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 2025-05-11.

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	6% 7% 3 7% 5% 4 4 4 5% 7% 47%	117846
	Night	6% 8% 3 8% 5% 5% 5% 4 6% 7% 44%	119910
Transparency	Day	35% 6% 11% 21% 18% 9%	117589
	Night	38% 7% 13% 22% 15% 5%	119756
Seeing	Day	11% 13% 24% 28% 19% 6%	15137
	Night	10% 8% 20% 38% 22% 3	24322

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	11% 14% 6% 15% 9% 9% 7% 6% 7% 7% 11%	3639
	11th to 20th	Day	9% 12% 4 10% 6% 5% 6% 4 4 5% 36%	3640
	21st to end	Day	7% 10% 4 8% 5% 4 5% 5% 7% 8% 36%	4166
February	1st to 10th	Day	9% 14% 3 10% 6% 6% 5% 5% 6% 8% 27%	1800
	11th to 20th	Day	10% 11% 4 10% 6% 5% 5% 4 7% 8% 30%	1775
	21st to end	Day	7% 12% 4 10% 8% 6% 6% 5% 7% 7% 28%	1650
March	1st to 10th	Day	6% 10% 3 10% 6% 6% 5% 6% 8% 9% 31%	4518
	11th to 20th	Day	6% 11% 5% 11% 6% 5% 5% 3 6% 7% 37%	4955
	21st to end	Day	6% 9% 4 11% 8% 7% 7% 6% 8% 9% 25%	5788
April	1st to 10th	Day	9% 12% 3 9% 7% 6% 6% 5% 6% 8% 29%	2400
	11th to 20th	Day	8% 11% 4 8% 6% 5% 5% 4 5% 6% 40%	2369
	21st to end	Day	7% 7% 3 7% 5% 6% 5% 4 7% 7% 42%	2496
May	1st to 10th	Day	9% 7% 2 6% 4 4 4 4 7% 8% 46%	4560
	11th to 20th	Day	5% 4 1 4 3 3 4 3 5% 6% 62%	4380
	21st to end	Day	8% 7% 2 7% 5% 4 4 5% 7% 8% 44%	4813
June	1st to 10th	Day	9% 8% 2 7% 5% 4 5% 4 6% 7% 43%	2660
	11th to 20th	Day	7% 6% 2 5% 4 4 4 4 5% 7% 51%	2660
	21st to end	Day	4 3 2 3 3 3 3 3 4 5% 67%	2660
July	1st to 10th	Day	1 1 1 2 1 1 1 2 2 3 84%	4420
	11th to 20th	Day	2 1 1 2 1 2 2 2 2 4 82%	4420
	21st to end	Day	2 2 1 2 1 2 2 2 3 5% 80%	4790
August	1st to 10th	Day	3 3 1 3 2 2 2 2 3 5% 73%	4312
	11th to 20th	Day	2 2 1 3 3 2 3 2 3 6% 73%	3978
	21st to end	Day	3 3 1 3 2 2 3 2 3 5% 72%	4180
September	1st to 10th	Day	2 2 1 2 2 2 2 2 4 5% 75%	2280
	11th to 20th	Day	4 4 2 4 4 3 4 4 5% 7% 58%	2280
	21st to end	Day	8% 4 1 5% 3 4 3 3 4 6% 57%	2045
October	1st to 10th	Day	5% 5% 2 5% 3 3 3 3 5% 5% 61%	3180
	11th to 20th	Day	5% 4 2 6% 5% 5% 6% 5% 7% 10% 45%	3161
	21st to end	Day	7% 9% 4 9% 5% 6% 6% 4 6% 7% 37%	3228
November	1st to 10th	Day	10% 9% 4 9% 6% 6% 5% 5% 7% 8% 30%	1764
	11th to 20th	Day	9% 11% 4 10% 8% 7% 6% 5% 7% 8% 24%	1627
	21st to end	Day	7% 12% 4 8% 7% 6% 6% 5% 6% 10% 30%	1600
December	1st to 10th	Day	6% 7% 4 7% 5% 5% 4 4 5% 7% 46%	2620
	11th to 20th	Day	8% 14% 7% 15% 9% 7% 7% 5% 8% 7% 14%	3028
	21st to end	Day	10% 14% 5% 12% 8% 7% 8% 6% 7% 7% 15%	4004
January	1st to 10th	Night	10% 12% 6% 15% 10% 8% 7% 5% 7% 6% 13%	6306
	11th to 20th	Night	10% 11% 4 8% 5% 4 4 4 4 7% 38%	6320
	21st to end	Night	7% 11% 4 10% 6% 5% 4 3 5% 7% 37%	6793
February	1st to 10th	Night	9% 13% 5% 10% 7% 6% 5% 4 6% 7% 28%	2600
	11th to 20th	Night	8% 11% 4 10% 6% 5% 5% 4 6% 6% 34%	2511
	21st to end	Night	9% 12% 5% 9% 7% 6% 6% 5% 6% 8% 29%	1980
March	1st to 10th	Night	5% 7% 3 8% 5% 6% 7% 5% 8% 9% 35%	5376
