Meadow View Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Meadow View Observatory clear sky chart from 2005-11-06 to 2026-09-29.

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	9% 3 1 3 2 2 2 2 4 5% 67%	158036
	Night	11% 4 1 3 2 2 3 2 4 5% 61%	150882
Transparency	Day	21% 3 6% 18% 25% 26%	152940
	Night	26% 4 7% 17% 22% 23%	146968
Seeing	Day	11% 7% 18% 28% 27% 10%	17588
	Night	12% 4 17% 37% 27% 3	26758

By Month

Percentage Cloud Cover SW (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	25% 8% 2 5% 3 3 3 3 5% 6% 37%	4722
	11th to 20th	Day	15% 4 1 4 2 2 2 2 3 4 60%	5202
	21st to end	Day	18% 5% 2 5% 3 2 4 3 5% 8% 46%	5843
February	1st to 10th	Day	20% 5% 1 3 2 3 3 3 5% 6% 48%	1890
	11th to 20th	Day	18% 7% 2 6% 3 3 4 2 4 7% 46%	1913
	21st to end	Day	18% 5% 2 4 3 3 3 3 5% 7% 48%	1730
March	1st to 10th	Day	21% 9% 3 7% 3 3 3 3 4 5% 40%	4858
	11th to 20th	Day	20% 6% 1 4 3 3 3 2 4 6% 48%	5110
	21st to end	Day	17% 8% 2 5% 4 4 4 3 6% 7% 40%	5757
April	1st to 10th	Day	13% 5% 2 4 4 3 4 3 5% 8% 49%	2520
	11th to 20th	Day	12% 4 1 4 2 2 3 4 5% 5% 57%	2489
	21st to end	Day	6% 3 2 3 2 3 4 3 4 7% 62%	2520
May	1st to 10th	Day	6% 3 1 3 2 2 2 2 3 6% 70%	7452
	11th to 20th	Day	2 1 1 1 1 1 1 2 2 5% 81%	8159
	21st to end	Day	2 2 1 2 2 2 2 2 4 6% 76%	8992
June	1st to 10th	Day	5% 3 1 2 2 2 3 3 5% 8% 66%	2940
	11th to 20th	Day	2 1 2 1 1 2 2 3 5% 80%	2940
	21st to end	Day	2 1 1 1 1 1 2 1 2 3 85%	2940
July	1st to 10th	Day	1 1 1 1 1 1 1 2 91%	8219
	11th to 20th	Day	3 2 1 3 2 1 2 1 2 2 82%	8220
	21st to end	Day	1 1 1 1 1 2 1 3 4 86%	8312
August	1st to 10th	Day	1 1 1 1 1 1 2 2 4 86%	7547
	11th to 20th	Day	1 1 1 1 1 2 3 4 86%	7302
	21st to end	Day	2 2 1 2 2 2 1 2 3 4 80%	7750
September	1st to 10th	Day	1 1 1 1 1 2 1 3 4 85%	2520
	11th to 20th	Day	3 2 1 3 2 1 2 2 3 5% 76%	2520
	21st to end	Day	4 1 1 2 1 1 1 2 3 5% 79%	2218
October	1st to 10th	Day	3 2 2 2 2 2 2 3 4 78%	3280
	11th to 20th	Day	6% 2 1 3 2 2 2 2 5% 6% 70%	3261
	21st to end	Day	7% 3 1 4 3 3 4 3 6% 8% 58%	3558
November	1st to 10th	Day	14% 3 1 4 2 3 3 3 5% 7% 55%	1914
	11th to 20th	Day	16% 4 1 5% 3 3 4 3 5% 8% 47%	1858
