st to 10th	Day	15% 10% 3 4 3 2 2 2 3 5% 50%	4931
	11th to 20th	Day	9% 7% 2 5% 4 3 3 3 4 6% 53%	4980
	21st to end	Day	14% 11% 3 8% 6% 5% 5% 4 5% 8% 33%	5502
April	1st to 10th	Day	13% 8% 3 7% 5% 4 4 3 5% 6% 43%	2400
	11th to 20th	Day	17% 7% 2 6% 4 4 4 3 4 7% 41%	2374
	21st to end	Day	19% 10% 3 7% 4 3 4 3 5% 6% 35%	2400
May	1st to 10th	Day	15% 8% 3 8% 5% 5% 4 4 6% 9% 34%	5760
	11th to 20th	Day	12% 7% 3 7% 5% 5% 5% 4 6% 8% 39%	6032
	21st to end	Day	17% 7% 2 6% 4 4 4 3 5% 7% 41%	6935
June	1st to 10th	Day	8% 4 2 5% 5% 4 5% 4 7% 9% 46%	2800
	11th to 20th	Day	9% 5% 1 4 5% 4 5% 4 6% 10% 47%	2800
	21st to end	Day	6% 4 2 5% 5% 4 4 4 7% 9% 50%	2800
July	1st to 10th	Day	11% 6% 2 6% 4 4 4 4 5% 9% 45%	6360
	11th to 20th	Day	7% 6% 3 7% 5% 5% 5% 5% 7% 10% 42%	5993
	21st to end	Day	7% 4 2 6% 5% 5% 5% 5% 8% 12% 41%	6422
August	1st to 10th	Day	5% 4 2 5% 4 4 5% 4 7% 11% 51%	4234
	11th to 20th	Day	11% 6% 2 6% 4 4 5% 4 5% 8% 46%	4044
	21st to end	Day	5% 4 2 5% 4 4 4 4 6% 9% 53%	4312
September	1st to 10th	Day	10% 4 2 4 4 4 4 4 5% 7% 51%	2400
	11th to 20th	Day	10% 5% 2 5% 4 3 4 4 5% 7% 51%	2400
	21st to end	Day	8% 4 2 6% 3 3 5% 3 5% 7% 53%	2085
October	1st to 10th	Day	10% 6% 2 5% 4 3 4 3 4 5% 55%	1930
	11th to 20th	Day	14% 6% 2 5% 3 3 3 2 3 5% 53%	1900
	21st to end	Day	18% 9% 2 5% 3 2 3 2 4 5% 47%	2090
November	1st to 10th	Day	13% 6% 2 4 3 3 3 3 5% 6% 53%	1901
	11th to 20th	Day	14% 7% 2 6% 3 3 3 3 5% 6% 49%	1770
	21st to end	Day	17% 9% 3 5% 3 3 3 3 5% 6% 44%	1600
December	1st to 10th	Day	9% 8% 2 7% 4 3 3 3 4 6% 51%	2610
	11th to 20th	Day	11% 9% 4 7% 4 3 3 3 4 6% 46%	3008
	21st to end	Day	19% 20% 5% 11% 4 4 3 2 3 4 23%	3982
January	1st to 10th	Night	13% 11% 5% 14% 6% 5% 3 3 3 4 32%	6095
	11th to 20th	Night	12% 9% 4 12% 5% 6% 4 4 3 4 37%	5900
	21st to end	Night	16% 12% 5% 7% 5% 3 3 3 4 4 39%	6490
February	1st to 10th	Night	14% 11% 4 8% 6% 4 4 4 6% 6% 35%	2600
	11th to 20th	Night	15% 8% 3 8% 5% 5% 3 3 5% 5% 41%	2488
	21st to end	Night	13% 10% 3 7% 4 3 3 4 4 6% 42%	1980
March	1st to 10th	Night	16% 11% 3 6% 3 3 3 3 4 4 45%	4963
	11th to 20th	Night	11% 7% 2 4 3 2 4 3 5% 7% 52%	4980
	21st to end	Night	14% 10% 3 7% 5% 4 5% 4 6% 7% 35%	5425
April	1st to 10th	Night	11% 7% 2 6% 3 3 5% 3 4 7% 49%	2000
	11th to 20th	Night	14% 8% 2 5% 3 4 3 3 6% 7% 45%	1975
	21st to end	Night	17% 8% 3 5% 5% 4 3 4 4 6% 40%	2000
May	1st to 10th	Night	16% 9% 3 7% 4 4 3 3 6% 8% 37%	4148
	11th to 20th	Night	11% 7% 2 6% 4 3 4 4 5% 8% 44%	3880
	21st to end	Night	15% 7% 2 5% 4 4 3 3 5% 7% 44%	3942
June	1st to 10th	Night	7% 3 1 5% 4 4 5% 5% 6% 10% 51%	1600
