MAS Eagle Lake Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the MAS Eagle Lake Observatory clear sky chart from 2005-11-06 to 2024-11-04.

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% 8% 3 8% 5% 4 5% 4 6% 7% 38%	102001
	Night	12% 9% 3 8% 5% 4 4 3 5% 6% 40%	97105
Transparency	Day	45% 4 13% 26% 12% 1	105632
	Night	44% 3 12% 26% 13% 2	101614
Seeing	Day	16% 9% 31% 27% 14% 3	16014
	Night	15% 8% 33% 32% 11% 1	25872

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	11% 17% 6% 14% 7% 5% 5% 4 4 6% 20%	2527
	11th to 20th	Day	5% 11% 5% 14% 8% 8% 9% 6% 7% 5% 21%	2628
	21st to end	Day	8% 18% 8% 14% 8% 6% 6% 3 5% 5% 21%	3135
February	1st to 10th	Day	8% 12% 4 10% 7% 6% 5% 5% 5% 6% 31%	1710
	11th to 20th	Day	8% 10% 4 10% 7% 5% 6% 5% 6% 6% 33%	1664
	21st to end	Day	10% 12% 3 9% 7% 5% 5% 4 6% 6% 33%	1441
March	1st to 10th	Day	12% 11% 4 8% 5% 4 4 3 5% 6% 39%	3426
	11th to 20th	Day	9% 9% 3 7% 5% 5% 4 3 5% 8% 40%	3480
	21st to end	Day	23% 11% 4 11% 7% 5% 4 3 4 6% 22%	3814
April	1st to 10th	Day	17% 9% 3 8% 5% 4 4 3 5% 7% 36%	2274
	11th to 20th	Day	19% 11% 4 7% 4 4 4 3 4 6% 33%	2299
	21st to end	Day	22% 12% 3 6% 5% 4 4 3 4 6% 32%	2470
May	1st to 10th	Day	17% 6% 2 6% 4 4 5% 4 6% 7% 39%	4192
	11th to 20th	Day	13% 6% 2 6% 4 4 4 4 5% 7% 46%	4399
	21st to end	Day	18% 7% 2 6% 5% 5% 5% 4 5% 8% 36%	4824
June	1st to 10th	Day	11% 5% 2 5% 4 4 4 4 6% 8% 47%	2660
	11th to 20th	Day	14% 6% 3 6% 5% 4 4 4 7% 8% 40%	2719
	21st to end	Day	10% 4 2 6% 5% 5% 6% 4 7% 9% 42%	2850
July	1st to 10th	Day	9% 6% 2 6% 4 5% 6% 5% 8% 11% 38%	4627
	11th to 20th	Day	5% 3 1 3 3 3 4 4 6% 9% 59%	4440
	21st to end	Day	5% 4 2 6% 4 5% 6% 4 7% 9% 48%	4666
August	1st to 10th	Day	12% 6% 2 6% 4 4 5% 4 7% 7% 42%	4104
	11th to 20th	Day	12% 5% 2 6% 4 4 5% 5% 7% 9% 41%	4041
	21st to end	Day	9% 6% 3 6% 4 4 4 3 5% 7% 50%	4377
September	1st to 10th	Day	11% 5% 1 6% 4 3 4 3 6% 7% 50%	2280
	11th to 20th	Day	12% 5% 2 6% 4 4 4 3 5% 7% 48%	2209
	21st to end	Day	15% 6% 2 5% 4 4 4 3 5% 7% 45%	2025
October	1st to 10th	Day	16% 7% 2 6% 5% 4 3 3 5% 5% 43%	1900
	11th to 20th	Day	14% 9% 2 6% 4 4 4 3 4 7% 43%	1900
	21st to end	Day	17% 10% 3 7% 4 3 4 3 4 6% 38%	2090
November	1st to 10th	Day	12% 10% 4 7% 5% 4 4 3 5% 7% 38%	1569
	11th to 20th	Day	10% 12% 6% 10% 5% 5% 4 3 6% 6% 32%	1520
	21st to end	Day	13% 10% 4 6% 5% 4 4 4 5% 9% 36%	1520
December	1st to 10th	Day	11% 12% 3 11% 8% 6% 6% 4 6% 6% 27%	1520
	11th to 20th	Day	10% 14% 5% 12% 5% 5% 4 4 5% 7% 29%	1918
	21st to end	Day	21% 14% 6% 17% 5% 3 3 2 4 5% 19%	2783
January	1st to 10th	Night	9% 15% 7% 17% 6% 4 3 3 4 5% 27%	4428
	11th to 20th	Night	7% 11% 5% 14% 8% 7% 8% 6% 8% 6% 21%	4340
	21st to end	Night	9% 18% 8% 12% 5% 5% 4 4 5% 4 27%	4532
February	1st to 10th	Night	6% 13% 5% 10% 6% 5% 5% 3 6% 7% 35%	2470
	11th to 20th	Night	7% 9% 3 8% 5% 5% 5% 4 6% 8% 40%	2403
