Snow Moon Camp Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Snow Moon Camp Observatory clear sky chart from 2005-11-06 to 2025-07-21.

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% 9% 4 9% 6% 5% 5% 4 6% 7% 32%	120453
	Night	11% 9% 4 9% 6% 5% 5% 4 6% 7% 35%	118669
Transparency	Day	42% 10% 13% 17% 13% 4	124167
	Night	39% 11% 13% 18% 13% 5%	123092
Seeing	Day	22% 18% 25% 19% 11% 5%	16050
	Night	20% 16% 22% 24% 16% 2	26123

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	9% 10% 8% 11% 5% 4 4 4 6% 6% 34%	4056
	11th to 20th	Day	8% 9% 6% 14% 6% 6% 6% 4 5% 4 33%	4060
	21st to end	Day	12% 11% 5% 9% 4 4 4 4 4 4 37%	4466
February	1st to 10th	Day	12% 11% 5% 10% 6% 6% 5% 4 5% 5% 32%	1800
	11th to 20th	Day	16% 12% 4 10% 6% 4 3 4 5% 5% 31%	1947
	21st to end	Day	16% 9% 3 10% 5% 4 3 4 5% 6% 35%	1650
March	1st to 10th	Day	14% 10% 4 9% 6% 6% 5% 4 4 5% 33%	4925
	11th to 20th	Day	9% 7% 3 8% 5% 4 4 3 5% 7% 45%	4980
	21st to end	Day	14% 8% 3 7% 5% 4 4 4 5% 7% 38%	5465
April	1st to 10th	Day	10% 9% 4 8% 5% 4 5% 4 7% 7% 37%	2200
	11th to 20th	Day	14% 9% 3 7% 5% 4 4 3 5% 7% 38%	2396
	21st to end	Day	14% 10% 3 8% 6% 4 6% 3 5% 6% 36%	2600
May	1st to 10th	Day	12% 10% 5% 10% 6% 7% 7% 5% 7% 7% 24%	5862
	11th to 20th	Day	15% 11% 4 11% 7% 7% 6% 4 7% 7% 21%	5861
	21st to end	Day	13% 8% 3 8% 6% 6% 6% 5% 7% 9% 28%	6433
June	1st to 10th	Day	11% 8% 2 9% 6% 7% 7% 6% 7% 8% 30%	2600
	11th to 20th	Day	8% 7% 3 9% 7% 7% 7% 6% 8% 9% 29%	2600
	21st to end	Day	9% 7% 3 8% 6% 7% 7% 6% 8% 9% 30%	2600
July	1st to 10th	Day	7% 6% 3 9% 7% 7% 8% 6% 8% 9% 30%	4250
	11th to 20th	Day	10% 8% 3 9% 7% 7% 7% 5% 7% 8% 29%	4250
	21st to end	Day	16% 10% 4 14% 9% 7% 7% 4 6% 6% 15%	4466
August	1st to 10th	Day	12% 8% 3 11% 8% 7% 7% 6% 8% 9% 21%	4104
	11th to 20th	Day	8% 8% 3 11% 7% 8% 8% 6% 8% 9% 25%	4044
	21st to end	Day	6% 5% 2 7% 6% 6% 5% 5% 7% 11% 40%	4300
September	1st to 10th	Day	11% 7% 3 8% 6% 7% 6% 4 6% 8% 34%	2090
	11th to 20th	Day	13% 10% 4 10% 6% 5% 6% 4 6% 7% 30%	2090
	21st to end	Day	15% 9% 4 7% 6% 5% 5% 4 5% 8% 32%	2090
October	1st to 10th	Day	14% 8% 2 7% 4 4 3 3 5% 7% 43%	2005
	11th to 20th	Day	12% 8% 2 7% 4 4 4 3 5% 5% 47%	1900
	21st to end	Day	12% 9% 3 7% 4 4 3 2 4 5% 46%	2090
November	1st to 10th	Day	9% 6% 4 7% 4 4 4 3 5% 6% 49%	1904
	11th to 20th	Day	10% 7% 2 8% 5% 5% 4 5% 5% 7% 43%	1800
