Lake Meade Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lake Meade Observatory clear sky chart from 2005-11-06 to 2024-11-30.

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	15% 7% 2 6% 4 4 5% 4 6% 7% 40%	101541
	Night	15% 7% 2 6% 4 4 4 4 5% 7% 41%	98011
Transparency	Day	41% 6% 12% 24% 15% 2	105178
	Night	41% 5% 12% 24% 15% 2	102512
Seeing	Day	19% 12% 25% 24% 15% 6%	14968
	Night	17% 8% 29% 32% 12% 1	24414

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	15% 8% 3 7% 4 4 5% 3 5% 5% 42%	2517
	11th to 20th	Day	13% 12% 4 10% 5% 6% 5% 4 5% 5% 32%	2808
	21st to end	Day	17% 11% 3 9% 6% 4 4 3 4 6% 32%	3124
February	1st to 10th	Day	15% 8% 2 8% 6% 4 5% 4 5% 5% 37%	1710
	11th to 20th	Day	14% 8% 3 8% 5% 4 5% 4 4 7% 39%	1705
	21st to end	Day	19% 9% 3 7% 5% 3 4 3 5% 5% 37%	1570
March	1st to 10th	Day	22% 7% 2 5% 4 4 5% 3 5% 6% 36%	3337
	11th to 20th	Day	9% 6% 3 6% 5% 5% 5% 3 6% 8% 44%	3480
	21st to end	Day	19% 9% 2 6% 4 3 3 3 4 5% 42%	3900
April	1st to 10th	Day	14% 7% 3 6% 6% 5% 6% 4 5% 7% 38%	2280
	11th to 20th	Day	15% 7% 2 6% 5% 4 5% 3 5% 8% 42%	2254
	21st to end	Day	19% 7% 2 5% 4 3 5% 4 5% 6% 39%	2280
May	1st to 10th	Day	28% 7% 2 5% 4 4 4 4 5% 7% 30%	4051
	11th to 20th	Day	23% 8% 3 8% 5% 5% 5% 3 6% 6% 29%	4386
	21st to end	Day	11% 5% 2 6% 4 5% 5% 4 7% 9% 43%	4823
June	1st to 10th	Day	12% 6% 2 5% 5% 4 4 5% 8% 9% 40%	2660
	11th to 20th	Day	12% 6% 2 6% 5% 5% 5% 4 7% 9% 40%	2660
	21st to end	Day	9% 4 2 5% 4 5% 4 5% 7% 10% 44%	2660
July	1st to 10th	Day	6% 4 2 7% 5% 6% 6% 6% 8% 11% 41%	4440
	11th to 20th	Day	7% 5% 2 6% 5% 5% 6% 5% 7% 10% 41%	4440
	21st to end	Day	10% 7% 2 8% 6% 5% 5% 4 7% 8% 38%	4468
August	1st to 10th	Day	17% 5% 2 7% 4 5% 6% 4 7% 9% 34%	4104
	11th to 20th	Day	12% 6% 2 5% 4 5% 5% 5% 7% 8% 41%	3894
	21st to end	Day	13% 5% 2 5% 3 3 4 3 5% 8% 49%	4180
September	1st to 10th	Day	16% 6% 2 5% 4 4 4 3 4 7% 46%	2280
	11th to 20th	Day	13% 5% 2 5% 3 3 4 3 5% 8% 49%	2280
	21st to end	Day	22% 7% 3 5% 4 3 4 3 5% 7% 38%	2004
October	1st to 10th	Day	17% 6% 2 6% 4 4 3 3 6% 6% 43%	1900
	11th to 20th	Day	16% 6% 2 5% 4 3 4 2 4 6% 47%	1900
	21st to end	Day	15% 7% 2 6% 4 3 4 3 5% 6% 44%	2090
November	1st to 10th	Day	12% 7% 2 4 3 2 4 2 5% 7% 52%	1809
	11th to 20th	Day	15% 6% 1 5% 4 3 4 4 5% 6% 46%	1747
	21st to end	Day	15% 7% 3 5% 4 3 5% 4 5% 6% 44%	1598
December	1st to 10th	Day	18% 9% 3 7% 5% 4 4 4 6% 7% 34%	1520
	11th to 20th	Day	17% 8% 3 7% 5% 4 4 4 5% 7% 36%	1910
	21st to end	Day	18% 8% 3 8% 6% 5% 5% 5% 5% 6% 31%	2772
January	1st to 10th	Night	13% 9% 3 7% 5% 5% 4 3 5% 7% 38%	4429
	11th to 20th	Night	16% 9% 3 6% 4 4 4 3 5% 6% 39%	4149
	21st to end	Night	22% 9% 3 7% 4 4 4 3 5% 6% 34%	4532
February	1st to 10th	Night	16% 9% 2 6% 5% 4 5% 3 5% 7% 39%	2470
	11th to 20th	Night	16% 9% 3 7% 4 3 4 3 5% 7% 40%	2361
	21st to end	Night	17% 9% 3 7% 5% 3 4 4 5% 5% 38%	1884
