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 2025-02-25.

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% 43%	108587
	Night	13% 6% 2 6% 4 4 4 3 5% 7% 46%	110078
Transparency	Day	37% 7% 12% 22% 16% 4	112237
	Night	36% 6% 11% 23% 19% 5%	114567
Seeing	Day	19% 13% 25% 24% 14% 5%	15331
	Night	16% 10% 26% 32% 15% 2	25255

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% 6% 1 4 4 4 4 3 4 6% 51%	4056
	11th to 20th	Day	9% 8% 3 6% 4 4 4 3 3 4 51%	4060
	21st to end	Day	13% 8% 3 7% 3 3 3 2 4 6% 47%	4466
February	1st to 10th	Day	11% 7% 3 8% 5% 4 5% 4 5% 5% 42%	1800
	11th to 20th	Day	16% 8% 2 6% 4 4 3 4 7% 6% 41%	1753
	21st to end	Day	15% 9% 3 6% 5% 4 4 4 5% 6% 40%	1678
March	1st to 10th	Day	18% 9% 3 6% 5% 4 4 4 4 6% 37%	3435
	11th to 20th	Day	9% 5% 2 5% 4 4 4 3 5% 6% 51%	3480
	21st to end	Day	17% 9% 2 6% 5% 4 5% 4 5% 5% 38%	3815
April	1st to 10th	Day	9% 7% 2 5% 5% 4 4 3 6% 8% 47%	2230
	11th to 20th	Day	12% 7% 2 5% 4 4 5% 4 6% 7% 47%	2254
	21st to end	Day	15% 7% 2 6% 5% 4 5% 4 4 6% 42%	2332
May	1st to 10th	Day	16% 6% 3 8% 5% 6% 6% 5% 7% 8% 31%	4082
	11th to 20th	Day	22% 6% 3 6% 4 4 5% 3 6% 8% 33%	4081
	21st to end	Day	10% 5% 2 5% 4 4 4 4 7% 11% 43%	4651
June	1st to 10th	Day	11% 4 2 6% 5% 4 5% 5% 6% 9% 43%	2660
	11th to 20th	Day	10% 5% 2 6% 6% 6% 6% 5% 7% 10% 38%	2660
	21st to end	Day	8% 4 2 5% 4 5% 5% 5% 8% 10% 43%	2660
July	1st to 10th	Day	6% 4 2 5% 5% 5% 6% 5% 8% 11% 42%	4161
	11th to 20th	Day	9% 5% 2 6% 5% 6% 6% 5% 10% 12% 34%	4120
	21st to end	Day	11% 6% 3 8% 6% 7% 7% 5% 8% 10% 29%	4466
August	1st to 10th	Day	14% 5% 2 7% 5% 5% 6% 5% 7% 11% 33%	4104
	11th to 20th	Day	9% 4 2 6% 5% 6% 6% 5% 9% 10% 38%	3990
	21st to end	Day	9% 4 2 5% 4 4 4 4 6% 9% 48%	4180
September	1st to 10th	Day	12% 5% 2 6% 4 4 4 5% 4 5% 48%	2280
	11th to 20th	Day	14% 5% 2 6% 4 4 5% 3 5% 8% 44%	2176
	21st to end	Day	24% 6% 2 5% 5% 4 4 3 5% 6% 36%	2038
October	1st to 10th	Day	16% 5% 2 5% 4 4 4 3 5% 6% 48%	1900
	11th to 20th	Day	15% 4 2 4 3 2 4 3 4 7% 52%	1900
	21st to end	Day	13% 6% 2 5% 3 3 3 2 5% 6% 52%	2090
November	1st to 10th	Day	12% 5% 2 4 3 4 3 3 5% 5% 55%	1957
	11th to 20th	Day	14% 6% 1 4 4 3 2 4 5% 5% 51%	1784
	21st to end	Day	13% 5% 2 5% 3 4 3 3 6% 7% 50%	1600
December	1st to 10th	Day	10% 5% 2 5% 3 3 4 3 6% 7% 52%	2600
	11th to 20th	Day	17% 5% 2 5% 3 3 3 3 5% 7% 48%	2990
	21st to end	Day	19% 7% 3 6% 4 4 4 3 5% 7% 38%	4098
January	1st to 10th	Night	10% 5% 2 5% 3 3 3 3 4 6% 56%	5889
	11th to 20th	Night	11% 7% 2 4 2 3 2 2 4 5% 57%	5900
	21st to end	Night	13% 8% 3 5% 3 3 3 3 3 5% 52%	6490
February	1st to 10th	Night	11% 8% 2 6% 4 4 5% 4 6% 7% 43%	2600
	11th to 20th	Night	18% 8% 2 6% 3 4 4 3 4 5% 43%	2533
	21st to end	Night	13% 8% 2 6% 4 4 4 4 5% 6% 44%	1867
March	1st to 10th	Night	20% 7% 3 6% 5% 4 4 4 4 6% 37%	3418
	11th to 20th	Night	11% 4 1 4 3 3 4 4 6% 7% 52%	3480
