Mesa Vista Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mesa Vista Observatory clear sky chart from 2005-11-06 to 2026-08-30.

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	3 4 2 4 3 4 5% 4 6% 7% 59%	151862
	Night	3 4 2 4 3 4 4 3 5% 7% 60%	147889
Transparency	Day	21% 5% 11% 20% 26% 17%	146885
	Night	21% 5% 10% 20% 27% 16%	143875
Seeing	Day	11% 19% 30% 26% 12% 2	17629
	Night	7% 14% 32% 32% 14% 2	27655

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	1 6% 4 6% 2 3 3 2 5% 7% 60%	5080
	11th to 20th	Day	1 3 3 4 2 1 2 2 3 4 77%	5340
	21st to end	Day	2 6% 2 6% 3 4 4 3 5% 5% 59%	5844
February	1st to 10th	Day	1 6% 2 5% 3 3 3 3 5% 8% 61%	1950
	11th to 20th	Day	2 6% 2 5% 3 3 4 3 6% 7% 60%	2049
	21st to end	Day	2 8% 1 4 3 2 2 2 5% 6% 64%	1730
March	1st to 10th	Day	1 6% 2 4 3 3 3 3 5% 7% 65%	4757
	11th to 20th	Day	3 6% 2 5% 4 4 5% 4 5% 7% 54%	5110
	21st to end	Day	2 4 1 4 3 3 4 3 6% 8% 61%	5846
April	1st to 10th	Day	2 4 1 4 3 3 4 4 6% 7% 62%	2520
	11th to 20th	Day	3 5% 2 5% 3 3 3 4 5% 5% 62%	2491
	21st to end	Day	3 5% 2 4 3 3 4 3 4 7% 64%	2520
May	1st to 10th	Day	5% 5% 2 5% 3 4 5% 4 6% 7% 55%	7057
	11th to 20th	Day	4 3 1 2 2 3 3 3 5% 6% 69%	7377
	21st to end	Day	2 2 1 3 3 3 4 4 5% 7% 66%	9026
June	1st to 10th	Day	2 2 1 4 4 4 4 4 7% 9% 59%	2940
	11th to 20th	Day	3 2 1 3 3 2 4 3 5% 6% 69%	2940
	21st to end	Day	5% 4 2 4 5% 4 5% 4 7% 7% 54%	2940
July	1st to 10th	Day	2 2 1 4 4 5% 6% 5% 7% 8% 56%	8249
	11th to 20th	Day	1 2 1 5% 5% 7% 10% 7% 10% 11% 41%	7716
	21st to end	Day	3 3 2 6% 6% 7% 9% 6% 9% 10% 38%	8304
August	1st to 10th	Day	3 2 1 4 5% 6% 6% 6% 8% 10% 50%	5691
	11th to 20th	Day	3 3 1 5% 5% 5% 6% 6% 8% 10% 49%	5486
	21st to end	Day	3 3 2 6% 5% 6% 7% 6% 9% 11% 42%	6093
September	1st to 10th	Day	6% 4 2 6% 5% 5% 5% 4 7% 7% 48%	2400
	11th to 20th	Day	7% 4 2 4 3 4 5% 4 6% 8% 55%	2400
	21st to end	Day	4 2 1 3 3 3 3 4 5% 7% 65%	2192
October	1st to 10th	Day	5% 3 1 3 3 2 2 2 3 5% 70%	3270
	11th to 20th	Day	7% 4 2 5% 3 3 3 3 4 6% 61%	3250
	21st to end	Day	3 3 1 2 1 2 1 1 3 5% 78%	3548
November	1st to 10th	Day	2 3 1 3 2 3 3 2 5% 7% 70%	1954
	11th to 20th	Day	2 3 1 3 3 3 3 3 5% 7% 69%	1890
	21st to end	Day	4 5% 2 3 3 3 3 3 5% 5% 65%	1890
December	1st to 10th	Day	1 3 1 2 2 1 2 2 3 6% 76%	2814
	11th to 20th	Day	2 3 1 4 4 2 3 3 4 7% 66%	3106
	21st to end	Day	2 4 1 3 2 2 3 2 4 6% 70%	4092
January	1st to 10th	Night	1 5% 3 7% 4 4 4 3 5% 7% 58%	7883
	11th to 20th	Night	1 2 2 3 2 3 3 2 3 4 75%	7650
	21st to end	Night	2 5% 2 5% 3 3 4 3 5% 7% 61%	8370
February	1st to 10th	Night	2 6% 2 5% 2 3 3 2 4 7% 64%	2667
	11th to 20th	Night	3 6% 2 4 3 4 4 3 4 7% 60%	2458
	21st to end	Night	3 6% 2 3 2 3 3 3 4 6% 66%	2076
March	1st to 10th	Night	2 4 1 4 3 3 4 3 4 6% 66%	5329
	11th to 20th	Night	5% 5% 3 5% 3 4 3 3 4 5% 59%	5110