March	1st to 10th	Night	20% 8% 3 6% 4 3 4 3 4 6% 38%	3513
	11th to 20th	Night	11% 6% 2 6% 4 4 4 4 5% 5% 49%	3480
	21st to end	Night	14% 10% 2 6% 4 4 3 3 4 5% 46%	3731
April	1st to 10th	Night	16% 8% 2 7% 5% 4 5% 4 6% 7% 36%	1900
	11th to 20th	Night	14% 6% 2 5% 4 4 4 4 5% 8% 44%	1875
	21st to end	Night	19% 6% 2 4 4 4 3 4 6% 7% 42%	1900
May	1st to 10th	Night	26% 7% 3 6% 4 4 4 3 5% 6% 31%	2860
	11th to 20th	Night	24% 8% 3 7% 5% 4 4 4 5% 6% 30%	2505
	21st to end	Night	11% 6% 2 6% 5% 5% 5% 5% 7% 10% 39%	2732
June	1st to 10th	Night	13% 5% 2 5% 4 3 5% 4 6% 7% 47%	1520
	11th to 20th	Night	11% 5% 3 5% 5% 3 6% 6% 7% 9% 40%	1520
	21st to end	Night	9% 5% 2 6% 4 5% 5% 4 7% 10% 43%	1520
July	1st to 10th	Night	7% 5% 2 6% 5% 6% 6% 4 7% 11% 42%	2520
	11th to 20th	Night	6% 5% 3 6% 5% 6% 5% 5% 7% 11% 41%	2520
	21st to end	Night	12% 7% 2 7% 5% 4 4 4 6% 9% 41%	3081
August	1st to 10th	Night	18% 5% 2 7% 4 4 5% 5% 7% 8% 35%	2825
	11th to 20th	Night	10% 7% 3 8% 5% 4 4 4 5% 8% 41%	2903
	21st to end	Night	14% 5% 2 5% 3 4 4 3 6% 8% 46%	3476
September	1st to 10th	Night	13% 6% 2 6% 4 4 4 3 5% 7% 47%	1900
	11th to 20th	Night	11% 6% 1 5% 4 3 4 3 4 7% 52%	1900
	21st to end	Night	21% 6% 2 5% 4 4 4 3 5% 6% 41%	2172
October	1st to 10th	Night	18% 7% 2 4 4 4 3 3 4 7% 44%	2280
	11th to 20th	Night	14% 5% 2 5% 4 3 4 3 5% 7% 49%	2280
	21st to end	Night	16% 6% 2 5% 3 3 4 3 6% 6% 46%	2508
November	1st to 10th	Night	10% 6% 2 5% 4 3 4 4 5% 5% 53%	2488
	11th to 20th	Night	14% 7% 2 5% 4 4 4 3 5% 7% 45%	2650
	21st to end	Night	13% 5% 2 6% 4 5% 5% 4 6% 6% 44%	2798
December	1st to 10th	Night	16% 7% 3 7% 5% 4 4 5% 5% 6% 37%	2660
	11th to 20th	Night	17% 7% 2 6% 5% 4 4 4 6% 6% 39%	3285
	21st to end	Night	17% 8% 3 7% 6% 5% 6% 5% 6% 7% 31%	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	43% 5% 13% 25% 11% 3	2518
	11th to 20th	Day	53% 5% 12% 16% 12% 3	2808
	21st to end	Day	53% 5% 10% 23% 7% 1	3124
February	1st to 10th	Day	47% 5% 12% 23% 11% 2	1710
	11th to 20th	Day	46% 5% 10% 25% 12% 2	1714
	21st to end	Day	49% 4 10% 21% 12% 4	1570
March	1st to 10th	Day	48% 5% 10% 24% 11% 2	3337
	11th to 20th	Day	36% 6% 11% 28% 16% 4	3480
	21st to end	Day	45% 4 10% 22% 16% 3	3900
April	1st to 10th	Day	44% 6% 11% 19% 16% 4	2280
	11th to 20th	Day	41% 5% 11% 23% 17% 4	2254
	21st to end	Day	44% 5% 10% 22% 16% 3	2280
May	1st to 10th	Day	53% 5% 9% 21% 11% 1	4088
	11th to 20th	Day	53% 8% 13% 17% 8% 1	4390
	21st to end	Day	34% 7% 14% 25% 17% 2	4837
June	1st to 10th	Day	38% 7% 14% 24% 16% 1	2660
	11th to 20th	Day	39% 8% 15% 23% 13% 2	2660
	21st to end	Day	33% 8% 14% 29% 15% 1	2660
July	1st to 10th	Day	35% 9% 14% 25% 13% 3	4370
	11th to 20th	Day	36% 7% 15% 27% 13% 2	4365
	21st to end	Day	42% 7% 11% 21% 18% 2	4325
August	1st to 10th	Day	45% 8% 13% 25% 9%	4091
	11th to 20th	Day	38% 6% 11% 28% 15% 1	3933
