Barnes City
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Barnes City clear sky chart from 2005-11-06 to 2025-09-19.

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 8% 5% 4 4 4 5% 7% 39%	126632
	Night	12% 8% 3 8% 4 4 4 3 5% 6% 42%	122689
Transparency	Day	43% 5% 12% 24% 14% 2	130230
	Night	42% 4 12% 24% 15% 2	127168
Seeing	Day	15% 10% 30% 26% 15% 4	17076
	Night	16% 9% 32% 31% 12% 1	26831

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	8% 12% 5% 20% 8% 7% 5% 3 4 5% 24%	3617
	11th to 20th	Day	7% 9% 4 11% 7% 5% 7% 5% 6% 6% 32%	3919
	21st to end	Day	11% 14% 6% 13% 6% 5% 4 4 4 5% 29%	4488
February	1st to 10th	Day	12% 13% 5% 10% 6% 5% 5% 4 5% 7% 29%	1800
	11th to 20th	Day	12% 12% 4 7% 5% 4 4 4 5% 8% 34%	1754
	21st to end	Day	14% 9% 5% 9% 5% 4 4 3 5% 6% 37%	1640
March	1st to 10th	Day	18% 10% 3 5% 3 3 2 2 3 5% 45%	4819
	11th to 20th	Day	9% 6% 2 6% 5% 4 4 3 5% 7% 48%	4980
	21st to end	Day	20% 12% 4 8% 5% 5% 4 4 5% 6% 26%	5553
April	1st to 10th	Day	17% 11% 3 6% 5% 4 4 3 5% 6% 35%	2400
	11th to 20th	Day	16% 9% 2 7% 5% 5% 5% 4 5% 8% 34%	2374
	21st to end	Day	21% 9% 3 7% 4 4 4 3 5% 7% 32%	2450
May	1st to 10th	Day	15% 7% 3 7% 5% 5% 5% 4 6% 7% 37%	5926
	11th to 20th	Day	16% 5% 2 5% 3 4 3 4 5% 7% 46%	6319
	21st to end	Day	15% 7% 3 7% 5% 5% 5% 4 6% 7% 37%	6935
June	1st to 10th	Day	10% 5% 2 6% 5% 4 5% 5% 7% 9% 44%	2800
	11th to 20th	Day	9% 4 2 6% 5% 5% 4 4 6% 9% 46%	2800
	21st to end	Day	10% 6% 3 6% 6% 5% 5% 4 6% 9% 40%	2800
July	1st to 10th	Day	8% 7% 3 8% 4 5% 5% 4 7% 9% 40%	6360
	11th to 20th	Day	9% 5% 2 6% 4 4 5% 4 6% 8% 46%	6360
	21st to end	Day	10% 5% 2 7% 4 5% 5% 5% 7% 10% 40%	6544
August	1st to 10th	Day	7% 5% 2 6% 5% 4 5% 5% 8% 11% 44%	4234
	11th to 20th	Day	10% 6% 3 7% 5% 5% 5% 4 6% 9% 40%	4148
	21st to end	Day	7% 4 2 6% 4 4 4 4 6% 8% 49%	4312
September	1st to 10th	Day	13% 5% 2 5% 3 3 3 2 5% 6% 53%	2400
	11th to 20th	Day	9% 5% 2 5% 4 4 4 4 5% 9% 49%	2376
	21st to end	Day	11% 5% 2 5% 4 4 4 3 5% 7% 49%	1988
October	1st to 10th	Day	14% 6% 2 6% 4 3 4 2 4 6% 49%	1900
	11th to 20th	Day	16% 7% 2 6% 4 4 3 3 4 6% 46%	1900
	21st to end	Day	15% 10% 2 6% 5% 4 3 3 4 6% 42%	2090
November	1st to 10th	Day	10% 8% 2 6% 4 4 4 3 6% 8% 45%	1791
	11th to 20th	Day	15% 11% 2 7% 4 4 4 3 5% 7% 38%	1655
	21st to end	Day	15% 11% 4 7% 4 3 3 4 5% 8% 38%	1600
December	1st to 10th	Day	7% 9% 4 6% 4 4 3 3 5% 6% 49%	2610
	11th to 20th	Day	14% 10% 4 17% 6% 5% 5% 4 5% 5% 27%	3008
	21st to end	Day	24% 19% 8% 12% 4 4 3 3 3 4 16%	3982
January	1st to 10th	Night	10% 12% 6% 17% 5% 4 4 3 4 5% 30%	6348
	11th to 20th	Night	10% 12% 5% 11% 7% 5% 6% 4 7% 6% 28%	6056
	21st to end	Night	13% 13% 5% 11% 4 4 4 3 4 6% 32%	6490
February	1st to 10th	Night	13% 13% 4 9% 5% 4 4 3 4 6% 35%	2600
	11th to 20th	Night	12% 10% 3 8% 5% 4 4 3 5% 7% 40%	2533
	21st to end	Night	13% 10% 3 8% 4 5% 3 2 4 5% 42%	1988
