Antelope
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Antelope clear sky chart from 2005-11-06 to 2026-09-14.

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	5% 6% 2 6% 4 4 4 4 5% 7% 52%	158416
	Night	6% 7% 3 7% 5% 4 5% 4 6% 7% 47%	150045
Transparency	Day	31% 5% 11% 22% 21% 10%	153178
	Night	35% 7% 12% 23% 17% 6%	146284
Seeing	Day	10% 13% 24% 28% 18% 6%	16906
	Night	10% 8% 20% 38% 21% 3	25880

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	9% 13% 5% 14% 9% 9% 7% 6% 7% 7% 13%	4722
	11th to 20th	Day	7% 9% 3 8% 5% 4 5% 4 4 6% 46%	4740
	21st to end	Day	6% 8% 4 10% 6% 5% 6% 5% 7% 9% 33%	5404
February	1st to 10th	Day	9% 14% 3 10% 6% 6% 5% 5% 6% 9% 28%	1890
	11th to 20th	Day	10% 11% 4 11% 7% 5% 5% 4 7% 8% 30%	1866
	21st to end	Day	8% 12% 4 9% 7% 6% 6% 5% 7% 7% 28%	1730
March	1st to 10th	Day	6% 10% 3 10% 6% 6% 5% 5% 8% 9% 31%	4618
	11th to 20th	Day	6% 10% 5% 11% 6% 5% 5% 3 6% 7% 37%	5064
	21st to end	Day	6% 9% 4 11% 8% 7% 7% 6% 8% 9% 25%	5916
April	1st to 10th	Day	9% 12% 3 8% 6% 6% 6% 5% 7% 8% 30%	2520
	11th to 20th	Day	8% 10% 4 8% 6% 5% 5% 4 5% 6% 39%	2489
	21st to end	Day	7% 7% 3 7% 5% 6% 5% 4 7% 7% 43%	2620
May	1st to 10th	Day	6% 5% 2 4 3 4 4 4 6% 7% 55%	8195
	11th to 20th	Day	5% 4 2 6% 4 5% 5% 4 6% 8% 52%	8160
	21st to end	Day	6% 5% 2 5% 4 4 4 4 6% 8% 52%	8992
June	1st to 10th	Day	9% 7% 2 7% 5% 4 5% 4 6% 6% 45%	2940
	11th to 20th	Day	7% 6% 2 5% 4 4 4 4 5% 7% 53%	2940
	21st to end	Day	4 3 2 3 3 3 3 3 5% 5% 66%	2940
July	1st to 10th	Day	2 1 1 2 1 1 2 2 3 4 80%	8219
	11th to 20th	Day	2 2 1 2 2 2 2 2 2 4 80%	8220
	21st to end	Day	2 2 1 2 1 2 2 2 3 4 80%	8922
August	1st to 10th	Day	2 2 1 2 2 2 2 2 3 5% 76%	7946
	11th to 20th	Day	2 1 1 3 2 2 3 2 4 6% 74%	7489
	21st to end	Day	4 4 2 3 2 2 3 2 4 7% 67%	7750
September	1st to 10th	Day	2 3 1 3 2 3 3 2 4 5% 72%	2520
	11th to 20th	Day	4 4 2 5% 4 3 4 4 5% 6% 59%	2437
	21st to end	Day	8% 5% 1 5% 3 3 3 3 4 6% 58%	2153
October	1st to 10th	Day	6% 5% 2 5% 3 3 3 3 5% 5% 61%	3280
	11th to 20th	Day	4 4 2 6% 5% 5% 6% 5% 7% 10% 45%	3261
	21st to end	Day	6% 9% 4 9% 5% 6% 6% 4 6% 7% 37%	3331
November	1st to 10th	Day	10% 9% 4 9% 6% 6% 6% 5% 7% 8% 30%	1854
	11th to 20th	Day	9% 11% 5% 10% 8% 7% 6% 5% 7% 8% 24%	1708
	21st to end	Day	7% 12% 4 8% 6% 6% 5% 5% 6% 10% 30%	1680
December	1st to 10th	Day	6% 7% 4 7% 6% 5% 4 4 5% 7% 44%	2700
	11th to 20th	Day	8% 14% 6% 15% 9% 7% 7% 5% 8% 7% 15%	3108
	21st to end	Day	10% 14% 5% 12% 8% 7% 8% 6% 7% 7% 16%	4092
January	1st to 10th	Night	9% 11% 5% 14% 10% 8% 8% 5% 7% 7% 15%	8172
	11th to 20th	Night	8% 9% 3 7% 4 4 4 3 4 7% 47%	8220
	21st to end	Night	6% 10% 4 11% 6% 5% 5% 4 6% 8% 35%	8784
February	1st to 10th	Night	9% 13% 4 10% 7% 6% 5% 4 7% 7% 29%	2730
	11th to 20th	Night	8% 11% 4 10% 6% 5% 6% 4 6% 7% 34%	2640
	21st to end	Night	9% 12% 4 9% 7% 6% 6% 5% 6% 7% 29%	2076