	21st to end	Night	10% 9% 3 8% 6% 5% 5% 4 5% 7% 38%	2012
March	1st to 10th	Night	9% 8% 2 7% 4 4 4 3 4 7% 48%	3454
	11th to 20th	Night	9% 7% 2 7% 5% 5% 5% 4 5% 7% 43%	3480
	21st to end	Night	25% 12% 4 9% 4 3 2 2 3 5% 30%	3817
April	1st to 10th	Night	14% 11% 3 6% 4 4 5% 4 6% 6% 38%	1905
	11th to 20th	Night	20% 8% 3 8% 4 3 3 4 5% 6% 35%	1827
	21st to end	Night	19% 8% 3 7% 4 4 5% 3 5% 6% 36%	1710
May	1st to 10th	Night	15% 7% 2 6% 4 5% 4 4 5% 6% 43%	2711
	11th to 20th	Night	14% 5% 1 4 3 3 4 3 6% 8% 49%	2506
	21st to end	Night	14% 8% 2 5% 4 3 4 3 5% 7% 45%	2743
June	1st to 10th	Night	10% 4 1 5% 4 3 4 4 7% 8% 50%	1520
	11th to 20th	Night	8% 6% 2 5% 4 4 5% 4 7% 9% 46%	1454
	21st to end	Night	7% 4 1 4 3 4 4 3 7% 8% 56%	1330
July	1st to 10th	Night	10% 4 1 4 4 5% 5% 4 7% 10% 44%	2334
	11th to 20th	Night	3 3 1 3 3 3 4 4 5% 8% 62%	2530
	21st to end	Night	5% 3 2 5% 4 4 3 3 5% 8% 57%	2893
August	1st to 10th	Night	12% 6% 2 5% 4 3 4 3 5% 7% 48%	2836
	11th to 20th	Night	13% 5% 1 4 3 3 4 4 6% 8% 49%	2798
	21st to end	Night	8% 6% 2 6% 4 4 4 3 6% 7% 50%	3284
September	1st to 10th	Night	8% 4 2 4 3 2 4 3 4 9% 56%	1900
	11th to 20th	Night	10% 4 1 4 3 3 4 4 6% 7% 55%	1967
	21st to end	Night	11% 5% 2 4 4 3 4 3 4 6% 53%	2135
October	1st to 10th	Night	14% 6% 2 5% 3 3 3 2 4 7% 50%	2280
	11th to 20th	Night	14% 9% 2 6% 4 4 4 3 5% 7% 42%	2280
	21st to end	Night	17% 10% 3 7% 3 3 4 3 5% 6% 39%	2508
November	1st to 10th	Night	13% 8% 2 6% 4 5% 4 3 6% 6% 44%	2575
	11th to 20th	Night	13% 11% 4 10% 6% 4 4 3 5% 4 36%	2660
	21st to end	Night	14% 8% 3 8% 5% 4 4 4 4 6% 40%	2660
December	1st to 10th	Night	10% 10% 3 11% 7% 5% 4 4 5% 6% 33%	2660
	11th to 20th	Night	11% 13% 4 10% 7% 6% 6% 4 6% 6% 29%	3279
	21st to end	Night	21% 14% 5% 13% 5% 4 4 3 4 5% 22%	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	66% 3 11% 16% 3	2528
	11th to 20th	Day	63% 3 10% 19% 5%	2628
	21st to end	Day	64% 3 12% 16% 4	3135
February	1st to 10th	Day	53% 4 13% 21% 8% 1	1710
	11th to 20th	Day	50% 5% 12% 23% 8% 1	1673
	21st to end	Day	52% 4 13% 20% 12%	1441
March	1st to 10th	Day	47% 2 13% 28% 10%	3426
	11th to 20th	Day	43% 3 9% 32% 10% 2	3480
	21st to end	Day	66% 3 9% 18% 4	3814
April	1st to 10th	Day	48% 3 13% 23% 12% 1	2274
	11th to 20th	Day	53% 3 9% 21% 12% 1	2299
	21st to end	Day	55% 3 12% 21% 9% 1	2470
May	1st to 10th	Day	44% 3 11% 26% 14% 1	4230
	11th to 20th	Day	39% 3 9% 31% 16% 2	4403
	21st to end	Day	48% 3 11% 28% 10% 1	4837
June	1st to 10th	Day	35% 4 15% 31% 14% 1	2660
	11th to 20th	Day	41% 5% 14% 23% 16% 1	2719
	21st to end	Day	37% 5% 18% 28% 11% 2	2850
July	1st to 10th	Day	38% 6% 19% 24% 11% 1	4556
	11th to 20th	Day	22% 5% 16% 37% 18% 2	4365
	21st to end	Day	30% 6% 14% 32% 16% 1	4519
August	1st to 10th	Day	39% 5% 12% 30% 13% 2	4090
	11th to 20th	Day	38% 5% 13% 33% 10%	4080