	21st to end	Day	35% 4 12% 29% 19% 2	4180
September	1st to 10th	Day	39% 5% 11% 21% 20% 4	2280
	11th to 20th	Day	33% 5% 10% 27% 21% 4	2280
	21st to end	Day	46% 5% 8% 18% 20% 2	2004
October	1st to 10th	Day	37% 4 8% 22% 25% 5%	3160
	11th to 20th	Day	28% 4 12% 29% 21% 6%	3140
	21st to end	Day	27% 3 11% 29% 28% 2	3428
November	1st to 10th	Day	33% 4 13% 26% 20% 4	1809
	11th to 20th	Day	38% 5% 11% 24% 19% 3	1747
	21st to end	Day	41% 4 12% 30% 10% 2	1598
December	1st to 10th	Day	48% 5% 15% 21% 10% 1	1520
	11th to 20th	Day	47% 5% 12% 27% 8% 1	1906
	21st to end	Day	51% 7% 16% 17% 8% 1	2772
January	1st to 10th	Night	45% 5% 13% 25% 10% 2	4429
	11th to 20th	Night	45% 5% 13% 24% 11% 2	4149
	21st to end	Night	52% 4 9% 25% 8% 2	4532
February	1st to 10th	Night	45% 4 14% 24% 11% 1	2470
	11th to 20th	Night	45% 4 10% 22% 17% 3	2363
	21st to end	Night	47% 4 11% 20% 14% 4	1884
March	1st to 10th	Night	47% 5% 10% 26% 11% 1	3513
	11th to 20th	Night	36% 5% 10% 32% 14% 2	3480
	21st to end	Night	41% 4 8% 22% 21% 4	3731
April	1st to 10th	Night	46% 4 10% 20% 15% 4	1900
	11th to 20th	Night	39% 6% 11% 21% 19% 4	1875
	21st to end	Night	40% 6% 10% 23% 16% 4	1900
May	1st to 10th	Night	54% 5% 9% 18% 12% 3	2887
	11th to 20th	Night	53% 7% 13% 16% 10% 1	2506
	21st to end	Night	37% 8% 15% 25% 12% 3	2739
June	1st to 10th	Night	34% 8% 11% 26% 18% 3	1520
	11th to 20th	Night	37% 8% 14% 23% 16% 2	1520
	21st to end	Night	35% 7% 14% 25% 17% 2	1520
July	1st to 10th	Night	36% 9% 17% 19% 14% 5%	2480
	11th to 20th	Night	36% 9% 15% 23% 15% 2	2472
	21st to end	Night	40% 6% 15% 19% 19% 2	2983
August	1st to 10th	Night	44% 6% 18% 23% 8% 1	2814
	11th to 20th	Night	40% 6% 11% 27% 16% 1	2930
	21st to end	Night	36% 5% 11% 29% 16% 2	3476
September	1st to 10th	Night	38% 5% 12% 20% 22% 4	1900
	11th to 20th	Night	32% 4 9% 28% 24% 3	1900
	21st to end	Night	44% 6% 9% 20% 19% 2	2172
October	1st to 10th	Night	41% 5% 10% 21% 21% 2	3800
	11th to 20th	Night	27% 4 10% 28% 27% 5%	3779
	21st to end	Night	26% 3 11% 34% 24% 3	4120
November	1st to 10th	Night	32% 5% 11% 26% 22% 5%	2488
	11th to 20th	Night	39% 4 9% 25% 18% 5%	2650
	21st to end	Night	39% 4 13% 26% 16% 2	2798
December	1st to 10th	Night	47% 5% 13% 23% 12%	2660
	11th to 20th	Night	44% 5% 13% 22% 14% 2	3288
	21st to end	Night	49% 7% 16% 20% 8% 1	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	23% 23% 32% 17% 4 2	180
	11th to 20th	Day	26% 28% 31% 11% 3	261
	21st to end	Day	21% 25% 35% 13% 4 1	297
February	1st to 10th	Day	21% 24% 37% 14% 2 1	270
	11th to 20th	Day	25% 27% 37% 10% 1	312
	21st to end	Day	32% 16% 32% 17% 3	382
March	1st to 10th	Day	20% 20% 31% 23% 5%	460
	11th to 20th	Day	20% 23% 33% 18% 5% 2	460
	21st to end	Day	25% 18% 28% 21% 7% 1	506
April	1st to 10th	Day	23% 17% 32% 19% 8% 1	460
	11th to 20th	Day	19% 16% 29% 19% 13% 4	452
	21st to end	Day	26% 11% 29% 23% 9% 3	460
