Meadowlark Ridge Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Meadowlark Ridge Observatory clear sky chart from 2005-11-06 to 2024-01-14.

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% 9% 4 7% 6% 3 5% 5% 5% 7% 37%	74788
	Night	13% 9% 4 7% 5% 3 4 4 5% 7% 39%	74994
Transparency	Day	46% 6% 13% 22% 12% 1	74488
	Night	45% 5% 12% 22% 14% 2	74814
Seeing	Day	17% 10% 28% 25% 15% 5%	14711
	Night	17% 9% 30% 30% 12% 1	24703

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% 9% 6% 9% 6% 3 5% 5% 5% 7% 32%	1517
	11th to 20th	Day	12% 14% 7% 12% 7% 3 4 5% 4 7% 23%	1464
	21st to end	Day	13% 13% 7% 13% 8% 3 5% 4 5% 6% 24%	1688
February	1st to 10th	Day	12% 13% 5% 9% 6% 3 5% 6% 5% 6% 30%	1620
	11th to 20th	Day	14% 11% 4 6% 6% 3 5% 5% 5% 6% 34%	1679
	21st to end	Day	13% 14% 5% 10% 7% 3 4 3 5% 5% 32%	1480
March	1st to 10th	Day	14% 11% 5% 8% 5% 3 5% 5% 5% 7% 33%	1800
	11th to 20th	Day	13% 8% 3 8% 6% 2 4 3 5% 7% 40%	1929
	21st to end	Day	19% 11% 4 7% 6% 4 5% 5% 4 6% 30%	2332
April	1st to 10th	Day	18% 11% 4 7% 6% 3 5% 4 5% 6% 31%	2160
	11th to 20th	Day	18% 9% 3 7% 6% 3 4 5% 5% 6% 34%	2134
	21st to end	Day	19% 10% 3 8% 6% 3 4 4 5% 6% 32%	2197
May	1st to 10th	Day	17% 9% 3 7% 7% 4 4 5% 7% 8% 30%	2425
	11th to 20th	Day	18% 7% 3 7% 7% 3 4 5% 5% 7% 34%	2479
	21st to end	Day	14% 8% 2 6% 6% 3 6% 5% 6% 8% 36%	2725
June	1st to 10th	Day	11% 4 2 5% 6% 3 5% 6% 6% 9% 44%	2520
	11th to 20th	Day	12% 5% 2 5% 5% 3 5% 6% 7% 9% 43%	2520
	21st to end	Day	11% 6% 3 6% 6% 3 6% 6% 7% 9% 38%	2520
July	1st to 10th	Day	6% 4 2 5% 4 3 5% 5% 8% 9% 47%	2520
	11th to 20th	Day	6% 5% 2 6% 5% 4 6% 6% 7% 9% 44%	2520
	21st to end	Day	7% 5% 2 5% 6% 3 5% 6% 6% 10% 45%	2743
August	1st to 10th	Day	6% 5% 2 5% 6% 4 6% 7% 7% 11% 41%	2444
	11th to 20th	Day	10% 6% 2 5% 6% 4 5% 5% 5% 7% 44%	2186
	21st to end	Day	10% 5% 3 5% 5% 2 4 5% 6% 8% 47%	2376
September	1st to 10th	Day	13% 5% 3 5% 6% 3 4 5% 6% 7% 43%	2160
	11th to 20th	Day	13% 5% 2 4 4 2 3 4 6% 7% 51%	2114
	21st to end	Day	11% 7% 3 6% 5% 3 5% 4 6% 6% 44%	1980
October	1st to 10th	Day	13% 7% 3 6% 5% 2 4 4 4 6% 47%	1820
	11th to 20th	Day	19% 8% 3 7% 5% 3 3 4 5% 6% 36%	1800
	21st to end	Day	18% 10% 3 5% 5% 3 4 3 4 6% 39%	1832
November	1st to 10th	Day	12% 6% 3 6% 5% 3 5% 4 5% 6% 44%	1672
	11th to 20th	Day	14% 12% 4 7% 6% 4 4 4 5% 6% 34%	1691
	21st to end	Day	15% 11% 5% 8% 5% 2 4 4 4 6% 37%	1520
December	1st to 10th	Day	14% 14% 4 8% 6% 3 5% 4 4 6% 32%	1520
	11th to 20th	Day	13% 12% 6% 8% 8% 3 4 3 6% 7% 29%	1918
	21st to end	Day	20% 21% 9% 9% 5% 3 4 5% 4 5% 15%	2783
January	1st to 10th	Night	12% 12% 5% 8% 7% 3 4 3 4 5% 36%	2648
	11th to 20th	Night	14% 14% 6% 11% 8% 3 4 4 4 5% 28%	2569
	21st to end	Night	13% 13% 6% 11% 6% 4 5% 5% 5% 6% 26%	2668
February	1st to 10th	Night	12% 14% 5% 8% 6% 4 5% 4 5% 5% 32%	2340
	11th to 20th	Night	12% 10% 3 8% 6% 3 5% 4 5% 5% 38%	2168
