Seven Ponds
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Seven Ponds clear sky chart from 2005-11-06 to 2025-08-05.

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% 10% 3 9% 5% 5% 5% 4 6% 7% 33%	124985
	Night	13% 10% 4 9% 5% 5% 5% 4 5% 7% 34%	123136
Transparency	Day	47% 7% 12% 20% 12% 1	128554
	Night	47% 7% 12% 21% 12% 1	127637
Seeing	Day	16% 13% 30% 23% 13% 5%	16385
	Night	18% 11% 31% 28% 11% 1	26004

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% 16% 7% 15% 6% 4 4 4 4 5% 25%	3617
	11th to 20th	Day	12% 17% 6% 15% 9% 8% 6% 4 5% 5% 12%	3620
	21st to end	Day	20% 16% 6% 12% 6% 5% 6% 3 4 4 18%	4391
February	1st to 10th	Day	13% 14% 5% 12% 9% 6% 5% 4 4 6% 22%	1800
	11th to 20th	Day	13% 13% 6% 12% 8% 6% 5% 4 5% 6% 23%	1870
	21st to end	Day	13% 15% 4 13% 7% 5% 4 4 4 6% 25%	1650
March	1st to 10th	Day	14% 12% 4 11% 6% 4 4 3 5% 5% 31%	4608
	11th to 20th	Day	11% 12% 4 9% 6% 5% 5% 3 6% 7% 32%	4980
	21st to end	Day	16% 14% 4 10% 6% 4 4 3 4 6% 28%	5465
April	1st to 10th	Day	15% 13% 4 8% 6% 4 4 4 5% 6% 30%	2315
	11th to 20th	Day	16% 9% 3 8% 4 5% 5% 4 6% 6% 35%	2552
	21st to end	Day	16% 10% 3 8% 6% 5% 4 3 5% 7% 35%	2600
May	1st to 10th	Day	17% 9% 3 7% 5% 5% 4 4 5% 6% 35%	5862
	11th to 20th	Day	16% 8% 2 7% 5% 5% 5% 3 7% 7% 34%	5861
	21st to end	Day	14% 7% 3 7% 4 4 4 4 5% 7% 41%	6433
June	1st to 10th	Day	9% 6% 2 7% 5% 4 4 5% 7% 9% 41%	2975
	11th to 20th	Day	10% 6% 2 7% 5% 5% 5% 5% 7% 8% 41%	3000
	21st to end	Day	9% 7% 2 7% 5% 5% 6% 5% 7% 10% 38%	2946
July	1st to 10th	Day	8% 6% 2 7% 5% 5% 5% 5% 8% 11% 38%	6360
	11th to 20th	Day	6% 5% 2 6% 4 5% 5% 4 6% 9% 46%	6360
	21st to end	Day	7% 5% 2 6% 5% 5% 6% 4 6% 9% 45%	6543
August	1st to 10th	Day	12% 5% 2 6% 4 5% 5% 4 7% 8% 41%	4156
	11th to 20th	Day	9% 6% 2 7% 5% 5% 5% 5% 7% 9% 40%	4044
	21st to end	Day	8% 6% 3 7% 5% 6% 6% 5% 7% 9% 38%	4518
September	1st to 10th	Day	10% 7% 2 7% 5% 6% 6% 5% 7% 8% 39%	2142
	11th to 20th	Day	10% 4 2 5% 4 3 5% 4 7% 10% 46%	2090
	21st to end	Day	15% 7% 2 7% 4 6% 5% 5% 7% 9% 33%	2090
October	1st to 10th	Day	13% 7% 2 6% 5% 5% 4 4 6% 6% 42%	2024
	11th to 20th	Day	17% 10% 3 7% 5% 5% 5% 4 4 6% 34%	1900
	21st to end	Day	18% 12% 4 8% 5% 5% 4 3 6% 7% 29%	1938
November	1st to 10th	Day	11% 9% 4 9% 6% 5% 4 3 6% 8% 36%	1762
	11th to 20th	Day	14% 11% 4 9% 7% 6% 5% 4 6% 6% 29%	1800
	21st to end	Day	15% 14% 6% 8% 6% 5% 5% 3 5% 7% 26%	1630
December	1st to 10th	Day	12% 14% 6% 12% 7% 5% 4 4 7% 8% 21%	2600
	11th to 20th	Day	16% 20% 6% 9% 5% 4 4 4 5% 5% 22%	2731
	21st to end	Day	23% 20% 7% 13% 5% 5% 4 2 4 5% 13%	3752
January	1st to 10th	Night	13% 12% 5% 11% 6% 4 5% 3 5% 7% 28%	6348
	11th to 20th	Night	10% 14% 6% 14% 9% 7% 6% 4 6% 6% 17%	6360
	21st to end	Night	16% 13% 8% 11% 6% 5% 5% 3 4 6% 22%	6564
February	1st to 10th	Night	13% 16% 6% 10% 8% 6% 6% 4 5% 5% 23%	2600
	11th to 20th	Night	13% 13% 4 11% 6% 5% 5% 4 6% 6% 27%	2415