	21st to end	Day	11% 10% 3 7% 5% 5% 3 3 5% 5% 42%	1800
December	1st to 10th	Day	10% 9% 4 8% 5% 5% 5% 4 5% 6% 38%	2930
	11th to 20th	Day	14% 10% 6% 8% 5% 4 5% 4 6% 6% 31%	3373
	21st to end	Day	13% 8% 5% 10% 6% 5% 6% 5% 6% 7% 30%	4466
January	1st to 10th	Night	9% 13% 5% 10% 7% 7% 5% 5% 8% 6% 25%	5889
	11th to 20th	Night	8% 8% 4 13% 9% 7% 5% 4 5% 5% 33%	5900
	21st to end	Night	11% 12% 5% 9% 5% 4 4 3 5% 6% 37%	6490
February	1st to 10th	Night	12% 9% 4 10% 6% 4 4 5% 6% 6% 34%	2598
	11th to 20th	Night	16% 11% 4 9% 7% 6% 4 5% 5% 4 29%	2338
	21st to end	Night	13% 9% 4 11% 6% 5% 5% 4 5% 6% 31%	1980
March	1st to 10th	Night	16% 12% 4 11% 5% 4 4 3 4 4 33%	4928
	11th to 20th	Night	10% 8% 3 8% 4 3 4 3 5% 6% 47%	4980
	21st to end	Night	10% 9% 4 8% 5% 6% 5% 3 5% 7% 39%	5467
April	1st to 10th	Night	11% 9% 4 9% 6% 4 4 4 5% 8% 37%	2200
	11th to 20th	Night	11% 9% 3 7% 4 4 5% 4 6% 6% 40%	1966
	21st to end	Night	12% 8% 3 8% 4 6% 4 4 5% 7% 39%	1800
May	1st to 10th	Night	14% 11% 4 9% 6% 5% 5% 4 8% 9% 27%	4033
	11th to 20th	Night	13% 13% 5% 11% 6% 5% 5% 4 6% 7% 23%	4032
	21st to end	Night	14% 13% 4 9% 5% 4 4 4 6% 8% 29%	4421
June	1st to 10th	Night	7% 8% 4 7% 7% 5% 5% 6% 8% 10% 34%	1800
	11th to 20th	Night	7% 7% 3 6% 5% 5% 6% 4 9% 11% 37%	1800
	21st to end	Night	6% 8% 3 7% 6% 5% 5% 5% 8% 10% 38%	1800
July	1st to 10th	Night	5% 7% 3 9% 6% 7% 7% 5% 8% 10% 33%	2930
	11th to 20th	Night	8% 6% 3 8% 5% 4 6% 5% 8% 10% 38%	2930
	21st to end	Night	11% 12% 5% 12% 8% 7% 6% 5% 6% 7% 21%	3087
August	1st to 10th	Night	10% 8% 4 10% 7% 6% 6% 6% 7% 10% 26%	2825
	11th to 20th	Night	9% 9% 3 11% 6% 5% 5% 5% 7% 7% 32%	2785
	21st to end	Night	5% 4 2 5% 4 4 5% 4 6% 10% 51%	3305
September	1st to 10th	Night	10% 9% 3 7% 6% 5% 4 4 7% 6% 39%	2090
	11th to 20th	Night	13% 8% 3 9% 5% 4 4 3 6% 7% 37%	2090
	21st to end	Night	11% 9% 4 9% 6% 5% 5% 3 4 5% 39%	2090
October	1st to 10th	Night	13% 8% 3 7% 4 3 4 4 4 6% 44%	2174
	11th to 20th	Night	11% 8% 4 7% 4 4 3 3 5% 5% 45%	2280
	21st to end	Night	9% 9% 4 8% 3 4 4 3 5% 6% 46%	2508
November	1st to 10th	Night	10% 8% 2 8% 5% 4 4 4 4 5% 45%	2391
	11th to 20th	Night	11% 8% 4 8% 4 4 4 4 5% 7% 42%	2600
	21st to end	Night	11% 8% 3 8% 4 4 4 4 6% 5% 43%	2600
December	1st to 10th	Night	10% 8% 4 12% 6% 5% 4 4 4 5% 39%	4250
	11th to 20th	Night	15% 10% 5% 13% 6% 6% 6% 4 5% 5% 26%	4822