March	1st to 10th	Night	17% 7% 3 6% 3 3 3 2 4 5% 47%	5063
	11th to 20th	Night	10% 7% 2 6% 4 3 3 3 5% 7% 50%	4980
	21st to end	Night	17% 11% 5% 11% 5% 4 4 3 5% 5% 29%	5376
April	1st to 10th	Night	15% 9% 3 7% 4 3 3 4 5% 5% 42%	2000
	11th to 20th	Night	14% 9% 3 6% 4 5% 4 4 5% 5% 40%	1975
	21st to end	Night	17% 8% 2 5% 4 3 4 3 5% 7% 40%	1945
May	1st to 10th	Night	16% 6% 2 6% 4 4 4 3 5% 7% 42%	3989
	11th to 20th	Night	12% 6% 2 5% 4 4 4 3 6% 6% 48%	3596
	21st to end	Night	15% 7% 2 6% 4 4 4 3 4 7% 43%	3942
June	1st to 10th	Night	6% 5% 2 5% 4 4 4 4 7% 9% 50%	1600
	11th to 20th	Night	7% 4 2 6% 4 4 4 4 6% 12% 47%	1600
	21st to end	Night	10% 5% 1 5% 3 5% 5% 4 7% 7% 47%	1600
July	1st to 10th	Night	9% 4 2 6% 4 4 5% 4 6% 10% 46%	3618
	11th to 20th	Night	7% 4 2 5% 3 4 4 3 5% 8% 55%	3617
	21st to end	Night	9% 6% 2 6% 4 4 4 4 6% 8% 47%	4310
August	1st to 10th	Night	4 4 2 5% 4 4 4 4 5% 9% 55%	2926
	11th to 20th	Night	8% 5% 2 4 3 3 4 3 5% 7% 57%	2910
	21st to end	Night	7% 4 2 6% 3 4 4 4 5% 8% 53%	3586
September	1st to 10th	Night	9% 5% 2 4 3 3 3 2 5% 6% 58%	2000
	11th to 20th	Night	10% 5% 1 5% 3 5% 3 3 5% 8% 52%	1980
	21st to end	Night	8% 5% 1 5% 3 4 3 3 4 8% 55%	2167
October	1st to 10th	Night	13% 6% 2 5% 3 3 3 3 4 6% 53%	2280
	11th to 20th	Night	13% 6% 3 6% 3 3 4 3 4 5% 51%	2280
	21st to end	Night	16% 8% 3 6% 5% 4 3 3 4 5% 43%	2508
November	1st to 10th	Night	10% 6% 2 5% 3 3 3 3 5% 7% 53%	2507
	11th to 20th	Night	13% 9% 3 6% 4 4 4 3 5% 7% 42%	2744
	21st to end	Night	16% 9% 4 7% 4 4 3 3 5% 6% 40%	2800
December	1st to 10th	Night	7% 9% 3 8% 4 4 4 4 5% 6% 48%	4580
	11th to 20th	Night	13% 9% 5% 11% 6% 5% 4 4 5% 5% 34%	5199
	21st to end	Night	22% 18% 7% 11% 5% 5% 3 3 4 4 18%	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	64% 3 11% 15% 7%	3618
	11th to 20th	Day	52% 3 10% 19% 14% 2	3919
	21st to end	Day	58% 4 12% 20% 6% 1	4488
February	1st to 10th	Day	54% 4 14% 19% 8% 1	1800
	11th to 20th	Day	49% 5% 13% 22% 10% 2	1763
	21st to end	Day	48% 3 12% 23% 10% 3	1640
March	1st to 10th	Day	45% 3 8% 25% 17% 1	4819
	11th to 20th	Day	36% 4 9% 30% 19% 2	4980
	21st to end	Day	58% 5% 16% 16% 5% 1	5555
April	1st to 10th	Day	50% 4 12% 24% 9%	2400
	11th to 20th	Day	48% 5% 12% 22% 11% 1	2374
	21st to end	Day	51% 5% 11% 20% 12% 1	2450
May	1st to 10th	Day	45% 5% 13% 19% 17% 1	5964
	11th to 20th	Day	38% 5% 11% 28% 16% 3	6323
	21st to end	Day	44% 6% 10% 25% 13% 1	6949
June	1st to 10th	Day	36% 6% 17% 24% 15% 2	2800
	11th to 20th	Day	34% 6% 12% 24% 20% 3	2800
	21st to end	Day	39% 7% 13% 24% 15% 2	2800
July	1st to 10th	Day	39% 6% 14% 29% 12% 1	6291
	11th to 20th	Day	35% 6% 13% 29% 15% 1	6285
	21st to end	Day	36% 9% 19% 23% 12% 1	6359
August	1st to 10th	Day	32% 7% 17% 30% 14% 1	4220
	11th to 20th	Day	40% 6% 13% 26% 15% 1	4187
	21st to end	Day	32% 6% 14% 29% 16% 2	4311