	21st to end	Night	14% 7% 2 5% 3 3 3 3 4 6% 49%	3817
April	1st to 10th	Night	12% 7% 2 6% 5% 4 4 4 6% 8% 44%	1949
	11th to 20th	Night	12% 5% 2 4 4 4 4 3 5% 9% 49%	1875
	21st to end	Night	16% 5% 2 5% 4 4 5% 4 5% 7% 44%	1863
May	1st to 10th	Night	19% 8% 3 7% 5% 4 4 3 6% 9% 34%	2813
	11th to 20th	Night	24% 7% 2 5% 4 4 4 3 5% 6% 36%	2812
	21st to end	Night	11% 5% 2 6% 4 4 4 4 6% 11% 44%	2900
June	1st to 10th	Night	9% 5% 2 6% 4 3 5% 5% 8% 9% 44%	1520
	11th to 20th	Night	10% 5% 2 6% 4 4 5% 5% 7% 9% 43%	1520
	21st to end	Night	9% 4 2 5% 4 4 5% 3 6% 10% 46%	1520
July	1st to 10th	Night	6% 4 1 5% 4 4 6% 5% 9% 11% 44%	2793
	11th to 20th	Night	9% 6% 2 7% 5% 5% 6% 5% 8% 10% 37%	2840
	21st to end	Night	9% 8% 3 9% 6% 6% 6% 5% 7% 9% 33%	3087
August	1st to 10th	Night	15% 5% 2 7% 5% 6% 5% 4 7% 8% 36%	2825
	11th to 20th	Night	10% 6% 3 8% 5% 6% 6% 5% 6% 9% 37%	2807
	21st to end	Night	12% 6% 2 5% 4 4 4 3 6% 8% 45%	3476
September	1st to 10th	Night	13% 5% 2 5% 4 4 4 4 5% 6% 48%	1900
	11th to 20th	Night	14% 5% 3 6% 3 4 3 3 5% 7% 46%	2000
	21st to end	Night	25% 6% 2 5% 3 3 3 3 4 5% 40%	2141
October	1st to 10th	Night	18% 6% 2 5% 3 3 3 2 5% 6% 46%	2280
	11th to 20th	Night	14% 4 2 5% 3 4 3 4 4 6% 51%	2280
	21st to end	Night	13% 3 1 5% 3 4 3 3 5% 6% 54%	2508
November	1st to 10th	Night	11% 7% 3 5% 4 3 3 2 4 4 54%	2341
	11th to 20th	Night	13% 6% 2 5% 4 3 4 3 3 6% 50%	2609
	21st to end	Night	12% 6% 1 4 4 4 4 3 5% 6% 51%	2800
December	1st to 10th	Night	9% 5% 2 5% 4 3 4 4 5% 7% 53%	4580
	11th to 20th	Night	16% 7% 2 6% 4 4 4 3 4 6% 44%	5205
	21st to end	Night	15% 5% 2 5% 4 4 5% 4 6% 8% 43%	6840

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	35% 4 6% 22% 22% 10%	4057
	11th to 20th	Day	37% 4 6% 17% 22% 14%	4060
	21st to end	Day	39% 4 6% 26% 20% 5%	4466
February	1st to 10th	Day	42% 6% 10% 23% 15% 3	1800
	11th to 20th	Day	42% 6% 9% 20% 18% 5%	1762
	21st to end	Day	45% 5% 10% 17% 17% 6%	1678
March	1st to 10th	Day	47% 6% 9% 19% 13% 6%	3435
	11th to 20th	Day	31% 6% 9% 26% 20% 7%	3480
	21st to end	Day	47% 7% 9% 18% 15% 4	3815
April	1st to 10th	Day	34% 8% 11% 21% 18% 8%	2230
	11th to 20th	Day	35% 7% 12% 21% 20% 5%	2254
	21st to end	Day	43% 7% 11% 22% 13% 4	2332
May	1st to 10th	Day	47% 10% 13% 18% 10% 2	4120
	11th to 20th	Day	47% 9% 12% 21% 10% 1	4085
	21st to end	Day	32% 11% 16% 21% 18% 2	4665
June	1st to 10th	Day	35% 10% 15% 25% 15% 1	2660
	11th to 20th	Day	38% 11% 15% 21% 14% 1	2660
	21st to end	Day	32% 11% 16% 25% 14% 1	2660
July	1st to 10th	Day	32% 12% 21% 19% 10% 6%	4096
	11th to 20th	Day	36% 10% 20% 24% 9% 1	4051
	21st to end	Day	46% 10% 13% 20% 10% 1	4324
August	1st to 10th	Day	42% 9% 18% 24% 6%	4091
	11th to 20th	Day	36% 10% 15% 28% 11% 1	4029
	21st to end	Day	31% 7% 20% 28% 12% 1	4180
September	1st to 10th	Day	37% 8% 13% 18% 20% 4	2280