	21st to end	Day	14% 4 1 4 2 3 4 3 4 6% 55%	1680
December	1st to 10th	Day	11% 3 1 3 2 3 3 3 5% 6% 60%	2700
	11th to 20th	Day	31% 6% 2 5% 4 4 3 3 5% 8% 29%	3108
	21st to end	Day	33% 7% 2 5% 3 3 3 2 4 6% 31%	4092
January	1st to 10th	Night	23% 7% 2 5% 3 3 3 3 5% 7% 38%	8172
	11th to 20th	Night	15% 3 1 3 2 2 2 2 4 5% 60%	7764
	21st to end	Night	19% 6% 2 6% 4 4 3 3 4 6% 45%	8371
February	1st to 10th	Night	19% 4 1 4 3 3 3 3 4 6% 49%	2730
	11th to 20th	Night	17% 6% 2 4 3 4 3 4 5% 6% 46%	2593
	21st to end	Night	17% 5% 2 4 4 4 4 3 4 6% 49%	2076
March	1st to 10th	Night	18% 9% 3 7% 4 3 3 3 4 7% 40%	5254
	11th to 20th	Night	21% 6% 2 4 2 2 2 2 4 5% 49%	5110
	21st to end	Night	18% 8% 3 6% 4 3 4 3 5% 7% 38%	5459
April	1st to 10th	Night	10% 5% 2 5% 4 4 4 4 6% 9% 48%	2100
	11th to 20th	Night	10% 5% 1 4 3 3 3 2 5% 7% 56%	2079
	21st to end	Night	7% 4 2 3 2 2 3 2 4 6% 63%	2100
May	1st to 10th	Night	6% 4 1 4 3 2 2 3 4 5% 67%	5501
	11th to 20th	Night	2 2 1 3 2 2 2 2 4 6% 74%	4700
	21st to end	Night	4 2 1 2 2 2 2 2 3 6% 75%	5181
June	1st to 10th	Night	5% 2 1 4 3 3 3 3 5% 9% 63%	1680
	11th to 20th	Night	1 1 1 2 2 2 2 3 6% 79%	1680
	21st to end	Night	1 1 1 2 1 1 2 2 3 3 82%	1680
July	1st to 10th	Night	1 1 1 1 2 3 90%	4740
	11th to 20th	Night	3 3 1 3 1 1 1 1 2 1 82%	4740
	21st to end	Night	1 1 1 1 2 2 3 4 85%	5781
August	1st to 10th	Night	2 1 1 1 1 1 1 1 3 2 85%	5275
	11th to 20th	Night	1 1 1 2 2 2 3 4 84%	5568
	21st to end	Night	2 2 1 3 2 2 2 2 3 4 78%	6499
September	1st to 10th	Night	2 1 1 1 1 1 1 2 3 86%	2100
	11th to 20th	Night	3 2 1 2 2 2 2 2 3 5% 76%	2100
	21st to end	Night	3 1 1 2 1 1 2 2 4 5% 79%	2352
October	1st to 10th	Night	3 2 1 2 2 2 2 1 3 3 79%	3920
	11th to 20th	Night	4 2 1 2 1 2 2 2 4 5% 75%	3897
	21st to end	Night	8% 2 1 3 2 3 4 2 5% 6% 64%	4253
November	1st to 10th	Night	13% 4 1 3 2 3 4 3 5% 7% 54%	2605
	11th to 20th	Night	14% 4 1 4 3 3 3 4 6% 8% 50%	2760
	21st to end	Night	13% 5% 2 4 2 3 3 3 4 6% 56%	2940
December	1st to 10th	Night	12% 3 1 3 2 2 3 2 5% 7% 61%	4700
	11th to 20th	Night	32% 6% 2 4 3 4 5% 3 5% 8% 27%	5316
	21st to end	Night	33% 6% 2 6% 4 3 3 3 3 4 32%	7106