September	1st to 10th	Day	32% 5% 11% 25% 22% 4	2400
	11th to 20th	Day	31% 5% 14% 30% 19% 1	2376
	21st to end	Day	35% 4 10% 32% 18% 2	1988
October	1st to 10th	Day	23% 2 6% 25% 42% 2	3160
	11th to 20th	Day	29% 2 9% 27% 27% 6%	3140
	21st to end	Day	40% 3 10% 28% 16% 3	3428
November	1st to 10th	Day	38% 5% 15% 25% 16% 3	1791
	11th to 20th	Day	46% 4 13% 21% 15% 1	1655
	21st to end	Day	46% 5% 15% 24% 10% 1	1600
December	1st to 10th	Day	37% 3 14% 38% 7% 1	2610
	11th to 20th	Day	60% 4 11% 14% 10% 1	3005
	21st to end	Day	74% 3 8% 11% 3	3982
January	1st to 10th	Night	58% 3 13% 18% 8% 1	6348
	11th to 20th	Night	55% 4 12% 13% 15% 2	6056
	21st to end	Night	55% 3 10% 19% 12% 1	6490
February	1st to 10th	Night	52% 3 11% 22% 11% 1	2600
	11th to 20th	Night	45% 4 11% 26% 12% 2	2534
	21st to end	Night	45% 3 11% 23% 16% 3	1988
March	1st to 10th	Night	41% 3 6% 29% 19% 2	5063
	11th to 20th	Night	34% 3 8% 32% 18% 5%	4980
	21st to end	Night	58% 4 16% 14% 6% 2	5376
April	1st to 10th	Night	43% 4 10% 27% 14% 2	2000
	11th to 20th	Night	44% 5% 10% 22% 16% 3	1975
	21st to end	Night	44% 5% 13% 22% 13% 3	1945
May	1st to 10th	Night	41% 5% 9% 24% 19% 2	4016
	11th to 20th	Night	36% 5% 13% 26% 17% 4	3597
	21st to end	Night	41% 6% 10% 24% 18% 2	3950
June	1st to 10th	Night	30% 7% 16% 28% 15% 4	1600
	11th to 20th	Night	29% 7% 14% 25% 22% 4	1600
	21st to end	Night	33% 8% 13% 24% 18% 4	1600
July	1st to 10th	Night	33% 6% 13% 31% 15% 2	3580
	11th to 20th	Night	28% 6% 16% 29% 20% 1	3572
	21st to end	Night	34% 8% 17% 26% 14% 1	4185
August	1st to 10th	Night	26% 6% 17% 32% 17% 2	2916
	11th to 20th	Night	27% 6% 15% 34% 16% 1	2937
	21st to end	Night	28% 6% 13% 29% 17% 6%	3586
September	1st to 10th	Night	28% 5% 9% 29% 26% 3	2000
	11th to 20th	Night	32% 4 9% 33% 18% 3	1980
	21st to end	Night	29% 5% 9% 32% 23% 3	2167
October	1st to 10th	Night	23% 3 6% 24% 40% 4	3800
	11th to 20th	Night	26% 3 9% 24% 30% 8%	3779
	21st to end	Night	44% 3 9% 23% 18% 3	4120
November	1st to 10th	Night	32% 4 15% 27% 18% 4	2507
	11th to 20th	Night	43% 4 12% 25% 14% 2	2744
	21st to end	Night	47% 3 12% 26% 12% 1	2800
December	1st to 10th	Night	38% 4 12% 36% 9%	4580
	11th to 20th	Night	52% 4 12% 24% 8%	5201
	21st to end	Night	70% 4 9% 12% 5%	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	20% 14% 33% 22% 10% 1	300
	11th to 20th	Day	21% 14% 43% 18% 3	300
	21st to end	Day	17% 13% 42% 23% 4	330
February	1st to 10th	Day	19% 19% 38% 20% 4	300
	11th to 20th	Day	20% 16% 37% 20% 7%	300
	21st to end	Day	22% 14% 44% 15% 4	249
March	1st to 10th	Day	20% 19% 40% 18% 4	300
	11th to 20th	Day	20% 18% 34% 20% 6% 1	300
	21st to end	Day	33% 18% 31% 15% 3 1	370
April	1st to 10th	Day	25% 17% 32% 20% 7%	500
	11th to 20th	Day	22% 18% 30% 22% 8% 1	492
	21st to end	Day	23% 15% 35% 19% 8% 1	550
