Calf Mountain Overlook
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Calf Mountain Overlook clear sky chart from 2005-11-06 to 2026-07-01.

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	13% 6% 2 6% 4 4 5% 4 6% 8% 42%	137410
	Night	13% 6% 2 6% 4 4 4 4 5% 7% 46%	134902
Transparency	Day	38% 7% 12% 22% 16% 5%	141016
	Night	37% 6% 11% 23% 19% 5%	139366
Seeing	Day	19% 13% 25% 23% 14% 5%	17153
	Night	16% 10% 26% 32% 14% 2	26967

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	12% 7% 2 5% 4 4 4 3 4 6% 49%	5258
	11th to 20th	Day	8% 7% 3 6% 4 4 4 3 3 4 54%	5280
	21st to end	Day	12% 7% 3 7% 4 4 4 3 4 5% 48%	5780
February	1st to 10th	Day	11% 7% 3 8% 5% 4 5% 4 5% 6% 43%	1890
	11th to 20th	Day	16% 8% 2 6% 4 4 3 4 7% 5% 41%	1843
	21st to end	Day	15% 9% 3 6% 5% 4 4 4 5% 6% 40%	1806
March	1st to 10th	Day	15% 7% 2 5% 4 4 4 4 5% 7% 41%	5045
	11th to 20th	Day	11% 5% 2 5% 3 4 4 3 5% 6% 51%	5090
	21st to end	Day	13% 7% 2 6% 5% 5% 5% 4 5% 6% 41%	5586
April	1st to 10th	Day	10% 7% 2 5% 5% 4 4 3 6% 8% 47%	2465
	11th to 20th	Day	11% 6% 2 5% 4 4 5% 4 6% 7% 47%	2494
	21st to end	Day	15% 8% 2 6% 5% 4 5% 4 4 6% 42%	2578
May	1st to 10th	Day	13% 5% 2 7% 5% 5% 6% 5% 7% 9% 36%	7616
	11th to 20th	Day	19% 5% 2 5% 4 4 5% 4 6% 8% 38%	7626
	21st to end	Day	20% 5% 2 5% 4 4 4 4 6% 9% 38%	8706
June	1st to 10th	Day	10% 4 2 6% 5% 4 5% 5% 7% 9% 43%	2940
	11th to 20th	Day	10% 5% 2 6% 6% 5% 6% 5% 7% 10% 38%	2940
	21st to end	Day	8% 4 2 5% 4 5% 5% 5% 8% 10% 43%	2940
July	1st to 10th	Day	7% 4 2 6% 6% 5% 6% 5% 8% 10% 41%	5955
	11th to 20th	Day	8% 5% 3 7% 6% 7% 8% 6% 10% 12% 29%	5900
	21st to end	Day	9% 5% 2 7% 5% 7% 6% 5% 8% 11% 35%	6424
August	1st to 10th	Day	14% 5% 2 6% 5% 5% 6% 5% 7% 11% 33%	4234
	11th to 20th	Day	9% 4 2 6% 5% 6% 6% 5% 9% 10% 38%	4118
	21st to end	Day	9% 4 2 5% 4 4 4 4 6% 9% 48%	4312
September	1st to 10th	Day	12% 5% 2 6% 4 4 4 5% 4 5% 49%	2400
	11th to 20th	Day	13% 5% 2 6% 4 4 5% 4 5% 8% 45%	2290
	21st to end	Day	25% 6% 2 5% 5% 4 4 3 6% 6% 35%	2145
October	1st to 10th	Day	15% 5% 2 5% 4 4 4 3 5% 6% 49%	2000
	11th to 20th	Day	15% 4 2 4 3 2 4 3 5% 7% 52%	2000
	21st to end	Day	14% 6% 2 5% 3 3 3 2 4 6% 52%	2200
November	1st to 10th	Day	11% 5% 2 4 3 4 3 3 5% 5% 56%	2057
	11th to 20th	Day	13% 5% 1 4 4 4 2 4 5% 5% 52%	1873
	21st to end	Day	13% 5% 1 5% 3 4 3 3 6% 7% 50%	1680
December	1st to 10th	Day	10% 5% 2 5% 3 3 4 3 6% 6% 52%	2680
	11th to 20th	Day	16% 5% 2 5% 3 3 3 3 5% 7% 48%	3070
	21st to end	Day	19% 7% 3 6% 4 4 4 3 5% 7% 38%	4189
January	1st to 10th	Night	9% 6% 2 5% 4 4 4 4 5% 6% 52%	7635
	11th to 20th	Night	10% 7% 2 5% 3 3 3 2 4 5% 57%	7680
	21st to end	Night	12% 7% 2 5% 4 4 3 3 3 5% 53%	8401
February	1st to 10th	Night	11% 8% 2 6% 4 4 4 4 6% 7% 44%	2730
	11th to 20th	Night	18% 8% 2 6% 3 3 4 3 4 5% 43%	2663
	21st to end	Night	12% 8% 2 7% 4 4 4 4 5% 6% 44%	1996
