Bearcat Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bearcat Observatory clear sky chart from 2005-11-06 to 2026-07-31.

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	11% 7% 3 7% 4 4 4 3 5% 7% 43%	138253
	Night	11% 7% 3 7% 4 4 4 3 5% 6% 47%	135059
Transparency	Day	40% 4 12% 26% 16% 2	141863
	Night	38% 4 11% 26% 18% 3	139530
Seeing	Day	15% 10% 30% 28% 14% 3	18167
	Night	14% 9% 33% 32% 11% 1	27970

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% 10% 4 11% 7% 4 5% 3 5% 6% 34%	5247
	11th to 20th	Day	5% 9% 3 9% 6% 6% 7% 4 5% 7% 40%	5310
	21st to end	Day	8% 12% 5% 12% 6% 6% 4 3 4 5% 34%	5812
February	1st to 10th	Day	11% 11% 4 8% 6% 5% 5% 4 5% 8% 33%	1890
	11th to 20th	Day	11% 9% 5% 7% 4 5% 4 4 6% 7% 38%	1844
	21st to end	Day	10% 9% 3 6% 5% 4 4 3 5% 7% 45%	1737
March	1st to 10th	Day	16% 9% 3 6% 3 3 3 3 3 4 48%	5046
	11th to 20th	Day	10% 7% 2 6% 4 4 4 3 4 8% 49%	5090
	21st to end	Day	15% 12% 5% 8% 5% 5% 4 4 5% 7% 30%	5583
April	1st to 10th	Day	16% 8% 3 6% 5% 3 3 3 4 6% 42%	2435
	11th to 20th	Day	15% 8% 2 7% 5% 3 4 4 5% 6% 40%	2494
	21st to end	Day	20% 8% 3 6% 4 4 4 4 5% 7% 36%	2719
May	1st to 10th	Day	12% 7% 3 6% 4 4 5% 3 5% 7% 44%	7617
	11th to 20th	Day	13% 6% 2 5% 4 4 4 3 5% 6% 48%	7627
	21st to end	Day	17% 8% 3 7% 4 4 4 3 5% 7% 38%	8929
June	1st to 10th	Day	8% 5% 2 6% 5% 4 5% 5% 6% 9% 46%	2940
	11th to 20th	Day	8% 5% 3 5% 4 4 4 4 6% 9% 47%	2940
	21st to end	Day	9% 6% 1 5% 5% 5% 5% 5% 6% 9% 45%	2940
July	1st to 10th	Day	9% 5% 2 6% 4 4 5% 4 7% 10% 45%	6343
	11th to 20th	Day	8% 5% 2 6% 4 4 5% 4 6% 8% 47%	6030
	21st to end	Day	7% 4 2 5% 4 3 4 4 6% 9% 50%	6553
August	1st to 10th	Day	6% 4 2 5% 4 4 5% 3 7% 10% 48%	4234
	11th to 20th	Day	11% 6% 2 5% 4 4 5% 4 6% 9% 44%	4171
	21st to end	Day	6% 5% 2 7% 4 4 5% 4 6% 7% 50%	4454
September	1st to 10th	Day	11% 4 2 5% 4 3 3 3 6% 6% 53%	2400
	11th to 20th	Day	9% 4 2 6% 4 4 4 3 6% 8% 50%	2226
	21st to end	Day	11% 4 2 5% 3 3 4 3 5% 6% 56%	2185
October	1st to 10th	Day	13% 6% 2 5% 3 3 3 3 4 6% 51%	2000
	11th to 20th	Day	12% 8% 2 4 3 3 2 3 3 5% 55%	2000
	21st to end	Day	13% 9% 3 6% 3 3 3 3 6% 5% 46%	2200
November	1st to 10th	Day	9% 7% 2 5% 3 4 3 2 5% 7% 52%	1997
	11th to 20th	Day	11% 8% 2 6% 4 4 4 2 4 6% 48%	1732
	21st to end	Day	15% 10% 4 7% 4 3 3 4 6% 6% 41%	1680
December	1st to 10th	Day	5% 5% 2 7% 5% 4 4 3 4 6% 54%	2690
	11th to 20th	Day	10% 10% 3 9% 5% 4 3 3 5% 5% 42%	3088
	21st to end	Day	18% 12% 6% 13% 5% 4 4 3 4 5% 24%	4070
January	1st to 10th	Night	10% 9% 4 16% 6% 5% 4 3 5% 5% 31%	7661
	11th to 20th	Night	6% 7% 3 8% 4 5% 6% 4 7% 6% 44%	7680
	21st to end	Night	10% 13% 5% 11% 5% 5% 4 2 3 4 38%	8402
February	1st to 10th	Night	11% 10% 3 9% 5% 4 4 3 5% 5% 39%	2730
	11th to 20th	Night	10% 9% 3 8% 5% 4 3 4 5% 6% 42%	2663
	21st to end	Night	9% 8% 3 7% 4 4 3 3 5% 5% 49%	2087