	21st to end	Night	12% 12% 6% 13% 6% 4 5% 4 6% 7% 27%	6490

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	34% 11% 14% 13% 23% 5%	4057
	11th to 20th	Day	34% 14% 12% 11% 24% 5%	4060
	21st to end	Day	41% 8% 11% 16% 19% 5%	4466
February	1st to 10th	Day	48% 9% 10% 15% 15% 3	1800
	11th to 20th	Day	49% 8% 10% 14% 15% 3	1957
	21st to end	Day	46% 7% 11% 14% 15% 5%	1650
March	1st to 10th	Day	42% 9% 10% 16% 15% 8%	4925
	11th to 20th	Day	34% 7% 9% 20% 18% 13%	4980
	21st to end	Day	42% 6% 11% 24% 14% 4	5465
April	1st to 10th	Day	41% 8% 12% 21% 15% 3	2200
	11th to 20th	Day	41% 8% 12% 18% 17% 4	2396
	21st to end	Day	45% 10% 11% 21% 11% 2	2600
May	1st to 10th	Day	50% 13% 13% 17% 7% 1	5897
	11th to 20th	Day	54% 12% 13% 16% 4 1	5865
	21st to end	Day	42% 13% 14% 17% 12% 2	6447
June	1st to 10th	Day	46% 12% 14% 18% 9% 1	2600
	11th to 20th	Day	45% 13% 14% 15% 11% 1	2600
	21st to end	Day	43% 13% 15% 17% 11% 1	2600
July	1st to 10th	Day	44% 13% 17% 16% 8% 1	4185
	11th to 20th	Day	47% 13% 18% 16% 5% 1	4181
	21st to end	Day	64% 11% 10% 11% 3 1	4324
August	1st to 10th	Day	52% 13% 16% 15% 3	4091
	11th to 20th	Day	45% 14% 17% 15% 6% 2	4083
	21st to end	Day	35% 11% 19% 27% 8% 1	4300
September	1st to 10th	Day	45% 9% 13% 17% 14% 3	2090
	11th to 20th	Day	50% 8% 11% 17% 14% 1	2090
	21st to end	Day	48% 8% 13% 15% 12% 4	2090
October	1st to 10th	Day	29% 8% 10% 16% 25% 12%	3330
	11th to 20th	Day	24% 6% 8% 22% 17% 21%	3140
	21st to end	Day	26% 8% 8% 26% 15% 17%	3428
November	1st to 10th	Day	33% 7% 9% 19% 25% 6%	1904
	11th to 20th	Day	35% 7% 10% 17% 24% 7%	1800
	21st to end	Day	38% 7% 11% 19% 22% 4	1800
December	1st to 10th	Day	37% 9% 10% 16% 23% 5%	2930
	11th to 20th	Day	43% 10% 12% 15% 18% 3	3370
	21st to end	Day	44% 8% 14% 20% 11% 3	4466
January	1st to 10th	Night	34% 13% 17% 14% 14% 8%	5889
	11th to 20th	Night	36% 13% 11% 13% 18% 10%	5900
	21st to end	Night	40% 8% 10% 13% 23% 5%	6490
February	1st to 10th	Night	43% 10% 13% 18% 15% 3	2598
	11th to 20th	Night	47% 11% 11% 14% 13% 4	2339
	21st to end	Night	45% 11% 11% 16% 12% 5%	1980
March	1st to 10th	Night	42% 11% 9% 15% 14% 8%	4928
	11th to 20th	Night	31% 8% 10% 20% 17% 14%	4980
	21st to end	Night	40% 9% 12% 23% 12% 4	5467
April	1st to 10th	Night	39% 11% 13% 20% 14% 3	2200
	11th to 20th	Night	37% 10% 13% 20% 16% 5%	1966