	11th to 20th	Day	38% 7% 8% 26% 18% 3	2176
	21st to end	Day	47% 6% 10% 17% 17% 2	2038
October	1st to 10th	Day	34% 4 8% 19% 29% 6%	3160
	11th to 20th	Day	24% 3 9% 24% 27% 13%	3140
	21st to end	Day	21% 3 10% 31% 23% 12%	3428
November	1st to 10th	Day	31% 4 9% 24% 26% 5%	1957
	11th to 20th	Day	34% 5% 10% 20% 23% 8%	1784
	21st to end	Day	33% 5% 11% 24% 24% 3	1600
December	1st to 10th	Day	31% 6% 11% 25% 20% 8%	2600
	11th to 20th	Day	37% 5% 14% 23% 17% 4	2986
	21st to end	Day	44% 6% 13% 21% 15% 1	4098
January	1st to 10th	Night	30% 4 8% 22% 26% 11%	5889
	11th to 20th	Night	31% 4 6% 21% 26% 12%	5900
	21st to end	Night	37% 4 5% 26% 22% 6%	6490
February	1st to 10th	Night	39% 7% 11% 24% 17% 3	2600
	11th to 20th	Night	43% 5% 8% 19% 18% 7%	2535
	21st to end	Night	40% 5% 11% 21% 16% 7%	1867
March	1st to 10th	Night	46% 7% 9% 20% 14% 3	3418
	11th to 20th	Night	29% 6% 8% 23% 28% 6%	3480
	21st to end	Night	38% 5% 10% 22% 20% 4	3817
April	1st to 10th	Night	37% 7% 12% 18% 20% 6%	1949
	11th to 20th	Night	33% 5% 15% 20% 22% 5%	1875
	21st to end	Night	38% 7% 11% 25% 15% 4	1863
May	1st to 10th	Night	46% 8% 13% 20% 11% 2	2840
	11th to 20th	Night	48% 8% 12% 23% 9% 1	2813
	21st to end	Night	33% 10% 17% 26% 12% 3	2907
June	1st to 10th	Night	32% 12% 12% 29% 14% 1	1520
	11th to 20th	Night	35% 11% 16% 25% 12% 2	1520
	21st to end	Night	31% 11% 17% 21% 17% 3	1520
July	1st to 10th	Night	31% 13% 23% 17% 14% 2	2748
	11th to 20th	Night	38% 11% 19% 23% 8% 1	2786
	21st to end	Night	45% 10% 17% 19% 9%	2988
August	1st to 10th	Night	43% 9% 16% 25% 6% 1	2814
	11th to 20th	Night	41% 9% 14% 23% 12%	2834
	21st to end	Night	34% 9% 16% 31% 8% 2	3476
September	1st to 10th	Night	36% 8% 13% 20% 16% 6%	1900
	11th to 20th	Night	37% 8% 10% 24% 19% 3	2000
	21st to end	Night	46% 5% 10% 20% 17% 3	2141
October	1st to 10th	Night	42% 4 9% 19% 21% 6%	3800
	11th to 20th	Night	24% 4 8% 22% 29% 12%	3779
	21st to end	Night	20% 3 9% 31% 26% 11%	4120
November	1st to 10th	Night	34% 4 9% 21% 25% 6%	2341
	11th to 20th	Night	36% 4 7% 22% 24% 7%	2609
	21st to end	Night	34% 5% 9% 24% 22% 5%	2800
December	1st to 10th	Night	31% 5% 10% 27% 24% 4	4580
	11th to 20th	Night	42% 4 12% 18% 16% 7%	5208
	21st to end	Night	38% 7% 12% 24% 18% 2	6840

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% 25% 13% 3	300
	11th to 20th	Day	32% 31% 24% 13% 1	300
	21st to end	Day	24% 27% 34% 12% 2 1	330
February	1st to 10th	Day	26% 30% 32% 12% 1	300
	11th to 20th	Day	43% 24% 25% 7%	300
	21st to end	Day	31% 22% 27% 18% 2	373
March	1st to 10th	Day	23% 23% 28% 21% 5% 1	460
	11th to 20th	Day	24% 23% 29% 17% 6% 1	460
	21st to end	Day	24% 17% 31% 22% 5% 1	506
April	1st to 10th	Day	23% 24% 26% 17% 8% 1	460
	11th to 20th	Day	20% 16% 28% 20% 12% 4	452
	21st to end	Day	23% 16% 30% 19% 10% 2	460
May	1st to 10th	Day	21% 19% 28% 20% 8% 3	463