	11th to 20th	Night	6% 5% 1 5% 4 3 4 4 7% 10% 50%	1600
	21st to end	Night	3 3 1 3 3 4 4 4 7% 10% 59%	1600
July	1st to 10th	Night	8% 5% 2 6% 4 4 4 4 5% 9% 47%	3618
	11th to 20th	Night	5% 5% 2 6% 4 4 5% 4 6% 10% 49%	3978
	21st to end	Night	5% 4 2 5% 4 4 6% 4 7% 11% 48%	4449
August	1st to 10th	Night	4 3 1 3 3 3 3 3 6% 8% 63%	2926
	11th to 20th	Night	10% 6% 3 6% 3 3 3 3 5% 7% 51%	3009
	21st to end	Night	4 3 1 4 4 3 4 4 6% 8% 60%	3586
September	1st to 10th	Night	11% 5% 2 4 2 2 3 3 4 7% 57%	2000
	11th to 20th	Night	9% 5% 2 4 3 4 4 3 7% 7% 52%	2000
	21st to end	Night	8% 5% 2 5% 3 3 4 3 4 6% 56%	2289
October	1st to 10th	Night	8% 4 2 4 3 3 3 3 4 6% 60%	2317
	11th to 20th	Night	12% 5% 2 5% 3 3 4 3 4 5% 53%	2280
	21st to end	Night	16% 7% 2 4 3 3 4 2 4 5% 49%	2508
November	1st to 10th	Night	11% 6% 2 4 3 2 4 2 4 5% 57%	2395
	11th to 20th	Night	12% 7% 3 6% 4 3 3 2 4 5% 50%	2625
	21st to end	Night	15% 8% 2 6% 3 3 3 2 4 5% 47%	2800
December	1st to 10th	Night	9% 9% 3 5% 4 3 4 3 5% 5% 50%	4580
	11th to 20th	Night	14% 10% 3 7% 4 3 3 3 4 5% 43%	5199
	21st to end	Night	22% 18% 5% 9% 4 4 3 3 3 4 25%	6996

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	52% 3 10% 22% 12% 2	3866
	11th to 20th	Day	45% 5% 7% 22% 16% 4	4080
	21st to end	Day	49% 3 8% 16% 19% 5%	4488
February	1st to 10th	Day	53% 3 10% 20% 12% 1	1800
	11th to 20th	Day	48% 3 11% 20% 14% 3	1806
	21st to end	Day	46% 3 8% 23% 16% 4	1650
March	1st to 10th	Day	40% 2 6% 23% 24% 5%	4931
	11th to 20th	Day	32% 4 8% 24% 25% 7%	4980
	21st to end	Day	49% 5% 15% 25% 6%	5504
April	1st to 10th	Day	43% 4 10% 25% 17% 2	2400
	11th to 20th	Day	44% 4 11% 24% 15% 2	2374
	21st to end	Day	50% 4 11% 21% 13% 1	2400
May	1st to 10th	Day	46% 6% 13% 22% 13%	5797
	11th to 20th	Day	43% 6% 11% 25% 13% 3	6036
	21st to end	Day	43% 5% 9% 27% 16% 1	6949
June	1st to 10th	Day	33% 6% 15% 29% 16% 1	2800
	11th to 20th	Day	31% 6% 13% 30% 17% 3	2800
	21st to end	Day	28% 6% 17% 29% 16% 4	2800
July	1st to 10th	Day	37% 4 11% 27% 20% 2	6291
	11th to 20th	Day	37% 4 15% 30% 13% 1	5921
	21st to end	Day	34% 5% 20% 32% 9% 1	6240
August	1st to 10th	Day	26% 5% 19% 34% 16% 1	4220
	11th to 20th	Day	37% 4 14% 29% 15% 1	4083
	21st to end	Day	28% 4 15% 35% 14% 4	4311
September	1st to 10th	Day	33% 4 10% 27% 19% 6%	2400
	11th to 20th	Day	32% 4 9% 27% 25% 3	2400
	21st to end	Day	30% 5% 8% 28% 25% 4	2085
October	1st to 10th	Day	20% 2 5% 20% 40% 14%	3190
	11th to 20th	Day	23% 2 4 22% 39% 10%	3140
	21st to end	Day	35% 3 8% 25% 28% 2	3428
November	1st to 10th	Day	33% 3 12% 24% 22% 5%	1901
	11th to 20th	Day	38% 2 9% 23% 23% 5%	1770
	21st to end	Day	42% 4 8% 30% 14% 2	1600
