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 2024-11-12.

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% 3 8% 5% 4 4 4 6% 7% 38%	101541
	Night	13% 9% 4 8% 4 4 4 3 5% 6% 39%	97727
Transparency	Day	44% 5% 12% 24% 13% 1	105068
	Night	45% 5% 11% 23% 15% 2	102340
Seeing	Day	16% 10% 29% 25% 14% 5%	15913
	Night	17% 10% 30% 31% 12% 1	25756

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% 12% 10% 15% 6% 4 4 2 4 4 28%	2527
	11th to 20th	Day	11% 12% 4 15% 5% 5% 5% 9% 7% 8% 20%	2530
	21st to end	Day	16% 19% 9% 11% 5% 3 3 2 5% 5% 21%	2957
February	1st to 10th	Day	11% 13% 5% 10% 5% 5% 4 4 5% 6% 32%	1710
	11th to 20th	Day	13% 11% 3 7% 5% 4 5% 4 5% 6% 36%	1775
	21st to end	Day	12% 14% 4 10% 6% 5% 4 3 5% 6% 33%	1570
March	1st to 10th	Day	13% 9% 3 6% 4 3 4 3 5% 7% 43%	3120
	11th to 20th	Day	11% 7% 2 9% 4 4 4 3 6% 7% 44%	3401
	21st to end	Day	21% 13% 4 9% 5% 5% 4 3 4 5% 26%	4093
April	1st to 10th	Day	18% 12% 4 7% 5% 4 4 3 5% 6% 31%	2280
	11th to 20th	Day	18% 10% 3 7% 5% 4 4 4 5% 6% 34%	2254
	21st to end	Day	19% 10% 3 9% 5% 4 4 3 5% 6% 33%	2320
May	1st to 10th	Day	16% 8% 3 7% 5% 4 4 4 6% 7% 36%	4237
	11th to 20th	Day	13% 6% 2 7% 5% 4 4 4 5% 7% 43%	4399
	21st to end	Day	12% 7% 2 7% 5% 5% 5% 4 7% 8% 38%	4824
June	1st to 10th	Day	11% 5% 1 6% 5% 4 5% 5% 6% 9% 44%	2660
	11th to 20th	Day	11% 5% 2 6% 5% 4 4 5% 7% 9% 42%	2660
	21st to end	Day	11% 6% 3 7% 5% 5% 5% 5% 7% 8% 38%	2660
July	1st to 10th	Day	9% 8% 3 9% 5% 5% 6% 5% 8% 9% 34%	4440
	11th to 20th	Day	4 4 2 5% 4 5% 5% 4 6% 10% 50%	4440
	21st to end	Day	8% 7% 3 7% 5% 5% 5% 4 6% 9% 40%	4813
August	1st to 10th	Day	9% 5% 2 7% 5% 5% 6% 5% 7% 8% 40%	4304
	11th to 20th	Day	10% 5% 2 6% 4 5% 5% 4 6% 7% 46%	3829
	21st to end	Day	9% 6% 3 6% 4 4 4 4 6% 9% 46%	4180
September	1st to 10th	Day	12% 5% 3 6% 5% 4 5% 3 6% 7% 45%	2280
	11th to 20th	Day	12% 5% 2 5% 3 3 3 4 6% 7% 51%	2231
	21st to end	Day	11% 7% 3 7% 4 4 4 3 6% 6% 45%	2090
October	1st to 10th	Day	12% 7% 2 6% 4 3 4 3 4 6% 48%	1921
	11th to 20th	Day	18% 9% 3 8% 4 3 4 3 5% 6% 37%	1900
	21st to end	Day	17% 11% 3 6% 4 4 4 2 5% 6% 40%	1933
November	1st to 10th	Day	12% 7% 3 7% 4 5% 4 4 5% 6% 43%	1762
	11th to 20th	Day	13% 13% 3 8% 5% 5% 4 3 5% 6% 34%	1700
	21st to end	Day	14% 12% 4 8% 4 4 3 3 4 6% 37%	1520
December	1st to 10th	Day	14% 14% 4 9% 6% 4 4 4 4 6% 32%	1520
	11th to 20th	Day	13% 13% 5% 9% 7% 4 4 3 6% 7% 29%	1918
	21st to end	Day	20% 22% 9% 10% 4 4 4 4 4 5% 15%	2783
January	1st to 10th	Night	12% 13% 7% 12% 6% 4 4 3 4 5% 31%	4428
	11th to 20th	Night	11% 15% 7% 14% 7% 4 4 5% 7% 5% 21%	4440
	21st to end	Night	16% 19% 7% 11% 4 5% 4 3 4 4 22%	4696