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	48% 6% 10% 22% 10% 4	4723
	11th to 20th	Day	31% 4 4 14% 24% 22%	5202
	21st to end	Day	38% 4 9% 18% 16% 14%	5843
February	1st to 10th	Day	37% 5% 11% 18% 19% 9%	1890
	11th to 20th	Day	39% 6% 9% 20% 20% 6%	1922
	21st to end	Day	36% 5% 12% 25% 17% 7%	1730
March	1st to 10th	Day	45% 7% 7% 21% 17% 3	4858
	11th to 20th	Day	38% 4 9% 23% 16% 9%	5110
	21st to end	Day	39% 9% 13% 24% 12% 2	5757
April	1st to 10th	Day	34% 6% 11% 23% 20% 6%	2520
	11th to 20th	Day	29% 5% 11% 23% 23% 10%	2492
	21st to end	Day	21% 5% 13% 29% 24% 8%	2520
May	1st to 10th	Day	17% 3 8% 24% 29% 19%	7452
	11th to 20th	Day	9% 2 5% 21% 39% 24%	8162
	21st to end	Day	11% 3 8% 30% 36% 13%	8994
June	1st to 10th	Day	17% 5% 10% 25% 27% 15%	2940
	11th to 20th	Day	8% 3 8% 20% 32% 29%	2940
	21st to end	Day	7% 1 3 14% 33% 41%	2940
July	1st to 10th	Day	4 1 1 9% 24% 60%	8151
	11th to 20th	Day	12% 1 1 4 15% 66%	8145
	21st to end	Day	6% 1 4 14% 26% 49%	8126
August	1st to 10th	Day	7% 2 2 5% 24% 60%	5976
	11th to 20th	Day	6% 1 1 19% 38% 34%	5761
	21st to end	Day	11% 1 2 14% 39% 32%	6077
September	1st to 10th	Day	6% 1 3 10% 26% 53%	2520
	11th to 20th	Day	12% 3 6% 20% 36% 23%	2520
	21st to end	Day	11% 2 6% 19% 30% 32%	2218
October	1st to 10th	Day	12% 3 3 12% 24% 46%	3280
	11th to 20th	Day	17% 3 5% 24% 30% 21%	3261
	21st to end	Day	23% 4 7% 22% 30% 14%	3558
November	1st to 10th	Day	28% 5% 11% 23% 20% 13%	1914
	11th to 20th	Day	35% 7% 11% 22% 16% 8%	1858
	21st to end	Day	29% 5% 10% 20% 22% 13%	1680
December	1st to 10th	Day	26% 4 7% 24% 28% 11%	2700
	11th to 20th	Day	55% 4 11% 16% 11% 3	3108
	21st to end	Day	54% 7% 11% 17% 9% 2	4092
January	1st to 10th	Night	46% 6% 14% 19% 11% 4	8172
	11th to 20th	Night	28% 5% 6% 13% 24% 23%	7764
	21st to end	Night	42% 4 7% 13% 15% 18%	8371
February	1st to 10th	Night	36% 5% 9% 21% 18% 13%	2730
	11th to 20th	Night	36% 5% 9% 20% 21% 8%	2595
	21st to end	Night	37% 5% 9% 22% 19% 8%	2076
March	1st to 10th	Night	41% 9% 11% 19% 15% 5%	5254
	11th to 20th	Night	37% 5% 9% 20% 19% 9%	5110
	21st to end	Night	42% 8% 13% 22% 12% 3	5459
April	1st to 10th	Night	31% 6% 13% 22% 19% 9%	2100
	11th to 20th	Night	26% 6% 12% 25% 20% 12%	2079
	21st to end	Night	22% 5% 13% 27% 26% 7%	2100
May	1st to 10th	Night	20% 4 9% 20% 29% 18%	5499
	11th to 20th	Night	13% 2 6% 20% 35% 24%	4700
	21st to end	Night	13% 3 6% 27% 36% 14%	5182
June	1st to 10th	Night	18% 6% 11% 25% 27% 13%	1680
	11th to 20th	Night	9% 3 8% 18% 31% 30%	1680
	21st to end	Night	9% 2 4 13% 31% 41%	1680
July	1st to 10th	Night	4 1 1 8% 24% 62%	4700
	11th to 20th	Night	13% 1 1 4 13% 68%	4692
	21st to end	Night	6% 1 3 15% 24% 50%	5655
August	1st to 10th	Night	10% 1 1 6% 23% 59%	4169
	11th to 20th	Night	8% 2 2 16% 35% 39%	4380
	21st to end	Night	11% 1 1 10% 40% 36%	5092
September	1st to 10th	Night	6% 2 2 8% 27% 54%	2100
	11th to 20th	Night	12% 3 6% 17% 36% 27%	2100
	21st to end	Night	10% 2 5% 17% 30% 36%	2352
October	1st to 10th	Night	13% 3 3 11% 18% 53%	3920
	11th to 20th	Night	14% 3 7% 24% 30% 23%	3897
	21st to end	Night	21% 3 5% 23% 29% 19%	4253
November	1st to 10th	Night	28% 6% 10% 24% 17% 15%	2605
	11th to 20th	Night	31% 7% 13% 22% 18% 9%	2760
	21st to end	Night	30% 5% 8% 22% 22% 13%	2940
December	1st to 10th	Night	25% 3 8% 24% 23% 16%	4700
	11th to 20th	Night	55% 4 9% 16% 13% 3	5316
	21st to end	Night	55% 6% 10% 14% 11% 3	7106