March	1st to 10th	Night	5% 7% 3 8% 5% 6% 7% 5% 8% 9% 35%	5496
	11th to 20th	Night	5% 8% 3 8% 5% 5% 6% 5% 7% 8% 41%	5155
	21st to end	Night	6% 9% 4 11% 8% 8% 8% 6% 8% 10% 24%	5301
April	1st to 10th	Night	9% 9% 3 8% 6% 5% 5% 5% 6% 9% 35%	2100
	11th to 20th	Night	6% 9% 4 7% 6% 4 5% 4 6% 7% 41%	2079
	21st to end	Night	6% 8% 3 6% 5% 5% 6% 5% 6% 7% 43%	1995
May	1st to 10th	Night	5% 5% 2 4 3 2 3 3 5% 7% 60%	4723
	11th to 20th	Night	5% 4 2 5% 3 3 4 3 5% 8% 58%	4700
	21st to end	Night	7% 5% 2 5% 3 3 3 3 5% 8% 56%	5181
June	1st to 10th	Night	9% 6% 3 5% 4 4 4 4 6% 7% 49%	1680
	11th to 20th	Night	5% 5% 2 5% 4 4 4 4 6% 7% 56%	1680
	21st to end	Night	5% 4 1 3 3 2 3 3 5% 5% 67%	1680
July	1st to 10th	Night	1 1 2 1 2 3 2 3 5% 80%	4740
	11th to 20th	Night	2 2 1 3 2 2 2 2 3 4 77%	4740
	21st to end	Night	2 2 1 2 2 2 2 2 4 5% 78%	5153
August	1st to 10th	Night	2 2 1 3 2 3 2 2 4 7% 72%	4852
	11th to 20th	Night	1 1 1 3 2 3 3 3 4 6% 73%	5370
	21st to end	Night	3 3 1 4 2 3 3 3 3 5% 70%	6499
September	1st to 10th	Night	2 2 1 3 2 2 3 2 4 6% 73%	2100
	11th to 20th	Night	4 3 1 4 3 3 5% 3 5% 7% 62%	2030
	21st to end	Night	6% 3 2 4 3 3 3 3 5% 7% 61%	2244
October	1st to 10th	Night	4 4 2 5% 3 3 3 3 3 5% 66%	3920
	11th to 20th	Night	5% 5% 2 7% 5% 4 5% 4 7% 9% 47%	3897
	21st to end	Night	6% 6% 3 8% 6% 6% 6% 5% 7% 8% 40%	4472
November	1st to 10th	Night	10% 10% 4 9% 6% 6% 5% 4 6% 8% 32%	2665
	11th to 20th	Night	10% 10% 4 11% 6% 6% 6% 6% 6% 8% 27%	2909
	21st to end	Night	7% 10% 4 9% 6% 6% 5% 4 7% 8% 35%	2940
December	1st to 10th	Night	6% 7% 2 6% 5% 4 4 4 6% 7% 48%	4700
	11th to 20th	Night	9% 16% 6% 14% 8% 6% 7% 6% 6% 6% 16%	5316
	21st to end	Night	11% 13% 4 12% 8% 6% 7% 5% 6% 8% 21%	7106

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	63% 11% 14% 10% 2	4723
	11th to 20th	Day	41% 5% 9% 20% 21% 4	4740
	21st to end	Day	43% 9% 11% 15% 16% 4	5404
February	1st to 10th	Day	51% 9% 14% 18% 7% 1	1890
	11th to 20th	Day	51% 7% 15% 18% 8% 1	1875
	21st to end	Day	51% 9% 15% 14% 9% 1	1730
March	1st to 10th	Day	45% 6% 12% 22% 14% 2	4618
	11th to 20th	Day	45% 7% 12% 25% 11%	5064
	21st to end	Day	50% 9% 16% 18% 7%	5916
April	1st to 10th	Day	49% 8% 13% 20% 10%	2520
	11th to 20th	Day	44% 6% 14% 19% 14% 3	2492
	21st to end	Day	37% 7% 14% 28% 13% 2	2620
May	1st to 10th	Day	26% 4 10% 29% 27% 3	8195
	11th to 20th	Day	27% 6% 14% 28% 23% 1	8163
	21st to end	Day	28% 6% 17% 30% 18% 2	8994
June	1st to 10th	Day	37% 5% 10% 27% 16% 3	2940
	11th to 20th	Day	30% 5% 11% 29% 21% 5%	2940
	21st to end	Day	20% 4 10% 31% 26% 9%	2940
July	1st to 10th	Day	10% 2 4 18% 34% 33%	8151
	11th to 20th	Day	11% 1 4 9% 29% 45%	8145
	21st to end	Day	10% 1 5% 24% 38% 21%	8723
August	1st to 10th	Day	11% 1 4 11% 36% 37%	6294
	11th to 20th	Day	13% 2 7% 34% 32% 12%	5900
	21st to end	Day	15% 3 6% 31% 32% 14%	6077
September	1st to 10th	Day	15% 3 8% 25% 31% 18%	2520