	21st to end	Night	2 4 1 4 3 3 4 3 4 6% 67%	5358
April	1st to 10th	Night	3 4 1 3 3 2 3 3 6% 7% 65%	2100
	11th to 20th	Night	3 5% 1 4 3 3 3 2 4 6% 64%	2077
	21st to end	Night	3 3 1 4 3 3 3 3 5% 5% 67%	2100
May	1st to 10th	Night	6% 5% 1 4 3 4 4 4 6% 8% 55%	5890
	11th to 20th	Night	4 3 1 3 3 3 3 3 4 6% 65%	5483
	21st to end	Night	4 3 1 4 3 3 4 3 5% 7% 62%	5181
June	1st to 10th	Night	3 4 1 4 5% 5% 4 5% 6% 8% 55%	1680
	11th to 20th	Night	2 2 1 3 3 3 4 3 4 7% 67%	1680
	21st to end	Night	6% 5% 1 5% 4 4 5% 5% 6% 8% 52%	1680
July	1st to 10th	Night	4 4 2 5% 4 4 5% 4 6% 8% 52%	4740
	11th to 20th	Night	2 3 1 4 4 5% 7% 6% 10% 14% 44%	5255
	21st to end	Night	4 4 2 5% 5% 6% 7% 7% 11% 13% 36%	5805
August	1st to 10th	Night	2 3 2 6% 6% 6% 7% 6% 8% 10% 43%	4337
	11th to 20th	Night	2 3 1 5% 4 6% 6% 6% 9% 12% 45%	4583
	21st to end	Night	4 5% 2 7% 5% 6% 7% 6% 9% 13% 35%	5083
September	1st to 10th	Night	5% 3 1 4 4 3 5% 4 9% 9% 52%	2000
	11th to 20th	Night	6% 3 1 5% 4 4 4 3 5% 7% 57%	2000
	21st to end	Night	4 3 1 4 3 3 4 3 4 7% 63%	2202
October	1st to 10th	Night	5% 3 1 2 2 2 2 2 3 4 73%	3920
	11th to 20th	Night	8% 4 2 4 2 3 3 2 4 6% 62%	3898
	21st to end	Night	3 2 1 2 1 1 2 2 4 5% 77%	4252
November	1st to 10th	Night	3 2 1 3 2 2 3 3 4 6% 73%	2540
	11th to 20th	Night	2 2 1 2 2 2 4 3 4 6% 72%	2730
	21st to end	Night	5% 5% 1 3 3 3 3 3 4 5% 64%	2730
December	1st to 10th	Night	2 2 1 3 2 2 2 2 3 7% 74%	4593
	11th to 20th	Night	2 3 1 3 3 3 3 3 5% 8% 68%	5321
	21st to end	Night	3 4 2 4 3 3 3 2 4 5% 68%	7128

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	23% 4 7% 30% 30% 7%	5083
	11th to 20th	Day	11% 4 8% 24% 32% 21%	5340
	21st to end	Day	23% 4 7% 14% 35% 16%	5844
February	1st to 10th	Day	22% 5% 10% 21% 29% 14%	1950
	11th to 20th	Day	22% 5% 9% 26% 26% 14%	2059
	21st to end	Day	20% 3 6% 18% 34% 19%	1730
March	1st to 10th	Day	18% 2 6% 13% 35% 26%	4757
	11th to 20th	Day	23% 4 11% 19% 30% 14%	5110
	21st to end	Day	17% 4 8% 28% 35% 8%	5846
April	1st to 10th	Day	19% 5% 8% 21% 31% 16%	2520
	11th to 20th	Day	21% 5% 6% 19% 29% 19%	2494
	21st to end	Day	18% 4 9% 21% 33% 14%	2520
May	1st to 10th	Day	24% 5% 11% 17% 28% 14%	7057
	11th to 20th	Day	15% 3 7% 15% 29% 29%	7381
	21st to end	Day	16% 5% 11% 15% 20% 34%	9027
June	1st to 10th	Day	18% 7% 13% 20% 23% 19%	2940
	11th to 20th	Day	15% 4 9% 14% 23% 35%	2940
	21st to end	Day	26% 6% 11% 18% 21% 19%	2940
July	1st to 10th	Day	21% 7% 11% 15% 19% 27%	8181
	11th to 20th	Day	28% 11% 21% 26% 9% 5%	7645
	21st to end	Day	32% 11% 21% 24% 10% 2	8120
August	1st to 10th	Day	31% 12% 19% 19% 13% 6%	4175
	11th to 20th	Day	22% 8% 12% 28% 19% 11%	4002
	21st to end	Day	32% 10% 17% 23% 16% 2	4420
September	1st to 10th	Day	30% 8% 12% 20% 22% 9%	2400
	11th to 20th	Day	25% 6% 10% 19% 24% 15%	2400