	21st to end	Day	35% 4 16% 30% 14% 1	4376
September	1st to 10th	Day	34% 5% 13% 34% 14%	2280
	11th to 20th	Day	37% 3 16% 34% 10%	2209
	21st to end	Day	39% 4 12% 33% 12% 1	2025
October	1st to 10th	Day	32% 2 8% 34% 23%	3160
	11th to 20th	Day	38% 4 11% 26% 20% 1	3140
	21st to end	Day	44% 2 14% 29% 10%	3428
November	1st to 10th	Day	46% 4 13% 20% 14% 3	1569
	11th to 20th	Day	53% 4 14% 18% 11%	1520
	21st to end	Day	47% 4 18% 23% 7% 1	1520
December	1st to 10th	Day	57% 4 16% 16% 7%	1520
	11th to 20th	Day	56% 3 19% 17% 5%	1915
	21st to end	Day	69% 2 9% 14% 5%	2783
January	1st to 10th	Night	62% 2 11% 19% 6%	4428
	11th to 20th	Night	63% 3 11% 19% 5%	4340
	21st to end	Night	62% 2 9% 20% 6% 1	4532
February	1st to 10th	Night	50% 2 12% 23% 11% 1	2470
	11th to 20th	Night	43% 4 15% 26% 10% 2	2404
	21st to end	Night	47% 3 11% 24% 13% 2	2012
March	1st to 10th	Night	37% 3 13% 30% 17% 1	3454
	11th to 20th	Night	41% 3 8% 31% 17% 1	3480
	21st to end	Night	60% 2 6% 21% 8% 1	3817
April	1st to 10th	Night	47% 4 10% 25% 13% 1	1905
	11th to 20th	Night	51% 3 7% 20% 17% 3	1827
	21st to end	Night	50% 4 8% 23% 14% 2	1710
May	1st to 10th	Night	43% 3 9% 22% 20% 2	2738
	11th to 20th	Night	34% 3 10% 27% 21% 4	2507
	21st to end	Night	41% 2 12% 28% 15% 1	2751
June	1st to 10th	Night	30% 3 14% 32% 18% 3	1520
	11th to 20th	Night	33% 5% 16% 23% 19% 3	1454
	21st to end	Night	26% 4 16% 32% 18% 3	1330
July	1st to 10th	Night	34% 6% 20% 25% 14% 1	2296
	11th to 20th	Night	21% 4 14% 41% 19% 2	2482
	21st to end	Night	25% 5% 16% 35% 18% 3	2801
August	1st to 10th	Night	36% 4 12% 30% 14% 5%	2826
	11th to 20th	Night	32% 5% 15% 33% 15% 1	2825
	21st to end	Night	33% 5% 17% 29% 14% 2	3284
September	1st to 10th	Night	27% 4 14% 34% 20% 1	1900
	11th to 20th	Night	29% 4 17% 33% 18% 1	1967
	21st to end	Night	33% 3 12% 33% 18% 2	2135
October	1st to 10th	Night	24% 2 5% 37% 28% 4	3800
	11th to 20th	Night	31% 3 13% 27% 23% 3	3779
	21st to end	Night	42% 3 12% 30% 13% 1	4120
November	1st to 10th	Night	41% 3 14% 26% 14% 2	2575
	11th to 20th	Night	52% 4 12% 19% 12% 1	2660
	21st to end	Night	47% 3 16% 24% 8% 1	2660
December	1st to 10th	Night	52% 4 16% 21% 7%	2660
	11th to 20th	Night	55% 4 14% 19% 6% 2	3281
	21st to end	Night	67% 2 9% 17% 4	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	14% 11% 36% 26% 12% 2	270
	11th to 20th	Day	13% 13% 41% 27% 4 1	270
	21st to end	Day	17% 8% 38% 25% 11% 2	297
February	1st to 10th	Day	13% 14% 47% 23% 3	270
	11th to 20th	Day	16% 15% 40% 23% 6% 1	270
	21st to end	Day	16% 11% 44% 26% 2	225
March	1st to 10th	Day	19% 13% 40% 23% 6%	270
	11th to 20th	Day	19% 8% 40% 24% 7% 1	270
	21st to end	Day	25% 14% 27% 24% 8% 2	297
April	1st to 10th	Day	24% 15% 34% 22% 5%	454
	11th to 20th	Day	28% 13% 26% 21% 10% 1	497
	21st to end	Day	25% 13% 30% 21% 9% 2	650