March	1st to 10th	Night	16% 7% 2 5% 3 3 3 3 4 5% 50%	5029
	11th to 20th	Night	10% 5% 2 5% 3 3 3 3 5% 6% 55%	5090
	21st to end	Night	15% 10% 3 9% 4 4 5% 3 5% 7% 36%	5588
April	1st to 10th	Night	12% 8% 2 6% 3 3 4 3 6% 6% 47%	2184
	11th to 20th	Night	12% 8% 2 6% 4 4 3 4 5% 6% 46%	2075
	21st to end	Night	16% 9% 3 5% 4 3 4 3 4 6% 42%	1896
May	1st to 10th	Night	11% 6% 2 6% 4 4 4 3 5% 7% 48%	5266
	11th to 20th	Night	14% 6% 2 4 3 3 3 2 4 6% 52%	5265
	21st to end	Night	17% 7% 2 7% 4 4 4 3 5% 6% 41%	5240
June	1st to 10th	Night	6% 3 2 4 4 3 4 5% 6% 9% 54%	1680
	11th to 20th	Night	6% 3 1 4 3 3 4 4 8% 11% 51%	1680
	21st to end	Night	6% 4 1 4 3 4 4 3 6% 9% 56%	1680
July	1st to 10th	Night	8% 4 2 5% 4 4 4 4 7% 9% 50%	3836
	11th to 20th	Night	5% 4 2 6% 4 4 4 3 6% 8% 53%	4167
	21st to end	Night	8% 4 2 5% 4 4 5% 4 7% 9% 49%	4539
August	1st to 10th	Night	3 2 1 4 3 3 4 3 5% 10% 60%	2926
	11th to 20th	Night	12% 6% 2 5% 3 3 3 2 4 6% 53%	2888
	21st to end	Night	6% 3 2 5% 3 3 3 3 5% 8% 58%	3448
September	1st to 10th	Night	10% 4 1 4 3 3 3 3 5% 8% 57%	2000
	11th to 20th	Night	10% 4 2 4 4 4 4 3 5% 7% 54%	2170
	21st to end	Night	9% 4 2 5% 3 3 3 3 4 6% 59%	2200
October	1st to 10th	Night	13% 6% 2 4 2 3 3 3 5% 6% 53%	2395
	11th to 20th	Night	13% 7% 2 4 2 3 3 2 4 5% 55%	2400
	21st to end	Night	15% 6% 2 5% 3 3 3 2 4 5% 51%	2640
November	1st to 10th	Night	8% 4 2 4 3 3 4 3 5% 7% 57%	2518
	11th to 20th	Night	10% 6% 2 6% 5% 3 3 3 5% 7% 50%	2887
	21st to end	Night	14% 8% 3 5% 4 3 3 3 5% 5% 48%	2940
December	1st to 10th	Night	6% 7% 2 6% 4 4 4 3 5% 6% 53%	4720
	11th to 20th	Night	11% 7% 3 8% 4 3 4 3 5% 7% 44%	5339
	21st to end	Night	19% 14% 6% 11% 4 3 3 3 4 5% 28%	7150

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	51% 4 11% 21% 12% 1	5248
	11th to 20th	Day	46% 2 10% 21% 16% 5%	5310
	21st to end	Day	54% 3 12% 20% 11% 1	5812
February	1st to 10th	Day	49% 6% 13% 21% 10% 2	1890
	11th to 20th	Day	44% 6% 12% 22% 13% 2	1853
	21st to end	Day	40% 4 12% 25% 16% 2	1737
March	1st to 10th	Day	41% 3 8% 24% 18% 5%	5046
	11th to 20th	Day	36% 4 8% 25% 24% 3	5090
	21st to end	Day	53% 6% 18% 18% 4 2	5585
April	1st to 10th	Day	44% 5% 11% 25% 14% 2	2435
	11th to 20th	Day	44% 5% 12% 22% 14% 2	2494
	21st to end	Day	48% 6% 10% 25% 11% 1	2719
May	1st to 10th	Day	40% 4 9% 27% 18% 1	7655
	11th to 20th	Day	37% 4 10% 28% 18% 3	7631
	21st to end	Day	46% 4 9% 25% 15% 1	8943
June	1st to 10th	Day	33% 8% 15% 28% 14% 2	2940
	11th to 20th	Day	33% 7% 13% 27% 18% 2	2940
	21st to end	Day	34% 7% 15% 27% 14% 3	2940
July	1st to 10th	Day	35% 3 15% 32% 14% 1	6277
	11th to 20th	Day	36% 4 13% 27% 18% 2	5961
	21st to end	Day	30% 4 17% 35% 11% 2	6371
August	1st to 10th	Day	30% 5% 15% 31% 17% 1	4220
	11th to 20th	Day	38% 5% 15% 26% 15%	4210
	21st to end	Day	33% 4 15% 29% 14% 5%	4453