December	1st to 10th	Day	36% 2 10% 36% 16% 1	2610
	11th to 20th	Day	41% 2 12% 28% 15% 1	3005
	21st to end	Day	66% 3 10% 13% 7% 1	3982
January	1st to 10th	Night	57% 3 8% 21% 11% 1	6095
	11th to 20th	Night	51% 3 7% 22% 13% 3	5900
	21st to end	Night	49% 2 9% 19% 17% 4	6490
February	1st to 10th	Night	50% 4 10% 21% 13% 2	2600
	11th to 20th	Night	45% 4 11% 20% 17% 3	2489
	21st to end	Night	44% 3 9% 23% 17% 4	1980
March	1st to 10th	Night	44% 3 7% 21% 21% 4	4963
	11th to 20th	Night	33% 4 7% 23% 26% 7%	4980
	21st to end	Night	48% 5% 13% 23% 9% 2	5425
April	1st to 10th	Night	36% 4 11% 26% 20% 4	2000
	11th to 20th	Night	40% 3 9% 24% 17% 6%	1975
	21st to end	Night	45% 4 10% 25% 15% 1	2000
May	1st to 10th	Night	44% 6% 15% 19% 14% 1	4176
	11th to 20th	Night	38% 6% 10% 24% 16% 5%	3881
	21st to end	Night	40% 5% 11% 24% 19% 2	3950
June	1st to 10th	Night	28% 6% 16% 31% 16% 3	1600
	11th to 20th	Night	28% 5% 12% 28% 23% 4	1600
	21st to end	Night	19% 4 18% 31% 21% 7%	1600
July	1st to 10th	Night	34% 4 11% 27% 22% 2	3580
	11th to 20th	Night	30% 5% 13% 36% 15% 2	3930
	21st to end	Night	28% 5% 19% 37% 10% 1	4320
August	1st to 10th	Night	19% 3 21% 32% 23% 2	2916
	11th to 20th	Night	34% 4 12% 30% 18% 3	3036
	21st to end	Night	22% 4 16% 37% 17% 4	3586
September	1st to 10th	Night	29% 3 11% 25% 25% 7%	2000
	11th to 20th	Night	31% 4 10% 26% 25% 5%	2000
	21st to end	Night	30% 3 8% 27% 28% 4	2289
October	1st to 10th	Night	16% 2 5% 21% 44% 11%	3837
	11th to 20th	Night	23% 2 7% 21% 31% 16%	3779
	21st to end	Night	35% 3 6% 29% 25% 3	4120
November	1st to 10th	Night	31% 4 11% 28% 21% 6%	2395
	11th to 20th	Night	37% 2 6% 25% 24% 5%	2625
	21st to end	Night	41% 3 10% 27% 17% 2	2800
December	1st to 10th	Night	37% 3 9% 36% 14% 1	4580
	11th to 20th	Night	45% 2 10% 25% 17% 1	5201
	21st to end	Night	64% 3 11% 15% 6% 1	6996

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	24% 15% 38% 17% 5%	300
	11th to 20th	Day	30% 16% 40% 13% 1	300
	21st to end	Day	21% 16% 43% 17% 4	330
February	1st to 10th	Day	25% 14% 44% 13% 3	300
	11th to 20th	Day	28% 23% 33% 11% 5%	300
	21st to end	Day	28% 20% 39% 11% 3	249
March	1st to 10th	Day	19% 19% 45% 15% 2	300
	11th to 20th	Day	29% 15% 34% 19% 2 1	300
	21st to end	Day	33% 19% 30% 14% 4	345
April	1st to 10th	Day	23% 15% 32% 22% 6% 1	500
	11th to 20th	Day	25% 15% 32% 19% 8%	492
	21st to end	Day	28% 11% 31% 23% 7% 1	500
May	1st to 10th	Day	20% 11% 32% 25% 11% 1	652
	11th to 20th	Day	20% 8% 24% 28% 17% 3	725
	21st to end	Day	18% 5% 28% 27% 15% 6%	789
June	1st to 10th	Day	10% 3 18% 34% 25% 9%	730
	11th to 20th	Day	10% 3 20% 39% 23% 5%	730