March	1st to 10th	Night	16% 5% 2 5% 4 3 4 3 5% 6% 47%	5028
	11th to 20th	Night	10% 4 1 5% 3 3 3 4 6% 7% 54%	5090
	21st to end	Night	12% 6% 2 6% 4 4 5% 4 5% 6% 46%	5588
April	1st to 10th	Night	12% 6% 2 6% 4 4 4 4 6% 9% 44%	2154
	11th to 20th	Night	11% 5% 2 5% 4 4 4 3 5% 9% 48%	2075
	21st to end	Night	15% 5% 2 5% 4 4 5% 4 5% 7% 45%	2059
May	1st to 10th	Night	15% 7% 2 7% 5% 4 4 4 6% 8% 39%	5237
	11th to 20th	Night	18% 5% 2 5% 4 4 5% 4 6% 8% 40%	5234
	21st to end	Night	21% 6% 2 6% 4 3 4 3 5% 9% 36%	5430
June	1st to 10th	Night	9% 5% 2 6% 4 4 5% 5% 7% 9% 44%	1680
	11th to 20th	Night	10% 5% 2 6% 4 4 5% 5% 7% 9% 43%	1680
	21st to end	Night	9% 4 2 5% 4 4 5% 3 6% 10% 46%	1680
July	1st to 10th	Night	8% 5% 2 6% 4 5% 6% 5% 7% 10% 42%	3983
	11th to 20th	Night	10% 8% 3 9% 6% 6% 7% 5% 9% 9% 28%	4057
	21st to end	Night	7% 6% 2 8% 6% 6% 7% 6% 8% 10% 34%	4427
August	1st to 10th	Night	16% 5% 2 7% 5% 6% 5% 4 7% 8% 36%	2915
	11th to 20th	Night	10% 6% 3 8% 5% 6% 6% 5% 6% 9% 37%	2898
	21st to end	Night	12% 6% 2 5% 4 4 5% 3 6% 8% 45%	3586
September	1st to 10th	Night	13% 5% 2 5% 4 4 4 4 4 6% 49%	2000
	11th to 20th	Night	14% 5% 2 6% 3 4 3 3 5% 7% 47%	2105
	21st to end	Night	25% 6% 2 6% 3 3 3 3 4 5% 39%	2254
October	1st to 10th	Night	17% 6% 2 5% 3 3 3 2 5% 6% 47%	2400
	11th to 20th	Night	14% 4 2 5% 3 4 4 4 4 6% 51%	2400
	21st to end	Night	13% 3 1 5% 3 4 3 3 5% 6% 54%	2640
November	1st to 10th	Night	11% 7% 3 5% 4 3 3 2 4 4 54%	2461
	11th to 20th	Night	13% 6% 2 5% 4 3 4 3 3 6% 50%	2740
	21st to end	Night	12% 6% 1 5% 4 4 4 3 5% 5% 50%	2940
December	1st to 10th	Night	9% 5% 2 5% 4 3 4 4 5% 7% 53%	4720
	11th to 20th	Night	15% 7% 2 6% 4 4 4 3 4 6% 45%	5345
	21st to end	Night	14% 5% 2 5% 4 4 5% 4 6% 8% 43%	6991

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	37% 4 9% 22% 21% 8%	5259
	11th to 20th	Day	35% 3 5% 17% 24% 16%	5280
	21st to end	Day	40% 3 5% 27% 19% 5%	5780
February	1st to 10th	Day	42% 6% 10% 23% 16% 4	1890
	11th to 20th	Day	42% 6% 9% 20% 18% 5%	1852
	21st to end	Day	45% 5% 9% 18% 17% 6%	1806
March	1st to 10th	Day	41% 5% 9% 18% 17% 10%	5045
	11th to 20th	Day	32% 5% 8% 26% 20% 8%	5090
	21st to end	Day	43% 7% 10% 17% 17% 7%	5586
April	1st to 10th	Day	34% 7% 11% 21% 18% 7%	2465
	11th to 20th	Day	34% 6% 12% 22% 20% 5%	2494
	21st to end	Day	42% 6% 11% 24% 13% 4	2578
May	1st to 10th	Day	42% 9% 12% 22% 14% 1	7651
	11th to 20th	Day	42% 8% 13% 24% 13% 1	7630
	21st to end	Day	42% 8% 12% 18% 17% 3	8721
June	1st to 10th	Day	34% 10% 15% 24% 17% 1	2940
	11th to 20th	Day	38% 11% 15% 21% 14% 1	2940
	21st to end	Day	32% 11% 16% 25% 14% 1	2940
July	1st to 10th	Day	34% 12% 19% 20% 12% 4	5890
	11th to 20th	Day	41% 13% 20% 20% 6% 1	5831
	21st to end	Day	39% 10% 15% 23% 13%	6240
August	1st to 10th	Day	42% 9% 18% 25% 6%	4221
	11th to 20th	Day	36% 10% 15% 27% 11% 1	4157
	21st to end	Day	31% 7% 20% 28% 12% 1	4312