	21st to end	Night	17% 11% 4 7% 5% 3 4 4 5% 6% 34%	1776
March	1st to 10th	Night	17% 10% 4 7% 5% 4 4 5% 4 7% 35%	2160
	11th to 20th	Night	12% 8% 3 5% 5% 4 5% 4 6% 8% 41%	2047
	21st to end	Night	20% 9% 4 8% 6% 3 5% 4 4 7% 30%	2022
April	1st to 10th	Night	17% 8% 4 6% 6% 3 4 5% 6% 6% 37%	1800
	11th to 20th	Night	20% 9% 3 6% 5% 3 4 3 5% 6% 36%	1775
	21st to end	Night	17% 7% 3 6% 5% 3 5% 5% 5% 8% 37%	1761
May	1st to 10th	Night	15% 7% 4 7% 6% 3 4 5% 7% 8% 34%	1530
	11th to 20th	Night	16% 8% 4 6% 6% 4 4 4 5% 7% 37%	1416
	21st to end	Night	11% 5% 2 6% 5% 3 4 5% 5% 10% 43%	1551
June	1st to 10th	Night	9% 4 2 4 6% 3 5% 5% 7% 10% 46%	1440
	11th to 20th	Night	12% 6% 2 5% 4 3 4 5% 5% 10% 45%	1440
	21st to end	Night	9% 5% 3 5% 4 3 4 4 5% 8% 50%	1440
July	1st to 10th	Night	6% 4 2 3 3 3 4 5% 6% 10% 54%	1440
	11th to 20th	Night	6% 4 2 3 5% 3 4 4 6% 9% 54%	1440
	21st to end	Night	6% 4 1 3 4 3 5% 5% 6% 10% 52%	1575
August	1st to 10th	Night	4 4 2 5% 6% 3 6% 5% 6% 9% 51%	1492
	11th to 20th	Night	8% 4 3 5% 4 3 3 4 5% 9% 52%	1715
	21st to end	Night	8% 4 2 4 4 3 4 4 4 6% 54%	1980
September	1st to 10th	Night	9% 4 2 4 5% 3 4 4 4 8% 54%	1800
	11th to 20th	Night	11% 5% 1 3 4 3 3 4 4 7% 54%	1826
	21st to end	Night	10% 6% 2 5% 4 3 4 5% 5% 7% 50%	1980
October	1st to 10th	Night	11% 6% 3 5% 4 3 4 4 5% 6% 49%	2137
	11th to 20th	Night	15% 8% 3 6% 5% 3 3 4 4 6% 44%	2160
	21st to end	Night	19% 7% 4 5% 5% 3 4 4 5% 7% 37%	2524
November	1st to 10th	Night	11% 7% 4 5% 5% 3 3 4 4 6% 49%	2406
	11th to 20th	Night	14% 10% 4 8% 7% 3 5% 4 4 6% 36%	2485
	21st to end	Night	17% 9% 4 5% 4 3 4 3 5% 6% 39%	2660
December	1st to 10th	Night	14% 12% 4 8% 6% 4 6% 5% 4 6% 31%	2660
	11th to 20th	Night	15% 12% 4 9% 7% 3 5% 4 4 5% 30%	3279
	21st to end	Night	21% 16% 6% 10% 6% 4 4 4 4 5% 20%	4884

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	52% 5% 14% 17% 11%	1518
	11th to 20th	Day	61% 4 13% 15% 7%	1464
	21st to end	Day	62% 5% 11% 14% 8% 1	1688
February	1st to 10th	Day	55% 4 12% 19% 9% 1	1620
	11th to 20th	Day	50% 4 12% 21% 10% 2	1688
	21st to end	Day	55% 4 9% 19% 11% 2	1480
March	1st to 10th	Day	51% 5% 13% 21% 8% 1	1800
	11th to 20th	Day	45% 5% 12% 23% 14% 1	1929
	21st to end	Day	56% 4 11% 20% 8% 1	2332
April	1st to 10th	Day	54% 5% 10% 20% 11% 1	2160
	11th to 20th	Day	50% 5% 10% 21% 12% 2	2134
	21st to end	Day	52% 6% 10% 18% 12% 2	2197
May	1st to 10th	Day	51% 5% 14% 22% 7%	2425
	11th to 20th	Day	49% 6% 11% 22% 12%	2483
	21st to end	Day	46% 7% 11% 21% 14% 1	2725
June	1st to 10th	Day	35% 8% 15% 26% 15% 1	2520
	11th to 20th	Day	36% 7% 14% 23% 18% 2	2520
	21st to end	Day	42% 7% 14% 24% 13% 1	2520
July	1st to 10th	Day	32% 7% 16% 28% 14% 2	2451
	11th to 20th	Day	33% 8% 16% 25% 16% 2	2445
	21st to end	Day	34% 6% 16% 28% 14% 3	2591
August	1st to 10th	Day	34% 8% 16% 29% 12% 1	2429