May	1st to 10th	Day	19% 12% 36% 23% 8% 2	703
	11th to 20th	Day	21% 12% 26% 26% 13% 3	725
	21st to end	Day	17% 10% 29% 28% 13% 4	789
June	1st to 10th	Day	9% 5% 28% 31% 21% 6%	730
	11th to 20th	Day	10% 5% 29% 33% 19% 3	730
	21st to end	Day	11% 7% 32% 31% 15% 4	730
July	1st to 10th	Day	8% 4 19% 31% 26% 12%	721
	11th to 20th	Day	8% 4 25% 33% 23% 8%	718
	21st to end	Day	8% 3 22% 35% 28% 4	794
August	1st to 10th	Day	7% 3 24% 34% 26% 6%	726
	11th to 20th	Day	11% 4 20% 35% 24% 7%	705
	21st to end	Day	8% 4 18% 35% 28% 7%	583
September	1st to 10th	Day	14% 6% 19% 29% 24% 8%	530
	11th to 20th	Day	9% 4 19% 37% 23% 8%	522
	21st to end	Day	14% 9% 30% 23% 20% 4	319
October	1st to 10th	Day	19% 9% 27% 26% 14% 5%	300
	11th to 20th	Day	18% 21% 33% 20% 7% 1	300
	21st to end	Day	21% 14% 36% 20% 7% 2	330
November	1st to 10th	Day	17% 10% 41% 20% 10% 2	300
	11th to 20th	Day	19% 21% 34% 18% 7% 2	300
	21st to end	Day	22% 13% 38% 23% 5%	300
December	1st to 10th	Day	14% 13% 44% 20% 9% 2	300
	11th to 20th	Day	14% 18% 36% 23% 8% 1	300
	21st to end	Day	30% 16% 36% 15% 4	330
January	1st to 10th	Night	13% 13% 40% 26% 8%	1000
	11th to 20th	Night	18% 13% 37% 26% 7%	1000
	21st to end	Night	19% 12% 37% 26% 5%	1100
February	1st to 10th	Night	20% 10% 40% 24% 5%	1000
	11th to 20th	Night	16% 13% 38% 28% 4	979
	21st to end	Night	19% 13% 41% 22% 4 1	668
March	1st to 10th	Night	19% 13% 39% 23% 6% 1	671
	11th to 20th	Night	17% 11% 36% 27% 8% 1	600
	21st to end	Night	23% 12% 39% 20% 5% 1	660
April	1st to 10th	Night	19% 13% 41% 24% 3	600
	11th to 20th	Night	20% 14% 34% 26% 6%	593
	21st to end	Night	21% 9% 37% 25% 8% 1	600
May	1st to 10th	Night	19% 6% 36% 32% 7% 1	600
	11th to 20th	Night	17% 10% 30% 31% 12%	591
	21st to end	Night	14% 6% 30% 34% 16%	650
June	1st to 10th	Night	8% 4 24% 45% 18% 1	600
	11th to 20th	Night	9% 4 25% 47% 16% 1	600
	21st to end	Night	10% 6% 28% 40% 15% 1	600
July	1st to 10th	Night	6% 1 14% 44% 32% 3	585
	11th to 20th	Night	5% 2 19% 43% 28% 2	582
	21st to end	Night	8% 2 16% 47% 24% 2	657
August	1st to 10th	Night	6% 2 17% 47% 26% 2	597
	11th to 20th	Night	8% 2 14% 44% 29% 3	594
	21st to end	Night	8% 2 15% 43% 29% 2	660
September	1st to 10th	Night	10% 4 21% 38% 24% 4	600
	11th to 20th	Night	13% 2 18% 40% 24% 3	594
	21st to end	Night	11% 5% 29% 35% 18% 1	670
October	1st to 10th	Night	16% 6% 28% 32% 16% 2	760
	11th to 20th	Night	15% 12% 34% 31% 8%	760
	21st to end	Night	20% 11% 34% 27% 8%	836
November	1st to 10th	Night	14% 9% 38% 30% 8% 1	780
	11th to 20th	Night	17% 15% 39% 23% 7%	944
	21st to end	Night	20% 11% 37% 25% 7%	1000
December	1st to 10th	Night	17% 12% 39% 27% 4 1	1000
	11th to 20th	Night	21% 10% 33% 29% 7% 1	1000
	21st to end	Night	25% 13% 33% 24% 5%	1100

Page generated at 2025-09-16 00:49:17. Version ac07

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