	11th to 20th	Night	5% 8% 3 8% 5% 5% 6% 5% 7% 8% 41%	5044
	21st to end	Night	5% 9% 4 11% 8% 8% 8% 6% 9% 10% 24%	5187
April	1st to 10th	Night	9% 10% 3 9% 6% 5% 5% 4 6% 9% 34%	2000
	11th to 20th	Night	6% 9% 4 7% 6% 3 5% 4 6% 7% 42%	1979
	21st to end	Night	6% 8% 3 6% 5% 5% 5% 5% 6% 7% 43%	1900
May	1st to 10th	Night	9% 8% 3 6% 4 3 3 3 5% 5% 51%	2620
	11th to 20th	Night	5% 3 1 3 2 2 3 3 4 6% 67%	2519
	21st to end	Night	5% 6% 2 6% 4 3 5% 3 6% 8% 52%	2762
June	1st to 10th	Night	9% 7% 3 6% 4 4 3 4 6% 7% 47%	1520
	11th to 20th	Night	6% 5% 2 5% 3 4 4 4 6% 7% 55%	1520
	21st to end	Night	5% 4 1 3 2 2 3 2 4 5% 68%	1520
July	1st to 10th	Night	1 1 1 1 1 2 1 2 3 86%	2540
	11th to 20th	Night	1 1 2 2 2 2 2 2 4 81%	2540
	21st to end	Night	1 1 2 2 1 1 2 3 4 82%	2761
August	1st to 10th	Night	2 2 1 3 2 3 3 2 5% 5% 71%	2617
	11th to 20th	Night	2 1 1 2 2 3 3 3 4 6% 74%	2862
	21st to end	Night	2 2 1 3 2 2 3 2 4 5% 75%	3498
September	1st to 10th	Night	2 2 1 2 1 1 2 2 3 5% 77%	1900
	11th to 20th	Night	4 3 1 4 3 4 5% 3 5% 7% 62%	1900
	21st to end	Night	6% 4 2 4 3 3 3 3 5% 7% 60%	2132
October	1st to 10th	Night	4 4 2 5% 3 2 3 2 3 5% 67%	3800
	11th to 20th	Night	5% 5% 2 6% 5% 4 5% 4 7% 9% 47%	3777
	21st to end	Night	6% 6% 3 8% 6% 6% 6% 5% 7% 8% 40%	4333
November	1st to 10th	Night	10% 10% 4 9% 6% 6% 5% 4 6% 7% 33%	2535
	11th to 20th	Night	10% 10% 4 11% 6% 6% 6% 6% 7% 8% 27%	2770
	21st to end	Night	7% 10% 4 8% 6% 6% 5% 4 7% 8% 36%	2800
December	1st to 10th	Night	6% 7% 3 6% 5% 4 4 4 5% 7% 49%	4560
	11th to 20th	Night	9% 16% 6% 14% 8% 6% 7% 6% 6% 6% 15%	5176
	21st to end	Night	11% 13% 4 12% 8% 6% 6% 4 6% 8% 21%	6952

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% 10% 13% 8% 2	3639
	11th to 20th	Day	51% 6% 11% 20% 11% 1	3640
	21st to end	Day	43% 10% 12% 16% 14% 5%	4166
February	1st to 10th	Day	53% 10% 14% 17% 7% 1	1800
	11th to 20th	Day	51% 7% 15% 18% 8% 1	1784
	21st to end	Day	51% 10% 16% 14% 8% 1	1650
March	1st to 10th	Day	45% 5% 12% 22% 14% 2	4518
	11th to 20th	Day	45% 6% 12% 25% 11%	4955
	21st to end	Day	50% 10% 16% 18% 6%	5788
April	1st to 10th	Day	50% 8% 13% 19% 10%	2400
	11th to 20th	Day	44% 6% 14% 19% 15% 3	2372
	21st to end	Day	37% 7% 14% 27% 12% 2	2496
May	1st to 10th	Day	34% 6% 13% 28% 19% 1	4560
	11th to 20th	Day	23% 4 10% 30% 30% 3	4383
	21st to end	Day	36% 7% 19% 27% 11% 1	4814
June	1st to 10th	Day	40% 6% 10% 27% 14% 3	2660
	11th to 20th	Day	31% 6% 11% 30% 19% 3	2660
	21st to end	Day	19% 4 10% 31% 27% 9%	2660
July	1st to 10th	Day	8% 1 5% 13% 24% 50%	4351
	11th to 20th	Day	9% 2 5% 7% 23% 54%	4345
	21st to end	Day	10% 2 6% 16% 36% 31%	4639
August	1st to 10th	Day	16% 2 5% 13% 38% 26%	4296
	11th to 20th	Day	14% 2 6% 33% 31% 14%	4017
	21st to end	Day	16% 3 7% 29% 28% 18%	4179
September	1st to 10th	Day	13% 3 8% 26% 31% 19%	2280