September	1st to 10th	Day	31% 6% 11% 28% 19% 4	2400
	11th to 20th	Day	32% 6% 12% 28% 20% 1	2226
	21st to end	Day	30% 5% 9% 31% 25% 2	2185
October	1st to 10th	Day	22% 2 6% 20% 47% 2	3260
	11th to 20th	Day	22% 2 7% 29% 32% 8%	3240
	21st to end	Day	35% 3 10% 27% 22% 3	3538
November	1st to 10th	Day	32% 4 15% 27% 20% 3	1997
	11th to 20th	Day	38% 3 12% 28% 17% 2	1732
	21st to end	Day	43% 4 12% 26% 14% 1	1680
December	1st to 10th	Day	33% 4 18% 31% 15% 1	2690
	11th to 20th	Day	44% 3 15% 26% 10% 1	3085
	21st to end	Day	64% 3 12% 15% 6%	4070
January	1st to 10th	Night	55% 4 12% 18% 10% 1	7662
	11th to 20th	Night	40% 3 9% 26% 19% 3	7680
	21st to end	Night	51% 3 12% 17% 15% 3	8402
February	1st to 10th	Night	46% 5% 12% 21% 14% 3	2730
	11th to 20th	Night	42% 5% 11% 23% 16% 3	2664
	21st to end	Night	38% 4 11% 22% 21% 5%	2087
March	1st to 10th	Night	39% 4 7% 25% 23% 3	5029
	11th to 20th	Night	32% 4 6% 29% 23% 7%	5090
	21st to end	Night	48% 5% 16% 22% 7% 1	5588
April	1st to 10th	Night	36% 6% 11% 26% 18% 3	2184
	11th to 20th	Night	38% 7% 10% 26% 16% 3	2075
	21st to end	Night	43% 6% 10% 24% 15% 1	1896
May	1st to 10th	Night	37% 4 8% 27% 21% 3	5293
	11th to 20th	Night	35% 4 9% 24% 24% 5%	5266
	21st to end	Night	44% 4 10% 24% 16% 1	5251
June	1st to 10th	Night	24% 8% 19% 30% 15% 4	1680
	11th to 20th	Night	24% 8% 16% 29% 20% 4	1680
	21st to end	Night	23% 7% 18% 30% 18% 4	1680
July	1st to 10th	Night	32% 3 14% 27% 20% 4	3796
	11th to 20th	Night	30% 3 17% 28% 21% 2	4116
	21st to end	Night	31% 4 17% 32% 15% 1	4410
August	1st to 10th	Night	21% 5% 17% 33% 23% 2	2916
	11th to 20th	Night	34% 3 13% 29% 20% 1	2915
	21st to end	Night	26% 4 16% 30% 18% 6%	3448
September	1st to 10th	Night	27% 6% 11% 26% 24% 7%	2000
	11th to 20th	Night	29% 5% 11% 32% 21% 2	2170
	21st to end	Night	27% 4 8% 30% 27% 3	2200
October	1st to 10th	Night	21% 2 6% 19% 49% 3	3915
	11th to 20th	Night	23% 2 6% 28% 31% 9%	3899
	21st to end	Night	37% 3 7% 28% 24% 2	4252
November	1st to 10th	Night	27% 5% 14% 27% 23% 4	2518
	11th to 20th	Night	34% 4 10% 31% 19% 3	2887
	21st to end	Night	39% 4 10% 28% 17% 2	2940
December	1st to 10th	Night	33% 3 12% 37% 14% 1	4720
	11th to 20th	Night	41% 3 14% 28% 13% 1	5341
	21st to end	Night	61% 3 10% 19% 6% 1	7150

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% 12% 37% 24% 6%	330
	11th to 20th	Day	18% 19% 38% 20% 4	330
	21st to end	Day	15% 10% 45% 27% 4	363
February	1st to 10th	Day	15% 18% 44% 19% 3 1	330
	11th to 20th	Day	15% 20% 40% 19% 5%	330
	21st to end	Day	13% 20% 44% 19% 3	273
March	1st to 10th	Day	20% 15% 42% 21% 2 1	330
	11th to 20th	Day	27% 12% 33% 24% 4 1	330
	21st to end	Day	30% 20% 33% 13% 3	363
April	1st to 10th	Day	27% 13% 37% 18% 5% 1	455
	11th to 20th	Day	19% 17% 36% 21% 6%	532
	21st to end	Day	23% 17% 35% 18% 7% 1	739