	21st to end	Night	16% 12% 3 9% 6% 5% 5% 3 5% 6% 29%	1980
March	1st to 10th	Night	14% 11% 3 10% 5% 4 4 3 5% 7% 35%	5243
	11th to 20th	Night	8% 8% 3 8% 5% 5% 5% 4 6% 9% 40%	4980
	21st to end	Night	14% 10% 3 9% 5% 5% 4 3 4 6% 38%	5467
April	1st to 10th	Night	17% 10% 3 7% 5% 4 5% 4 5% 6% 34%	2100
	11th to 20th	Night	17% 7% 3 7% 5% 3 4 3 6% 7% 38%	1796
	21st to end	Night	16% 8% 2 5% 5% 4 4 4 7% 7% 38%	1800
May	1st to 10th	Night	19% 9% 3 7% 5% 5% 4 3 5% 7% 33%	4033
	11th to 20th	Night	15% 9% 3 7% 4 4 4 3 4 6% 40%	4032
	21st to end	Night	14% 6% 3 6% 4 4 4 4 5% 7% 45%	4404
June	1st to 10th	Night	10% 5% 2 6% 4 3 5% 4 6% 8% 47%	1420
	11th to 20th	Night	10% 6% 2 6% 4 3 5% 6% 7% 8% 44%	1400
	21st to end	Night	7% 7% 2 6% 4 5% 4 3 5% 8% 49%	1448
July	1st to 10th	Night	7% 5% 2 5% 4 4 4 4 7% 11% 47%	3618
	11th to 20th	Night	7% 4 2 5% 4 4 4 4 6% 10% 49%	3617
	21st to end	Night	7% 5% 2 6% 4 5% 5% 4 7% 8% 48%	4297
August	1st to 10th	Night	10% 5% 3 6% 4 3 3 4 5% 8% 48%	2861
	11th to 20th	Night	9% 6% 2 6% 4 4 4 4 6% 8% 48%	2785
	21st to end	Night	8% 6% 2 7% 4 4 5% 3 5% 7% 48%	3124
September	1st to 10th	Night	10% 6% 2 6% 4 4 5% 4 6% 6% 48%	2017
	11th to 20th	Night	9% 5% 1 5% 3 2 4 3 5% 7% 54%	2090
	21st to end	Night	14% 7% 3 7% 5% 4 4 3 6% 6% 42%	2090
October	1st to 10th	Night	13% 6% 3 6% 4 4 4 4 5% 7% 44%	2155
	11th to 20th	Night	18% 8% 3 8% 4 4 5% 4 5% 6% 36%	2280
	21st to end	Night	20% 9% 4 7% 5% 5% 5% 3 5% 6% 31%	2655
November	1st to 10th	Night	13% 8% 3 7% 4 4 4 4 5% 7% 43%	2536
	11th to 20th	Night	15% 10% 3 8% 5% 5% 5% 5% 6% 6% 30%	2600
	21st to end	Night	16% 14% 4 9% 6% 4 5% 3 6% 6% 27%	2765
December	1st to 10th	Night	11% 14% 5% 14% 6% 5% 5% 4 6% 7% 23%	4580
	11th to 20th	Night	13% 18% 6% 13% 7% 5% 4 4 5% 5% 20%	5468
	21st to end	Night	21% 22% 7% 10% 6% 4 4 2 4 5% 16%	7208

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	59% 8% 10% 15% 7% 1	3618
	11th to 20th	Day	70% 8% 10% 6% 6%	3620
	21st to end	Day	69% 5% 11% 9% 5% 1	4391
February	1st to 10th	Day	63% 7% 9% 14% 7%	1800
	11th to 20th	Day	61% 6% 9% 14% 8% 1	1879
	21st to end	Day	59% 7% 11% 14% 7% 2	1650
March	1st to 10th	Day	53% 6% 13% 17% 9% 2	4608
	11th to 20th	Day	49% 6% 14% 21% 8% 2	4980
	21st to end	Day	56% 6% 11% 15% 10% 2	5465
April	1st to 10th	Day	52% 8% 11% 19% 10% 1	2315
	11th to 20th	Day	47% 8% 11% 19% 13% 2	2552
	21st to end	Day	48% 6% 14% 18% 12% 1	2600
May	1st to 10th	Day	47% 7% 12% 18% 12% 4	5897
	11th to 20th	Day	45% 9% 12% 20% 12% 2	5865
	21st to end	Day	41% 6% 10% 20% 19% 4	6447
June	1st to 10th	Day	37% 7% 14% 25% 14% 2	2975
	11th to 20th	Day	38% 8% 13% 24% 15% 2	3000
	21st to end	Day	39% 9% 13% 23% 15% 1	2946
July	1st to 10th	Day	37% 7% 15% 24% 15% 1	6291
	11th to 20th	Day	31% 7% 14% 29% 17% 1	6285
	21st to end	Day	34% 7% 14% 22% 22% 1	6357
August	1st to 10th	Day	38% 8% 14% 22% 17% 1	4143