February	1st to 10th	Night	11% 14% 4 9% 5% 6% 4 3 5% 5% 33%	2470
	11th to 20th	Night	11% 11% 3 8% 6% 4 4 3 5% 6% 39%	2292
	21st to end	Night	16% 12% 4 8% 4 3 4 3 5% 6% 35%	1884
March	1st to 10th	Night	17% 10% 3 6% 4 4 4 3 4 5% 41%	3733
	11th to 20th	Night	9% 6% 2 7% 4 4 4 4 6% 7% 47%	3589
	21st to end	Night	24% 12% 4 11% 5% 4 4 3 3 5% 26%	3536
April	1st to 10th	Night	17% 9% 3 7% 4 3 4 3 6% 6% 37%	1900
	11th to 20th	Night	19% 9% 3 7% 4 3 4 3 5% 6% 37%	1875
	21st to end	Night	17% 7% 3 7% 4 5% 3 4 5% 8% 37%	1858
May	1st to 10th	Night	17% 7% 3 8% 5% 4 4 4 6% 7% 35%	2658
	11th to 20th	Night	13% 7% 3 6% 5% 5% 4 4 6% 7% 41%	2506
	21st to end	Night	9% 7% 2 6% 5% 4 4 4 6% 9% 44%	2743
June	1st to 10th	Night	8% 4 2 5% 5% 4 5% 4 8% 9% 45%	1520
	11th to 20th	Night	12% 6% 2 5% 4 4 4 3 6% 11% 44%	1520
	21st to end	Night	8% 6% 3 6% 4 4 3 4 5% 7% 49%	1520
July	1st to 10th	Night	14% 6% 3 6% 4 4 5% 3 6% 8% 41%	2530
	11th to 20th	Night	4 4 1 4 4 4 5% 4 5% 8% 56%	2530
	21st to end	Night	6% 5% 2 6% 4 5% 5% 4 7% 9% 48%	2750
August	1st to 10th	Night	8% 5% 2 5% 4 4 5% 4 6% 7% 51%	2633
	11th to 20th	Night	9% 5% 3 6% 3 4 4 3 5% 9% 50%	3003
	21st to end	Night	9% 5% 2 6% 4 4 4 3 5% 7% 50%	3476
September	1st to 10th	Night	8% 4 2 5% 4 3 4 3 4 8% 55%	1900
	11th to 20th	Night	10% 5% 2 4 3 4 4 4 5% 7% 52%	1928
	21st to end	Night	9% 6% 2 5% 3 4 4 4 5% 7% 51%	2090
October	1st to 10th	Night	11% 6% 3 5% 4 3 4 3 5% 6% 50%	2256
	11th to 20th	Night	15% 8% 2 6% 4 3 3 3 4 6% 45%	2280
	21st to end	Night	18% 7% 4 6% 4 4 5% 3 5% 7% 37%	2665
November	1st to 10th	Night	12% 8% 4 6% 3 4 3 3 4 5% 48%	2536
	11th to 20th	Night	14% 11% 4 9% 6% 4 4 3 5% 6% 36%	2499
	21st to end	Night	17% 10% 4 6% 4 4 3 3 5% 6% 39%	2660
December	1st to 10th	Night	14% 12% 4 9% 6% 5% 5% 4 5% 6% 31%	2660
	11th to 20th	Night	15% 13% 4 10% 6% 5% 5% 3 5% 5% 30%	3279
	21st to end	Night	20% 17% 5% 11% 5% 5% 4 3 4 5% 19%	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	61% 4 12% 16% 7%	2528
	11th to 20th	Day	58% 5% 15% 14% 8%	2530
	21st to end	Day	66% 4 10% 15% 5%	2957
February	1st to 10th	Day	53% 4 12% 19% 12% 1	1710
	11th to 20th	Day	49% 4 12% 23% 10% 2	1784
	21st to end	Day	54% 4 9% 20% 11% 2	1570
March	1st to 10th	Day	41% 5% 11% 28% 11% 3	3120
	11th to 20th	Day	39% 5% 11% 31% 13% 1	3401
	21st to end	Day	60% 4 12% 16% 7% 1	4093
April	1st to 10th	Day	54% 5% 10% 20% 11% 1	2280
	11th to 20th	Day	50% 6% 9% 21% 12% 2	2254
	21st to end	Day	51% 6% 10% 18% 13% 2	2320
May	1st to 10th	Day	45% 6% 11% 22% 15% 1	4275
	11th to 20th	Day	40% 7% 10% 31% 12%	4403
	21st to end	Day	40% 8% 11% 23% 15% 3	4837
June	1st to 10th	Day	35% 7% 15% 26% 16% 1	2660
	11th to 20th	Day	36% 7% 14% 23% 18% 2	2660
