Bosque Farms Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bosque Farms Observatory clear sky chart from 2005-11-06 to 2026-09-29.

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	2 3 1 3 3 3 4 3 6% 8% 65%	156530
	Night	4 4 2 5% 3 4 4 4 6% 8% 58%	152493
Transparency	Day	16% 5% 10% 21% 28% 20%	151526
	Night	22% 5% 10% 19% 26% 18%	148504
Seeing	Day	5% 8% 20% 31% 26% 10%	17480
	Night	5% 5% 25% 43% 21% 1	27607

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	3 7% 2 4 2 3 4 4 6% 8% 56%	5318
	11th to 20th	Day	2 3 1 2 2 2 2 3 4 6% 74%	5340
	21st to end	Day	4 5% 2 5% 3 3 3 4 5% 6% 61%	5844
February	1st to 10th	Day	3 4 2 4 2 2 3 4 4 6% 64%	1890
	11th to 20th	Day	3 4 2 5% 3 3 4 3 6% 7% 60%	2047
	21st to end	Day	3 4 2 3 2 2 4 3 5% 5% 68%	1730
March	1st to 10th	Day	2 3 1 3 3 2 3 3 5% 6% 68%	4990
	11th to 20th	Day	4 4 2 5% 4 4 3 3 5% 7% 60%	5110
	21st to end	Day	2 4 1 4 3 3 3 4 6% 7% 63%	5710
April	1st to 10th	Day	3 2 1 3 3 3 3 3 5% 6% 68%	2520
	11th to 20th	Day	3 3 1 3 2 3 4 3 4 6% 67%	2491
	21st to end	Day	2 2 1 2 2 2 3 3 5% 6% 71%	2520
May	1st to 10th	Day	3 2 1 3 2 3 4 3 5% 7% 65%	7057
	11th to 20th	Day	2 2 1 2 2 3 3 3 5% 6% 71%	7304
	21st to end	Day	2 1 1 2 2 2 2 3 4 6% 75%	8724
June	1st to 10th	Day	2 2 1 3 3 3 3 4 6% 10% 64%	2940
	11th to 20th	Day	2 2 1 3 2 2 2 3 5% 6% 74%	2940
	21st to end	Day	3 3 1 3 3 4 4 4 6% 7% 60%	2939
July	1st to 10th	Day	2 1 1 3 3 3 4 4 6% 7% 65%	7649
	11th to 20th	Day	1 1 1 2 3 3 5% 5% 9% 14% 56%	7650
	21st to end	Day	2 2 1 4 4 5% 6% 5% 9% 12% 50%	8304
August	1st to 10th	Day	1 1 1 2 2 3 4 4 7% 11% 63%	7421
	11th to 20th	Day	1 1 1 3 3 3 4 4 7% 10% 62%	7003
	21st to end	Day	2 2 1 4 4 4 5% 5% 9% 12% 53%	7751
September	1st to 10th	Day	4 3 2 4 4 4 4 5% 7% 8% 56%	2520
	11th to 20th	Day	5% 3 1 3 4 3 4 3 6% 8% 60%	2520
	21st to end	Day	4 2 1 3 3 2 3 3 4 5% 70%	2233
October	1st to 10th	Day	3 1 1 2 2 2 2 2 4 5% 77%	3270
	11th to 20th	Day	3 2 1 2 2 2 3 3 4 6% 71%	3250
	21st to end	Day	2 1 1 1 1 1 2 2 3 5% 80%	3548
November	1st to 10th	Day	3 2 1 2 2 2 2 2 4 8% 73%	2059
	11th to 20th	Day	2 2 1 3 2 3 3 3 4 5% 72%	1927
	21st to end	Day	4 4 1 3 3 3 4 3 4 5% 66%	1890
December	1st to 10th	Day	3 3 1 2 2 2 2 2 3 5% 76%	2738
	11th to 20th	Day	2 3 1 4 3 3 3 2 4 7% 68%	3106
	21st to end	Day	3 4 1 3 2 3 3 2 4 7% 68%	4277
January	1st to 10th	Night	3 9% 2 5% 3 4 5% 4 6% 6% 52%	7605
	11th to 20th	Night	2 3 1 2 2 2 2 2 4 6% 74%	7650
	21st to end	Night	6% 5% 2 4 3 3 4 3 6% 8% 57%	8370
February	1st to 10th	Night	3 5% 2 4 3 2 3 2 3 5% 68%	2730
	11th to 20th	Night	6% 6% 2 4 3 3 3 3 5% 7% 58%	2458
	21st to end	Night	4 4 1 4 2 2 3 2 3 5% 68%	2076
March	1st to 10th	Night	5% 5% 1 4 3 3 4 3 4 5% 65%	5105
	11th to 20th	Night	9% 6% 2 5% 3 3 3 3 4 5% 56%	5110