	11th to 20th	Day	39% 6% 14% 26% 14% 1	2186
	21st to end	Day	34% 6% 12% 28% 19% 3	2376
September	1st to 10th	Day	39% 7% 9% 25% 18% 2	2160
	11th to 20th	Day	32% 5% 13% 32% 16% 2	2114
	21st to end	Day	40% 5% 9% 29% 16% 1	1980
October	1st to 10th	Day	39% 6% 9% 30% 15% 1	1820
	11th to 20th	Day	49% 4 11% 23% 12% 1	1800
	21st to end	Day	48% 4 12% 23% 13% 1	1832
November	1st to 10th	Day	41% 5% 13% 25% 14% 2	1672
	11th to 20th	Day	50% 5% 14% 20% 10% 1	1691
	21st to end	Day	49% 4 17% 21% 8% 1	1520
December	1st to 10th	Day	54% 5% 13% 18% 8% 1	1520
	11th to 20th	Day	55% 3 16% 15% 9% 2	1915
	21st to end	Day	72% 5% 9% 9% 5%	2783
January	1st to 10th	Night	51% 4 11% 20% 13% 1	2648
	11th to 20th	Night	60% 4 13% 14% 8% 1	2569
	21st to end	Night	59% 5% 10% 15% 9% 1	2668
February	1st to 10th	Night	55% 4 10% 18% 12% 1	2340
	11th to 20th	Night	48% 4 12% 21% 14% 1	2169
	21st to end	Night	51% 4 11% 20% 11% 3	1776
March	1st to 10th	Night	51% 5% 13% 20% 10% 2	2160
	11th to 20th	Night	42% 4 13% 22% 17% 2	2047
	21st to end	Night	56% 4 9% 20% 10% 2	2022
April	1st to 10th	Night	46% 6% 11% 22% 14% 2	1800
	11th to 20th	Night	49% 4 6% 20% 17% 4	1775
	21st to end	Night	45% 6% 12% 22% 12% 2	1761
May	1st to 10th	Night	46% 7% 13% 20% 13%	1530
	11th to 20th	Night	47% 5% 11% 22% 14% 1	1417
	21st to end	Night	37% 6% 15% 23% 17% 2	1552
June	1st to 10th	Night	32% 7% 14% 26% 21% 1	1440
	11th to 20th	Night	35% 6% 9% 25% 23% 2	1440
	21st to end	Night	32% 6% 17% 23% 18% 3	1440
July	1st to 10th	Night	26% 5% 15% 33% 18% 3	1400
	11th to 20th	Night	27% 6% 12% 31% 21% 3	1392
	21st to end	Night	25% 6% 19% 28% 18% 4	1487
August	1st to 10th	Night	30% 6% 15% 30% 17% 3	1483
	11th to 20th	Night	30% 5% 15% 30% 19% 1	1715
	21st to end	Night	30% 6% 11% 28% 20% 4	1980
September	1st to 10th	Night	30% 5% 13% 26% 24% 2	1800
	11th to 20th	Night	30% 5% 11% 32% 19% 2	1826
	21st to end	Night	34% 4 11% 30% 20% 1	1980
October	1st to 10th	Night	36% 5% 9% 29% 21% 2	2137
	11th to 20th	Night	42% 4 11% 24% 18% 1	2160
	21st to end	Night	48% 5% 10% 24% 12% 1	2524
November	1st to 10th	Night	39% 4 10% 26% 18% 3	2406
	11th to 20th	Night	50% 5% 12% 21% 11% 1	2485
	21st to end	Night	48% 4 14% 23% 11% 1	2660
December	1st to 10th	Night	55% 4 11% 21% 9% 1	2660
	11th to 20th	Night	57% 5% 12% 18% 8% 1	3281
	21st to end	Night	67% 5% 8% 15% 5%	4884

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	18% 14% 28% 28% 10% 2	270
	11th to 20th	Day	22% 14% 39% 18% 6% 1	249
	21st to end	Day	20% 13% 36% 23% 7%	264
February	1st to 10th	Day	15% 21% 43% 15% 5%	240
	11th to 20th	Day	25% 20% 31% 20% 3	240
	21st to end	Day	25% 20% 35% 18% 2	198
March	1st to 10th	Day	16% 21% 41% 17% 5%	240
	11th to 20th	Day	20% 20% 35% 16% 7% 3	240
	21st to end	Day	28% 13% 31% 19% 6% 2	418
April	1st to 10th	Day	24% 14% 33% 23% 5%	420
	11th to 20th	Day	26% 16% 26% 19% 11% 2	412