	11th to 20th	Day	25% 5% 10% 24% 24% 11%	2280
	21st to end	Day	28% 5% 12% 26% 22% 8%	2045
October	1st to 10th	Day	25% 4 9% 23% 30% 9%	3180
	11th to 20th	Day	31% 7% 18% 25% 17% 2	3161
	21st to end	Day	42% 7% 10% 26% 14% 2	3228
November	1st to 10th	Day	47% 9% 12% 22% 9% 1	1764
	11th to 20th	Day	54% 11% 16% 14% 6%	1627
	21st to end	Day	47% 11% 15% 18% 9% 1	1600
December	1st to 10th	Day	36% 7% 12% 25% 19% 1	2620
	11th to 20th	Day	63% 10% 15% 11% 1	3028
	21st to end	Day	61% 11% 13% 11% 3	4004
January	1st to 10th	Night	66% 11% 12% 9% 2	6306
	11th to 20th	Night	47% 7% 10% 24% 11% 1	6320
	21st to end	Night	46% 9% 10% 15% 15% 5%	6793
February	1st to 10th	Night	52% 9% 18% 15% 6%	2600
	11th to 20th	Night	47% 9% 15% 20% 8% 1	2513
	21st to end	Night	50% 10% 14% 16% 9% 1	1980
March	1st to 10th	Night	40% 7% 12% 25% 14% 2	5376
	11th to 20th	Night	37% 7% 18% 27% 11%	5044
	21st to end	Night	49% 14% 17% 17% 3	5187
April	1st to 10th	Night	45% 9% 16% 21% 8% 1	2000
	11th to 20th	Night	40% 7% 18% 22% 11% 2	1979
	21st to end	Night	37% 9% 15% 25% 12% 2	1900
May	1st to 10th	Night	34% 6% 14% 29% 18%	2620
	11th to 20th	Night	20% 5% 10% 39% 25% 1	2519
	21st to end	Night	29% 9% 30% 24% 7% 1	2762
June	1st to 10th	Night	35% 10% 12% 28% 14% 2	1520
	11th to 20th	Night	28% 7% 13% 36% 13% 4	1520
	21st to end	Night	19% 3 12% 33% 25% 7%	1520
July	1st to 10th	Night	6% 2 6% 15% 26% 44%	2500
	11th to 20th	Night	10% 2 5% 13% 19% 50%	2492
	21st to end	Night	8% 1 5% 20% 37% 29%	2674
August	1st to 10th	Night	15% 3 6% 16% 38% 23%	2609
	11th to 20th	Night	12% 3 8% 39% 28% 9%	2889
	21st to end	Night	12% 4 12% 29% 28% 16%	3498
September	1st to 10th	Night	11% 3 9% 28% 32% 17%	1900
	11th to 20th	Night	22% 6% 11% 26% 23% 13%	1900
	21st to end	Night	25% 5% 9% 28% 24% 9%	2132
October	1st to 10th	Night	22% 3 10% 25% 35% 5%	3800
	11th to 20th	Night	31% 6% 19% 23% 18% 2	3777
	21st to end	Night	37% 8% 11% 30% 12% 1	4333
November	1st to 10th	Night	48% 7% 12% 21% 10% 1	2535
	11th to 20th	Night	52% 9% 15% 19% 5%	2770
	21st to end	Night	44% 10% 16% 20% 10% 1	2800
December	1st to 10th	Night	33% 7% 11% 30% 19%	4560
	11th to 20th	Night	64% 10% 14% 11% 2	5176
	21st to end	Night	57% 9% 17% 12% 5%	6952

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	26% 9% 24% 25% 12% 6%	200
	11th to 20th	Day	15% 12% 22% 31% 15% 6%	200
	21st to end	Day	11% 13% 25% 27% 18% 6%	291
February	1st to 10th	Day	17% 18% 24% 25% 15% 3	400
	11th to 20th	Day	15% 17% 27% 24% 15% 2	405
	21st to end	Day	16% 17% 24% 27% 14% 2	414
March	1st to 10th	Day	15% 20% 26% 26% 12% 2	500
	11th to 20th	Day	16% 16% 24% 27% 13% 4	500
	21st to end	Day	15% 18% 29% 26% 10% 1	550
April	1st to 10th	Day	17% 17% 23% 26% 12% 4	500
	11th to 20th	Day	14% 16% 32% 21% 12% 5%	492
	21st to end	Day	9% 22% 27% 24% 14% 4	500
May	1st to 10th	Day	11% 15% 27% 26% 16% 5%	503