	21st to end	Day	42% 7% 13% 24% 13% 2	2660
July	1st to 10th	Day	43% 7% 15% 26% 9% 1	4371
	11th to 20th	Day	28% 7% 16% 32% 17% 1	4365
	21st to end	Day	39% 7% 15% 21% 17% 2	4662
August	1st to 10th	Day	39% 6% 15% 27% 13% 1	4289
	11th to 20th	Day	36% 5% 14% 31% 14% 1	3867
	21st to end	Day	34% 4 14% 30% 16% 1	4179
September	1st to 10th	Day	38% 7% 10% 26% 19% 2	2280
	11th to 20th	Day	32% 5% 12% 32% 17% 2	2231
	21st to end	Day	39% 5% 9% 29% 17% 1	2090
October	1st to 10th	Day	24% 4 6% 39% 26% 1	3194
	11th to 20th	Day	35% 3 8% 27% 24% 2	3140
	21st to end	Day	42% 3 10% 28% 14% 3	3158
November	1st to 10th	Day	42% 5% 14% 25% 13% 2	1762
	11th to 20th	Day	50% 5% 14% 20% 10% 1	1700
	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	56% 5% 10% 19% 9% 1	4428
	11th to 20th	Night	62% 4 11% 14% 9%	4440
	21st to end	Night	66% 4 8% 16% 5% 1	4696
February	1st to 10th	Night	53% 4 10% 19% 12% 2	2470
	11th to 20th	Night	47% 4 11% 22% 14% 1	2293
	21st to end	Night	50% 4 11% 21% 11% 3	1884
March	1st to 10th	Night	46% 5% 11% 23% 10% 5%	3733
	11th to 20th	Night	35% 4 11% 31% 17% 2	3589
	21st to end	Night	61% 4 7% 17% 9% 1	3536
April	1st to 10th	Night	46% 6% 10% 23% 13% 2	1900
	11th to 20th	Night	48% 4 6% 20% 18% 3	1875
	21st to end	Night	45% 6% 12% 23% 12% 2	1858
May	1st to 10th	Night	45% 7% 12% 16% 19% 1	2685
	11th to 20th	Night	41% 7% 12% 23% 17% 1	2507
	21st to end	Night	34% 8% 14% 21% 20% 3	2751
June	1st to 10th	Night	32% 7% 14% 26% 20% 1	1520
	11th to 20th	Night	34% 5% 10% 26% 23% 3	1520
	21st to end	Night	33% 6% 16% 22% 19% 3	1520
July	1st to 10th	Night	41% 5% 15% 24% 12% 3	2490
	11th to 20th	Night	25% 7% 14% 34% 18% 2	2482
	21st to end	Night	31% 7% 17% 21% 20% 4	2662
August	1st to 10th	Night	32% 5% 14% 29% 20% 1	2624
	11th to 20th	Night	32% 5% 13% 32% 18% 1	3031
	21st to end	Night	33% 5% 12% 28% 18% 3	3476
September	1st to 10th	Night	29% 5% 12% 27% 25% 2	1900
	11th to 20th	Night	31% 5% 11% 32% 19% 2	1928
	21st to end	Night	34% 4 10% 30% 20% 1	2090
October	1st to 10th	Night	25% 3 6% 37% 28% 1	3763
	11th to 20th	Night	33% 3 10% 27% 25% 2	3779
	21st to end	Night	44% 4 9% 27% 15% 2	4390
November	1st to 10th	Night	40% 4 10% 26% 18% 2	2536
	11th to 20th	Night	50% 5% 12% 21% 11% 1	2499
	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	20% 15% 40% 19% 5% 1	270
	21st to end	Day	22% 14% 34% 24% 6%	297
February	1st to 10th	Day	14% 20% 40% 18% 6% 1	270
	11th to 20th	Day	23% 20% 33% 21% 4	270
	21st to end	Day	23% 18% 38% 19% 2	225
March	1st to 10th	Day	17% 19% 42% 18% 4	270
	11th to 20th	Day	20% 21% 36% 15% 6% 2	270
	21st to end	Day	28% 13% 32% 19% 6% 2	460