	11th to 20th	Day	38% 9% 12% 29% 11% 1	4083
	21st to end	Day	39% 7% 14% 28% 12% 1	4517
September	1st to 10th	Day	39% 9% 15% 24% 12% 2	2142
	11th to 20th	Day	33% 7% 15% 30% 14% 1	2090
	21st to end	Day	45% 7% 15% 22% 11% 1	2090
October	1st to 10th	Day	32% 6% 11% 31% 19% 2	3362
	11th to 20th	Day	41% 5% 12% 24% 17%	3140
	21st to end	Day	46% 6% 13% 23% 11% 1	3175
November	1st to 10th	Day	45% 7% 13% 23% 11% 1	1762
	11th to 20th	Day	54% 7% 13% 17% 9% 1	1800
	21st to end	Day	58% 7% 13% 16% 6% 1	1630
December	1st to 10th	Day	58% 7% 18% 12% 4	2600
	11th to 20th	Day	63% 7% 10% 12% 8%	2727
	21st to end	Day	74% 6% 9% 7% 5%	3752
January	1st to 10th	Night	53% 8% 11% 19% 7% 2	6348
	11th to 20th	Night	62% 9% 11% 12% 6% 1	6360
	21st to end	Night	63% 5% 10% 15% 7%	6564
February	1st to 10th	Night	61% 8% 9% 13% 7% 1	2600
	11th to 20th	Night	55% 8% 10% 18% 9% 1	2417
	21st to end	Night	54% 7% 12% 18% 8% 1	1980
March	1st to 10th	Night	47% 6% 15% 21% 10% 1	5243
	11th to 20th	Night	40% 7% 16% 23% 13% 1	4980
	21st to end	Night	46% 6% 12% 20% 14% 2	5467
April	1st to 10th	Night	50% 5% 11% 20% 12% 2	2100
	11th to 20th	Night	44% 7% 11% 19% 17% 2	1796
	21st to end	Night	43% 6% 13% 19% 16% 3	1800
May	1st to 10th	Night	48% 8% 10% 16% 13% 5%	4060
	11th to 20th	Night	43% 7% 12% 24% 11% 3	4033
	21st to end	Night	37% 7% 11% 24% 16% 5%	4412
June	1st to 10th	Night	34% 7% 12% 27% 19% 2	1420
	11th to 20th	Night	33% 9% 14% 24% 18% 2	1400
	21st to end	Night	34% 6% 12% 27% 20% 1	1448
July	1st to 10th	Night	30% 7% 16% 26% 17% 4	3580
	11th to 20th	Night	30% 7% 14% 29% 18% 1	3572
	21st to end	Night	30% 9% 14% 22% 23% 1	4170
August	1st to 10th	Night	34% 7% 14% 28% 16% 1	2850
	11th to 20th	Night	32% 8% 15% 31% 12% 2	2812
	21st to end	Night	34% 8% 12% 31% 15% 1	3124
September	1st to 10th	Night	35% 7% 14% 27% 16% 2	2017
	11th to 20th	Night	29% 7% 14% 30% 19% 2	2090
	21st to end	Night	40% 7% 11% 29% 12% 1	2090
October	1st to 10th	Night	27% 4 12% 31% 25% 1	3597
	11th to 20th	Night	43% 6% 11% 23% 17%	3779
	21st to end	Night	43% 5% 12% 28% 11% 1	4368
November	1st to 10th	Night	40% 7% 12% 26% 14% 1	2536
	11th to 20th	Night	52% 8% 13% 18% 9% 1	2600
	21st to end	Night	56% 6% 15% 16% 6% 1	2765
December	1st to 10th	Night	58% 7% 18% 14% 2	4580
	11th to 20th	Night	62% 8% 10% 13% 6%	5471
	21st to end	Night	71% 6% 9% 8% 6%	7208

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	20% 21% 38% 15% 6%	300
	11th to 20th	Day	20% 21% 43% 12% 4 1	300
	21st to end	Day	26% 18% 35% 16% 4 1	330
February	1st to 10th	Day	21% 24% 37% 14% 3 1	300
	11th to 20th	Day	24% 22% 38% 15% 2	300
	21st to end	Day	23% 31% 33% 11% 2	249
March	1st to 10th	Day	26% 21% 36% 15% 2 1	350
	11th to 20th	Day	19% 16% 35% 22% 7% 1	500
	21st to end	Day	27% 15% 32% 20% 5% 1	550
April	1st to 10th	Day	19% 19% 35% 19% 7% 1	500
	11th to 20th	Day	25% 17% 32% 14% 9% 4	492
	21st to end	Day	23% 14% 27% 24% 9% 2	500