	21st to end	Day	7% 4 28% 37% 19% 5%	730
July	1st to 10th	Day	13% 2 10% 32% 30% 14%	721
	11th to 20th	Day	7% 2 18% 36% 28% 9%	718
	21st to end	Day	10% 1 13% 32% 33% 11%	794
August	1st to 10th	Day	9% 1 15% 39% 27% 8%	726
	11th to 20th	Day	11% 2 15% 35% 29% 8%	640
	21st to end	Day	9% 2 11% 32% 33% 13%	583
September	1st to 10th	Day	11% 2 13% 34% 32% 8%	530
	11th to 20th	Day	8% 2 16% 34% 29% 12%	530
	21st to end	Day	10% 7% 25% 30% 19% 8%	335
October	1st to 10th	Day	14% 4 28% 29% 19% 6%	309
	11th to 20th	Day	18% 17% 31% 25% 8% 1	300
	21st to end	Day	29% 17% 29% 22% 3 1	330
November	1st to 10th	Day	20% 7% 39% 22% 9% 3	300
	11th to 20th	Day	22% 15% 30% 25% 7% 1	300
	21st to end	Day	29% 15% 26% 25% 4 1	300
December	1st to 10th	Day	17% 17% 40% 16% 8% 1	300
	11th to 20th	Day	21% 19% 37% 19% 4	300
	21st to end	Day	29% 17% 37% 15% 2	330
January	1st to 10th	Night	17% 16% 36% 26% 5%	1000
	11th to 20th	Night	21% 17% 36% 21% 5%	1000
	21st to end	Night	19% 13% 39% 26% 2	1100
February	1st to 10th	Night	21% 15% 37% 24% 4	1000
	11th to 20th	Night	21% 16% 36% 23% 3	934
	21st to end	Night	23% 14% 40% 20% 3	660
March	1st to 10th	Night	21% 15% 36% 24% 4	620
	11th to 20th	Night	25% 9% 32% 28% 5%	600
	21st to end	Night	26% 12% 34% 22% 5%	660
April	1st to 10th	Night	17% 13% 34% 31% 5%	600
	11th to 20th	Night	20% 11% 32% 28% 8%	593
	21st to end	Night	20% 6% 38% 28% 8%	600
May	1st to 10th	Night	17% 5% 31% 35% 11% 1	600
	11th to 20th	Night	15% 4 25% 38% 16% 1	591
	21st to end	Night	14% 3 26% 32% 22% 2	650
June	1st to 10th	Night	10% 1 17% 42% 28% 3	600
	11th to 20th	Night	9% 1 20% 45% 24% 2	600
	21st to end	Night	5% 2 21% 50% 21% 2	600
July	1st to 10th	Night	10% 9% 38% 37% 6%	585
	11th to 20th	Night	6% 1 12% 43% 35% 3	582
	21st to end	Night	7% 1 12% 41% 35% 3	657
August	1st to 10th	Night	7% 1 11% 45% 33% 3	597
	11th to 20th	Night	8% 1 11% 46% 31% 4	594
	21st to end	Night	7% 1 10% 37% 40% 4	660
September	1st to 10th	Night	13% 1 13% 38% 31% 5%	600
	11th to 20th	Night	10% 2 12% 38% 32% 6%	600
	21st to end	Night	10% 3 21% 36% 26% 4	699
October	1st to 10th	Night	9% 4 26% 35% 23% 3	773
	11th to 20th	Night	15% 9% 35% 30% 10%	760
	21st to end	Night	21% 10% 32% 28% 8%	836
November	1st to 10th	Night	15% 9% 34% 32% 10%	780
	11th to 20th	Night	18% 12% 33% 29% 8%	825
	21st to end	Night	22% 10% 36% 25% 6%	1000
December	1st to 10th	Night	21% 12% 34% 26% 7% 1	1000
	11th to 20th	Night	23% 9% 35% 28% 5%	1000
	21st to end	Night	25% 13% 33% 26% 3	1100

Page generated at 2025-10-01 00:39:08. Version ac07

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