September	1st to 10th	Day	36% 8% 14% 18% 20% 4	2400
	11th to 20th	Day	38% 7% 8% 26% 19% 3	2290
	21st to end	Day	48% 6% 11% 17% 16% 2	2145
October	1st to 10th	Day	34% 4 8% 19% 30% 6%	3260
	11th to 20th	Day	24% 3 9% 24% 27% 13%	3240
	21st to end	Day	21% 3 10% 30% 23% 13%	3538
November	1st to 10th	Day	31% 4 10% 24% 26% 5%	2057
	11th to 20th	Day	34% 5% 9% 22% 23% 7%	1873
	21st to end	Day	34% 5% 10% 25% 23% 3	1680
December	1st to 10th	Day	31% 6% 11% 25% 19% 8%	2680
	11th to 20th	Day	37% 4 14% 23% 17% 5%	3066
	21st to end	Day	44% 6% 13% 22% 15% 1	4189
January	1st to 10th	Night	33% 4 9% 23% 23% 8%	7636
	11th to 20th	Night	31% 3 6% 20% 27% 13%	7680
	21st to end	Night	36% 3 5% 27% 23% 6%	8401
February	1st to 10th	Night	38% 7% 11% 24% 17% 3	2730
	11th to 20th	Night	43% 5% 8% 19% 18% 6%	2665
	21st to end	Night	39% 5% 11% 21% 17% 7%	1996
March	1st to 10th	Night	37% 5% 8% 21% 20% 9%	5028
	11th to 20th	Night	28% 5% 8% 23% 28% 7%	5090
	21st to end	Night	38% 5% 10% 20% 21% 5%	5588
April	1st to 10th	Night	37% 7% 13% 18% 20% 6%	2154
	11th to 20th	Night	33% 5% 15% 21% 21% 5%	2075
	21st to end	Night	37% 7% 11% 27% 15% 4	2059
May	1st to 10th	Night	43% 8% 13% 21% 12% 3	5264
	11th to 20th	Night	41% 6% 13% 27% 12% 1	5235
	21st to end	Night	46% 7% 13% 20% 10% 3	5437
June	1st to 10th	Night	33% 11% 12% 28% 15% 1	1680
	11th to 20th	Night	35% 10% 16% 25% 13% 1	1680
	21st to end	Night	32% 10% 17% 21% 17% 3	1680
July	1st to 10th	Night	34% 12% 19% 19% 14% 2	3940
	11th to 20th	Night	47% 12% 17% 17% 6% 1	4006
	21st to end	Night	41% 11% 16% 21% 11%	4297
August	1st to 10th	Night	44% 9% 16% 25% 6% 1	2904
	11th to 20th	Night	41% 9% 15% 23% 11%	2925
	21st to end	Night	35% 9% 16% 31% 9% 2	3586
September	1st to 10th	Night	35% 8% 13% 21% 17% 6%	2000
	11th to 20th	Night	37% 8% 10% 25% 19% 3	2105
	21st to end	Night	47% 5% 10% 19% 16% 3	2254
October	1st to 10th	Night	41% 3 9% 19% 22% 6%	3920
	11th to 20th	Night	25% 4 8% 23% 29% 11%	3899
	21st to end	Night	20% 3 9% 31% 27% 11%	4252
November	1st to 10th	Night	34% 3 9% 21% 26% 6%	2461
	11th to 20th	Night	36% 5% 7% 22% 24% 7%	2740
	21st to end	Night	34% 5% 9% 24% 22% 5%	2940
December	1st to 10th	Night	31% 5% 11% 27% 23% 4	4720
	11th to 20th	Night	41% 4 12% 19% 17% 7%	5348
	21st to end	Night	38% 7% 13% 24% 17% 2	6991

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% 28% 26% 13% 3	330
	11th to 20th	Day	32% 31% 23% 12% 1	330
	21st to end	Day	26% 27% 33% 12% 2 1	363
February	1st to 10th	Day	25% 29% 31% 13% 2	330
	11th to 20th	Day	42% 25% 25% 8%	330
	21st to end	Day	31% 21% 28% 18% 2	420
March	1st to 10th	Day	23% 23% 28% 22% 4 1	540
	11th to 20th	Day	26% 22% 29% 16% 5% 1	540
	21st to end	Day	24% 19% 31% 21% 5% 1	594
April	1st to 10th	Day	23% 24% 26% 18% 8% 1	540
	11th to 20th	Day	20% 16% 29% 20% 11% 3	532
	21st to end	Day	22% 17% 29% 20% 10% 2	540
