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 2025-03-27.

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 4 5% 7% 43%	109153
	Night	11% 7% 3 7% 4 4 4 3 5% 6% 46%	110378
Transparency	Day	39% 5% 13% 25% 16% 2	112802
	Night	38% 5% 12% 25% 18% 3	114870
Seeing	Day	14% 10% 30% 28% 15% 3	16190
	Night	14% 9% 33% 32% 11% 1	26242

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 12% 8% 5% 5% 3 5% 7% 31%	4048
	11th to 20th	Day	7% 10% 4 9% 5% 5% 7% 3 4 6% 40%	4080
	21st to end	Day	9% 12% 5% 14% 6% 6% 4 3 4 5% 32%	4488
February	1st to 10th	Day	11% 12% 4 8% 6% 5% 5% 4 5% 7% 32%	1800
	11th to 20th	Day	11% 9% 5% 7% 4 5% 4 4 6% 7% 38%	1754
	21st to end	Day	11% 10% 3 6% 5% 4 3 3 5% 7% 44%	1657
March	1st to 10th	Day	15% 10% 3 6% 4 3 3 3 3 5% 46%	3546
	11th to 20th	Day	11% 8% 3 6% 4 3 4 3 5% 7% 48%	3590
	21st to end	Day	18% 13% 6% 8% 4 4 4 4 5% 7% 27%	3880
April	1st to 10th	Day	15% 8% 3 6% 5% 3 3 3 4 6% 44%	2203
	11th to 20th	Day	15% 9% 3 7% 5% 3 4 4 6% 6% 39%	2254
	21st to end	Day	21% 7% 2 6% 4 3 4 4 5% 7% 37%	2460
May	1st to 10th	Day	15% 8% 3 7% 5% 4 5% 4 6% 8% 36%	4082
	11th to 20th	Day	16% 7% 3 6% 5% 4 4 4 5% 6% 40%	4082
	21st to end	Day	13% 7% 2 6% 4 4 4 3 5% 8% 44%	4762
June	1st to 10th	Day	7% 5% 1 6% 5% 4 5% 5% 6% 9% 48%	2660
	11th to 20th	Day	8% 5% 2 5% 4 4 4 4 7% 9% 47%	2660
	21st to end	Day	8% 6% 1 5% 5% 5% 5% 5% 6% 9% 46%	2660
July	1st to 10th	Day	12% 5% 3 6% 4 4 5% 4 7% 9% 40%	4328
	11th to 20th	Day	7% 4 1 4 3 4 4 4 6% 8% 54%	4120
	21st to end	Day	4 3 1 4 4 3 4 4 7% 11% 54%	4465
August	1st to 10th	Day	6% 4 2 5% 4 4 5% 3 7% 10% 49%	4104
	11th to 20th	Day	11% 6% 2 6% 4 4 5% 4 6% 8% 43%	4041
	21st to end	Day	6% 5% 2 7% 4 5% 5% 4 6% 7% 50%	4318
September	1st to 10th	Day	11% 4 2 4 4 3 3 3 6% 6% 54%	2280
	11th to 20th	Day	9% 4 2 6% 4 4 4 3 5% 8% 51%	2115
	21st to end	Day	11% 4 1 5% 3 3 4 3 5% 6% 56%	2076
October	1st to 10th	Day	13% 6% 2 5% 4 3 3 3 4 6% 51%	1900
	11th to 20th	Day	12% 8% 2 4 3 3 2 3 3 5% 56%	1900
	21st to end	Day	13% 8% 3 6% 4 3 4 3 6% 5% 47%	2090
November	1st to 10th	Day	10% 7% 2 5% 3 4 3 2 5% 8% 52%	1900
	11th to 20th	Day	12% 8% 2 6% 4 4 4 2 4 6% 48%	1650
	21st to end	Day	14% 9% 4 7% 3 3 3 4 6% 6% 41%	1600
December	1st to 10th	Day	5% 5% 2 7% 5% 4 4 3 4 6% 55%	2610
	11th to 20th	Day	10% 10% 3 9% 5% 4 4 3 5% 5% 42%	3008
	21st to end	Day	19% 12% 6% 13% 5% 4 4 3 4 5% 23%	3982
January	1st to 10th	Night	9% 9% 5% 19% 7% 6% 5% 3 5% 5% 26%	5915
	11th to 20th	Night	7% 8% 4 10% 5% 5% 6% 4 6% 5% 39%	5900
	21st to end	Night	12% 12% 4 11% 5% 4 4 2 4 4 38%	6490
February	1st to 10th	Night	12% 11% 3 9% 5% 4 4 3 6% 6% 38%	2600
	11th to 20th	Night	11% 9% 3 7% 5% 4 4 4 5% 6% 42%	2533
	21st to end	Night	10% 8% 3 7% 4 4 3 3 5% 5% 48%	1990
March	1st to 10th	Night	12% 7% 2 6% 4 3 4 3 4 5% 50%	3529