	11th to 20th	Day	25% 5% 10% 25% 25% 10%	2437
	21st to end	Day	28% 4 11% 25% 23% 8%	2153
October	1st to 10th	Day	25% 4 9% 23% 29% 9%	3280
	11th to 20th	Day	31% 7% 18% 25% 17% 2	3261
	21st to end	Day	42% 7% 10% 26% 13% 2	3331
November	1st to 10th	Day	47% 9% 13% 22% 8% 1	1854
	11th to 20th	Day	54% 10% 16% 14% 6%	1708
	21st to end	Day	47% 11% 15% 18% 8% 1	1680
December	1st to 10th	Day	37% 8% 12% 25% 18% 1	2700
	11th to 20th	Day	62% 9% 15% 12% 2	3108
	21st to end	Day	60% 11% 13% 12% 3	4092
January	1st to 10th	Night	61% 12% 13% 12% 2	8172
	11th to 20th	Night	38% 6% 9% 22% 21% 4	8220
	21st to end	Night	47% 8% 10% 15% 17% 4	8784
February	1st to 10th	Night	51% 8% 18% 16% 6%	2730
	11th to 20th	Night	47% 8% 15% 20% 8% 1	2642
	21st to end	Night	50% 9% 14% 16% 10% 2	2076
March	1st to 10th	Night	40% 7% 12% 25% 14% 2	5496
	11th to 20th	Night	37% 7% 18% 27% 11%	5155
	21st to end	Night	49% 14% 17% 17% 4	5301
April	1st to 10th	Night	44% 9% 16% 23% 8% 1	2100
	11th to 20th	Night	40% 8% 17% 22% 11% 2	2079
	21st to end	Night	36% 9% 15% 25% 12% 2	1995
May	1st to 10th	Night	24% 5% 11% 32% 28% 1	4721
	11th to 20th	Night	23% 7% 16% 35% 19% 1	4700
	21st to end	Night	26% 6% 23% 29% 15% 1	5182
June	1st to 10th	Night	33% 9% 12% 28% 16% 2	1680
	11th to 20th	Night	27% 7% 12% 34% 16% 4	1680
	21st to end	Night	20% 4 12% 33% 25% 7%	1680
July	1st to 10th	Night	9% 2 6% 27% 28% 28%	4700
	11th to 20th	Night	13% 2 5% 11% 28% 40%	4692
	21st to end	Night	10% 2 4 31% 36% 16%	5040
August	1st to 10th	Night	11% 2 4 12% 39% 32%	3834
	11th to 20th	Night	12% 3 9% 34% 33% 8%	4234
	21st to end	Night	14% 3 9% 32% 31% 12%	5092
September	1st to 10th	Night	14% 3 9% 27% 31% 16%	2100
	11th to 20th	Night	22% 6% 10% 26% 23% 12%	2030
	21st to end	Night	24% 5% 9% 28% 25% 9%	2244
October	1st to 10th	Night	22% 4 10% 25% 34% 4	3920
	11th to 20th	Night	31% 6% 19% 24% 18% 2	3897
	21st to end	Night	37% 8% 11% 30% 13% 1	4472
November	1st to 10th	Night	48% 7% 13% 21% 9% 1	2665
	11th to 20th	Night	52% 9% 15% 19% 5%	2909
	21st to end	Night	44% 9% 16% 20% 9% 1	2940
December	1st to 10th	Night	33% 8% 12% 29% 18%	4700
	11th to 20th	Night	63% 9% 14% 11% 3	5316
	21st to end	Night	57% 9% 17% 12% 5%	7106

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	25% 10% 25% 24% 11% 5%	220
	11th to 20th	Day	14% 11% 21% 31% 16% 7%	220
	21st to end	Day	10% 12% 26% 28% 18% 6%	317
February	1st to 10th	Day	17% 17% 23% 25% 15% 3	430
	11th to 20th	Day	15% 16% 27% 25% 15% 2	436
	21st to end	Day	17% 16% 26% 26% 13% 2	446
March	1st to 10th	Day	15% 21% 26% 25% 12% 1	540
	11th to 20th	Day	18% 17% 24% 25% 12% 4	540
	21st to end	Day	16% 18% 30% 26% 10% 1	594
April	1st to 10th	Day	17% 16% 23% 25% 13% 5%	540
	11th to 20th	Day	15% 16% 31% 23% 11% 5%	532
	21st to end	Day	9% 21% 27% 25% 14% 4	540
May	1st to 10th	Day	10% 15% 27% 27% 17% 5%	543