	21st to end	Night	41% 9% 14% 23% 12% 1	1800
May	1st to 10th	Night	45% 16% 14% 18% 7% 1	4060
	11th to 20th	Night	50% 14% 15% 17% 4	4033
	21st to end	Night	41% 17% 16% 18% 7% 1	4429
June	1st to 10th	Night	40% 14% 17% 20% 10% 1	1800
	11th to 20th	Night	34% 14% 21% 22% 9% 1	1800
	21st to end	Night	35% 14% 18% 20% 11% 3	1800
July	1st to 10th	Night	38% 16% 18% 19% 7% 1	2885
	11th to 20th	Night	34% 14% 27% 20% 4 1	2876
	21st to end	Night	54% 16% 14% 12% 3	2988
August	1st to 10th	Night	45% 15% 21% 14% 5%	2814
	11th to 20th	Night	39% 16% 20% 16% 7% 1	2812
	21st to end	Night	27% 9% 20% 33% 8% 3	3305
September	1st to 10th	Night	41% 10% 14% 18% 13% 4	2090
	11th to 20th	Night	44% 9% 13% 18% 15% 1	2090
	21st to end	Night	45% 7% 12% 20% 14% 2	2090
October	1st to 10th	Night	29% 11% 12% 17% 18% 14%	3629
	11th to 20th	Night	25% 7% 9% 18% 19% 21%	3779
	21st to end	Night	27% 8% 8% 22% 17% 17%	4120
November	1st to 10th	Night	37% 7% 11% 18% 21% 7%	2391
	11th to 20th	Night	36% 7% 10% 18% 21% 8%	2600
	21st to end	Night	37% 8% 9% 21% 21% 5%	2600
December	1st to 10th	Night	36% 12% 11% 17% 21% 4	4250
	11th to 20th	Night	48% 10% 11% 14% 13% 3	4824
	21st to end	Night	44% 13% 14% 15% 11% 3	6490

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	42% 30% 21% 6% 1	300
	11th to 20th	Day	42% 24% 28% 6% 1	300
	21st to end	Day	35% 35% 22% 7% 1	330
February	1st to 10th	Day	32% 32% 26% 8% 1	300
	11th to 20th	Day	49% 30% 18% 3	300
	21st to end	Day	41% 32% 23% 4	249
March	1st to 10th	Day	32% 26% 26% 12% 4	490
	11th to 20th	Day	32% 30% 23% 11% 2 1	500
	21st to end	Day	31% 28% 26% 11% 4	550
April	1st to 10th	Day	28% 27% 26% 13% 6% 1	500
	11th to 20th	Day	27% 25% 23% 15% 9% 2	492
	21st to end	Day	23% 21% 29% 15% 8% 3	500
May	1st to 10th	Day	23% 23% 33% 11% 7% 4	503
	11th to 20th	Day	22% 17% 27% 19% 10% 5%	527
	21st to end	Day	18% 14% 23% 23% 13% 10%	573
June	1st to 10th	Day	15% 12% 30% 24% 14% 6%	530
	11th to 20th	Day	8% 10% 29% 28% 17% 7%	530
	21st to end	Day	9% 11% 31% 27% 13% 8%	530
July	1st to 10th	Day	9% 6% 24% 30% 20% 11%	525
	11th to 20th	Day	8% 8% 18% 35% 23% 9%	524
	21st to end	Day	11% 5% 25% 26% 20% 12%	532
August	1st to 10th	Day	15% 7% 26% 24% 15% 13%	486
	11th to 20th	Day	10% 9% 23% 26% 23% 10%	479
	21st to end	Day	12% 4 20% 27% 21% 16%	539