	11th to 20th	Day	16% 12% 23% 29% 14% 6%	489
	21st to end	Day	13% 11% 19% 30% 19% 7%	529
June	1st to 10th	Day	10% 13% 25% 26% 17% 8%	490
	11th to 20th	Day	11% 19% 25% 27% 14% 4	490
	21st to end	Day	4 10% 22% 35% 21% 7%	490
July	1st to 10th	Day	2 7% 27% 36% 24% 5%	486
	11th to 20th	Day	2 10% 25% 32% 25% 7%	484
	21st to end	Day	2 5% 25% 31% 26% 11%	531
August	1st to 10th	Day	4 6% 25% 29% 24% 13%	487
	11th to 20th	Day	3 5% 18% 30% 27% 17%	477
	21st to end	Day	5% 7% 24% 29% 24% 10%	539
September	1st to 10th	Day	3 6% 22% 28% 27% 13%	490
	11th to 20th	Day	6% 8% 22% 30% 27% 6%	490
	21st to end	Day	11% 10% 16% 31% 26% 7%	490
October	1st to 10th	Day	10% 12% 21% 28% 20% 8%	490
	11th to 20th	Day	9% 14% 19% 26% 25% 7%	490
	21st to end	Day	13% 17% 24% 23% 16% 6%	407
November	1st to 10th	Day	12% 16% 24% 30% 14% 4	300
	11th to 20th	Day	11% 15% 26% 23% 17% 6%	213
	21st to end	Day	16% 12% 22% 25% 21% 5%	200
December	1st to 10th	Day	11% 12% 16% 26% 24% 12%	200
	11th to 20th	Day	18% 10% 27% 34% 9% 3	200
	21st to end	Day	19% 14% 22% 28% 14% 3	220
January	1st to 10th	Night	17% 11% 24% 31% 16% 2	800
	11th to 20th	Night	15% 11% 21% 29% 22% 3	800
	21st to end	Night	15% 9% 17% 37% 20% 2	880
February	1st to 10th	Night	16% 10% 23% 34% 15% 1	800
	11th to 20th	Night	13% 9% 25% 35% 16% 1	784
	21st to end	Night	16% 13% 24% 35% 11% 1	660
March	1st to 10th	Night	12% 10% 25% 38% 14% 1	800
	11th to 20th	Night	11% 10% 21% 40% 17% 2	800
	21st to end	Night	9% 12% 27% 36% 14% 1	880
April	1st to 10th	Night	13% 11% 22% 35% 18% 1	800
	11th to 20th	Night	10% 10% 28% 33% 16% 3	791
	21st to end	Night	9% 10% 24% 38% 17% 2	700
May	1st to 10th	Night	6% 7% 21% 41% 23% 2	400
	11th to 20th	Night	11% 6% 16% 38% 28% 2	375
	21st to end	Night	7% 8% 17% 37% 29% 2	411
June	1st to 10th	Night	11% 4 17% 44% 22% 1	380
	11th to 20th	Night	7% 6% 23% 46% 16% 2	380
	21st to end	Night	8% 3 11% 51% 26% 1	380
July	1st to 10th	Night	3 1 9% 54% 32% 2	370
	11th to 20th	Night	1 1 13% 59% 25% 2	368
	21st to end	Night	1 9% 54% 33% 2	416
August	1st to 10th	Night	2 1 6% 48% 40% 3	427
	11th to 20th	Night	3 1 7% 36% 45% 9%	588
	21st to end	Night	2 3 16% 44% 31% 4	836
September	1st to 10th	Night	2 3 14% 41% 35% 5%	760
	11th to 20th	Night	5% 3 11% 40% 35% 7%	760
	21st to end	Night	8% 4 14% 38% 31% 5%	760
October	1st to 10th	Night	8% 3 16% 42% 27% 4	760
	11th to 20th	Night	7% 7% 19% 37% 26% 5%	760
	21st to end	Night	12% 8% 20% 37% 17% 5%	836
November	1st to 10th	Night	14% 7% 22% 37% 18% 1	780
	11th to 20th	Night	15% 13% 22% 33% 16% 2	800
	21st to end	Night	12% 9% 20% 36% 20% 4	800
December	1st to 10th	Night	15% 7% 19% 36% 20% 4	800
	11th to 20th	Night	16% 12% 21% 36% 15% 1	800
	21st to end	Night	18% 13% 27% 31% 10% 1	880

Page generated at 2025-05-08 06:33:56. Version ac07

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