	11th to 20th	Day	17% 14% 24% 27% 13% 5%	568
	21st to end	Day	12% 11% 21% 30% 19% 7%	617
June	1st to 10th	Day	10% 14% 25% 27% 17% 8%	570
	11th to 20th	Day	10% 17% 25% 28% 16% 4	570
	21st to end	Day	4 11% 23% 34% 21% 7%	570
July	1st to 10th	Day	2 7% 25% 35% 25% 6%	566
	11th to 20th	Day	3 10% 24% 33% 23% 7%	564
	21st to end	Day	2 5% 25% 30% 27% 11%	619
August	1st to 10th	Day	3 6% 24% 30% 25% 13%	567
	11th to 20th	Day	3 5% 18% 31% 27% 16%	557
	21st to end	Day	5% 7% 24% 29% 24% 10%	627
September	1st to 10th	Day	4 6% 22% 29% 27% 12%	570
	11th to 20th	Day	6% 8% 22% 31% 26% 7%	543
	21st to end	Day	11% 10% 16% 30% 25% 8%	530
October	1st to 10th	Day	11% 11% 21% 28% 20% 8%	530
	11th to 20th	Day	10% 15% 20% 26% 23% 7%	530
	21st to end	Day	13% 16% 24% 24% 17% 6%	444
November	1st to 10th	Day	12% 15% 26% 28% 14% 4	330
	11th to 20th	Day	10% 16% 26% 24% 17% 6%	234
	21st to end	Day	15% 12% 23% 26% 20% 5%	220
December	1st to 10th	Day	14% 12% 17% 24% 22% 11%	220
	11th to 20th	Day	20% 11% 26% 32% 8% 3	220
	21st to end	Day	18% 15% 22% 26% 14% 4	242
January	1st to 10th	Night	16% 11% 24% 31% 15% 2	840
	11th to 20th	Night	14% 10% 20% 30% 23% 3	840
	21st to end	Night	14% 8% 17% 38% 20% 2	924
February	1st to 10th	Night	16% 10% 23% 35% 16% 1	840
	11th to 20th	Night	13% 9% 25% 35% 16% 1	824
	21st to end	Night	16% 13% 25% 34% 11% 1	692
March	1st to 10th	Night	12% 11% 26% 37% 13% 1	840
	11th to 20th	Night	11% 11% 22% 39% 16% 2	840
	21st to end	Night	9% 13% 27% 36% 14% 1	924
April	1st to 10th	Night	12% 11% 22% 35% 19% 1	840
	11th to 20th	Night	10% 10% 28% 34% 16% 3	831
	21st to end	Night	9% 10% 25% 38% 17% 2	735
May	1st to 10th	Night	6% 7% 21% 42% 23% 2	420
	11th to 20th	Night	11% 7% 18% 37% 26% 1	414
	21st to end	Night	7% 8% 16% 39% 28% 2	455
June	1st to 10th	Night	11% 4 18% 43% 23% 2	420
	11th to 20th	Night	6% 6% 24% 47% 16% 2	420
	21st to end	Night	8% 3 12% 51% 25% 1	420
July	1st to 10th	Night	2 1 9% 54% 33% 1	410
	11th to 20th	Night	1 1 14% 58% 24% 2	408
	21st to end	Night	1 10% 54% 33% 2	460
August	1st to 10th	Night	2 1 7% 49% 38% 3	473
	11th to 20th	Night	3 1 7% 38% 44% 8%	650
	21st to end	Night	2 4 16% 44% 31% 3	924
September	1st to 10th	Night	3 3 15% 41% 34% 4	840
	11th to 20th	Night	5% 4 11% 40% 34% 6%	812
	21st to end	Night	8% 4 14% 38% 31% 5%	800
October	1st to 10th	Night	8% 3 17% 42% 26% 4	800
	11th to 20th	Night	8% 7% 20% 37% 25% 4	800
	21st to end	Night	12% 8% 20% 38% 17% 5%	880
November	1st to 10th	Night	14% 8% 23% 36% 18% 1	820
	11th to 20th	Night	15% 13% 22% 33% 16% 1	840
	21st to end	Night	12% 10% 20% 36% 19% 4	840
December	1st to 10th	Night	15% 8% 19% 35% 19% 4	840
	11th to 20th	Night	16% 12% 21% 36% 14% 1	840
	21st to end	Night	18% 13% 27% 31% 11% 1	924

Page generated at 2026-09-11 01:11:52. Version ac07

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