May	1st to 10th	Day	28% 11% 26% 21% 10% 4	463
	11th to 20th	Day	21% 11% 26% 24% 13% 5%	487
	21st to end	Day	17% 5% 18% 28% 23% 8%	529
June	1st to 10th	Day	16% 8% 26% 24% 18% 8%	490
	11th to 20th	Day	14% 7% 22% 27% 21% 8%	490
	21st to end	Day	11% 5% 25% 32% 19% 7%	490
July	1st to 10th	Day	12% 5% 16% 29% 25% 14%	485
	11th to 20th	Day	5% 4 18% 31% 29% 13%	484
	21st to end	Day	12% 3 19% 33% 25% 8%	532
August	1st to 10th	Day	12% 3 14% 29% 31% 10%	486
	11th to 20th	Day	13% 5% 15% 31% 23% 13%	479
	21st to end	Day	12% 6% 14% 29% 26% 13%	539
September	1st to 10th	Day	18% 5% 16% 23% 23% 14%	490
	11th to 20th	Day	14% 3 14% 29% 25% 14%	490
	21st to end	Day	27% 8% 21% 24% 15% 6%	490
October	1st to 10th	Day	22% 6% 21% 24% 18% 9%	490
	11th to 20th	Day	16% 14% 27% 24% 17% 3	490
	21st to end	Day	17% 9% 37% 23% 11% 3	539
November	1st to 10th	Day	17% 11% 29% 27% 13% 2	420
	11th to 20th	Day	18% 15% 29% 25% 11% 1	347
	21st to end	Day	20% 21% 32% 19% 9% 1	200
December	1st to 10th	Day	26% 23% 27% 16% 7% 2	180
	11th to 20th	Day	23% 18% 32% 21% 5% 1	180
	21st to end	Day	22% 18% 28% 22% 9% 1	198
January	1st to 10th	Night	16% 15% 43% 23% 3	760
	11th to 20th	Night	21% 15% 33% 28% 4	760
	21st to end	Night	18% 13% 41% 26% 2	836
February	1st to 10th	Night	20% 15% 33% 29% 2	760
	11th to 20th	Night	20% 18% 41% 19% 1	743
	21st to end	Night	22% 15% 42% 18% 3	628
March	1st to 10th	Night	17% 14% 40% 24% 4	760
	11th to 20th	Night	22% 13% 36% 24% 5%	760
	21st to end	Night	20% 11% 39% 24% 6% 1	836
April	1st to 10th	Night	21% 15% 37% 22% 5%	760
	11th to 20th	Night	17% 10% 35% 30% 8% 1	751
	21st to end	Night	21% 9% 33% 30% 8%	760
May	1st to 10th	Night	21% 7% 26% 33% 12%	604
	11th to 20th	Night	20% 5% 26% 38% 11%	384
	21st to end	Night	15% 2 18% 46% 18% 1	411
June	1st to 10th	Night	13% 2 24% 40% 21% 1	380
	11th to 20th	Night	13% 2 23% 43% 19% 1	380
	21st to end	Night	10% 2 24% 50% 15%	380
July	1st to 10th	Night	11% 3 16% 41% 26% 2	370
	11th to 20th	Night	7% 1 12% 49% 28% 2	368
	21st to end	Night	10% 2 13% 46% 28% 1	618
August	1st to 10th	Night	12% 2 9% 46% 29% 2	567
	11th to 20th	Night	11% 3 10% 44% 27% 4	630
	21st to end	Night	14% 2 13% 39% 29% 3	836
September	1st to 10th	Night	15% 2 16% 37% 27% 3	760
	11th to 20th	Night	13% 3 13% 38% 29% 3	760
	21st to end	Night	24% 3 17% 34% 21% 2	760
October	1st to 10th	Night	21% 3 22% 31% 19% 4	760
	11th to 20th	Night	18% 7% 28% 33% 13% 1	760
	21st to end	Night	19% 6% 34% 30% 10% 1	836
November	1st to 10th	Night	14% 7% 33% 35% 11% 1	780
	11th to 20th	Night	18% 11% 33% 29% 8% 1	800
	21st to end	Night	16% 12% 35% 30% 8%	800
December	1st to 10th	Night	21% 12% 38% 23% 6% 1	760
	11th to 20th	Night	19% 8% 39% 30% 4	760
	21st to end	Night	19% 10% 37% 30% 3	836

Page generated at 2024-11-27 17:30:54. Version ac07

Copyright © 2024 Attilla Danko.