	11th to 20th	Day	22% 11% 27% 22% 15% 3	487
	21st to end	Day	17% 7% 24% 28% 18% 7%	529
June	1st to 10th	Day	12% 8% 28% 25% 21% 6%	490
	11th to 20th	Day	11% 9% 26% 28% 18% 8%	490
	21st to end	Day	9% 6% 27% 33% 18% 7%	490
July	1st to 10th	Day	10% 4 19% 30% 27% 10%	485
	11th to 20th	Day	5% 3 20% 34% 26% 12%	484
	21st to end	Day	11% 4 18% 36% 22% 9%	532
August	1st to 10th	Day	13% 5% 20% 26% 25% 11%	486
	11th to 20th	Day	11% 4 20% 27% 26% 12%	479
	21st to end	Day	11% 2 16% 32% 22% 17%	539
September	1st to 10th	Day	14% 4 17% 26% 23% 16%	490
	11th to 20th	Day	17% 3 16% 28% 26% 10%	490
	21st to end	Day	30% 9% 18% 23% 16% 4	490
October	1st to 10th	Day	19% 5% 22% 31% 17% 6%	490
	11th to 20th	Day	16% 14% 25% 23% 19% 3	490
	21st to end	Day	17% 13% 31% 24% 12% 3	539
November	1st to 10th	Day	17% 11% 28% 29% 12% 3	495
	11th to 20th	Day	22% 12% 31% 23% 11% 1	342
	21st to end	Day	21% 20% 33% 19% 7% 2	200
December	1st to 10th	Day	21% 22% 37% 14% 5% 1	200
	11th to 20th	Day	24% 19% 28% 21% 8% 2	200
	21st to end	Day	27% 20% 29% 18% 6% 1	250
January	1st to 10th	Night	18% 18% 38% 23% 3	800
	11th to 20th	Night	20% 16% 32% 29% 3	800
	21st to end	Night	16% 16% 39% 26% 3	880
February	1st to 10th	Night	16% 17% 36% 30% 2	800
	11th to 20th	Night	23% 21% 34% 21% 1	783
	21st to end	Night	20% 17% 37% 23% 3	647
March	1st to 10th	Night	15% 19% 33% 29% 4	760
	11th to 20th	Night	23% 16% 30% 23% 6% 1	760
	21st to end	Night	19% 14% 33% 27% 5%	836
April	1st to 10th	Night	16% 19% 37% 23% 6%	760
	11th to 20th	Night	14% 15% 29% 30% 10% 1	751
	21st to end	Night	19% 9% 30% 34% 8%	723
May	1st to 10th	Night	19% 10% 25% 30% 16% 1	570
	11th to 20th	Night	19% 6% 24% 35% 16% 1	561
	21st to end	Night	17% 1 16% 38% 25% 2	515
June	1st to 10th	Night	8% 2 19% 47% 23% 1	380
	11th to 20th	Night	9% 2 17% 41% 29% 2	380
	21st to end	Night	10% 2 18% 46% 22% 2	380
July	1st to 10th	Night	11% 1 12% 34% 36% 6%	521
	11th to 20th	Night	6% 1 9% 36% 42% 6%	552
	21st to end	Night	8% 3 12% 41% 31% 5%	624
August	1st to 10th	Night	12% 2 10% 39% 33% 4	567
	11th to 20th	Night	13% 2 10% 35% 36% 4	573
	21st to end	Night	13% 2 11% 36% 34% 4	836
September	1st to 10th	Night	15% 2 13% 35% 29% 6%	760
	11th to 20th	Night	14% 3 12% 36% 31% 4	760
	21st to end	Night	28% 4 16% 30% 20% 2	760
October	1st to 10th	Night	21% 5% 16% 31% 22% 4	760
	11th to 20th	Night	16% 9% 27% 31% 16% 1	760
	21st to end	Night	15% 9% 27% 35% 13% 1	836
November	1st to 10th	Night	13% 8% 28% 36% 12% 3	780
	11th to 20th	Night	17% 12% 28% 33% 9% 1	800
	21st to end	Night	16% 12% 31% 31% 10% 1	800
December	1st to 10th	Night	18% 12% 35% 28% 6% 1	800
	11th to 20th	Night	16% 10% 33% 35% 6%	800
	21st to end	Night	17% 12% 31% 37% 4	880

Page generated at 2025-02-22 06:51:36. Version ac07

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