	21st to end	Night	3 3 1 4 3 3 4 3 5% 6% 64%	5500
April	1st to 10th	Night	4 3 2 4 3 2 3 3 5% 6% 65%	2100
	11th to 20th	Night	5% 3 1 4 4 3 3 4 4 6% 64%	2077
	21st to end	Night	5% 3 1 3 3 2 3 3 4 6% 66%	2100
May	1st to 10th	Night	8% 5% 2 6% 4 4 4 4 5% 6% 54%	5890
	11th to 20th	Night	4 3 1 4 3 3 3 3 4 6% 64%	5583
	21st to end	Night	4 3 1 4 3 3 4 4 5% 6% 63%	5478
June	1st to 10th	Night	4 3 1 5% 4 5% 5% 4 6% 8% 55%	1680
	11th to 20th	Night	3 2 1 4 2 3 3 4 6% 7% 66%	1680
	21st to end	Night	4 4 2 6% 4 5% 5% 5% 7% 9% 49%	1680
July	1st to 10th	Night	2 3 2 6% 5% 5% 6% 5% 7% 8% 52%	5332
	11th to 20th	Night	3 3 2 6% 5% 7% 7% 6% 9% 13% 39%	5340
	21st to end	Night	4 4 2 8% 7% 8% 8% 7% 11% 12% 30%	5805
August	1st to 10th	Night	2 3 2 7% 6% 7% 7% 6% 9% 12% 40%	5398
	11th to 20th	Night	3 3 2 7% 6% 7% 7% 7% 10% 13% 34%	5853
	21st to end	Night	3 4 2 8% 7% 8% 9% 7% 11% 13% 28%	6465
September	1st to 10th	Night	4 4 1 5% 6% 4 5% 4 6% 10% 49%	2100
	11th to 20th	Night	5% 4 2 4 4 4 4 4 6% 8% 55%	2100
	21st to end	Night	5% 3 1 4 3 3 3 3 4 6% 66%	2337
October	1st to 10th	Night	3 2 1 2 2 2 2 2 4 5% 74%	3920
	11th to 20th	Night	5% 3 2 5% 3 4 3 3 4 5% 63%	3898
	21st to end	Night	2 2 1 2 2 1 2 2 3 6% 78%	4252
November	1st to 10th	Night	3 2 1 2 2 2 2 2 4 5% 76%	2460
	11th to 20th	Night	2 3 1 3 2 2 2 3 4 5% 74%	2669
	21st to end	Night	6% 4 2 3 3 2 3 2 4 5% 65%	2730
December	1st to 10th	Night	3 2 1 2 2 2 3 2 5% 7% 72%	4669
	11th to 20th	Night	2 2 1 3 2 3 3 2 5% 9% 67%	5321
	21st to end	Night	4 4 1 3 3 3 3 3 4 6% 67%	6972

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	24% 4 11% 33% 26% 3	5321
	11th to 20th	Day	11% 4 9% 26% 36% 14%	5340
	21st to end	Day	23% 4 6% 19% 35% 13%	5844
February	1st to 10th	Day	20% 3 8% 24% 30% 15%	1890
	11th to 20th	Day	22% 4 9% 24% 29% 12%	2057
	21st to end	Day	18% 3 6% 18% 32% 24%	1730
March	1st to 10th	Day	16% 3 6% 12% 33% 30%	4990
	11th to 20th	Day	19% 7% 8% 19% 27% 20%	5110
	21st to end	Day	19% 2 8% 18% 38% 14%	5710
April	1st to 10th	Day	17% 3 7% 14% 35% 23%	2520
	11th to 20th	Day	18% 3 7% 14% 29% 29%	2494
	21st to end	Day	14% 3 7% 16% 36% 24%	2520
May	1st to 10th	Day	16% 5% 10% 18% 28% 24%	7057
	11th to 20th	Day	13% 3 7% 12% 30% 36%	7307
	21st to end	Day	10% 3 6% 13% 20% 48%	8725
June	1st to 10th	Day	15% 4 10% 17% 25% 29%	2940
	11th to 20th	Day	12% 3 6% 10% 21% 48%	2940
	21st to end	Day	21% 4 11% 16% 21% 29%	2939
July	1st to 10th	Day	15% 6% 9% 13% 21% 37%	7586
	11th to 20th	Day	13% 8% 20% 30% 20% 8%	7581
	21st to end	Day	22% 9% 18% 31% 16% 4	8120
August	1st to 10th	Day	13% 8% 14% 30% 26% 10%	5872
	11th to 20th	Day	15% 7% 14% 27% 25% 12%	5519
	21st to end	Day	22% 9% 17% 28% 21% 4	6078
September	1st to 10th	Day	23% 7% 11% 21% 24% 14%	2520
	11th to 20th	Day	20% 7% 10% 17% 26% 20%	2520