	11th to 20th	Night	12% 5% 2 5% 3 3 3 2 4 5% 55%	3590
	21st to end	Night	19% 9% 3 10% 4 4 4 3 5% 6% 32%	3889
April	1st to 10th	Night	10% 8% 2 6% 3 4 4 3 6% 7% 48%	1976
	11th to 20th	Night	13% 8% 2 7% 4 4 3 4 5% 6% 46%	1875
	21st to end	Night	16% 9% 3 5% 4 3 4 3 5% 5% 44%	1716
May	1st to 10th	Night	15% 7% 2 6% 4 4 4 3 5% 7% 43%	2823
	11th to 20th	Night	13% 7% 2 6% 4 4 3 2 4 6% 49%	2823
	21st to end	Night	13% 6% 2 6% 4 4 3 3 5% 7% 48%	2789
June	1st to 10th	Night	6% 3 2 4 4 3 4 5% 6% 8% 55%	1520
	11th to 20th	Night	6% 3 1 4 3 3 5% 4 8% 11% 51%	1520
	21st to end	Night	5% 4 1 3 3 4 4 3 7% 10% 57%	1520
July	1st to 10th	Night	10% 5% 2 6% 4 4 4 4 6% 8% 47%	2623
	11th to 20th	Night	4 3 1 4 3 3 3 3 6% 8% 63%	2850
	21st to end	Night	5% 3 2 4 4 4 4 4 8% 10% 53%	3098
August	1st to 10th	Night	3 2 1 4 3 3 4 3 6% 10% 61%	2836
	11th to 20th	Night	13% 6% 2 5% 3 3 3 2 4 6% 53%	2798
	21st to end	Night	6% 3 2 5% 3 3 3 3 5% 8% 58%	3342
September	1st to 10th	Night	10% 3 1 3 4 3 3 3 5% 7% 57%	1900
	11th to 20th	Night	10% 3 2 4 4 4 3 3 4 7% 56%	2061
	21st to end	Night	9% 4 1 5% 3 2 3 3 4 6% 59%	2090
October	1st to 10th	Night	13% 6% 1 4 3 3 3 3 5% 6% 54%	2275
	11th to 20th	Night	13% 7% 2 4 2 3 3 2 3 5% 56%	2280
	21st to end	Night	15% 6% 2 5% 3 3 3 2 4 5% 51%	2508
November	1st to 10th	Night	9% 4 2 4 3 3 4 3 5% 7% 57%	2395
	11th to 20th	Night	10% 6% 2 5% 5% 3 3 3 5% 7% 50%	2749
	21st to end	Night	13% 8% 3 5% 3 3 3 3 5% 5% 49%	2800
December	1st to 10th	Night	6% 7% 2 5% 4 4 4 3 5% 6% 53%	4580
	11th to 20th	Night	11% 7% 3 8% 4 3 4 3 5% 7% 44%	5199
	21st to end	Night	19% 15% 6% 11% 4 3 3 3 4 4 28%	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	53% 5% 10% 20% 11% 1	4049
	11th to 20th	Day	47% 3 10% 19% 17% 4	4080
	21st to end	Day	55% 4 11% 19% 10% 1	4488
February	1st to 10th	Day	51% 6% 12% 20% 10% 2	1800
	11th to 20th	Day	45% 6% 12% 21% 13% 2	1763
	21st to end	Day	41% 4 12% 24% 16% 2	1657
March	1st to 10th	Day	42% 5% 10% 21% 20% 2	3546
	11th to 20th	Day	37% 5% 11% 27% 19% 2	3590
	21st to end	Day	55% 8% 17% 14% 4 1	3880
April	1st to 10th	Day	42% 5% 11% 26% 14% 2	2203
	11th to 20th	Day	44% 5% 12% 22% 14% 2	2254
	21st to end	Day	47% 7% 10% 25% 11% 1	2460
May	1st to 10th	Day	43% 8% 13% 22% 13% 2	4120
	11th to 20th	Day	44% 7% 11% 25% 14%	4086
	21st to end	Day	37% 7% 12% 26% 16% 2	4775
June	1st to 10th	Day	31% 9% 15% 28% 14% 3	2660
	11th to 20th	Day	33% 7% 14% 28% 17% 2	2660
	21st to end	Day	32% 8% 15% 27% 14% 3	2660
July	1st to 10th	Day	39% 4 16% 27% 12% 2	4262
	11th to 20th	Day	28% 5% 11% 34% 20% 2	4051
	21st to end	Day	23% 5% 19% 34% 15% 3	4325
August	1st to 10th	Day	29% 5% 15% 31% 18% 1	4090
	11th to 20th	Day	38% 5% 16% 26% 16%	4080
	21st to end	Day	33% 4 16% 29% 14% 4	4317
September	1st to 10th	Day	30% 6% 11% 29% 20% 5%	2280