May	1st to 10th	Day	20% 20% 31% 19% 7% 3	543
	11th to 20th	Day	21% 11% 29% 22% 14% 3	567
	21st to end	Day	20% 9% 24% 25% 16% 6%	617
June	1st to 10th	Day	11% 8% 30% 25% 20% 6%	570
	11th to 20th	Day	11% 10% 27% 28% 17% 7%	570
	21st to end	Day	10% 6% 25% 32% 20% 6%	570
July	1st to 10th	Day	9% 4 19% 31% 26% 10%	525
	11th to 20th	Day	5% 3 20% 34% 26% 13%	524
	21st to end	Day	10% 3 17% 37% 23% 10%	576
August	1st to 10th	Day	14% 4 20% 26% 24% 11%	526
	11th to 20th	Day	11% 4 20% 28% 25% 12%	519
	21st to end	Day	11% 3 17% 32% 22% 16%	583
September	1st to 10th	Day	13% 5% 18% 28% 22% 14%	530
	11th to 20th	Day	16% 4 15% 29% 27% 10%	530
	21st to end	Day	31% 8% 18% 23% 15% 4	530
October	1st to 10th	Day	18% 6% 22% 31% 18% 6%	530
	11th to 20th	Day	17% 15% 26% 23% 17% 3	530
	21st to end	Day	19% 14% 30% 23% 11% 3	583
November	1st to 10th	Day	17% 11% 30% 27% 11% 3	535
	11th to 20th	Day	22% 14% 31% 22% 10% 1	371
	21st to end	Day	23% 20% 30% 19% 7% 1	220
December	1st to 10th	Day	21% 22% 37% 14% 5% 1	220
	11th to 20th	Day	24% 19% 28% 21% 7% 1	220
	21st to end	Day	28% 20% 29% 17% 5% 1	275
January	1st to 10th	Night	18% 18% 39% 23% 3	840
	11th to 20th	Night	20% 17% 32% 28% 3	840
	21st to end	Night	16% 16% 40% 25% 2	924
February	1st to 10th	Night	16% 17% 37% 29% 2	840
	11th to 20th	Night	23% 20% 34% 21% 1	823
	21st to end	Night	19% 18% 37% 23% 2	692
March	1st to 10th	Night	15% 19% 35% 28% 4	840
	11th to 20th	Night	23% 16% 30% 25% 5% 1	840
	21st to end	Night	18% 15% 35% 26% 5%	924
April	1st to 10th	Night	16% 19% 36% 23% 6%	840
	11th to 20th	Night	14% 15% 31% 31% 10% 1	831
	21st to end	Night	18% 9% 30% 36% 8%	799
May	1st to 10th	Night	18% 10% 28% 29% 15% 1	630
	11th to 20th	Night	18% 6% 24% 35% 15% 1	621
	21st to end	Night	20% 2 17% 36% 24% 2	570
June	1st to 10th	Night	8% 3 19% 48% 22% 1	420
	11th to 20th	Night	10% 3 18% 41% 27% 1	420
	21st to end	Night	10% 2 19% 45% 23% 2	420
July	1st to 10th	Night	11% 1 12% 34% 36% 6%	549
	11th to 20th	Night	6% 2 8% 36% 42% 6%	582
	21st to end	Night	8% 3 12% 40% 32% 5%	657
August	1st to 10th	Night	13% 3 9% 39% 32% 4	597
	11th to 20th	Night	14% 2 10% 35% 36% 4	604
	21st to end	Night	13% 2 12% 36% 33% 4	880
September	1st to 10th	Night	15% 2 13% 36% 28% 6%	800
	11th to 20th	Night	14% 3 12% 37% 31% 4	800
	21st to end	Night	28% 4 16% 30% 20% 2	800
October	1st to 10th	Night	21% 5% 16% 31% 24% 4	800
	11th to 20th	Night	16% 9% 26% 32% 16% 1	800
	21st to end	Night	16% 9% 28% 34% 13% 1	880
November	1st to 10th	Night	14% 9% 28% 36% 11% 2	820
	11th to 20th	Night	17% 12% 29% 33% 9% 1	840
	21st to end	Night	16% 12% 32% 30% 9% 1	840
December	1st to 10th	Night	18% 12% 37% 28% 6%	840
	11th to 20th	Night	16% 10% 34% 34% 5%	840
	21st to end	Night	17% 12% 32% 35% 3	924

Page generated at 2026-06-28 02:10:49. Version ac07

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