	21st to end	Day	16% 4 7% 20% 30% 23%	2233
October	1st to 10th	Day	12% 3 6% 13% 29% 36%	3270
	11th to 20th	Day	13% 4 6% 16% 35% 26%	3250
	21st to end	Day	9% 2 4 20% 40% 25%	3548
November	1st to 10th	Day	12% 3 6% 21% 41% 18%	2059
	11th to 20th	Day	15% 3 6% 23% 40% 13%	1927
	21st to end	Day	21% 4 5% 24% 33% 13%	1890
December	1st to 10th	Day	13% 4 6% 32% 32% 13%	2738
	11th to 20th	Day	19% 4 7% 34% 31% 5%	3104
	21st to end	Day	17% 3 11% 27% 32% 10%	4277
January	1st to 10th	Night	29% 5% 10% 28% 25% 4	7605
	11th to 20th	Night	12% 3 8% 25% 41% 11%	7650
	21st to end	Night	24% 4 6% 18% 33% 14%	8370
February	1st to 10th	Night	19% 3 10% 20% 32% 15%	2730
	11th to 20th	Night	25% 4 8% 21% 27% 14%	2458
	21st to end	Night	19% 3 4 16% 34% 23%	2076
March	1st to 10th	Night	20% 3 6% 11% 34% 27%	5105
	11th to 20th	Night	25% 6% 7% 17% 28% 17%	5110
	21st to end	Night	19% 3 10% 16% 36% 16%	5500
April	1st to 10th	Night	19% 3 6% 13% 34% 25%	2100
	11th to 20th	Night	21% 3 7% 13% 24% 32%	2077
	21st to end	Night	18% 4 9% 12% 32% 25%	2100
May	1st to 10th	Night	27% 5% 11% 14% 22% 21%	5888
	11th to 20th	Night	18% 4 8% 12% 26% 32%	5584
	21st to end	Night	17% 5% 7% 10% 13% 47%	5479
June	1st to 10th	Night	24% 5% 11% 14% 18% 27%	1680
	11th to 20th	Night	15% 3 8% 12% 19% 43%	1680
	21st to end	Night	28% 7% 12% 13% 14% 27%	1680
July	1st to 10th	Night	25% 8% 12% 14% 12% 28%	5287
	11th to 20th	Night	29% 10% 23% 21% 11% 5%	5286
	21st to end	Night	37% 13% 18% 22% 9% 2	5677
August	1st to 10th	Night	30% 12% 16% 24% 13% 6%	4271
	11th to 20th	Night	32% 11% 16% 18% 12% 10%	4613
	21st to end	Night	36% 13% 19% 19% 9% 4	5069
September	1st to 10th	Night	27% 8% 13% 19% 19% 13%	2100
	11th to 20th	Night	25% 6% 13% 15% 20% 21%	2100
	21st to end	Night	21% 4 7% 14% 29% 25%	2337
October	1st to 10th	Night	14% 3 6% 11% 28% 37%	3920
	11th to 20th	Night	22% 5% 6% 13% 25% 30%	3898
	21st to end	Night	10% 2 4 19% 40% 25%	4252
November	1st to 10th	Night	12% 2 5% 19% 42% 19%	2460
	11th to 20th	Night	14% 3 5% 19% 39% 20%	2669
	21st to end	Night	22% 3 6% 19% 34% 16%	2730
December	1st to 10th	Night	14% 3 7% 31% 32% 13%	4669
	11th to 20th	Night	16% 3 7% 31% 36% 8%	5322
	21st to end	Night	18% 3 8% 30% 32% 9%	6972

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	5% 7% 23% 46% 17% 1	330
	11th to 20th	Day	10% 6% 22% 37% 20% 5%	330
	21st to end	Day	3 7% 25% 41% 21% 3	363
February	1st to 10th	Day	3 10% 29% 35% 21% 3	330
	11th to 20th	Day	10% 11% 27% 44% 9%	330
	21st to end	Day	8% 13% 30% 34% 13% 2	273
March	1st to 10th	Day	6% 17% 33% 28% 14% 2	503
	11th to 20th	Day	10% 18% 27% 28% 15% 2	540
	21st to end	Day	8% 22% 31% 23% 14% 2	594
April	1st to 10th	Day	8% 17% 31% 26% 14% 4	540
	11th to 20th	Day	8% 21% 32% 27% 10% 2	532
	21st to end	Day	9% 16% 32% 29% 12% 3	540