	21st to end	Day	18% 4 8% 22% 33% 15%	2192
October	1st to 10th	Day	17% 3 5% 15% 31% 29%	3270
	11th to 20th	Day	25% 3 6% 14% 30% 22%	3250
	21st to end	Day	13% 1 5% 14% 42% 25%	3548
November	1st to 10th	Day	14% 3 8% 18% 42% 17%	1954
	11th to 20th	Day	15% 4 7% 23% 37% 14%	1890
	21st to end	Day	21% 3 7% 19% 30% 19%	1890
December	1st to 10th	Day	11% 3 7% 23% 41% 16%	2814
	11th to 20th	Day	18% 4 7% 22% 40% 11%	3104
	21st to end	Day	15% 2 8% 25% 36% 13%	4092
January	1st to 10th	Night	25% 4 7% 26% 28% 10%	7884
	11th to 20th	Night	13% 4 6% 23% 35% 18%	7650
	21st to end	Night	21% 4 8% 15% 35% 17%	8370
February	1st to 10th	Night	21% 4 10% 22% 28% 15%	2667
	11th to 20th	Night	24% 3 10% 24% 25% 13%	2458
	21st to end	Night	19% 4 5% 17% 34% 21%	2076
March	1st to 10th	Night	18% 3 7% 11% 36% 26%	5329
	11th to 20th	Night	24% 5% 8% 17% 32% 14%	5110
	21st to end	Night	15% 4 8% 27% 36% 10%	5358
April	1st to 10th	Night	18% 5% 8% 21% 30% 18%	2100
	11th to 20th	Night	21% 4 9% 18% 28% 21%	2077
	21st to end	Night	18% 6% 9% 20% 34% 13%	2100
May	1st to 10th	Night	24% 7% 11% 21% 23% 15%	5888
	11th to 20th	Night	17% 5% 10% 16% 25% 27%	5484
	21st to end	Night	19% 6% 12% 13% 15% 35%	5182
June	1st to 10th	Night	23% 9% 14% 17% 18% 19%	1680
	11th to 20th	Night	17% 4 8% 15% 21% 35%	1680
	21st to end	Night	28% 7% 14% 16% 16% 20%	1680
July	1st to 10th	Night	28% 7% 11% 18% 17% 20%	4700
	11th to 20th	Night	24% 11% 28% 24% 8% 5%	5203
	21st to end	Night	32% 12% 25% 22% 9% 1	5677
August	1st to 10th	Night	36% 11% 18% 17% 12% 6%	3177
	11th to 20th	Night	27% 11% 16% 21% 18% 8%	3343
	21st to end	Night	35% 11% 19% 23% 9% 3	3687
September	1st to 10th	Night	24% 9% 18% 22% 19% 8%	2000
	11th to 20th	Night	24% 7% 13% 16% 25% 15%	2000
	21st to end	Night	20% 5% 10% 19% 31% 15%	2202
October	1st to 10th	Night	16% 3 6% 15% 35% 24%	3920
	11th to 20th	Night	24% 4 5% 14% 28% 25%	3898
	21st to end	Night	11% 2 5% 18% 39% 26%	4252
November	1st to 10th	Night	13% 2 6% 23% 38% 18%	2540
	11th to 20th	Night	13% 3 9% 22% 38% 15%	2730
	21st to end	Night	22% 4 7% 20% 29% 19%	2730
December	1st to 10th	Night	13% 3 6% 28% 34% 16%	4593
	11th to 20th	Night	15% 3 8% 20% 38% 17%	5322
	21st to end	Night	17% 4 8% 22% 36% 12%	7128

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% 29% 31% 17% 4	330
	11th to 20th	Day	18% 29% 29% 17% 6% 1	330
	21st to end	Day	7% 29% 35% 19% 8% 1	363
February	1st to 10th	Day	14% 34% 30% 18% 3	330
	11th to 20th	Day	15% 38% 29% 15% 2	330
	21st to end	Day	21% 39% 25% 12% 2	273
March	1st to 10th	Day	14% 35% 31% 17% 2	396
	11th to 20th	Day	22% 30% 29% 14% 3 1	540
	21st to end	Day	21% 34% 31% 11% 2 1	594
April	1st to 10th	Day	16% 32% 35% 12% 3 1	540
	11th to 20th	Day	18% 38% 32% 10% 2	532
	21st to end	Day	17% 32% 39% 9% 2	540