May	1st to 10th	Day	17% 14% 33% 26% 8% 2	753
	11th to 20th	Day	18% 11% 32% 25% 12% 2	775
	21st to end	Day	19% 9% 27% 27% 15% 2	844
June	1st to 10th	Day	9% 4 23% 33% 24% 7%	780
	11th to 20th	Day	8% 6% 28% 36% 19% 4	780
	21st to end	Day	10% 6% 37% 32% 13% 3	780
July	1st to 10th	Day	9% 3 18% 32% 29% 10%	771
	11th to 20th	Day	8% 2 20% 35% 26% 9%	768
	21st to end	Day	8% 2 15% 42% 27% 6%	845
August	1st to 10th	Day	9% 2 20% 40% 24% 6%	726
	11th to 20th	Day	10% 3 19% 36% 27% 5%	715
	21st to end	Day	8% 3 19% 33% 29% 8%	673
September	1st to 10th	Day	13% 4 22% 31% 25% 6%	530
	11th to 20th	Day	8% 3 21% 39% 21% 8%	356
	21st to end	Day	15% 5% 27% 29% 19% 5%	330
October	1st to 10th	Day	17% 8% 28% 28% 13% 6%	330
	11th to 20th	Day	12% 20% 38% 22% 7% 1	330
	21st to end	Day	19% 17% 34% 23% 6% 2	363
November	1st to 10th	Day	15% 13% 41% 24% 7% 2	330
	11th to 20th	Day	18% 14% 38% 22% 7% 1	330
	21st to end	Day	23% 13% 35% 22% 7%	330
December	1st to 10th	Day	8% 17% 41% 27% 6% 2	330
	11th to 20th	Day	19% 16% 35% 23% 6% 1	330
	21st to end	Day	22% 17% 39% 20% 2	363
January	1st to 10th	Night	11% 13% 40% 30% 6%	1050
	11th to 20th	Night	14% 15% 39% 25% 6%	1050
	21st to end	Night	14% 12% 43% 27% 4	1155
February	1st to 10th	Night	16% 11% 42% 26% 4	1050
	11th to 20th	Night	16% 13% 41% 26% 4	1029
	21st to end	Night	14% 15% 44% 21% 5% 1	703
March	1st to 10th	Night	16% 14% 39% 26% 5%	630
	11th to 20th	Night	20% 9% 39% 27% 5%	630
	21st to end	Night	25% 13% 38% 19% 5%	693
April	1st to 10th	Night	16% 13% 41% 26% 4	630
	11th to 20th	Night	15% 14% 41% 24% 5%	623
	21st to end	Night	20% 11% 35% 28% 5%	630
May	1st to 10th	Night	15% 10% 36% 33% 6% 1	630
	11th to 20th	Night	16% 10% 32% 30% 11% 1	621
	21st to end	Night	14% 7% 29% 36% 13% 1	683
June	1st to 10th	Night	6% 4 25% 44% 20% 1	630
	11th to 20th	Night	8% 3 27% 43% 17%	630
	21st to end	Night	7% 3 33% 43% 14%	630
July	1st to 10th	Night	7% 2 16% 44% 30% 2	615
	11th to 20th	Night	5% 1 15% 48% 29% 2	612
	21st to end	Night	6% 2 16% 47% 28% 2	687
August	1st to 10th	Night	5% 1 21% 48% 24% 1	597
	11th to 20th	Night	9% 2 13% 47% 26% 3	594
	21st to end	Night	9% 2 15% 43% 28% 3	660
September	1st to 10th	Night	11% 2 21% 41% 23% 2	600
	11th to 20th	Night	12% 3 20% 41% 24% 1	600
	21st to end	Night	10% 4 28% 41% 17% 1	600
October	1st to 10th	Night	15% 6% 29% 33% 16% 2	795
	11th to 20th	Night	17% 8% 39% 29% 7%	800
	21st to end	Night	19% 10% 37% 27% 7%	880
November	1st to 10th	Night	10% 11% 35% 36% 8%	878
	11th to 20th	Night	13% 13% 40% 28% 6%	1050
	21st to end	Night	19% 10% 35% 28% 8%	1050
December	1st to 10th	Night	15% 12% 39% 28% 5% 1	1050
	11th to 20th	Night	19% 9% 38% 28% 6%	1050
	21st to end	Night	20% 13% 37% 26% 4	1155

Page generated at 2026-07-28 02:25:21. Version ac07

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