May	1st to 10th	Day	4 14% 34% 28% 16% 3	543
	11th to 20th	Day	4 12% 29% 29% 18% 7%	568
	21st to end	Day	4 11% 26% 34% 21% 4	737
June	1st to 10th	Day	2 5% 19% 36% 31% 8%	780
	11th to 20th	Day	2 5% 17% 35% 33% 7%	780
	21st to end	Day	3 4 16% 34% 35% 8%	779
July	1st to 10th	Day	1 2 12% 30% 36% 20%	566
	11th to 20th	Day	3 1 5% 19% 38% 35%	564
	21st to end	Day	3 1 4 21% 37% 34%	619
August	1st to 10th	Day	2 1 6% 22% 42% 26%	567
	11th to 20th	Day	3 1 6% 24% 41% 24%	557
	21st to end	Day	4 1 6% 26% 41% 23%	627
September	1st to 10th	Day	5% 1 11% 26% 39% 18%	570
	11th to 20th	Day	4 2 15% 34% 35% 9%	570
	21st to end	Day	4 6% 14% 29% 34% 13%	412
October	1st to 10th	Day	5% 4 18% 28% 31% 15%	330
	11th to 20th	Day	7% 8% 15% 31% 28% 11%	330
	21st to end	Day	6% 7% 14% 30% 33% 10%	363
November	1st to 10th	Day	6% 7% 20% 35% 27% 4	330
	11th to 20th	Day	3 5% 15% 41% 28% 8%	330
	21st to end	Day	7% 9% 24% 35% 19% 5%	330
December	1st to 10th	Day	6% 5% 25% 39% 19% 5%	330
	11th to 20th	Day	3 6% 27% 38% 20% 6%	330
	21st to end	Day	12% 7% 23% 40% 15% 3	363
January	1st to 10th	Night	6% 3 28% 47% 15% 1	840
	11th to 20th	Night	7% 4 30% 44% 14% 1	840
	21st to end	Night	7% 5% 30% 41% 15% 1	924
February	1st to 10th	Night	5% 6% 32% 42% 14% 1	840
	11th to 20th	Night	8% 8% 35% 42% 7%	824
	21st to end	Night	6% 9% 41% 40% 5%	692
March	1st to 10th	Night	6% 8% 36% 40% 10%	840
	11th to 20th	Night	7% 10% 31% 40% 12%	840
	21st to end	Night	5% 12% 32% 42% 10%	878
April	1st to 10th	Night	5% 10% 40% 37% 7%	630
	11th to 20th	Night	5% 13% 37% 37% 8%	623
	21st to end	Night	6% 12% 37% 39% 6%	630
May	1st to 10th	Night	6% 7% 36% 43% 9%	630
	11th to 20th	Night	6% 7% 31% 39% 16% 1	621
	21st to end	Night	4 6% 31% 46% 12%	683
June	1st to 10th	Night	3 4 23% 52% 17%	630
	11th to 20th	Night	3 3 25% 49% 20%	630
	21st to end	Night	4 3 19% 47% 26% 1	630
July	1st to 10th	Night	3 1 13% 44% 36% 2	615
	11th to 20th	Night	3 1 7% 36% 50% 3	612
	21st to end	Night	4 1 7% 31% 51% 6%	690
August	1st to 10th	Night	3 1 5% 33% 51% 6%	627
	11th to 20th	Night	4 1 8% 41% 43% 4	624
	21st to end	Night	3 7% 37% 50% 4	693
September	1st to 10th	Night	6% 10% 46% 36% 2	630
	11th to 20th	Night	6% 2 13% 47% 31% 2	630
	21st to end	Night	5% 2 16% 45% 31% 1	732
October	1st to 10th	Night	6% 3 21% 47% 23% 2	800
	11th to 20th	Night	4 6% 19% 52% 18% 2	800
	21st to end	Night	5% 4 22% 43% 24% 3	880
November	1st to 10th	Night	3 3 21% 50% 22% 1	820
	11th to 20th	Night	3 4 25% 47% 21% 2	989
	21st to end	Night	8% 7% 23% 39% 21% 1	1050
December	1st to 10th	Night	7% 4 26% 46% 16% 1	1050
	11th to 20th	Night	6% 6% 26% 46% 16% 1	1050
	21st to end	Night	8% 5% 27% 49% 10%	1090

Page generated at 2026-09-26 02:18:44. Version ac07

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