	11th to 20th	Day	32% 6% 12% 28% 21% 2	2115
	21st to end	Day	29% 5% 9% 31% 24% 2	2076
October	1st to 10th	Day	22% 2 6% 20% 47% 2	3160
	11th to 20th	Day	21% 2 7% 29% 32% 8%	3140
	21st to end	Day	34% 3 10% 28% 22% 3	3428
November	1st to 10th	Day	32% 4 15% 26% 19% 3	1900
	11th to 20th	Day	38% 3 12% 27% 18% 2	1650
	21st to end	Day	42% 5% 13% 26% 15% 1	1600
December	1st to 10th	Day	32% 4 18% 31% 15% 1	2610
	11th to 20th	Day	44% 3 16% 26% 10% 1	3005
	21st to end	Day	64% 3 12% 14% 6%	3982
January	1st to 10th	Night	58% 5% 10% 17% 9% 1	5915
	11th to 20th	Night	46% 3 11% 21% 16% 3	5900
	21st to end	Night	51% 3 11% 16% 15% 3	6490
February	1st to 10th	Night	47% 5% 12% 20% 14% 3	2600
	11th to 20th	Night	42% 5% 11% 23% 16% 2	2534
	21st to end	Night	38% 4 11% 21% 20% 5%	1990
March	1st to 10th	Night	36% 5% 10% 25% 22% 2	3529
	11th to 20th	Night	32% 5% 8% 31% 19% 5%	3590
	21st to end	Night	52% 7% 18% 18% 5% 1	3889
April	1st to 10th	Night	34% 7% 11% 27% 18% 3	1976
	11th to 20th	Night	39% 7% 9% 27% 15% 3	1875
	21st to end	Night	42% 6% 10% 25% 16% 2	1716
May	1st to 10th	Night	39% 8% 11% 21% 19% 2	2850
	11th to 20th	Night	37% 6% 10% 25% 20% 1	2824
	21st to end	Night	36% 7% 13% 24% 19% 3	2797
June	1st to 10th	Night	23% 9% 18% 30% 16% 4	1520
	11th to 20th	Night	24% 8% 16% 29% 20% 4	1520
	21st to end	Night	22% 7% 18% 30% 18% 4	1520
July	1st to 10th	Night	36% 4 13% 25% 18% 4	2581
	11th to 20th	Night	21% 4 15% 35% 22% 2	2796
	21st to end	Night	25% 5% 19% 31% 19% 1	2999
August	1st to 10th	Night	20% 5% 16% 33% 24% 2	2826
	11th to 20th	Night	34% 3 13% 28% 20% 1	2825
	21st to end	Night	26% 4 17% 30% 18% 6%	3342
September	1st to 10th	Night	27% 6% 10% 26% 24% 7%	1900
	11th to 20th	Night	28% 5% 10% 32% 22% 3	2061
	21st to end	Night	27% 5% 8% 31% 26% 3	2090
October	1st to 10th	Night	20% 2 6% 19% 49% 3	3795
	11th to 20th	Night	22% 2 6% 29% 31% 9%	3779
	21st to end	Night	36% 3 7% 28% 24% 2	4120
November	1st to 10th	Night	27% 5% 15% 25% 23% 5%	2395
	11th to 20th	Night	34% 4 10% 30% 19% 3	2749
	21st to end	Night	38% 4 11% 28% 18% 2	2800
December	1st to 10th	Night	32% 3 12% 37% 14% 1	4580
	11th to 20th	Night	41% 3 14% 28% 13% 1	5201
	21st to end	Night	61% 3 10% 19% 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	21% 12% 36% 24% 7%	300
	11th to 20th	Day	20% 18% 37% 21% 5%	300
	21st to end	Day	16% 9% 45% 26% 4	330
February	1st to 10th	Day	17% 17% 43% 20% 2 1	300
	11th to 20th	Day	15% 20% 41% 19% 6%	300
	21st to end	Day	14% 19% 44% 20% 3	249
March	1st to 10th	Day	19% 15% 41% 22% 2 1	300
	11th to 20th	Day	27% 11% 34% 24% 3 1	300
	21st to end	Day	33% 22% 29% 13% 4	315
April	1st to 10th	Day	25% 13% 37% 19% 5% 1	383
	11th to 20th	Day	19% 16% 35% 23% 7%	452
	21st to end	Day	23% 17% 33% 18% 7% 1	640
May	1st to 10th	Day	18% 14% 33% 26% 8% 1	653