September	1st to 10th	Day	12% 5% 19% 29% 24% 10%	490
	11th to 20th	Day	16% 8% 17% 26% 24% 9%	490
	21st to end	Day	23% 13% 21% 23% 15% 4	490
October	1st to 10th	Day	20% 13% 22% 21% 20% 4	490
	11th to 20th	Day	17% 21% 26% 20% 15% 2	490
	21st to end	Day	18% 22% 25% 23% 8% 4	539
November	1st to 10th	Day	19% 19% 30% 21% 10% 2	442
	11th to 20th	Day	25% 26% 30% 14% 3 1	300
	21st to end	Day	27% 24% 29% 15% 4 1	300
December	1st to 10th	Day	33% 29% 28% 9% 1	300
	11th to 20th	Day	30% 22% 34% 11% 2	300
	21st to end	Day	28% 27% 32% 8% 4 1	330
January	1st to 10th	Night	31% 27% 23% 16% 3	800
	11th to 20th	Night	30% 24% 26% 17% 4	800
	21st to end	Night	27% 27% 27% 16% 3	880
February	1st to 10th	Night	22% 25% 26% 24% 3	800
	11th to 20th	Night	33% 31% 22% 13% 1	783
	21st to end	Night	26% 27% 33% 12% 1	660
March	1st to 10th	Night	24% 24% 31% 18% 4	800
	11th to 20th	Night	25% 24% 27% 17% 6%	800
	21st to end	Night	22% 22% 31% 20% 5%	880
April	1st to 10th	Night	24% 21% 26% 22% 6%	800
	11th to 20th	Night	21% 20% 26% 22% 11% 1	749
	21st to end	Night	15% 19% 23% 32% 10% 1	600
May	1st to 10th	Night	17% 16% 29% 24% 12% 1	600
	11th to 20th	Night	17% 9% 25% 31% 16% 2	591
	21st to end	Night	15% 10% 17% 29% 24% 6%	650
June	1st to 10th	Night	9% 6% 22% 32% 27% 4	600
	11th to 20th	Night	9% 6% 21% 27% 33% 5%	600
	21st to end	Night	8% 7% 18% 32% 32% 3	600
July	1st to 10th	Night	11% 3 14% 28% 40% 5%	585
	11th to 20th	Night	7% 4 12% 29% 41% 7%	582
	21st to end	Night	6% 6% 12% 30% 38% 9%	624
August	1st to 10th	Night	12% 4 14% 28% 37% 5%	567
	11th to 20th	Night	13% 5% 13% 29% 33% 7%	564
	21st to end	Night	11% 3 11% 30% 37% 8%	712
September	1st to 10th	Night	12% 7% 14% 29% 30% 7%	760
	11th to 20th	Night	20% 4 14% 27% 30% 5%	760
	21st to end	Night	21% 9% 15% 27% 25% 2	760
October	1st to 10th	Night	15% 14% 19% 23% 23% 6%	760
	11th to 20th	Night	18% 17% 21% 27% 14% 3	760
	21st to end	Night	20% 17% 22% 27% 12% 2	836
November	1st to 10th	Night	18% 15% 23% 29% 13% 2	780
	11th to 20th	Night	23% 17% 20% 29% 9% 1	800
	21st to end	Night	23% 19% 24% 24% 10% 1	800
December	1st to 10th	Night	26% 22% 25% 20% 6%	800
	11th to 20th	Night	23% 23% 25% 24% 5% 1	800
	21st to end	Night	28% 19% 26% 23% 4	880

Page generated at 2025-07-18 01:10:01. Version ac07

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