May	1st to 10th	Day	19% 12% 36% 23% 8% 1	653
	11th to 20th	Day	19% 8% 31% 23% 15% 3	675
	21st to end	Day	19% 9% 28% 26% 15% 3	734
June	1st to 10th	Day	11% 6% 26% 32% 20% 4	680
	11th to 20th	Day	16% 8% 33% 30% 11% 3	680
	21st to end	Day	12% 7% 32% 29% 16% 4	680
July	1st to 10th	Day	9% 4 24% 31% 24% 8%	671
	11th to 20th	Day	10% 6% 25% 32% 21% 6%	668
	21st to end	Day	6% 4 24% 38% 23% 6%	739
August	1st to 10th	Day	11% 5% 21% 34% 25% 4	676
	11th to 20th	Day	14% 4 21% 31% 24% 6%	665
	21st to end	Day	11% 5% 26% 35% 19% 5%	658
September	1st to 10th	Day	13% 8% 28% 30% 16% 5%	490
	11th to 20th	Day	12% 5% 30% 31% 17% 5%	419
	21st to end	Day	19% 8% 30% 23% 12% 7%	300
October	1st to 10th	Day	16% 12% 27% 25% 13% 7%	300
	11th to 20th	Day	15% 19% 34% 22% 9% 1	300
	21st to end	Day	25% 14% 37% 16% 8% 1	330
November	1st to 10th	Day	20% 11% 34% 24% 9% 1	279
	11th to 20th	Day	12% 17% 44% 22% 4	270
	21st to end	Day	21% 14% 40% 20% 5%	270
December	1st to 10th	Day	13% 11% 39% 28% 9% 1	270
	11th to 20th	Day	19% 14% 36% 24% 6%	270
	21st to end	Day	27% 11% 37% 21% 4	297
January	1st to 10th	Night	11% 10% 40% 29% 9% 1	950
	11th to 20th	Night	15% 10% 38% 30% 6% 1	950
	21st to end	Night	17% 10% 36% 30% 7%	1045
February	1st to 10th	Night	13% 11% 39% 30% 6% 1	950
	11th to 20th	Night	10% 11% 43% 29% 6% 1	929
	21st to end	Night	15% 10% 36% 30% 8% 1	756
March	1st to 10th	Night	17% 8% 40% 25% 9% 1	594
	11th to 20th	Night	18% 9% 38% 28% 6% 1	570
	21st to end	Night	23% 10% 31% 24% 11% 2	627
April	1st to 10th	Night	19% 11% 36% 28% 5%	570
	11th to 20th	Night	23% 11% 29% 28% 8% 1	563
	21st to end	Night	22% 11% 31% 28% 7% 1	570
May	1st to 10th	Night	18% 10% 34% 30% 8%	570
	11th to 20th	Night	17% 8% 33% 32% 10% 1	561
	21st to end	Night	15% 8% 25% 36% 15%	617
June	1st to 10th	Night	11% 3 30% 40% 15% 1	570
	11th to 20th	Night	11% 5% 29% 44% 10%	570
	21st to end	Night	10% 3 25% 46% 16%	570
July	1st to 10th	Night	6% 2 23% 39% 27% 3	555
	11th to 20th	Night	5% 3 24% 47% 21% 2	552
	21st to end	Night	5% 1 22% 49% 21% 2	624
August	1st to 10th	Night	8% 2 17% 48% 23% 1	567
	11th to 20th	Night	12% 2 19% 40% 25% 3	564
	21st to end	Night	7% 4 26% 37% 23% 3	627
September	1st to 10th	Night	10% 2 26% 41% 19% 2	570
	11th to 20th	Night	10% 5% 32% 32% 19% 2	570
	21st to end	Night	12% 9% 31% 32% 15% 1	615
October	1st to 10th	Night	16% 9% 30% 30% 14% 1	760
	11th to 20th	Night	18% 11% 35% 28% 7% 1	760
	21st to end	Night	22% 11% 31% 29% 6%	836
November	1st to 10th	Night	18% 10% 33% 30% 9% 1	895
	11th to 20th	Night	18% 11% 39% 24% 8%	950
	21st to end	Night	19% 11% 37% 26% 7%	950
December	1st to 10th	Night	16% 9% 38% 28% 9% 1	950
	11th to 20th	Night	19% 8% 38% 28% 6% 1	950
	21st to end	Night	24% 10% 34% 27% 4 1	1045

Page generated at 2024-11-01 21:47:34. Version ac07

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