	11th to 20th	Day	18% 11% 31% 26% 12% 2	675
	21st to end	Day	18% 9% 27% 27% 16% 2	734
June	1st to 10th	Day	7% 4 23% 34% 24% 7%	680
	11th to 20th	Day	8% 5% 28% 36% 19% 4	680
	21st to end	Day	8% 6% 36% 32% 14% 3	680
July	1st to 10th	Day	9% 3 17% 32% 28% 11%	671
	11th to 20th	Day	7% 3 21% 37% 25% 7%	668
	21st to end	Day	6% 2 15% 42% 29% 6%	739
August	1st to 10th	Day	8% 2 19% 41% 25% 6%	676
	11th to 20th	Day	10% 3 20% 36% 26% 5%	665
	21st to end	Day	8% 3 19% 33% 29% 8%	625
September	1st to 10th	Day	13% 4 22% 30% 26% 6%	490
	11th to 20th	Day	8% 3 21% 39% 21% 8%	325
	21st to end	Day	14% 6% 29% 30% 18% 3	300
October	1st to 10th	Day	17% 8% 27% 28% 13% 7%	300
	11th to 20th	Day	11% 20% 39% 21% 7% 1	300
	21st to end	Day	16% 18% 34% 24% 6% 2	330
November	1st to 10th	Day	15% 12% 40% 24% 7% 2	300
	11th to 20th	Day	20% 15% 37% 20% 7% 1	300
	21st to end	Day	22% 12% 35% 22% 8%	300
December	1st to 10th	Day	7% 17% 40% 28% 6% 2	300
	11th to 20th	Day	18% 16% 34% 24% 6% 1	300
	21st to end	Day	23% 17% 38% 19% 2	330
January	1st to 10th	Night	11% 13% 40% 29% 6%	1000
	11th to 20th	Night	15% 14% 39% 26% 6%	1000
	21st to end	Night	14% 12% 42% 28% 4	1100
February	1st to 10th	Night	17% 11% 42% 26% 4	1000
	11th to 20th	Night	16% 13% 41% 26% 5%	979
	21st to end	Night	15% 15% 43% 21% 6% 1	670
March	1st to 10th	Night	15% 14% 40% 26% 5%	600
	11th to 20th	Night	20% 9% 37% 28% 6%	600
	21st to end	Night	26% 13% 38% 19% 5%	647
April	1st to 10th	Night	15% 14% 40% 26% 5%	570
	11th to 20th	Night	16% 13% 39% 25% 6%	563
	21st to end	Night	20% 11% 35% 28% 5% 1	570
May	1st to 10th	Night	15% 11% 36% 33% 6% 1	570
	11th to 20th	Night	16% 9% 32% 30% 11% 1	561
	21st to end	Night	13% 8% 29% 35% 13% 1	617
June	1st to 10th	Night	5% 4 25% 44% 21% 1	570
	11th to 20th	Night	9% 3 26% 44% 17%	570
	21st to end	Night	5% 3 33% 43% 15% 1	570
July	1st to 10th	Night	7% 2 16% 43% 30% 3	555
	11th to 20th	Night	5% 1 16% 48% 28% 2	552
	21st to end	Night	5% 2 16% 47% 28% 2	624
August	1st to 10th	Night	4 1 21% 47% 25% 1	567
	11th to 20th	Night	9% 2 14% 47% 25% 2	564
	21st to end	Night	9% 2 16% 42% 29% 3	627
September	1st to 10th	Night	11% 2 21% 40% 24% 2	570
	11th to 20th	Night	12% 3 20% 40% 24% 1	570
	21st to end	Night	10% 4 29% 41% 16% 1	570
October	1st to 10th	Night	15% 7% 28% 33% 15% 2	755
	11th to 20th	Night	17% 8% 39% 29% 8%	760
	21st to end	Night	18% 10% 36% 28% 7%	836
November	1st to 10th	Night	10% 11% 34% 37% 9%	835
	11th to 20th	Night	14% 14% 39% 28% 6%	1000
	21st to end	Night	18% 10% 36% 28% 8%	1000
December	1st to 10th	Night	15% 12% 39% 29% 6% 1	1000
	11th to 20th	Night	19% 9% 37% 29% 6%	1000
	21st to end	Night	20% 14% 37% 25% 4	1100

Page generated at 2025-03-24 08:04:29. Version ac07

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