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	41% 8% 15% 20% 14% 1	220
	11th to 20th	Day	21% 8% 18% 28% 16% 7%	383
	21st to end	Day	20% 5% 20% 25% 23% 7%	473
February	1st to 10th	Day	24% 9% 18% 26% 18% 6%	430
	11th to 20th	Day	23% 13% 22% 24% 14% 4	461
	21st to end	Day	17% 11% 25% 29% 15% 3	446
March	1st to 10th	Day	24% 17% 25% 20% 12% 2	540
	11th to 20th	Day	24% 9% 21% 23% 17% 5%	540
	21st to end	Day	21% 14% 22% 26% 14% 3	594
April	1st to 10th	Day	17% 13% 24% 24% 17% 6%	540
	11th to 20th	Day	15% 11% 23% 25% 19% 6%	532
	21st to end	Day	7% 11% 21% 31% 23% 7%	540
May	1st to 10th	Day	8% 8% 32% 24% 21% 7%	543
	11th to 20th	Day	8% 10% 20% 26% 25% 11%	568
	21st to end	Day	4 7% 18% 28% 30% 12%	617
June	1st to 10th	Day	4 6% 18% 30% 32% 10%	570
	11th to 20th	Day	3 6% 21% 32% 30% 8%	570
	21st to end	Day	2 4 15% 34% 32% 13%	570
July	1st to 10th	Day	1 2 12% 37% 37% 12%	566
	11th to 20th	Day	2 1 9% 34% 41% 13%	564
	21st to end	Day	1 8% 35% 42% 14%	619
August	1st to 10th	Day	1 1 10% 31% 40% 17%	567
	11th to 20th	Day	1 2 10% 29% 41% 18%	557
	21st to end	Day	2 1 10% 29% 43% 15%	627
September	1st to 10th	Day	2 4 12% 28% 40% 13%	570
	11th to 20th	Day	5% 4 18% 26% 32% 15%	570
	21st to end	Day	4 4 18% 33% 28% 11%	563
October	1st to 10th	Day	5% 7% 21% 24% 29% 14%	530
	11th to 20th	Day	8% 6% 19% 24% 30% 14%	530
	21st to end	Day	12% 7% 19% 27% 25% 10%	583
November	1st to 10th	Day	16% 7% 17% 22% 27% 11%	390
	11th to 20th	Day	18% 5% 17% 29% 21% 10%	313
	21st to end	Day	13% 5% 18% 28% 26% 9%	220
December	1st to 10th	Day	20% 5% 19% 24% 18% 14%	220
	11th to 20th	Day	29% 4 17% 25% 17% 8%	220
	21st to end	Day	26% 10% 18% 23% 20% 3	242
January	1st to 10th	Night	23% 5% 17% 34% 19% 2	840
	11th to 20th	Night	20% 5% 14% 39% 21% 2	840
	21st to end	Night	19% 3 19% 36% 21% 2	924
February	1st to 10th	Night	20% 4 17% 39% 18% 2	840
	11th to 20th	Night	19% 7% 20% 33% 19% 2	824
	21st to end	Night	18% 5% 24% 38% 13% 1	692
March	1st to 10th	Night	21% 9% 21% 31% 15% 2	840
	11th to 20th	Night	20% 7% 19% 30% 23% 2	840
	21st to end	Night	19% 8% 22% 34% 15% 1	924
April	1st to 10th	Night	12% 7% 27% 34% 18% 1	840
	11th to 20th	Night	12% 7% 24% 34% 21% 3	831
	21st to end	Night	9% 6% 21% 38% 23% 3	840
May	1st to 10th	Night	8% 6% 28% 33% 24% 1	693
	11th to 20th	Night	5% 5% 23% 39% 27% 2	414
	21st to end	Night	6% 7% 18% 41% 27% 1	455
June	1st to 10th	Night	6% 3 18% 45% 26% 1	420
	11th to 20th	Night	1 5% 22% 47% 24% 1	420
	21st to end	Night	3 2 16% 46% 30% 2	420
July	1st to 10th	Night	1 1 12% 50% 34% 2	410
	11th to 20th	Night	1 13% 51% 33% 2	408
	21st to end	Night	1 7% 41% 47% 4	678
August	1st to 10th	Night	2 1 8% 38% 48% 3	627
	11th to 20th	Night	1 1 8% 43% 43% 4	718
	21st to end	Night	1 1 6% 39% 49% 3	924
September	1st to 10th	Night	2 2 10% 38% 45% 4	840
	11th to 20th	Night	4 2 11% 39% 38% 7%	840
	21st to end	Night	4 3 14% 37% 35% 8%	832
October	1st to 10th	Night	6% 4 17% 35% 33% 5%	800
	11th to 20th	Night	7% 3 15% 35% 35% 5%	800
	21st to end	Night	9% 4 14% 36% 29% 7%	880
November	1st to 10th	Night	14% 6% 14% 31% 31% 4	820
	11th to 20th	Night	15% 2 18% 39% 23% 2	840
	21st to end	Night	14% 4 17% 40% 22% 3	840
December	1st to 10th	Night	20% 4 15% 35% 23% 4	840
	11th to 20th	Night	29% 3 15% 30% 20% 3	840
	21st to end	Night	27% 6% 19% 32% 16% 1	924

Page generated at 2026-09-26 01:18:40. Version ac07

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