April	1st to 10th	Day	25% 15% 33% 22% 5%	460
	11th to 20th	Day	26% 16% 26% 19% 11% 2	452
	21st to end	Day	24% 11% 30% 24% 9% 2	460
May	1st to 10th	Day	22% 9% 31% 27% 9% 2	553
	11th to 20th	Day	21% 9% 28% 25% 12% 4	675
	21st to end	Day	17% 9% 26% 24% 17% 7%	734
June	1st to 10th	Day	9% 7% 30% 29% 20% 5%	680
	11th to 20th	Day	12% 6% 30% 30% 15% 6%	680
	21st to end	Day	14% 8% 27% 30% 16% 5%	680
July	1st to 10th	Day	8% 3 19% 29% 27% 14%	671
	11th to 20th	Day	9% 5% 25% 28% 23% 10%	668
	21st to end	Day	8% 4 25% 32% 22% 8%	739
August	1st to 10th	Day	7% 3 19% 35% 26% 10%	676
	11th to 20th	Day	12% 5% 20% 27% 23% 14%	543
	21st to end	Day	12% 6% 18% 30% 25% 9%	539
September	1st to 10th	Day	13% 6% 23% 29% 20% 9%	490
	11th to 20th	Day	12% 3 20% 31% 24% 11%	490
	21st to end	Day	14% 10% 26% 27% 18% 5%	490
October	1st to 10th	Day	15% 11% 28% 28% 15% 3	321
	11th to 20th	Day	23% 17% 32% 19% 9%	300
	21st to end	Day	26% 18% 28% 22% 6% 1	330
November	1st to 10th	Day	18% 14% 38% 20% 8% 2	300
	11th to 20th	Day	19% 17% 36% 19% 8% 1	273
	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	20% 12% 37% 25% 5% 1	950
	21st to end	Night	20% 12% 35% 27% 5%	1045
February	1st to 10th	Night	18% 11% 39% 24% 7%	950
	11th to 20th	Night	17% 15% 37% 26% 5%	817
	21st to end	Night	23% 14% 38% 21% 4	628
March	1st to 10th	Night	22% 13% 36% 24% 5% 1	760
	11th to 20th	Night	17% 11% 35% 29% 8%	640
	21st to end	Night	24% 10% 32% 27% 6% 1	627
April	1st to 10th	Night	20% 15% 36% 24% 5%	570
	11th to 20th	Night	24% 12% 29% 27% 7%	563
	21st to end	Night	20% 9% 32% 28% 9% 1	570
May	1st to 10th	Night	18% 8% 34% 30% 9% 1	570
	11th to 20th	Night	19% 5% 30% 35% 11% 1	561
	21st to end	Night	12% 6% 27% 38% 16% 1	617
June	1st to 10th	Night	9% 5% 24% 45% 15% 1	570
	11th to 20th	Night	15% 3 29% 39% 14%	570
	21st to end	Night	10% 6% 25% 43% 16% 1	570
July	1st to 10th	Night	9% 3 12% 39% 32% 4	555
	11th to 20th	Night	8% 3 20% 42% 24% 3	552
	21st to end	Night	7% 2 18% 46% 26% 2	624
August	1st to 10th	Night	5% 3 15% 46% 28% 3	567
	11th to 20th	Night	10% 3 13% 38% 30% 6%	564
	21st to end	Night	11% 1 15% 44% 27% 3	627
September	1st to 10th	Night	9% 3 22% 37% 24% 5%	570
	11th to 20th	Night	12% 3 20% 34% 26% 4	598
	21st to end	Night	12% 8% 23% 37% 19% 2	760
October	1st to 10th	Night	15% 7% 26% 34% 17% 1	760
	11th to 20th	Night	19% 12% 28% 31% 9%	760
	21st to end	Night	22% 12% 32% 27% 7% 1	836
November	1st to 10th	Night	16% 11% 37% 26% 10% 1	780
	11th to 20th	Night	19% 14% 37% 24% 5% 1	780
	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

Page generated at 2024-11-08 21:45:39. Version ac07

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