May	1st to 10th	Day	13% 31% 38% 14% 3 1	543
	11th to 20th	Day	13% 19% 36% 24% 7% 1	655
	21st to end	Day	8% 18% 36% 29% 8% 1	844
June	1st to 10th	Day	3 9% 33% 37% 17% 2	780
	11th to 20th	Day	5% 12% 31% 34% 16% 1	780
	21st to end	Day	8% 10% 27% 33% 17% 4	780
July	1st to 10th	Day	5% 2 24% 35% 28% 5%	771
	11th to 20th	Day	4 1 11% 45% 31% 8%	589
	21st to end	Day	5% 1 12% 41% 32% 9%	619
August	1st to 10th	Day	4 3 19% 44% 25% 5%	567
	11th to 20th	Day	4 3 22% 40% 24% 6%	557
	21st to end	Day	4 3 23% 43% 22% 5%	620
September	1st to 10th	Day	6% 4 27% 41% 18% 3	530
	11th to 20th	Day	6% 6% 37% 36% 12% 3	530
	21st to end	Day	5% 12% 34% 30% 14% 4	330
October	1st to 10th	Day	10% 19% 30% 24% 14% 3	330
	11th to 20th	Day	15% 21% 31% 22% 9% 3	330
	21st to end	Day	12% 22% 33% 22% 9% 2	363
November	1st to 10th	Day	12% 30% 35% 17% 6% 1	330
	11th to 20th	Day	8% 22% 38% 23% 8% 1	330
	21st to end	Day	16% 27% 31% 19% 8%	330
December	1st to 10th	Day	16% 29% 28% 18% 8%	330
	11th to 20th	Day	10% 32% 33% 20% 5%	330
	21st to end	Day	19% 34% 29% 14% 4	363
January	1st to 10th	Night	6% 21% 36% 25% 10% 1	940
	11th to 20th	Night	8% 16% 39% 27% 8% 2	840
	21st to end	Night	6% 18% 40% 26% 9% 1	924
February	1st to 10th	Night	6% 19% 44% 25% 5% 1	840
	11th to 20th	Night	8% 24% 41% 22% 4	824
	21st to end	Night	10% 23% 47% 18% 2	692
March	1st to 10th	Night	8% 22% 39% 26% 5%	840
	11th to 20th	Night	10% 18% 34% 30% 8%	840
	21st to end	Night	8% 18% 43% 26% 4	814
April	1st to 10th	Night	8% 23% 41% 24% 4	630
	11th to 20th	Night	9% 22% 35% 28% 5%	623
	21st to end	Night	7% 19% 42% 26% 5%	630
May	1st to 10th	Night	6% 14% 40% 32% 9%	630
	11th to 20th	Night	7% 12% 33% 33% 14% 1	621
	21st to end	Night	6% 12% 35% 38% 9% 1	683
June	1st to 10th	Night	4 6% 28% 43% 18%	630
	11th to 20th	Night	2 7% 31% 45% 14% 1	630
	21st to end	Night	6% 5% 21% 44% 23% 2	630
July	1st to 10th	Night	5% 1 13% 44% 33% 3	615
	11th to 20th	Night	3 1 7% 41% 43% 5%	612
	21st to end	Night	5% 2 7% 33% 48% 6%	690
August	1st to 10th	Night	4 1 9% 36% 42% 7%	627
	11th to 20th	Night	4 2 12% 42% 38% 3	624
	21st to end	Night	5% 1 10% 43% 36% 5%	687
September	1st to 10th	Night	5% 3 13% 48% 28% 4	600
	11th to 20th	Night	7% 3 17% 48% 25% 2	600
	21st to end	Night	5% 6% 25% 44% 19% 2	604
October	1st to 10th	Night	9% 8% 23% 42% 18% 1	800
	11th to 20th	Night	7% 11% 33% 34% 12% 3	800
	21st to end	Night	5% 13% 32% 33% 14% 3	880
November	1st to 10th	Night	4 13% 37% 33% 12% 2	900
	11th to 20th	Night	3 16% 36% 33% 9% 2	1050
	21st to end	Night	9% 17% 35% 28% 10% 2	1050
December	1st to 10th	Night	8% 20% 38% 26% 7% 1	1050
	11th to 20th	Night	7% 21% 38% 26% 8%	1050
	21st to end	Night	11% 21% 43% 22% 4	1155

Page generated at 2026-08-27 02:07:15. Version ac07

Copyright © 2026 Attilla Danko.