	21st to end	Day	24% 11% 30% 24% 10% 2	420
May	1st to 10th	Day	22% 9% 31% 27% 8% 2	508
	11th to 20th	Day	23% 9% 28% 25% 12% 4	625
	21st to end	Day	18% 8% 26% 23% 17% 8%	679
June	1st to 10th	Day	9% 6% 30% 29% 21% 6%	630
	11th to 20th	Day	13% 6% 29% 31% 15% 7%	630
	21st to end	Day	13% 8% 26% 31% 17% 5%	630
July	1st to 10th	Day	7% 2 18% 30% 28% 15%	621
	11th to 20th	Day	9% 5% 25% 28% 22% 10%	618
	21st to end	Day	8% 4 26% 32% 22% 8%	684
August	1st to 10th	Day	7% 3 18% 35% 28% 10%	626
	11th to 20th	Day	12% 5% 18% 27% 23% 15%	500
	21st to end	Day	12% 6% 19% 29% 25% 9%	495
September	1st to 10th	Day	14% 6% 22% 30% 20% 8%	450
	11th to 20th	Day	13% 4 21% 30% 22% 11%	450
	21st to end	Day	14% 11% 25% 26% 19% 5%	450
October	1st to 10th	Day	17% 10% 27% 28% 14% 4	290
	11th to 20th	Day	24% 18% 31% 18% 8%	270
	21st to end	Day	27% 17% 27% 22% 6% 1	297
November	1st to 10th	Day	16% 14% 39% 20% 9% 2	270
	11th to 20th	Day	19% 17% 37% 18% 8% 1	270
	21st to end	Day	23% 11% 41% 20% 5%	270
December	1st to 10th	Day	19% 18% 37% 17% 7% 2	270
	11th to 20th	Day	20% 13% 38% 21% 9%	270
	21st to end	Day	28% 14% 39% 17% 2	297
January	1st to 10th	Night	16% 15% 37% 25% 7% 1	950
	11th to 20th	Night	21% 12% 36% 26% 5% 1	918
	21st to end	Night	20% 12% 35% 27% 5%	990
February	1st to 10th	Night	19% 11% 39% 23% 6%	900
	11th to 20th	Night	18% 15% 37% 25% 5%	773
	21st to end	Night	23% 14% 37% 21% 4	592
March	1st to 10th	Night	22% 13% 35% 24% 6% 1	720
	11th to 20th	Night	18% 10% 34% 29% 9%	607
	21st to end	Night	24% 10% 31% 27% 7% 1	594
April	1st to 10th	Night	20% 15% 36% 24% 6%	540
	11th to 20th	Night	25% 11% 29% 27% 7%	533
	21st to end	Night	21% 9% 31% 28% 10% 1	540
May	1st to 10th	Night	18% 8% 34% 31% 9% 1	540
	11th to 20th	Night	20% 5% 30% 34% 11% 1	531
	21st to end	Night	13% 5% 27% 38% 16% 1	584
June	1st to 10th	Night	9% 5% 24% 45% 16% 1	540
	11th to 20th	Night	15% 3 27% 40% 15%	540
	21st to end	Night	10% 5% 24% 43% 17% 1	540
July	1st to 10th	Night	7% 3 12% 40% 34% 5%	525
	11th to 20th	Night	7% 3 20% 43% 23% 2	522
	21st to end	Night	7% 2 18% 46% 25% 2	591
August	1st to 10th	Night	5% 3 15% 46% 29% 3	537
	11th to 20th	Night	10% 3 13% 38% 31% 6%	534
	21st to end	Night	11% 1 15% 44% 27% 3	594
September	1st to 10th	Night	9% 3 22% 37% 23% 5%	540
	11th to 20th	Night	13% 3 21% 33% 26% 4	566
	21st to end	Night	13% 8% 23% 35% 19% 2	720
October	1st to 10th	Night	15% 7% 26% 33% 18% 1	720
	11th to 20th	Night	20% 12% 28% 31% 9%	720
	21st to end	Night	22% 11% 32% 27% 7% 1	792
November	1st to 10th	Night	15% 10% 37% 26% 10% 1	740
	11th to 20th	Night	19% 14% 36% 24% 5% 1	775
	21st to end	Night	21% 13% 34% 25% 7%	950
December	1st to 10th	Night	21% 12% 36% 25% 6% 1	950
	11th to 20th	Night	23% 12% 34% 25% 5% 1	950
	21st to end	Night	27% 14% 32% 24% 3	1045

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