May	1st to 10th	Day	21% 16% 29% 22% 10% 2	503
	11th to 20th	Day	18% 11% 32% 21% 13% 5%	527
	21st to end	Day	16% 10% 24% 26% 16% 8%	573
June	1st to 10th	Day	12% 10% 33% 29% 12% 4	730
	11th to 20th	Day	12% 9% 29% 31% 14% 4	730
	21st to end	Day	11% 9% 29% 32% 15% 5%	730
July	1st to 10th	Day	8% 6% 23% 32% 20% 11%	721
	11th to 20th	Day	9% 8% 27% 29% 19% 7%	718
	21st to end	Day	7% 6% 25% 30% 23% 9%	630
August	1st to 10th	Day	10% 5% 21% 24% 27% 13%	502
	11th to 20th	Day	9% 5% 20% 29% 25% 12%	479
	21st to end	Day	12% 6% 21% 28% 22% 12%	539
September	1st to 10th	Day	11% 7% 25% 25% 19% 12%	490
	11th to 20th	Day	10% 3 19% 25% 28% 14%	490
	21st to end	Day	17% 13% 23% 22% 19% 8%	490
October	1st to 10th	Day	17% 10% 28% 23% 14% 8%	490
	11th to 20th	Day	18% 16% 34% 22% 7% 1	490
	21st to end	Day	24% 17% 35% 18% 5% 1	387
November	1st to 10th	Day	15% 23% 34% 19% 8% 1	300
	11th to 20th	Day	21% 22% 34% 16% 6% 1	300
	21st to end	Day	23% 23% 37% 13% 4	215
December	1st to 10th	Day	20% 23% 36% 14% 7% 1	200
	11th to 20th	Day	23% 29% 34% 12% 3 1	200
	21st to end	Day	26% 21% 36% 13% 3	280
January	1st to 10th	Night	20% 15% 41% 19% 5% 1	1000
	11th to 20th	Night	22% 17% 36% 21% 3 1	1000
	21st to end	Night	19% 14% 37% 25% 5%	915
February	1st to 10th	Night	21% 17% 39% 21% 2	800
	11th to 20th	Night	20% 18% 35% 22% 5%	783
	21st to end	Night	22% 18% 38% 20% 2	660
March	1st to 10th	Night	21% 14% 37% 24% 5%	800
	11th to 20th	Night	17% 16% 37% 24% 5% 1	800
	21st to end	Night	22% 12% 33% 26% 6% 1	880
April	1st to 10th	Night	21% 16% 34% 25% 3	700
	11th to 20th	Night	21% 12% 34% 23% 8% 2	593
	21st to end	Night	18% 10% 32% 33% 7%	600
May	1st to 10th	Night	16% 9% 35% 32% 9% 1	600
	11th to 20th	Night	19% 6% 29% 32% 13% 1	591
	21st to end	Night	10% 6% 26% 39% 18% 2	650
June	1st to 10th	Night	11% 6% 28% 44% 11%	420
	11th to 20th	Night	11% 5% 31% 42% 12%	400
	21st to end	Night	8% 6% 23% 46% 15% 1	448
July	1st to 10th	Night	8% 2 20% 41% 25% 3	585
	11th to 20th	Night	9% 4 20% 42% 22% 3	582
	21st to end	Night	6% 4 20% 45% 23% 2	657
August	1st to 10th	Night	8% 4 16% 39% 30% 2	579
	11th to 20th	Night	8% 2 19% 39% 27% 4	564
	21st to end	Night	11% 3 19% 36% 29% 3	627
September	1st to 10th	Night	12% 5% 21% 35% 23% 5%	689
	11th to 20th	Night	10% 4 19% 34% 29% 4	760
	21st to end	Night	17% 7% 22% 33% 19% 3	760
October	1st to 10th	Night	15% 8% 28% 29% 17% 2	760
	11th to 20th	Night	21% 15% 29% 26% 8% 1	760
	21st to end	Night	24% 14% 33% 25% 5%	836
November	1st to 10th	Night	19% 13% 30% 26% 11% 1	780
	11th to 20th	Night	20% 16% 35% 22% 7% 1	800
	21st to end	Night	23% 16% 36% 20% 5%	800
December	1st to 10th	Night	22% 16% 37% 20% 4	800
	11th to 20th	Night	22% 14% 41% 21% 3	925
	21st to end	Night	28% 14% 35% 21% 2	1100

Page generated at 2025-08-02 01:32:23. Version ac07

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